scholarly journals Influence of Sheet Conditions on In-Plane Strain Evolution via Ex-Situ Tensile Deformation of Ti-3Al-2.5V at Room Temperature

2021 ◽  
Vol 10 (1) ◽  
pp. 15-26
Author(s):  
J.S Kwame ◽  
E. Yakushina ◽  
P. Blackwell
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Phase Field ◽  
Image Correlation ◽  
Ex Situ ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Deformation Bands ◽  
Strain Evolution ◽  
Β Phase

Localised plastic deformation evolution was examined in a near alpha Ti-3Al-2.5V alloy with indent defect and defect free surfaces using digital image correlation, an interrupted uniaxial tensile test and scanning electron microscopy. The main aim was to understand the role of the localised strain evolution at micro scale and the underlying deformation mechanisms that influence the global mechanical behaviour of the material. The microstructures captured at different stages of deformation were processed using a digital image correlation system, whose outputs were analysed through Matlab, to ascertain the localised strain evolution observed in each surface condition. This work found that the strains observed at the deformation bands along the indent defect edge, were significantly higher than those observed in the deformed β phase field. The deformation bands concentrating at the tip of the indent defect acted as a fertile site for early crack nucleation and propagation with a reduced localised fracture strain. For a defect free surface, the absence of defect zones acting as a high stress concentration site meant that strain aggregation was minimised and the α phase field was able to sufficiently accommodate the β phase deformation resulting in higher fracture strains.

scholarly journals Multi-Scale Digital Image Correlation Analysis of In Situ Deformation of Open-Cell UHMWPE Foam

2020 ◽  
Author(s):  
Eugene S. Statnik ◽  
Codrutza Dragu ◽  
Cyril Besnard ◽  
Alexander J.G. Lunt ◽  
Alexey I. Salimon ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Performance ◽  
Structural Evolution ◽  
Image Correlation ◽  
Deformation Bands ◽  
Open Cell ◽  
Polyether Ether Ketone ◽  
Structural Levels

Porous ultra-high molecular weight polyethylene (UHMWPE) is a high performance bioinert polymer used in cranio-facial reconstructive surgery in procedures where relatively low mechanical stresses arise. As an alternative to much stiffer and costly polyether-ether-ketone (PEEK) polymer, UHMWPE finds further wide application in hierarchically structured hybrids for advanced implants mimicking cartilage, cortical and trabecular bone tissues within a single component. The mechanical behaviour of open-cell UHMWPE sponges obtained through sacrificial desalination of hot compression-moulded UHMWPE-NaCl powder mixtures shows a complex dependence on the fabrication parameters and microstructural features. In particular, similarly to other porous media it displays significant inhomogeneity of strain that readily localises within deformation bands that govern the overall response. In this article, we report advances in the development of accurate experimental techniques for operando studies of the structure-performance relationship applied to the porous UHMWPE medium with pore sizes of about 250 µm that are most well-suited for live cell proliferation and fast vascularization of implants. Samples of UHMWPE sponges were subjected to in situ compression using a micromechanical testing device within Scanning Electron Microscope (SEM) chamber, allowing the acquisition of high-resolution image sequences for Digital Image Correlation (DIC) analysis. Special masking and image processing algorithms were developed and applied to reveal the evolution of pore size and aspect ratio. Key structural evolution and deformation localisation phenomena were identified at both macro- and micro-structural levels in the elastic and plastic regimes. The motion of pore walls was quantitatively described, and the presence and influence of strain localisation zones were revealed and analysed using DIC technique.

Experimental Study of Fatigue Crack Initiation and Strain Evolution around a Micro-Void by In Situ SEM and Digital Image Correlation

2017 ◽  
Vol 754 ◽  
pp. 75-78 ◽  
Author(s):  
De Qiang Wang ◽  
Ming Liang Zhu ◽  
Fu Zhen Xuan
Keyword(s):  
Fatigue Crack ◽  
Digital Image Correlation ◽  
Crack Initiation ◽  
Digital Image ◽  
Early Stage ◽  
Fatigue Crack Initiation ◽  
Image Correlation ◽  
Dominant Factor ◽  
Strain Evolution

Fatigue crack initiation stage occupies a large proportion of total fatigue life in modern engineering materials and structures which are often designed under lower service loading conditions. In this paper, the fatigue crack initiation behavior from a micro-void in a small-scale specimen was studied in-situ in SEM. Surface morphologies were monitored in-situ and images were taken during interrupted tests at selected number of cycles, and displacement and strain map around the void was calculated based on digital image correlation (DIC) technique. The results indicated that the strain evolution near the micro-void could be divided into stages, before crack initiation. The strain increasing rate was fast in the early stage and slower in the second stage. A critical cyclic strain value for fatigue crack initiation from the micro-void was obtained around 9%, and was believed to be the dominant factor for early stage of fatigue damage.

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.

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.

