Full-Field Strain Behavior of Friction Stir-Welded Titanium Alloy by Digital Image Correlation

2014 ◽  
Vol 692 ◽  
pp. 490-496 ◽  
Author(s):  
Mamidala Ramulu ◽  
Trent Greenwell ◽  
Paul Labossiere
Keyword(s):  
Titanium Alloy ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Thin Sheet ◽  
Measurement Techniques ◽  
Image Correlation ◽  
Stress Strain ◽  
Full Field ◽  
Friction Stir ◽  
Strain Behavior

Experimental investigation is conducted to examine, evaluate, and characterize the fundamental elastic-plastic stress/strain response of friction stir-welded butt joints in thin-sheet, fine grain Ti-6Al-4V titanium alloy under normal tensile loading using traditional global stress-strain tensile testing and the full-field displacement measurement techniques of Digital Image Correlation (DIC). It was found that overall strength of friction stir-welded Ti-6Al-4V is comparable to the accepted values for mill-annealed Ti-6Al-4Valloy. Overall strain performance of friction stir-welded Ti-6Al-4V is roughly half that of the accepted values for pure mill-annealed Ti-6Al-4V. In addition, friction stir-welded Ti-6Al-4V demonstrates a consistent pattern of strain localization between the onset of yielding and ultimate failure.

Local Elasto-Plastic Identification of the Behaviour of Friction Stir Welds with the Virtual Fields Method

2011 ◽  
Vol 70 ◽  
pp. 135-140 ◽  
Author(s):  
G. Le Louëdec ◽  
M.A. Sutton ◽  
Fabrice Pierron
Keyword(s):  
Mechanical Properties ◽  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Weld Zone ◽  
Spatial Variations ◽  
Image Correlation ◽  
Virtual Fields Method ◽  
Full Field ◽  
Friction Stir

Welding is one of the most popular joining technologies in industry. Depending on the materials to be joined, the geometry of the parts and the number of parts to be joined, there is a wide variety of methods that can be used. These joining techniques share a common feature: the material in the weld zone experiences different thermo-mechanical history, resulting in significant variations in material microstructure and spatial heterogeneity in mechanical properties. To optimize the joining process, or to refine the design of welded structures, it is necessary to identify the local mechanical properties within the different regions of the weld. The development of full-field kinematic measurements (digital image correlation, speckle interferometry, etc.) helps to shed a new light on this problem. The large amount of experimental information attained with these methods makes it possible to visualize the spatial distribution of strain on the specimen surface. Full-field kinematic measurements provide more information regarding the spatial variations in material behaviour. As a consequence, it is now possible to quantify the spatial variations in mechanical properties within the weld region through a properly constructed inverse analysis procedure. High speed tensile tests have been performed on FSW aluminium welds. The test was performed on an MTS machine at a cross-head speed of up to 76 mm/s. Displacement fields were measured across the specimen by coupling digital image correlation with a high-speed camera (Phantom V7.1) taking 1000 frames per second. Then, through the use of the virtual fields method it is possible to retrieve the mechanical parameters of the different areas of the weld from the strain field and the loading. The elastic parameters (Young’s modulus and Poisson’s ratio) are supposed to be constant through the weld. Their identification was carried out using the virtual fields method in elasticity using the data of the early stage of the experiment. Assuming that the mechanical properties (elastic and plastic) of the weld are constant through the thickness, the plastic parameters were identified on small sections through the specimen, using a simple linear hardening model. This method leads to a discrete identification of the evolution of the mechanical properties through the weld. It allows the understanding of the slight variations of yield stress and hardening due to the complexity of the welding process.

Assessment of Stress-Strain Behavior of Corroded Steel Reinforcement Using Digital Image Correlation (DIC)

2018 ◽  
Vol 46 (5) ◽  
pp. 20160487 ◽  
Author(s):  
Ranjitha Rajagopal ◽  
Sameer Sharma ◽  
Radhakrishna G. Pillai ◽  
Sankara J. Subramanian
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Steel Reinforcement ◽  
Image Correlation ◽  
Stress Strain ◽  
Strain Behavior ◽  
Assessment Of Stress

Error Estimations in Digital Image Correlation Technique

2007 ◽  
Vol 7-8 ◽  
pp. 265-270 ◽  
Author(s):  
Thorsten Siebert ◽  
Thomas Becker ◽  
Karsten Spiltthof ◽  
Isabell Neumann ◽  
Rene Krupka
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Image Correlation ◽  
Field Analysis ◽  
Correlation Technique ◽  
Full Field ◽  
Wide Range ◽  
The Impact

The reliability for each measurement technique depends on the knowledge of it’s uncertainty and the sources of errors of the results. Among the different techniques for optical measurement techniques for full field analysis of displacements and strains, digital image correlation (DIC) has been proven to be very flexible, robust and easy to use, covering a wide range of different applications. Nevertheless the measurement results are influenced by statistical and systematical errors. We discuss a 3D digital image correlation system which provides online error information and the propagation of errors through the calculation chain to the resulting contours, displacement and strains. Performance tests for studying the impact of calibration errors on the resulting data are shown for static and dynamic applications.

