OPTICAL MEASUREMENT METHOD FOR DYNAMIC MECHANICAL TESTING BASED ON IMAGE GREY LEVEL DISTRIBUTION DIFFERENCE MODEL

Zhiqiang Yin^{1, 2}, Lei Wang^{1, 2}, Haifeng Ma³

¹The Provincial Key Laboratory of mining effects and disasters preventing under deep mining in Anhui, Anhui University of Science and Technology, Huainan, Anhui, China, 232001

²School of Mineral and Safety, Anhui University of Science and Technology, Huainan, Anhui, China, 232001

³Faculty of Resources and Safety Engineering, China University of Mining and Technology, Beijing, China, 100083

This study developed an optical measuring system with a gray level distribution difference (GLDD) model, and applied the system to examine the displacement field of a Brazilian disk (BD) split under dynamic loading. The system consists of high-speed (HS) photography, a split-Hopkinson pressure bar (SHPB), a synchronization control system and operation of differential images. First, we captured differential images with a high speed camera (10 frames at a time resolution of 10μs). Next, we established the corresponding relationship between the dynamic fracturing evolution of the disc rock samples and the stress loading process with a synchronization controlling system. Changes in the surface displacement field were calculated with the differential image base method according to the joint probability distribution function of two images. This method takes the image correlation into account and can effectively eliminate the influence of background noise, identify surface displacement and capture cracks and expansion in dynamic Brazilian disk splitting experiments straightforwardly and accurately. Findings can be used for novel measurement of surface displacement fields in Brazilian disk splitting tests under dynamic loads.