Over the last 20-30 years the subject of spin in tennis has become increasingly important. A great deal of work has been done to establish the effects which, increased levels of spin have, on shots. The most prominent effect of increased spin in a tennis shot is the resulting deviation in flight which allows players to, amongst other things, strike the ball harder with top-spin in the knowledge that it will still fall inside the court due to the extra aerodynamic downward force. With such significant advantages available racket manufacturers are naturally keen to maximise spin generation. That being said, very little research has been performed into the subject of spin generation in tennis and the affecting factors. This thesis details the development of a finite element model which is to be used to allow a greater understanding of spin generation and how varying properties such as string density (the number of strings in a string-bed), gauge and orientation affect its magnitude. The primary aim, or goal, of this research is to create an FE model which can be used to model oblique impacts and measure the resulting spin. Whilst considerable focus was placed on developing novel, modelling techniques to create the FE model, a great deal of emphasis was also placed on its validation. The validity of the model was examined under static loading conditions, such as that experienced during stringing. The dynamic performance was also validated using a combination of modal analysis and high speed video of dynamic impacts. Each of the validation methods provided assurance of the models performance, with all error margins less than 5%. The two areas of the FE model which required the most attention were the interaction properties (specifically coefficient of friction (COF)) and material properties. Previous studies have sought to obtain a single value for the COF of a tennis racket/ball system but this study examines how the COF varies as the strings interact first, with themselves and secondly with the ball. Each of the validation methods (dynamic and static) were deemed successful as they provided concise data which could be readily compared with the results produced by the FE model. Having validated the model s performance, with respect to predicting outbound spin, a number of oblique impact angles were modelled to allow a greater understanding of how the mechanisms of spin generation change with the inbound trajectory of the ball. This analysis showed that for the impact conditions studied the contact time of the impact was reduced from 6.2 milliseconds to 5.7 milliseconds when the angle was increased from 32 degrees to 40 degrees. Furthermore, a number of novel string-beds were modelled, with varying string orientations (between 30 degrees and 60 degrees relative to the rackets frame) and subjected to a similar analysis procedure, with their results providing the concluding section of the thesis.

As electromagnetic launcher (EML) is an apparatus that uses the electromagnetic (EMAG) force to propel an armature along a rail. An applied electric current, coupled with the resulting magnetic field, creates an EMAG force capable of accelerating an armature to velocities up to several thousand meters per second. The high sliding velocity, coupled with the electric current density, creates extreme thermal conditions at the interface between the rail and the armature that can cause melting at the interface. This project considers a lab-scale EML which is pre-loaded to establish the initial contact between arils and armature. This contact area influences the flow of the electric current and, therefore, it affects the thermal conditions significantly. This work presents a finite-element analysis (FEA) of the aforementioned physical phenomena of the lab-scale EML. This work is aimed at improving the understanding of the armature-to-rail performance and the useful life of an EML by developing a computer simulation which can be used as a design tool to acquire conditiodecoup for the best performance. A two-dimensional structural FEA is used to determine the structural deformation, the contact area, the contact pressure, the von Mises stress, and the material properties of the structural compliance. The vibration characteristics of the lab-scale EML armature are studied using Modal analysis. A three-dimensional electromagnetic FEA is performed to determine the EMAG force. Frictional and Joule heating are determined from a two-dimensional thermal FEA. The commercial finite-element package, ANSYS, is used in the simulation.

Finite element simulation of indentation is presented in this thesis. A rigid cylindrical indenter of flat end is used in all the cases, in which the simulation focuses on the effect of a hole on the indentation behavior of materials including elastic and elasto-plastic materials. In the simulation, the material is assumed to be a half-space. The relations between load and displacement are determined as a function of the hole size. Also indentation under cyclic loading is simulated for an elastic-perfect plastic half space. The influence of factors causing fatigue deformation like amplitude, median load and frequency is addressed. The propagation rate of plastic zone and Von Mises stress distribution at maximum and minimum loading are analyzed.

