The piston works under conditions of high temperature, high pressure, high speed and poor lubrication. The piston is directly in contact with high temperature gas, and the instantaneous temperature can reach 2500K or more. Therefore, the heat is severe and the heat dissipation condition is very poor. Therefore, the temperature of the piston is very high, the top is as high as 600~700K, and the temperature distribution is very uneven. The gas pressure is very large, especially the work stroke pressure is the largest, the gasoline engine is up to 3~5MPa, and the diesel engine is up to 6~9MPa, which makes the piston impact and bears the side pressure; the piston is at a very high speed in the cylinder (8 ~12m/s) reciprocating motion, and the speed is constantly changing, which produces a large inertia force, causing the piston to be subjected to a large additional load. When the piston is operated under such harsh conditions, it will deform and accelerate wear, and will generate additional loads and thermal stress, while being chemically corroded by the gas.