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StressCheck

GETTING STARTED GUIDE

Release 10.3March, 2017

For Windows Operating Systems

Copyright 2017

Engineering Software Research & Development, Inc.

COPYRIGHT NOTICE

Copyright 2017 by Engineering Software Research & Development, Inc. All rightsreserved, worldwide. No part of this manual may be reproduced, transmitted, tran-scribed, stored in a retrieval system, or translated into any human or computer lan-guage, in any form or by any means, electronic, mechanical, magnetic, optical,chemical, manual, or otherwise, without the expressed written permission from Engi-neering Software Research & Development, Inc., 111 Westport Plaza, Suite 825, St.Louis, MO 63146, U.S.A.

StressCheck includes portions of FLEXnet license manager version 11.5 Copyright ©2009 Acresso Software Inc.

Tech Soft America (www.hoops3d.com) supplied the following core technology:

HOOPS 3D Application Framework© 2015

HOOPS 3D Graphics System© 2015

StressCheck incorporates Parasolid®, a product of Siemens Product Lifecycle Man-agement Software Inc.

StressCheck incorporates MeshSim(TM) a product of Simmetrix Inc.

StressCheck incorporates PAM(TM) a product of Applied Design Analysis Corp.(ADA). Copyright 2002. All Rights reserved.

StressCheck incorporates InterOp libraries that are a product of Dassault Systèmes.

StressCheck includes Taucs Version 2.0, November 29, 2001. Copyright © 2001,2002, 2003 by Sivan Toledo, Tel-Aviv University, [email protected]. All Rightsreserved.

StressCheck includes CSparse: a Concise Sparse matrix package. Copyright © 2006,Timothy A. Davis. http://www.cise.ufl.edu/research/sparse/CSparse

StressCheck includes METIS. Copyright 1997, Regents of the University of Minne-sota. All rights reserved.

StressCheck incorporates the Intel(R) Math Kernel Library for Windows, 2016 Copy-right Intel Corporation. All rights reserved.

StressCheck incorporates AvalonDock. Copyright © 2007-2013, Adolfo Marinucci.All right reserved. THE SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLD-ERS AND CONTRIBUTORS "AS IS", AND ANY EXPRESS OR IMPLIED WAR-RANTIES, INCLUDING BUT NOT LIMITED TO, THE IMPLIED WARRANTIESOF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AREDISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CON-TRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-CIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING BUTNOT LIMITED TO, PROCUREMENTOF SUBSTITUTE GOODS OR SERVICES;LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTIONS) HOW-EVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CON-TRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGIBLE OROTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

DISCLAIMER

Engineering Software Research & Development, Inc. makes no representations orwarranties with respect to the contents hereof and specifically disclaims any impliedwarranties of merchantability or fitness for any particular purpose. Further, Engineer-ing Software Research & Development, Inc. reserves the right to revise this publica-tion and to make changes from time to time in the content hereof without obligation ofEngineering Software Research & Development, Inc. to notify any person or organi-zation of such revision or change.

Table of Contents

1 Introduction 1

What is StressCheck? 1

Why use StressCheck? 2

Who should use StressCheck? 3

StressCheck features 3

How to use this manual? 3

Frequently asked questions about the p-version and StressCheck 5

2 StressCheck Interface 9

Interface layout 9

Standard file extensions 17

File menu 18

Edit menu 20

Class menu 21

View menu 22

Getting Started Guide Table of Contents i

Table of Contents

Display menu 24

Tools menu 28

General interface conventions 28

3 The Handbook 31

Handbook framework 31

Handbook library 31

Handbook interface 32

Solving a handbook problem 35

Handbook library expansion 42

4 Tutorial 43

Planar elasticity problem 43

Extrusion problem 62

Three-dimensional problem 69

Index 79

ii Table of Contents Getting Started Guide

1

1 Introduction

What is StressCheck?

From the perspective of designers, StressCheck is a very advanced handbook thatprovides reliable solutions quickly and conveniently.

From the perspective of analysts, StressCheck is a tool for advanced problem solv-ing and a framework for communicating the results to designers.

From the perspective of managers, StressCheck is a tool for increased productivityand better design in less time.

StressCheck is the first finite element analysis program to emphasize bothadvanced technological features and ease of use for everyday design and analysisproblems. ESRD founders are pioneers in development of p-version FEA and havebuilt the most advanced features available into StressCheck: advanced representa-tion of surfaces; hierarchic models for structural plates, including plates made oflaminated composites; advanced implementation of superconvergent extractionprocedures for the computation of stress intensity factors in two and three dimen-sions; efficient and reliable treatment of material and geometric nonlinearities inthe context of the p- and hp- versions; multi-body contact including material non-linearities; the option to employ either the trunk space or the product space in p-

Getting Started Guide Chapter 1: Introduction 1

Why use StressCheck?

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extensions, and capabilities related to the analysis of fastened connections,including cold working analysis.
StressCheck improves the reliability of computed information while increasingthe productivity of analysts. Recognizing that the analyst’s time is usefullyspent only if the computed information is sufficiently accurate and reliable toserve the purposes of engineering decision-making, StressCheck was designedso that the reliability of the data of interest can be readily ascertained. For mostanalysis tasks the largest cost component, typically more than 90 percent, is thecost of time spent on data preparation and interpretation of the results. Stress-Check was designed so as to minimize this cost. The user interface wasdesigned to permit quick generation of finite element meshes, entry of materialproperties and boundary conditions.

There is an immediate visual feedback confirming that the data is properlyentered. Modification and editing tasks can be performed quickly and conve-niently. With StressCheck, the desired information, such as displacements,stresses and stress maxima, stress intensity factors, and stress resultants can beconveniently extracted from finite element solutions.

Why use StressCheck?

StressCheck delivers the most advanced p-version stress analysis technology ina convenient, easy to use, handbook style interface. With StressCheck, youovercome both the limitations of engineering handbooks and the complexity ofconventional FEA. StressCheck provides information that enables its users toverify solution quality in a fraction of the time that would be required for con-ventional FEA.

By incorporating your proprietary technology into an everyday handbook styletool for both analysts and design engineers, routine problems can be set up andsolved in minutes. The handbook utility makes it possible for users to definefrequently occurring problems parametrically which can be recalled quicklyand conveniently for analysis, even by non-specialists. Therefore StressCheckprovides solutions which are much more representative of the parts that need tobe analyzed than handbook solutions. The amount of time required for analysisis about the same as for computerized handbooks but the versatility and reli-ability are much greater.

Chapter 1: Introduction Getting Started Guide

Who should use StressCheck?

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StressCheck’s unique handbook capability is combined with an automated paramet-ric analysis capability making it convenient to investigate the sensitivity of a solu-tion to variations in critical design parameters.

StressCheck’s unique and advanced post-processing capability allows detailedevaluation of engineering data anywhere in the model without expensive and timeconsuming re-run of the problem.

Who should use StressCheck?

StressCheck has been developed to facilitate analysis throughout the design pro-cess, making it a valuable tool for both analysts and design engineers. The hand-book utility provides designers with easy access to advanced finite elementtechnology within an easy-to-use intuitive interface. The handbook library can beexpanded by FEA analysts to incorporate commonly encountered parts anddesigns. The problems can then be executed quickly and easily by design engineers.

StressCheck features

StressCheck is based on the p-version of the finite element method: The errors ofapproximation are controlled by increasing the polynomial degree of the elements.The main features of the program are summarized in the table on page 4.

How to use this manual?

For persons experienced in using finite element analysis programs, StressCheck iseasy to learn. For persons who have no experience, or only very limited experiencewith finite element analysis, detailed step-by-step procedures are provided in thismanual. The basic procedures are described and illustrated by examples so as tomake self-instruction possible. The Getting Started Guide was designed to explorethe basics of the user interface, the Handbook framework, model creation, solutionprocedures and post-processing operations.


How to use this manual?

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G

E

M

Model Materials Boundary Conditions

Solution

StressCheck features - Elasticity

Output

eometry:

Parasolid kernel

System

Point

Line

Circle

Fillet

Ellipse

Spline

Cylinder

Cone

Plane

Torus

Formula

Composite

more

lements:

Beam

Fastener

Link

Quadrilateral

Triangular

Hexahedral

Pentahedral

Tetrahedral

Linear:

Isotropic

Orthotropic

Anisotropic

Fitted Fiber

Temperature-dependent

Loads:

Tractions

Point Load

Body Force

Spring Displ.

Bearing

Shear

Moment

Imposed Displ.

Thermal

Formula

Running load importation

TLAP Traction

TLAP Bearing

Nonlinear:

Elastic-Plastic

Bilinear

Ramberg-Osgood

Iso-Exponential

Laminated:

Cartesian (flat)

Cylindrical

General Curvature

Automatic Lam-ination

Constraints:

Rigid Body

Nodal Constr.

Boundary General

Face Constr.

Spring Coeff.

Built-In

Soft-Simple

Symmetry

Antisymmetry

Fastener to Fastener

Hinge

Imported point con-straint

Formula

Point constraint importation

Reference:

Plane-Stress

Plane-Strain

Axisymm.

Plate Bending

Extrusion

3D-Solids

Analyses:

Linear

Nonlinear Material

Nonlinear Geometry

Modal

Prestress Modal

Eigenvalue Buckling

Cold Working

Margin Check

Measurement

Crack Path

Contact

Global-Local

Standard:

Error Estimate

Equilibrium Check

Resultants

Contour Plotting

Deformed Shape

Min/Max Extraction

Point/Line/Edge Extraction

Averages

Animation

eshing:

Manual

2D automesh

3D automesh

Boundary Layer Meshing

Advanced:

2D & 3D Fracture Mechanics

SIF

T-Stress

Separated J-integral


Frequently asked questions about the p-version and StressCheck

1

An overview of the user interface is presented in the second chapter. The thirdchapter provides an introduction to the Handbook framework. The fourth chapterwas written for first time users who are encouraged to follow the example problemsin a step-by-step fashion. This will provide a sense of the “look and feel” of the pro-gram. For specific analysis types and procedures refer to the Analysis Guide andthe Advanced Guide.


In this section some frequently asked questions about the p-version of the finite ele-ment method, which is the technological basis of StressCheck, are answered.

Why is the p-version important?

The finite element method provides an approximate solution. In engineering prac-tice it is important to know not only the information one wishes to compute but alsoto have an indication about the size of the error of approximation. The p-versionmakes it convenient to obtain error estimates in terms of the data of interest veryefficiently. Since the analyst is responsible for the computed information, it isimportant to have tools available which make it possible to exercise that responsi-bility.

When was the p-version developed?

