Six studies by the Authors in geotechnical image analysis are reported. These were: (a) consistency ratio mapping for tilted scanning electron micrographs of rough surfaces; (b)semi-variance mapping for aerial photographs; (c) mathematical morphology for bore-hole layouts; (d) computer assistance for bore-hole logging; (e) the circular Hough Transform for particle shapes; (f) frame slip. (a) and (b) are methods for textured images. (b) to (e) are aspects of site investigation. (f) is an artefact which might be widespread.

In studying soil microstructure, the orientations of soil particles and of the voids between them are two of the most important factors. In this Paper, the directed vein method and the convex hull method are proposed for automatic orientation analysis of soil microstructure. In the directed vein method a directed vein image of the boundaries of the particles in an electron micrograph of soil structure is constructed using a chain code, and the expected directions of a directed vein are calculated to provide the orientation of the vein. In the convex hull method simple polygons are constructed from the boundaries, the convex hulls of the simple polygons are built up, and the longest diagonal of each convex hull is selected, the direction of which is taken as the orientation of the particle. Before either method can be applied, image preprocessing must be carried out to find the boundaries of the particles. Both methods involve simpler programming, faster computing and less storage than do other methods. Les orientations des particules du sol et des vides entre ces particules représentent deux des facteurs les plus importants dans I'étude de la microstructure des sols. L'article propose pour I'analyse automatique des orientations dans la microstructure des sols une méthode dite à veine dirigée et une méthode dite à enveloppe convexe. Dans la méthode à veine dirigée on construit, à I'aide d'un code à chaîne une image à veine dirigée des limites des particules dans un micrographe électronique de la structure du sol, après quoi on calcule les directions attendues d'une veine dirigée pour fournir I'orientation de la veine. Dans la méthode à enveloppe convexe on construit des polygones simples à partir des limites, on construit des enveloppes convexes de polygones simples et on choisit la diagonale la plus longue de chaque enveloppe convexe, sa direction est admise comme I'orientation de la particule. Avant I'application de I'une ou de I'autre de ces méthodes il faut prétraiter I'image afin d'obtenir les limites des particules. En comparaison avec d'autres méthodes, ces deux méthodes présentent I'advantage de programmes simplifiés, de calculs plus rapides et de mémoires réduites.

Measurements of the electric breakdown fields of films of NaCl, LiF and cryolite (Na3AlF6) are reported. The films were tested in vacuum, immediately after deposition, with voltages increasing linearly at a rise rate which was normally about 10 V msec-1. The electrodes were of evaporated Ag, Al, or Au. Ag appears to behave anomalously, possibly as a result of migration in the strong applied field. The results are lower than would be expected on the basis of published values for bulk single crystals, the breakdown field in a film 1000 A thick being of the order of 1 MV cm-1 in all the dielectrics studied. The breakdown field was found to increase with decreasing film thickness, and also, in cryolite, to increase with the rise rate of the applied voltage. Some evidence that the latter effect also occurs in NaCl and LiF was found. It is suggested that the depression of the breakdown field is due to the structure of the layers. Thus it may not be correct to assume that a disordered structure always leads to an increased electric strength. In view of the possible effects of the structure, the thickness dependence of the breakdown field cannot be taken as conclusive evidence for an ionization mechanism of breakdown.

The microstructure and properties of the composite TiN–Ti–Al type titanium nitride surface layer with a sub-layer of titanium and aluminium produced on AZ91D magnesium alloy using a hybrid PVD method including final sealing by hydrothermal treatment were investigated. The results were analysed in terms of the microstructure–properties correlation, to approach the role of the sub-layers and the mechanisms involved in the properties improvement. The microstructure investigations indicate that the composite titanium nitride layers are tight and have nano-crystalline, diffusive character and multi zone microstructure of the type TixOy–TiN–Ti–Al–Al3Mg2–Al12Mg17. The significant corrosion resistance improvement of the AZ91D alloy obtained using the sealed composite titanium nitride layers was found to be the result of a synergistic mechanism which combined hydrothermal treatment of the layer with an action of aluminium sub-layer which is critical to make the sealing effective. The diffusive bonding via Mg–Al zone improves adhesion and the load bearing capacity of titanium nitride layers in wear conditions.

Measurements have been made by multiple beam interference methods using Fizeau fringes and fringes of equal chromatic order to obtain the variation of phase change on reflection as a function of film thickness for chromium films deposited by evaporation on glass substrates. The results do not agree closely with theoretical curves but this has been shown to be due to the inhomogeneity of the chromium films and the deviations from theory have been explained in terms of a structural model based on independent evidence. The experimental curve has been used to explain anomalies which have been reported previously in measurements of the thickness of silver films by multiple beam interference methods when chromium is used as the reflecting overlayer.