Analysis And Simulation Of Straightening And Grinding Residual Stress For Linear Guideway

Linear guideways have been widely developed and applied for their advantages of high positioning accuracy,high moving efficiency,and easy installation.During the processing of linear guideway,straightening and grinding are two consecutive finishing operations.Straightening is essentially to plastically deformation the workpiece to ensure the straightness of the linear guideway.After the straightening process,residual stress will be generated inside the guideway.Grinding is an important process to ensure the surface roughness of the linear guideway and its movement accuracy after straightening.The grinding process also produces residual stress.For the machining process of linear guideway,since the straightening process is preceded by the grinding process,the straightening residual stress superimpose with the grinding residual stress,which affects the residual stress distribution of the finished guideway.Therefore,this paper first established the stress distribution equation of the linear guideway along the height direction during the straightening process,derived a numerical calculation model of the straightening stroke.Then,considering the existence of initial residual stress,the grinding residual stress model was established by the two processes of stress loading and stress strain release.Single straightening experiment,grinding experiment and residual stress measurement experiment were carried out.ANSYS was used to simulate the straightening process and the grinding process.The prediction model can provide reference for matching straightening parameters and grinding allowance in the future.The main content and work of this article are as follows:(1)Firstly,based on the elastoplastic theory and considering the strengthening behaviour of the material,a section stress distribution equation and a numerical model of straightening stroke for single straightening process of linear guideway were established.Then,considering the stress inheritance behaviour,the multiple straightening stress distribution equations were derived.The results showed that in two consecutive straightening processes,the distribution of residual stress in the second straightening was more uniform than that in the first straightening.(2)The Mc Dowell hybrid algorithm was used to calculate the grinding residual stress through stress loading and stress strain releasing processes.Then,the initial residual stress of the workpiece was considered,the same calculation principles for the loading and release processes were used to obtain the grinding residual stress prediction model considering the initial residual stress.(3)The numerical model of straightening stroke proposed in this paper was verified by single straightening experiment.The grinding force and the maximum temperature of the grinding surface were measured during the surface grinding experiment.In addition,the surface residual stress generated by the grinding process after the straightening of the linear guideway was measured.The results showed that:(1)As the workpiece speed and grinding depth increased,both the tangential grinding force and normal grinding force increased.(2)After straightening and grinding,the residual stresses in both directions of the workpiece surface were compressive stress.(4)ANSYS software was used to simulate and analyse single straightening process and grinding process.The theoretical model and the finite element model were compared to verify the correctness of the theoretical model of straightening stroke and section stress distribution equation.By simulating the grinding process,the following conclusions were summarized: Under the grinding conditions used in this paper,the residual stress on the workpiece surface caused by grinding was tensile stress.The workpiece speed increased,the residual stress decreased,the grinding depth increased,and the residual stress increased.In the case of grinding process was performed after single straightening process,theoretical calculations and experimental measurement results showed that the residual compressive stress caused by the straightening process caused residual compressive stress on the workpiece surface and its subsurface after grinding under the same grinding parameters.Therefore,when studying the residual stress of linear guides caused by grinding,the initial residual stress of the previous process should be considered.