Numerical solutions for solid mechanics problems with a rapid variation of quantities in a small domain may result in impractical estimates.The presence of a cavity in an elastic domain, as a classic example, enforces more complexity on a large model due to its stress concentration impact.Boundary element method (BEM) as a numerical method applicable to this type of problem, also involves singular kernels.Due to the implementation complexity of augmented integration schemes, there is still a tendency to use ordinary integration techniques.Besides, enforcing boundary conditions might also be challenging in BEM.In this study, near-corner stress values are explored to evaluate the impact of straightforward integration schemes and discontinuous boundary enforcement treatments.Provided results demonstrate that for coordinates near corners in this specific problem, using non-conforming elements and shape functions with displacement vectors might reduce the error values to fewer than 1%.Further, despite the results for nodes away from corners, unique traction can compromise accuracy for near-corner coordinates in exchange for its simple implementation.

The paper focuses on deriving a local variant of the method of fundamental solutions (MFS) for the case of Stokes flow.Compared to the global and local basis variants, the local with global basis one leads to a sparse characteristic matrix as in fully localized variants but with a narrower system of equations and thus makes the solution of especially large-scale problems more efficient.It is also essential to keep the condition number of the characteristic matrix within reasonable bounds and remove the solution dependency on fictitious sources.A combination of MFS and finite collocation approach was used for the localization with a globally defined Stokeslet fundamental solution.The results of the particular local variant were compared on several examples, and the dependence of the solution on the density of the point network and the dimensions of the stencil used were also tested in the paper.

This paper presents a treatment of the topology optimization problem for two-dimensional fields governed by Laplace's equation. The study considers various boundary conditions, including Dirichlet, Neumann, Robin, and nonlinear radiation boundary conditions. Additionally, the topological derivative for a general objective functional comprising solely of boundary quantities is derived, with a special focus on the case of a radiation boundary condition in a black body. The accuracy of the derived adjoint problem and topological derivative is validated through several boundary element method calculations.

Welcome to the WIT Press eLibrary - the home of the Transactions of the Wessex Institute collection, providing on-line access to papers presented at the Institute's prestigious international conferences and from its State-of-the-Art in Science & Engineering publications.

Welcome to the WIT Press eLibrary - the home of the Transactions of the Wessex Institute collection, providing on-line access to papers presented at the Institute's prestigious international conferences and from its State-of-the-Art in Science & Engineering publications.

Electrical conduction by the motion of ions in the solid state was considered to be impossible for a long time.When Michael Faraday discovered that solid lead(II) fluoride conducts electricity when heated, it was an anomaly and the conduction mechanism remained ununderstood for long.Nowadays, several ions of small size and low charge, such as H + , Li + and F -, are known to be highly mobile in solid compounds provided the crystal structure contains pathways that make possible easy ionic motion.We have prepared new compounds, PbSnF4 and BaSnF4 and other phases in the PbF2-SnF2 system that increase the conduction efficiency by up to three orders of magnitude relative to the corresponding MF2.Solid state fluoride ion batteries (FIBs) promise high specific energy and thermal stability.High potential solid state rechargeable fluoride ion batteries are being designed and BaSnF4 has been used as one of the ingredients to form an interlayer solid electrolyte with high conductance.In the current work, we have analyzed the role of divalent tin in these structures, in terms of crystal structure and of local bonding to fluorine, in an effort to understand how it can result in such a high enhancement of the conductivity.Diffraction methods were used to investigate the crystal structures and 119 Sn Mössbauer spectroscopy for studying the mode of Sn-F bonding and the electron configuration of tin.

Tooth root bending fatigue is the most dangerous failure mode in gears. Indeed, it starts from the nucleation of a crack within the tooth root fillet region and the subsequent propagation up to the complete breakage of the tooth. To investigate this phenomenon, Single Tooth Bending Fatigue (STBF) tests are largely diffused. In these tests, an alternating bending stress at the tooth root is induced by the application of a pulsing force to the gear flank. In addition, this loading condition can be modelled through Finite Elements (FE) to study the stress state in the affected area. However, the application of strength criteria such as von Mises' can provide the equivalent stresses when the applied force reaches its maximum value but does not provide any insight in terms of fatigue behaviour. Nevertheless, the crack propagation can be investigated by analysing the results of FE analyses (which model the entire load cycle) through fatigue criteria based, for instance, on the critical plane concept. Previous studies conducted by the authors have shown that the different fatigue criteria (to study the tooth bending failure) lead to very different results. Therefore, the objective of the present paper is to compare the results of analyses carried out with different fatigue criteria based on critical plane, i.e. Findley, Matake, McDiarmid, Papadopoulos, and Susmel, with experimental outcomes, i.e. STBF tests on an aeronautical gears, to determine the most appropriate fatigue criterion to characterize the fatigue behaviour of these mechanical components. Results reveal that all fatigue criteria lead to consistent results when the target is to identify the most critical point. However, the Findley and Papadopulus criteria are found to be the most accurate for what concerns the evaluation of the damage. Among the others, Susmel turns out to be the most conservative criterion while the Findley criterion is the only one capable of identifying with good accuracy the direction of crack propagation.

