Thermo-Mechanical Fatigue Life Assessment of Diesel Engine Hot Components

Most of mechanical components of automobile engine and structures applied in powerhouses, petrochemical and aviation industries are subjected to different kinds of cyclic loadings, such as low cycle fatigue (LCF) stresses at high temperatures. Thermo-mechanical fatigue is the dominant cause of fracture in these components.Therefore, investigation of different thermo-mechanical fatigue life assessment methods of these components is very necessary. When a component is subjected to high temperature thermal cycles and mechanical strain cycles simultaneously, the thermo-mechanical fatigue process leads to micromechanical damage and final fracture of the component.In this study a precise procedure for the Thermo-mechanical fatigue life assessment of hot diesel engine components is investigated. In high cycle fatigue assessment, the effect of mean stress is considered using Haigh diagram. Different LCF life assessment methods have been used to investigate LCF life and their results are compared to each other. Almost all of the engine components are subjected to proportional or non-proportional multiaxial loadings. The non-proportional loading leads to an additional cyclic hardening in the material. Critical plane LCF theories are appropriate for consideration of the additional cyclic hardening effect on the fatigue life reduction of the component. Effect of high cycle fatigue on low cycle fatigue life reduction is also studied. Finally, the discussed thermo-mechanical fatigue life assessment process is used to estimate thermo-mechanical fatigue life of a diesel engine piston.