Interface adherence mechanism

Marshall, D.B. and Evans, A.G., Measurement of adherence of residually stressed thin-films by indentation. I. Mechanics of interface delamination. J. Appl. Phys., 56(10), 2632-2638 (1984). 

As the tension of the film is different from the tension of two single isolated interfaces, a contact angle, 0, is expected at the junction between adherent and free interfaces. This is depicted in Fig. 2.30. The mechanical equilibrium of the contact line at the junction between free and adherent interfaces dictates the value of the contact angle ... 

A distinction should be made between the bubbles which are formed by cavitation and those which occur naturally in the parent liquid or are induced by ultrasonic action (sparging). Cavitation bubbles, which range in size from infinitesimal to visible (40 pm and above) appear only when the radiating surface is activated and vanish apparently instantaneously when the power is turned off (in fact, they vanish within a half-cycle or 25 X 10 s at 20 kHz). Naturally occurring bubbles of entrapped air or other gases are most evident in freshly poured hot tap water as cloudiness or in still water as small bubbles adhering to the undersurface and the vessel walls. Sparged bubbles, which are those induced mechanically by external means such as ultrasonic action at or near the gas-liquid interface (the surface), tend to float in the liquid and even produce foam. 

The analytical approach developed by Schadler and Noyan, allows calculation of the stress redistribution in cracked triple layer systems. This approach assumes mechanical equilibrium of the cracked coating and the interlayer through perfectly adhering interfaces which transfer the applied stress to the substrate. It is thus possible to deduce expressions for stress distribution normal to the cracked film and shear stress distribution at the interlayer ... 

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