Plain waterjet machining is an useful manufacturing technology, that is environmentally friendly and versatile. Despite the benefits, a limitation of the process is that there is not a well-established physical process model for plain waterjet machining. Current models are only valid for a narrow range of operating parameters and for specific materials. As a result the setup and optimisation of new plain waterjet applications is based on costly and time consuming experimental process optimisation. To address this need this thesis presents the development of a robust physical model for plain waterjet machining. To develop a consistent mathematical model, a study of the effect of the critical process parameters on machined surfaces was undertaken. This formed the basis for key relationships to be established at first for AI- 7475, which was then extended to a broad range of material including: Ti6AIV4, AI-6082, Inconel 718, stainless steel 304 and commercial copper. The model achieved a determination coefficient above 0.95 between the range of 0.05mm and 1.5 mm of depth. Finally the model was extended to allow the footprint left by the jet to be predicted, enabling the model to be applied to a broad range of applications such as: cutting, milling, peening, roughening surfaces and removing coatings; preliminary work on the area of prediction of average surface roughness was undertaken, providing a path for future research work in this subject.

In an effort to make the ECM process more appealing for industrial use, through the reduction of costs associated with this implementing this method, this work introduces a simulation based on the finite-element method that allows a time-dependent analysis of the machining process. Following on from the development of an initial two-dimensional simulation, a number of different industry specific applications are presented. These include the machining of non-flat workpieces, machining using A.C. supply, and a simulation of a non-equilibrium turbine blade set-up that uses a combined tool configuration. Towards the end of this work the industrial applicability of this simulation work is progressed further into three-dimensions. For each of these industry specific adaptations, sample results are presented. In addition to these adaptations, a section of this work discusses the development of a non-ideal, time-dependent simulation of ECM. Based on the findings of experimental work using a unique ultrasound system, this involves the introduction of a parameterised overpotential model. The increased accuracy gained from introduction of this model is then assessed through comparison with experimental data.

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Electrochemical machining has found numerous applications in recent years. The process offers significant economic advantages over conventional machining methods where complex shapes are required in high performance metals. However, a general lack of information on the design of a machining operation has resulted in an unacceptable amount of trial and error development work in many instances. This thesis is concerned with the selection of operating conditions and the design of tooling for electrochemical machining. An introduction to this aspect of the process is followed by a review of current literature on the subject. A model is adopted for the prediction of the one-dimensional equilibrium gap. The model utilises two parameters which require experimental determination. The model also predicts an upper bound to the electrolyte velocity in the electrode gap which corresponds to a limiting value of the tool feedrate. Various other apparent limitations on the metal removal rate are discussed. Preliminary experimental work was carried out to test the applicability of the theoretical model with particular reference to the pressure drop across the electrode gap. The results verify the model but the model parameters show dependence on the operating conditions of machining. The experimental work was extended, using a production electrochemical machine, to cover operating conditions used in practice. Sodium chloride and sodium nitrate solutions were the electrolytes in the machining tests. The anode workpieces were manufactured from mild steel and were initially plane and parallel to the cathode. The machining characteristics of the two electrolytes with mild steel are discussed. Anode profiles are presented at various operating conditions with the model parameters required to match the experimental test data. Phenomena other than the electrolyte conductivity appear to influence the anode profile in tests with sodium nitrate electrolyte. The theoretical model is not verified with respect to the upper bound to the electrolyte velocity. Tool feedrates and electrolyte flow velocities are used which exceed those predicted theoretically. The upper bound to the electrolyte velocity is the performance limit of the electrolyte pump. A separate investigation was required to determine the cause of machining failure. Miniature bead thermistors were inserted through the cathode into the electrode gap to measure the temperature of the electrolyte close to the cathode. Temperatures in this region are found to be greater than those measured at outlet. Machining failure is shown to be the result of boiling of the electrolyte around the gas bubbles evolved at the cathode. The conductivity of the electrolyte becomes less due to the formation of steam bubbles and the anode converges towards outlet so that sparking or arcing occurs across the gap. A correlation is introduced to allow prediction of this condition. The operating characteristics of electrochemical machining are discussed in relation to the correlation, and other limitations. An optimum outlet pressure exists which allows an increase in feedrate particularly at low machining voltages. A procedure for the selection of operating conditions is proposed.

Explosive impact welding is a process to produce bi-metallic plates and tubes. Whilst well established it has been essentially an empirical process. This thesis describes work carried out to numerically analyse the two plates welding process. Using finite element and finite difference engineering packages, most aspects of the explosive welding process are modelled. A notable advance is the inclusion of a 'Williamsburg' type equation of state for various mixtures of the low speed ANFO explosives used by most commercial explosive welding companies. The numerical simulations showed that the level of strain induced in the plates may be a factor in determining the bond strength. In most cases, the measured weld shear strength either remained relatively constant or increased slightly with the computationally predicted values of contact pressure, shear stress, plastic strain and impact angle. The shear stress in the flyer plates which welded was predicted to be of opposite sign to that in the base plate. The formation of interface waves and the phenomenon of jetting were computationally reproduced. The computational models were validated by explosive welding trials and by impact laboratory experiments using a pneumatic gun. A new semi-empirical theoretical analysis to predict the velocity and impact angle of the explosively driven flyer plate during its acceleration phase is developed and experimentally validated. This is an advancement on past theories which only considered a non accelerating flyer plate to impinge freely on the base plate. The equations were used to develop a code which includes the effect of explosive density, flyer plate thickness in the calculation of the flyer plate velocity during its acceleration phase. The results of the computer program were validated by experimental measurements. A method for calculating flyer plate velocity, based on the substitution of pressure equations into the 'Williamsburg' equation of state for reactive explosive and into the 'Muranghan' equation of state for the non-reactive explosive assuming non-ideal detonation behaviour is presented. The linear phase mixing rule is assumed for all thermodynamical properties. These equations provided a theoretical framework for the change of energy and pressure with respect to time in the reaction zone. The equilibrium and reactive adiabatic equations most commonly used are either empirical (e. g. JWL equation of state) or simplistic (e. g. polytropic EOS). In addition, they are usually inconsistent with the detonation EOS (e. g. they assume constant Gruneisen gamma or constant heat capacity), and are relatively inflexible. Early treatments used the polytropic equation for both unreacted explosive and detonation product gases, often with the same polytropic index. The analysis showed that the pressure predicted along the expansion adiabat by the 'Williamsburg' EoS based on an ideal calculation is too high, possibly by a considerable amount. Consideration of the length of the detonation/reaction zone (i. e. of order of 50mm) makes it necessary to take into account the variation of pressure along this zone

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