DIC数字图像相关技术原理 见之前的文章，本篇文章为原理后续，通过一个3D应用案例：铝合金狗骨样件拉伸试验，以使大家对DIC原理有更形象具体的认识。
内容包括：试验布置、散斑图案、试件颈缩试验结果
3D应用案例: 铝合金狗骨样件拉伸试验 / 3-D Example Application: Aluminum Dog-bone Tensile Sample
第一张图显示了铝合金狗骨试件测量时3D DIC系统的实验布置。 VIC-3D测量系统通过连接到试验机控制器获取载荷输出，并与图像采集数据同步记录负载数据。
The first picture shows the test setup for 3D image correlation measurements on an aluminum dog-bone sample. The VIC-3D measurement system is connected to the load ouput of the test frame controller and records load data synchronously with the images.
特写显示3D系统的两个图像采集器聚焦在样件上。试件使用光纤鹅颈式灯光进行照明，可以方便地进行调节，以在整个试件上提供均匀的照度。
The close-up shows the two cameras of the stereo system focused on the sample. The sample is illuminated using fiber-optic goose-neck style lights that can conveniently be adjusted to provide even illumination across the entire sample.
散斑图案 / Speckle Images
两幅图像分别显示了由3D系统的左侧和右侧相机拍摄的未变形状态下的狗骨试件散斑图像。
显示的试件是0.5“宽和0.1”厚。标距长度是5“。
散斑图案是使用自喷漆制作的，首先用一层白色涂料喷涂覆盖铝试件。 然后通过轻轻地喷涂黑漆雾来制备黑色散斑。
The two imagesshow the speckle images of the dog-bone sample in the undeformed state recorded by the left and right camera of the stereo system, respectively.
The sample shown was 0.5″ wide and 0.1″ thick. The gage section was 5″ in length.
The speckle pattern was applied by first coating the aluminum sample with a layer of white paint using a spray can. The black speckles were then applied by lightly over-spraying a black mist of paint.
试件颈缩 / Specimen Necking
下图显示了失效前试件上的彩色云图的离面位移（W值）。试件最终破坏发生时显示出典型的局部颈缩特征。
The graph below shows the out-of-plane displacement (W) as a color-coded overlay on the sample just prior to failure. The sample showed the typical localized necking where ultimately failure occurred.
应力-应变曲线 / Stress-Strain Curve
图片显示了试件的应力 - 应变曲线。测得的应变是大约1/8"标距长度上的区域平均值。
The stress-strain curve for the sample is shown. The measured strains were averaged over an area corresponding to a gage length of approximately 1/8″.
由于VIC-3D计算试件表面上的拉格朗日应变张量，横向应变可用在基于体积守恒约束计算的样品横截面积减小。 在右侧的图中，以绿色显示的是用减小的横截面积计算的实际应力 - 应变曲线。
Since VIC-3D calculates the Lagrangian strain tensor on the specimen surface, the transverse strain can be used to calculate the reduction in cross-sectional area of the sample using a volume conservation constraint. In the graph on the right, the actual stress-strain curve using the reduced cross-sectional area is shown in green.