Research on the p-version dates back to the late 1960's. Many important advancesoccurred in the 1970's. The theoretical basis was established in 1981 and optimalmeshing strategies appropriate for the p-version were developed in the period 1984-1985. For details we refer to Szabo and Babuska, Finite Element Analysis, JohnWiley & Sons, Inc. (1991). Beginning in 1985, these developments were madeavailable for use in professional practice. The p-version is a more recent technologythan the h-version, the development of which began in the late 1950's.



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Are error estimation procedures available in h-version codes as well?
Most h-version codes offer some form of adaptive capability. The theory ofadaptive mesh construction was developed in the 1970's by Babuska and Rhe-inboldt. The objective of an h-adaptive process is to obtain a sequence of finiteelement meshes in such a way that the error measured in energy norm is mini-mal, or nearly minimal, for each mesh. Subsequently Zienkiewicz and Zhouproposed an adaptive scheme, variants of which have been implemented in h-version codes. In general, h-version codes do not provide convenient and reli-able means for making an assessment of the quality of computed information,however.

Does the p-version have clear advantages over the h-version?

Yes. For typical design problems in mechanical and civil engineering practicethe errors of approximation are reduced at an exponential rate when the num-ber of degrees of freedom are increased, provided that the finite element meshis properly constructed. The h-version can provide algebraic convergence ratesonly. This makes error control much more effective in the p-version. Further-more, a converging sequence of solutions is much more naturally and conve-niently obtained with the p-version than with the h-version. This makes itfeasible to employ quality control procedures in the setting of practical engi-neering decision-making processes.

Are there significant differences in p-version FEA programs?

Yes. There are several important differences. For example, proper implementa-tion of the p-version requires that the mappings from the standard elements tothe “real” elements must be sufficiently accurate so that the error of approxi-mation is controlled by the mesh and the polynomial degree of elements, notby the mapping procedures. This is because, unlike in the h-version, the meshis not refined as the number of degrees of freedom is increased. Quadratic andcubic polynomial mappings (also known as isoparametric mappings) shouldnot be used in connection with the p-version unless the maximum polynomialorder is restricted to 4 or 5. StressCheck has advanced mapping proceduresimplemented. Many other important differences exist in such areas as enforce-ment of constraints, specification of loading conditions, the availability of non-linear analyses, graphic user interfaces, post-processing operations, etc.



1

Are there areas of application which can be handled by the p-version but not by the h-version or vice versa?

In principle, any problem which can be solved by the h-version can be solved bythe p-version and, conversely, any problem which can be solved by the p-versioncan be solved by the h-version. There are large differences in convergence rates,however. For example, it was demonstrated in one well-documented plane elasticmodel problem that to achieve one percent relative error in energy norm (which issimilar to the root-mean-square measure of error in stress), approximately 1000degrees of freedom were needed with the p-version and properly designed mesh,whereas 10 million degrees of freedom would have been required with the h-ver-sion, utilizing 8-noded quadrilaterals and uniform mesh refinement. For details werefer to p.190 in Szabo and Babuska, Finite Element Analysis (1991). There areother important areas where the p-version has clear and substantial advantages:adhesively bonded joints (where very large aspect ratios are required), structuralplates and shells, fracture mechanics, etc.

What are the advantages of StressCheck over other FEA programs?

There are several important advantages. The most important advantage is thatStressCheck is the only FEA program in existence today which was designed forcontrolling both the errors of discretization and idealization. The errors of discreti-zation are the errors controllable by the finite element mesh and the polynomialdegree (h- or p-extensions). The errors of idealization are the errors associated withthe restrictions incorporated in mathematical model. For example, the basicassumptions of the linear theory of elasticity are that the strains are much smallerthan unity; the stress is proportional to the strain independently of the magnitude ofstrain; the deformed and undeformed configuration of the elastic body are virtuallyidentical, hence the equilibrium equations can be written for the undeformed con-figuration. Inasmuch as these assumptions may not be applicable in particularcases, errors of idealization are incurred. StressCheck was designed so that the lin-ear solution is a potential starting solution for a geometric and/or material nonlinearproblem.

There are many other advantages as well: StressCheck incorporates advanced pro-cedures for the computation of stress intensity factors in linear elastic fracturemechanics; it can compute the natural straining modes and the corresponding gen-eralized stress intensity factors in homogeneous and heterogeneous bodies. Stress-Check is the first FEA program to provide hierarchic models for homogeneous and



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laminated plates. StressCheck provides a number of unique post-processingprocedures as well.
What are the recommended quality control procedures in FEA?

The main idea in quality control procedures is that the exact solution is inde-pendent of the mesh or the polynomial degree. Therefore the data of interestcannot depend on the choice of mesh or polynomial degree. Furthermore, thedata of interest should not be sensitive to the restrictive assumptions incorpo-rated in the mathematical model. The recommended quality control proceduresconsist of the following steps:

a) Linear analysis: Control of the errors of discretization.

• Verify that the error in energy norm (which is related to the RMS mea-sure of error in stress) is reasonably small (under 5 percent for 3D andunder 2 percent for 2D).

• Knowing that the data of interest are finite, show that the data of inter-est are substantially independent of the polynomial degree of elements.

• Show that equilibrium is satisfied.

• Show that there are no significant jumps in the stress contours.

b) Nonlinear analysis: Control of the errors of idealization.

• Show that the data of interest are independent of the restrictiveassumptions incorporated in the linear model. This requires that geo-metric and/or material nonlinear analysis be performed.


2

2 StressCheck Interface

This chapter covers the most relevant features of the user interface. For a complete overview of the userinterface refer to the User’s Guide. The interface layout, standard file extensions, file menu options,interface conventions, and display manipulation sections provide enough information to create the finiteelement model, to compute the solution and to perform an analysis of a model problem.

Interface layout

The StressCheck user interface is designed to simplify data entry and to standardizeprogram operation. As shown in Figure 1, this interface consists of a Main MenuBar and four Toolbars (Main, Attributes, Reference/Theory/Units, and Part/Assem-bly) at the top of the screen, a graphic Model Window in the center, and four Tool-bars (Views, Edit, Display Options, and Display Objects) at the bottom of thescreen. Tabbed dialog windows provide for data entry. When a tabbed dialog win-dow has more tabs than can fit on the screen, a convenient pop-up menu can beactivated by a right mouse button click.

The Main Menu Bar provides access to program options which are used on a rela-tively infrequent basis; such as opening and closing files, changing display attri-butes, selecting an input class, etc. The Views and Main Toolbars provide a shortcutto the most frequently used menu options, such as display manipulation, and access

Getting Started Guide Chapter 2: StressCheck Interface 9

Interface layout

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to the dialog windows. The Reference selector should be used to choosewhether to model a problem as a membrane, as an axisymmetric solid, as aplate in bending, or as a fully three-dimensional solid. The Theory selectorshould be used to indicate whether the problem to be solved is an elasticity or aheat transfer problem. It is now necessary to consider the choice of units ofmeasurement before creating any geometry in StressCheck. In the Units selec-tor combo box, the options are: Other, in/lbf/sec/F, and mm/N/sec/C. TheModel Window is where the finite element model will appear for both pre- andpost-processing. A dialog window is where most text based user interaction

Main Menu Bar

Main Toolbar

Status Line

FIGURE 1 StressCheck screen layout.

Model Window

Tabbed Input Dialog Window

Reference/Theory/Units Selectors

Views Toolbar

Attributes Toolbar

Project Log

Chapter 2: StressCheck Interface Getting Started Guide

Interface layout

2

will occur. There are five primary dialog windows: one for model information, onefor model input, one for solver options, one for model results, and one for interact-ing with the handbook framework.

Most of the tabbed dialog windows are divided into three sections (FIGURE 3). Atthe bottom are 2 or more tabs, which allow the user to select a category of input. Inthe center are the input fields and combo-boxes which relate to the specific cate-gory of input chosen with the tab. At the bottom of each dialog window is a set ofpush-buttons which are used to invoke a command.

Of particular importance is the additional interface control found in the input dialogwindow which contains a summary of the data records corresponding to a particularclass. This listbox gives the user access to data previously entered so that it may bealtered and replaced. For geometry and mesh classes, this listbox can be viewed byselecting the “Index” tab.

Model Info The “Model Information” window can be displayed on the screen by selecting“Model Info” from the Main Menu “Edit” pulldown menu. The model window(FIGURE 2) can also be activated by selecting the icon from the Main Toolbar. The

FIGURE 2 Model Info dialog box.

“Model Info” Icon

Browser icon


Interface layout

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three tabs at the top of the window give the user access to model descriptions,design variable definitions, and design variable rules. The model browser canbe activated from this window by selecting the Browser icon.

Input The “Input” window can be displayed on the screen by selecting “Input” fromthe Main Menu “Edit” pulldown menu, or by selecting an input class such asGeometry, Mesh, Thickness, etc. from the Main Menu “Class” pulldownmenu. Alternatively, the Input dialog window (FIGURE 3) may be activated byselecting the “Create Model” icon from the Main Toolbar.

FIGURE 3 Geometry input dialog window.

Class Tabs

Command Buttons

“Create Model” Icon

Input Fields

Curve/Surface Selector

Surface/Solid Option


Interface layout

2

Solution The “Solution” window can be displayed by selecting “Solution” from the MainMenu “Edit” pulldown menu, or by selecting the “Compute Solution” icon in theMain Toolbar. The Solution dialog window is shown in FIGURE 4 for 3D Elastic-ity. The solution interface contains several tabs, one for each type of solution sup-ported by StressCheck, i.e. Linear, Nonlinear, Modal, Buckling, Measurement, andMargin Check. Once a specific solution type is selected, and the pertinent optionsare chosen, the solution may be performed by choosing the “SOLVE!” tab. This tabcontains the various options that are common to all solution types.

Results The “Results” window can be displayed by selecting “Results” from the MainMenu “Edit” pulldown menu, or by selecting the “View Results” icon in the MainToolbar. The Results dialog window is shown in FIGURE 5. The results interfacecontains several tabs, one for each type of post-processing option supported byStressCheck, i.e. Error Estimation, Points Extraction, Resultant Extraction, etc.

FIGURE 4 Solver interface.

Solver Execution InterfaceSolver Option Interface

“Compute Solution” Icon


Interface layout

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StressCheck provides convenient means for displaying and printing computedinformation in graphical form. For example, to obtain a contour plot ordeformed configuration, you select the Plot tab from the Results window. Byselecting any other tab, a graph window appears. This window will contain theresults of the post-processing computations in both graphical and tabular form.

NOTE: The Graph window is not applicable for the Plot tab.

FIGURE 5 Results interface.

