Research On Method Of Acquisition For Simulation Acoustic Emission Signal In Metal Fatigue Crack Based On Virtual Crack Closure Technique

Metal components with complex loading and poor working environments are prone to fatigue cracks.Nowadays,fracture parameters of metal components can be obtained directly using finite element analysis,but it cannot be acquire measured directly by fatigue test with under cyclic load.According to the problems in metal fatigue crack detection,this paper expanded the fracture parameters to acoustic emission parameters,on the basis of analysis for the mechanism of metal fatigue crack growth and principle of acoustic emission detection,acoustic emission element based on virtual crack closure technique was developed by using ABAQUS user element function.The acoustic emission element was called to obtain metal simulation acoustic emission signal of fatigue crack propagation.A metal fatigue crack acoustic emission test was conducted to verify the simulating acoustic emission signals made for the acoustic emission element based on virtual crack closure technique.(1)The mechanism of acoustic emission with fatigue crack propagation and acoustic emission detection of metal components material principle was analyzed,the expressions of acoustic emission signal amplitude based on finite element analysis was derived based on elastic wave theory and transfer function of the detection system.(2)By using the feature of UEL user-defined units in ABAQUS,acoustic emission element based on virtual crack closure technique was developed for obtain simulating acoustic emission signals of metal fatigue crack.The element combined the discrete Finite analysis steps together which contains calculation of energy release rate of crack propagation,displacements on the surface of metal components and the final simulation of acoustic emission signal in output.Acoustic emission element was called in Finite element analysis of three-point bending example,the simulation of acoustic emission signal for fatigue crack propagation was exported.(3)The finite element model of metal components was created in the ABAQUS,simulation of acoustic emission signal of metal fatigue crack propagation was obtained by calling acoustic emission element based on virtual crack closure technique.The transmission paths,loading and time-frequency distribution was studied respectively to observe the characteristics of acoustic emission signal.A metal fatigue crack acoustic emission test was conducted finally to acquire the acoustic emission signal of metal fatigue crack under cyclic loading,simulation acoustic emission signal obtained by using acoustic emission element based on virtual crack closure technique was verified through test,it proved that the acoustic emission element based on virtual crack closure technique can be used to get the fatigue crack propagation simulation of acoustic emission signal.Results of this research can provide a new way to study on metal fatigue crack propagation,and which are of practical significance.