Critical distance approach for the fatigue strength assessment of magnesium welded joints in contrast to Neuber's effective stress method

• Published in: International journal of fatigue 2018-07, Vol.112, p.21-35
• Main Authors: Karakaş, Ö., Zhang, G., Sonsino, C.M.
• Format: Article
• Language: English
• Subjects: Butt welds; Critical distance; Effective stress; Fatigue; Fatigue life; Fatigue strength; Finite element analysis; Finite element method; Magnesium; Magnesium welds; Materials fatigue; Metal fatigue; Notch stress; S N diagrams; Specimen geometry; Stress; Stresses; Welded joints; Welding
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2018.03.004

•Three different magnesium welded joints were evaluated.•Calculations were based on the critical distance method.•The critical distance for magnesium welded joints was determined as a=0.06 mm.•Scatters of critical distance and stress averaging methods showed similar results. In the present paper, the critical distance method was used to evaluate the fatigue behaviour of magnesium welded joints. The main objective of the study was to determine the applicability of the critical distance method and to compare the findings with Neuber’s stress averaging method. To realise this objective, experimental data, determined for three different weld geometries under three different stress ratios, were evaluated. Stress distributions of each specimen geometry, i.e. full penetrated butt weld, incomplete penetrated butt weld and transversal stiffener, were acquired by finite element analyses and were used to calculate effective stresses. The critical distance a is a material constant, which is independent of the used notch radius rref. For its determination, an identification process was used where the scatter of the resulting S-N line of effective stress is minimised. The critical distance a=0.06 mm was determined versus the microstructural length ρ∗=0.12 mm.