| Grinding is one of the most important machining methods of engineering ceramics.Because engineering ceramics are brittle and hard to machine materials,in order to improve the quality and efficiency of ceramic grinding,acoustic emission(AE)on-line monitoring of engineering ceramics grinding process has become a research hotspot.The core of grinding ceramics with diamond wheel is the process of removing ceramic materials with single diamond grit.The acoustic emission monitoring of single diamond grit scratch ceramic is an important basis for the on-line monitoring of acoustic emission of ceramic grinding with diamond wheel.Firstly,the research progress of AE technology in grinding process of wheel and single grit scratch material process monitoring at home and abroad is introduced.The experimental scheme of partially stabilizing zirconia and alumina ceramics by diamond grit scratching is established.Based on the measured scratch size,the actual ceramic material removal rate is analyzed.A two-step pick-up method based on VMD is proposed to automatically identify the grinding contact time and accurately pick up the grinding acoustic emission signal.The method is applied to the determination of contact time in the grinding process of single diamond grit and grinding wheel.The results show that the method can effectively avoid the interference of background noise to the grinding acoustic emission signal,and can accurately judge the grinding contact time and pick up the acoustic emission signal.The time-frequency analysis of the single grit scratch AE signal is carried out by using the empirical wavelet transform(EWT)and then the synchronous extraction transform(SET),which overcomes the problem of the traditional time-frequency analysis method mode overlapping,and reveals the change characteristics of the single grit scratch AE signal in the time-frequency domain.The effective value,variance,kurtosis,skewness,energy entropy,time-domain amplitude and time-frequency distribution of the acoustic emission signal of the two kinds of ceramic materials are analyzed with the change of the removal rate of ceramic materials,and the internal causes of the characteristic change of the acoustic emission signal of the two kinds of ceramic materials are deeply studied.Finally,based on the statistical eigenvalue and the singular value of time-frequency spectrum of acoustic emission signal,a prediction model of scratch size of single grit is established according to support vector regression.The results show that there is a good correspondence between the eigenvalue of acoustic emission signal of single grit scratch ceramic and the scratch size of single grit ceramic,which lays a foundation for the acoustic emission monitoring of grinding surface of ceramic. |
