Digital image correlation

About: Digital image correlation is a research topic. Over the lifetime, 7842 publications have been published within this topic receiving 132166 citations.

Analysis of piles under oblique pullout load using transparent-soil models

Abstract: This paper presents an experimental investigation of internal deformation in transparent sand caused by a pile moving under oblique pullout loads using the digital image correlation (DIC) technique. Transparent sand used in this study is manufactured with fused quartz and a pore fluid (mixture of Norpar 12 and white mineral oil) with a matching refractive index. An optical system consisting of a linear laser, a charge-coupled device (CCD) camera, an optical platform, a frame grabber, and a computer is employed. During the test process, the speckle (which is the interaction between the transparent-soil matrix, impurities, entrapped air, and laser) is generated. The laser speckle images before and after soil deformation are used to measure the relative displacement field using the DIC technique. The belled wedge pile, conventional tapered pile, and equal section pile with the same volume, slenderness ratio L/D = 16.9, and oblique pullout loads at angles α = 0°, 45°, 60°, and 90° are conducted in transparent sand. The load-displacement response, oblique ultimate pulling resistances, internal deformation field, surface heaving, and failure mechanisms have been studied. The normalized values in this paper were compared with previously measured values. The results indicate that the optical system and transparent sand are suitable for studying soil deformation caused by pile–soil interaction under oblique pullout loading.

Fracture Characterization of Rolled Sheet Alloys in Shear Loading: Studies of Specimen Geometry, Anisotropy, and Rate Sensitivity

Abstract: Two different shear sample geometries were employed to investigate the failure behaviour of two automotive alloy rolled sheets; a highly anisotropic magnesium alloy (ZEK100) and a relatively isotropic dual phase steel (DP780) at room temperature. The performance of the butterfly type specimen (Mohr and Henn Exp Mech 47:805–820, 16; Dunand and Mohr Eng Fract Mech 78:2919-2934, 17) was evaluated at quasi-static conditions along with that of the shear geometry of Peirs et al Exp Mech 52:729-741, (27) using in situ digital image correlation (DIC) strain measurement techniques. It was shown that both test geometries resulted in similar strain-paths; however, the fracture strains obtained using the butterfly specimen were lower for both alloys. It is demonstrated that ZEK100 exhibits strong anisotropy in terms of failure strain. In addition, the strain rate sensitivity of fracture for ZEK100 was studied in shear tests with strain rates from quasi-static (0.01 s−1) to elevated strain rates of 10 and 100 s−1, for which a reduction in fracture strain was observed with increasing strain rate.

Quantitative Strain Analysis of the Large Deformation at the Scale of Microstructure: Comparison between Digital Image Correlation and Microgrid Techniques

Abstract: A comparative study has been carried out to assess the accuracy of the Digital Image Correlation (DIC) technique for the quantification of large strains in the microstructure of an Interstitial Free (IF) steel used in automotive applications. A microgrid technique has been used in this study in order to validate independently the strain measurements obtained with DIC. Microgrids with a pitch of 5 microns were printed on the etched microstructure of the IF steel to measure the local in-plane strain distribution during a tensile test carried out in a Scanning Electron Microscope (SEM). The progressive deformation of the microstructure with microgrids has been recorded throughout the test as a sequence of micrographs and subsequently processed using DIC to quantify the distribution of local strain values. Strain maps obtained with the two techniques have been compared in order to assess the accuracy of the DIC measurements obtained using the natural patterns of the revealed microstructure in the SEM micrographs. The results obtained with the two techniques are qualitatively similar and thus, demonstrate the reliability of DIC applied to microstructures, even after large deformations in excess of 0.7. However, an average error of about 16 % was found in the strain values calculated using DIC.