中文摘要：

针对LY12铝合金材料的早期疲劳损伤问题,研究发展了一套可靠的超声非线性系数测量实验系统,利用该系统离线测量了LY12铝合金疲劳试件的超声非线性系数。实验结果表明,在未达到60%左右疲劳寿命时,超声非线性系数对LY12铝合金材料的早期疲劳损伤有很高的灵敏度。同时利用浸蚀法观察了LY12硬铝疲劳试件的位错密度变化,超声非线性系数和位错密度随疲劳周次的变化近似一致,表明超声非线性效应与晶体中的位错有关,超声非线性系数可以表征晶体材料内部位错的变化,进而预测金属材料的疲劳寿命。

英文摘要：

For the problem of the LY12 aluminum early fatigue damage,a robust experimental procedure was researched.Using this system,the ultrasonic nonlinearity parameters of LY12 aluminum fatigue samples were measured.The experimental results show that there is a significant increase in β linked to aluminum fatigue damage,before the fatigue life of 60%.Meanwhile,dislocation density change of LY12 aluminum fatigue samples is observed using erosion method,and the changes of nonlinearity parameter and dislocation density with fatigue cycles are consistent.Macro-mechanics,nonlinear ultrasonic testing and microscopic observation results show that ultrasonic nonlinearity parameters as the bridge between micro and macro can characterize the early fatigue damage,and predict fatigue life of metallic material.