引張試験片破断音の発生機構

抄録

The aim of this study is to clarify the generation mechanism of the fracture sound for tensile test. A SS400 steel specimen was attached to a universal testing machine. Tensile load was applied to the specimen until right before breaking the specimen and then unloaded. In order to investigate the sound pressure at breaking the specimen, a microphone was set at a 200 mm distance from the specimen. A high speed video camera was also set to focus on necking region of the specimen. White smoke was used to visualize the air flow near the necking region of the specimen. Tensile load was applied to the specimen again until breaking the specimen. As a result of the acoustic analysis of the fracture sound of the specimen, negative sound pressure was initially detected at breaking point. Subsequently, positive sound pressure was also detected. As a result of the image analysis for the image captured from the movie taken with the high speed video camera, the air flow to the fracture region was observed. Both results indicate that vacuum region occurred at breaking point. The air near the specimen rapidly expanded to vacuum region and shrunk. Thus, the fracture sound of the specimen for tensile test would be caused by that the air near specimen rapidly expands to the vacuum occurred at fracture region and shrinks.