Study On The Application Of Electrochemical Machining Technology In Residual Stress Measurement By Small Hole Method

Residual stress is an inevitable phenomenon in the process of processing and production of mechanical parts.Especially,there are large residual stresses in the interior of important structural parts.Residual stress will have a serious impact on the static strength and fatigue strength of mechanical parts,resulting in technological defects of mechanical parts in the process of processing and production,and then affecting mechanical parts.The performance of the system.Therefore,the measurement of residual stress of mechanical parts is an important index for evaluating the integrity of workpiece surface processing.Since the development of the last century in the 1930 s,a variety of residual stress testing methods have emerged in an endless stream.However,despite the tremendous efforts made by researchers in the field of residual stress testing,there is still a strong need to continuously improve the existing residual stress testing technology and explore new residual stress testing technology.Measuring near-surface residual stress of mechanical parts by small hole method has the advantages of high reliability and large measuring depth.It is one of the most widely used residual stress testing methods in engineering field.However,additional stress is easily introduced in machining small holes by mechanical processing methods such as drilling and milling,which affects the measuring accuracy and results of near-surface residual stress.Due to the advantages of no stress effect in the machining process and wide applicability of processing materials,electrochemical machining(ECM)has a significant advantage in measuring the near surface residual stress of small holes.In this paper,pure iron material is taken as the research object,aiming at the unique advantages of electrochemical machining in measuring residual stress by small hole method,the application of electrochemical processing technology in measuring residual stress by small hole method is studied.The electrochemical characteristics of pure iron-electrolyte system were studied by measuring the anodic potentiodynamic polarization curves of single component electrolyte and composite component electrolyte at different concentrations.The composition and concentration of electrolyte suitable for electrolytic processing of pure iron materials were optimized.Accurate control of the hole depth in electrochemical machining is the key technology to ensure the accuracy of residual stress measurement.Based on Faraday’s first law,this paper adopts constant current electrochemical machining method to analyze the current efficiency under different processing time,and revises the relationship between the processing depth and processing time,so as to realize the requirement of controlling the hole depth.Based on the basic principle of residual stress measurement by small hole method,the elastic parameters of pure iron materials were measured by experiments.Abaqus software was used to simulate and analyze the influence of the corner between the bottom and the side wall of the small hole on the residual stress test results.In this paper,an experimental device for residual stress measurement by electrochemical machining(ECM)keyhole method is built by combining ECM process equipment with resistance strain gauge measurement technology.Based on X-ray diffraction method,a comparative experiment of residual stress measurement by ECM keyhole method and mechanical machining keyhole method for pure iron specimens is carried out.The experimental results show that the error of residual stress measurement by electrochemical machining small hole method is small,which can meet the test requirements.The application method of electrochemical machining technology in measuring residual stress by small hole method is feasible,and the measurement results are more accurate.