Proportional limit, elastic limit, yield stress and ultimate stress of a ductile material are 150MPa, 180MPa, 200MPa and 300MPa respectively. if the factor of safety is 2, the allowable stress of this material is ( )
A、100MPa;
B、150MPa;
C、75MPa;
D、90MPa
发布时间：2025-07-24 20:15:57
