The major part of this work is concerned with the development of the apparatus and the techniques involved in the measurements of the load-deflection characteristics of a pneumatic tyre and its associated changes in the pressure and volume of the air contained in it. A satisfactory results were obtained from this arrangement. From the measurements of the changes in volume and pressure of the air in the tyre, relationship was derived whereby the volume of the tyre at a particular inflation pressure was determined. The volume obtained by this method agree favourably with the value obtained by the conventional method of filling the tyre with water, and also it has the advantage over the conventional method due to its ease of operation. The most important aspect of this work is to determine qualitatively the amount of work required to deform the tyre structure. This is determined from the relationship that the work done on the structure is the difference between the total work done and the work done on air. An isothermal process was assumed. It was found that the work done on the structure accounts for only 10-20% of the total external work done on the tyre and is independent of the inflation pressure. A simplified quantitative treatment of the result based on the Gent and Thomas theory of air spring was developed and it agrees satisfactorily with the experimental results.

Part 1: Synergic control in MIG welding. Synergic controls (i.e. real time control methods) for both steady DC open arc and short circuiting arc operations have been developed in this study. These have been based on the generalised quadratic and linear ‘power-current' and linear ‘voltage-current’ equations which adequately describe the MIG welding operation. The controls are low coat electronic units which are added to a ‘transistor’ controlled power source. The units based on the ‘power-current’ concept can operate with the power source set in the constant current, constant voltage or any intermediate mode of output characteristics, and regulate only the steady DC open arc operation. The unit based on the ‘voltage-current’ concept operates with the power source set in nominally constant voltage mode, and regulates both steady DC open arc and short circuiting arc operations. These controls adjust the current, voltage or power automatically according to any operator-selected wire feed speed whether maintained constant at any level, varied gradually or modulated with any waveform to achieve ‘thermal pulsing’. In addition, two approaches have been used to adapt the synergic control units to a lower cost, thyristor controlled power source which is more widely used in industry. In one approach, the generalised control equation used previously for the transistor controlled power source has been extended to take account of the output characteristics of the thyristor controlled power source. As an alternative, the control units themselves have been modified to allow for the different power source characteristics. The control systems have been successfully demonstrated for producing sound welds in a wide range of welding applications, for both mechanised and manual welding techniques. Part II: Penetration control in TIG welding A 'backface' penetration control system developed at Liverpool University, based on a ‘video camera' instead of a ‘photodiode' as a sensor, has been evaluated at The Welding Institute. Essentially, the system controls the size of the weld pool, instead of an average level of radiation, by regulating pulse current period, by means of a fibre optics image guide/video camera/microcomputer based controller. The system has been found to be capable of controlling the weld bead penetration uniformly in stainless steel plates and joints, for constant as well as variable material thicknesses. However, the system cannot be used with high frequency (HF) arc discharge, as required for automatic arc initiation, because the software and electronic components are corrupted. A hard-wired control unit has therefore been developed at The Welding Institute to replace foe microcomputer based controller. This unit can be operated reliably with automatic HF arc initiation. Furthermore, it has been shown to control weld bead penetration in stainless steel plates and joints, for constant at well as variable material thicknesses.

An apparatus was designed and constructed to allow a molten polymer extrudate under tension - or draw-down - to pass through a volume of liquid metal alloy in order that the extrudate would rapidly reach the temperature of the metal and be fully quenched on leaving the medium. The temperature of the medium could be controlled to an accuracy of +/- 0.5°C and the molten extrudates could be subjected to a wide range of draw-downs whilst maintaining a continuous production of extrudate. High density polyethylene (HOPE) extrudates were prepared from three dies - circular, strip and flat-film - at a range of liquid metal alloy temperatures (111 - 123°C) and over a wide range of draw-downs. The effect of processing on the HOPE extrudates was analysed by tensile testing, cyclic strain recovery, shrinkage testing, density measurements and annealing in air and liquid metal at 117°C. It was found that the level of draw-down and the temperature of the quenching medium had a profound effect upon the resultant properties of the extrudate. Extrudates prepared using a low level of orientation and low bath temperature are similar to those quenched in air, i.e. having a pronounced yield point, whereas those prepared using a high level of orientation and a high bath temperature exhibited properties similar to those of amorphous samples, i.e. high modulus and low extension at break. However, if the extrudate remains in the bath longer than is necessary to quench it, this effect is reversed. A possible mechanism was proposed to explain the relationship between the values of the processing parameters used, the morphology of the resultant HDPE extrudates and their properties.

The service performance of anodised aluminium in architecture is dependent upon the control of the anodising, colouring and sealing processes. The quality of the anodic oxide film is determined by assessment tests. The use of a nitric acid ‘predip’ on soft films was shown to dissolve a soft outerlayer. A new admittance test was devised in which the ‘drift’, Y, was measured using 33%, nitric acid. This test threw light on the sealing quality of films exposed to the environment and those sealed in nickel salt solutions. Well-sealed, hard films gave a Y value of 0.1 to 0.2. A sealing mechanism for nickel acetate solutions is proposed in which ageing of a Ni-A1 complex is thought to play a significant role. The admittance-abrasion (Y-?) profile was used to supplement other test data. An accelated sulphur dioxide test was investigated, the optimum conditions for which were 40°C for 6 hours. The presence of a sealing bloom was determined by a simple go/no go three paper abrasion test. The assumption is made that Yt (25°C ) = a + bt and linear regression has been used to find b. It has been found that for batches having a range of thicknesses but a common sealing time, the linear relation is a reasonable assumption when the gradient is < +10. The admittance values of electrocoloured tin black film s have been found to be anomalous. The gradients are negative due to the presence of tin in the pores. Linear regression has been used to obtain an average value of b over the whole thickness range, which gives information as to the degree of sealing. Colouring and soaking in sulphuric acid at elevated temperatures (before sealing) reduces the abrasion resistance. The abrasive wheel test was also used to show the depth of tin within the pores. The use of the addition agent ‘Tribrite’ in tin colouring solutions suppresses the outward, whiskery growth of tin in the pores.

