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Stress acting on Piston Crown

The Piston is subjected to compressive and tensile stress caused by the bending action due to gas forces and thermal loading. When a piston crown is subjected to high thermal load, the material at the gas side attempts to expand but it is partly prevented by the cooler material under it. This leads to compressive stress in addition to the stress imposed mechanically due to variation in load at the time of compression / ignition stroke and exhaust / inlet stroke of the piston.

At very high temperature, the metal can creep to relieve these compressive stresses and when the piston cools, residual tensile stress is set up, hence residual thermal stress. If this stress is sufficiently great, cracking of the piston crown may result


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