Comment Engineering Lesson Stress vs Strain (Score 1) 421
I'd like to explain stress vs strain. Stress is related to force while strain is related to displacement. No matter what thin phone you are putting in your pocket the phone will conform to your body. Strength isn't the real issue. The issue is yield strain. This is how far you can bend something before it yields (permanently deforms). Aluminum while stronger (can take more force) than almost all plastics cannot bend as far without yielding. Aluminum yield strain will be around 0.4% while plastics like polycarbonate will be more like 2.6%. Effectively this means you can bend a piece of polycarbonate about 6.5 times as far as piece of aluminum before it permanently bends. Yes it will take quite a bit more force to permanently bend an aluminum phone than a plastic one but that force is small enough that it will not be the limit. The shape your body and pocket form is going to force the phone to that shape.