P4G-6 A New Method for the Inspection of Tool Wear Based on the Dispersion of ASF Modes

Abstract

Discovered by Lagasse in early 1970's through a numerical study, wedge waves are guided acoustic waves propagating along the tip of a wedge, with energy tightly confined near the apex. Like Lamb waves, wedge waves with displacement field anti-symmetric about the mid-apex-plane are called anti-symmetric flexural (ASF) modes. Without apex truncation, the ASF modes are non-dispersive. However, with apex truncation, the ASF modes are dispersive and the dispersion relation is highly sensitive to the apex truncation. In this research, a laser ultrasound technique (LUT) with a three- dimensional scanning is employed for a non-contact measurement of the ASF dispersion which is related to the tool wear. The basic measurement principle is the dispersion behavior of ASF mode influenced by the wear condition of the machine tool. Figure 1 shows a micrograph of the tool tip before it is used for machining. The tool is then arranged for a sequence of machining/LUT measurement procedure. The ASF dispersion curve is strongly influenced by the machining time. The measured dispersion slopes show as good measure for the quantitative wear of the tools. The current result suggests that dispersion of the ASF modes propagating along the tool tip could be an effective measure for the wear condition. The current technique is continuously been developed to meet the criteria of serving as an on-line wear characterizing technique.