On the applicability of digital image correlation method in extracting the higher order terms in stress field around blunt notches

Abstract

Accurate and deep understanding of the stress field has a key role in designing and optimizing the engineering structures. The main objective of the present article is to experimentally investigate the stress field around various blunt notches by means of the digital image correlation (DIC) method. First, several mode I tests were conducted using two types of specimens, namely single edge notch tension (SENT) and single edge notch bending (SENB), each consisting of three different notches (U, VO, and Keyhole). Then, the optical method of DIC was used to determine the stress field around the notch tip by calculating the coefficients of singular and higher-order terms (HOTs) for each notch type. To do so, the output displacement field of the DIC measurements was considered as input data for a computer program, and the coefficients of the stress field were calculated by the least square method (LSM) and an over-deterministic approach. Moreover, the effects of several geometry parameters like notch opening angle and notch tip shape on the stress distribution around the notch were discussed in detail. Finally, the precision of the calculated notch stress intensity factors (NSIFs) and the coefficients of HOTs were studied by comparing the DIC results with those obtained from the finite element (FE) analysis. It is also shown that HOTs of stress field have considerable contribution in more precise determination of the stress field around notches.