Experimental investigation of plastic deformation of stainless steel for cyclic loading at low temperature

Cyclic plastic deformation of stainless steel SUS 304 is experimentally investigated at low temperature of liquid nitrogen (77 K) under various cyclic loading conditions Thin walled tubular specimens are subjected to cyclic loading under constant strain ranges. At low temperature, the material shows remarkable hardening by cyclic loading comparing with cyclic loading at room temperature. The hysteresis curves of stress-strain relations by cyclic loading are saturated by increasing the cycle numbers. The saturation tendency depends on loading direction. The saturated stress values are related with cumulative plastic strain of cyclic loading. The prestraining is given at 77 K by axial and torsional loadings, and subsequent cyclic loading under constant strain range is conducted at 77 K. The cyclic stress-strain curves are saturated by increasing cyclic numbers. At small cyclic numbers, cyclic plastic deformation depends on the prestrain direction. The directional effect of pre-strain on cyclic loading becomes small with increasing number of cycles.