An equilibrium theory of adhesion between elastic solids is developed. Adhesion is shown to depend on the interfacial surface energy and on the geometry and elastic constants of the adherent bodies. The theory is used to interpret the well-known adhesion tests - the pull-off, peel and scratch tests - and the spontaneous peeling of thin films is discussed. Experiments on contacts between Perspex and gelatine surfaces support the analysis.
It is shown that by properly controlling vibrational and charging conditions, the transition from disordered to ordered, densest packing of particles can be obtained consistently. The method applies to both spherical and nonspherical particles. For spheres, face centered cubic packing with different orientations can be achieved by monitoring the vibration amplitude and frequency, and the structure of the bottom layer, in particular. The resultant force structures are ordered but do not necessarily correspond to the packing structures fully. The implications of the findings are also discussed.
A theory for the effect of shrinkage stresses on the peel strength of a joint between rubber and glass is developed. The theory suggests that shrinkage weakens the joint, the weakening becoming more noticeable with rise in shrinkage strain and rubber film thickness. Peeling experiments on a rubber-glass bond verify the theory and justify a discussion of shrinkage in butt joints.
Applying an electric field across a poorly conducting material containing a crack causes a force to be exerted across the crack faces which resists crack opening, giving an electric adhesive effect. This paper presents a theory to account for this phenomenon, based on the idea that the electric potential developed across the opened crack faces by current flow around the crack provides a crack closing pressure which can be calculated. The theory is used to interpret experiments demonstrating adhesion between contacting semiconductors in an electric field. It may also be useful in explaining electrostatic precipitation, electrical adhesion between solid surfaces, and electro-gelation of powders and slurries.
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