No description available.

Product design decisions can result in unintended consequences that propagate across multiple life-phases such as manufacturing, use and disposal. If designers are to generate 'life-oriented' solutions, handling this phenomena is a necessity. Due to the sequence of life-phases, knowledge of such 'life-cycle consequences' (LCCs) is generated late, after decisions have been committed. Thus, designers have difficulties in foreseeing LCCs co-evolving with their solution. Further, a literature review established that, designers currently lack adequate support to foresee and explore LCCs during synthesis. To address this 'Design Synthesis for Multi-X (DsF∑X)' problem, this thesis proposes, implements and evaluates a computational 'Knowledge of life-cycle Consequences (KC)' approach. The establishment of a phenomena model disclosing how LCCs are generated from two different conditions has highlighted the necessity of concurrent 'artefact' and 'Iifephase system' synthesis. This provided a foundation of how to model and timely utilize LCC knowledge for revealing LCCs co-evolving with a solution description. This resulted in a framework for the 'KC' approach consisting of: the 'LGG knowledge modelling frame' which presents a formalism of 'what' elements to acquire and model for an application domain, together with how to structure the established relationships into 'LCC inference' and 'LCC action' knowledge; an 'artefact life modelling' frame which provides a formalism for describing 'artefact life' compositional models that support the inference of LCCs; and the 'operational frame' which discloses principles of how a LCC knowledge model can be utilized to amplify the human designer's capabilities. By identifying system requirements, an architecture and knowledge codification schemes, the framework was realized as a Knowledge Intensive GAD prototype, 'FORESEE', for the thermoplastic component domain. An evaluation of FORESEE established that the 'KC' approach integrates synthesis with foreseeing multiple LCCs. This is fundamentally different from first generating a candidate solution and afterwards analysing the solution for conflicts with artefact life issues. The 'KC' approach thus provides a step towards realizing pro-active DsF∑X support. However, further work is required to the framework and FORESEE to practically exploit its utilization.

No description available.

This thesis presents an approach to cutting dynamics during turning based upon the mechanism of deformation of work material around the tool nose known as "ploughing". Starting from the shearing process in the cutting zone and accounting for "ploughing", new mathematical models relating turning force components to cutting conditions, tool geometry and tool vibration are developed. These models are developed separately for steady state and for oscillatory turning with new and worn tools. Experimental results are used to determine mathematical functions expressing the parameters introduced by the steady state model in the case of a new tool. The form of these functions are of general validity though their coefficients are dependent on work and tool materials. Good agreement is achieved between experimental and predicted forces. The model is extended on one hand to include different work material by introducing a hardness factor. The model provides good predictions when predicted forces are compared to present and published experimental results. On the other hand, the extension of the ploughing model to taming with a worn edge showed the ability of the model in predicting machining forces during steady state turning with the worn flank of the tool. In the development of the dynamic models, the dynamic turning force equations define the cutting process as being a system for which vibration of the tool tip in the feed direction is the input and measured forces are the output The model takes into account the shear plane oscillation and the cutting configuration variation in response to tool motion. Theoretical expressions of the turning forces are obtained for new and worn cutting edges. The dynamic analysis revealed the interaction between the cutting mechanism and the machine tool structure. The effect of the machine tool and tool post is accounted for by using experimental data of the transfer function of the tool post system. Steady state coefficients are corrected to include the changes in the cutting configuration with tool vibration and are used in the dynamic model. A series of oscillatory cutting tests at various conditions and various tool flank wear levels are carried out and experimental results are compared with model—predicted forces. Good agreement between predictions and experiments were achieved over a wide range of cutting conditions. This research bridges the gap between the analysis of vibration and turning forces in turning. It offers an explicit expression of the dynamic turning force generated during machining and highlights the relationships between tool wear, tool vibration and turning force. Spectral analysis of tool acceleration and turning force components led to define an "Inertance Power Ratio" as a flank wear monitoring factor. A formulation of an on—line flank wear monitoring methodology is presented and shows how the results of the present model can be applied to practical in—process tool wear monitoring in turning operations.