“View Results” Icon

Solution ID Selection

Class Tabs

Computation Options

Command Buttons


Interface layout

2

Handbook The “Handbook Library” window can be displayed by selecting “Handbook” fromthe Main Menu “Edit” pulldown menu, or by selecting the “Handbook Library”icon in the Main Toolbar. The Handbook Library dialog window is shown in FIG-URE 6.

The Handbook Library interface provides access to, and interaction with, pre-defined models of frequently occurring mechanical design components. Its tabsprovide access to different functions of the handbook framework. The “ModelInfo” tab through its Browser Icon gives access to the Model Browser. The ModelBrowser provides a list of the available handbook models from which to choose.Click on the Browser Icon and the Model Browser will be displayed on the screen.The three buttons to the right of the Browser Icon provide access to the Icon win-dow and a capability to capture, edit and save an image of the model. The Icon win-dow provides an illustration for each handbook problem which is useful forassociating the design parameters with the model. The Keywords help to identifythe model during browsing. The Comments are intended to provide specificinstructions to assist in the execution of a handbook model or in the interpretationof results.

The “Analysis” tab gives the user control of model dimensions and other designproperties, and provides a set of command buttons which automatically perform asolution, plot results, and compute engineering data specific to each handbookmodel. The Analysis tab also contains a Design Study feature which makes it possi-ble to evaluate design variations by selecting design variables which will be sys-tematically changed during a series of solution computations.

The “Results” tab provides a variety of post processing procedures that may be per-formed very conveniently within the handbook framework. Computing an estimateof the error in energy norm, plotting standard engineering quantities, computingminimum and maximum engineering quantities, computing engineering data atselected locations in the model, computing resultants, computing fracture mechan-ics quantities, or computing various engineering properties such as deformed area/volume or distortion, are possible options when using this interface.

The “Material” tab provides access to linear isotropic material property definitions.The user may modify existing material properties only.

The “Constraint” tab gives the user the possibility of changing the existing type ofconstraint. It applies to Built-In, Symmetry, Antisymmetry, Soft Simple and Freetypes.

For further details refer to the User’s Guide.


Interface layout

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2

FIGURE 6 Handbook library interface.

Icon Window

Handbook Tabs

“Handbook Library” Icon

Browser Icon


Standard file extensions

2

Standard file extensions

The StressCheck file system was completely redesigned in version 10.1 to simplify,improve stability, and make its usage intuitive. The input file (*.sci) and database(*.scm) have been replaced with the StressCheck workfile (*.scw) and the Stress-Check project (*.scp).

The StressCheck project file (*.scp) is designed to be the default file format whensaving and opening StressCheck data. This single file solution replaces the database(*.scm) and its dataset folder, so it contains all model information and all solutiondata. If a project is solved, saved, and closed, the solution data is immediately avail-able for post-processing when the project is reopened.

StressCheck first opens with a new empty project. If any parameters, formulae,geometric or mesh objects, etc. are created then they are added to the current proj-ect. The project can be saved in its current state with File Menu > Save or pressingthe Save icon on the main toolbar. The first time Save is pressed, a dialog willprompt for a file name with the *.scp project extension. This becomes the currently-opened project. Any subsequent save operation will modify the current *.scp proj-ect, as is standard behavior for programs designed for the Windows® operatingsystem1. The path to the current project is displayed in the StressCheck title bar andin the Model View window title bar.

The current StressCheck project can be changed with File > Save As. The previousproject file will not be modified.

A new project can be opened with File > New or by pressing the New icon on themain toolbar. This will close the current project without modifications and create anew empty project.

An existing project can be opened with File > Open, or by pressing the Open iconon the main toolbar. This will close the current project without modifications beforeopening the existing project file. Any existing project can also be opened in a newsession of StressCheck by double-clicking on its *.scp file.

A significant feature of the project file is that StressCheck does not write to itduring a session unless the user explicitly chooses to save. All temporary files arekept in a separate “scratch” location, the path of which can be changed by the userin the Options dialog (File->Options).

The StressCheck workfile (*.scw) replaces the StressCheck input file (*.sci). Assolution data can significantly increase the file size of StressCheck projects, the


File menu

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workfile exists as a smaller alternative that does not contain solution data. It isa snapshot of the model in its current state.

A StressCheck workfile can be exported from a StressCheck project at anypoint with File > Export or by pressing the Export icon on the main toolbar.The workfile is the default file format in the Export dialog.

File menu

The following sections provide a brief summary of the options found in theMain Menu Bar, FILE pulldown menu. If an icon exists for a specific opera-tion, it will be shown to the right of the command name.

New Discard current session and start a new project. Note: if a StressCheck project(.scp) was saved during the session, all information up to the last save will beunaffected (i.e. does not erase contents of the last opened .scp).

Open Supports the project (*.scp) and workfile (*.scw) file formats as well as thelegacy database (*.scm) and input file (*.sci) formats. Double-clicking on anysupported file will act as an open operation and bring the file data into a newStressCheck project. Legacy dataset folders can be converted to project files byopening the corresponding *.scm and then saving in the new format. Any solu-tion data in the dataset folder will become a part of the project file.

Save Saves the current project in a *.scp file, including all model information and allsolution data. The first Save will act as Save As, and then any following saveoperations will modify the currently opened project.

SaveAs Saves the current project in a new *.scp file. Any previously opened projectwill remain unmodified.

Import Imports new data into the current project. The following file types are sup-ported:

• CAD files


File menu

2

• Parasolid (*.x_t; *.x_b)

• IGES (*.igs)

• CATIA V4 (*.model; *.session; *.exp)

• CATIA V5 (*.CATPart; *.CATProduct; *.CATShape; *.cgr)

• STEP (*.step; *.stp)

• Pro-E (*.prt; *.asm; *.xpr; *.xas)

• Unigraphics (*.ug)

• Mesh Data

• Nastran mesh and point loads (*.bdf; *.nas; *.dat)

• LS-Dyna mesh and residual stress data

• MeshSim mesh (*.sms)

• StressCheck Append data

• Append data created with TranslatePoints utility (*.sci)

• StressCheck Parameter data

• Parameters from a StressCheck file (*.par)

Export Exports data out of the current project. The following file types are supported:

• StressCheck Workfile (*.scw)

• CAD files

• Parasolid (*.x_t; *.x_b)

• IGES (*.igs)

• CATIA V4 (*.model; *.session; *.exp)

• CATIA V5 (*.CATPart; *.CATProduct; *.CATShape; *.cgr)

• STEP (*.step; *.stp)

• Captures of the model view

• Images (*.jpg; *.png; *.tif)

• 3D representations (*.hmf; *.hsf; *.stl)

• StressCheck compatibility workfile (*.sci)


Edit menu

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• StressCheck Parameter data

• Parameters from a StressCheck file (*.par)

Exit Closes StressCheck.

A complete description of the View Session Log, and View Error Log optionsis given in the User’s Guide.

Edit menu

The following sections provide a brief summary of the options found in theMain Menu Bar, EDIT pulldown menu.

Undo Use this option to reverse the effect of the previous data transaction. The Undoapplies only to creation, deletion, and modification of geometric objects, andother input records. It does not apply to selection, blanking, rotation, or otherdisplay related operations. The Undo operation may be repeated indefinitelyuntil the entire sequence of input operations is reversed. Note: Solution data isnot preserved after an Undo operation.

Redo Use this option to re-apply a data transaction which has been reversed with theUndo operation. Like the Undo, Redo applies only to creation, deletion, andmodification of geometric objects and other similar input records. The Redomay be repeated until all Undo operations have been reapplied.

Model Info This option provides access to the Model Information window. The creation ofthe icon for the model, the problem title and comments, and the entering andediting of parameter definitions is done through the corresponding dialog win-dow. A complete description is given in the User’s Guide.

Input The Input option provides access to the various input classes, including Geom-etry, Mesh, Section Properties, Thickness, Materials, Loads, Constraints, and


Class menu

2

Solution ID’s. When selected, the StressCheck Input dialog window will appear inwhich you will find a tab for each available input class.

Solution The Solution option provides access to the various StressCheck solver options,including Linear, Nonlinear, Modal, Buckling, Measurement, Margin Check andCrack Path analysis. When selected, the StressCheck Solution dialog window willappear, and there will be a tab for each solver option. Once you have entered therequired information for the desired solver, select the SOLVE! tab to activate thecorresponding solution procedure.

Results The Results option provides access to the various output classes, including ErrorEstimation, Plot, Min/Max, Points, Resultant, Properties, and Fracture Mechanics.When selected, the StressCheck Results dialog window will appear, and there willbe a tab for each results option.

Handbook The Handbook option provides access to the StressCheck Handbook Library inter-face, including the handbook Model Info, Analysis, Results, Material and Con-straint options. When selected, the StressCheck Handbook dialog window willappear, and there will be a tab for each option.

Formulae The Formulae option provides access to the dialog window for entering and editingformula record definitions.

For more details and the description of other menu options, refer to the User’sGuide, Chapter 2.

Class menu

The class menu provides quick access to the various Input and Results class inter-faces. Simply select the Input or Results class of interest and a dialog window willappear, containing a set of “property sheet” tabs, with the appropriate tab automati-cally selected.


View menu

22

2

Classes provide the basic organizational structure for input and results interac-tion in StressCheck. Input classes include Geometry, Mesh, Thickness, SectionProperties, Material, Load, Constraint, etc. Each Input class provides access tomodel objects and input data records which define the finite element model.

Results classes include Error Estimation, Plot, Points, etc. The Results classesprovide access to the various post-processing features of StressCheck. Post-processing requires selection of the desired results class, followed by selectionof the solution(s) of interest and various options related to the chosen resultsclass.

View menu

The View pulldown menu provides quick access to the various StressCheckdockable tool bars. You may remove a tool bar from the display, or replace itagain by selecting the corresponding menu option from the View Menu.

Views Toolbar Choose View > Views Toolbar to obtain the icons for all the available view per-spectives and other display manipulation operations.

You may select a predefined view of your model from the Views Toolbar; forexample, to get a 3-dimensional view of your model click on the Isometricview. The Isometric view is a 3D view with a 45 degree rotation about the x-axis and a -35 degree rotation about the y-axis. You may store a particular viewof your model, and then restore the model to this precise orientation at a later


View menu

2

time using the Save and Restore options in the Views Toolbar. You may fit the cur-rent orientation of the model into the screen by selecting Center Model.

Edit Toolbar The View > Edit Toolbar contains icons for quick access to object editing featureswhich may be used to cancel selected objects, blank selected objects, unblankblanked objects, and to undo or redo previous operations.

