Someone start a cht im bored (im a freshman)

Coiled springs ought to be very strong and stiff. si3n4 is a strong, stiff material. would you select this material for a spring? explain.

The thermal expansion or contraction of a given metal is a function of the f a)-density b)-initial temperature c)- temperature difference d)- linear coefficient of thermal expansion e)- final temperature f)- original length

Draw the engineering stress-strain curve for (a) bcc; (b) fcc metals and mark important points.