The detection of internal log defects has been shown to have a potential for increasing the lumber value. As an alternative to other available expensive log scanning devices, a method using radio frequency waves has been used to detect the knots. The main focus of the current research is to investigate the effectiveness of using radio frequency waves to detect the knots. Electrostatic finite element analysis is performed to predict the defects in logs. A script has been written using the commercial finite element ANSYS software to predict defects in log sections. The results are then compared with the experimental data measured on actual log sections. Analysis proved that it is possible to detect presence of knots in the log sections.

A blankholder is used to hold the edges of metal sheet while it is being formed by a matrix and a punch. An efficient way to design a stamping die is to integrate the blankholder plate into the die structure. This would eliminate the time and cost to manufacture blankholder plates. The integrated structure is called integrated blankholder. The main focus of this thesis is structural analysis and optimization of the integrated blankholder. The structural analysis of the integrated blankholder model (used for the production of doors of Volvo car model V70) is performed using Hypermesh and Abaqus. The FE-results were compared with the analytical calculations of the fatigue limit. To increase the stiffness and reduce the stress levels in the integrated blankholder, topology and shape optimization is performed with Optistruct. Thereafter, a CAD model is set up in Catia based on the results of optimization. Finally, structural analysis of this CAD model is performed and the results are compared with the original results. The results show reduction in stress levels by 70% and a more homogeneous stress distribution is obtained. The mass of the die is increased by 17 % and in overall, a stiffer die is obtained. Based on the simulations and results, discussion and conclusions are formulated.

Recent efforts in engineering education research have set in motion reform advocating more active learning in the classroom. Active learning centers on the student and consists of pedagogical approaches to address the broad spectrum of educational backgrounds and demographics. In order to further the research focused on active learning products, appropriate and innovative assessment methods must be developed. For this thesis, innovative active learning modules are the focus of the analysis. In total, 12 Finite Element tutorials are designed and assessed using both statistical analysis and confidence interval correlations. Fundamental and informative assessment strategies have been developed to iteratively improve active learning approaches. Results of this process show that the finite element tutorials lead to enhanced student learning that can span across student demographics. Certain cases do exist where unique learning styles or personality types respond more positively to this pedagogical technique than others. Global outcomes are presented to assess these tutorials cumulatively, as active learning products. Finally, the assessment methodology is redesigned into a useful toolkit for educators to follow in furthering efforts of integrating active learning into any engineering classroom. / text

In predicting the likely behaviour of precast prestressed concrete flooring systems in fire using advanced finite element methods, an improved numerical model using the non-linear finite element program SAFIR has been developed in order to investigate the effects and the interaction of the surrounding structures and has been used extensively throughout this thesis. Note that fire induced spalling is not included in the analysis. In the numerical investigation of the new model, the reinforced concrete topping is modelled as part of the beam elements in order to predict the behaviour of single hollowcore concrete slabs, with various support conditions, under a Standard ISO fire. It is shown that the current approach using tendons that are anchored into the supporting beams leads to a major problem for precast prestressed flooring systems. In order to resolve this problem, a multi-spring connection model has been developed to include the old and new connection systems corresponding to the New Zealand Concrete Standard NZS 3101. The connection model with hollowcore slabs is validated against a published fire test. The investigation on restrained hollowcore floors is performed with various parameters and boundary support conditions. Numerical studies on various boundary support conditions show that the behaviour of hollowcore floors in fire is very sensitive to the existence of side beams. Further investigations on the effects of fire emergency beams, which reduce the transverse curvature of floors to improve fire resistance, are made on 4x1 multi-bay hollowcore floors with different arrangements of theses beams. The numerical studies show that fire emergency beams significantly increase the fire resistance. Code based equations which can calculate the shear resistance and splitting resistance are then introduced. The Eurocode equation can be modified with high temperature material properties to estimate the shear capacity of a hollowcore slab. The modified Eurocode equation which is fit to fire situations validated against the published literature with respect to shear tests in fire. The structural behaviour of single tee slabs having different axial restraint stiffness as well as the variation of axial thrust in fire is then studied. SAFIR analyses of single tee slabs show that fire performance can increase when a web support type is used that has high axial restraint stiffness. A series of test results on prestressed flat slabs conducted in United States are used to validate a simply supported numerical model. The application of multi-spring connection elements is also investigated in order to examine the feasibility of continuity.

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