Undo

Redo

Cancel Highlighted Objects

Cancel Specific Object Type

Blank Objects

Unblank Objects

Display Reset

Reveal Blanked

Invert Selection

Select Any Object

Select Unobscured Objects


View menu

24

2

Attributes The View > Attributes Toolbar contains icons for quick access to the modelattributes (loads, constraints, etc.) in the graphic display area. To control scal-ing of the attribute symbols, you must interact directly with the correspondingsection property class tab of the Input dialog window.

Display Objects The View > Display Objects Toolbar contains icons for controlling the objectsbeing displayed in the display window.

Display Thickness

Display Section Properties

Display Materials Display p-Level

Display Loads/Flux

Display Constraints/Temperature

Display Points

Display Nodes

Display Systems Display Fasteners

Display Elements

Display Text

Display Curves

Display Surfaces

Display ObjectsDisplay Mesh Layers


Display menu

2

Display Options The View > Display Options Toolbar contains icons for better visualization of yourmodel.

Display menu

There are several ways to manipulate the contents and appearance of the graphicdisplay information. These options are contained in the DISPLAY pulldown menuin the Main Menu Bar and in the View Controls dialog box (Display > View Con-trols).

Reset Reconstruct the main window display.

Move You may change the orientation of the model on the screen by translating, zooming,or rotating. Model orientation may be manipulated dynamically using the mousecursor. First you must choose the type of orientation operation you wish to performby selecting Display > Move in the main menu or clicking the appropriate icon inthe Views Toolbar. Translation, Rotation, and Zoom are self explanatory. Just pressthe right mouse button and drag the mouse while you hold down the button. TheBox Zoom option is provided so that you may draw a rectangle around the area ofinterest and it will be expanded to fill the display window.

Axis/Legend

Perspective

Toggle Light Source

Wireframe

Hidden Lines

Shade Cutting Plane

Shrink Elements

Element Edges

Element Handles

Surface ShadeSurface Grid

Wetted Faces


Display menu

26

2

Objects The Display > Objects dialog window shown in FIGURE 7 provides a mecha-nism for controlling the display and labeling of each type of object. The label

check box will turn the object labels on or off. The display check box willenable or disable the display of each object type. If you wish to view a specificrange of objects, or a specific set of objects, select the corresponding tablabeled “Ranges” or “Sets”. Each object is assigned an object number, whichmay be used to display a range of objects. Sets may be created using the inputSets class, and may be referenced in the Sets tab to display only the objectsbelonging to the selected set.

View Controls Model orientation may also be controlled by bringing the Display Controls dia-log box shown in FIGURE 8 to the screen by activating Display > View Con-trols. This box also contains input fields for controlling the size of eachrotation step, translation step, and zoom step. In addition, you may control theshrink option for the elements. The resolution of geometric boundary objectsand element edges may be increased to improve display precision, or decreasedto improve display speed. The Display Format controls the precision of thedata values displayed in the Geometry Input box and the Input Check reports.This is a C language format specification.

FIGURE 7 Display Objects.


Display menu

2

Attributes The Display > Attributes menu contains options for displaying various model attri-butes in the graphic display area such as loads or constraints, etc. To control scalingof the attribute symbols, you must interact directly with the corresponding propertysheet class tab of the Input dialog window. Attribute display may also be controlledusing the View > Attributes Toolbar discussed earlier.

Selection The Display > Selection menu provides a mechanism for controlling the display ofblanked objects.

FIGURE 8 View Controls.


Display menu

28

2

Model Icon Display > Model Icon displays the Icon Window associated with your currentmodel.

Model Summary Display > Model Summary allows you to obtain a summary of model informa-tion such as the number of elements and number of nodes. The Model Sum-mary window is illustrated in FIGURE 9.

Material Summary Display > Material Summary allows you to obtain a summary of standardmaterials currently used in your model. This summary carries useful informa-tion about the material including its type (isotropic, orthotropic, anisotropic) itsnonlinear behavior law (Ramberg-Osgood, Elastoplastic, Bilinear, etc.) and soon. For more information refer to the User’s Guide.

FIGURE 9 Model Summary window.


Tools menu

2

Assign Colors Display > Assign Colors provides options for displaying in grayscale, default col-ors, or a user defined color scheme.

Tools menu

The Tools menu provides access to a few additional features of StressCheck that areused relatively infrequently. For the description of the Mode, Convert ElementMapping, Set Browser, Table Reset, Set Font, and User Preferences options refer tothe User’s Guide.

General interface conventions

Since StressCheck is based on Windows graphic user interface development tools,there are several standard conventions for interacting with the program. For adescription of the on-line Help, Tab navigation, Input evaluation, Window sizing,Abort process, Input autosave, Reserved parameters, Graphic and Text input, andsome important guidelines for navigating through the StressCheck interface refer tothe User’s Guide.



30

2

C/A/O/M The user interface frequently makes use of a Class > Action > Object >Method convention for command interpretation. This can be roughly com-pared with declarative sentence construction. The Class tells the program whattype of data you wish to work with: Geometry, Mesh, Material, etc. TheAction is the verb of the command telling the program what action you wish toperform: Create, Select, Edit, etc. The Object will be acted upon when thecommand is performed, as when we create a point, select a circle, move anode. The Method is how the Action will be performed on the Object. Forexample, we might create a node as an intersection of two boundaries. Thisapproach is also used when specifying boundary conditions and loads. Youmight Select (action) a Curve (object) to apply a load by Traction (method).

Note that the program constructs a message at the bottom of the display areabased on the current action, object and method. This is how the program keepsyou informed of what input is expected from you in the graphic display area.

Graphic feedback StressCheck provides several types of feedback to assist in the interpretation ofgraphic display information. This is accomplished by varying the cursor icon,the color of individual object types, and by varying the type of lines used todisplay objects.

Cursors: Each time you change the action in StressCheck, the cursor willchange to reflect the current action. Once you learn the different icons used byStressCheck, you will be able to determine quickly what action the program iswaiting for. For example, the select action uses the hand icon. As long as thehand icon appears on the screen, the program is ready to mark the next objectselected. No matter what icon is displayed, you are free to make menu selec-tions or to manipulate any buttons or text fields available to you in the userinterface. The only information the cursor icon conveys is the currentlyselected action, which will be invoked by a graphic cursor pick (left mousebutton click in the graphic display area).

Colors: Each type of object is displayed in a different color. For example,boundaries are displayed in one particular color, elements in another color, etc.When an object is selected or blanked, it is displayed in yet another color. Thismakes it easy to interpret the status of each object displayed.

Line Types: Line type is another way to distinguish objects. Boundaries areusually displayed with dashed lines and elements with solid lines when bothelements and boundaries are selected for display. This is so that when youselect a boundary, it is still possible to see the underlying element edge



2

between the dashes of the selected boundary. When elements are not selected fordisplay, boundaries are displayed with solid lines.

Selection Object selection is accomplished by clicking the left mouse button while the mousecursor is pointing to the desired object. To select more than one object you mayclick the left mouse button while dragging the mouse across the display area anddrawing a box around them. Only objects which match the specified object typewill be selected. Since you are selecting many objects at once, no information isdeposited in the geometry input fields. To cancel a single selected object whileretaining the selection status of other selected objects, depress the Ctrl key whileclicking the left mouse button.

It is important to remember that the mouse cursor is always ready to perform thecurrent Action > Object > Method command when you press the left mouse button.

Dynamic operations All dynamic display operations can be performed by dragging the mouse across thedisplay area with the right mouse button depressed. This technique is used for rota-tion, translation, dynamic zoom and box zoom.

The right mouse button is also used to select a point or node as the center of rota-tion.

Clicking the right mouse button in the model window without dragging will indi-cate that a multi-step operation should be aborted.

For a complete description about the user interface refer to the User’s Guide, Chap-ter 2.



32

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3 The Handbook

3

Handbook framework

The Handbook Framework in StressCheck is a simple yet powerful environmentfor solving analysis problems encountered in routine and variant design. The hand-book framework consists of: a Model Information interface which provides abrowser to explore handbooks and handbook models; an Analysis interface forsolving and analyzing a user selected model with user specified design dimensions,using pre-defined solution methods and post-processing procedures; a Resultsinterface for performing basic post-processing operations such as error estimation,contour plotting, and point function extraction in a simplified setting; a Materialinterface and a Constraint interface.

Handbook library

StressCheck provides several default handbooks which contain a variety of modelproblems which are intended to serve as a sampling of the kind of problems that canbe constructed and placed in a handbook to be solved by a typical design engineer.Most problems found in the Handbook Library have been defined in parametricform, though this is not a requirement. Handbook models may be used in a produc-

Getting Started Guide Chapter 3: The Handbook 33

Handbook interface

34

3

tion environment where dimensions will be modified, load magnitudesadjusted, or material coefficients changed in order to evaluate the engineeringcharacteristics of a particular design. Also, models may be entered into a hand-book simply to capture a static component design. In this way, the handbooklibrary serves as a repository of design knowledge for future reference.

Handbook interface

Upon selecting the Handbook Library icon from the Main toolbar, the Hand-book interface shown in FIGURE 10 will appear. The Handbook interface rep-resents the starting point for handbook analysis and post-processing activities.The Model Browser is activated by clicking on the Browser icon in the ModelInfo tab of the Handbook interface. It serves to select the directory folder ofinterest and then the specific model from the chosen folder. Once a handbookmodel has been selected, you may use the operation tabs to perform an analy-sis, and post process the solution.

FIGURE 10 Handbook interface.

Operation Tabs

Library Icon (Main toolbar)

Browser Icon

(Model Info tab)

Chapter 3: The Handbook Getting Started Guide

Handbook interface

3

Model Browser

FIGURE 11 shows one of the forms that the handbook browser interface may take,when the model view option is selected. A handbook is just a collection of relatedStressCheck models which have been grouped together for the convenience of theuser. StressCheck currently provides the following handbooks: Basic, Beam, Frac-ture, Parts, Training and Tutorial.

The Basic Handbook focuses on simple design details that might be found in a tra-ditional engineering handbook such as a filleted corner, or a plate with a hole.

The Beam Handbook focuses exclusively on beam models of simple frames andtrusses.

The Fracture Handbook contains models used specifically for performing fracturemechanics computations, including multi-site damage calculations and problemsinvolving a multi-material interface.

FIGURE 11 Handbook model browser:

View Menu


Handbook interface

36

3

The Parts Handbook contains models which represent parts such as latches,torque arms, crankshaft sections, bathtub fittings, etc. These models frequentlycome from benchmark problems posed by StressCheck customers.