Various factors and filler characteristics which influence the ability of added polymer particles prepared as latices by emulsion polymerisation to reinforce the mechanical properties of films derived from rubber latices, particularly post-vulcanised natural rubber latex, have been investigated. The emphasis has been upon the enhancement of tear strength and puncture strength.

A detailed study of the effect of added ingredients upon processing behaviour of NR latex with reference to dipping has been conducted in an endeavour to further understanding of the fundamental science underlying latex dipping processes.

The study is concerned with the interaction between p-tertiary butyl phenol-formaldehyde condensates and isoprene rubber under conditions resembling those used in industrial vulcanization processes, and involves investigations of reaction rates, mechanisms of reactions and structures produced. The work is an extension of an earlier study (A. Fitch, Thesis for Ph.D. (C.N.A.A.), 1978). 'Model' phenol-formaldehyde condensates (2-methylol 4- tert.butyl 6-methyl phenol and the ether derived from it by thermal condensation) are shown to interact with isoprene rubber (cis-l,4-polyisoprene) to form adducts containing chroman structures. The ether reacts somewhat more quickly and more efficiently than the methylol compound. 'Lewis acid' catalysts will greatly accelerate the reaction, but cause concurrent structural isomerization of the isoprene rubber, to an extent depending on the nature of the catalyst. In separate experiments involving only rubber and catalyst, it is found that, of the three catalysts examined, tin(II) chloride dihydrate causes extensive isomerization, tin(II) chloride (anhydrous) causes little isomerization and zinc(II) chloride (anhydrous) causes negligible isomerization, under the appropriate reaction conditions. The structural changes are evaluated, and involve cis-trans interconversions double-bond shifts, cyclization and crosslinking. Using zinc(II) chloride as catalyst, a study is made of the effectiveness of five different polyfunctional phenol- formaldehyde condensates as vulcanizing agents for isoprene rubber. The condensates consist of 2,6-dimethylol 4-tert. butyl phenol and four of its derivatives containing different molar proportions of methylol, dibenzyl ether and diaryl methane groups. One of the derivatives is a commercially-available vulcanizing agent. Measurements of rubber-combined phenolic material and of crosslink concentrations are made at different times of reaction, and results show that the condensates containing high proportions of dibenzyl ether links are the most efficient vulcanizing agents. Efficiency may be further improved by the addition of a formaldehyde donor to suppress side-reactions. The results indicate that, in all cases, combination with the rubber occurs through chroman linkages and the crosslinks contain at least two phenolic nuclei joined by dimethylene ether or methylene links.

The effect of changing processing conditions on the mechanical properties of LDPE, LLDPE and blends of LDPE and LLDPE blown films was studied. The results were analysed by relating the change in mechanical properties with the change in the residual strain of manufactured film. The residual strain was measured by using a shrinkage method.

All weld metal test pieces were produced from two commercial and six experimental 7016 type electrodes, each having different contents of manganese and nickel. These were tested in three point bending over a range of depressed temperatures in a cryostatic cell of the author’s devising. Notched samples were used to obtain values for the cleavage fracture strength. This was calculated by reference to slip line field theory from the fracture load at the test temperature where fracture was first coincident with general yielding. The commercial electrodes were first tested in the as welded condition and all eight electrodes were then tested after a heat treatment designed to give a microstructure similar to that found in re-heated weld metal. Notched and pre-cracked samples were then tested in the heat treated condition to determine KI values. Fracture surfaces were examined by scanning electron microscope and grain size measurements made by optical microscopy. Lower shelf impact energy measurements were also made. The results show that both manganese and nickel individually increased the cleavage fracture strength. In combination the best cleavage properties were given by alloying contents of 1.0% manganese and 1.5% nickel increasing alloying beyond this level had a detrimental effect. The mechanism for this was a combination of grain size effects, changes in the slip characteristics of the material, the size, distribution and nature of inclusions and the effects of alloying on grain boundary and matrix/inclusion cohesion. In re-heated material at test temperatures studied the plane strain fracture toughness is influenced by similar factors to those which determine cleavage fracture strength.

The purpose of the study was to investigate the metallurgical interactions that occur during the brazing of zirconium with Ag-28Cu filler, with particular reference to their effect on mechanical properties. The ultimate aim was to provide information that would aid in the production of tougher brazed zirconium joints than are currently being obtained. The investigation was carried out in a number of stages: 1. A general literature survey of the metallurgy of brazed joints. 2. Zirconium brazed lap joints were made using either vacuum furnace or high frequency induction brazing. Interalloying was studied by optical and electron microscopy, X-ray diffraction and electron microprobe analysis. Interface layers were produced consisting of Cu4Zr, CuZr2, AgZr2 and Cu, distributed in a mixture between two sub-layers. Induction brazing produced high quality joints with interface layers thinner than those in vacuum brazed joints; a link between heat-up rate and wetting was observed. 3. Butt joints for mechanical testing were produced to optimum conditions. Instrumented impact testing showed that the toughest joints were those brazed with a reactive copper filler, although in all joints most of the energy absorbed was due to fracture initiation energy. 4. The greater toughness of the reactive copper brazed joints was due to a lack of flaws of any kind in their microstructure, which consisted of a eutectic of CuZr and CuZr2. In contrast, interface layer Ag-28Cu brazed joints contained shrinkage cracks and interfacial voids, along which fracture occurred.