Computer aided design and analysis of cold formed sections

The work reported in this thesis is concerned with the improvement and expansion of the assistance given to the designer by the computer in the design of cold formed sections. The main contributions have been in four areas, which have consequently led to the fifth, the development of a methodology to optimise designs. This methodology can be considered an `Expert Design System' for cold formed sections. A different method of determining section properties of profiles was introduced, using the properties of line and circular elements. Graphics were introduced to show the outline of the profile on screen. The analysis of beam loading has been expanded to beam loading conditions where the number of supports, point loads, and uniform distributive loads can be specified by the designer. The profile can then be checked for suitability for the specified type of loading. Artificial Intelligence concepts have been introduced to give the designer decision support from the computer, in combination with the computer aided design facilities. The more complex decision support was adopted through the use of production rules. All the support was based on the British standards. A method has been introduced, by which the appropriate use of stiffeners can be determined and consequently designed by the designer. Finally, the methodology by which the designer is given assistance from the computer, without constraining the designer, was developed. This methodology gives advice to the designer on possible methods of improving the design, but allows the designer to reject that option, and analyse the profile accordingly. The methodology enables optimisation to be achieved by the designer, designing variety of profiles for a particular loading, and determining which one is best suited.

Linking finite-element analysis and computer-aided drafting processes

The aim of this research was to investigate the integration of computer-aided drafting and finite-element analysis in a linked computer-aided design procedure and to develop the necessary software. The Be'zier surface patch for surface representation was used to bridge the gap between the rather separate fields of drafting and finite-element analysis because the surfaces are defined by analytical functions which allow systematic and controlled variation of the shape and provide continuous derivatives up to any required degree. The objectives of this research were achieved by establishing : (i) A package which interpretes the engineering drawings of plate and shell structures and prepares the Be'zier net necessary for surface representation. (ii) A general purpose stand-alone meshed-surface modelling package for surface representation of plates and shells using the Be'zier surface patch technique. (iii) A translator which adapts the geometric description of plate and shell structures as given by the meshed-surface modeller to the form needed by the finite-element analysis package. The translator was extended to suit fan impellers by taking advantage of their sectorial symmetry. The linking processes were carried out for simple test structures, simplified and actual fan impellers to verify the flexibility and usefulness of the linking technique adopted. Finite-element results for thin plate and shell structures showed excellent agreement with those obtained by other investigators while results for the simplified and actual fan impellers also showed good agreement with those obtained in an earlier investigation where finite-element analysis input data were manually prepared. Some extensions of this work have also been discussed.

Computer aided form roll design

Cold roll forming is an extremely important but little studied sheet metal forming process. In this thesis, the process of cold roll forming is introduced and it is seen that form roll design is central to the cold roll forming process. The conventional design and manufacture of form rolls is discussed and it is observed that surrounding the design process are a number of activities which although peripheral are time consuming and a possible source of error. A CAD/CAM system is described which alleviates many of the problems traditional to form roll design. New techniques for the calculation of strip length and controlling the means of forming bends are detailed. The CAD/CAM system's advantages and limitations are discussed and, whilst the system has numerous significant advantages, its principal limitation can be said to be the need to manufacture form rolls and test them on a mill before a design can be stated satisfactory. A survey of the previous theoretical and experimental analysis of cold roll forming is presented and is found to be limited. By considering the previous work, a method of numerical analysis of the cold roll forming process is proposed based on a minimum energy approach. Parallel to the numerical analysis, a comprehensive range of software has been developed to enhance the designer's visualisation of the effects of his form roll design. A complementary approach to the analysis of form roll design is the generation of form roll design, a method for the partial generation of designs is described. It is suggested that the two approaches should continue in parallel and that the limitation of each approach is knowledge of the cold roll forming process. Hence, an initial experimental investigation of the rolling of channel sections is described. Finally, areas of potential future work are discussed.

