Piston is the “heart” of engine and bears mechanical load and thermal load of alternation, so it is one of the key parts in engine that runs in the worst condition. The role of piston is to bear gas pressure and transfers it to connecting rod via piston pin to drive bent axle. The piston top is also the part of the combustion chamber. Piston works under high temperature, high pressure, high speed and poor lubricating condition. Piston is exposed to high temperature gas and the transient temperature can reach 2500K, therefore, it is severely heated but the heat emission condition is bad; the working temperature of piston is very high and the top can reach 600~700K, and the temperature distribution is not even; the gas pressure of piston is very large, especially the power stroke" the gasoline engine can reach 3~5MPa and the diesel engine can reach 6~9 MPa, which greatly strikes the piston, and it also bears the effect of side pressure; the piston carries out reciprocating motion ...