Application of Optical Measurement Method in Brazilian Disk Splitting Experiment Under Dynamic Loading

Abstract

A real-time and in situ optical measuring system is developed, which can be used to observe the determination of the displaced field on Brazilian disk splitting under dynamic loading. The system consists of high speed (HS) photography, split-Hopkinson pressure bar (SHPB), synchronization controlling system and the operation of differential image. In the present experiments, photographs of the specimen were taken using a FASTCAM SA1.1 high speed camera, the frame rate was 100,000 fps. The continuous images of rock sample dynamic Brazil fracturing process and stress wave loading on the specimen were observed by synchronization controlling system. The change law of surface displacement field was calculated from the method of differential image base on the joint probability distribution function of two images. This method was considered the image correlation, and effectively eliminated the influence of background noise, and could identify the surface displacement and the occurrence and expansion of the crack in the dynamic Brazilian disk splitting experiments straightforward and effectively. This method can provide a novel measurement of surface displacement field in Brazilian disk splitting tests under high strain rates.

Keywords

• SHPB
• Brazilian disk
• Dynamic loading
• High-speed photography
• Differential image.