Question { 23897 }

WHAT YOU MEAN BY PROOF STRESS?

Answer

when a material such as Aluminium doesn't have an obvious
yield point and yet undergoes large strain after the
proportional limit is exceeded an arbitrary yield stress may
be determined by Offset method .A line parallel to initial
part is drawn which is offset by some standard amount of
strain such as 0.2 % ,the inersection of the offset point
defines the yield stress which is slightly above the
proportional limit and is called 'PROOF STRESS'.