RESEARCH OF ENGINE PISTONS FORM POINT OF VIEW OF THERMAL SHOCKS

Experimental test results of thermal shocks for heavy duty pistons of combustion engines are presented in the paper. The range and the level of thermal loads were dive rse and dependent from working engine conditions as well as the temper ature ranges were adapted for real conditions in w hich pistons of the combustion engine w ork. Temperature measurement results on crown and skirt of a piston during an engi ne operating under different conditions are presented in the paper. Measured temperature differences during engine operating were great est in areas, where appeared greates t piston temperatures. Researches of thermal shocks were realized on the speci al testing device. The device this is automatic, controlled a c omputer, makes possible the re alization of the cycle of research of thermal shocks in t he necessary range of the temperature. Test results showed that in following cycles of thermal s hocks took place stable changes of dimensions of the piston too. Main factors effecting on the resistance of piston materials on thermal shocks are presented in the pape r, at this essential par ameters influent on the re sistance of materials on thermal shocks are coefficients of thermal expansion and Young' s modules. In particu lar thermal shock resistance of the different piston alloys, dependence of dimensional thermal tensions vers us the undimensional heat flux, Basic parameters of the composite material AK12 +20%Al2O3 and standard, values of heat conductivity coefficient the and temperature on the composite piston surface, values of stresses due with the temperature field in piston, values strains i n the composite piston due the te mperature field, the example of the influence of the number of ther mal shocks on the deformation of the piston sample are presented in the paper.