Argon TIG arc temperatures have been measured for a wide range of arc parameters using the 'Fowler-Milne' spectroscopic method. Prompted by widespread disagreement amongst temperatures published by previous groups, a detailed investigation has been carried out into those experimental and theoretical aspects of the measurement process that may have led to incorrect results. The tests have included the variation of experimental parameters, the choice of Abel inversion procedure, and the calculation of argon species number densities and partition functions. The existence of equilibrium within the TIG arc has been investigated by determining temperatures with a number of argon emission lines. Significant differences 'in derived values of the temperatures were observed within 1mm of the tungsten cathode tip, smaller variations were observed over the remainder of the arc. The results indicate that large scale departures from a Boltzmann distribution amongst argon atom excited states exists close to the tungsten tip, deviations decrease with increasing distance from the tip but do not disappear completely. lt is believed that the breakdown of equilibrium within the argon TIG arc may help to explain the disagreement in temperatures obtained by past groups that have used spectroscopic methods. Despite evidence for non-equilibrium within the arc. results from previous groups suggest that derived values of .the temperatures are substantially correct in the main body of the arc. The detailed temperature maps provide useful information on temperature changes with arc parameters for the purposes of modelling and understanding of the arc.

Tensile strength-modulus relationships established for postvulcanised latex films have been found to show characteristics of both prevulcanised latex and dry rubber curves. The curves depend upon the accelerator system used, as with dry rubber. They passed through their maxima after which tensile strength fell, with the down-turn less pronounced than for prevulcanised latex but greater than for dry rubber. The results suggest that postvulcanised latex films remain particulate rather than homogeneous. Processes known to affect prevulcanised latex films were applied to postvulcanised latex films. These included stirring and maturation of latex, different conditions for drying films and leaching with water and solvents, but only stirring had a significant effect. Stirring was essential to produce homogeneous latices for films with consistent chemical compositions and physical properties.

No description available.

Ceramic injection moulding is already established as a production technique for complex shaped ceramic components. However the process is limited to thin section mouldings generally not exceeding a wall thickness of 10 mm. The global objective of this work is to describe and understand the aetiology of defects which preferentially appear in thick injection moulded ceramics, and to find ways to overcome these problems. The following stages are examined mould-filling, solidification, binder removal and sintering. Different moulding techniques; conventional moulding, modulated pressure moulding, insulated sprue moulding and low hold pressure moulding were applied. Moulding thicknessw as systematicallyv aried (15,20,25, and 35 mm).. Hold pressures and times were closely controlled and found to be decisive processing parameters for defect creation. The use of insulated sprue moulding prevented void formation in 25 nun thick mouldings and the application of low and constant hold pressures (>5 MPa) led to a reduction of residuals tressesin the mouldings. An intensive study was carried out on the binder removal stage in which the catalytic removal of the polyacetal binder enabled removal of the binder from sections of 35 nun thickness. The reaction and transport kinetics during binder removal were studied and close observations were made out on various defects which could appear during interrupted binder removal. Differential shrinkage of the ceramic components during sintering was studied and could be tracked back to flow-induced particle alignment during mould filling. The sintering behaviour of the alumina feedstock used in this study was compared with an equiaxed zirconia powder injection moulding suspension. The phenomenon of jetting in large section mouldings and the creation of spherulites during solidification of the polymer were found to influence moulding structure.

No description available.

