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Detailed analysis of aU the fretting fatigue test results available in the literature is carried out by employing refined asymptotic solutions. Several different criteria are used and it is shown that two give an improvement over stress-based criteria. These procedures provide a practical method for both designing against fretting fatigue failure and quantifying the nucleation time when fretting is unavoidable. The reduced stiffness method is developed together with the evolutionary algorithm which is the direct implementation of the Signorini and Coulomb friction contact inequalities. This method is capable of solving two dimensional frictional contact problems in significantly less time and is more accurately than a traditional FE approach. In addition, algorithms for determining shakedown limit of coupled contacts have also been developed. A problem of a plane receding contact was considered where a strip is pressed against an elastically similar half-plane by normal pressure extending along the strip surface but stopping short of the end. These phenomena are analysed, together with the behaviour of the system when the pressure is removed. Interfacial characteristics of a lap joint formed using friction grip bolts is also considered as these produce a receding contact. The joints consist of two elastically similar laps pressed in contact by a constant normal force and subject to oscillatory bulk load at the free end of the laps. Bulk load applied at the free ends causes a smooth change in the size of contact and the development of the slip zones. The trend of energy dissipation with the extent of contact and magnitude of remote tension, at various friction coefficients, has been found. Lastly, axisymmetric receding contact between a circular elastic disc pressed against a half-space has been studied. The disc is first subjected to normal pressure followed by torsion. Normal pressure alone causes a contact interface to separate, if the loaded area is sufficiently small. Torsion is subsequently appl ied which causes a change in the size of contact and has a significant effect on the direction of the resultant slip displacement and the stick/slip boundaries. I

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A combination of low density and good heat resistance is desirable for many applications. Porosity is used to develop low density, and high porosity materials are frequently associated with low thermal conductivity. Materials that display this property, coupled with heat resistance, may be useful for thermal applications. Porous materials can exhibit several different structural types. In this work the structures that can be formed from fire resistant materials to reduce the density are considered as three different types. The first structure is represented by a recently-developed composite material, which was created by TWI, Abington, Cambridge, and has been given the trade name Barrikade™. This material combines granules of an expandable natural mineral, vermiculite, with a sodium silicate binder, to produce an inexpensive material with high porosity and heat resistance. The structure of this material is that of a coarse agglomerate of particles, with much of the porosity being incorporated in the interparticle spaces. Possible applications are wide ranging, including the core material in domestic or marine fire doors, and as a low cost lagging material for industrial furnaces. A second structural type that is that of a fibre mat. An array of fibres, bonded at points or held together solely by friction and surface forces of the fibres, may include high levels of porosity in the spaces between fibres. Materials with this structure are made from melt spun mineral fibres, and exhibit a high degree of heat resistance. The example of these materials studied herein is Rockwool®, often used for building insulation purposes. The third structural type considered here is often used where low density is required; a foam. Foamed structures can have many attractive properties, but the fire resistance of the foams considered here, closed cell aluminium foams, has been frequently predicted to be favourable, without being demonstrated in controlled tests. Where the material properties are not already known, the microstructure, mechanical performance, fire and temperature resistance, creep behaviour and thermal conduction and expansion characteristics of the materials have been determined. The aim of the work is the assessment and ranking of the materials’ suitability for different applications, and determination of the critical aspects for the design of such systems.

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