Measurement of displacement field around a crack tip using fractal correlation method

Zhende Hou; Yuwen Qin; Lianyun Xiu

doi:10.1117/12.509772

29 April 2003 Measurement of displacement field around a crack tip using fractal correlation method

Zhende Hou, Yuwen Qin, Lianyun Xiu

Proceedings Volume 5058, Optical Technology and Image Processing for Fluids and Solids Diagnostics 2002; (2003) https://doi.org/10.1117/12.509772
Event: Optical Technology and Image Processing for Fluids and Solids Diagnostics 2002, 2002, Beijing, China

Abstract

The key problem to enhance the precision of displacements measurement with image correlation is to make the most of correlation behavior of speckle images. In fact, the artificial random speckles or natural texture, especially the microcosmic texture, on the object's surface have fractal characteristics, and the digital images of these patterns are also fractals. It is found that there is correlation between the fractal characteristics in un-deformed and deformed states of the images. Based on this fact a method called fractal correlation method, can be used to measure displacements. In this paper, the fractal correlation method was used to measure the displacement field on a crack tip of a metal specimen. The microcosmic natural texture on specimen's surface was taken as images, and the area was 1.397×1.397mm. By correlation operation with the fractal correlation method, curves of displacement around the tip can be obtained. The position of crack tip can be clearly distinguished from the displacement curves. The relationship of COD and distance behind the tip is linear. This agrees with the theory of fracture mechanics. The results also show that the plastic field does not distribute in uniform.

Citation Download Citation

Zhende Hou, Yuwen Qin, and Lianyun Xiu "Measurement of displacement field around a crack tip using fractal correlation method", Proc. SPIE 5058, Optical Technology and Image Processing for Fluids and Solids Diagnostics 2002, (29 April 2003); https://doi.org/10.1117/12.509772

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