The Training Handbook contains problems of particular interest to a new userof StressCheck who might like to see what sorts of problems StressCheck hasbeen used to solve, and to find out how certain capabilities can be used in thecontext of a particular problem. For example, the handbook contains modelsthat demonstrate the use of StressCheck in unique fastened connection analy-sis, cold-working analysis, fiber wound composite material modeling, etc.

The Tutorial Handbook contains example problems from the Analysis andAdvanced guides.

Model Icon

Once you have selected a handbook model and loaded it into StressCheck, apictorial representation of the model can be obtained by clicking on the ShowIcon button in the Handbook interface (FIGURE 12).

Model Viewer You may choose to have a visual summary of handbook icons (View Menu >Thumbnails) or a list of the model file names (View Menu > List) in the ModelBrowser window. You may scroll the viewer using the browser scrollbar.

FIGURE 12 Handbook model icon.


Solving a handbook problem

3

To load the model into StressCheck point to the icon in the viewer and double-clickthe left mouse button.

Comments

The Handbook interface also displays textual information describing characteristicsof the model that the author thought would be important to a user such as a descrip-tion of the material used, a reference to the original source of the model, or com-ments about limiting values of stress data.


Selecting a problem

After opening a StressCheck session, switch to the Handbook Interface. Click onthe Browser Icon to access the Model Browser. Choose the Parts Handbook anddouble click on the bolt.sci file. The problem entitled Bolt head in tension (washersupport) will be loaded into StressCheck.

Once a problem is loaded into StressCheck, the finite element mesh appears in theModel Window with the load and constraint attributes. The finite element mesh foreach problem is designed to provide good convergence properties for a wide rangeof parameter values, consistent with the goal of the analysis. Whenever possible,symmetry conditions are used.

FIGURE 13 shows a sketch of the problem. The bolt is loaded in tension and is sup-ported by a washer. The objective of the analysis is to compute the magnitude andlocation of maximum first principal stress for the following value of the parame-ters: a=0.5, di=0.75, Do=1.5, F=5000, hw=0.125, L=1.5, rf=0.075. The bolt ismade of steel ASTM A-36 (E=29x106 psi, v=0.295), and the washer material is analuminum alloy with Ew=10x106 psi.

Parameters You have to update default values of the parameters to suit the dimensions require-ment. To update the value of the parameters select the Analysis tab at the top of theHandbook interface and then the All tab at the left; type the new numbers in thecorresponding fields. Once a new Value has been typed, you can use the Return keyto jump to the next parameter value. You may use the “=” key to enter an expres-



38

3

sion that will be evaluated immediately and the result deposited in the field.After you have modified all parameters, click on the Update button (FIGURE14).

F=5000 lb

washer

FIGURE 13 Bolt with washer support. All dimensions in inches.

L

a

rf

di

Do

hw



3

Refer to the model icon provided for a visual indication of the meaning of eachparameter.

Update When you are ready to update the model to reflect the new parameter values, justclick the Update button. If any parameter values violate their predefined limits, anerror message appears and the parameter values will be returned to their previousvalid settings.

Saving parameters If you want to save current parameter settings or retrieve previously saved parame-ter settings for a model, use the Analysis tab together with the Settings tab or theFile tab at the bottom of the Handbook interface. FIGURE 15 illustrates how theHandbook interface will look if you wish to save this new configuration of the bolthead in a file. Enter the name you want to assign to this parameter setting in the“Name:” field, then use the Browser button to select the location for the file andclick on the Write button. The parameter values will be stored in that place underthe name bolt_new.par.

FIGURE 14 Saving new configuration for handbook problem.



40

3

Executing the analysis

Choose the Input tab in the Analysis interface if you wish to solve the currentlyselected handbook model using the procedures defined by the author of thehandbook model.

FIGURE 16 shows the Analysis and Input tabs of the Handbook interface, theicon and parameters for the selected problem and the finite element mesh con-sisting of 11 quadrilateral elements, with the loading and constraint symbols.The support provided by the washer is modeled as a spring constraint with thespring coefficient given by the ratio between the modulus of elasticity and thethickness of the washer. Once you have made the desired parametric changes,simply click on the Solve button to invoke the solution procedures defined forthis particular model.

The execution parameters for this model have been assigned so that a Down-ward-p extension (from p=8 to p=1) is initiated in the automatic mode afterclicking on the Solve button.

FIGURE 15 Save new configuration in a file.



3

Post-processing

The “Results” tab provides a variety of post processing procedures that may be per-formed very conveniently within the handbook framework. Computing an estimateof the error in energy norm, plotting standard engineering quantities, computingminimum and maximum engineering quantities, computing engineering data atselected locations in the model, computing resultants, computing fracture mechan-ics quantities, or computing various engineering properties such as deformed area/volume or distortion, are possible options when using this interface.

FIGURE 16 Analysis tab, problem icon and mesh for handbook problem.



42

3

FIGURE 17 Handbook Results: Bolt head example.



3

Design Study Tab

Choose the Design Study tab if you wish to perform a “What If?” type of analysisfor the current handbook model. When performing a design study, you controlwhich parameters(s) will remain constant, and which parameters(s) will varyduring the analysis. You also control how many steps will be performed duringwhich the variable parameters will be varied from their initial to their final values.

The Design Study interface (FIGURE 18) provides access to the definition of eachparameter defined for the model. Each parameter may be either Constant or Vari-able. When a parameter is constant, its value remains constant for each step of thedesign study. The value of each variable parameter will change during the designstudy. To make a parameter variable, simply check the box at the left of the param-eter name. To make a parameter constant, un-check the box.

# Steps You may supply the number of steps to perform during the parametric analysis. Thenumber supplied will be used to determine the value of the scale which in turn isused to compute the value of each variable parameter.

Scale The current value of each variable parameter is determined by the Scale value (S)as shown below:

a = a min + (a max - a min)S

FIGURE 18 Design Study interface.


Handbook library expansion

44

3

You may preview the parametric configurations of the model by activating thescale (enable the Scale check box), and clicking the up or down arrows toincrease or decrease the scale value. The Scale value will vary from 0.0 to 1.0in increments of 1/(Steps-1).

p-level During a design study, the assignment of p-levels to the elements is held con-stant. The p-level you enter will be assigned to all elements which have beendesignated as variable in the definition of the model. All elements designatedas having fixed p-level will retain their assigned value.

Solve When you are ready to begin the design study, simply click the Solve button.The model will be updated automatically and the resulting configuration willappear in the model window. The solution for each design configuration willbe saved for subsequent post-processing.

Handbook library expansion

An important feature of the Handbook Framework is the capability to add newmodels to the Handbook Library. This is discussed in the User’s Guide.


4 Tutorial

4

This chapter contains guidelines for the preparation of input data, obtaining a linear solution and per-forming post solution operations for problems in Planar and 3D Elasticity. Working a simple exampleproblem in a lock-step fashion will allow you to develop an understanding of the program characteris-tics and its capabilities.

Planar elasticity problem

Opening a new project

To run StressCheck double-click on the StressCheck icon. Note that after openinga new project, the default analysis type is 3D Elasticity and the default units are inthe US customary system (in/lbf/sec/oF). From the Reference and Theory Selec-tors select Planar Elasticity. If you are working from an existing new project,check the Reference and Theory Selectors and adjust them if necessary. Undereach analysis mode, all the input forms contain the appropriate fields and function-ality supported for the reference and theory.

Getting Started Guide Chapter 4: Tutorial 45


46

4

You can always exit from the program any time you wish by selecting the File> Exit menu option. Don’t be afraid to browse through the menus and dialogboxes, there are not hierarchic menus to get lost in.

Units

Once you start creating geometric objects it is not possible to change theunits from the selector. Therefore, it is very important to select the properunits before starting a session. Three options are possible: in/lbf/sec/F, mm/N/sec/C and Other.

Problem description

A rectangular plate with a circular hole in the center (FIGURE 19) is loaded bya constant traction Tx=0. It has unit thickness, a length to width ratio (L/W)of 3. The material is ASTM-A36. Assuming plane stress conditions, the goal ofthe computation is to determine the gross section (Kt) and net section (Kn)stress concentration factors for a diameter to width ratio (a/W) of 0.45.

By definition the gross section stress concentration factor is:

(1)

and the net section stress concentration factor is

(2)

Making use of symmetry (geometry and loading), it is possible to work withonly one-fourth of the problem. This symmetry consideration will simplifymodel creation and reduce solution time.

We will formulate the mathematical problem as shown in FIGURE 20.

Kt

max0

--------------=

Kn

max0

-------------- W a– W

------------------=

Chapter 4: Tutorial Getting Started Guide


4

Specification of units for is not important because the data of interest, Kt andKn are dimensionless.

2a

L=30

=100

FIGURE 19 Rectangular plate with a central hole.

a=4.5 W=10

5.0

15.0A B

CD

E

AB: un = Tt = 0.0 (symmetry)

BC: Tn = 100, Tt = 0.0

CD: Tn = Tt = 0.0 (stress free)

DE: un = Tt = 0.0 (symmetry)

x

y

FIGURE 20 The solution domain and boundary conditions.

2.25



48

4

Entering geometric data

From the Main Toolbar select the Create Model icon and then select the Geom-etry tab in the Input dialog window (FIGURE 21). Geometry provides for thespecification of the solution domain using points, lines, circles, rectangles, etc.StressCheck lets you separate the definition of boundaries from the definitionof the finite element mesh. You will find that this feature gives you a great dealof flexibility and convenience. You will be able to change the mesh and thenew elements will be assigned the correct boundary conditions by StressCheckautomatically. Refer to the User’s Guide for a detailed description of geometryconstruction in StressCheck.

FIGURE 21 Geometry input.

Create Model Icon



4

To specify the domain, select the Geometry tab in the Input dialog box, and thenconstruct a rectangular domain using the following steps:

• Geometry tab > Action: Create > Curve Selector > Object: Rectangle> Method: Locate > Input: (Make sure the toggle switch is ON) X: 0.0 > Y:0.0 > Z: 0.0 > Width: 15 > Height: 5 > Rot-Z: 0.0 > Button: Accept.

Note that the logical sequence was to select the Class: Geometry, an Action: Create,an Object: Rectangle, and the method by which the object is to be created (Method:Locate), that is, specify the data which define the rectangle (the coordinates of avertex point, the width and the height, measured from the vertex point). The result-ing rectangle consists of four lines and four points.

Define next the inner circle by the commands:

• Geometry tab > Create > Circle > Locate > Input toggle switch ON > X: 0.0> Y: 0.0 > Z: 0.0 > Radius: 2.25 > P1-Min: 0 > P1-Max: 90 > Rot-Z: 0.0 >Click on the Accept button. Click on the Center Model icon in the Viewstoolbar.

