In reality most welded components are loaded with a combination of different variable forces and moments which often cause a state of multiaxial stress in the fatigue critical areas of the weldment. If the multiaxial loading is nonproportional, conventional hypotheses are not able to give a satisfying lifetime prediction. This investigation is a cooperation of three German research institutes to build an experimental database for the verification of different concepts of lifetime prediction. In accordance with former investigations, a flange-tube connection made of steel P460 is used. The test program is divided into constant amplitude and variable amplitude tests. The ratio between the nominal bending and shear stress is 1. The ratio between the local shear and normal stress at the critical point is 0.6. For the variable amplitude tests, a Gaussian standard is used.

A lifetime prediction software for multiaxial state of cyclic stress was developed. The software has a modular structure and allows calculations with different hypotheses and methods. The calculations are based on the local elastic stresses. This is an acceptable method for high-cycle fatigue. The failure criteria “critical plane approach” and “integral damage approach” are used in the software. Lifetime predictions for the flange-tube connection were performed using various hypotheses and concepts. In this work, one type of calculation, the integral approach with elementary Miner's Rule and damage sum D = 1, is illustrated. The calculations correspond well with the experimental results.