unique software solution for accurate in-situ load...

Unique software solution for accurate in-situ load measurement

Overview Introductionfe-safe® is the technical leader in the design anddevelopment of durability analysis software and isdedicated to meeting its customers' most demandingapplications. It develops and sells fe-safe®, the leadingfatigue analysis software suite for Finite Element models.

As a privately owned company, its independence and focusenables Safe Technology to continually bring the mostaccurate and advanced fatigue analysis technology toreal-world, industrial applications.

Wolf Star Technologies is committed to helping its clientsrealise their product development goals by leveraging thestrengths of Finite Element Analysis (FEA). Wolf StarTechnologies offers consulting services to assist withdelivering decision-ready solutions for clients' projects.

Wolf Star Technologies offers unique software solutions forin-situ load management that seamlessly integrate intothe FEA environment, to better utilise customers' FEAinvestment. Wolf Star Technologies’ software tools enableanalysis-driven product development by focusing on testcorrelation, quasi-statics and linear dynamics.

Safe Technology has partnered with Wolf Star Technologiesto bring to market fe-safe/True-Load™, a unique solutionto provide strain correlated FEA load calculations.

fe-safe/True-Load™ turns any structureinto an n-dimensional load transducer

by coupling FEA analysis withexperimental strain measurement.

Loading measurements form the biggest source of error forperforming any fatigue calculation. Until now, loading hasremained the hardest measurement to provide. Traditional loadmeasurement, which typically is not aligned with the FEA model,wastes time and money when performing design anddevelopment iteration cycles.

Strain measurement is a common approach to understandingenvironmental loading on structures but this is a time-consumingprocess and when comparing the strain measurements to FEAmodels, there is often discrepancy. This leads to poor designdecisions for future product iterations which ultimately leadsto wasted time and money in product development.

The core reason for inaccuracies is that the number of variablesinvolved are impossible to handle manually. Each point in timerequires a unique set of loadings in order to correlate to themeasured strain values. The sheer magnitude of the numberof gauges and the quantity of data makes this impossible toperform manually.

fe-safe/True-Load™ provides the solution. The software willdetermine optimal gauge placement based on the FEA model.Once strains are collected at these optimal gauge locations, thestrain data is read into the software to calculate load timehistories that will typically match the measured strain to within2% at every point in time.

With fe-safe/True-Load™ interrogating any point in the modelfor strain, stress or displacement is easy and interactive. Typically ittakes a few minutes to determine the strain gauge placement anda few minutes to back- calculate the loading profiles. Oncefe-safe/True-Load™ has calculated loading profiles, a scale-and-combine fatigue event is defined. The user only has to assignfatigue materials to the regions of interest in the FEA model.


Loading events can be the biggest unknown for calculating fatigue damage.fe-safe/True-Load™ provides the solution

Case Study: Headlamp Equivalent Loading• Headlamp subjected to modal dynamic base excitation• Quasi-Static G-Loading used to place gauges• Strain measured from dynamic event• Equivalent quasi-static load histories generated via fe-safe/True-Load™• Strain correlation within 2%

Summary Technology overview


fe-safe/True-Load™ calculates loading histories with remarkable accuracy

Case Study: Bushing Loads • Non-Linear analysis used to generate non-linear mount loading• Bracket turned into load transducer via fe-safe/True-Load™• Equivalent loading constructed using strains from non-linear analysis

Key benefits

• Turns complex components into multi-channel load cells• Calculates loading histories from measured strain histories• Optimises the location of strain gauge placement based

on FEA unit loads• Generates loading histories that can be used for testing

and for fatigue from FEA• Provides unprecedented Strain Correlation

on all strain channels• Generates strain correlated load histories• Generates strain correlated FEA load histories• Provides sound, methodical, math-based strain

gauge placement • Pre-conditions the FEA model for correlation

to strain data

• Reduces test and analysis time correlating loads• Reduces test costs (transducers, testing, labour)• Increases the user’s knowledge of the true loading

on the structure• Reduces time and error in setting up scale-and-combine

fatigue analysis• Provides the foundation for accurate fatigue calculation

Saves money byeliminating iteration cycles

fe-safe/True-Load™ leverages the fact that most structures havespatial regimes which behave linearly throughout theenvironmental loading regime. This means the forces applied tothe structure are proportional to the strain and displacement ofthe linear portions of the structure. This can be represented bythe graphical relationship:

