Brian Ralph

Determination of the cation content of alginate thin films by FTi.r. spectroscopy

Abstract Different sodium alginates derived from Laminaria hyperborea, with various mannuronate/guluronate (M/G) ratios and molecular weights, were immersed in calcium chloride solution and converted to mixed sodium/calcium salts. Thin films were obtained and studied using Fourier transform infrared spectroscopy (FTi.r.). FTi.r. spectra were recorded as a function of time and the ion exchange between sodium and calcium monitored. Peak shifts, difference in peak shapes and the appearance of new peaks were observed, and some explanations of the phenomena observed are proposed. In parallel, the samples were analysed quantitatively by atomic absorption/emission spectroscopy. From these results, peak wavenumbers derived from the FTi.r. spectra could be correlated quantitatively to the sodium and calcium content.

The processing of metal matrix composites — an overview

Abstract This overview begins by considering the mature situation for polymer matrix composites (PMCs). After a further short section devoted to ceramic matrix composites (CMCs), the main text is devoted to the variety of routes available for processing metallic matrix composites (MMCs). These are divided into those where the main steps are performed in the solid state and those where the process route involves a stage where the matrix is molten. Some discussion is also given to the thermomechanical processing of MMCs and of their properties.

An investigation into welding parameters affecting the tensile properties of titanium welds

Abstract Grain size and amount of martensite formation affect the tensile strength of the alloy and these two factors are in turns related to the cooling rate of the welding process. There was found a trend of decreased tensile strength with the increase of welding heat input and a trend of increased tensile strength with the increase of welding cooling rate. Considering the effect of cooling rate on ductility, it was found that the higher the cooling rate, the larger is the relative elongation and hence the higher the welds ductility.

The relationships between tensile properties and hole expansion property of C-Mn steels

In order to investigate the effects of the microstructure and chemical compositions on the hole expansion property of C-Mn steels, four C-Mn steels were used and heat treated into different structures. The influences of the tensile properties on the hole expansion property were also investigated. It has been found in this paper that C-Mn steels with a high ratio of yield strength to ultimate tensile strength usually have a good hole expansion property. A high silicon content in solid solution can improve the hole expansion property. Carbon has a significant detrimental effect on the hole expansion property.

Synthesis of α-silicon nitride powder from a polymeric precursor

Abstract Methylcyclosiloxanes and methylcyclosilazanes prepared using dichloromethylsilane have been reacted together to prepare a copolymer which was pyrolysed to give a ceramic powder. The copolymer was characterized using proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier transform infra-red spectroscopy (FT-IR). Thermogravimetric analysis of the pyrolysis process and reactions which could occur during conversion of the copolymer to the ceramic are discussed. The product, which was found to be amorphous, was also studied using FTIR, crystallized by re-heating and characterized using FT-IR, X-ray techniques and scanning electron microscopy. It was identified as α-silicon nitride and its characteristics are compared with a conventionally prepared, widely used, commercially available grade of silicon nitride. The α-silicon nitride synthesised in the present work contains a wide range of particle morphologies, varying from needles (500 nm in length and 100 nm in width) to equiaxed agglomerates (200–500 nm in size with a substructure in the size range 50–120 nm).

A multi-mode extrinsic Fabry - Pérot interferometric strain sensor

This paper reports on the fabrication and evaluation of a multi-mode extrinsic Fabry - Perot interferometric (EFPI) sensor which is capable of measuring both tensile and compressive strains. A scanning monochromator was used to measure the absolute cavity length of the EFPI sensor. Sensors of this type were embedded within a 16-ply carbon-fibre-reinforced epoxy composite and tested under quasi-static tensile and compressive loading conditions. Excellent correlation was observed between the EFPI sensor and a surface-mounted extensometer. The sensor system can operate in the strain range from -1 to 1% with an accuracy of better than 30 micro-strain. Preliminary results indicated that the sensor design was relatively insensitive to temperature in the range 38 - 180 . An analysis of the relationship between the insensitivity and the sensor geometry is also presented.

The development of deformation substructures in face-centred cubic metals☆

Abstract The development of dislocation cells in polycrystalline aluminium and nickel has been evaluated over a tensile strain range, 0.05–0.30, using transmission electron microscopy. The results of the two test series are compared. Measurements of both the cell sizes and relative cell misorientations have been made, the latter using microdiffraction. The results are then compared with previous studies from the literature.

The grain boundary character distribution effect on the flow stress of polycrystals : The influence of crystal lattice texture

Abstract The grain size of a polycrystalline aggregate has an important effect on its properties. Several properties of materials, such as the yield and flow stresses, ductility and hardness have been suggested to show a linear dependence on (average size of grains) −1 2 . A number of models which justify the grain size effect are based on the assumption that the grains in a polycrystal have the same size and the grain boundaries the same properties. Grain boundaries are characterized by differences in their structure and, as a result, in their properties. An experimental study of the grain boundary strengthening effect in a 316L austenitic stainless steel has been carried out on a series of specimens obtained employing a powder-forming process and produced by conventional thermo-mechanical processing. The Brinell hardness was measured and analysed as a function of (grain size) −1 2 . The experimental data, in general, confirm the Hall—Petch relationship. A significant difference is observed in the values of the KH constants. This difference is discussed in terms of the influence of crystal texture on the strengthening effect of the grain boundaries.

A quantitative description of recrystallization and grain growth in single phase b.c.c. iron

This paper provides a description of the geometrical aspects of static recrystallization in α-Fe. Geometrical properties of two-dimensional sections, volume, shape and spatial distribution of nuclei/grains have been measured and from them, using stereological methods, three-dimensional microstructural evolution has been followed. The results show that recrystallization nuclei in α-Fe form clusters and that the nucleation of defect-free nuclei and grain growth occurs concurrently during recrystallization. The recrystallization process is characterized not only by changes in the size of nuclei/grains but also by alterations in their shape.

Self-sensing E-glass fibres

Abstract The primary aims of this study were to demonstrate that conventional reinforcing E-glass fibres could be converted to act as waveguides. This was achieved by selecting and applying appropriate cladding material onto the glass fibre bundle. Three classes of cladding materials were evaluated: epoxy, polyurethane and sol–gel. The light transmission characteristics through the E-glass waveguides was evaluated and compared. The epoxy and polyurethane cladding were found to be superior compared to the sol–gel coated fibres in terms of the quality of the coating and the light transmission intensity over specified lengths. The effect of fibre-end preparation on the light transmission characteristic was also investigated. The feasibility of conducting in situ tensile tests where the light transmission intensity was passed through the E-glass fibres was demonstrated successfully. This in situ technique was capable of highlighting differences in the macroscopic tensile failure modes obtained using the various cladding materials.