最新色国产精品精品视频,中文字幕日韩一区二区不卡,亚洲有码转帖,夜夜躁日日躁狠狠久久av,中国凸偷窥xxxx自由视频

The ultra-fine grain(UFG) material by Equal Channel Angular Pressing (ECAP) has attracted attention for excellent mechanical performance. The fatigue properties of UFG by ECAPSareScriticalSto wide application. The fatigue properties of ultra-fine grain high purity(HP) and low purity(LP) copper by ECAP were investigated by fatigue tests conducted in air, at symmetrical loading ratio R= -1. The cyclic stress-strain response, fatigue life and grain orientation distribution before and after fatigue were analyzed. The relationship between purity and fatigue stability of ultra-fine grain copper were discussed. The results showed that the stress-controlled fatigue life of UFG low purity copper is longer about 1.6~2.0 times than that of their coarse grain (CG) counterparts under any stress amplitude. On the other hand, the fatigue curve of UFG high purity copper shows different characteristics. TheSfatigueScyclesSto failure of UFG Hp copper is strongly dependent upon the applied stress amplitude and decrease sharply withSstress amplitude decreasing. Under lower cyclic stresses, UFG Hp copper exhibitsSlower fatigue lives. Cyclic stress-strain response of UFG Cu under stress-controlled loading change from cyclic softening to cyclic hardening with stress amplitude decreasing. The UFG low purity copper shows a relatively high cyclic strain hardening exponent, hardeningShardeningScoefficient and fatigue stability with respect to the UFG high purity copper, because the impurity hinder grain rotation and dislocation motion, decline recovery rate, and reduce grain orientation modifies.