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Abstract: Advanced pore morphology (APM) structures are composite metal foams, which are assembled from a large number of small spherical elements with cellular structure, and are bonded into a composite with polymeric adhesive. The result of such composition is a wide spectrum of achievable mechanical behaviour in APM structures. To explore their full potential, efficient computational models are needed, which allow for simple parameter variation. Unfortunately, the current computer models do not allow for efficient simulations of porous composite structures with advanced pore morphology, as they employ complex discretisation approaches. A new approach to simulation is presented in this work, based on the discrete particle method (DPM), where every element of APM structure is discretised with a single node. This enables more efficient simulations of APM structures, while still allowing for simple variation of structural parameters. The DPM method was augmented with constitutive models of normal and tangential contact behaviour of APM elements and bonds between them, which were formulated based on an extensive experimental study of APM structure's geometry and mechanical behaviour. Consequently, the models enable simulations of large APM structure's behaviour by modelling the contact behaviour of individual elements. The implementation of new models was verified on a set of analytically solvable examples, and the accuracy of the models was validated with very good correspondence between computational and experimental results. Moreover, the models were validated on a wide set of examples, also taking into account the various strain rates and the absence of the bonds. The applicability of new models was demonstrated in a comprehensive parametrical study, where the influential structural parameters and properties were identified for low and high strain rate deformations. The study also demonstrated the possibility of customising the mechanical behaviour with property gradation, and with introduction of regular, as well as geometrically complex APM element assemblies. The possibility of coupled discrete particle method and finite element method simulations was also addressed. The newly developed models represent a breakthrough in the field of computational investigation of APM structures, and provide for simpler and more efficient investigations of APM structures in the future.
Keywords: Metal foams, advanced pore morphology, composite materials, mechanical properties, contact modelling, discrete particle methods, computer simulations
Published in DKUM: 11.03.2016; Views: 2635; Downloads: 245
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Abstract: The paper describes a general computational model for the simulation of contact fatigue-damage initiation in the contact area of meshing gears. The model considers the continuum mechanics approach, where the use of homogenous and elastic material is assumed. The stress field in the contact area and the relationship between the cyclic contact loading conditions and observed contact points on the tooth flank are simulated with moving Hertzian contact pressure in the framework of the finite element method analysis. An equivalentmodel of Hertzian contact between two cylinders is used for evaluating contact conditions at the major point of contact of meshing gears. For the purpose of fatigue-damage analysis, the model, which is used for prediction of the number of loading cycles required for initial fatigue damageto appear, is based on the Coffin-Manson relationship between deformations and loading cycles. On the basis of computational results, and with consideration of some particular geometrical and material parameters, theinitiation life of contacting spur gears in regard to contact fatigue damage can be estimated.
Keywords: machine elements, fracture mechanics, gears, contact fatigue, crack initiation, numerical modelling, teeth flanks
Published in DKUM: 30.05.2012; Views: 2833; Downloads: 93
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