Moiré Patterns of Partial Derivatives of Displacement Components

Abstract

The knowledge of the partial derivatives of displacement components is essential in strain analysis. Two methods of determining these partial derivatives using moiré effects are presented in this paper. One consists of superposing two shifted copies of the same deformed grating of lines. The other consists of superposing two shifted copies of moiré patterns of displacement components. Explanations of the phenomena, based on the parametric properties of superposed families of lines, are given. Applications to the determination of the nonlinear deformation and strain tensor are included.