This linear relationship can be written mathematically as:

The first equation above is simply Hooke's law. If Hooke's lawholds for the structure in question, then the second corollaryequation must also hold true. Through application of standardlinear algebra manipulations, the unknown correlation matrix, [C]can be found from the relationship:

The strain matrix [ ], and thus the correlation matrix [C], canbe found from strain results retrieved from FEA model unit loadcases. Once the correlation matrix has been found, theenvironmental loading is then calculated from the strain and loadcorrelation equation.

Initial strain gauge placement is chosen by searching through themodel to provide the most stable representation of the inverseof the strain matrix projection:

The objective is to maximise the determinant of the strain matrixprojection. The search is performed using an exclusive D-optimalsearch algorithm. This method leverages the linear behaviour ofthe structure, the full field stress/strain relationship of the FEAmodel and experimental strain measurement to calculateenvironmental loading without any structural modification. Froma handful of strain gauges, full field results are able to becalculated for every point in time of the environmental loading.

Process overview Key featuresThe fe-safe/True-Load™ process begins with the FEAanalyst applying unit load cases to the FEA model. Theseunit load cases represent points of load entry or uniquemodes for the structure. This is a departure fromtraditional FEA loading which typically will look at theentire loading profile in a single solution set.

Once the unit load cases are applied and strain results aresolved, the fe-safe/True-Load™ software is used todetermine the gauge placement and save the correlationmatrix. The test engineer will then place physical straingauges as indicated by fe-safe/True-Load™. Havingcollected the strain data, the test engineer will then passthe strain data back to the analyst to calculate the loadingusing True-Load/Post-Test. The analyst can now use theseloads to refine the design or send them to fe-safe® forfatigue calculations.

• Provides accurate in-situ load measurement• Generates strain correlated FEA loading• Generates pre-conditioned FEA models for testing• Enables scale-and-combine loading definition through

multi-channel data file and the loading definitionfile (LDF)

• Optimises the locations of strain gauges• Leverages the mathematics embedded in the

FEA model, thereby achieving remarkable accuracy• Saves time and money in testing• Provides hardware-in-the-loop technology

for load measurement• Includes a natural, intuitive user interface• Integrates with Abaqus CAE• Exports data quickly and easily to fe-safe®

• Eliminates iterations by understandingthe true loading environment


fe-safe/True-Load™ optimises the locations of strain gauges

Case Study: ”Hangman” Fixture• Simplified structure for correlation study• Subjected to proving ground loading mounted to rear of vehicle• Forces measured independently through large mass acceleration• fe-safe/True-Load™ measurement via strain gauges mount on structure• Force correlation within 2%• Strain correlation within 0.1%

FEA Modelsfe-safe/True-Load™ leverages the linear elastic behaviour

of the FEA model. The FEA model requires strain results

to be used to develop the correlation matrix.

All element types are permitted in the FEA model. However,

gauge placement is only allowed on thin shell or membrane

elements. If the model contains solid elements in the area

of interest, a surface coating of shell elements will need

to be applied.

Any load type may be considered: point load, pressure load,

acceleration load, thermal load, enforced displacement and

mode shapes. The only requirement is that the FEA analysis

produces strain on the elements.

Currently, fe-safe/True-Load™ is enabled via an Abaqus

CAE plug-in.

A multi-platform version of fe-safe/True-Load™ is in

development.

InputTrue-Load/Pre-Test: FEA Strain datasets.

True-Load/Post-Test: Time histories of measured strain data.

