Topic
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.
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TL;DR: In this article, a simple procedure for the characterization of the constitutive behaviour of welds is presented, based on the Digital Image Correlation (DIC) for accessing local strain fields in transverse weld tensile samples and the stress distribution is calculated taking into account local strain data and thickness variation across the samples.
134 citations
TL;DR: The digital image correlation method is extended to the study of transient deformations such as the one associated with a rapid growth of cracks in materials, and the entire crack tip deformation history, from the time of impact to complete fracture is mapped.
Abstract: The digital image correlation method is extended to the study of transient deformations such as the one associated with a rapid growth of cracks in materials. A newly introduced rotating mirror type, multichannel digital high-speed camera is used in the investigation. Details of calibrating the imaging system are first described, and the methodology to estimate and correct inherent misalignments in the optical channels are outlined. A series of benchmark experiments are used to determined the accuracy of the measured displacements. A 2%-6% pixel accuracy in displacement measurements is achieved. Subsequently, the method is used to study crack growth in edge cracked beams subjected to impact loading. Decorated speckle patterns in the crack tip vicinity at rates of 225,000 frames per second are registered. Two sets of images are recorded, one before the impact and another after the impact. Using the image correlation algorithms developed for this work, the entire crack tip deformation history, from the time of impact to complete fracture, is mapped. The crack opening displacements are then analyzed to obtain the history of failure characterization parameter, namely, the dynamic stress intensity factor. The measurements are independently verified successfully by a complementary numerical analysis of the problem.
134 citations
TL;DR: In this paper, the location of the crack tip, the fracture initiation toughness and the fracture propagation toughness were calculated using the deforma- tion fields using the optical method of DIC.
Abstract: Notched semi-circular bend (NSCB) specimen has been successfully used in fracture tests of brittle materials. As a suggested method for measuring the dynamic fracture toughness of rocks by the International Society for Rock Mechanics (ISRM), this method only measures the fracture initiationtoughnessofthesamplewithgivenexternalloadand geometrical parameters. Using the digital image correlation (DIC) method combined with ultra-high speed photography, the objective of this paper is to measure more fracture param- eters of the NSCB specimen loaded by a split Hopkinson pressure bar (SHPB) system. The displacement and strain fields during the fracture propagation process were deter- mined using DIC method. The location of the crack tip, the fracture initiation toughness and the fracture propagation toughness were subsequently calculated using the deforma- tion fields. Compared with the traditional NSCB tests, the optical method of DIC provides much more information on the fracture propagation process.
133 citations
TL;DR: In this article, the authors used 3D-DIC measurements of drift, diagonal deformations, and interface slip between reinforced concrete tie columns and the masonry infill to produce detailed crack maps.
Abstract: The understanding of the load-resistance mechanisms and failure modes of large-scale concrete and masonry structures relies on accurate measurements of surface motions and deformations, and faithful crack maps. Measurements are typically taken using surface-mounted point-wise sensors (PWSs), and crack maps are hand-drawn based on visual inspection. It is impractical to obtain detailed displacement and deformation maps that describe the complex response of large structures based on PWS measurements. In addition, manual crack drawing is difficult, time-consuming, and prone to human errors, which makes it challenging to consistently produce faithful crack maps. This paper reports on a pilot study to test the use of three-dimensional digital image correlation (3D-DIC) as a non-contacting method to measure surface deformation fields on full-scale masonry walls, and produce detailed crack maps. Three confined masonry walls were tested under horizontal in-plane reverse-cycle loads. The specimens were designed to attain different levels of strength and deformability through different load-resistance mechanisms. Representative 3D-DIC measurements of drift, diagonal deformations, and interface slip between the reinforced concrete tie columns and the masonry infill were evaluated vis-a-vis benchmark PWS measurements, showing a comparable accuracy. Strain maps based on 3D-DIC measurements were enlisted to visualize the development of the fundamental strut-and-tie resisting mechanism in confined masonry walls subjected to horizontal in-plane loads, and illustrate practical structural analysis and design implications. More detailed crack maps compared with traditional hand-drawn maps were obtained based on 3D-DIC maximum principal strain contours.
133 citations
TL;DR: In this article, a simple linear least squares algorithm is proposed to estimate the distortion coefficient from the distorted displacement results of rigid body, in-plane translation tests, which can be used to correct the distortion fields to obtain unbiased displacement and strain fields.
132 citations