三维DIC在铸铁拉伸试验中的应变测量精度研究

Study on Strain Measurement Accuracy in Tensile Test for Cast Iron Using Three-Dimensional Digital Image Correlation

基于三维数字图像相关方法(3D-DIC)的拉伸实验研究了铸铁的拉伸力学性能,分别得到了应力—应变曲线、弹性模量、抗拉强度、延伸率等拉伸力学性能参数.将3D-DIC应力—应变的测试结果与目前实验中使用广泛的接触式引伸计方法的实验结果作了对比,得到两者的应力—应变曲线基本重合,弹性模量相差不超过4%.此外,还对3D-DIC和机械引伸计的应变绝对误差和相对误差作了详细比较,实验表明3D-DIC在铸铁拉伸力学性能测试中具有足够的应变测量精度,完全可以取代传统引伸计成为一种有效的非接触式变形测量手段.

Based on uniaxial tensile test and three-dimensional digital image correlation （3D-DIC） technique, tensile mechanical properties of cast iron were studied and tensile mechanical performance parameters such as stress-strain curves, elastic modulus, tensile strength and elongation percentage produced by maximum force were obtained respectively. The results obtained using 3D-DIC were compared with that determined using contact extensometer method which is utilized widely in current experiments. Experimental results indicate that stress-strain curves are in good agreement with each other and the error of elastic modulus is less than 4%. In addition, absolute strain difference and relative difference between 3D-DIC and mechanical extensometer were compared and analyzed in detail, which indicates that 3D-DIC has enough strain measurement accuracy in tensile tests for mechanical properties of cast iron and it can completely replace the conventional contact extensometer method, becoming an effective means of non-contact deformation measurement.