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Open AccessArticle

Fatigue Strength Assessment of Welded Mild Steel Joints Containing Bulk Imperfections

1
Christian Doppler Laboratory for Manufacturing Process based Component Design, Chair of Mechanical Engineering, Montanuniversität Leoben, 8700 Leoben, Austria
2
Kyushu University, 819-0395 Fukuoka, Japan
3
Fraunhofer Institute for Mechanics of Materials IWM, 79108 Freiburg, Germany
4
Department of Applied Mechanics, School of Engineering, Aalto University, 02150 Espoo, Finland
*
Author to whom correspondence should be addressed.
Metals 2018, 8(5), 306; https://doi.org/10.3390/met8050306
Received: 29 March 2018 / Revised: 20 April 2018 / Accepted: 23 April 2018 / Published: 29 April 2018
(This article belongs to the Special Issue Fatigue and Wear for Steels)
This work investigates the effect of gas pores, as bulk imperfections, on the fatigue strength of welded mild steel joints. Two test series containing different butt joint geometries and weld process parameters are included in order to achieve two variable types of pore sizes. Based on the √area-parameter by Murakami, the test series can be grouped into imperfections exhibiting √area < 1000 µm and √area > 1000 µm. Fatigue tests at a load stress ratio of R = 0.1 are performed, which act as comparison for the subsequent fatigue estimation. To assess the fatigue resistance, the approaches by Murakami, De Kazinczy, and Mitchell are utilized, which highlight certain differences in the applicability depending on the imperfection size. It is found that, on one hand, Murakami’s approach is well suitable for both small and large gas pores depending on the applied model parameters. On the other hand, the fatigue concepts by De Kazinczy and Mitchell are preferably practicable for large defects with √area > 1000 µm. In addition, the method by Mitchell incorporates the stress concentration factor of the imperfection, which can be numerically computed considering the size, shape, and location of the gas pore, as presented in this paper. View Full-Text
Keywords: fatigue strength; welded joints; gas porosity; fatigue assessment fatigue strength; welded joints; gas porosity; fatigue assessment
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MDPI and ACS Style

Leitner, M.; Murakami, Y.; Farajian, M.; Remes, H.; Stoschka, M. Fatigue Strength Assessment of Welded Mild Steel Joints Containing Bulk Imperfections. Metals 2018, 8, 306.

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