Original scientific paper
Potential Fatigue Strength Change of Welds Due to Repair Welding
Vladimir GLIHA
; Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia
Ivan SAMARDŽIĆ
; Mechanical Engineering Faculty, J.J. Strossmayer University of Osijek) Trg Ivane Brlić-Mažuranić 2, Slavonski Brod, Croatia
Tomaž VUHERER
; Faculty of Mechanical Engineering, University of Maribor, Maribor, Slovenia
Abstract
The fatigue strength of welds in polycrystalline metals depends on the hardness, the size of defects and grains in the areas of the highest stress and on the level of welding residual stresses. Changes of residual stresses and hardness were experimentally determined on a weld which was repaired. Besides, steel samples with the microstructure of martensite were used with the intention to assess effects of residual stresses and grain size to the fatigue strength of welds. The samples were prepared using either thermal cycle simulator or laboratory furnace and water quenching. The used methods of microstructure preparation result in different surface residual stresses. Specimens for the fatigue limit measurement were prepared either defect-free or with artificial defects. Artificial surface defects were small in comparison with the size of grains. The defects were made by drilling small holes and indenting with the Vickers pyramid. The results show that tensile residual stresses and coarser grains lower the fatigue limit of steel and vice versa. Enhancement of welding residual stresses caused by repair welding leads to fatigue strength reduction of welds while hardening of weld materials leads to its increase.
Keywords
Artificial defect; Base-metal - BM; Coarse grain; Crack initiation; Fatigue crack; Fatigue limit; Fatigue strength; Hardness; Heat-affected zone - HAZ; Re-fined grain; Repair welding; Residual stresses - RS; Small defects; Weld; Weld metal- WM
Hrčak ID:
42525
URI
Publication date:
26.2.2009.
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