A survey of the existing state-of-the-art of turbine blade manufacture highlights two operations that have not been automated namely that of loading of a turbine blade into an encapsulation die, and that of removing a machined blade from the encapsulation block. The automation of blade decapsulation has not been pursued. In order to develop a system to automate the loading of an encapsulation die a prototype mechanical handling robot has been designed together with a computer controlled encapsulation die. The robot has been designed as a mechanical handling robot of cylindrical geometry, suitable for use in a circular work cell. It is the prototype for a production model to be called `The Cybermate'. The prototype robot is mechanically complete but due to unforeseen circumstances the robot control system is not available (the development of the control system did not form a part of this project), hence it has not been possible to fully test and assess the robot mechanical design. Robot loading of the encapsulation die has thus been simulated. The research work with regard to the encapsulation die has focused on the development of computer controlled, hydraulically actuated, location pins. Such pins compensate for the inherent positional inaccuracy of the loading robot and reproduce the dexterity of the human operator. Each pin comprises a miniature hydraulic cylinder, controlled by a standard bidirectional flow control valve. The precision positional control is obtained through pulsing of the valves under software control, with positional feedback from an 8-bit transducer. A test-rig comprising one hydraulic location pin together with an opposing spring loaded pin has demonstrated that such a pin arrangement can be controlled with a repeatability of +/-.00045'. In addition this test-rig has demonstrated that such a pin arrangement can be used to gauge and compensate for the dimensional error of the component held between the pins, by offsetting the pin datum positions to allow for the component error. A gauging repeatability of +/- 0.00015' was demonstrated. This work has led to the design and manufacture of an encapsulation die comprising ten such pins and the associated computer software. All aspects of the control software except blade gauging and positional data storage have been demonstrated. Work is now required to achieve the accuracy of control demonstrated by the single pin test-rig, with each of the ten pins in the encapsulation die. This would allow trials of the complete loading cycle to take place.

Resin Transfer Moulding (RTM), at present, is a semi-automated, low volume production process for fibre reinforced plastics with much work being undertaken to achieve full automation and medium volume production. The efficient and consistent impregnation of thermosetting resin into a reinforcement pack are key requirements in the development of R TM. For mass production and automation accurate predictions of mould fill times are critical in order to plan production. At present, the fill times are predicted by assuming Darcy's law and using experimentally determined permeability value. Permeability measurements display a large amount of scatter which affects the accuracy of simulations of mould filling. Commercial fabrics such as 'Injectex' are now available which achieve high permeability to resin flow through a modified microstructural architecture of fibre tows. This thesis seeks to examine the relationship between microstructure and permeability in these fabrics in the context of possible decreases in mechanical properties which may result from non-uniform fibre distribution. An image analysis technique is used to characterise and quantify the regions of flow within the fabric architecture which are then correlated with a series of permeability measurements determined experimentally. This then leads onto a mathematical model for the prediction of the permeability of the fibre pack.

No description available.

No description available.

No description available.

Printed Circuit Board (PCB) manufacture involves an electrolytic copper deposition stage for consolidation of conductive circuit paths. Miniaturisation trends requiring increased circuit densities and high aspect ratio through-holes are restricted by the phenomenon of non-uniform copper electrodeposit thickness which can affect electrical impedance properties of the circuitry, cause electrical discontinuity between adjoining circuit layers and inhibit component-lead insertion. This thesis considers means of enhancing the electrodeposition process to alleviate the aforementioned problems. Following a comprehensive review of process technology, both a novel electrolyte agitation method utilising eductors and a Periodic Pulse Reverse (PPR) current technique were investigated experimentally within a pilot tank containing 350 litres of electrolyte. Eductor agitation was analysed/optimised using high-speed photography and a mass transport mapping technique. Data for agitation configurations were verified by statistical analysis of thickness distributions across high surface-area panels. PPR current was initially studied with a small-scale pulse unit and Assaf Cell throwing power test, followed by pilot tank trials using a full-size pulse rectifier in conjunction with eductor agitation and a proprietary electrolyte containing additives. Through-hole throwing power, deposit morphology and microstructure were investigated under various low-frequency pulse conditions and anodic-to-cathodic current density ratios. Eductor agitation and PPR current were compared against the more widely used air agitation and direct current techniques. The effects of air agitation on electrolyte conductivity and commercially produced PCBs were also considered. Optimum agitation conditions were achieved using eight eductors inclined at 37.5° from the horizontal and spaced equidistantly along longitudinal tank walls. Such conditions decreased the standard deviation of copper thickness measured on high surface area panels and lessened edge-effects. Consistent agitation levels up to ten times greater than static solution were recorded, providing enhanced deposition rates; by comparison, air agitation achieved levels of around seven times in uniform regions. Conductivity data showed good correlation with a theoretical approach; air agitation was found to reduce conductivity in proportion to the voidage fraction of gas bubbles and by 20-30% in electrolyte adjacent to air sparge pipes. PPR current provided superior deposits compared to direct current. Through-hole throwing power ratios between 1:1 and 1.3:1 (hole-thickness: surfacethickness) were recorded at mean cathodic current densities between 3.3-4 A/dm2 using pulse timings of 15,1,20,1,25,1 and 30,1 ms (cathodic: anodic) and current density ratios between 2.6:1 and 3:1 (peak-anodic: peak-cathodic); optimum conditions for boards produced in the pilot tank were provided by the 20,1 ms timing. The 25,1 ms timing exhibited high throwing power between 2.5-3.5 A/dm2 under Assaf evaluation but was unable to maintain a uniform thickness distribution in through-holes across a PCB surface. Deposit microstructure and microhardness recorded using PPR current varied according to pulse parameters. Controlling factors and their influence upon results were discussed. Parameters critical to optimisation of agitation and PPR current were attributed to electrochemical effects during deposition. The merits, limitations and potential application of these techniques were examined in relation to PCB manufacture and future priorities were considered.