| The cracking processing method is an innovative technology in the field of automobile engine expanding and breaking connecting rod manufacturing,which has been widely used in the manufacturing of different types of connecting rods in many domestic and foreign automobile enterprises.The application of expansion break connecting rod in the development of raw materials is mainly reflected in the following three aspects: strength improvement,mass reduction and cost reduction.In view of the laser equipment in cutting36 MnVS4 connecting rod cracking groove appears to be slag,fracture uneven and other deficiencies,while the domestic process research on pulsed fiber laser cutting 46MnVS5connecting rod has not been reported.And the cracking process of connecting rod processing can only show the initial and final state,it is difficult to understand the essence of cracking processing,and there are more elements affecting the cracking quality,such as the type of connecting rod,the thermophysical properties of the workpiece itself,as well as the laser output power,cutting speed,etc.,so the experimental research method is difficult and time-consuming,and there are great limitations.Therefore,finite element numerical simulation is needed to explore and analyze the cracking process of the new expanded connecting rod 46MnVS5,which advocates "environmentally friendly materials",and conduct experimental research and optimization of the process parameters,which is of great significance for enterprises to improve the processing quality and production efficiency of the connecting rod cracking tank.This thesis presents a numerical simulation of the temperature field and a process study of the pulsed fiber laser processing of a new expansion-break connecting rod material,46MnVS5,with the following main findings and conclusions.（1）The chemical composition and metallographic organization of 46MnVS5 were analyzed,and the expansion and fracture properties of 46MnVS5 and 36 MnVS4 were compared in terms of microstructure and alloying elements.（2）A numerical simulation and analysis platform was built by applying COMSOL Multiphysics to determine the loading method of the laser heat source based on the differential heat transfer equation.The temperature field model of a connecting rod cracking tank processed by a pulsed laser heat source was established and the related techniques（boundary conditions,meshing,etc.）were analyzed.A database of the thermophysical property parameters（specific heat capacity and thermal conductivity）of 46MnVS5 was established and its density was measured by the volumetric method.The temperature field distribution at each laser processing parameter（pulse power,pulse frequency,pulse width and cutting speed）and its influence law on the geometry of the cracking tank were studied and analyzed.The numerical simulation of the temperature field lays the foundation for further experimental study of the relationship between the pulsed laser cutting parameters and the quality parameters of the 46MnVS5 connecting rod cracking tank.（3）Numerical simulations were used as the theoretical basis to design a scientific experimental protocol for a single-factor experimental study of pulsed fiber laser processing parameters for cutting 46MnVS5 connecting rod cracking grooves.The depth and width of the cracking groove under each group of process parameters were observed by the confocal laser microscope in turn,and the tension angle was calculated by the corresponding equation to study the influence of each laser process parameter on the geometry of the cracking groove.Finally,comparing the results of experiments and simulations,the two have good agreement,which verifies the validity of numerical simulation.（4）Within the range of process parameters to meet the processing requirements,the influence laws of process parameters on the cracking groove depth,width and tension angle of each pulsed laser processing connecting rod cracking groove and the influence laws at different levels of different process parameters were investigated by orthogonal tests and using extreme difference and analysis of variance.According to the orthogonal test results,combined with the enterprise connecting rod production processing requirements,the best combination of process parameters for pulse laser cutting 46MnVS5 connecting rod cracking groove was determined: pulse power 1000 W,pulse frequency 1200 Hz,pulse width 90μs,cutting speed 1.2m/min.Finally,the 46MnVS5 connecting rod cracking groove was cut experimentally with the best combination of laser processing parameters,and the expansion and fracture morphology was observed.The results show that: the expansion effect is good,expansion defects are significantly improved to meet the processing requirements of enterprises and production efficiency. |
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