利用单单元扩展数字图像相关方法测试裂纹尖端变形场.docVIP

  Crack tip deformation measurement using single-element extended digital image correlation# 5 10 15  Abstract: Since the crack tip displacement field influences the crack paths under both fatigue and fracture conditions strongly, it is very important to develop a test method with high accuracy to measure this deformation parameter. Single-element extended digital image correlation (X-DIC) using the enrichment function to describe the crack tip singularity, which could measure the discontinuous deformation directly. Simulated images are used to verify the performance of single-element X-DIC, the measured crack tip displacement field is in accordance with the given value. Displacement fields of the compact tension specimen under pure mode I loading condition was measured. The influence to the measurement accuracy caused by the crack width，subset size and subset location was discussed. All results in this paper show that single-element X-DIC could be used to measure the crack tip displacement field with high accuracy. Key words: Experimental solid mechanics; crack tip deformation; extended digital image correlation (X-DIC); subset 20 0 Introduction The path that a crack follows is strongly influenced by the elastic and plastic displacement field at the crack tip [1]. Although electrometric method is used widely for engineering application, strain gauge must be adhered to the specimen, it is a contact and non-full-field test method. 25 30 35 40 45 Photoelastic stress analysis, Moire interferometry and other traditional optical measurement methods could successfully characterize the elastic stress fields around cracks. However, these methods require the strict test environment and the operation of fringe is too trivial. Digital image correlation (DIC) method possesses many advantages such as its simple experimental steps, high accuracy and high computational efficiency, so it has been applied to measure the deformation of the materials on the multi-scales extens