Constitutive relations of cyclic plasticity at low temperature

本文通过对薄壁圆管试样在液氮中77 K的轴向和扭转载荷作用下的循环加载实验，研究了薄壁圆管的本构关系。的.试件材料为不锈钢SUS 304。利用循环加载的应力-应变曲线，考察了预应变施加方向和温度对循环应力-应变曲线的影响。(1)横向于循环加载的预应变在循环加载的初始阶段产生大的塑性硬化。随着循环荷载的增加，塑性硬化逐渐减小，接近于无预应变循环荷载的行为。(2)循环加载方向的预应变产生类似于循环加载累积塑性应变的塑性硬化，预应变温度对循环应力-应变曲线的影响如下。(1)在77 K下，横向于循环加载的预应变比室温下的预应变产生更大的塑性硬化。随着循环载荷的增加，预应变温度的影响逐渐减小。(2)循环加载方向的预应变在室温和77 K下产生相似的塑性硬化，预应变温度的影响不显著。

Constitutive relations of cyclic loading are experimentally investigated by subjecting thin walled tubular specimens to axial load and torsional load at 77K in liquid nitrogen. The. material of specimen is stainless steel SUS304. The effects of the direction and the temperature of giving prestrain are examined by using stress-strain curves of cyclic loading.The effects of prestraining direction on cyclic stress-strain curves are as follows.(1) The prestrain transverse to cyclic loading gives, rise to large plastic hardening at the initial stage of cyclic loading. With increase of cyclic loading, the plastic hardening decreases gradually and approaches to the behavior of cyclic loading without prestrain.(2) The prestrain of cyclic loading direction produces the plastic hardening similar to accumulated plastic strain of cyclic loading.The effects of prestraining temperature on cyclic stress-strain curves are as follows.(1) The prestrain transverse to cyclic loading at 77K gives rise to larger plastic hardening than the prestrain at room temperature. With increase of cyclic loading the effect of prestraining temperature decreases.(2) The prestrain of cyclic loading direction results in similar plastic hardening at room temperature and 77K.The effects of prestraining temperature is not remarkable.