Design Failure

1. Design Failure .

2. When Does a Design Fail? A failed design is a design process which one does not achieve the specified design goals. In this class, failure could be project cancellation due to nonperformance or no support for next year’s project

3. Conventional Types of Design Failure 1. It doesn’t work! 2. It would work, but ……..! 3. It works, but no one wants it! 4. Ooops [we’ll see what this means]

4. It doesn’t work [broad definition]! Cannot find a design solution that meets • performance, • cost, • time, • etc. specifications - even after compromises. Examples: • Fusion reactor for power - too costly, inefficient • Geared turbofan • Electric Car - performance/cost not acceptable

5. It would work, but …..! All the theory, analysis, experiment and simulation says it should work, but it doesn’t. Example: F-102 delta wing pursuit plane [We will see about this shortly]. What are your teams doing to ensure success? • Theory: _______________ • Analysis: ______________ • Experiment: ____________ • Simulation: _____________

6. It works but no one wants it! The operation was a success but the patient died. Examples: • Ford Edsel - great car, freak design • Sony Betamax - people wanted VHS • DEC PC’s - incompatible floppy Not normally an issue for your teams, but make sure you are doing what sponsor wants / needs

7. Oops! It works, but some unanticipated condition or reason causes it to fail. Examples: • Challenger Disaster - “O” rings failed below freezing temperature • Civic Center Roof - overloaded • Mianus River Bridge - mechanical failure How do you minimize your risks?

8. Design Failure Categories Catastrophic: - Serious damage to life, property; - Serious financial loss; etc. Soft: - Design goals not met but nobody hurt, - Missed opportunity Repercussions: - No UCONN support for next year - No job offers to graduates

9. Failure Mechanisms 1. Financial 2. Performance 3. Physical 4. Process 5. People Let’s now look at each of the above failure modes

10. Failure Mechanisms 1. Financial - Design cost too high - Production cost too high - Marketing unsuccessfulloss of market advantage - Inadequate service organization - Liabilities

11. Failure Mechanisms 2. Performance - Fails under certain environmental conditions. - Fails under certain operating conditions - Fails to achieve full performance specs

12. Failure Mechanisms 3. Physical - Mechanical - overstress, fracture, fatigue, over- heating, lubrication, corrosion, tolerances - Electrical - overheating, burnout, bad solder/ connector, tolerances, timing deterioration

13. Failure Mechanisms 3. Physical [cont’d] - Hardware/Software • Programming bug, timing problem, interfacing problem, too slow, not enough memory, glitches

14. Failure Mechanisms 4. Process Design is OK, but implementation a problem - Ford Taurus ignition switch - Firestone ATX tires (see later) - K.C. Hyatt (see later) 5. People Design is OK, but people can be a problem - skill level of workers (Firestone Decatur plant) - supervision of workers (PW TF30 for F111) - interest level of workers

15. Failure Mechanisms Now let’s consider some examples of design failures that are both infamous and catastrophic

16. Design Failure: Firestone ATX Tires • Who was at fault, Ford or Firestone? • ATX tires used on trucks never had failure modes • Statistically greater failure of left rear tires • Physical - shoulder pockets (for traction in mud and snow) cut too deep, leaving too little rubber on edge - shoulder pockets cut at right angles to tread increasing strain on shoulder • Process or People - Manufacturing standards at Decatur plant were inconsistent - Decatur plant used too much lubricant to keep rubber compounds from sticking together during manufacturing. Belts from this plant did not stick to each other as well as in other plants.

