Residual coating strain

From the residual coating strain, the residual coating stress can be calculated assuming a two-dimensional stress state in the thin coating. 

In this equation, essentially similar to the condition for cracking of a lap joint or removal of a film by applying a compression (Fig. 10b), W is the work of adhesion, E is the Young modulus of the film, d its thickness and e the residual elastic strain (or o the elastic stress) in the coating. Experimental results confirmed this theory for elastomers adhering to glass. For biaxial tension, is replaced by cr ( 1 - v ), where v is the Poisson ratio. 

This photoelastic stress analysis is a technique for the nondestructive determination of stress and strain components at any point in a stressed product by viewing a transparent plastic product. If not transparent, a plastic coating is used such as certain epoxy, polycarbonate, or acrylic plastics. This test method measures residual strains using an automated electro-optical system. 

Measurements of residual stress and strain, Young s modulus and adhesive bonding strength of the hydroxyapatite coating after immersion in HBSS showed... 

Of further interest was the finding that residual strain was independent of applied coating thickness in the case of three low-boiling solvents but increased with thickness with high-boiling solvents (68). Pigmented systems also show a dependency on loading 70). 

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