scholarly journals Study on Retrofitted Masonry Elements under Shear Using Digital Image Correlation

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 2122 ◽  
Author(s):  
Benjamín Torres ◽  
Francisco B. Varona ◽  
F. Javier Baeza ◽  
David Bru ◽  
Salvador Ivorra
Keyword(s):  
Digital Image Correlation ◽  
Mechanical Behavior ◽  
Digital Image ◽  
Tensile Tests ◽  
Shear Behavior ◽  
Wind Pressure ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Tension Tests ◽  
Reinforced Masonry

Architectural heritage is usually built with masonry structures, which present problems under lateral in-plane loading conditions, such as wind pressure or earthquakes. In order to improve the shear behavior of masonry, the use of a fabric-reinforced cementitious matrix (FRCM) has become an interesting solution because of its synergy of mechanical properties and compatibility with masonry substrates. For a proper structural evaluation, the mechanical behavior of reinforced masonry and the FRCM itself needs to be characterized. Hence, a numerical model to evaluate the FRCM reinforcement requires some mechanical parameters that may be difficult to obtain. In this sense, the shear behavior of masonry can be evaluated by means of diagonal tension tests on small specimens (71 × 71 cm). In this work, a digital image correlation (DIC) monitoring system was used to control displacements and cracking patterns of masonry specimens under shear stress (induced by diagonal tension with FRCM layers) applied to one or two sides. In addition, the mechanical behavior of FRCM coupons under uniaxial tensile tests was also registered with DIC. The displacement measurements obtained by DIC were validated with the measurements registered with LVDT. Unlike LVDT-based techniques, DIC monitoring allowed us to measure deformations in masonry during the full test, detecting crack initiation even before it was visible to the eye.

Tension and compression moduli characterization of a bimodular ceramic-fiber reinforced SiO2 aerogel composite

2020 ◽  
Vol 62 (10) ◽  
pp. 1003-1009
Author(s):  
Yantao Sun ◽  
Jia Huang ◽  
Duoqi Shi ◽  
Shengliang Zhang ◽  
Zhizhong Fu ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Image Correlation ◽  
Bending Test ◽  
Ceramic Fiber ◽  
Fiber Reinforced ◽  
Compression Tests ◽  
Tension Tests ◽  
Aerogel Composite ◽  
Tension And Compression

Abstract Comprehensive characterization mechanical properties of aerogels and their composites are important for engineering design. In particular, some aerogel composites were reported to have varied tension and compression moduli. But conducting tension tests is difficult for the reason that low strength and brittleness will lead to unexpected failure in the non-test area. A method is presented for measuring both the tension and compression moduli of a ceramic-fiber reinforced SiO2 aerogel composite by bending via digital image correlation. First, the relationship between bending behavior and the tension/compression moduli was introduced for bimodular materials. Then a bending test was conducted to predict tension and the compression moduli of the ceramicfiber- reinforced SiO2 aerogel composite via digital image correlation. In addition, uniaxial tension and compression tests of the aerogel composites were carried out, respectively for measuring tension and compression moduli. The tension and compression moduli measured were numerically similar to results obtained from uniaxial tests with a difference of less than 14 %.

Local Constitutive Behavior of Undermatched Welded Joints in Pipeline Steel Using Digital Image Correlation Technology

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
X. Wu ◽  
J. Shuai ◽  
K. Xu ◽  
Z. Lv
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Welded Joints ◽  
Pipeline Steel ◽  
Image Correlation ◽  
Optical Observations ◽  
Uniaxial Tensile ◽  
Welded Steel ◽  
Steel Joint ◽  
Constitutive Parameters