One of the main engineering objectives nowadays is to develop and design a sustainable practice whilst operating a technology that can yield value added products and be environmentally friendly in the same time. No better example can be provided of ongoing research of such technologies other than waste to fuel and energy solutions. Such technologies can recycle solid waste whilst maintaining a sustainable practice and operation. A prime example of such is the technique of pyrolysis, where waste is deteriorated in inert environments and products of such process are used in the place of petroleum fossil-based ones. One of the products of pyrolysis namely when using a polyolefin polymer is chemical waxes that were proven recently as a valuable product on the market. These waxes have a potential of having fuel range hydrocarbons and their market is of growing capacity as of late. In this work, the pyrolysis of polyethylene (PE) sourced as a virgin extrusion grade and used a translucent pellets, was used to produce waxes in the pyrolysis operation of fixed bed batch type. The pyrolysis reaction temperature took place between 500 and 800C and waxes were collected and characterised for their fuel potential amongst their physical and rheological properties. The elemental carbon in the wax ranged between 81.04% to 87.67% showing high potential of carbon based material similar to the one of the original high density polyethylene (HDPE) feedstock material. Furthermore, the dynamic viscosity (at 40C) ranged between 31 and 171 Centipoise. It is worth noting the that the fuel range of the wax was of high range of some 70% diesel fuel for material collected at 500C which is attributed to the slow pyrolysis regime and the branched nature of the feedstock. This points towards utilising this product as a potential fuel source in addition to further upgrading instead of classical refinery ones.

In accordance with the European politics of reducing the amount of plastics and polymers sited in landfills, the inclusion of compounds such as roof wastes as recycled and reusable materials to replace variable amounts of aggregates is interesting in the production of new construction materials due to their physical and chemical behaviour.Mortars made with Portland cement, sand, water and grinded roof wastes from the automobile industry that replace in different amounts part or all of the aggregates are examined in this study.To try to avoid the mechanical resistance limitation due to the use of roof wastes, the chemical properties of the binders have been modified with non-ionic surfactants that changed the effect on the hydration of the clinker.This variation produces an important change in the mechanical resistance to achieve recycled structural materials with a low density compared to conventional light mortars.In addition, these additives improve other properties including workability, compaction of the matrix, prevent the disintegration of the particles and help to improve the mechanical properties, ductility, thermal resistance and durability against fire to reinforce the materials.These ecomortars have a lower thermal conductivity as more quantity of roof wastes are incorporated, which greatly favours the thermal insulation of the final envelope, as well as a good behaviour against temperature, measured in terms of thermogravimetry and non-combustibility test.With these results, we can consider the use of roof wastes as a sustainable alternative to the materials currently used and then with them we can be able to contribute to a more ecological business model in the building sector.

From the standpoint of detectability of small maritime objects by a ship's radar system, the radar cross section (RCS) of a maritime object is a key parameter that determines the detectability of an object. When a vessel navigates in narrow channels and in areas with high sea traffic density, the ability to detect small maritime targets such as buoys and inflatable rubber boats is crucial for maritime safety. However, it is difficult to measure the radar cross section of such maritime objects in environments such as laboratory or in a field test not only due to object size, but also due to the fact that these objects are partially submerged into seawater. In such situations, the most effective approach is to apply numerical methods for electromagnetic scattering from inhomogeneous objects in order to predict the RCS of a maritime object. Though approaches to RCS prediction are diverse, one of the most sophisticated, namely, the hybrid numerical method based on combination of boundary and finite elements is applied in this work. This hybrid numerical method first computes near electromagnetic field on the surface of the scatterer, followed by a particular technique developed by the authors to compute the radar cross section of small maritime targets from these near field values. The accuracy of the approach is discussed and some illustrative computational examples of RCS calculations are given.