No abstract

The objective of this research work is to reproduce in a test specimen, the fatigue failure that occurs in a damaged section of a structure. There is a structural problem, that is, the presence of a fracture at a certain point in the structure of the bus, starting at this point and growing progressively, causing damage. The steps of a methodology were applied to physically reproduce the fatigue failure in a representative specimen of a section of the bus structure, where the failure is located and up to the instrumentation of the testing machine and performance of the fatigue test. Subsequently, the results are analyzed and conclusions are made based on the results obtained in the laboratory test.

This paper presents results of research on the propagation of fatigue cracks in structural steel sheet, subjected to a MIG welding process. The study was conducted on rectangular test pieces with 62.5 x 60 mm and 2 mm thick, MIG welded and non-welded. Samples were tested for fatigue crack propagation at the base material and welded metal. The results show a crack stop in the heat affected zone (HAZ), requiring greater amplitude of the stress intensity factor (KI) so the crack could propagate in a stable manner. Results indicate that the combination of adequate microstructure and residual stress in the HAZ are those factors which can stop the advance of the crack in MIG welded material.