Fatigue design of welded joints from the wrought magnesium alloy AZ31 by the local stress concept with the fictitious notch radii of rf= 1.0 and 0.05 mm

• Published in: International journal of fatigue Vol. 30; no. 12; pp. 2210 - 2219
• Main Authors: KARAKAS, O, MORGENSTERN, C, SONSINO, C. M
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier 01.12.2008
• Subjects: Applied sciences; Exact sciences and technology; Fatigue; Joining, thermal cutting: metallurgical aspects; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Welding; Local stress concept; Welding; Mechanical properties; Fatigue; Wrought alloy; Aluminium; Fictitious radius; Steel; Design; Welded joints; Magnesium base alloys; Welded joint; Magnesium
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2008.05.017

Investigations were carried out with three different types of MIG- and TIG-welded joints of the magnesium alloy AZ31(ISO-MgAl3Zn1): fully or partially penetrated butt welds, transversal stiffeners. The evaluation of the results showed that the local stress concept using the fictitious notch radius of rf = 1.0 mm can be applied to magnesium welded joints from plates with thicknesses t 5 mm independently of the weld geometries. Design curves are proposed for different stress ratios, i.e. R = -1 as well as 0 and 0.5, which allow the consideration of residual stresses as well as load induced mean-stresses. The results also permit the suggestion of Deltasigma = 28 MPa for rf = 1.0 mm as FAT-value in the IIW-Fatigue Design Recommendations. Further, the FAT-value Deltasigma = 73 MPa is also derived for the fictitious radius of rf = 0.05 mm to be applied to welded thin magnesium joints (t < 5 mm). These FAT-values are compared with data already known for steel and aluminium joints. A linear relationship between the FAT-values and the Young's modulus is determined.