Modeling And Control Methods For Residual Stress In Cam Shaft Swing Grinding Considering Service Process

As the design width of the camshaft profile of marine diesel engines increases,so does the difficulty of machining.With conventional plunge-cut grinding,the large grinding contact area is prone to high grinding temperatures,which leads to residual stresses on the machined surface that are out of tolerance,thus affecting the service performance and service life of the camshaft.To solve the problem that plunge-cut grinding is not suitable for wide camshaft profiles,an swing grinding process is proposed in which the grinding wheel is fed purely by rolling along the camshaft profile while making a periodic reciprocating motion along the axial direction.By using a narrow grinding wheel to machine a wide camshaft profile,the grinding contact area is reduced and the surface quality and machining efficiency are improved.However,the influence of the camshaft swing grinding process parameters on the residual stresses on the machined surface is still unclear,the matching of the grinding process parameters under the swing grinding method is not studied systematically enough,and there are uncertainties and blindness in the selection of the process parameters.At the same time,neglecting the effect of residual stresses during the service life of a camshaft often leads to inaccurate predictions of camshaft life.Accurate description of the evolution of residual stresses under cyclic loading is the basis for accurate predictions of camshaft fatigue life.As camshafts are subjected to inhomogeneous residual stresses during the grinding process,they are also subjected to inhomogeneous loads during service.It is difficult to perform experimental studies of the evolution of complex residual stresses in camshaft service,and finite element analysis methods have difficulties in accurately describing the ratchet behaviour of stress-strain under cyclic loading of camshafts.To address the above problems,to give full play to the technical advantages of swing grinding,the in-depth integration of oscillation grinding process parameters and fatigue performance is realised.This paper conducts an in-depth study based on a combination of models(FEM)and experimental verification.The specific research content is as follows:(1)Using the heat-force sequential coupling analysis method,the FEM of the temperature field of camshaft swing grinding was first established based on the ABAQUS heat source subroutine DFLUX,and then the results of the simulation of the grinding temperature field were coupled with the applied grinding force for multi-field analysis,and finally a FEM of the residual stress field of camshaft swing grinding under the action of multi-field coupling was established.(2)To analyse the stress-strain ratchet behaviour characteristics of the camshaft in service and derive a cyclic plasticity principal structure equation considering mixed hardening coupled damage,which is written as the ABAQUS user material subroutine UMAT.at the same time,the cyclic load applied to the camshaft in service is written as the ABAUQS user load subroutine DLOAD.combining the written UMAT and the FEM of the residual stresses in the camshaft during variable load service is established by combining the two subroutines UMAT and DLAOD.(3)Measurement of residual stresses in the camshaft profile after swing grinding using X-ray diffraction,thus verifying the rationality of the established FEM of residual stresses in camshaft swing grinding.The blind hole method was used to measure the residual stresses in the designed simplified test workpiece to verify the reliability of the FEM of the residual stresses during variable load service of the camshaft.The results show that the two FEMS developed are reasonable and reliable.(4)Based on the established FEM of the residual stress field in camshaft swing grinding and the FEM of the residual stress in camshaft variable load service process,the effects of various process parameters on the temperature and stress fields in camshaft swing grinding and the evolution of the residual stress in camshaft under the same initial conditions,different cyclic loads and different grinding methods are investigated.Finally,with the residual stresses in service on the camshaft profile as the evaluation index,the process parameters of swing amplitude,swing frequency,grinding wheel diameter,grinding wheel width and workpiece speed were optimized under the same grinding depth and grinding wheel linear speed parameters to find the optimal combination of process parameters.The optimum process parameters were obtained as n=2600 mm/min;D=280mm;B=15 mm;f=60 times/min;F=1 mm.