Study On The Crack Initiation And Expansion Mechanism Of Low Stress Cropping Based On Acoustic Emission Signal

The separation and separation of metal rod pipe is the first step in equipment manufacturing,automobile industry,bearing industry,petroleum and petrochemical industry,etc.In the traditional way,sawing is mainly used for cutting.However,there are some disadvantages such as high energy consumption and waste material.Under the low stress,the advantages of the materials are low energy consumption,high material utilization rate and low pollution,which conform to the green manufacturing concept advocated by modern society.However,it is difficult to judge the crack initiation of v-shaped slot in the low-stress process.The extended model is not accurate enough,and the problem directly influences the loading time and initial loading force.This article introduced the mutation theory,established a rod crack under low stress of material cusp catastrophic model,the model with an average depth of a crack,as state variables,in order to load and cycle number N F as control variable,with the energy of the bar on V as a potential function.It is concluded from the analysis of mutation model that there exists an unstable equilibrium surface on the equilibrium surface of the system,and the occurrence of crack must satisfy the control trajectory to reach the bifurcation point set.Based on the combination of qualitative and quantitative methods,this paper determines that the sym7 wavelet is a wavelet base suitable for the analysis of the acoustic emission signal,and the wavelet de-noising algorithm is presented.The results of the analysis pointed out that sym7 wavelet function for blanking acoustic emission signal de-noising treatment has good effect,signal-to-noise ratio SNR values more than 20,can suppress noise effectively while maintaining high signal-to-noise ratio.Through the frequency domain analysis of the acoustic emission signal of the blanking process,the frequency range of the signal is found to be concentrated between 100 kHz and 200 kHz,and the amplitude decreases with the increase of crack propagation.Based on the analysis of signal waveform form,the method to judge the crack of rod by the modal coefficient and skewness is put forward.In this article,through the traditional AE characteristic parameter analysis method,the crack criterion based on waveform form method the accuracy of the new variable T is constructed at the same time,and based on the variable T crack of the bar is the quantitative criterion.The stress intensity factor is deduced and the relational expression of the acoustic emission ringing count,the acoustic emission ringing count and stress intensity factor in the relation between the coefficient k and specific value of the material constant m: k = 11971,m = 0.357.Through the comparison and analysis of the characteristic parameters of the acoustic emission,the initial initiation,stable expansion and instability expansion of the bottom crack of the rod V groove are determined.The stress intensity factor is deduced and the relational expression of the acoustic emission ringing count,on this basis,the acoustic emission ringing count and stress intensity factor in the relation between the coefficient k and specific value of the material constant m: k = 11971,m = 0.357.In the crack process of low stress bar material,on a single characteristic parameters are difficult to complete description the problem of low utilization ratio of the sound source signal and sound signal data,on the basis of the theory of data fusion is proposed based on principal component parameter crack propagation model of fusion algorithm.Compared with the single feature parameter model,this paper established the crack propagation model based on multiple parameters fusion value has obvious advantages,mainly reflected in: based on the established model and the experimental data of the method of correlation coefficient is close to 1,compared with the single feature parameters of the correlation coefficient increased 0.8.