An analysis of methods of determination of strain using dividing grids

Various methods of calculation of the components of the tensor of strains _ij from the displacements of the nodes of the dividing grid U_ij are analyzed, including by the method of approximation by polynomials of the power n=1–5, smoothing of U_ij, and approximation of polynomials of the powern=5–7 and by methods of finite elements and numerical differentiation. A comparison of the calculated data with the results of experimental measurement of the field of local strains in Mg-1.5% Mn-0.3% Ce alloy with a grain size of 100 m using a grid with a base of 50 m showed that the method of finite-element approximation most adequately reflects the real picture of distribution of strains _ij. Statistical parameters characterizing the field of _ij are discussed.Translated from Problemy Prochnosti, No. 4, pp. 11–16, April, 1991.