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No description available.

Both dip and pulsed modes of metal transfer were investigated to establish which method produced the better bead geometry and penetration on 2024 and 2014 aluminium alloys using 2319 filler wire. The MIG electrode configuration used was electrode positive, which provides cathodic cleaning for aluminium alloys. Some initial work was also carried out using 6013 with 2319 as the consumable. A second part of the project involved the investigation of different combinations of shielding gas, and during both this and the previous task it was necessary to adjust the welding parameters to achieve acceptable welds. Initially, visual inspection and measurement of bead geometry were used for analysing the welds, but macrographs/micrographs, radiographs, hardness profiles and tensile tests were carried out to look more closely at the welds, once acceptable bead geometry and penetration was obtained. The microstructure was investigated to ascertain the extent of any porosity and chemical changes that might affect the mechanical performance of the joint by depletion of alloying elements in the HAZ. Pulse mode metal transfer improved the weld properties in comparison with the use of dip mode and was therefore used for all the work following the first section. During the work relating to shielding gas composition it was found that a 30% helium balance argon shielding gas produced the best results. It was observed during the speed trials that porosity increased with speeds in the region of 1000mm/min and also below 650mm/min. Pulse frequency and pulse time seemed to affect the arc performance and also influenced the levels of porosity. The need to thoroughly clean the joint area was also seen to be paramount in reducing porosity to a minimum. Hardness profiles indicated a dip in hardness just inside the HZ adjacent to the fusion line, with all tensile specimens failing at this point when the beads were left on. The tensile results carried out on 1.6mm 2024 at Cranfield using 30% helium in the shielding gas produced UTS strengths equivalent to 85% compared to parent metal strength, while those performed by Shorts produced UTS results up to 89%. This indicates an increase in strength over previous published results of 100%. Ibbotson cites two sets of TIG welds having UTS values of 191 and 194 MPa equivalent to 42% compared to parent metal strength while the welds produced at Cranfield using 30% helium in the shielding gas were 402 l\/IPa, equivalent to 86%. The tensile results for the 2mm 2014 aluminium alloy were even better, producing UTS results equivalent to 94% compared to the parent metal. With the 2014 alloys Ibbotson cites two sets of welds in both TIG and MIG and here UTS results were 221 and 243 MPa, equivalent to 55% compared to parent metal i ABSTRACT MIG Welding Aluminium alloys strength, while similar welds produced at Cranfield were 395MPa equivalent to 94%. The fractographs for this showed the start of a shear fracture indicating that the strength was nearing that of the parent material. Against these results even the thick section ]2.7mm 7150 welds having a UTS of 347MPa equivalent to 58% compared to parent metal strength look quite promising. The time trials relating to the natural age hardening process on 2024 welds confirmed that they achieve their maximum strength after 30 days, increasing by some 15% from half an hour after welding to 30 days. The use of thick section materials in the form of 12mm 2024 and 12.7mm 7150 became a requirement during the latter stages of the project with the investigation into the use of a number of commercially available filler wires dominating the research. Post weld heat treatment was seen to improve the strength of the welded joints when employing several different filler wires, but when incorporating a dual post weld heat treatment with 7150 using 1.6 5180 filler wire a marked improvement was observed. Arc monitoring techniques were used in the form of Arcwatch to log the arc voltage and welding current values, and a number of statistical evaluations were conducted during the project using the Arcwatch data. Geometrical data relating to weld bead dimensions was collected at numerous stages throughout the research and employed to build a joint prediction statistical model. This provides the end user with a means of process parameter selection and a visualisation of the influence of parameter variation on weld bead geometry. It has clearly been demonstrated that it is possible to produce viable welds using the MIG welding process with electrode positive, with comparatively low heat inputs when using a number of different high strength aluminium alloys and different composition filler W1I`CS. This piece of research has involved the welding of high strength aluminium alloys that have, in the past been classified as difficult to weld and with the 7xxx series, regarded unweldable. The results illustrate a major advancement in the welding of high. strength aluminium alloys, represent a considerable improvement in the strengths obtained in weldments using these alloys and has encouraged the U aerospace industry to pursue further research in this field.

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No description available.

The injection moulding process is a major fabricating technique used in both the plastics and rubber industries. The quality of the coloured polyolefin products produced by the injection moulding technique depend, at least in part, on the mixing process associated with the plasticating screw. The aim of the research programme reported in this thesis was therefore to investigate two main areas: (1) the effect of moulding conditions on the mixture quality of injection moulded articles; and (2) the suitability of the computerised image analysis technique for characterising pigmented mixtures.

