Evaluation of true stress-strain diagrams for welded joints by application of Digital Image Correlation

2021 ◽  
pp. 105609
Author(s):  
N. Milosevic ◽  
B. Younise ◽  
A. Sedmak ◽  
M. Travica ◽  
A. Mitrovic
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Welded Joints ◽  
True Stress ◽  
Image Correlation ◽  
Stress Strain

scholarly journals Investigation on True Stress-Strain Curves of Flat and Corner Regions of Cold-Formed Section Using 3D Digital Image Correlation Method

2019 ◽  
Vol 2019 ◽  
pp. 1-18
Author(s):  
Bo Xu ◽  
Junwu Xia ◽  
Renwei Ma ◽  
Jian Wang ◽  
Xiaomiao Chen ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Strain Hardening ◽  
Ultimate Strength ◽  
Digital Image ◽  
True Stress ◽  
Image Correlation ◽  
Stress Strain ◽  
Corner Region ◽  
Flat Region ◽  
3D Digital Image Correlation

The true stress-strain curve is the critical method to describe the practical material mechanical performance and the essential precondition to develop the advanced numerical simulation. Experimental, analytical, and numerical procedures were performed in present research to investigate the true stress-strain curves of flat and corner regions of the cold-formed channel section. The coupon tests with the 3D digital image correlation system were conducted on flat and corner specimens to directly obtain the true stress-strain curves. The experimental results indicate that the tensile secondary-hardening phenomenon at the plastic strain stage was observed in the true stress-strain curves of flat coupons, and initial strain hardening behavior was produced in that of corner coupons. Flat region exhibits a significant improvement of true ultimate strength compared to the engineering value. The stress status of the corner region is developed to ultimate strength at the early strain phase and exhibits a slight increase compared with the nominal values at the plastic phase. Cold-rolling action limits the ductility performance of the corner region, which highly restrains the tensile strain hardening at the plastic condition. Thus, the true yielding strength of the corner region is obviously higher, but the true ultimate strength is significantly lower than that of the flat region. Together with the optical measuring results, a trilinear model with two-stage strain hardening and a simplified trilinear models were established for describing the true stress-strain curves of flat and corner regions, respectively. The load-displacement curves from numerical simulations fit very well with those of coupon tests, which validate the reliability of the optic measurement and the dependability of the simplified constitutive models.

Determination of constitutive relation from miniature tensile test with digital image correlation

2020 ◽  
Vol 55 (3-4) ◽  
pp. 99-108 ◽  
Author(s):  
Yunlu Zhang ◽  
Sreekar Karnati ◽  
Tan Pan ◽  
Frank Liou
Keyword(s):  
Digital Image Correlation ◽  
Tensile Test ◽  
Constitutive Relation ◽  
Digital Image ◽  
Strain Curve ◽  
True Stress ◽  
Image Correlation ◽  
Stress Strain Curve ◽  
Stress Strain

The determination of constitutive relation from the miniature tensile test is of high interest in multiple areas. Here, a convenient experimental method is proposed to determine the true stress–strain curve from the miniature tensile test. The instantaneous cross-sectional area is estimated by only one camera in aid of digital image correlation technique. This method was applied on commercial pure titanium and aluminum 6061 alloys, and the results indicate that the extracted true stress–strain curves are not scale-dependent. The derived mechanical properties from miniature specimens match well with the results of standard specimens. The correctness of the true stress–strain curve was evaluated by the finite element analysis method. The results suggest that the derived true stress–strain curve is capable to represent the constitutive behavior of the tested materials.

Comparison of the Tensile Performance of Polymer PC and PC/ABS

2007 ◽  
Vol 353-358 ◽  
pp. 563-566
Author(s):  
Qin Zhi Fang ◽  
Tie Jun Wang ◽  
Hui Min Li
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Acrylonitrile Butadiene Styrene ◽  
True Stress ◽  
Image Correlation ◽  
Stage Model ◽  
Displacement Fields ◽  
Stress Strain ◽  
Tensile Performance ◽  
Butadiene Styrene

Large deformation performances of polycarbonate (PC) and PC/ABS (Acrylonitrile Butadiene Styrene) have been investigated experimentally in this paper. The displacement fields of these polymers are measured with a system based on digital image correlation (DIC) method. The variations of strains during tension are measured and the true stress-strain curves are presented. For these materials, it is observed that the contraction in thickness is larger than that in width during tension. No obvious stress softening is observed in the true stress-strain curves. The true stress-strain curves can be fitted well with three-stage model.

Evaluation of local constitutive properties of Al2024 friction stir-welded joints using digital image correlation method

2020 ◽  
pp. 030932472098120
Author(s):  
A. Shahmirzaloo ◽  
M. Farahani ◽  
M. Farhang
Keyword(s):  
Mechanical Properties ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Welded Joints ◽  
Local Stress ◽  
Image Correlation ◽  
Welding Parameters ◽  
Stress Strain ◽  
Friction Stir ◽  
Dic Technique

The intense applied thermal gradients during the welding process leads to the variation in the properties of the weld zone and its surrounding areas. In this regard, determining the local mechanical properties and evolved microstructures of the weld and its surrounding zones are essential in the evaluation of welded structures. In this study, the local mechanical properties of Al2024 friction-stir-welded joints were precisely examined. Digital image correlation (DIC) technique using uniform stress (USM) and virtual field methods (VFM) were utilized to evaluate the local mechanical properties. The local stress-strain curves were plotted for different weld regions using local strain from the DIC technique. It was observed that the advancing side of the thermo-mechanically affected zone (TMAZ) had the lowest values of Young’s modulus and yield strength (YS), approximately 9% and 31% of the base metal, respectively. Effects of welding parameters, such as tool rotational and traverse speeds, were also taken into account. The plotted local stress-strain curve for the fractured region of welded specimens at lower rotational speed illustrated a higher strength and elongation. Furthermore, lower rotational and also higher traverse speeds resulted in the reduction of the grain size.

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.

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