Question

7. The yield stress of a tension specimen machined from a 2-m wide by 0.6-cm thick copper sheet is 145 MPa. The sheet is rolled further with an applied tensile force in the plane of the sheet of 0.22 MN. What roll pressure is needed to just cause yielding? You may ignore friction between the metal and the rolls. For rolling, the deformation occurs by plane-strain in which there is no increase in the width of the sheet. You may also assume that for plastic flow the Poisson's ratio v= 0.5, and the copper obeys von Mises criterion. (Ans. -94 MPa) (20%)

Answer 1

iven Width of pecimen Thictness af sheet t o 6 em yield strength Ys l4sMPa. Tensile force acting m sheet, Fr 0-22 MN Poisson's ratio of copper, 20 33 Tensile strecs Fr aT o-22X10 N o Sxo 6X to m 73-3x 10 Pa 73.3 MPa The stress developed by rollers ar: 9y- 9T e t4S-13-33 71-67Mpa strain in longitudinal axis due to Strecs rollefs by lomgi tuclinal = TI 67 lateral strain Sateral Simgi tudi nal

Suteral ux Slongitudinal o 33 xS ax lo 141x 1o lateral strain developed due to pressuve by rollers m the sheet applied E : ateral Slateral latev 120x14u7x io 23.36 MPa