scholarly journals New Four Points Initialization for Digital Image Correlation in Metal-Sheet Strain Measurements

2019 ◽  
Vol 9 (8) ◽  
pp. 1691 ◽  
Author(s):  
Alejandro-Israel Barranco-Gutiérrez ◽  
José-Alfredo Padilla-Medina ◽  
Francisco J. Perez-Pinal ◽  
Juan Prado-Olivares ◽  
Saúl Martínez-Díaz ◽  
...  
Keyword(s):  
Image Registration ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Surface Deformation ◽  
Initial Conditions ◽  
Low Cost ◽  
Digital Camera ◽  
Image Correlation ◽  
Camera System ◽  
Metal Sheets

Nowadays, the deformation measurement in metal sheets is important for industries such as the automotive and aerospace industries during its mechanical stamping processes. In this sense, Digital Image Correlation (DIC) has become the most relevant measurement technique in the field of experimental mechanics. This is mainly due to its versatility and low-cost compared with other techniques. However, traditionally, DIC global image registration implemented in software, such as MATLAB 2018, did not find the complete perspective transformation needed successfully and with high precision, because those algorithms use an image registration of the type “afine” or “similarity”, based on a 2D information. Therefore, in this paper, a DIC initialization method is presented to estimate the surface deformation of metal sheets used in the bodywork automotive industry. The method starts with the 3D points reconstruction from a stereoscopic digital camera system. Due to the problem complexity, it is first proposed that the user indicates four points, belonging to reference marks of a “Circle grid”. Following this, an automatic search is performed among the nearby marks, as far as one desires to reconstruct it. After this, the local DIC is used to verify that those are the correct marks. The results show reliability by reason of the high coincidence of marks in experimental cases. We also consider that the quality of mark stamping, lighting, and the initial conditions also contribute to trustworthy effects.

scholarly journals Digital Image Correlation for Cement-based Materials and Structural Concrete Testing

2020 ◽  
Vol 22 (1) ◽  
pp. 6-12 ◽  
Author(s):  
Asdam Tambusay ◽  
Benny Suryanto ◽  
Priyo Suprobo
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Low Cost ◽  
Digital Camera ◽  
Cement Composite ◽  
Reinforced Concrete Beam ◽  
Image Correlation ◽  
Image Recording ◽  
Composite Testing

This paper presents the application of a low-cost digital image correlation (DIC) system for automated crack mapping. The system employed makes use of a conventional digital camera, a remote image recording controller, and an open-source digital image correlation MATLAB software Ncorr. To showcase the potential of the proposed system, two case studies involving general structural and material testing were undertaken. In the first series, the DIC system was used to study the fracture processes in a reinforced concrete beam and to investigate the influence of key input parameters on the spatial quality of strain maps obtained from the DIC analysis. In the second series, the application of the DIC method was expanded to assist in the study of complex multiple micro-crack formations in ductile cement composite testing. It is shown that the strain maps obtained from the DIC technique have a close resemblance to the actual crack patterns

Predicting strains in embedded reinforcement based on surface deformation obtained by digital image correlation technique

2021 ◽  
Author(s):  
Ali Mirzazade ◽  
Cosmin Popescu ◽  
Thomas Blanksvärd ◽  
Björn Täljsten
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Surface Deformation ◽  
Local Strain ◽  
Surface Strain ◽  
Image Correlation ◽  
Correlation Technique ◽  
Proposed Model ◽  
Structural Inspection ◽  
Semi Empirical

<p>This study is carried out to assess the applicability of using a digital image correlation (DIC) system in structural inspection, leading to deploy innovative instruments for strain/stress estimation along embedded rebars. A semi-empirical equation is proposed to predict the strain in embedded rebars as a function of surface strain in RC members. The proposed equation is validated by monitoring the surface strain in ten concrete tensile members, which are instrumented by strain gauges along the internal steel rebar. One advantage with this proposed model is the possibility to predict the local strain along the rebar, unlike previous models that only monitored average strain on the rebar. The results show the feasibility of strain prediction in embedded reinforcement using surface strain obtained by DIC.</p>

scholarly journals A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation

2016 ◽  
Vol 23 (3) ◽  
pp. 461-480 ◽  
Author(s):  
Sze-Wei Khoo ◽  
Saravanan Karuppanan ◽  
Ching-Seong Tan
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Measurement ◽  
Surface Deformation ◽  
Optical Measurement ◽  
Image Correlation ◽  
Two Dimensional ◽  
Full Field ◽  
Computation Efficiency ◽  
Dimensional Measurements

Abstract Among the full-field optical measurement methods, the Digital Image Correlation (DIC) is one of the techniques which has been given particular attention. Technically, the DIC technique refers to a non-contact strain measurement method that mathematically compares the grey intensity changes of the images captured at two different states: before and after deformation. The measurement can be performed by numerically calculating the displacement of speckles which are deposited on the top of object’s surface. In this paper, the Two-Dimensional Digital Image Correlation (2D-DIC) is presented and its fundamental concepts are discussed. Next, the development of the 2D-DIC algorithms in the past 33 years is reviewed systematically. The improvement of 2DDIC algorithms is presented with respect to two distinct aspects: their computation efficiency and measurement accuracy. Furthermore, analysis of the 2D-DIC accuracy is included, followed by a review of the DIC applications for two-dimensional measurements.

