Lecture 3: SolidWorks 2 - Testing

Professor Erik Cheever

Course web page: http://www.swarthmore.edu/NatSci/echeeve1/Class/e5/E5Index.html

Remember… Wizards available (Hicks 211/213) from 8:30-10:00

Tuesdays and 8:00-10:00 Wednesdays specifically for E5.

Thursday 9/17

SolidWorks part from Lab 2 is due.

Ball drop wiki is due

Thursday 9/24 – “Bridge Design” is due.

Shop Class sign-up (Shop class starts 9/18). Sign up in department office.

Plan to attend a study session sometime – just to see what they are like… See http://www.swarthmore.edu/wizards.xml for schedule.

…or just drop by to say “hi” to Ann in Hicks 219.

The big picture… This week

Videos from last week (how parts are made)

Class - Testing parts with Solidworks

Lab – Iterative design for optimization

Next week – making assemblies – several parts together.

Subsequent weeks – learning MatLab, a useful programming language for a wide variety of programming problems

Making parts (from last week)

Subtractive Prototyping (Start with stock, and remove)

Manual vs CNC (Computer Numerically Controlled)

Manual Milling machine: Cutter spinshttp://www.youtube.com/watch?v=2zVp7x8wDtM

CNC Milling machine:

3 axis (smaller):http://www.youtube.com/watch?v=LdrFHbUUUKE

3 axis (bigger):http://video.google.com/videoplay?docid=-1883546966521949694&hl=en#

4 axis:http://www.directindustry.com/prod/charlyrobot/compact-3-axis-cnc-vertical-milling-machine-7954-352067.html

5 axis:http://www.youtube.com/watch?v=RSvgvNyHEYU

CNC Lathe: stock material spinshttp://www.youtube.com/watch?v=ghF7njMgZgs

Testing parts with SolidWorks

SolidWorks uses Finite Element Method (FEM) Analysis

It is hard to calculate forces on shapes that are complex, so…

split the object up into thousands of smaller objects of simple shape,

assume everything behaves linearly,

get a computer to solve.

This technique is also used in computer simulations of heat transfer, fluid dynamics, electronics…

The FEM Mesh

From http://www.algor.com/news_pub/cust_app/monkey_skull/default.asp

Variable Mesh Sizes

. . . SolidWorks demo . . .

FEM Mesh fro fluid flow around pipes.

From http://www2.imperial.ac.uk/ssherw/vortexflows/people/Tim_Kendon/fig/mesh_Vr8.89_B1.53_fsf_Re100_LES.png

Corners concentrate stress (1)

http://varifrank.com/images/314028020_29d914723f_o.jpg

The Early De Havilland Comet (with square windows) – the

first commercial jet liner.

The windows were square to differentiate them from a ship’s

porthole.

Corners concentrate stress (2)

http://www.owlnet.rice.edu/~msci301/CometCrash.jpg

After Several flights the planes had tendency for explosive decompression

Corners concentrate stress (3)

http://www.geocities.com/CapeCanaveral/Lab/8803/p5cyp07.jpg

Round windows!

http://www.plane-spotter.com/ScanAvPhoto/Dan-AirLondon_Comet4.jpg

A later model Comet (with round windows)

. . . SolidWorks Demo . . .

The Hyatt Regency Kansas CityBasic Walkway Design

• Walkway on 2nd, 3rd and 4th floors cross the atrium.

• 3rd and 4th floor walkways were suspended from roof;2nd floor walkway suspended from 4th floor walkway.

Images from: http://azurebrooke.com/deviation.htm

As originally designed As built

Constraints – design 1

Loads – design 1

Stress – design 1

Maximum Stress is 4.16*107

Stress (close-up) – design 1

Stress (extreme close-up) – design 1

Note triangular regions due to computer analysis

Deflections – design 1

Maximum Deflection is 5.34*10-3

Loads – design 2

Simplified Analysis of designs

Image from: http://azurebrooke.com/deviation.htm

Stresses – design 2

Maximum Stress is 8.34*107

About twice as much as before (4.16*107)

Stresses (close-up) – design 2

Deflections – design 2

Maximum Deflection is 7.17*10-3

About 50% more than before (5.34*10-3)

Fourth floor walkway beam

Image from: http://ethics.tamu.edu/ethics/hyatt/hyatt2.htm

Fourth floor beam (close-up)

Image from: http://ethics.tamu.edu/ethics/hyatt/hyatt2.htm

Third Floor Beam

Image from: http://ethics.tamu.edu/ethics/hyatt/hyatt2.htm

Note slight buckling due

to insufficient design

An Engineer's Responsibility Engineers have a tremendous responsibility to insure

the safety, health, and welfare of the public. The public well-being can be maintained only if

engineers follow all codes and standards, and uphold their professional obligations.

Safety during the construction phase of projects will help to insure the ultimate safety of the completed structure.

Adapted from: http://www.mech.utah.edu/ergo/pages/Educational/safety_modules/KC/

Facts About Case

As originally designed, the walkways were barely capable of holding up the expected load, and would have failed to meet Kansas City building requirements.

The fabricator did not want to thread entire rod to install the washer and the nut.

The fabricator claimed to receive phone approval for engineering change.

The engineering firm declared they had not received the phone call, but plans were altered to reflect change.

Adapted from: http://www.mech.utah.edu/ergo/pages/Educational/safety_modules/KC/

Who was responsible? Original design was marginal.

A lack of communication between the designer and fabricator is one contributor to the failure of walkways.

The engineering firm did receive revised drawings during construction and stamped them with their engineering review seal, authorizing construction.

The revised design was significantly less capable of holding up the required forces, and was not designed in accordance with the Kansas City building code.

Adapted from: http://www.mech.utah.edu/ergo/pages/Educational/safety_modules/KC/

Consequences

114 people were killed and over 200 injured.

Engineers found guilty of gross negligence, misconduct, and unprofessional conduct in the practice of engineering.

Many principals lost engineering licenses.

Expensive legal suits settled out of court.

Several firms went bankrupt.

Adapted from: http://www.mech.utah.edu/ergo/pages/Educational/safety_modules/KC/