温度及应变速率对7075铝合金临界损伤因子的影响

Effect of different temperatures and strain rates on the critical damage factor of 7075 aluminum alloy

解析Cockroft-Lathem韧性累积损伤计算原理,提出'基于损伤敏感率演变规律求解临界损伤因子'的方法。完成不同温度和应变速率条件下多组7075铝合金试样的热物理模拟压缩试验,以采集到的真实应力应变数据作为数值计算损伤值的底层材料模型,以最大损伤值出现的镦粗鼓外缘部位为研究区域,获得'损伤敏感率在变形初期快速下降至后期逐步趋于0'的损伤软化规律,而损伤软化现象对应变速率较为敏感。以损伤敏感率为0作为临界损伤因子出现的时机,获得7075铝合金在温度573～723K、应变速率0.01～10s-1下的临界损伤因子分布规律。结果显示其不是常数,而是为在0.255～0.453范围内变化的变量,其在高的温度下对应变速率更为敏感,在高的应变速率下对温度更为敏感。

The computation principle of Cockroft-Lathem ductile cumulative damage is analyzed.A method to solve the critical damage factor based on the evolution rules of damage sensitive rate is brought forward.Several series of billet samples are compressed on heat physical simulation machine under different deformation temperatures and strain rates,and then the collected true stress-strain data are used to calculate the performance of computations.As the outer edge of upsetting drum where the maximum damage value appears is concerned,a typical damage softening rule is obtained and described as the damage sensitive rate decreases rapidly at the initial deformation,then gradually tends to 0.In further,damage softening is more sensitive to strain rate than temperature.A principle that critical damage factor arises when damage sensitive rate decreases to 0 is assumed,then the distribution of critical damage factor under temperature 573~723 K and strain rate 0.01~10 s-1 is obtained.The results show that the critical damage factor of 7075 aluminum alloy is not a constant but a change within a range of 0.255 ~ 0.453,and it is more sensitive to strain rate in high temperature and more sensitive to temperature in high strain rate.