Causes of cracks on the edges of the combustion chamber of the diesel engine piston

Internal combustion engines operate in non-stationary operating modes, when the crankshaft rotational speed changes over wide ranges, not only the torque but also the angular speed changes. While transients occurring in the cylinder of an internal combustion engine during operating modes, especially for tractor diesels, are the most unfavorable for parts of the cylinder-piston group. Long cycle changes during which pressure, temperature, piston speed and heat transfer surface are constantly changing creates very difficult loading conditions. Moreover, the peak values of thermal powers through the heat exchange surfaces of the piston bottom in unsteady modes are 2 ... 2.5 times higher than the values at steady modes. High values of thermal and mechanical loads on the piston lead to cracks on the edge of the combustion chamber and premature destruction. Failure in pistons can be caused by mechanical and thermal loading, but thermal loads make the greatest contribution to the value of equivalent stresses. Therefore, cracks gradually develop, which often leads to a deterioration of the working process, and then to the destruction of the piston.