Finite Element Analysis And Experimental Research On Relieving Residual Stress By Vibration Process Method

With the rapid development of nuclear power technology in our country,more and more nuclear reactors have been put into construction and operation in order to meet the increasing energy demand.Large amount of depleted uranium waste is generated during the reactor nuclear fuel process.As nuclear fuel waste is increasingly stored and costly managed,it is necessary to find another way for the depleted uranium waste.Depleted uranium alloys are now widely used in military applications and civil supplies.However,the deformation induced by large residual stress during the production of the depleted uranium alloy blank workpiece,which affects the dimensional stability and brings difficulties to the subsequent process.In order to solve this problem,based on the vibratory stress relief(VSR)technology,various shape types of depleted uranium alloy specimens are taken as the research objection in the paper.The VSR effect and process parameters are studied by using computer simulation techniques and experiment method.This article mainly carries on the following research work:(1)The residual stress are elaborated from the aspects of classification,generation mechanism,elimination and measuring method,and the evolution mechanism of residual stress reduction of VSR is revealed from macro and micro perspective.Based on the working principle of VSR technology,the experiment program and suitable test device of VSR are designed.(2)The elastoplastic finite element model is established to analyze the dynamic characteristics of the depleted uranium alloy blank specimens.Taking the beam and the board specimen as research object,the effect on the residual stress reduction of the parameters of VSR such as vibration mode,supporting point location,frequency,vibration force and vibration time were analyzed.The effect of VSR on accuracy and stability of the workpiece during mechanical process is also analyzed by numerical simulation.(3)The simulation analysis shows that the distribution of the dynamic stress field depends on the frequency,the vibration mode and the vibration force,and the residual stress decreases about 50% after VSR simulation.Based on the numerical simulation result,a composite VSR method is proposed,which means Removal of materials and vibration are combined together during VSR process according to the level and distribution of the initial residual stress of the workpiece,in order to minimize the residual stress at a greater degree.(4)The VSR experiment is carried out to measure the change of residual stress of simulation specimen.Residual stress decreases about 40%~50% after VSR and about 70% after composite VSR,which validated the effectiveness of the composite VSR method.The VSR process parameters to eliminate residual stress were experimentally researched and optimized by orthogonal experimental design method for a certain level and distribution of residual stress field.