The Importance of Material Surfaces to the Engineer

Recent experimental work involving surfaces is described, and it is shown that by measuring the distributions of asperities, it is possible to evaluate the nature and size of contact for various surface loads. The removal of adsorbed gas layers from the surfaces of crystals is shown to affect the friction markedly, while the “ploughing” term in the frictional cooefficient emerges as the important factor in explaining the anisotopy of friction found on some crystalline solids. The effect of microdefects on the strength of glasses and their removal by etching is described. The behavior of glasses is compared with that of hard polymers such as lucite. Finally, the property a surface has as a “free boundary” in stress wave propagation is considered, with particular reference to the fracture behavior of brittle solids in plate form.