Determination of stress in coatings by the bending strip method in the case of large displacements

Abstract

The classical formulae derived through the simple plate theory for determining stress in coatings by the bending strip method have been widely used to date. However, their application is limited to bending displacements, which are small compared to the thickness of the strip. Since the actual measured displacements are often greater, the question for the applicability of this theory arises. To the best of our knowledge, a satisfactory answer to this question has not yet been presented. There are publications stressing only the danger of bifurcation of experimental specimens at high curvature values when this theory becomes inapplicable. The present work provides an answer by solving the geometrically non-linear problem of the theory of elasticity involving large deflections of coated strips by the finite element method. Data on the errors of classical formulae and two practically applicable conditions for reaching a minimal admissible error are given.