Mechanical Reliability

Fatigue life prediction of bonded steel joints under multiaxial loading with phase shift, variable mean stress and variable amplitudes (LAMbdA)


In recent years, many innovative and reliable approaches for the fatigue life assessment of bonded steel joints have been developed. Such approaches usually concentrate on the evaluation of the fatigue strength under uniaxial loads with constant amplitudes. The challenge is to consider further influences such as multi-axial stress starts with alternating principal stress directions, mean stresses and variable amplitudes in the fatigue life assessment. This will enhance the evaluation of the behavior of bonded joints under realistic loads.

As a part of the Roadmap Bonding Technology, this project should on the one hand provide insights on the effects of variable influences on adhesive bonds. On the other hand, it should provide a performant evaluation method for the fatigue life of steel bonded joints that is relatively easy to implement. Finally, especially small and medium-sized enterprises should be given access to the application and design of bonded steel joints.


The resulting methodology should be capable of estimating the fatigue life under complex loading conditions with sufficient accuracy and, at the same time, be implemented in commercial software.


In order to better determine the effects of the individual influences on the fatigue performance of bonded steel connections, an extensive test program is being carried out. Four specimen geometries are tested at different load conditions, phase shifts and load-time signals. Simultaneously, the fatigue life of the bonded joints will be assessed with FE models. Therefore existing numerical approaches will be used and modified if required. Based on validation tests, the accuracy of the estimates of the newly developed numerical approaches will be verified.

Picture: Fachgebiet SAM


Research Instituts:

  • Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM)
  • University of Kassel, Department of Mechanics (IfM), Faculty of Mechanical Engineering
  • University of Paderborn, Laboratory for material and joining technology (LWF)
  • Technical University (TU) of Darmstadt, Research group System Reliability, Adaptive Structures, and Machine Acoustics (SAM)

AiF-project IGF 21.112, FOSTA project P1427
The Research Association for Steel Application FOSTA e. V.
Duration: 30 month, 01.06.2020 until 31.12.2022


Dr.-Ing. Jörg Baumgartner
Tel.: ++49-6151-705-474