The piston in direct contact with the high temperature gas instantaneous temperature can reach 2500K above, therefore, is serious, and the radiation condition is very poor, so the piston when the temperature is high, top up to 600 ~ 700K, and the temperature distribution is not uniform; piston the top under air pressure, especially the power stroke gasoline engine maximum pressure, up to 3 ~ 5MPa, the diesel engine is up to 6 ~ 9MPa, which makes the piston impact, and bear the side pressure; the piston in the cylinder at a high speed (8 ~ 12m/s) reciprocating motion, and speed changes constantly, it produces a large inertial force, the piston is great additional load. The piston to work in such harsh conditions, will produce deformation and accelerated wear, will produce additional load and thermal stress, at the same time by the chemical action of gas.…