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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 86
Edited by: B.H.V. Topping
Paper 145

Expected Variations in Stress in Aluminium Lap Joints when Designing to Eurocode 9

J.W. Bull1, C.H. Woodford2 and E.A. Charles3

1School of Civil Engineering and Geosciences, 2Information Systems and Services
3Advanced Chemicals & Materials Analysis
Newcastle University, Newcastle upon Tyne, United Kingdom

Full Bibliographic Reference for this paper
J.W. Bull, C.H. Woodford, E.A. Charles, "Expected Variations in Stress in Aluminium Lap Joints when Designing to Eurocode 9", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 145, 2007. doi:10.4203/ccp.86.145
Keywords: fatigue life, aluminium, weld, lap joints, Eurocode 9, finite elements.

This research considers the design of aluminium and aluminium alloy structures in accordance with Eurocode 9 [1,2]. More specifically, the maximum deflection, stress and stress range in, and the fatigue life of, an aluminium weldment.

Eurocode 9 covers a range of 3000, 4000, 5000, 6000, 7000 and 8000 series aluminium alloys used in the design of structures [1,2]. However, if other available aluminium and aluminium alloys are used, the designer must know what change in resulting deflections, stresses and fatigue life could be expected by designing to Eurocode 9 [1,2,3]. In References [1] and [4], tables are given for the selection of weld filler metal to be used with the parent aluminium alloys being joined. In both references the Young's modulus value of 70000MPa is used for the parent metal and for the weld filler metal.

Weld filler metal can be chosen to give maximum weld strength, maximum resistance to corrosion or to reduce weld cracking. However, there is insufficient information concerning the Young's modulus of the weld filler metal. This lack of information significantly affects the deflections and stress results when using finite element analysis, as required by Eurocode 9, as the Young's modulus is an analysis requirement [1,2].

The value of the Young's modulus is dependent upon the aluminium alloy combination, typically ranging from 60800MPa to 71900MPa [3]. Further, as the weld filler metal can be considered as a casting, its Young's modulus could range from 69000MPa to 88000MPa [3]. This research considers the effects of using these alternative Young's moduli to determine the deflections, stresses and fatigue life of the weldment.

The finite element analysis assessed the output from six loads individually applied to the weldment, with the magnitude of the load being decided by the maximum deflection produced. The loads were tension or compression in the longitudinal direction, an upward or a downward load in the vertical direction, a transverse load in the lateral direction and torsion about the longitudinal axis.

The results showed that using the alternative values of Young's modulus, the maximum deflections were increase by 15.39%, and the maximum longitudinal stress and principal stress were increased by 12.65% and 11.58% respectively. For fatigue life, where the stress range is the determining factor, the reduction was between 26% and 39% depending upon the appropriate permitted class being assessed [2].

EN 1999-1-1, "Design of aluminium structures - Part 1-1: General structural rules", BSI, London, United Kingdom, 2006.
EN 1999-1-3, "Design of aluminium structures - Part 1-3: Structures susceptible to fatigue", BSI, London, United Kingdom, 2007.
Aluminium Federation, "The properties of aluminium and its alloys", 9th edition, Aluminium Federation, Birmingham, United Kingdom, 2003.
BS8118, "Structural use of aluminium", BSI, London, United Kingdom, 1991.

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