Optical Strain Monitoring Techniques

2012 ◽  
Author(s):  
Aditya Narayanan ◽  
Andy Morris ◽  
Catrin M. Davies ◽  
John P. Dear
Keyword(s):  
Digital Image Correlation ◽  
Creep Strain ◽  
Digital Image ◽  
Power Plants ◽  
Image Correlation ◽  
Camera System ◽  
Optical Strain ◽  
Point To Point ◽  
The Uk ◽  
And Control

The Auto-Reference Creep Management and Control (ARCMAC) system is being developed as a technique to evaluate the remaining life of power plant components. The system consists of a pair of Inconel plates with a configuration of silicon nitride (SiN) spheres on them, and a camera system used to take images of the gauge during the component’s deformation. The purpose of the system is to measure the creep strain accumulated by a component at regular intervals, tracking the relative motion of the spheres in order to measure a point-to-point value of strain. The system is currently used to capture images of gauges already installed on power plants in the UK as part of scheduled maintenance during plant outages. It is also possible to use the ARCMAC system to capture speckle paint pattern data used in digital image correlation (DIC) in order to visualise the strain field across the heat affected zones (HAZ) in welds and around other strain concentration features. A newer version of the system: the Digital Single Lens Reflex (DSLR) ARCMAC is being developed specifically to capture this kind of data in order to complement the point-to-point strain measurements obtained. This article presents results of experiments performed at room temperature with the purpose of establishing the basic accuracy of the conventional ARCMAC and the DSLR ARCMAC in order to compare their performance. It also intends to evaluate the performance of the latter when used for digital image correlation. The results showcase the accuracy of the technique at high strains using the DSLR camera, showing its usefulness as a tool to measure creep strain.

Digital Image Correlation as a Tool for Monitoring Crack Networks on the Surface of MgO-Based Refractory Castables

2014 ◽  
Vol 92 ◽  
pp. 242-247
Author(s):  
Rafael G.M. Saracura ◽  
Rodrigo B. Canto ◽  
Victor Carlos Pandolfelli ◽  
Nicolas Schmitt ◽  
François Hild
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Displacement Field ◽  
Digital Camera ◽  
Experimental Results ◽  
Image Correlation ◽  
Post Processing ◽  
Climatic Chamber ◽  
Refractory Castables

This paper deals with the characterization of crack networks on the surface of refractory castable slabs, which are induced by stresses arising during the curing and drying (CD) stages. Images of the surface of castable samples placed in a house-made climatic chamber were recorded during the CD stages with a digital camera and processed by Digital Image Correlation (DIC) tomeasure the displacement field. Post-processing of DIC results were performed to estimate the length, orientation and opening of cracks in networks. The methodology is detailed and first analyses of experimental results are shown.

The Wavelike Plastic Deformation of Single Crystal Copper

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Russell J. McDonald ◽  
Christos Efstathiou ◽  
Peter Kurath
Keyword(s):  
Plastic Deformation ◽  
Digital Image Correlation ◽  
Strain Rate ◽  
Single Crystal ◽  
Digital Image ◽  
Surface Deformation ◽  
Image Correlation ◽  
Nominal Strain Rate ◽  
Single Crystal Copper ◽  
Nominal Strain

The purpose of this work is to explore nonuniform plastic flow at small length- and time-scales. Pure single crystal copper tensile specimens were pulled along the [6¯ 5 6] crystal axis at three nominal strain-rates: 0.01%/s, 0.04%/s, and 0.10%/s. Simultaneously, the surface deformation was monitored with in situ digital image correlation over a length-scale of ∼100 μm and a time-scale of 0.07–0.2 s. Sequential digital image correlation strain-rate fields show compelling evidence of a wavelike plastic deformation that is proportional to the nominal strain-rate and decelerates with increasing strain hardening. While a mechanism responsible for the waves is not identified, a methodology correlating observations of multiple researchers is forwarded.

scholarly journals Evaluation of a low-cost approach to 2-D digital image correlation vs. a commercial stereo-DIC system in Brazilian testing of soil specimens

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
M. Arza-García ◽  
C. Núñez-Temes ◽  
J. A. Lorenzana ◽  
J. Ortiz-Sanz ◽  
A. Castro ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Accuracy Assessment ◽  
Low Cost ◽  
Field Measurements ◽  
Image Correlation ◽  
Strain Gauges ◽  
Source Image ◽  
Full Field ◽  
Cost Approach

AbstractDue to their cost, high-end commercial 3D-DIC (digital image correlation) systems are still inaccessible for many laboratories or small factories interested in lab testing materials. These professional systems can provide reliable and rapid full-field measurements that are essential in some laboratory tests with high-strain rate events or high dynamic loading. However, in many stress-controlled experiments, such as the Brazilian tensile strength (BTS) test of compacted soils, samples are usually large and fail within a timeframe of several minutes. In those cases, alternative low-cost methods could be successfully used instead of commercial systems. This paper proposes a methodology to apply 2D-DIC techniques using consumer-grade cameras and the open-source image processing software DICe (Sandia National Lab) for monitoring the standardized BTS test. Unlike most previous studies that theoretically estimate systematic errors or use local measures from strain gauges for accuracy assessment, we propose a contrast methodology with independent full-field measures. The displacement fields obtained with the low-cost system are benchmarked with the professional stereo-DIC system Aramis-3D (GOM GmbH) in four BTS experiments using compacted soil specimens. Both approaches proved to be valid tools for obtaining full-field measurements and showing the sequence of crack initiation, propagation and termination in the BTS, constituting reliable alternatives to traditional strain gauges. Mean deviations obtained between the low-cost 2D-DIC approach and Aramis-3D in measuring in-plane components were 0.08 mm in the perpendicular direction of loading (ΔX) and 0.06 mm in the loading direction (ΔY). The proposed low-cost approach implies considerable savings compared to commercial systems.

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