Integrating the finite element method and genetic algorithms to solve structural damage detection and design optimisation problems

This thesis documents fundamental new research in to a specific application of structural box-section beams, for which weight reduction is highly desirable. It is proposed and demonstrated that the weight of these beams can be significantly reduced by using advanced, laminated fibre-reinforced composites in place of steel. Of the many issues raised during this investigation two, of particular importance, are considered in detail; (a) the detection and quantification of damage in composite structures and (b) the optimisation of laminate design to maximise the performance of loaded composite structuress ubject to given constraints. It is demonstrated that both these issues can be formulated and solved as optimisation problems using the finite element method, in which an appropriate objective function is minimised (or maximised). In case (a) the difference in static response obtained from a loaded structure containing damage and an equivalent mathematical model of the structure is minimised by iteratively updating the model. This reveals the damage within the model and subsequently allows the residual properties of the damaged structure to be quantified. Within the scope of this work is the ability to resolve damage, that consists of either penny-shaped sub-surface flaws or tearing damage of box-section beams from surface experimental data. In case (b) an objective function is formulated in terms of a given structural response, or combination of responses that is optimised in order to return an optimal structure, rather than just a satisfactory structure. For the solution of these optimisation problems a novel software tool, based on the integration of genetic algorithms and a commercially available finite element (FE) package, has been developed. A particular advantage of the described method is its applicability to a wide range of engineering problems. The tool is described and its effectiveness demonstrated with reference to two inverse damage detection and quantification problems and one laminate design optimisation problem. The tool allows the full suite of functions within the FE software to be used to solve non-convex optimisation problems, formulated in terms of both discrete and continuous variables, without explicitly stating the form of the stiffness matrix. Furthermore, a priori knowledge about the problem may be readily incorporated in to the method

Boom for a load handling machine

A boom for a load handling machine, the boom has a mounting by which the boom is mounted on a body of the machine, and at least first and second telescoped sections. In use, the boom carries a load handling implement at or towards its outermost end. The first boom section is telescoped within the second section and is extendible and retractable relative to the second boom section by an actuator. At least the first boom section includes walls made at least predominantly of a composite material. A bearing member is located where adjacent walls meet to extend along a substantial length of the first boom section to provide bearing surfaces during sliding of the first boom section relative to the second boom section. Bearings also may be provided on the interior of the second boom section to further protect the first boom section

Boom for a load handling machine

A boom (12) for a load handling machine (10), the boom (12) has a mounting (20) by which the boom (12) is mounted on a body (11) of the machine (10), and first and second telescoped sections (24), the boom (12) carrying in use, at or towards its outermost end, a load handling implement (27), the second boom (24) section being telescoped within the first section and being extendible and retractable relative to the first boom sections (22) by actuating means, characterised in that at least one of the boom sections (22, 25) includes a plurality of walls (25a, 25b, 25c, 25d) each being a web made at least predominantly of a composite material, and where adjacent walls meet there being bearing members (30/35; 30a) which extend along a substantial length of the boom section (22, 25) to provide bearing surfaces (31) during sliding of the second boom section (25) relative to the first boom section (22)