数字图像相关测试技术在霍普金森杆加载实验中的应用

On the Application of Digital Image Correlation Testing Technology in Hopkinson Bar Loading

本文利用三维数字图像相关(3D-DIC)测试技术,在Hopkinson bar加载条件下测试铝合金动态拉伸力学性能以及TC4合金Ⅱ型裂纹的起裂时间和冲击载荷下的失稳扩展速度。两台高速相机保证了被测物体的三维成像,校准板技术使得所测试的应变-时间历程定量化。利用数据处理软件能够得到关注区内每一点的位移-时间历程、应变-时间历程及主应变等。同时,针对TC4材料的动态断裂过程,三维数字图像相关技术能够实时地记录预制疲劳裂纹的张开、裂纹尖端起裂、裂纹分叉扩展、失稳传播等各个阶段,为动态断裂韧性的确定提供了有力工具。

Dynamic tensile mechanical performance of aluminium alloy specimen and the crack initiation time of Ⅱ type crack and instability growth rate due to impact loading of TC4 alloy were measured under the condition of Hopkinson bar loading and based on three-dimensional digital image correlation （3D-DIC）. Two high-speed cameras were used to ensure 3D imaging of the measured object and calibration plate technology allows to obtain quantitative strain profile. Using data processing software, the displacement profile, strain profile and principal strain at every point within area of interest can be detemined by experimental data. At the same time,the crack opening, the tip fracture initiation of prefabricated crack, crack branching and instability growth on different dynamic fracture stages of TC4 alloy can be real-time recorded. Thus, a practical and reliable method to determine crack initiation time and dynamic fracture toughness is proposed in this paper.