The aluminum test specimen shown is subjected to two equal and opposite centric axial forces of magnitude P.
(a) Knowing that E = 70 GPa and σall = 200 MPa, determine the maximum allowable value of P and the corresponding total elongation of the specimen.
(b) Solve part a, assuming that the specimen has been replaced by an aluminum bar of the same length and a uniform 60 X 15-mm rectangular cross section.