Research On Stress Characterization Method Of Thin Plate Material Based On Acoustoelastic Effect

With the rapid development of science and industrialization,the stress state of materials has received more and more attention in aerospace,biomedical,military equipment and other fields.For mechanical components composed of plate,internal stress will inevitably occur during processing and service.This will not only cause tiny cracks inside the component,but also reduce the fatigue life of the component.Finally the component will deform or break.Therefore,it is important to explore the detection method of stress.For the evaluation of stress,ultrasonic testing is widely used because of its non-destructive,high sensitivity,and simple operation.Based on the Acoustoelastic effect and acoustic reflection,this paper studies the plate with stress.The main contents are as follows:(1)Based on the acoustoelastic theory of superimposed small perturbations of acoustic waves on static deformation,an acoustic model including stress parameters is established.The initial prestress is introduced into the theoretical model in the form of strain potential energy under the assumption of a superelastic body.The displacement equation and stress-strain relationship under initial prestress are obtained.In addition,the equations of acoustoelastic in natural coordinates and the third-order elastic constants of solids with stress are deduced.(2)Using the acoustoelastic equation and boundary conditions,the theoretical solution matrix for the reflection coefficient of the prestressed material at the liquid / solid interface is derived.Compare the results of the literature to verify the correctness of the method.Meanwhile,the reflection coefficient spectrum of isotropic single-layer and cladding plates under prestress were calculated.The correlation coefficient is used to analyze the influence of different stresses on the reflection coefficient spectrum,which provides a new theoretical basis for ultrasonic detection of stress.(3)For the stress measurement of thin plates,a finite element model for measuring the acoustic reflection coefficient under stress is established.The reflection coefficient at the liquid / solid interface is extracted through finite element model.At the same time,the influence of different stresses on the reflection coefficient spectrum was analyzed.Finally,comparing and verifying the simulation results with the theory.(4)Based on the acoustic microscopy,the theoretical of reflection coefficient is established.The defocusing experiment was carried out on the thin plate,and the experimental results were compared with the theoretical calculation results to verify the correctness and feasibility of the proposed method.At the same time,the study of the reflection coefficient measurement of the thin plate under different stress was carried out to analyze the effect of different stresses on the reflection coefficient.This laid the foundation for characterizing the stress state of the thin plate using acoustic microscopy.