This completes the specification of the solution domain (FIGURE 22).

Select the Mesh tab when you are ready to define nodes and elements. Nodes maybe associated with previously defined points, specified as intersections of twoboundary curves, assigned as offsets on boundaries, defined directly, etc.

FIGURE 22 Solution domain for the problem.



50

4

Designing the mesh

A general rule is that finite element meshes should be constructed so that thevertex angles of triangular elements are as close to 60 degrees as possible, andthe vertex angles of quadrilateral elements are as close to 90 degrees as possi-ble. The p-version is much more ‘forgiving’ with respect to deviation from theoptimal vertex angles than the h-version, nevertheless vertex angles should notbe less than 5 degrees or greater than 175 degrees.

To construct the mesh shown in FIGURE 23, the first step is to define thenodes. Nodes 1 to 5 can be created by the method of intersection.

• Mesh tab > Action: Create > Object: Node > Method: Intersection.Click on the boundary segments near the intersection points where anode is to be located. StressCheck indicates the node by a small square.

Note: The numbering sequence for the nodes is unimportant.

Create node 6 as offset on the given circle, by selecting:

• Mesh tab > Create > Node > Offset > Offset: 45. Then click on the cir-cle.

At this point you could construct a finite element mesh by using 2 quadrilateralelements. However, this wouldn’t be a good decision. Both elements, thoughacceptable, would have a deviation from the optimal 90 degrees vertex anglesthat can be avoided easily using 3 quadrilateral elements. To construct a wellbalanced 3 elements mesh, let’s create two extra nodes.

FIGURE 23 Finite element mesh.



4

• Mesh tab > Create > Node > Locate > X: 5 > Y: 0 > Z: 0 > Accept. (Node 7)

• Mesh tab > Create > Node > Projection. Click on node 7 and, while holdingthe Control and Shift keys, click on Line 3 then, click on Accept. Node 8will be created on the line.

Now you are ready to create the elements. To create a quadrilateral element select:

• Mesh tab > Create > Quadrilateral > Selection.

Then, click on the four nodes which define the element in any order. Three ele-ments are defined by associating the appropriate nodes.

Checking the mesh

In order to ensure that all elements are properly connected, that is, there are nounintended free edges, select:

• Mesh tab > Check > Edge > Free Edge.

If there are element boundaries which are not connected to other elements they willbe highlighted.

To check for distortion, select:

• Mesh tab > Check > All Elements > Distortion > Accept. A report contain-ing the smallest and largest vertex angles found in the elements will be pro-duced in the edit window. The default range for the vertex angles isbetween 5 and 175 degrees.

Assigning thickness

For problems of Planar Elasticity (plane stress) it is necessary to associate somethickness with the elements. To assign thickness, click on the Thickness tab in theStressCheck Input dialog box (FIGURE 24) and complete the following informa-tion:

• Thickness tab > Action: Select > Object: All Elements > Method: Selection> Thickness: 1.0 > System: Global > Click on the Accept button and Stress-Check will confirm your entry in the scrolling list.



52

4
Entering material properties
To enter the material properties you must provide two types of information:definition of material properties and assignment of material properties. Bothactivities are performed by selecting the Material tab in the StressCheck Inputbox. FIGURE 25a shows the material interface displayed on the screen whenthe Define tab is used for providing the material coefficients. FIGURE 25bshows the interface when the Assign tab is used for assigning the defined prop-erties to the elements in the mesh. After selecting the Material tab, completethe following information:

• Define tab > ID: STEEL > Material: Linear > Type: Isotropic > Units:US > Case: Pl. Stress > E: 2.9e+7 > v: 0.295 > Accept. (Note that the

FIGURE 24 Thickness input.



4
input fields for the density and coefficient of thermal expansion do not needto be specified for this problem.)
• Assign tab > Action: Select > Object: All Elements > Method: Selection >ID: STEEL > Accept.

Entering load data

To enter load data select the Load tab in the StressCheck Input box. The input areawill appear as shown in FIGURE 26. Specify a unique name which identifies theloading case you are about to enter. In engineering practice often multiple loadcases must be investigated, each load case must be given an unique name in the IDfield.

To create a load record select the Load tab and complete the following information:

FIGURE 25 Material properties input.

(a) (b)

Define tab Assign tab



54

4
• Load tab > Action: Select > Object: Any Curve > Method: Traction >
ID: LOAD > Direction: Norm/Tan > Normal: 100. Use the mouse cur-sor to select the right side of the rectangle (Line2 in FIGURE 22).Click on the Accept button. The load symbols will appear on the meshas shown in FIGURE 28.

Several types of loading such as traction, spring displacement, body forces orpoint loads are available for Planar Elasticity. Traction loading means that adistributed load (in force per unit area) is imposed on a boundary or edge.Traction is a vector quantity. Thus, two vector components must be given.These may be in the normal-tangent reference frame, in the global system, oran arbitrary local system. Traction loads can be applied to geometric boundar-ies or element edges, including beam elements.

FIGURE 26 Input area for load.



4

Check applied load StressCheck makes it very convenient to check the magnitude of the appliedmechanical loads. To check the load vector components Fx, Fy, and the moment Mzat X=0, Y=0, select the following options:

• Load tab > Check > All Elements > ID: LOAD > Moment-X: 0.0 >Moment-Y: 0.0 > Accept.

The edit window will report:

Note that: Fx=o x W/2 x thickness=100 x 10/2 x 1=500.

Entering constraint data

To enter constraint data select the Constraint tab in the Input dialog box (FIGURE27). Specify a unique name for the constraint data you are about to enter. This isnecessary because StressCheck allows more than one constraint case to be entered.Each case must be identified by a unique name.

Several types of constraints such as General, Symmetry, or Spring Coefficient areavailable. When the Symmetry constraint is selected, the normal displacementcomponent is set to zero. Symmetry constraints are applicable only to straightedges. To specify a symmetry constraint, the objects curve or edge must be selectedfirst.

• Constraint tab > Action: Select > Object: Any Curve > Method: Symmetry> ID: CONST. Use the mouse cursor to select the left side of the rectangleand then, holding the Shift key, click on the lower side of it (Lines 1 and 4



56

4
in FIGURE 22). Click on the Accept button. The constraint symbols(circles) will appear on the mesh as shown in FIGURE 28.
FIGURE 27 Input area for constraints.

FIGURE 28 Specified boundary conditions.



4

Defining the solution ID

Because StressCheck allows more than one load case and constraint case to bedefined, it is necessary to associate a unique solution name with each desired con-straint and load name pair. To do this, select the Solution ID tab from the Stress-Check Input box. The constraint name(s) and load name(s) previously defined aredisplayed on this form (FIGURE 29).

To complete the solution record for this problem supply the following information:

• Solution ID tab > Action: Define > Object: Name > Method: Selection >Solutions tab > Solution ID: SOL > Constraint ID: CONST (or click onitem in listbox) > Load ID: LOAD (or click on item in listbox). Click on theAccept button.

Executing a linear analysis

To execute a linear analysis click on the Compute Solution icon from theMain Toolbar. When the Solver interface appears (FIGURE 30), select the Lineartab and complete the requested information.

FIGURE 29 Solution ID input.



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• Linear tab > Extension: Upward-p > p-limits: 1 to 8.

Choosing “Upward-p” extension means that the solution will be computedfrom the minimum to the maximum p-levels specified under p-limits. Thisoption requires more CPU time than the “Downward-p” but requires less diskspace. The highest possible p-level in StressCheck is 8.

Next, choose the SOLVE! tab to get the solution. Complete the requested infor-mation as shown below:

• SOLVE! tab > Execute: Initialize > Run Mode: Automatic > Method:Direct > Converge: None > Button: Solve. The status window will dis-play the progress of the solution (FIGURE 30).

We run an “Automatic” sequence of solutions from the initial (“Initialize”) p-level to the final. Method: “Direct” means that StressCheck uses a Directsolver for the solution of linear systems of equations.

Quality assessment and extraction procedures

To perform post-processing operations you must select the View Results icon from the Main Toolbar. (FIGURE 31)

FIGURE 30 Input area for linear analysis.

Linear tab SOLVE! tab



4

Error Estimate To obtain the relative estimated error in energy norm, select the Error tab from theResults dialog window and complete the following information:

• Error interface > Input tab > Solution: SOL > Run: 1 to 8 > Click on theAccept button.

For the example problem, the error estimate shown in FIGURE 32 is obtained. Thetabular results show the run number, the degrees of freedom (DOF), the computedand extrapolated values of the potential energy, the rate of convergence and the esti-

FIGURE 31 Results interface.

View Results Icon



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mated relative error in energy norm. Note that the estimated relative error inenergy norm is only 0.25% at p=8 (220 DOF).

StressCheck functions StressCheck computes a set of commonly used functions, such as stresses,strains, etc. in the global or local reference frame. The available standard func-tions are listed in Table 1. In addition, any combination of the standard Stress-Check functions can be computed through user-specified formulas or throughthe use of the calculator. Refer to the User’s Guide for additional details.

TABLE 1. Standard functions. Planar Elasticity.

Symbol Explanation and commonly used symbol

Ex Normal strain x

Ey Normal strain y

FIGURE 32 Relative error in energy norm for example problem.



4

Plotting the data StressCheck provides convenient means for displaying and printing computedinformation in graphical form. To obtain the deformed configuration plot over theundeformed shape, select the Plot tab from the Results window and proceed as fol-low:

• Plot tab > Select > All Elements > Selection > Solution: SOL > Run: 8 >Plot: Solution > Shape: Deform > Overlay ON > Midsides: 10. Click on thePlot button (FIGURE 33).

To plot the equivalent (von Mises) stress distribution, Seq, on the undeformedshape, make the following selection:

Ez Normal strain z Gxy Shear strain xy

E1 Principal strain 1 E2 Principal strain 2

Eeq Equivalent strain eq

Ux Displacement component in the x-direction ux

Uy Displacement component in the y-direction uy

Sx Normal stress x Sy Normal stress y

Sz Normal stress z

Txy Shear stress xyS1 Principal stress 1

S2 Principal stress 2

Seq Equivalent stress eq (von Mises)

Tmax Maximum shear stress max

Error Error indicator.

Fmla Formula. Using this option, any mathematical expression containing the standard functions can be computed for a given solution.

Calc Calculator. Using this option, any mathematical expression containing standard functions can be computed for any arbitrary combination of solutions.

TABLE 1. Standard functions. Planar Elasticity.