The development of a computer aided system for adaptive budgeting in a confectionery manufacturing firm

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Azidoprofen as a soft anti-flammatory agent for the topical treatment of Psoriasis

Azidoprofen {2-(4-azidophenyl)propionic acid; AZP}, an azido-substituted arylalkanoic acid, was investigated as a model soft drug candidate for a potential topical non-steroidal anti-inflammatory agent (NSAIA). Reversed-phase high performance liquid chromatography (HPLC) methods were developed for the assay of AZP, a series of ester analogues and their· degradation products. 1H-NMR spectroscopy was also employed as an analytical method in selected cases. Reduction of the azido-group to the corresponding amine has been proposed as a potential detoxification mechanism for compounds bearing this substituent. An in vitro assay to measure the susceptibility of azides towards reduction was developed using dithiothreitol as a model reducing agent. The rate of reduction of AZP was found to be base-dependent, hence supporting the postulated mechanism of thiol-mediated reduction via nucleophilic attack by the thiolate anion. Prodrugs may enhance topical bioavailability through the manipulation of physico-chemical properties of the parent drug. A series of ester derivatives of AZP were investigated for their susceptibility to chemical and enzymatic hydrolysis, which regenerates the parent acid. Use of alcoholic cosolvents with differing alkyl functions to that of the ester resulted in transesterification reactions, which were found to be enzyme-mediated. The skin penetration of AZP was assessed using an in vitro hairless mouse skin model, and silastic membrane in some cases. The rate of permeation of AZP was found to be a similar magnitude to that of the well established NSAIA ibuprofen. Penetration rates were dependent on the vehicle pH and drug concentration when solutions were employed. In contrast, flux was independent of pH when suspension formulations were used. Pretreatment of the skin with various enhancer regimes, including oleic acid and azone in propylene glycol, promoted the penetration of AZP. An intense IR absorption due to the azide group serves as a highly diagnostic marker, enabling azido compounds to be detected in the outer layers of the· stratum corneum following their application to skin, using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). This novel application enabled a non-invasive examination of the percutaneous penetration enhancement of a model azido compound in vivo in man, in the presence of the enhancer oleic acid.

Computer aided design and manufacture of form-rolls

Cold roll forming of thin-walled sections is a very useful process in the sheet metal industry. However, the conventional method for the design and manufacture of form-rolls, the special tooling used in the cold roll forming process, is a very time consuming and skill demanding exercise. This thesis describes the establishment of a stand-alone minicomputer based CAD/CAM system for assisting the design and manufacture of form-rolls. The work was undertaken in collaboration with a leading manufacturer of thin-walled sections. A package of computer programs have been developed to provide computer aids for every aspect of work in form-roll design and manufacture. The programs have been successfully implemented, as an integrated CAD/CAM software system, on the ICL PERQ minicomputer with graphics facilities. Thus, the developed CAD/CAM system is a single-user workstation, with software facilities to help the user to perform the conventional roll design activities including the design of the finished section, the flower pattern, and the form-rolls. A roll editor program can then be used to modify, if required, the computer generated roll profiles. As far as manufacturing is concerned, a special-purpose roll machining program and postprocessor can be used in conjunction to generate the NC control part-programs for the production of form-rolls by NC turning. Graphics facilities have been incorporated into the CAD/CAM software programs to display drawings interactively on the computer screen throughout all stages of execution of the CAD/CAM software. It has been found that computerisation can shorten the lead time in all activities dealing with the design and manufacture of form-rolls, and small or medium size manufacturing companies can gain benefits from the CAD/CM! technology by developing, according to its own specification, a tailor-made CAD/CAM software system on a low cost minicomputer.