Identification of the Mechanical Properties of High-Strength Steel Using Digital Image Correlation

2014 ◽  
Vol 980 ◽  
pp. 122-126 ◽  
Author(s):  
Michaela Štamborská ◽  
Miroslav Kvíčala ◽  
Monika Losertová
Keyword(s):  
Mechanical Properties ◽  
Digital Image Correlation ◽  
Digital Image ◽  
High Strength Steel ◽  
Strain Field ◽  
High Strength ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Large Strains ◽  
Identification Procedure

Identification of the mechanical properties of high-strength steel using digital image correlation. In this paper an experimental procedure to identify the plastic behaviour of sheet metals up to large strains using full field measurement is presented. The tests were conducted on notched specimens. This geometry generates a heterogeneous strain field which was measured during the test using a digital image correlation system. The advantage of using a heterogeneous strain field in the identification procedure is that a complex state of stress-strain can be analyzed at the same time and much more information can be obtained in a single test. On the other hand, the stress field cannot be directly computed from the test and a suitable identification procedure must be developed. Here, the virtual fields method (VFM) adapted for large strains and plasticity was used to identify the hardening behaviour and the anisotropy of the material. The values obtained with the VFM were compared with the results from a standard identification made using uniaxial tensile tests.

scholarly journals Tensile Creep of Cement and Concrete Composites: Monitoring by Means of 2D-Digital Image Correlation

2021 ◽  
Vol 11 (18) ◽  
pp. 8334
Author(s):  
Andina Sprince ◽  
Tomass Kozlovskis ◽  
Rihards Gailitis ◽  
Juozas Valivonis ◽  
Kinga Korniejenko ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Compact Tension ◽  
Test Methods ◽  
Image Correlation ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
2D Digital Image Correlation ◽  
Cement And Concrete ◽  
Creep Deformations

Creep and shrinkage of Cement and Concrete Composites (CCC) are significant properties that need to be considered to use these materials in practice. Many previous scientific studies revealed CCC creep characteristics under sustained compression and shrinkage, using traditional test methods from design standards. Because of the complexity of experimental procedures, CCC creep in tension has not been studied as close. Furthermore, there is no unified standard that proposes applicable testing methods or specific testing apparatus. This study examines the suitability of 2D—Digital Image Correlation (DIC) to observe the creep deformations of specimens under tension. Ordinary Portland cement (OPC) mortar with 1% polyvinyl alcohol (PVA) fibres has been investigated in the research. Compact tension (CT) specimens 150 × 150 × 12 mm (with a notch) were used. Creep deformations under sustained uniaxial tension (applied loading corresponding to 60% of the ultimate strength) were measured. DIC images were captured using an entry/mid-level DSLR camera. Results show that DIC is suitable for studying uniaxial tensile creep of cement and concrete composites. Deformation of specimens in tension was similar to that measured using the conventional method (using surface-attached gauges).

scholarly journals Experimental and Numerical Investigations of Thin-Walled Stringer-Stiffened Panels Welded with RFSSW Technology under Uniaxial Compression

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1785 ◽  
Author(s):  
Andrzej Kubit ◽  
Tomasz Trzepiecinski ◽  
Łukasz Święch ◽  
Koen Faes ◽  
Jan Slota
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Testing Machine ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Stiffened Panels ◽  
Friction Stir ◽  
Uniaxial Tensile Testing ◽  
First Case ◽  
Thin Walled

Many aircraft structures are thin walled and stringer-stiffened, and therefore, prone to a loss of stability. This paper deals with accurate and validated stability analysis of the model of aircraft skin under compressive loading. Both experimental and numerical analyzes are conducted. Two different methods of joining panel elements are considered. In the first case, the panel is fabricated using rivets. In the second variant, the refill friction stir spot welding technique is used. Both types of panels are loaded in axial compression in a uniaxial tensile testing machine. The geometrically and physically nonlinear finite element analyzes of the panels were carried out in ABAQUS/Standard. The Digital Image Correlation measurement system ARAMIS has been utilized to monitor the buckling behavior and failure mode in the skin-stringer interface of the stiffened panels. The results of experiments and the digital image correlation system are presented and compared to the numerical simulations.

On the Local Constitutive Behavior of Friction Stir Welded AISI 304 Stainless Steel Joints

2020 ◽  
Vol 979 ◽  
pp. 107-113
Author(s):  
V. Karthik Srinivas ◽  
A.K. Lakshminarayanan
Keyword(s):  
Stainless Steel ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Thermal Imaging ◽  
Image Correlation ◽  
Dynamic Strain ◽  
Uniaxial Tensile ◽  
Infrared Thermal Imaging ◽  
Friction Stir ◽  
Thermal Transients

The uniaxial tensile test is often used to determine the mechanical properties of a material like its yield strength and elastic limit. However, some of the recent advances in imaging Non Destructive Evaluation (NDE) modalities offer experimental tools which, apart from determining the conventional properties, also make it possible to visualise and map the dynamic strain evolution during monotonic loading and correlate it with the micro mechanisms of deformation. Infrared thermal imaging (IRT) and digital image correlation (DIC) are two such advanced NDE methods which are being widely used in experimental mechanics. Infrared thermal imaging maps the thermal gradient including the dynamic thermal transients that may occur during the tensile testing and is based on the detection of infrared radiation. Digital image correlation, a non-contact optical method based on grey value correlation before and after deformation, maps the magnitude of deformation on the surface of the object under load. In this investigation, the global and local properties of a friction stir welded joint of 304 Austenitic Stainless steel through the simultaneous application of thermal imaging and digital image correlation. By characterising the various stages of tensile deformation, this study enabled correlation of the thermal and strain evolutions and to provide deeper insights into the micro-mechanisms of the associated deformation phenomenon.

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