Thermal-fatigue performance assessment of components and systems is challenging due to the inherent complexities in mechanical and thermal loadings, material inhomogeneity, manufacturing inconsistency etc. Among all of possible failure modes, the fatigue and thermal-fatigue failures at stress raisers are of particular importance because they consist of the majority of failure modes in vehicle components and systems. Stress raisers in components include the welds, notches, and other material and geometry discontinuities. Durability and reliability assessment of stress raisers is difficult in testing because the true deformation at a stress raiser often cannot be directly measured. Many approximate engineering approaches have been developed over the last decades, but further fundamental understanding of the problems and the development of more effective engineering methods are still strongly demanded. In this paper, several new concepts and engineering testing approaches are developed and introduced with the emphasis on thermal-fatigue assessment of welded structures.