Computer aided geometric design of form-rolls for NC manufacture

Conventional methods of form-roll design and manufacture for Cold Roll-Forming of thin-walled metal sections have been entirely manual, time consuming and prone to errors, resulting in inefficiency and high production costs. With the use of computers, lead time can be significantly improved, particularly for those aspects involving routine but tedious human decisions and actions. This thesis describes the development of computer aided tools for producing form-roll designs for NC manufacture in the CAD/CAM environment. The work was undertaken to modernise the existing activity of a company manufacturing thin-walled sections. The investigated areas of the activity, including the design and drafting of the finished section, the flower patterns, the 10 to 1 templates, and the rolls complete with pinch-difference surfaces, side-rolls and extension-contours, have been successfully computerised by software development . Data generated by the developed software can be further processed for roll manufacturing using NC lathes. The software has been specially designed for portability to facilitate its implementation on different computers. The Opening-Radii method of forming was introduced as a subsitute to the conventional method for better forming. Most of the essential aspects in roll design have been successfully incorporated in the software. With computerisation, extensive standardisation in existing roll design practices and the use of more reliable and scientifically-based methods have been achieved. Satisfactory and beneficial results have also been obtained by the company in using the software through a terminal linked to the University by a GPO line. Both lead time and productivity in roll design and manufacture have been significantly improved. It is therefore concluded that computerisation in the design of form-rolls for automation by software development is viable. The work also demonstrated the promising nature of the CAD/CAM approach.

Isotropic compression of mixtures of hard and soft spheres

The compaction behaviour of powders with soft and hard components is of particular interest to the paint processing industry. Unfortunately, at the present time, very little is known about the internal mechanisms within such systems and therefore suitable tests are required to help in the interpretative process. The TRUBAL, Distinct Element Method (D.E.M.) program was the method of investigation used in this study. Steel (hard) and rubber (soft) particles were used in the randomly-generated, binary assemblies because they provided a sharp contrast in physical properties. For reasons of simplicity, isotropic compression of two-dimensional assemblies was also initially considered. The assemblies were first subject to quasi-static compaction, in order to define their behaviour under equilibrium conditions. The stress-strain behaviour of the assemblies under such conditions was found to be adequately described by a second-order polynomial expansion. The structural evolution of the simulation assemblies was also similar to that observed for real powder systems. Further simulation tests were carried out to investigate the effects of particle size on the compaction behaviour of the two-dimensional, binary assemblies. Later work focused on the quasi-static compaction behaviour of three-dimensional assemblies, because they represented more realistic particle systems. The compaction behaviour of the assemblies during the simulation experiments was considered in terms of percolation theory concepts, as well as more familiar macroscopic and microstructural parameters. Percolation theory, which is based on ideas from statistical physics, has been found to be useful in the interpretation of the mechanical behaviour of simple, elastic lattices. However, from the evidence of this study, percolation theory is also able to offer a useful insight into the compaction behaviour of more realistic particle assemblies.

Visual performance of the human eye with soft hydrophilic contact lenses

The recording of visual acuity using the Snellen letter chart is only a limited measure of the visual performance of an eye wearing a refractive aid. Qualitative in addition to quantitative information is required to establish such a parameter: spatial, temporal and photometric aspects must all be incorporated into the test procedure. The literature relating to the correction of ametropia by refractive aids was reviewed. Selected aspects of a comparison between the correction provided by spectacles and contact lenses were considered. Special attention was directed to soft hydrophilic contact lenses. Despite technological advances which have produced physiologically acceptable soft lenses, there still remain associated with this recent form of refractive aid unpredictable visual factors. Several techniques for vision assessment were described, and previous studies of visual performance were discussed. To facilitate the investigation of visual performance in a clinical environment, a new semi-automated system was described: this utilized the presentation of broken ring test stimuli on a television screen. The research project comprised two stages. Initial work was concerned with the validation of the television system, including the optimization of its several operational variables. The second phase involved the utilization of the system in an investigation of visual performance aspects of the first month of regular daily soft contact lens wear by experimentally-naive subjects. On the basis of the results of this work an ‘homoeostatic’ model has been proposed to represent the strategy which an observer adopts in order to optimize his visual performance with soft contact lenses.

Computer-aided design, synthesis and screening of potential anti-microbial compounds

The work presented in this thesis falls into three main categories: The design and synthesis of potential anti-tuberculosis drugs targeting a mycobacterial esterase and the enzyme dUTPase; synthesis and anti-microbial SAR studies on a set of carboxamidrazones; synthesis and anti-microbial SAR studies on a set of thiosem icarbazones.