Fatigue strength of spot welded stainless steel components for railway carriages under operational loading conditions. Final report

The objectives of this project have been the following: Specification, for austenitic stainless steel, of better conditions of surface sheet hardness from the point of view both for the fatigue behaviour and for the evaluation of sensitivity notch effect. Fatigue strength evaluation of spot welded stainless structures, in terms of analytic method and data. Results: For the steel AISI 301(1.4318) cold sheet steel in annealed and full hard surface condition the sensitivity notch parameter has been found equal to q=0.5, for stress concentration design factor equal or less value K(t) <= 2.0. Whereas for middle hard surface level (1/8 and 1/2 hard) the sensitivity notch has been higher than q>0.5, moreover this value depending on both of the hard surface level and of the notch stress concentration design factor. The experimental and numerical approaches have been developed by CSM and LBF taking into account the easy to use way in term of software and hardware resources. The experimental fat igue life results have been obtained from overlap joint welded spot stressed under fatigue tension, girder boxes with more spots stressed also under shear fatigue loads, omega specimens stressed under multiaxial fatigue and random fatigue loads. The radial stress as damage stress in fatigue of the spot welded has been evaluate by a numerical way and the relationship with the applied loads has been found too. The results of the fatigue life obtained can be used for the fatigue life estimation of complicate spot welded structures from stainless steels under complex multiaxial loading and operational conditions.