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.

Membrane Curvatures and Stress-strain Full Fields of Axisymmetric Bulge Tests from 3D-DIC Measurements. Theory and Validation on Virtual and Experimental results

Abstract: The bulge test is mostly used to analyze equibiaxial tensile stress state at the pole of inflated isotropic membranes. Three-dimensional digital image correlation (3D-DIC) technique allows the determination of three-dimensional surface displacements and strain fields. In this paper, a method is proposed to determine also the membrane stress tensor fields for in-plane isotropic materials, independently of any constitutive equation. Stress-strain state is then known at any surface point which enriches greatly experimental data deduced from the axisymmetric bulge tests. Our method consists, first in calculating from the 3D-DIC experimental data the membrane curvature tensor at each surface point of the bulge specimen. Then, curvature tensor fields are used to investigate axisymmetry of the test. Finally in the axisymmetric case, membrane stress tensor fields are determined from meridional and circumferential curvatures combined with the measurement of the inflating pressure. Our method is first validated for virtual 3D-DIC data, obtained by numerical simulation of a bulge test using a hyperelastic material model. Afterward, the method is applied to an experimental bulge test performed using as material a silicone elastomer. The stress-strain fields which are obtained using the proposed method are compared with results of the finite element simulation of this overall bulge test using a neo-Hookean model fitted on uniaxial and equibiaxial tensile tests.

Feature extraction and health monitoring using image correlation for survivability of leadfree packaging under shock and vibration

Abstract: In this paper, the feature extraction for health monitoring based on optical measurements of transient-strain from digital image correlation (DIC) in conjunction with ultra high-speed imaging has been investigated. Full-field measurement of transient strain have been made in various board assemblies subjected to shock in various orientations. Feature-extraction for health monitoring of leadfree area array architectures based on statistical pattern recognition has been presented. Previous researchers have measured the transient-dynamics of board assemblies with high-speed imaging in conjunction with high-speed image analysis for measurement of relative displacement, angle, velocity, and acceleration [Lall 2006, Che 2006], high-speed data-acquisition systems with discrete strain gages [Lall 2004, 2005, Liang 2005] and with accelerometers for measurement of transient acceleration [Dunford 2004, Goyal 2000, Seah 2005]. Degradation in confidence value gives a leading indication of component failure. Package architectures examined include-flex ball-grid arrays, tape-array ball-grid arrays, and metal lead-frame packages. Statistical pattern recognition techniques including, mahalanobis- distance approach, wavelet packet energy decomposition, and time-frequency (TFA) techniques have been investigated for system identification, condition monitoring, and fault detection and diagnosis in electronic systems. Explicit finite element models have been developed and various kinds of failure modes have been simulated such as solder ball cracking, package fall off and solder ball failure. Models developed include, smeared property models, Timoshenko-beam models, and explicit sub-models. Explicit finite-element models have been correlated with experimental data. The presented approach does not depend on continuity and therefore does not need daisy-chained devices for detection of failure.

Cluster approach based multi-camera digital image correlation: Methodology and its application in large area high temperature measurement

Abstract: A cluster approach based multi-camera Digital Image Correlation (DIC) system has been developed to quantify dynamic material response at temperature up to 1200 °C The Monochromatic Light Illuminated Stereo DIC technique was embedded to eliminate surface radiance at high temperature. The employed measurement system not only takes advantage of a conventional 3D DIC system, but also provides a feasible way to enlarge the measurement field without losing effective resolution in the area of interest. Two pairs of pre-calibrated CCD cameras are used to measure a piece of sheet nickel alloy. The view of each pair of cameras covers about half of the specimen. To guarantee the continuity of the evaluation result, an overlapped area that is covered by all four cameras is used in the setup. Unlike the conventional data stitching technique which stitches data from different pairs of cameras, our system with the cluster approach technique, maps all data points into a universal world coordinate system before evaluating the contour, displacement, and strain. To evaluate our system, a specimen was loaded with infrared heaters, and the dynamic contour, displacement, and strain field was evaluated. The methodology of the employed system is introduced in this paper. The system has the potential to be expanded with more cameras to measure a very large surface with one shot.