Welded joints are widely employed in engineering field and they are always the starting points of fatigue damage. Because of the unfavorable material and geometry characters, as well as initial welding defects, the fatigue damage evaluation of welded joints is an important and troublesome issue for engineers. In this article, multiaxial fatigue space theory proposed by the first author for smooth specimens is extended for the fatigue damage assessment of welded joints, by adopting nominal stress approach. The fatigue test data with different materials, loading paths, and welded joints geometries are used to validate the capability of this theory. The result indicates a strong parallelization between predicted life and experimental life, with a favorable prediction error and beneficial error distribution. It can be concluded that multiaxial fatigue space theory is a useful method for fatigue damage assessment of welded joints with the help of nominal stress approach.

The multiaxial fatigue character of high-speed railway brake disc thermomechanical damage is studied in this work. Although the amplitude and distribution of temperature, strain and stress are similar with uniform and rotation loading methods, the multiaxial behavior and out-of-phase failure status can only be revealed by the latter one. With the help of a multiaxial fatigue model, fatigue damage evaluation and fatigue life prediction are implemented, the contribution of uniaxial fatigue parameter, multiaxial fatigue parameter and out-of-phase failure parameter to the total damage is discussed, the damage will be underestimated without the consideration of multiaxial characters and out-of-phase failure status. It can be announced that brake disc fatigue belongs to the type of multiaxial thermomechanical fatigue. The results of this work can help to understand the damage mechanism of high-speed railway brake disc, and provide theoretical foundation for design optimization from the perspective of multiaxial thermomechanical fatigue resistance.