scholarly journals Measurement of Interlaminar Tensile Strength and Elastic Properties of Composites Using Open-Hole Compression Testing and Digital Image Correlation

2019 ◽  
Vol 9 (13) ◽  
pp. 2647 ◽  
Author(s):  
Guillaume Seon ◽  
Andrew Makeev ◽  
Joseph D. Schaefer ◽  
Brian Justusson
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Standard Test ◽  
Image Correlation ◽  
Stress Strain ◽  
Aircraft Structures ◽  
Full Field ◽  
Manufacturing Defects ◽  
Open Hole ◽  
Properties Of Composites

Advanced polymeric composites are increasingly used in high-performance aircraft structures to reduce weight and improve efficiency. However, a major challenge delaying the implementation of the advanced composites is the lack of accurate methods for material characterization. Accurate measurement of three-dimensional mechanical properties of composites, stress–strain response, strength, fatigue, and toughness properties, is essential in the development of validated analysis techniques accelerating design and certification of composite structures. In particular, accurate measurement of the through-thickness constitutive properties and interlaminar tensile (ILT) strength is needed to capture delamination failure, which is one of the primary failure modes in composite aircraft structures. A major technical challenge to accurate measurement of ILT properties is their strong sensitivity to manufacturing defects that often leads to unacceptable scatter in standard test results. Unacceptable failure mode in standard test methods is another common obstacle to accurate ILT strength measurement. Characterization methods based on non-contact full-field measurement of deformation have emerged as attractive alternative techniques allowing more flexibility in test configuration to address some of the limitations inherent to strain gauge-based standard testing. In this work, a method based on full-field digital image correlation (DIC) measurement of surface deformation in unidirectional open-hole compression (OHC) specimens is proposed and investigated as a viable alternative to assessing ILT stress–strain, strength, and fatigue properties. Inverse identification using a finite element model updating (FEMU) method is used for simultaneous measurement of through-thickness elastic constants with recovery of the maximum ILT stress at failure for characterization of strength and fatigue S–N curves.

Validation of Digital Image Correlation Techniques for Strain Measurement in Biomechanical Test Models

2013 ◽  
Author(s):  
Renee D. Rogge ◽  
Scott R. Small ◽  
Derek B. Archer ◽  
Michael E. Berend ◽  
Merrill A. Ritter
Keyword(s):  
Aluminum Alloy ◽  
Digital Image Correlation ◽  
Polyurethane Foam ◽  
Digital Image ◽  
Measurement Techniques ◽  
Image Correlation ◽  
Principal Strain ◽  
Strain Gages ◽  
Full Field ◽  
Strain Measurements

Many previous biomechanical studies of bone and bone substitutes have estimated strains in these materials using strain gages. The purpose of this study was to compare digital image correlation (DIC) strain measurements to those obtained from strain gages in order to assess the applicability of DIC technology to common biomechanical testing scenarios. Compression and bending tests were conducted on aluminum alloy, polyurethane foam, and laminated polyurethane foam specimens. Results showed no significant differences in the principal strain values (or the variances) between strain gage and DIC measurements on the aluminum alloy and laminated polyurethane foam specimens. There were significance differences between the principal strain measurements of the non-laminated polyurethane foam specimens, but the deviation from the theoretical results was similar for both measurement techniques. In summary, DIC techniques provide similar results to those obtained from strain gages and also provide full field strain results.

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.

scholarly journals Experimental Characterization of the FRCM-Concrete Interface Bond Behavior Assisted by Digital Image Correlation

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1154
Author(s):  
Dario De Domenico ◽  
Antonino Quattrocchi ◽  
Damiano Alizzio ◽  
Roberto Montanini ◽  
Santi Urso ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Mechanical Tests ◽  
Image Correlation ◽  
Front Face ◽  
Full Field ◽  
Bond Behavior ◽  
Externally Bonded ◽  
Strengthening Technique ◽  
Concrete Interface

Digital Image Correlation (DIC) provides measurements without disturbing the specimen, which is a major advantage over contact methods. Additionally, DIC techniques provide full-field maps of response quantities like strains and displacements, unlike traditional methods that are limited to a local investigation. In this work, an experimental application of DIC is presented to investigate a problem of relevant interest in the civil engineering field, namely the interface behavior between externally bonded fabric reinforced cementitious mortar (FRCM) sheets and concrete substrate. This represents a widespread strengthening technique of existing reinforced concrete structures, but its effectiveness is strongly related to the bond behavior between composite fabric and underlying concrete. To investigate this phenomenon, a set of notched concrete beams are realized, reinforced with FRCM sheets on the bottom face, subsequently cured in different environmental conditions (humidity and temperature) and finally tested up to failure under three-point bending. Mechanical tests are carried out vis-à-vis DIC measurements using two distinct cameras simultaneously, one focused on the concrete front face and another focused on the FRCM-concrete interface. This experimental setup makes it possible to interpret the mechanical behavior and failure mode of the specimens not only from a traditional macroscopic viewpoint but also under a local perspective concerning the evolution of the strain distribution at the FRCM-concrete interface obtained by DIC in the pre- and postcracking phase.

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