Digital Image Correlation (often referred to as “DIC”) is an easy to use optical method which measures deformation on an object’s surface. The method tracks the changes in gray value pattern in small neighborhoods called subsets (indicated in red in the figure below) during deformation. Digital Image Correlation has repeatedly proven to be accurate when compared to valid FEA models. The commercially available VIC-2D and VIC-3D systems from Correlated Solutions utilize this advanced optical measurement technology.
DIC原理书籍 / Digital Image Correlation Book
美国Correlated Solutions, Inc (CSI)公司的缔造者们共同撰写了《Image Correlation for Shape, Motion and Deformation Measurements: Basic Concepts,Theory and Applications》一书。 本书是数十年来2D和3D数字图像相关软件的研究和开发的总结，并已经在VIC-3D产品中实施。 这本书可以从许多在线零售商处购买，也可直接从CSI购买。
The book “Image Correlation for Shape, Motion and Deformation Measurements: Basic Concepts,Theory and Applications” (seen below) was co-authored by the founders of Correlated Solutions. The book is a collaboration of decades of research and development of 2D and 3D digital image correlation software, which have been implemented into our products. The book can be purchased from many online retailers or directly from Correlated Solutions.
DIC原理概述 / Digital Image Correlation Overview
Below are the reasons why its versatility, robustness, and ease of use make it the only choice when it comes to digital image correlation.
The two pictures below show a speckle pattern on an aluminum sample with two offset semi-circular cut-outs. The two pictures were taken from an animation with the left image taken from the beginning and the right picture taken from the end of the animation. Since the deformation is predominantly in-plane, a single camera can be used to measure the deformation.
The pictures below show the horizontal strain measured by two-dimensional image correlation for the pictures shown above.
The two speckle images below were taken simultaneously with the left and right camera of a stereo-system. The sample itself is a piece of glass with our company logo sticker adhered to the surface. The speckle pattern was applied using standard off-the-shelf flat white and black spray paint. Can you make out the shape?
The first picture on the left 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.
The close-up on the left 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.
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.