Fatigue design of welded aluminum rectangular hollow section joints

Norwegian University of Science and Technology, Department of Structural Engineering, Rich. Birkelandsvei 1a, N-7034 Trondheim, Norway
Engineering Failure Analysis (Impact Factor: 1.13). 04/1999; DOI: 10.1016/S1350-6307(98)00025-9

ABSTRACT Fatigue design methods for welded aluminum joints are reviewed, including various approaches to fatigue life estimation currently adopted in design codes across a range of industrial applications. The applicability of these established methodologies to the fatigue design of automotive space frame structures is critically assessed. The hot spot stress method is identified as the most promising in terms of providing a coherent and comprehensive approach to design. Particular problems related to implementation are considered such as failure sites and determination of appropriate stress concentration factors from physical models, finite element calculations or parametric equations. Preliminary results from finite element stress analyses and fatigue tests are also presented for rectangular hollow sections welded in a T-joint configuration. Recommendations are made for a design methodology for welded rectangular hollow-section joints in aluminum space frames, including use of a single hot spot S–N curve.

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    ABSTRACT: The aim of this work is to present an engineering method based on linear elastic finite element (FE) analyses oriented to fatigue strength assessments of fillet-welded joints made of steel or aluminium alloys and subjected to mode I loading in the weld toe region where fatigue cracks nucleate. The proposed approach combines the robustness of the notch stress intensity factor approach with the simplicity of the so-called ‘peak stress method’. Fatigue strength assessments are performed on the basis of (i) a well-defined elastic peak stress evaluated by FE analyses at the crack initiation point (design stress) and (ii) a unified scatter band (design fatigue curve) dependent on the class of material, i.e. structural steel or aluminium alloys. The elastic peak stress is calculated by using rather coarse meshes with a fixed FE size. A simple rule to calculate the elastic peak stress is also provided if a FE size different from that used in the present work is adopted. The method can be applied to joints having complex geometry by adopting a two-step analysis procedure that involves standard finite element (FE) models like those usually adopted in an industrial context. The proposed approach is validated against a number of fatigue data published in the literature.
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    ABSTRACT: In this paper the results of a numerical-experimental study aimed to evaluate the fatigue be- haviour of welded joints of Al-alloy bike frames are presented. The stress field in the frame was calculates by means of a finite element model, set up to identify the critical points for fa- tigue failure in dependence on the typical performances required in service. Taking into ac- count the loads originated in the joint by the rest of the structure, a laboratory testing device was simulated by Finite Element Modelling (FEM) and developed to test the weld joint at stress conditions similar to those experienced in service. By using this testing configuration the fatigue characterisation of the welded joints with different geometry was carried out.
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    ABSTRACT: In this study, fatigue tests to obtain S-N curves and FE analyses to obtain structural stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curve of load carrying joint to that based on hot spot stress. As a result, the S-N curve of load carrying joint based on hot-spot stress was almost exactly coincided with that of non load-carrying joint based on nominal stress. So we have conducted that the fatigue strength of a welded joint with different geometry from the non stress distribution along the expected crack path.
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