Symbol Explanation and commonly used symbol



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• Plot tab > Select > All Elements > Selection > Solution: SOL > Run: 8> Plot: Solution > Contour: Fringe > Shape: Undef. > Func.: Seq >Midsides: 10 > Range toggle switch ON, min: 0, max: 400 > Interval:10. Click on Plot and the contour fringes of the plotted function willappear in the display window (FIGURE 34).

Min/Max values To compute minimal and maximal values of displacement, stress and straindata, in the Results window select the Min/Max tab.

To compute the maximum value of the stress component x (StressCheckname Sx, refer to Table 1) for the eight available solutions, complete the entriesin the Results input area as follows:

• Min/Max tab > Select > All Elements > Grid > Solution: SOL > Run: 1to 8 > Function: Sx > Midsides: 10 > Maximum button ON. Click onAccept.

The convergence of the maximum Sx value will be displayed as a function ofthe number of degrees of freedom as shown in FIGURE 35. The estimated lim-its are also included.

FIGURE 33 Deformed shape.



4

FIGURE 34 Equivalent stress fringes.

FIGURE 35 Convergence of Sx maximum.



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The number of midsides represents the size of the search grid to locate themaximum. Note that the maximum value of Sx is practically independent ofthe degrees of freedom for p > 4.

Concentration factors

The gross and net section stress concentration factors for the p=8 solution arecomputed by determining the maximum normal stress at the edge of the holemax=x(0,2.25) and then using equations (1) and (2) with0=100. Using thevalue for p=8 (Sx=399):

(3)

The gross and net section stress concentration factors compare very well withthe published data. In “Stress Concentration Factors” by R. E. Peterson, JohnWilley & Sons, 1974, the values of Kt and Kn extracted from the curves onpage 150 are:

(4)

Ending the session

After the analysis is completed, or at any time after opening a new project, it isuseful to save your session to a StressCheck project file (.scp).

To save the StressCheck session data into a StressCheck project file, select File> Save from the Main Menu Bar or select the Save icon from the main tool-bar. The Save As Window appears overlapping the Model Window. Usingthe mouse, move the cursor to the File name field in this new window and typethe name you want to give to the file (do not include an extension) and thenpress the Return key or click on the Save button.

Save a StressCheck project file for the problem solved during this session withthe name: “PlateWithHole”, we will use it later (PlateWithHole.scp). Note: ifwe only wanted to save model data, we could use File > Export or selectthe Export icon from the main toolbar . We can then export the modeldata as a StressCheck work file (.scw).

aW----- 0.45 Kt 3.99 Kn 2.19= = =

aW----- 0.45 Kt 4.01 Kn 2.20= = =


Extrusion problem

4

To exit the program select File > Exit from the Main Menu Bar.

Extrusion problem

The Extrusion option in StressCheck provides a simple way to investigate theeffects of out-of-plane loads and constraints on bodies which are essentially two-dimensional. Extrusion is applicable only for components that are defined inthe XY-plane (Planar reference) and have piecewise constant thickness. Theloads and constraints (symmetry, antisymmetry, built-in) are automatically con-verted to their 3D equivalent when Extrusion is performed. Once a model has beenextruded all quadrilateral elements are converted into hexahedrals, and triangularelements into pentahedrals. It is also possible to add to or modify existing load andconstraint records before executing the analysis.

Extrusion constraints

When extruding a 2D model it is necessary to check if the constraints are sufficient.The following cases illustrate additional model constraints required when certain2D models are extruded. The four cases below illustrate the rules to convert 2Dnodal constraints, and to specify constraints on the extrusion side.

Double symmetry FIGURE 36 shows how double symmetry constraint applied in 2D should be com-plemented with nodal constraints in 3D applications.

FIGURE 36 Double symmetry: (a) planar - (b) extrude.

1 addition

Uz=0(one node)

symmetry(a)

(b)


Extrusion problem

66

4

Single symmetry FIGURE 37 shows how single symmetry plus a nodal constraint applied in 2Dshould be complemented in 3D applications.

Symmetry-antisymmetry FIGURE 38 shows how symmetry, antisymmetry and nodal constraintsapplied in 2D should be complemented in 3D applications.

Double antisymmetry FIGURE 39 shows how double antisymmetry plus a nodal constraint appliedin 2D should be complemented in 3D applications.

Let us extrude the planar problem described in the previous section.

FIGURE 37 Single symmetry: (a) planar - (b) extrude.

2 additionsUy=0

(two nodes)

Uz=0(one node)

symmetry

node constraintUy=0

(a)(b)

FIGURE 38 Symmetry and antisymmetry: (a) planar - (b) extrude.

1 addition

Uy=0(two nodes)nodal constraint

Uy=0

symmetry

antisymmetry

(a)(b)


Extrusion problem

4

Updating the model

Let us extrude the first planar problem described in the previous section. After start-ing a new session, or using File > New to begin a new project, open the PlateWith-Hole.scp.

• File > Open > PlateWithHole.scp > Double-click on the file name.

If you did not create the file, create the 2D problem as explained in the previoussection before continuing. The input data will be loaded and the finite elementmesh will be displayed in the Model Window.

From the Reference and Theory Selectors select Extrude Elasticity. The programwill convert the 2D problem you just loaded into a 3D-solid problem, as shown inFIGURE 40. Note that the original nodes that defined the 2D problem are the onlyones visible. This is a reminder that we are dealing with a solid created by extru-sion.

When extruding a 2D problem it is a good practice to carefully consider whetherthe boundary conditions defined in 2D are complete in 3D or not. In some casesthey will be complete, but in general they will not. In this example, we need toimpose a nodal constraint in the z-direction to prevent a rigid body translation. Thisis equivalent to the double symmetry constraint shown in FIGURE 36. To do this,select Class: Constraint from the Main Menu Bar or select the Constraint tab fromthe Input window and complete the input area as indicated in FIGURE 41:

FIGURE 39 Double antisymmetry: (a) planar - (b) extrude.

no change

Uy=0(one node)

nodal constraintUy=0

antisymmetry

(a) (b)


Extrusion problem

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4

• Constraint tab > Select > Node > Node > ID: CONST (Same name asused before in 2D) > Direction: XYZ > Data Type: Fixed (turn on theswitch) > System: Global > Turn ON the Z switch. Select node 1 (seeFIGURE 23), and then click on the Accept button to create the con-strain record.

A summary of the new constraint record is added to the scrolling list and theconstraint symbol is displayed on the element.

Note that the original constraint information provided in 2D was automaticallyconverted to its 3D equivalent when the model was extruded. Note also that thetraction load specified along an element edge in 2D is now distributed over theelement face.

Also note the Extrude toggle switch shown in the Constraint dialog box ofFIGURE 41. This switch is turned on when it is required to impose the nodalconstraint at both sides of the extrusion (see FIGURE 38).

FIGURE 40 Constraints for the extruded model problem.


Extrusion problem

4
Execution
You are now ready to start the computation. Select the Compute Solution icon fromthe Main Toolbar. When the Solver dialog window appears select the Linear taband complete the requested information as done before:

• Linear tab > Extension: Upward-p > p-limits: 1 to: 8.

• SOLVE! tab > Execute: Initialize > Run Mode: Automatic > Method: Direct > Click on the Solve button. A sequence of solutions of increasing polynomial order (from p=1 to p=8) will be obtained.

Extraction of results

After the execution is complete we can extract results from the finite element solu-tions. The procedures for estimating the error in energy norm, plotting the data of

FIGURE 41 Input box: Constraint tab.


Extrusion problem

70

4

interest, etc., are the same as those described for the 2D analysis. Following thesame steps, the results shown in FIGURE 42 will be obtained. Note that theresults are practically identical to those corresponding to the planar problem.

If the through-thickness distribution of the normal stress x is of interest, fromthe Results window, select the following options:

• Points tab > Input tab > Select > Edge > Selection > Solution: SOL >Run: 8 to 8 > Func(s): Sx > # of pts: 10 > Click on the “Display points”button > Select the element edge shown in FIGURE 43 > Click on theAccept button. To make it easier to select the edge of interest, turn offthe element shading.

Note that there is a variation of the normal stress in the thickness direction,with the maximum occurring at the center of the plate. The value of Sxobtained from the 2D model (FIGURE 35) should be close to the average ofthis distribution. Turning on the Average button shown in FIGURE 43, theintegral average of Sx along the edge will be obtained. the average is computedas

FIGURE 42 Results for the extrusion.


Three-dimensional problem

4

and the value is 391, which practically is the same value obtained from the 2Dmodel (399).

As demonstrated by this very simple example problem, the Extrusion option can beused for any problem defined in the Planar reference system. Once the model isextruded, the loads and constraints can be edited before executing the analysis.Care must be exercised to ensure that the three-dimensional body is properly con-strained. For example, if in this problem we did not enforce the nodal constraint inthe z-direction (any node can be constrained), then a rigid body translation alongthe z-axis would have been possible.


We are interested now in creating a 3D description for the same rectangular plateproblem analyzed in 2D, but with the thickness given in parametric form. An out-line of the steps for creating the geometry and finite element mesh, applying theload and enforcing the constraints is described in the following.

FIGURE 43 Sx along edge of maximum stress.

Edge

x1l--- x sd

0

l

=



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An alternative way of creating the geometric description using solids isincluded at the end of the chapter.

Creating the model

After starting a new StressCheck session, open the “Tension strip with a centralhole” input file created before (PlateWithHole.scp).

File > Open > PlateWithHole.scp > Double-click on the file name.

If you did not create the file, create the 2D problem before continuing. Theinput data will be loaded and the finite element mesh will be displayed in theModel Window.

From the Reference and Theory Selectors select 3D Elasticity.

To create the parameter for this problem, select the Model Info icon from theMain Toolbar and when the interface appears select the Parameters tab. Com-plete the following information (FIGURE 44):

• Parameters tab > Input tab (it’s at the bottom of the dialog box) Name: th > Description: Panel thickness > Value: 1.0 > Accept button.

There are several ways to produce the geometric description for this problem.We have chosen to update the model you already have from Planar Elasticity.

FIGURE 44 Parameter interface.



4

A useful feature of StressCheck is the Copy command. The Copy button at the bot-tom of the Input interface may be used to create copies of objects currently selectedin the graphic display area. The selected objects defined in global coordinates willbe copied and attached to a new local system. All of their associative objects will becopied and the associative relationship will be transferred to the new copies of therelated objects. Note that if the original group of objects contains elements, theresulting copy will also have elements.

We want to copy the 2D profile to a different z-plane (z=th). Select the Geometrytab from the Input dialog window and follow the steps indicated below:

• Geometry tab > Select > Any Object > Locate. Select the desired group ofobjects by drawing a box around the 2D model; this will cause the objectsto be highlighted. Make sure you have all object types active. Next, enterthe coordinates where the copy is to be located (Z=th), in the correspondinginput fields as shown in the FIGURE 45. Finally, click the Copy button.