In der wissenschaftlichen Diskussion wie auch auf betrieblicher Ebene werden Fehlmengenkosten bei mangelhafter Lieferfähigkeit mit Hinweis auf einen enormen und damit unwirtschaftlichen Erhebungsaufwand meist ignoriert. Stattdessen werden oft Sicherheitsbestände definiert, die ohne ausreichende Berücksichtigung der Kundenbedürfnisse und integrierte Modellansätze mögliche Bedarfs-spitzen auf Herstellerseite abfedern sollen. Findet doch eine Modellierung in quantitativen Ansätzen stochastischer Lagerhaltungsmodelle statt, so fehlen aus Sicht eines Investitionsgüterherstellers oft wichtige Parameter oder sind unzureichend modelliert. Die vorliegende Arbeit verfolgt das Ziel, Fehlmengenkosten auf der einen und Bestandskosten auf der anderen Seite inhaltlich genauer zu beleuchten und in eine grundsätzliche Beziehung zueinander zu setzen. Beide Kostenblöcke werden in der größtmöglichen Granularität in ein distributionslogistisches Modell überführt, sodass Determinanten, Hierarchien und Wechselwirkungen in einen nachvollziehbaren Gesamtzusammenhang gebracht werden. Zu diesem Zweck werden relevante Distributionsmodelle bei stochastischer Nachfrage geprüft und auf ihre Relevanz für die Problemstellung dieser Arbeit hin analysiert. Dabei konnte festgestellt werden, dass weder die verschiedenen Kostenarten von Fertigwarenbeständen ausreichend identifiziert, noch die unterschiedlichen Ausprägungen von Fehlmengenkosten umfänglich abgebildet wurden. Vor diesem Hintergrund kristallisiert sich heraus, dass existierende Modelle und Rechenbeispiele bei deren Umsetzung auf eine Problemstellung in der betrieblichen Praxis als weitestgehend untauglich eingestuft werden müssen. Im Sinne eines wertorientierten Bestandsmanagements wird in besonderer Weise darauf geachtet, dass kundenorientierte Strategien hinsichtlich eines festzulegenden Lieferservicegrades so festgelegt werden, dass keine isolierte Betrachtung von Bestandskosten einerseits und Fehlmengenkosten andererseits vorgenommen wird. Dadurch konnte ein klareres Bild geschaffen werden, dass einseitige Bestandssenkungen zwangsläufig erhöhte Fehlmengenkosten in definiertem Umfang nach sich ziehen. Diese können die Lieferfähigkeit über einen längeren Betrachtungszeitraum so negativ beeinflussen, dass das Nachfrageverhalten nachhaltig geschädigt wird und im Extremfall zu einem Abwanderungsverhalten der Kunden führt. Durch die Modifizierungen einiger wichtiger Prämissen und Modellparameter, welche die Merkmale der Investitionsgüterindustrie in besonderer Weise berücksichtigt, wurde ein dynamisches Entscheidungsmodell entwickelt, in dem nachvollziehbar eine nützliche Symbiose zwischen theoretischer Erkenntnis und praktischer Problemstellung geschaffen werden konnte. Diese Arbeit leistet damit einen wichtigen Beitrag, die oftmals auf reine Bestandssenkungen fokussierte Diskussion ohne adäquaten Modellansatz weitestgehend zu versachlichen und auf eine faktenbasierte, quantitative Grundlage zu stellen. / In scientific discussion as well as on company levels, out-of-stock costs are often ignored in case of inadequate delivery capacity, with reference to an enormous and thus uneconomical analysis effort. Instead, safety stocks are often defined which are designed to cushion possible demand peaks on manufacturer's side without sufficient consideration of customer requirements and integrated model approaches. If modeling is carried out in quantitative approaches of stochastic inventory models, important parameter from an industrial goods manufacturer point of view are often missing or insufficiently modeled. The present thesis aims to elucidate out-of-stock costs on one hand and inventory costs on the other, and to establish a fundamental relationship with each other. Both cost pools are analyzed with its largest possible granularity into a distributive-logistic model, so that determinants, hierarchies and interactions are brought into a post-executable overall context. For this purpose, relevant distribution models for stochastic demand are examined and analyzed for their relevance for the problem definition of this paper. It was found that neither the different cost types of finished goods were adequately identified nor the different manifestations of out-of-stock costs were shown. Against this background, it emerges that existing models and sample calculations must be classified as largely unsuitable in their implementation to a problem in the operational practice. In the sense of value-oriented inventory management, particular attention is paid to the fact that customer-oriented strategies with regard to a service level to be defined are determined in such a way that no isolated consideration of inventory costs on one side and out-of-stock costs on the other side are undertaken. It gives a clearer picture that unilateral inventory reductions inevitably lead to increased out-of-stock costs to a defined extent. This situation may have a negative impact on the ability to deliver over a longer period of time so that demand behavior is sustainably damaged and, in extreme cases, leads to a churning behavior of the customers. By modifying some important premises and model parameters, which take particular account of the characteristics of industrial goods industry, a dynamic decision-making model was developed in which a useful symbiosis between theoretical knowledge and practical problem-solving could be established. Thus, this thesis makes an important contribution to largely disregard the discussion focused on pure inventory reductions without an adequate model approach and to put it on a factual, quantitative basis.

No description available.

No description available.

One of the fundamental concepts in automated garment assembly is that the orientation of a fabric panel should never be lost. However, if a panel does become distorted, several techniques, such as vision, air flotation tables, and vibratory conveyors are available to restore the orientation. This thesis has investigated the behaviour of a fabric panel on a vibratory table. Several table parameters such as amplitude of vibration, frequency and angle of inclination, together with some important fabric properties as friction and compressibility are required to understand the behaviour. However, most work on friction in textiles considers fibre-fibre or fabric-fabric friction, which is not appropriate to this and so low force frictional properties between unloaded fabric and engineering surfaces (i.e., aluminium, Formica and rubber) have been studied. The influence of several experimental variables on friction is demonstrated, in particular, the effect of humidity and velocity. Further, an in depth study is made on the stick-slip of fabric panels wherein a novel measuring technique is introduced. An estimate of the damping, which is required to model the fabric, has been obtained from an in-plane vibration test. The second significant fabric property to be studied is the compression both static and impact. Again, only low-force compression tests are carried out since these are the typical forces experienced by fabrics on a vibrating table. The static compressibility of knitted and woven materials is verified with van Wvk's equation. which gives a near indistinguishable fit with the experimental data.

A study of the minimum tooling requirements and strategies for efficient operation of Flexible Manufacturing Systems, FMS's, in Assembly set Production, ASP, i.e production in sets of parts to completely assemble one or more product units, is presented in this research work. The main investigating tool is a simulation model. With this model the tool groups to be loaded into machines and fixtured pallet requirements were studied in conjunction with two scheduling rules. One is a FCFS rule and the other is a new rule, called MRPAS, which schedules work on the basis of the number of parts still unfinished belonging to an Assembly Set. The results of the research work show that ASP can be efficiently carried out in FMS's. However this requires that a good system set-up and adequate operating strategies are used. In particular appropriate tooling levels and good tooling configurations,TC's, i.e. combinations of tools in groups to be loaded into the machines, must be established to achieve high FMS performance. Tooling combination and duplication heuristic rules and the simulation model can be used for achieving this aim. The heuristic approach is shown to be necessary due to the impossibility, in a reasonable time, of evaluating the performance of FMS's under the large number of alternative tooling configurations which are possible. The level of fixtured pallets used can also have a great influence on system performance. Appropriate levels of these resources to operate FMS's for given TC's can be established using the methodology developed in this work. It is also important that good scheduling rules are used. In the cases studied, the MRPAS rule produces the best performance expressed as the combination of FMS utilization and production of complete assembly sets. Moreover a very small assembly set batch size, ASBS, i.e. number of AS released together into the FMS, is likely to be preferable. In the cases studied an ASBS of one performed best overall.