Evolution And Control Of Residual Stress In The Manufacturing Process Of Marine Diesel Engine Pistons Based On Finite Element Analysis

Cast iron piston is one of the core components of marine diesel engine.Its complex structure and harsh working environment require it to have high reliability and dimensional accuracy during service.The release of residual stress accompanies the entire production process of the piston,which can be roughly divided into three stages: casting,machining,and heat treatment.The existence of residual stress will directly affect the strength and stiffness of the piston,reducing its service life.Therefore,it is necessary to study the residual stress in the manufacturing process of the piston,in order to improve the manufacturing process and achieve low-stress manufacturing of the piston,so as to improve its working performance.In this thesis,the cast iron piston produced by a certain enterprise is taken as the research object.A multi-process continuous simulation process for the manufacturing process of marine diesel engine piston is established,so as to study the residual stress in the manufacturing process and has important engineering value for improving the existing manufacturing process.The specific research contents are as follows:(1)The residual stresses at various stages in the process of piston manufacturing were analyzed based on theoretical foundations,and a multi-process continuous simulation mathematical model for the manufacturing process of the piston was established.The feasibility of continuous simulation of residual stresses in multiple processes was verified through numerical algorithm testing.Based on the requirements of each process,corresponding simulation software was selected,and a data transfer scheme was determined for the stress data files between different software,providing reliable technical support for multi-process continuous simulation of residual stresses in diesel engine pistons,and providing strong support for further development in the field of piston manufacturing.(2)According to casting process theory,the structural casting process was analyzed for diesel engine pistons,and a three-dimensional model of the piston was established.The bottom-injection casting scheme was selected for the piston casting,and the casting system and riser compensation system were designed.Pro CAST software was used for numerical simulation of the casting process of the piston.The temperature field and flow field distribution of the filling and solidification stages of the piston casting were analyzed,and the influence of pouring temperature and shakeout temperature on residual stresses in the piston was studied.(3)Based on the residual stresses in the piston casting process,a finite element model of the clamping key process in piston machining was established,and the simulation results were verified through clamping experiments.The machining process of the piston was analyzed,and the Model change function was used to remove the material of the cutting part of the piston during machining.The numerical simulation of the piston machining process was carried out,and the changes in residual stresses in the piston before and after machining were analyzed.The influence of different initial stresses on residual stresses in the piston after machining was studied.(4)A finite element model of the piston heat treatment was established,with the residual stresses after machining as the initial stress field,simulating the formation and change of residual stresses in the piston during different heat treatment processes.The influence of factors such as heating rates,insulation temperature,holding time,and cooling rates on residual stresses in the piston was studied,and the interaction between heat treatment process parameters was studied using orthogonal experimental design,obtaining optimized heat treatment parameters and improving the level of residual stress elimination in the piston.