A computational approach to thermomechanical fatigue life predictions of dissimilarly welded superheater tubes

Doctoral Thesis / Dissertation from the year 2012 in the subject Engineering - Mechanical Engineering, grade: cum laude (gut), Karlsruhe Institute of Technology (KIT), course: Mechanical Engineering, language: English, abstract: The primary focus of this work is to investigate the influence of residual stresses on thermomechanicalfatigue (TMF) ...

Doctoral Thesis / Dissertation from the year 2012 in the subject Engineering - Mechanical Engineering, grade: cum laude (gut), Karlsruhe Institute of Technology (KIT), course: Mechanical Engineering, language: English, abstract: The primary focus of this work is to investigate the influence of residual stresses on thermomechanicalfatigue (TMF) life predictions. Both experimental and numerical methodshave been adapted in order to predict the lifetimes of dissimilarly welded superheater tubingin power plants. The fatigue behavior and lifetime predictions of such componentsare complicated at high temperatures since a complex interaction between thermally activatedtime-dependent processes are involved. At the same time, components that operateat elevated temperatures are often subjected to transient temperatures due to start-up andshut-down where thermally induced cyclic stresses can occur. The superposition of thermaltransients with mechanical load cycles along with unequal heating of parts of a componentresult in a complex evolution of damage, leading to TMF failure of the component. To addto the complexity, the degradation mechanisms relevant to welded power plant componentscan be accelerated by the presence of residual stresses.