The aim of this study is to investigate the dynamic phenomenon of ultrasonic vibration-assisted cutting condition by utilizing visualization system of stress distribution. The vibrating cutting edge is considered to be cause of dynamic change of cutting force at ultrasonic frequency. However, many researchers have explained the effect of ultrasonic vibration-assisted cutting by evaluating the time-averaged cutting force, because the dynamometers have insufficient frequency characteristics to measure the dynamically changing cutting force in ultrasonic frequency. In this study, the instantaneous stress distribution on workpiece was visualized by photoelastic method in combination of pulse laser emission synchronized with tool vibration. A constructed photographic system is able to capture 360 flames for one ultrasonic vibration period. Dynamic cutting force is calculated by stress distribution by Flamant theory. It was experimentally confirmed that the stress distribution under vibration-assisted condition showed the periodical change synchronized with insert vibration. Because these results are compatible with well-known vibration cutting theories, the imaging system is able to show the periodic change of stress distribution in ultrasonic frequency band. It is considered that the dynamic change of cutting force for ultrasonic vibration period affects intermittent cutting condition. In this report, the vibration direction was adjusted from −9.54° to +9.5° to the cutting direction. When the tool moved in upward for the cutting phase and downward for withdrawal phase, the stress distribution continued to be observed over one period of tool vibration and intermittent cutting did not occurred. The locus of cutting force vector was affected by the ultrasonic vibration direction and rake angle of cutting tool. Negative rake angle showed that the direction of the cutting force vector shifted to the workpiece side near the most advanced position of the cutting edge.

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