| The most stringent emission standard of GB6 b will be fully implemented in 2023.In order to meet the requirements of energy consumption and emission,many advanced combustion technologies are applied to the engine to achieve the purpose of full combustion.At the same time,these measures also make the load conditions such as cylinder burst pressure and cylinder temperature more severe,and the piston and other parts in direct contact with it are more prone to fatigue and wear failure The corresponding improvement measures must be taken,such as optimizing the material properties and structural strength.Relevant research shows that high load engine is the most direct cause of piston fatigue damage,and the piston fatigue damage occupies a high proportion in piston failure,which seriously affects the reliability of engine operation and becomes the weak link of engine further development.In order to meet the requirements of engine performance,some new aluminum alloy materials have been developed and used successively,such as new aluminum alloy materials 174 and +174.Although these two kinds of new material pistons can meet the requirements of the engine,some basic physical properties and fatigue properties need to be measured.In this paper,these two kinds of new aluminum alloy pistons are taken as the research object,their chemical composition and structure are systematically tested,samples are prepared and systematic high temperature fatigue test of materials and high cycle fatigue test of parts are carried out Three main aspects of the study:(1)The basic physical properties of aluminum alloy piston material are studied.The basic physical properties,thermal physical properties and conventional mechanical properties of the sample are systematically tested.The density and hardness of the material at room temperature,the thermal conductivity at different temperatures,the tensile strength at different temperatures,the modulus of elasticity at different temperatures and the coefficient of thermal expansion at different temperatures are obtained.(2)Study on the thermal fatigue properties of aluminum alloy piston materials,study the high temperature stress fatigue properties of 174 and 174 + aluminum alloy materials at different temperatures,and draw the cyclic stress curve according to the experimental results.The fatigue test of pin hole was carried out,the surface morphology and metallographic structure of pin hole cracks were observed,and therelationship between creep deformation and fatigue was analyzed.(3)The fatigue life of aluminum alloy piston is simulated by finite element method.Taking 174 aluminum alloy piston as the research object,the solid model of piston is established.The measured real test data and experience data are substituted into the finite element model to carry out the finite element simulation calculation.Compared with the results of bench test,the calculation results are optimized to provide design support for improving the reliability of piston. |
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