PSI - Issue 23

Barbara Nasiłowska et al. / Procedia Structural Integrity 23 (2019) 577– 582 Nasiłowska B./ Structural Integrity Procedia 00 ( 2019) 000 – 000

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95 and 85 % (at the level of nominal stress amplitude Δσ an = 490, 438 and 375 MPa) of a total number of cycles to failure N f . The less advantageous development of fatigue fractures occurred in the specimens made with TIG method. The tests showed that after reaching approximately 50% of a total number of cycles to failure N f , an initiation of fatigue fractures N i occurred. Mechanical shot peening of the surface layer of the joint welded with TIG method was particularly favourable since an increase in not only a total number of cycles to failure but also in a number of cycles to fracture initiation was achieved. Introduction of favorable structural changes during the surface shot peening resulted in increasing the fracture initiation time and shortening the fatigue fracture time, which occurred after approximately 70% of a number of cycles to failure. Non-shot peened joints welded with a laser beam were characterized with a longer time of fatigue fractures development initiation than joints welded with TIG method by 20%. It is of special importance during service of chemical installations, where any lack of tightness lead to leakage of hazardous substances. Period of fatigue fracture initiation in joints welded with a laser beam after shot peening of the surface layer run similarly as in the case of the parent material. After approximately 85% of a total number of cycles to failure, the fracture initiation occurred. Summary The greatest number of cycles to fatigue fractures initiation was in the case of the parent material (90%) and, subsequently, joints welded with a laser beam – shot peened (84%), joints welded with a laser beam – non-shot peened (73%), joints welded with TIG method – shot peened (72%) and joints welded with TIG method – non-shot peened (49%). The results of the tests, in terms of fatigue life, clearly show that the best quality weld was that made with a laser beam and additionally subjected to surface shot peening. Surface strengthening caused squeeze of the austenite grains in the subsurface layer, which resulted in an advantageous distribution of compressive stress. The initiation and development of fatigue fracturing was favourably delayed and development of main fracturing was accompanied by secondary subsurface fractures located parallel to the specimen plane. Reference Cichański , A., 1996. Problemy z wyznaczaniem wartości współczynnika kształtu dla obciążeń zmiennych . Materiały konferencyjne XVI Symp ozjum Zmęczenia i Mechaniki Pękania Materiałów Konstrukcji. Bydgoszcz-Pieczyska, 43-46. Fazzini, P.G., Belmonte, J.C., Chapetti, M.D., Otegui, J.L., 2007. Fatigue assessment of a double submerged arc welded gas pipeline International. Journal of Fatigue. 29,1115-1124. Gao, Y.K. 2008. Influence of deep-nitriding and shot peening on rolling contact fatigue performance of 32Cr3MoVA steel, J Mater Eng Perform. 17, 455-459. Hassani-Gangaraj, S.M, Moridi, A., Guagliano, M., Ghidini, A., Boniardi, M., 2014. The effect of nitriding, severe shot peening and their combination on the fatigue behavior and micro-structure of a low-alloy steel, 9th Fatigue Damage of Structural Materials Conference. International Journal of Fatigue, 62, 67-76. Hatamleh, O., 2009. A comprehensive investigation on the effects of laser and shot peening on fatigue crack growth in friction stir welded AA 2195 joints. International Journal of Fatigue. 31 (5), 974-988. Kocańda , D., 1996. Analiza rozwoju krótkich pęknięć zmęczeniowych . rozprawa habilitacyjna. WAT. Warszawa, in Poland. Kocańda , S., 1985. Zmęczeniowe pękanie metali, WNT . Warszawa, in Poland. Palmer, A. C., King R. A. 2008. Subsea Pipeline Engineering, Penn Well Books. 624. Nasiłowska , B., Bogdanowicz Z., Wojucki M., 2015. Shot peening effect on 904L welds corrosion resistance. Journal of Constructional Steel Research. 115. 276-282. Nakonieczny, A., 2002. Dynamiczna powierzchniowa obróbka plastyczna – kulowanie (shot peeling), Wydawnictwo IMP. Takakuwa, O., Soyama, H., 2012. Suppression of hydrogen-assisted fatigue crack growth in austenitic stainless steel by cavitation peening international. Journal of Hydrogen Energy. 37, 5268-5276. Terres, M.A., Laalai, N., Sidhom H., 2012. Effect of nitriding and shot-peening on the fatigue behavior of 42CrMo4 steel: experimental analysis and predictive approach. Mater Des. 35, 741-748. Wei, T., Ye, L., Clar, G., Mai, Y., 2002. Laser shock processing and its effects on microstructure and properties of metal alloys. International Journal of Fatigue. 24, 1021-1036.