Modelling Fatigue in Adhesively Bonded Joints
Fatigue is widely recognised as one of the most common causes of mechanical failure and hence the issue of fatigue in bonded joints must be addressed if adhesives are to find wider usage in structural applications. Fatigue failure is difficult to predict
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Modelling Fatigue in Adhesively Bonded Joints Ian A. Ashcroft and Andrew D. Crocombe
Abstract Fatigue is widely recognised as one of the most common causes of mechanical failure and hence the issue of fatigue in bonded joints must be addressed if adhesives are to find wider usage in structural applications. Fatigue failure is difficult to predict accurately and fatigue in bonded joints is complicated by the multi-component nature of bonded joints and by the complex stress distributions and material behaviour. Various methods of modelling the fatigue behaviour of bonded joints have been proposed, varying in complexity, applicability and degree of empiricism. The aims of the models are either to predict the number of load cycles until a certain event occurs (such as macro-crack initiation or complete failure) or to predict the rate of change of crack length (or some other measure of damage) as a function of cycles. In this chapter the main approaches to modelling fatigue in adhesive joints are outlined and examples given of the application of each approach. It is seen that there are many practical modelling routes, the choice being dependent on what is required and the availability of resources, data and expertise. However, it cannot be said at present that there is a generally applicable method of modelling fatigue in bonded joints that is robust, reliable and mechanistically accurate. However, the further development of advanced computational methods, such as finite element analyses incorporating progressive damage, and increased understanding of the mechanisms of fatigue in bonded joints will continue to provide drivers for improved modelling methods.
Ian A. Ashcroft Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK, e-mail: [email protected] Andrew D. Crocombe Division of Mechanical, Medical and Aerospace Engineering, School of Engineering, University of Surrey, Guildford, GU2 5XH, UK, e-mail: [email protected]
ยจ L.F.M. da Silva, A. Ochsner (eds.), Modeling of Adhesively Bonded Joints, c Springer-Verlag Berlin Heidelberg 2008
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Ian A. Ashcroft, Andrew D. Crocombe
7.1 Introduction Fatigue, in an engineering sense, is the failure of a structure under a repetitive or cyclic loading regime in which the loads involved are considerably lower than those involved in instantaneous, or quasi-static, failure. Fatigue is a significant subject for study for many reasons. Firstly, fatigue loading is seen in nearly all major engineering structures, e.g. aircraft, ships, cars, buildings, bridges, as well as in many nonengineering applications, such as sports equipment and even human parts, such as knees. Secondly, it can result in sudden catastrophic failure after years of apparently safe service. Long periods can be spent in the initiation phase of fatigue damage, in which there may be no outward signs of damage, failure can then quickly accelerate in the final stages. Fatigue damage can be initiated or accelerated by many
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