Pressure interfacial crack

It should be noted that these methods work well for inferring the interfacial crack propagation behaviour, but they cannot measure the conditions under which a crack will initiate. Estimates of the interfacial shear stress to initiate debonding can be obtained from indentation tests using an approximate stress analysis in which the coating is assumed very thin, so that stresses are approximately constant through the thickness [34]. In this model [58], the plastic zone below the indentation is modelled as a cylinder, which is replaced conceptually by a hole under an internal pressure (see Fig. 4), p, which is related to the indentation hardness of the material ... 

Other possible interfacial degradative mechanisms include the build up of osmotic pressure at the oxide/adhesive interface(6) (akin to the phenomenon of paint blistering by osmotic gradients), disbonding by alkali produced by the cathodic reaction in metallic corrosion(107), and the imposition of stress leading to bond stress-corrosion cracking( 108-110). 

When interpreting the data it should be realized that the equilibrium structure of the transferred monolayer may not be identical to that of the parent monolayer in the Uqnid interface. Interaction of the amphiphiles with the solid substrate (or with the predeposited layers) is probably different from that with the liquid interface and, furthermore, at the solid surface the amphiphiles do not experience the same, constant, interfacial pressure that keeps the parent monolayer in the original state. Due to all of this, structural rearrangements may occur during or after deposition. During the ageing process of the transferred film phase separation, terrace and crack formation may take place. Where the films kept in air are stable over several weeks or months, the ageing in water may occur within minutes or hours. 

The cross-sections of impression for different combination of specimen and indenter size are shown in from Figs. 13 to Fig. 16. For the observation of plastic zone immediately below the impression" . While there was little distinction in the fracture of spray film and the formation of plastic zone in different specimens, they presented clear differences depending on the indenter size. In case of indenter 1 mminterfacial debonding" . As the indenter size increased, the fracture tended to turn closer to the interfacial debonding. With smaller indenter, the indentation pressure is greater, to produce plastic deformation in the substrate. With 1 mmc[) indenter, plastic deformation occurred in proportion to the size of damage area, while with 4mmc[) indenter, the plastic... 

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