Issue 38

E. Shams et alii, Frattura ed Integrità Strutturale, 38 (2016) 114-120; DOI: 10.3221/IGF-ESIS.38.15 114 Focussed on Multiaxial Fatigue and Fracture Fatigue of weld ends under combined in- and out-of-phase multiaxial loading E. Shams Technische Universität Darmstadt, Materials Mechanics Group, Franziska-Braun-Str. 3, D-64287 Darmstadt, Germany shams@wm.tu-darmstadt.de M. Vormwald Technische Universität Darmstadt, Materials Mechanics Group, Franziska-Braun-Str. 3, D-64287 Darmstadt, Germany vormwald@wm.tu-darmstadt.de A BSTRACT . Weld start and end points are fatigue failure sensitive locations. Their fatigue behaviour especially in thin sheet structures under multiaxial load conditions is not sufficiently explored so far. Therefore, a research project was initiated to increase the knowledge concerning this topic, which is of special interest in the automotive industry. In the present study, fatigue tests on welded joints were conducted. In the numerical part of the study, notch stresses were calculated with an idealised weld end model. A numerical method which combines the geometrical and statistical size effect to an integrated approach was used, in order to consider the size effects. K EYWORDS . Weld ends; Fatigue; Notch stress; Size effect; Multiaxial. Citation: Shams, E., Vormwald, M., Fatigue of weld ends under combined in- and out-of- phase multiaxial loading, Frattura ed Integrità Strutturale, 38 (2016) 114-120. Received: 18.05.2016 Accepted: 15.06.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION elded structures often contain weld start and end points, which are the critical location for the failure. Normally, fatigue design of welded components proceeds from S – N curves (fatigue strength versus number of cycles). Concerning weld start and end points, the knowledge of S - N curve parameters is limited to either normal [1-5] or shear [6] stressed structures. In these investigations, dealing only with uniaxial loading conditions, geometrically idealised weld end models with concept radii of r normal = 0.20 mm respectively r shear = 0.05 mm were created. These models base on the real weld geometry obtained by means of high-precision 3D-scanner. In connection with these models, recommendations for determining notch stresses by applying the finite element (FE) method were developed. Nowadays, different S - N curves are assigned to weld toe and weld root failure scenarios induced by normal and shear stresses. Further studies have shown, that an evaluation of both stress gradient and expansion of the notch area realizes the standardisation of S - N curves belonging to various structural shapes and sizes [4-5]. In the framework of the “Numerical Method regarding Size Effects for Standardisation of Wöhler curves” (NuMeSiS), a standardised stress is to be derived by W