R. English

Finite Element Analysis of a Total Knee Replacement by Using Gauss Point Contact Constraints

Finite element methods have been applied extensively and with much success in the analysis of orthopaedic hip and knee implants. Very recently a burgeoning interest has developed, in the finite element community, in how numerical models can be constructed for the solution of problems in contact mechanics. New developments in this area are of paramount importance in the design of implants for orthopaedic surgery. Modern techniques are described for finite element contact analysis and applied to two problems of stress analysis in a plastic tibial component. In the former, results are compared with a previous finite element analysis and with Hertzian solutions. In the latter, an estimate of the extent of convergence of the finite element solutions is provided.

Finite Element Study into the effect of footwear temperature on the Forces transmitted to the foot during quasi- static compression loading

The determination of plantar stresses using computational footwear models which include temperature effects are crucial to predict foam performance in service and to aid material development and product design. Finite Element Method (FEM) provides an efficient computational framework to investigate the foot-footwear interaction. The aim of this research is to use FEM to investigate the effect of varying footwear temperature on plantar stresses. The results obtained will provide data which can be used to help optimise shoe design in terms of minimising damaging stresses in the foot particularly for individuals with diabetes who are susceptible to lower extremity complications. The FE simulation results showed significant reductions in foot stresses with the modifications from FE model (1) without footwear to model (2) with midsole only and to model (3) with midsole and insole. In summary, insole and midsole layers made from various foam materials aim to reduce the Ground Reaction Forces (GRFs) and foot stresses considerably and temperature variation can affect their cushioning and consequently the shock attenuation properties. The loss of footwear cushioning effect can have important clinical implications for those individuals with a history of lower limb overuse injuries or diabetes.

Effects of Temperature on the Performance of Footwear Foams Subjected to Quasi-Static Compression Loading

Diabetic ulcers are the most common foot injuries leading to lower extremity amputation [1]. Early detection and appropriate treatment of these ulcers may prevent the majority of amputations [2]. One of the most important factors in causing such injuries is the friction of the foot on the ground which produces heat and induces a non-homogeneous elevation of temperature in the foot. This elevation varies according to the kind of quasi – static and dynamic movements and to the ability of the footwear materials to evacuate the heat.

Effective stress factors for reinforced butt-welded branch outlets subjected to internal pressure or external moment loads

This paper presents finite element data for 92 reinforced butt-welded branch outlet piping junctions designed according to the ASME B31.3 process piping code, for the purpose of investigating their effectiveness in the light of data for un-reinforced fabricated tee junctions. The data suggest that the reinforcement provided under the ASME B31.3 design is effective for the internal pressure load case and all external bending moment loads with the exception of branch out-of-plane bending for thin-walled assemblies.

An experimental procedure for measuring accelerations and strains from a tie down system of a heavy nuclear transport package during a rail journey

Abstract The transportation of nuclear waste and new nuclear fuel is an important aspect in sustaining the generation of electricity by nuclear power. The design of packages that satisfy regulatory requirements for normal operating and accident conditions is a complex engineering challenge. The ancillary equipment used to constrain the packages to their conveyance, a tie down system, is part of a multicomponent system used to transport packages. Traditionally, the individual components of the transport system have been designed in isolation. This approach does not account for the interaction between components of the system such as the conveyance, tie down system and package. The current design process for tie down systems is well established but, due to its heuristic development, suffers from uncertainties over which loading conditions should be applied. This paper presents a method for collecting measured acceleration and strain data that can be used to derive customised load cases for the design of tie down systems during rail transportation. The data was collected from a tie down system that restrained an empty TN81 package, weighing 99·7 tonnes during a routine rail journey from Barrow-in-Furness to Sellafield. Furthermore, the data can be used to validate modern computer models, allowing for the development of the previously described holistic approach to tie down system design. The results are unique because an ensemble of acceleration and strain time histories from a transport system laden with a nuclear package is unprecedented. A visual examination indicates that the loading a tie down system incurs during a rail journey consists of low magnitude accelerations. The measurement points also show that the general trend of acceleration levels is highest nearest the track and is attenuated by the package. The implications for the design of tie down systems are that two potential failure modes, fatigue and static strength, have been identified. The data provides scope for customising accurate static strength and fatigue calculations using modern computational techniques. This allows for the safety margins inherent in new designs to be determined and optimised design solutions made possible. INS makes no representations or warranties or any kind concerning this article, express or implied, statutory or otherwise, including without limitation, warranties of accuracy or the absence of errors.

Numerical Study of the Effect of Welding Parameters on the Strength of Spot-Welded Joints

Resistance spot welding (RSW) is widely employed in sheet metal fabrication, in particular in automotive bodies and structures. Manufacturers are increasingly demanding reduced design periods with improved safety requirements, which could potentially be achieved through computational simulations. This paper presents an integrated approach combining simulation of the welding process, materials characterisation and mechanical modelling to study the effect of welding parameters on the strength of spot-welded joints. The welding process was simulated and the dimensional attributes were used to build the mechanical models for strength analysis. The constitutive material properties of the base, nugget and the heat-affected-zone (HAZ) were determined by an inverse FE modelling approach using indentation test data. The predicted deformation of spot-welded joints of a typical automotive steel under tensile-shear load showed a good agreement with experimental results. The validated models were further used to predict effects of welding parameters on the strength and failure behaviour of weld joints. Potential uses of the approach in optimising welding parameters for strength were also discussed.

Effects of Temperature on the Performance of Footwear Foams: Review of Developments

The human foot is a multifunctional system that serves as the primary physical interaction between the body and the environment during gait. Footwear foam components maintain efficient foot function which is essential for daily living and provide cushioning by acting as a protective layer between the foot and the ground that attenuates the shock of impact. Footwear foam materials have high temperature dependency mechanical characteristics. The lower the temperature, the less elastic the material becomes. Consequently, it would seem reasonable to expect different mechanical and cushioning characteristics for the same shoe under different temperature conditions. Although the footwear foam materials great temperature sensitivity and the clinical implications of excessive temperature rise in the footwear during activities on lower extremity injuries and ultimate amputation are well recognized, but very few studies have demonstrated this dependency. This study reviews the developments made on the temperature effect on the performance of footwear foams and assesses its consequent clinical complications.

A Study into the Effects of Temperature on the Performance of Footwear Foams under Quasi-static Compression Loading and Their Hyperfoam Characterization

The human foot is a multifunctional system that serves as the primary physical interaction between the body and the environment during gait. Footwear foam components maintain efficient foot function which is essential for daily living and provide cushioning by acting as a protective layer between the foot and the ground that attenuates the shock of impact. Footwear foam materials have high temperature dependency mechanical characteristics. The lower the temperature, the less elastic the material becomes. Consequently, it would seem reasonable to expect different mechanical and cushioning characteristics for the same shoe under different temperature conditions. The insole and midsole are two of essential footwear components which play important roles in lowering foot stresses, and also in the correction of any biomechanical irregularities.

Effect of indenter shapes on inverse materials characterization based on the dual indenters method

Abstract The indentation method is a useful tool for studying the onset of plastic flow and work hardening in small volumes. Several approaches based on either single and dual indenters have been reported to characterise a wide range of materials. In this work, the single and dual indenters approaches, with different indenter types, have been comparatively studied using an inverse finite element modelling program developed based on the Kalman filter method. The effect of indenter shapes on the accuracy and uniqueness of the predicted results, as well as convergence time of the program are systematically analysed by automatically mapping the results with a wide range of initial values.