多相机3D-DIC及其在高温变形测量中的应用

将基于双目视觉的三维数字图像相关方法 (Three-dimension digital image correlation,3D-DIC)与多相机同步采集系统相结合,形成基于多相机的3D-DIC系统。依据三维空间误差(Three-dimensional residual,3Dresidual)最小原则,确定各点对应的最佳双目视觉系统,获得物体全场三维变形。以四相机3D-DIC系统为例,与测量精度达10~20nm的电子散斑干涉测量系统同时对平板的离面位移进行测量,并对测量得到的离面位移最大值进行了对比分析。结果显示,荷载较小时,四相机3D-DIC与电子散斑干涉测量系统误差稍大,最大达到2.7%;荷载增大,物体变形增大时,两种测量系统结果基本相同。文中讨论了四相机测量系统的不稳定对实验结果的影响。利用该四相机3D-DIC系统对镍合金不锈钢材料在高温场中的变形进行测量,获得了物体的三维变形场,并分析了材料的膨胀系数,得到了试件的热应变-温度曲线和膨胀系数随温度变化的关系式。

On the Multiple Camera 3D-DIC System and its Application in Deformation Measurement at High Temperature

In order to obtain 3D deformation of object, combining 3D-DIC system(Three-Dimensional Digital Image Correlation) based on binocular vision principle with multiple camera synchronous acquisition system to form a multiple camera 3D-DIC system. Based on minimum three-dimensional (3D) residual principle, a system, in which each point is corresponding to the best binocular vision is determined. Thus, 3D contour and 3D deformation of object can be obtained. Taking a four-camera 3D-DIC system as the example, measurement of flat plate out plane displacement was carried out by synchronously using electronic speckle pattern interferometry system with accuracy of 10~20 nm and above proposed system, and the obtained maximum out plane displacement was compared. Results show that when load is small, the maximum error from proposed 3D-DIC system is 2.7%, larger than that from electronic speckle system. With the load increasing (the deformation becomes larger), the measurement results from both measuring systems are basically agree well. The infuluence of instability of four-camera 3D-DIC system on experimental results is analyzed in this paper. Using above proposed system, 3D deformation of a specimen made of nickel alloy stainless steel was measured at high temperature, 3D deformation of specimen was obtained, strain-temperature curve and relation between expansion coefficient and temperature were analyzed.