Research on fatigue cracking failure mechanism of diesel engine piston combustion bowl
The engine fatigue durability reliability bench tests were carried out under the same experimental conditions for two diesel engine pistons with different structures until the piston failed.After the tests,the microstructure and crack morphology of the cracked piston were characterized by metallographic microscope and scanning electron microscope,and then the cracking failure mechanism of the piston combustion bowl was studied in combination with finite element simulation technology.The results show that mechanical or thermo-mechanical coupling load induces higher tensile stress at the bottom of the piston combustion bowl,while the maximum hoop stress of the mechanical load appears at the bottom of the combustion bowl in the direction of the pinhole axis.The longer the piston runs,the more likely it is to become"over-aged",which results in a significant loss of strength and hardness of the piston,and the risk of cracking failure.By moving the position of the cooling gallery inside the piston upwards and redesigning the top of the chamber with equal wall thickness according to the shape of the combustion chamber,the mechanical and thermo-mechanical coupling stress in the combustion chamber can be reduced,which effectively improves the service life of the piston.
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