Corrosion fatigue of welded aluminium vehicle structures under constant and variable amplitude loadings

The structural durability design of welded vehicle structures of aluminium also comprises the aspect of corrosion fatigue, especially for the experimental and numerical proof of chassis components that are submitted to salt corrosion in winter. Investigations carried out with specimens and components show that the decrease of fatigue strength under cyclic salt spray corrosion is not as pronounced under spectrum loading as under constant amplitude loading. This effect on spectrum fatigue strength and life, in turn, allows lightweight design of welded aluminium structures; knowledge and application of constant amplitude fatigue behaviour only would result in thicker cross-sections in design. Recommendations are given for the consideration of the different fatigue strength reductions arising from cyclic salt spray corrosion under constant and variable amplitude loadings and for the assessment of fatigue life under spectrum loading by cumulative damage calculations.