Strain and Morphology Measurement by Digital Image Correlation Method

• Main Authors: Min-Chien Shen, 沈旻建
• Other Authors: Shun-Fa Hwang
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/61983871064415332864

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 99 === Digital image correlation (DIC) is a whole-field, non-contact and non-destructive strain measuring method. This method captures the surface image of a specimen before and after the deformation, and then the displacement as well as strain information about the surface of the specimen can be obtained by analyzing the change of the images. In this work, a two-step DIC is presented. In the first step, the coarse-fine iterative technique is used to search the displacement of an interested region of the specimen, and then the strain can be obtained by utilizing the finite element method in the second step. To verify the accuracy of this method, a rigid-body motion experiment which prevents the error from the CCD sensor, lighting or other experimental error resource is used. On the surface of the specimen, random specimen speckle pattern by spray paint have been tested. Strain gauges are adhered on the back of the specimen. Furthermore, to have a more stable light resource, we provide the Halogens light as well. By comparing the value from the strain gauge and the method, one can verify the accuracy of DIC. In addition, the effects of image filters (wiener2) and the adjacent images are considered. Also composite material specimens and polymer material specimens are tested to obtain their mechanical properties. Then, the development of three-dimensional digital Image correlation method is developed. The obtained morphology from the surface of a specimen is compared to those obtained from reversed engineering-3D optical scanning system.