泡沫金属中高速拉伸的试验数据处理与材料力学性能测量

Data processing and mechanical properties measurement of foamed metal in medium to high-speed tensile test

泡沫金属中高应变率(0.02~100s-1)的拉伸试验多由伺服液压控制的高速拉伸试验机来完成,然而,对伺服液压高速试验机进行数据处理时,存在两个问题使得测量结果不可靠:一是荷载较小,使得拉伸荷载信号与若干噪声信号量级相同,难以确定拉伸的起始点;二是夹具滑移等现象使得测量位移数值明显大于试件变形产生的真实位移。为了克服荷载和位移在测量方面的困难,本文结合高速摄像机测量及数字图像相关(Digital Image Correlation,DIC)技术,分析了泡沫铝拉伸行为,提出用DIC技术测量得到的加载端加速度峰值来确定材料破坏应变的观点,从而可以综合DIC技术获得的加速度数据和荷载数据,确定荷载的起始点,有效地得到泡沫金属拉伸应力应变关系以及弹性模量和破坏强度等参数。

The tensile test of foamed metal with medium to high strain rate(0.02~100 s-1)is mostly done by hydraulic servo controlled high-speed testing machine.There are two problems that make the test results unreliable when processing data.On one hand,it is difficult to determine the start time of stretching,because the tensile load is small so that the tensile signals can be disturbed by noise signals with the same order of magnitude.On the other hand,the measured displacement value is significantly larger than the actual displacement due to the slip of the fixture.By combining a high-speed video camera with the digital image correlation(DIC)technology,the tensile behavior of foamed aluminum is successfully analyzed,and the method that can be used to determine the damage strain based on the peak acceleration velocity of DIC measurement is proposed.Meanwhile,the start time of tensile is obtained using the load-time curve of equipment and the acceleration-time curve of DIC.Furthermore,the tensile stress-strain relationship,elastic modulus and failure strain of foamed metal are obtained effectively.