Steady and Cyclic Thermal Stresses of Diesel Engine Pistons - A Photothermoelastic Study and Calculation

A photothermoelastic analysis was used to investigate the steady thermal stresses of the pistons of 4-cycle, high-speed diesel engines, and the cyclic temperature swing of the piston surface in relation to the cyclic thermal stresses was investigated with a digital computer method.

The investigation revealed that axisymmetric analysis as an approximation was enough to estimate the steady thermal stresses, and that a major cause of the stress was the radial thermal gradient in the top of the pistons.

The cyclic temperature swing and cyclic thermal stress, calculated in connection with time-averaged heat flux, reached considerably higher value than that calculated by usually used equations of instantaneous heat-transfer coefficient.