A MASTER THESIS ON THE PARAMETRIC WELD-DESIGN EVALUATION IN CRANE LOADER BODY USING NOTCH STRESS ANALYSIS

Abstract: This thesis has been conducted at Cargotec Sweden AB as a case study on the loader body of the HIAB XS 144 crane. The loader body is the innermost part in the cranes arm-system and its fatigue life is critical to the operational life of the whole crane. Welding is the main joining process in Cargotec’s cranes and are often a limiting factor when it comes to fatigue life. The weld joining the column to the loader body is carrying the whole crane moment. Previous testing has shown that this weld often limits the fatigue life of the loader body, it has thus been evaluated. Weld fatigue life is affected by a large amount of parameters. To pinpoint the parameters mainly affecting the weld fatigue life and to understand their influence, calculations have been organized using factorial design. The evaluation has been carried out using 3D finite element calculations utilizing sub-modelling to calculate local stresses in the weld notches. Different parameters have been evaluated based on their influence on the local notch stresses. To estimate stresses from the evaluated parameters, regression equations have been fitted. The effective notch method has been used to estimate weld fatigue life. The evaluation has shown that a butt-weld design with root-support, only being welded from the outside of the loader body, as used on some other crane models, could not provide a robust design for the XS 144 crane. The evaluation could also point out several critical parameters that need to be considered when using such design. Apart from the local weld geometry, plate thickness, plate angle, material offset and thickness in the casted column were mainly affecting the weld notch stresses.