Fitness for purpose assessment of a structural aluminium railway car body component

In the present study a fitness for purpose assessment has been performed for a car body floor plate of a high speed railway vehicle made from thin walled AlMgSi 0.7 (EN AW 6005 T6) extrusions. The extrusions investigated have been MIG welded using AlSi5 wire to form the vehicle floor structure. The assessment takes into account welds with typical defects which can either be caused by the manufacturing process or loading during service. Local material properties such as strength and deformation values, fracture toughness and cyclic crack growth rates of the base and the weld metal as well as of the heat-affected zone are used. By comparison of the local stress strain state (function of geometry, defect state and external loading condition) and the local material resistance weld defects such as lack of fusion, hot cracks or grain boundary openings are evaluated and the consequences for the structure are assessed.