Wear estimation by testing the elastic behavior of tool surface

Abstract

Impedance and Lamb wave structural health monitoring (SHM) techniques are two common approaches used to successfully monitor the integrity of a variety of structures. In this paper, the feasibility of applying both methods for monitoring tool wear is investigated. Additionally, the surface response to excitation (SuRE) was investigated using spectrum analyzers an alternative to the costlier impedance method. Three approaches were used to monitor the condition of both new and artificially worn drill bits. Artificial degradation of the drill bit cutting edges was necessary to avoid any possible data contamination from accidental damage to the sensors or wiring in a harsh machining environment. The estimated magnitude characteristics found from the impedance and spectrum analyzers correctly distinguished between new and worn tools. Lamb wave characteristics were represented by the envelopes of the propagated signal. The S-transformation was then used to obtain the envelope of the harmonic component of the signal at the excitation frequency. The envelopes were nearly identical at similar tool wear levels, and envelope characteristics changed significantly when Lamb wave reflections reached the sensor from the worn cutting edges. The study indicated that each of the three approaches used successfully detected tool wear.