Study On Cutting Tool Monitoring Methods Based On Nondestructive Inspection

In order to lengthen the operation life of the cutting tool in high-speed cutting,coating technique is widely used in engineering. The homogeneity in coating thicknessand cutting tool integrity are important parameters to evaluate the quality of cutting andthe life of cutting tool. NDT can monitor cutting tool condition without impairing theintended use or application of the tool. Consequently, it is necessary to investigate thefeasibility of the NDT to evaluate the thickness of coatings and defects in cutting tool.The major work and conclusions are as follows:(1) With the goal of building a testing system for measurement of thin coatingsthickness, a finite element (FE) model of eddy current testing system with the coatedsample is built. Base on the FE model, the influence of excitation frequency and lift-offon the magnetic flux density in z-component (Bz) are analyzed firstly; Then therelationship between coating thickness and Bzwere investigated. The investigationindicated that the real part of Bzhave a stronger robustness than Bz. Therefore, the realpart of Bzis suggested to be the detected signal in thin coating thickness measurement.(2) The eddy current testing signal is weak and containing noises due to the thincoating. Wavelet analysis is used to handle the eddy current testing signal. The effects ofwavelet basis, wavelet threshold and time of decomposition are discussed, respectively.The simulation results show wavelet analysis can effectively remove the noise of thereal signal.(3) A cutting model is setup to simulate the temperature distribution in operation.The effect of coating thickness is discussed. A thermal model of the cutting tool is buildbased on the temperature distribution calculated by the cutting model. A series ofinvestigations are carried out to analysis the influences of the depth, the length and thewidth of the defect upon the surface temperature. The investigation indicated that theinfrared thermal imaging can show the condition of the integrity of the base material ofcutting tool.This thesis researches the coating thickness measurement and defect detection ontheoretical analysis and numerical simulation. The result provides basis and references for the manufacturing process.