Click on the Cancel button before continuing so no object remains highlighted.

Mesh The next step is to create the three hexahedral elements as shown in FIGURE 46. Inthe StressCheck Input window select:

• Mesh tab > Create > Hexahedron > Face to Face.

FIGURE 45 Copy operation.



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4

In this case, there is a one to one correspondence between the elements in theoriginal model and the elements in the copy. Move the cursor to the displayarea and click on an element in one section with a corresponding element in theother section until the 3 hexahedrals have been created.

Note: When performing the face to face meshing, a StressCheck Error mes-sage will appear on the screen after creating each hexahedral element. This isto inform the user of the incompatibility between element types (Quadrilateralsand Hexahedrals) and inconsistency of boundary conditions. Ignore these mes-sages since they will go away once the model is fully updated.

To delete the quadrilateral elements: Select > Quadrilateral > Selection, mar-quee pick all the quadrilateral elements, and then click on the Delete button.Use the Shrink Elements icon to improve visualization.

The mesh construction is now complete.

Loads To update the load record select the Load tab in the Input dialog window andclick on the Purge button. At this point a message will overlap the main win-dow “Do you really wish to Purge all data records?” Click on the Yes button.

• Load tab > Select > Face > Traction > ID: LOAD > Direction: Norm./Tan. > System: Global > Normal: 100. Move the cursor to the displayarea and click on the rightmost face of the element, then click on theAccept button. A distributed traction pointing in the direction of theoutward normal will be displayed on the element face.

Constraints To update the constraint record select the Constraint tab in the StressCheckInput dialog window and click on the Purge button. At this point a messagewill overlap the main window “Do you really wish to Purge all data records?”Click on the Yes button.

• Constraint tab > Select > Face > Symmetry > ID: CONST. Move thecursor to the display area and click on the three faces which lie on theplanes of symmetry while holding the Shift key. Click on the Acceptbutton.

As we did before with the extruded model we have to impose a nodal con-straint in the z-direction to prevent rigid body translation. To do this, completethe input area as follows:

• Constraint tab > Select > Node > Node > ID: CONST > Direction:XYZ > Data Type: Fixed > System: Global > Turn ON the Z toggleswitch. Select node 1, and then click on the Accept button to create the



4

constraint record. A summary of the new constraint record is added to thescrolling list and the constraint symbol is displayed on the node. The meshand boundary conditions for the 3D model are shown in FIGURE 46.

Execution and extraction of results

You are now ready to start the computation. Select the Compute Solution icon fromthe Main Toolbar. When the Solution dialog window appears select the Linear taband complete the requested information as done before.

After the execution is completed we can extract results from the finite element solu-tions. The procedures for estimating the error in energy norm, plotting the data ofinterest, etc., are the same as those described for the 2D analysis. Following thesame steps, for instance, you will obtain the estimated relative error in energy norm,the convergence of x maximum, the distribution of x along the edge, and theequivalent stress contour plot shown in FIGURE 47. Note that the results are prac-tically identical to those corresponding to the extrusion problem.

To assess the influence of the thickness in the results, change the thickness from 1to 3. To do that select the Model Info icon from the Main Toolbar and select theParameters tab. Click on the existing record in the Parameter dialog window and

FIGURE 46 The 3D model.



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FIGURE 47 Results for the 3D problem, th=1.



4

then type the new value of the parameter in the Value field. Click on the Acceptbutton. The model will be automatically updated. Rerun the analysis from p=1 to 8and perform the same post-processing operations as indicated before. Note that themaximum value of the equivalent (von Mises) stress, Seq, is practically the same asbefore, but the distribution of Sx along the edge of the hole is quite different (FIG-URE 48). The maximum value of Sx is now 410 instead of 403 for th=1 (3D-model) or 399 for th=1 (2D model).

Steps for solid model construction

This section provides a step by step description on how to create the geometry ofthe same model problem using solids. After starting a new StressCheck session, orbeginning a new StressCheck project, from the Reference and Theory Selectorsselect 3D Elasticity.

Create the parameter th as described on page 72, then select the Geometry tab inthe StressCheck Input interface, and construct a solid block using the followingsteps:

FIGURE 48 Results for the 3D problem, th=3.



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• Geometry tab > Create > Box > Locate > Data tab > Solid button on >Input toggle switch on > X: 0.0, Y: 0.0, Z: 0.0, Width: 30, Height: 10,Depth: th, Rot-X: 0.0, Rot-Y: 0.0, Rot-Z: 0.0 > Click on the Acceptbutton.

Next, define the hole by selecting:

• Geometry tab > Create > Cylinder > Locate > Data tab > Solid buttonon > Input toggle switch on > X: 0.0, Y: 0.0, Z: 0.0, Radius: 2.25,Height: th, Rot-X: 0.0, Rot-Y: 0.0, Rot-Z: 0.0 > Click on the Acceptbutton.

Having created the block and cylinder, we now create a body by using a bool-ean subtraction:

• Create > Body > Bool-Subtract > Click on the Box and then on the cyl-inder > Click on the Accept button. This operation creates a body con-sisting of a plate with a hole as shown in FIGURE 49.

To take advantage of symmetry, you need to clip the plate with two planes asfollows:

• Create > Plane > Locate > Input toggle on > X: 0, Y: 0, Z: 0, Width: 10,Height: 10, P1-Min: -0.5, P1-Max: 0.5, P2-Min: -0.5, P2-Max: 0.5,Rot-X: 0, Rot-Y: 90, Rot-Z: 0 > Click on the Accept button.

• Create > Body > Clip-Back > Click on the solid body and then click on the plane This operation removes half of the solid (FIGURE 50).

Clip-Back and Clip-Front operations are relative to the positive normal to theclipping plane as indicated by the displayed triad. In our case the plane wasrotated 90 degrees about the Y-axis, therefore the positive normal is directed in

FIGURE 49 Geometry construction after Boolean subtraction.



4

the positive X-direction. Clip-Back removes the solid that is located in the negativeX-direction relative to the clipping plane.

• Create > Plane > Locate > Input toggle on > X: 0, Y: 0, Z: 0, Width: 30,Height: 10, P1-Min: -0.5, P1-Max: 0.5, P2-Min: -0.5, P2-Max: 0.5, Rot-X:90, Rot-Y: 0, Rot-Z: 0 > Click on the Accept button.

• Create > Body > Clip-Front > Click on the solid body and then click on theplane > Click on the Accept button. This operation leaves one fourth of thedomain we want to mesh (FIGURE 51).

This completes the solution domain. To create the three hexahedral elements asshown in FIGURE 46, we have to define the nodes first. Set the view to be isomet-ric. Make sure the Display Curves icon in the Display Objects Toolbar is on and the

FIGURE 50 Geometry construction after first Boolean clipping.

planeClipping

FIGURE 51 Geometry construction after second Boolean clipping.



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Display Surfaces icon is off. In the StressCheck Input dialog window select theMesh tab and the following options:

Mesh tab > Create > Node > Point > Click on the Accept button. A node willbe created at every point in the model. A total of 10 nodes should be createdusing this method. (FIGURE 52)

.

• Create > Node > Mid-Offset. Move the cursor to the display area andclick on two nodes on one circle and then on the two nodes of the othercircle.

• Create > Node > Locate > Input toggle on > X:5.0, Y: 0.0, Z: th > Clickon the Accept button. A node will be created at the front side of themodel.

• Create > Node > Projection. Move the cursor to the display area, clickfirst on the last node created and then, while holding the Control andShift keys, click on one of the lines closest to the node, then click onthe Accept button. Repeat two more times for a total of 3 nodes.

After the last operation, 16 nodes have been defined as shown in FIGURE 53.Now, 3 hexahedral elements should be created.

• Create > Hexahedron > Selection. Move the cursor to the display area and click on 8 nodes that define the element in any order or draw a box around 8 nodes in a single operation as shown in FIGURE 55.

FIGURE 52 Mesh construction: Nodes at points.

Display Surfaces Off

Display Curves On



4

To enter material properties, load, and constraints follow the same steps indicatedabove for the model created using the copy operation.

FIGURE 53 Mesh construction: Additional nodes.

Node at (5,0,th)

Nodes by projection

Nodes by Mid-Offset

FIGURE 55 Mesh construction: Element creation by selection 8 nodes.



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Index

AAction 30Analysis

linear 57Attributes 24Average 70

BBatch file

read 18write 19

Boolean operationsclip-back 78clip-front 79subtract 78

Browser 35

CCenter of Rotation 31Class 30Class menu 21Colors 30Comments 37constraint 55Constraints

assign 55display 27extrusion 65symmetry 55

Cursors 30

DDatabase

erase 20new 18

Design Study 43Display

attributes 27colors 28controls 28material summary 28model summary 28objects 30options 27options toolbar 25

Display Menu

attributes 27colors 29material summary 28model summary 28move 25objects 26selection 27view controls 26

Display Object 24

EEdit 23Edit Menu

handbook 21input 20parameters 21redo 20results 21solution 21undo 20

Element 50Error

estimator 59Execute

linear analysis 57Exit 20Export 19Extrusion 65

FFile

exit 20export 19import 18menu 18new 18open 18save 18

Functions 60

GGeometry

create 30, 48, 72delete 30edit 30select 30

HHandbook

browser 35editor 44framework 33index 34interface 16library 15

IIcon

compute solution 13create model 12handbook library 15view results 13

Input dialog window 12Interface conventions 29

LLine

types 30Load

assign 53dialog box 53display 27traction 54types 54

MMaterial properties

entry 52summary 28

Menu Bar 9Mesh

check 51create 51design 50

Method 30Min/Max computation 62Model Browser 35Model Icon 28Model Info 11Model Summary 28Move 25

OObject 30Objects 27Open project 45

PParameters 37Planar elasticity 45Plot 61Plotting

standard functions 61Post-processing 41P-version 3

QQuality assessment 8, 58

RRedo 20Reset 25Results dialog window 13

SScale 43Solution dialog window 13Solution ID’s

specification 57

TThickness

assign 51display 27

Toolbarattributes 24display objects 24display options 25edit 23main 9view 9

Tutorial 45

UUndo 20Update 39

VView Menu

attributes toolbar 24display object toolbar 24display options toolbar 25edit toolbar 23views toolbar 22

Views Toolbar 22

WWindow

dialog 10input 12model 10

stresscheck - home | esrd · 2021. 3. 17. · planar elasticity problem 43 extrusion problem 62 ......

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