时效蠕变与时效应力松弛行为转换关系

Research on conversion relationship between aging creep and aging stress relaxation

针对目前采用的蠕变与应力松弛转换方法存在的问题,即一方面没有考虑时效析出过程对二者的影响,另一方面存在转换精度较低、人为因素影响大等缺陷,以7075铝合金作为试验材料,分别开展对时效热处理温度为140℃,多组不同初应力下的时效应力松弛与时效蠕变试验。基于蠕变和应力松弛特性,利用作图与数值分析相结合的方法,实现时效应力松弛曲线向时效蠕变曲线稳态蠕变阶段的转换,得到了材料的稳态蠕变速率;通过拟合转换曲线与试验曲线,分别得到两组曲线在Norton方程中的材料常数K和n。结果发现,由时效松弛试验转换得到的蠕变数据与时效蠕变试验数据吻合较好,表明这一转换方法可行,并进一步验证了时效应力松弛与时效蠕变两者间的内在联系。

Some inherent shortcomings, such as the influence of the aging precipitation heat treatment on creep and stress relaxa- tion process, the low conversion accuracy and human factors etc, exist in traditional conversion method from creep results to stress relaxation ones. Stress relaxation aging tests and creep aging tests of 7075 aluminum alloy under different initial stresses were carried out. Based on relationship between creep and stress relaxation, the conversion from the aging stress relaxation curves to the steady-state stage of aging creep curves were achieved by using numerical analysis and plotting method, the steady-state creep strain rates under different stress levels were also obtained. At the same time, through fitting the conversion curves and the test curves, the material constant K and n in Norton equations were deduced respectively. Good agreement between the creep data converted from the stress relaxation test data and the conventional creep test data was reached. Thus the feasibility of this conver sion method and the intrinsic relationship of creep and stress relaxation are verified.