Practice problem: true stress and strain a cylindrical specimen of a metal alloy 49.9 mm long and 9.72 mm in diameter is stressed in tension. a true stress of 376 mpa causes the specimen to plastically elongate to a length of 53.5 mm. if it is known that the strain-hardening exponent for this alloy is 0.1, calculate the true stress (in mpa) necessary to plastically elongate a specimen of this same material from a length of 49.9 mm to a length of 58.2 mm.