 Assume same material property in compression and tension Steel, aluminum, polymers  Assume no buckling or other instabilities Structuralized Local – soda can under compressive load folds up like accordion It is said…

 In order for a structure to have the least amount of material capable of carrying a load, all of the material must be in pure tension or compression

 For every amount of material that is in compression, an additional amount of material will need to be added in tension

 For every pound of material added, another pound of material must be added in order to support that extra weight (larger springs, fasteners, bearings, etc.)

 Suspension bridges

 Why are there ‘wrinkles’? Is it under a vacuum or high pressure?  Why is the bottom flat?

 Why is bottom domed inward? Is it under a vacuum or high pressure?  Why is the top a plate? Why is it thicker?

The Stalwart VS The Wexford

 Material: Sheet steel  Manufacturing Processes: Cutting Stamping Shaping Welding

 Material: Coil of Steel  Manufacturing Processes: Clip Spot weld

 A ratio Designed for Load Anticipated Experienced Load “Strength”

 Consider consequence of failure? Airplane vs. Excavator

 Depends on: Manufacturing process Materials Design Consequence

 Aircraft – 1.2 to 1.5 More analysis performed  Chair – 2 to 3, maybe upwards of 5, or 7 Might be misused more frequently

 Strength Using good, quality suppliers where you know material is repeatable and will act similar each and every time  Load Limit (as discussed last lecture)  Remove uncertainty!

1. Analytical Analysis 2. FEA Studies Most engineers stop here! 3. Field Testing Using real loads