Department of Mechanical & Aerospace Engineering

CAD Apps for Core Courses in AE and ME Curricula

The Eiffel Challenge 1/14

L. M. Silverberg, Director of Undergraduate Programs Mechanical & Aerospace Engineering

J. Eischen, Chair of ME Course & Curriculum CommitteeMechanical & Aerospace Engineering

L. Battestilli, Instructor of Introduction to MATLABTeaching Assistant Professor, Computer Science

Students:Will Morrow, CS, MS Candidate – CodingSean Maguire, ME, MS Candidate – Design & AssessmentKonner White, ME, MS Candidate – Design & Assessment

Point of Contact:L. M. Silverberg at lmsilver@ncsu.edu(919)515 5665

Department of Mechanical & Aerospace Engineering

CAD Apps: The Need for Design and Exploration in Early Engineering AE and ME Curricula

• The need to increase design and exploration ranks high in student exit surveys.

• This need originates from the central role of design and exploration in education and the difficulties that educators face in providing design and exploration experiences.

• Whereas analysis tends to be about finding one correct solution, design and exploration tend to be about iterating parameters until a satisfactory solution is found.

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Department of Mechanical & Aerospace Engineering

CAD Apps: Course-Specific General-Purpose Tools are Developed for Design and Exploration

• The offering of design problems in a classroom setting is greatly enhanced by using tools that allow the student to rapidly find solutions to complex problems.

• Computer tools available to students today are largely general-purpose; not customized to specific courses.

• This grant responds to the need for course-specific general-purpose tools for design and exploration for the early engineering years.

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Department of Mechanical & Aerospace Engineering

CAD Apps: Core Courses in AE and ME Curricula

Topic AreaAerospace

EngineeringMechanical Engineering

Planar Trusses Engineering Statics Engineering Statics

Planar Mechanisms Engineering Dynamics Engineering Dynamics

Planar Frames Solid Mechanics Solid Mechanics

Planar Heat Conduction Heat Transfer

Planar Mass-Spring-Damper Systems

Vibrations Vibrations

Topic Area Computer Science

Variety Introduction to MATLAB

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Department of Mechanical & Aerospace Engineering

Will Morrow, Comp. Sci MS Candidate

Sean Maguire, ME, MS Candidate

Konner White,BS in ME, AE

GUI Design & AssessmentMATLAB GUI Software Development

MATLABBackend

Code

• Weekly Meetings Students & Faculty• Testing with Undergraduate/Graduate Volunteers

CAD Apps: The Student Team

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Department of Mechanical & Aerospace Engineering

CAD Apps: Backend Code• Students use backend code specifically developed for the apps (truss, frame,

mechanism, heat conduction, vibration).

• Elements are one-dimensional.

• Internally, nodes are unconstrained; constraints are modelled as highly stiff.

• The process is dynamic.

• 7 state variables for each node: 2 positions, 1 angle, 1 temperature, 2 velocities, 1 angular velocity

• The static apps use default dynamic properties.

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y

xDqk0

  

Dqk

  

Dqk --

Dqk0

   

u = D – L

D

L

i

k Y

X

j

PkA VkA MkA

  

A

B

Pk (X) Vk (X)Mk (X)

  

QkA

  

Qk (x)

  

j

i

Department of Mechanical & Aerospace Engineering

• GUIDE for overall front-end design• Utilities downloaded from community (e.g. plot_arrow.m ) or

developed in-house (e.g. meshcolor.m, yieldLabelText.m)

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CAD Apps: The Front End

Main Window Editor Window

Main Window runs simulations and displays or exports results. Invokes the Editor Window.

Editor Window creates, edits, opens, and saves designs

Department of Mechanical & Aerospace Engineering

• Installation• Tutorial• The Eiffel

Challenge• Results & Winning Design

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CAD Apps: The Truss App

Department of Mechanical & Aerospace Engineering

MATLAB Installed (2012b or higher) URL: http://www.mae.ncsu.edu/academics/mae-course-websites.phpAt the bottom of the webpage click: Matlab App

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CAD Apps: Installation

Double click on the file CADApp_Truss.mlappinstall

Department of Mechanical & Aerospace Engineering

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CAD Apps: Tutorial

Note: yE=16.32 mm (nonlinear)

Department of Mechanical & Aerospace Engineering

Return to Editor

Move a Node• Using the Mouse • Using Nodal Properties Table

Change the Length of a Member• Using the Mouse Node Deletion • Using the Mouse Middle Button

Importing and Exporting Schematic Files • Using the Import from File Button and

the Export to File Button

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CAD Apps: Tutorial – Additional Features

Department of Mechanical & Aerospace Engineering

Eiffel said in 1887 (Le Temps (Paris), February 14):

“Now to what phenomenon did I give primary concern in designing the Tower? It was wind resistance. Well then! I hold that the curvature of the monument's four outer edges, which is as mathematical calculation dictated it should be … will give a great impression of strength and beauty, for it will reveal to the eyes of the observer the boldness of the design as a whole.”

As proof of the tower's effectiveness in wind resistance, it sways only 6–7 cm (2–3 in) in the wind.

____________

Named after the engineer Gustave Eiffel, whose company designed and built the tower.

Erected in 1889 as the entrance arch to the 1889 World’s Fair

The tallest building in Paris; most-visited paid monument in the world; 6.98 million people ascended it in 2011. The tower received its 250 millionth visitor in 2010.

324 meters (1,063 ft) tall, about the same height as an 81-story building.

Has 3 levels for visitors, with restaurants on the 1st and 2nd. From ground level to the 1st level is over 300 steps, same from the 1st to the 2nd. There are stairs to the 3rd level but these are usually closed to the public and it is generally only accessible by lift.

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CAD Apps: The Eiffel Tower Challenge (Wikipedia)

Department of Mechanical & Aerospace Engineering

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1st platform

2nd platform

Top platform

Challenge: Find the widths of the 1st and 2nd platforms subject to the constraint that the total width L1+L2= 339ft in order to minimize the lateral deflection at the top platform

Hint: Begin the iterative design process with the baseline configuration in file JWEEiffel.schm.

The Eiffel Tower

Challenge

Department of Mechanical & Aerospace Engineering

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Minimum deflection is 0.207 ft = 2.5 in at the top when L1 ≈ 200 ft and L2 ≈139 ft.

Actual Eiffel tower dimensions areL1 = 216 ft and L2 = 123 ft.

Given the simplicity of our 2D truss model, the insight than can be achieved is remarkable

CAD Apps: The Eiffel Tower Solution (Top Secret)

150 160 170 180 190 200 210 220 230 2400.1

0.2

0.3

Eiffel Tower Stiffness Optimization

1st Platform Width, L1, ft

Top

PLatf

orm

Defl

ectio

n, d

, ft