Fatigue design of welded aluminum rectangular hollow section joints
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 hot spot stress approach is usually adopted in the fatigue design and analysis of tubular welded joints. To apply the hot spot stress approach for fatigue evaluation of long span suspension bridges, the FEM is used to determine the hot spot stress of critical fatigue location. Using the local finite element models of the Tsing Ma Bridge, typical joints are developed and the stress concentration factors are determined. As a case for study, the calculated stress concentration factor is combined with the nominal representative stress block cycle to obtain the representative hot spot stress range cycle block under traffic loading from online health monitoring system. A comparison is made between the nominal stress approach and the hot spot stress approach for fatigue life evaluation of the Tsing Ma Bridge. The comparison result shows that the nominal stress approach cannot consider the most critical stress of the fatigue damage location and the hot spot stress approach is more appropriate for fatigue evaluation.Structural Engineering & Mechanics 01/2005; · 0.80 Impact Factor
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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: 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.Fatigue & Fracture of Engineering Materials & Structures 06/2008; 31(5):346 - 369. · 0.86 Impact Factor