OutputTrue-Load/Pre-Test: Strain gauge placement, loading

correlation matrix, HTML report.

True-Load/Post-Test: Loading functions, Scale-and-combine

loading definition, fe-safe® configuration macro, quasi-static

event file, experimental / FEA strain correlation plots at

gauges, HTML report.

Quasi-static DomainQuasi-static analysis involves the superposition of static load

cases to simulate time varying dynamic loads. Static FEA

solves are used to provide the load correlation matrices. The

measured strain data is then projected onto a load correlation

matrix to provide the time varying quasi-static loads.

Flexible Body DomainWith a flexible body domain, modes shapes are used

to develop the strain correlation matrices. Similar to the

quasi-static approach, the measured strain will be projected

onto the correlation matrices to determine modal participation

functions. These modal participation functions can then

be used to extract operating deflection shapes complete

with full field stress and strain data.

Craig-Bampton ConnectionsBy applying the quasi-static approach to connection DOF, and

then combining these results with the structural mode shapes,

fe-safe/True-Load™ will result in an experimentally derived

Craig-Bampton dynamic response of the structure.

Scale-and-combine loading for fe-safe®fe-safe/True-Load™ creates the multi-channel data file, loading

definition file and a configuration macro. The user only needs

to run the macro and then assign fatigue materials in fe-safe®.

fe-safe/True-Load™ includes the utility True-QSE which is an

interactive scale-and-combine tool which will output time

domain displacement, velocity, acceleration, stress and strain

data for any node or element in the model based on the

loading from fe-safe/True-Load™. Full field operating deflection

shapes may also be generated from True-QSE.

Capabilities overview


This is not a complete list of features in fe-safe/True-Load™. To discuss your particular requirements, please contact your local fe-safe/True-Load™ representative.

All t

rade

mar

ks a

re a

ckno

wle

dged

. fe-

safe

® , fe

-saf

e/Tr

ue-L

oad™

and

the

Safe

Tec

hnol

ogy

logo

are

tra

dem

arks

of

Safe

Tec

hnol

ogy

Lim

ited.

With

tha

nks

to T

rium

ph M

otor

cycl

es L

imite

d fo

r im

ages

sup

plie

d.

Dassault Systèmes, the 3DEXPERIENCE Company, provides business and people with virtual universes to imagine sustainable innovations. Its world-leading solutions transform the way products are designed, produced, and supported. Dassault Systèmes’ collaborative solutions

.dlrow laer eht evorpmi ot dlrow lautriv eht rof seitilibissop gnidnapxe ,noitavonni laicos retsofThe group brings value to over 150,000 customers of all sizes, in all industries, in more than 80 countries. For more information, visit www.3ds.com.

CATIA, SOLIDWORKS, SIMULIA, DELMIA, ENOVIA, GEOVIA, EXALEAD, NETVIBES, 3DSWYM, 3DVIA are registered trademarks of Dassault Systèmes or its subsidiaries in the US and/or other countries.

Delivering Best-in-Class Products

Europe/Middle East/Africa Dassault Systèmes 10, rue Marcel Dassault CS 40501 78946 Vélizy-Villacoublay Cedex France

Americas Dassault Systèmes 175 Wyman Street Waltham, Massachusetts 02451-1223 USA

Asia-Pacific Dassault Systèmes Pier City Shibaura Bldg 10F 3-18-1 Kaigan, Minato-Ku Tokyo 108-002 Japan

Virtual Product Design

3D for Professionals

Realistic Simulation Dashboard Intelligence

Social Innovation

Online 3D Lifelike Experiences

Virtual Production

Visit us at 3DS.COM/SIMULIA

Global Collaborative Lifecycle Management

Information Intelligence

Virtual Planet

Desi

gn b

y bl

uest

raw

berr

yele

phan

t.co.

uk ©

2013

. All

right

s re

serv

ed D

assa

ult

Syst

èmes

201

3.

unique software solution for accurate in-situ load...

Documents