Abstract Although the identification of local constitutive behaviors is possible based on digital image correlation (DIC), few studies have been reported that characterize the properties of the girth-welded joints of pipeline steel. The DIC technique was used to measure the strain fields of undermatched girth-welded joints of X80 pipeline steel under uniaxial tension in this paper. First, microstructure optical observations and micrometer hardness measurements were used to test the size and hardness of the subregions in the specimens. Second, the local strain data in different regions of the girth-welded joint were obtained via DIC technology, and the stress data were obtained via uniaxial tensile tests. Then, the stress–strain relationships of the weld metal (WM), base metal (BM), and subregions of the heat-affected zone (HAZ) of the girth-welded joints of pipeline steel were obtained. Finally, the constitutive parameters of the Ramberg–Osgood model in the different regions were determined by curve fitting of the strain and stress data. The local yield strength, elastic modulus, and hardening exponent of the welded joints were obtained. The yield stresses of the different subregions of the welded steel joint followed the sequence BM > WM > HAZ, which was consistent with the results of the hardness measurements. The hardening exponents of the different subregions of the welded steel joint followed the sequence HAZ > WM> BM.

scholarly journals Robust Filtering Options for Higher-Order Strain Fields Generated by Digital Image Correlation

2020 ◽  
Vol 1 (4) ◽  
pp. 174-192
Author(s):  
Nedaa Amraish ◽  
Andreas Reisinger ◽  
Dieter H. Pahr
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Tensile Tests ◽  
Image Correlation ◽  
Field Strain ◽  
Strain Fields ◽  
Full Field ◽  
Low Pass ◽  
Discrete Measurement ◽  
Mean Filtering

Digital image correlation (DIC) systems have been used in many engineering fields to obtain surface full-field strain distribution. However, noise affects the accuracy and precision of the measurements due to many factors. The aim of this study was to find out how different filtering options; namely, simple mean filtering, Gaussian mean filtering and Gaussian low-pass filtering (LPF), reduce noise while maintaining the full-field information based on constant, linear and quadratic strain fields. Investigations are done in two steps. First, linear and quadratic strain fields with and without noise are simulated and projected to discrete measurement points which build up strain window sizes consisting of 6×5, 12×11, and 26×17 points. Optimal filter sizes are computed for each filter strategy, strain field type, and strain windows size, with minimal impairment of the signal information. Second, these filter sizes are used to filter full-field strain distributions of steel samples under tensile tests by using an ARAMIS DIC system to show their practical applicability. Results for the first part show that for a typical 12×11 strain window, simple mean filtering achieves an error reduction of 66–69%, Gaussian mean filtering of 72–75%, and Gaussian LPF of 66–69%. If optimized filters are used for DIC measurements on steel samples, the total strain error can be reduced from initial 240−300 μstrain to 100–150 μstrain. In conclusion, the noise-floor of DIC signals is considerable and the preferable filters were a simple mean with s*¯ = 2, a Gaussian mean with σ*¯ = 1.7, and a Gaussian LPF with D0*¯ = 2.5 in the examined cases.

Study on Lüders Deformation in Welded Mild Steel Using Infrared Thermography and Digital Image Correlation

2012 ◽  
Vol 585 ◽  
pp. 82-86 ◽  
Author(s):  
N. Srinivasan ◽  
N. Raghu ◽  
B. Venkatraman
Keyword(s):  
Digital Image Correlation ◽  
Mild Steel ◽  
Infrared Thermography ◽  
Digital Image ◽  
Tensile Testing ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Testing ◽  
Heterogeneous Deformation ◽  
Lüders Band

Studies on characterizing heterogeneous deformations in many materials under different loading conditions using imaging NDE techniques like Infrared thermography (IRT) and Digital image correlation (DIC) began in the last decade and have been reported by many researchers. This work aims in experimental investigation of one such heterogeneous deformation namely Lüders band phenomenon in welded IS 2062 E250-B mild steel during monotonic, uniaxial tensile testing using IRT and DIC. Also attempt has been made to study the generation of pre-yield microstrain in welded material. An understanding of nucleation and propagation of Lüders band in welded specimen is made based on temperature and strain changes.

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