Details of the problems and links to reports



AKZO: Optimal blower design

In some spinning processes, split blowers are used to transport and stretch filaments. Pressurised air is forced through a nozzle to create a high speed flow. The objective of the study is to minimise the pressurised air while maintaining sufficient frictional forces on the surface of the filaments. Probably one of the main variables is the geometry of the blower.

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WS Atkins: Cracking and buckling in ship bulkheads

An important cause of bulk carrier loss [1] is ingress of sea water owing to cracks in the side shell as a consequence of main frame deterioration and the subsequent failure of transverse bulkheads adjacent to the flooded hold. When the hold is flooded the stresses in the bulkhead are known to exceed yield and the bulkhead to have undergone slight distortion [2]. The vertical bulkheads are corrugated and have upper support from cross deck strips. Typical initial damages are cracks in the joint between bulkhead corrugations and deck plating due partly to corrosion. These can lead to portions of the cross deck strip becoming detached from the bulkhead. Pressure on the ship sides can then cause the bulkhead and cross deck strip to buckle, with minor and local buckles on the bulkhead leading to shear buckling of the whole structure.

The purpose of the Study Group will be an investigation of this cracking and buckling process.

[1] Det Norske Veritas report, Bulk carrier losses, Nov. 1991
[2] Lloyd's List, Letter from J Bell (IACS President), Feb. 1997

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AEA Technology: Risk estimates (obtained from highly skewed distributions)

In radiological exposure, risk is the probability of a serious health effect as a result of that exposure. This is proportional to the expectation of annual dose. The aim of probability safety assessment is to estimate the estimated dose as a function of time, however there is no expert opinion of the PDF of the dose information on which comes from the observed distribution. Errors arise in estimations when this is highly skewed.

The problem is to estimate this error given various assumptions on the form of the distribution.

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ELKEM: (i) Electrode paste briquette softening

In electrical smelting, current is supplied through electrodes which are gradually consumed. These electrodes are made of paste which flows under increasing temperature. The paste is charged by adding paste briquettes on top of the electrode which soften and flow to form a dense fluid which is baked to form the solid electrode. When producing electrodes rapidly the softening/flow process can be incomplete due to trapped air leading to breakages.

The objective of the Study Group is a mathematical analysis of this process which will allow a transfer of laboratory measurements to conditions for real electrodes.

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ELKEM: (ii) Homogenisation of thermal and electrical properties of the Søderberg electrode

Current is supplied to a Søderberg electrode by copper clamps that are attached to the steel casing around the electrode. From this casing steel fins run into the paste to enhance current transport, creating a non-uniform distribution of current and temperature within the paste.

The aim for the Study Group is to determine whether a homogneisation approach can be used to reduce the problem to one with axial symmetry.

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Food Sciences: (i) Determining thermal properties of food

The composition of a food substance can be inferred (in part) from its thermal properties. These can in turn be measured using a thermal probe. In a previous Study Group the effectiveness of using a single probe was considered. The current investigation will extend this to look at optimal placings of several probes so that repeated thermal measurements are made (with associated errors), the food composition can be accurately calculated and errors in the determined composition estimated.

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Food Sciences: (ii) Micro-waving food

Susceptors are food containers made to absorb electromagnetic energy which heat up and brown the food. Unfortunately components of the plastics on the containers migrate into the food.

The questions for the Study Group are of estimating the temperature of the receptors and also in improving the uniformity of the micro-wave heating.

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ICI: Mudcracking in drying paint

Thicker coatings of paint made up of water, polymer latex, titanium dioxide pigment and with no organic solvents, exhibit mudcracking when they dry. This is due to a build up of stress in the drying film. There is a need to develop a theory of mud mechanics which shows the role of the pigment volume concentration in the paint thickness and the latex viscosity in developing stress in the film.

The aim is to reduce the build up of stress in the drying film to avoid crack initiation.

[Download report (postscript file)]


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