Structural Hot-Spot Stress Approach to Fatigue Analysis of Welded Components by Erkki Niemi Wolfgang Fricke & Stephen J. Maddox

Author:Erkki Niemi, Wolfgang Fricke & Stephen J. Maddox
Language: eng
Format: epub
Publisher: Springer Singapore, Singapore

4.5 Use of Relatively Fine Element Meshes

Use of a relatively fine element mesh is recommended for the following:in complex details and details showing a high stress gradient close to the hot-spot;

when evaluating the structural hot-spot stress by through-thickness linearization or at a single point close to the hot-spot (surface stress extrapolation is possible as well);

when comparing FEA results and measured stresses.

4.5.1 Solid Element Modelling

Solid element modelling allows the weld geometry to be considered, as illustrated in Fig. 4.2. Since the extrapolation method uses nodal stresses 0.4t and 1.0t from the weld toe when applied to Type “a” hot spots, the first element length should be no more than 0.4t and the second element length no more than 0.6t in the loading direction, Fig. 4.6. For Type “b” hot spots, the required maximum element sizes are shown in Fig. 4.3c. Also the element width should be smaller than in coarse models, see Table 4.1. If a refined mesh is used, it is generally recommended to subdivide the mesh shown in Fig. 4.3(a, c) in both directions, i.e. in the direction of stress extrapolation as well as in the thickness direction.

Fig. 4.6An example of simple solid element modelling of a bracket welded on a plate. The darkest face is a symmetry plane

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