17. Design Failure: YF102 YF-102 • Convair [Gen. Dyn.] delta-winged fighter • Unable to fly supersonically, i.e. M < 1 • Problem diagnosed as limited by physical • principle not mechanical shortcoming • Area rule (Whitcomb, NACA) • blockage of wings causes excessive • drag rise

18. Design Failure: YF102 • Solution is to reduce flow blockage • Coke bottle fuselage design YF-102A YF-102

19. Design Failure: DC10 Cargo Door

20. Design Failure: DC10 Cargo Door • All commercial aircraft are pressurized while flying • Outside air is at low pressure compared to cabin • Inward opening door plug tight against door frame • Cargo door open outward so as not to lose interior cargo storage space • DC10 door locking procedure [baggage handler] • Pull down top-hinged door and shut it • Swing down lever on outside or door • Press and hold button operating electric motor • Put ear to fuselage until hear click, then hold for 7 more seconds till motor stops

21. Design Failure: DC10 Cargo Door • DC10 flight on June 12, 1972 from Detroit to Buffalo • DC10 baggage handler has difficulty closing door, but forces lock which gives false signal of locking • After takeoff, cargo door blows out sucking out rear galley and damaging hydraulic cables and cables to tail • Pilot deviates from accepted procedures and successfully landed plane; design changes recommended • Turkish Airlines inspection paperwork stamped with quality control approval [indicating cargo door repaired]; plane crashed in 1974 due to cargo door failure, killing 346.

22. Design Failure: K.C. Hyatt Atrium • Background • Plush hotel complex with atrium inter • connecting 3 buildings • 2 / 1 pedestrian walkways for the 2-4 / 1 • floors • At evening tea dance in atrium (1981) • with people dancing on walkways; 2-4 • floor walkways collapsed • Worst structural disaster in U.S. • History • 114 dead, 200 injured • Owner (D. Hall) settled more than 90% • of claims out of court as a sense of • duty and civic responsibility

23. Design Failure: K.C. Hyatt Atrium • Observation: failure site noted at 4th floor box beam hanger on walkway • Walkway sliding (bearing) support chosen to allow beam to expand / contract with temperature changes • Brainstorming of Failure Causes • People dancing on walkways sets up a resonance • Quality of material used in construction • Construction crew skill level • On-site contractor (as-built) modification of final design Design changes approved by architects and structural engineers As built 4th floor support takes twice the designed load

24. Design Failure: K.C. Hyatt Atrium Box Beam Hanger-as Built Box Beam Hanger-as Designed

25. Design Failure: K.C. Hyatt Atrium • Actual dead load (weight of all components) of walkway was 8% greater than designed dead load • Live load (required by K.C code was 72,000 lbs/walkway), but with 63 people on 2 walkways, actual live load = 63 (150 lbs) = 9450 lbs << 72,000 lbs • Load per 6 supports therefore was 72,000 * 2 / 6 = 24,000 Notes do not say what design should be able to take Principal manager and project manager fro m structural firm had Missouri license revoked for not calculating whether support would work.

26. Design Failure: Boston Hancock Building • Background • 60 story floor-to ceiling reflective glass panels • Glass panels started blowing out from the • beginning of construction (1973). At times • more than 1/3 of panels were out. • Cause not certain due to legal agreement of • “nondisclosure in perpetuity” • Design satisfied all governing codes • Some information gleaned from construction • grapevine • Window design • Double-glazed, doubled pane panels • Lead spacer at edges to separate panels • Design allowed for view of continuous glass

27. Design Failure: Boston Hancock Building • Brainstorming • Large wind storm correlated to panel blowout • Lateral deflection of structure due to wind effect • not verified in tests • Twisting motion (short direction) observed by • tenants (had to be damped out) • 600 tons of lead dampers added near • roof

28. Design Failure: Boston Hancock Building • Failure Cause Analysis • Glass panels were correctly installed • Thermal stress cycles induced by compression • / expansion of air between panes • Most panes cracks found in outer panes first • Lead solder overconstrains glass causing • premature fatigue • Replace all 10,344 panels with single pane glass

29. Guarding Against Failure Organizational • Management Plan • Financial Plan • Marketing Plan • Engineering

30. Guarding Against Failure Engineering • Modeling / Simulation • Design Review [CDR, Tiger Teams] • Prototyping • Testing • Maintenance Plan • Failsafe Design - Redundancy • Documentation

31. What are your teams doing to ensure success? • Theory: _______________ • Analysis: ______________ • Experiment: ____________ • Simulation: _____________

32. What are your teams doing to ensure success? Finally remember to document your failures for you and others to learn from…. But if someone has to be blamed for a project failure, blame your advisor.