The research relates to the modelling and control of multi-stage production - inventory systems in high volume low-mix manufacturing industry. Examples of such class include typically the automotive and white goods industries. The research has included the investigation of available mathematical control techniques in the "optimal" control of manufacturing systems, a study of their applicability and the practical implications of their use in a manufacturing environment. Earlier work in the field of multivariable control theory has shown the potential of application in industrial management. In this thesis, previous work is extended whereby explicit consideration is given to some practical constraints existing in a typical manufacturing environment. It is considered that the research carried out has contributed to the development of multivariable control theory as applied to practical control problems with constraints. This has been achieved by the use of structured canonical forms and the exploitation of their particular ordered properties, resulting in the development of practical control models. The automotive industry has been used as a practical case study and modelled as a linear discrete-time control problem. The models have been developed in close liaison with a car manufacturing company in the U.K., and have been shown to produce practical control policies in the areas of both capacity requirements planning and inter-stage float levels. Particular attention is given to existing practical constraints of such systems. The approach is extended to deal effectively with a more general multi-product environment. It is noted that multi-product environment is of a more complex nature than single product since it involves the consideration of competition for the limited resources that have to be shared out "sub-optimally", in addition to providing smooth control of the responses. The development and application of multivariable control theory as described in this thesis is shown to provide an effective methodology for the solution of dynamic production control problems of multi-stage production-inventory systems in both single and multi-product environments.

This thesis is concerned with the engineering design requirement and the process by which it is elicited, evolved and recorded. The purpose of the research reported in the work is to achieve a more complete understanding of the engineering design requirement, and to apply that understanding to the better support of designers during the design requirement capture phases of the design process. Two perspectives dominate the approach to the research. The first concerns the relation between the design process and human cognition. The research subject is seen as being fundamentally a product of the human mind and that such things as knowledge, language and meaning – the things commonly associated with cognition – are crucial to its proper understanding. The second perspective is informed by the view that the development of the design requirement can be seen as a knowledge-intensive process of communication. Thus, understanding communication between humans and some aspects of communication failure can assist in understanding and remedying failure in design requirement capture.

This research work investigates the information requirements of the engineering designer during the early phases of the design process. In particular, it focuses on the use of standard components, and the information requirements associated with them. The research presents a system for the representation of information, both formal catalogue data, and also what the author has termed "Informal Information". Also presented is a system for the representation of catalogue information that will allow for standard component catalogue interfacing.

Nos últimos anos, os processos de manufatura têm sido desenvolvidos assumindo-se uma faixa mais ampla de aplicações e capacidades. Devido a isto, a seleção destes processos está se tornando uma tarefa mais complexa. Ela inclui a análise de aspectos monetários e tecnológicos. Atualmente, a maioria das indústrias de manufatura tem que decidir sobre os investimentos na produção dentro de uma vasta gama de possibilidades. Portanto, uma metodologia inovadora é necessária para suprir os elementos necessários para o processo de decisão aplicado a investimentos nos sistemas de manufatura. Este trabalho propõe uma nova metodologia que estabelece passos com o objetivo de se obter as informações essenciais para a comparação entre sistemas de manufatura. Esta metodologia considera aspectos ao longo do tempo de uma forma integrada. O método proposto é aplicado a um estudo de caso onde o processo de retificação é comparado à uma operação de torneamento na produção de eixos de transmissão para a indústria automotiva. A aplicação do método ilustra o poder de sua aplicação no ambiente industrial. / The manufacturing processes have been developed in the last years assuming a wider range of applications and capabilities. Due to that, the selection of theses processes is usually getting a more complex task. It includes the analysis of technological and monetary aspects. Nowadays, most of manufacturing industries have to decide the investments in manufacturing within a wide range of possibilities. Therefore an innovative methodology is required to provide the necessary elements for a decision process applied to investments in manufacturing systems. This work proposes a new methodology that provides steps in order to obtain the main information for the comparison between manufacturing systems. It considers technological and financial aspects along the time in an integrated way. The proposed method is applied to a case study where the grinding process is compared to a turning operation in the production of transmission shafts for automotive industry. The application of the method illustrates the power of its application in industrial environments.