Error Estimation of DIC for Heterogeneous Strain States
Digital image correlation (DIC) involves certain errors during correlation, which are highly influenced by factors, e.g. image qualities, DIC parameters, and furthermore, degrees of deformation or strain states. In this contribution, attention is paid to the influence of strain states on the uncertainty of DIC, including the magnitude and the heterogeneity of the strains. A series of 2D-DIC numerical experiments are carried out on tensile specimens associated with finite element analysis (FEA). The specimens are made of 3 materials, i.e. steel DC06, steel DX54D+Z, and aluminium alloy Al6016, and cut into 3 different geometries, i.e. standard and 2 complex designs. Initial images were taken from these real specimens, which were all painted manually with random speckle patterns. Deformed images were obtained by imposing FE displacement fields on these undeformed initial images. Consequently, the errors source from imaging system are avoided, and only intrinsic errors of DIC itself are taken into account. The hardening behaviours of those materials in 3 different orientations were introduced to FEA for simulation, namely rolling direction (RD), transverse direction (TD) and 45o w.r.t. RD (45o). In FEA, homogeneous and heterogeneous strain states are achieved through applying uniaxial tension on two ends of the standard and complex specimens, respectively. The strain states are characterized by different material properties and geometries of specimens. DIC calculation are performed at various load steps to investigate the influence of the magnitude of the strain. Errors of the fields are compared among the different specimens to study the influence of the heterogeneity. In this contribution, the qualities of the speckle patterns are considered, since different patterns are applied to each experiment.
R. L. Burguete, M. Lucas, E. A. Patterson, S. Quinn
Y. Q. Wang et al., "Error Estimation of DIC for Heterogeneous Strain States", Applied Mechanics and Materials, Vol. 70, pp. 177-182, 2011