Simple method of using strain gages to estimate stress fields near a notch in structures subject to large deflections

This study set out to estimate the stress fields in notched plates subject to large deflections. Because there are no general solutions to the von Karman equations defining this problem, the goal of the authors was to estimate the stress field for a large-deflection problem by superposing the stress fields of two solvable linear problems, that is, a bending problem and a plane problem. This paper described the procedure for estimating the stress fields in a plate with a circular hole, subject to a large deflection. By using strain gages and the equations describing the stress fields near the root of a notch in a plate subject to out-of-plane bending and in-plane deformation, the unknown coefficients of the equations were determined by the stress values obtained from rosette-type strain gages and the method of least squares. The rosette-type strain gages are located on a circular arc with a radius that is 1.5 times greater than the notch root radius. The estimated maximum stress values at the notch root were compared with those obtained by finite element analyses. The estimated values were found to be nearly equal to those obtained by finite element analysis, provided the ratio of the maximum deflection to the plate thickness is less than 0.8.