Advanced notch strain based calculation of S–N curves for welded components

• Development of a novel calculation of S–N curves for welded joints.
• Elastoplastic analysis based on material properties and the Local Strain Approach.
• Consideration of the residual stress state and mean stress relaxation effects.
• Comprehensive experimental verification on welded automotive components.
• Verification for various load configurations and load ratios.

The present paper contains an advanced elastic–plastic calculation procedure of S–N curves of welded joints, taking into account solely standardized cyclic material data. The methodology used is based on the Notch Strain Approach, whereby advanced proposals regarding the means stress relaxation, mean stress sensitivity and residual stress state are introduced. The calculation accuracy of the proposed concept has been verified by means of experimentally determined S–N curves of motor truck’s axle casings, providing welds with explicit terminations (weld starts and ends) and subjected to cyclic loading at different load ratios and load configurations. Very good agreement between calculated and experimentally determined fatigue lives has been observed in all cases investigated.