Experiment And Numerical Analysis Of Low Cycle Thermal Fatigue Strength Of Aluminum Alloy Piston

Diesel engines are widely used in commercial vehicles,trucks and construction machinery,and piston is one of its core components.The working environment of piston is extremely harsh,and it is easy to cause fatigue damage,which leads to abnormal operation of diesel engine.In the actual operation condition,the piston thermal fatigue damage caused by the cold and hot low-cycle cycle of "start and stop" is the most serious.The study on the low-cycle fatigue life can determine the maximum number of "start and stop" allowed by the diesel engine,which is of great significance to the design of the piston.In this paper,aiming at the thermal fatigue performance of aluminum alloy piston,the low-cycle thermal fatigue performance of aluminum alloy piston and the fatigue life prediction method are studied by combining experimental test and finite element simulation analysis.The specific contents are as follows:(1)Through the thermal fatigue test platform using electromagnetic induction heating as the heat source,the temperature cycle in the thermal fatigue test of aluminum alloy piston is precisely controlled,and the temperature history curve and thermal fatigue life of piston under different temperature cycle schemes are obtained;Materials were extracted from the piston throat and processed to make test bars.By using the test bar TMF test bench,different temperature cycles and constraint rate schemes were set up.Through the test bar TMF test,the constraint rate-fatigue life diagram was obtained.(2)UG software and ANSYS software were used to establish a three-dimensional finite element calculation model for aluminum alloy piston.Then the method of magneto-thermal coupling and the model of gaussian normal distribution surface heat source are used to obtain the mathematical expression of equivalent heat source.The equivalent heat source expression is applied to the finite element model of piston,and the transient temperature field of piston is calculated.(3)Based on the temperature field,the finite element model of the piston was analyzed for thermosetting coupling,and the stress-strain distribution of the piston was obtained.The thermal strain and total strain at the piston throat were extracted,and the constraint rate at the piston throat was calculated according to the formula of constraint rate.Compared with the thermal fatigue test,the validity of the constrained rate-fatigue life method is verified.The thermal fatigue performance of aluminum alloy piston is studied by experiment and numerical method,and the validity of fatigue life prediction method is verified,which provides reference for fatigue life prediction of piston.