No description available.

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No description available.

The compactional behaviour of a range of materials has been investigated by using an instrumented, 25.4 mm diameter punch and die set in conjunction with a Mayes Hydraulic Testing Machine. A CBM microcomputer with a multi-channel 3D-ADC was employed to monitor applied force of up to 45kN, the radially transmitted pressure to the die wall, die base reaction and punch displacement. Avicel and Sta-Rx compacts exhibited greater contact time, energy absorbtion and higher rate of radial pressure transmission to the die wall than was shown by Emdex, Emcompress and Paracetamol DC. It was deduced from the form of Heckel plots that time dependent bases Avicel and Sta-Rx underwent further densification when held under a constant stress. Densification of the mate~ials were usually greater if a slower speed of compression was used. Time dependent strain movements of the formed compacts held under a constant stress within the die have been investigated. The elastic and viscoelastic recoveries observed on load release have also been studied. The effects of various parameters on these movements and the feasibilty of using an elastic recovery index to predict the quality of a material are discussed. Avicel and Sta-Rx exhibited an extended plastic flow when held under a constant stress. Poorly compressible materials such as magnesium stearate and paracetamol exhibited the least strain movements and the greatest elastic expansion. It was found that the elastic recovery indices of the compressible materials were always lower than those of poorly compressible powders. Viscoelastic behaviour of the compacts after ejection has been studied following the changes in depth of penetration of an indenter over a long period into the surface of the compacts. Creep compliance curves obtained from the above two techniques have been compared. Both tests enable important viscoelastic parameters of the materials to be determined. Viscoelastic properties deduced from indentation tests were brought1y similar to those obtained by compression within the die. Throughout the work all data were recorded, processed and presented using a microcomputer and disk storage. Compressional criteria which are defined in the thesis have been found useful in evaluating some commercial granulates.

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This research has examined the two largest potential markets for melt extract stainless steel fibres, namely sprayed concrete and refractory concrete. An emphasis was placed on developing appropriate test methods that would produce experimental data of a practical and useful nature. A comparison was made at various stages between melt extract fibres and more conventional drawn wire fibres. The spraye~ concrete programme studied three fibre dispersion techniques on site and produced test panels between 50mm and 150mm thick from which beam and core specimens were cut. Information was obtained on fibre rebound and the effects of specimen age, fibre type and content on compressive, flexural and splitting strengths and toughness. Rebound of drawn wire fibres was found to be twice that of melt extract fibres on plywood panels and approaching two and a half times greater on rock. The addition of steel fibres produced increases in compressive and flexural strengths, typical values for a 7.5% dry mix content being 15% and 55% respectively. Two splitting tests on cores (Brazilian and point-load types) were investigated as possible methods of on site quality control and results indicated linear relationships between flexural and splitting strengths. The post-crack toughness was examined in terms of the area under the beam load/deflection curve and a computer programme was used to evaluate a variety of toughness indices. Deflection cut-off crieria based on the ultimate load co-ordinates or fixed values of deflection were found preferable to those calculated from the first crack deflection and the use of the elastic area under the fibrous beam's curve as the denominator of the index proved less reliable than using that of the unreinforced material. The inclusion of 7% by weight of melt fibres increased the toughness by over 30 times when using the 2.3mm fixed deflection criteria. [... continued].

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No description available.

No description available.

Traditional machinery for manufacturing processes are characterised by actuators powered and co-ordinated by mechanical linkages driven from a central drive. Increasingly, these linkages are replaced by independent electrical drives, each performs a different task and follows a different motion profile, co-ordinated by computers. A design methodology for the servo control of high speed multi-axis machinery is proposed, based on the concept of a highly adaptable generic machine model. In addition to the dynamics of the drives and the loads, the model includes the inherent interactions between the motion axes and thus provides a Multi-Input Multi-Output (MIMO) description. In general, inherent interactions such as structural couplings between groups of motion axes are undesirable and needed to be compensated. On the other hand, imposed interactions such as the synchronisation of different groups of axes are often required. It is recognised that a suitable MIMO controller can simultaneously achieve these objectives and reconciles their potential conflicts. Both analytical and numerical methods for the design of MIMO controllers are investigated. At present, it is not possible to implement high order MIMO controllers for practical reasons. Based on simulations of the generic machine model under full MIMO control, however, it is possible to determine a suitable topology for a blockwise decentralised control scheme. The Block Relative Gain array (BRG) is used to compare the relative strength of closed loop interactions between sub-systems. A number of approaches to the design of the smaller decentralised MIMO controllers for these sub-systems has been investigated. For the purpose of illustration, a benchmark problem based on a 3 axes test rig has been carried through the design cycle to demonstrate the working of the design methodology.