scholarly journals Full-Field Microscale Strain Measurements of a Nitinol Medical Device Using Digital Image Correlation

2020 ◽  
Author(s):  
Kenneth I. Aycock ◽  
Jason D. Weaver ◽  
Harshad M Paranjape ◽  
Karthikeyan Senthilnathan ◽  
Craig Bonsignore ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Computational Models ◽  
Optical Microscope ◽  
Image Correlation ◽  
Full Field ◽  
Physiological Loading ◽  
Out Of Plane ◽  
Computational Modeling And Simulation ◽  
Cantilever Bending

Computational modeling and simulation are commonly used during the development of cardiovascular implants to predict peak strains and strain amplitudes and to estimate the associated durability and fatigue life of these devices. However, simulation validation has historically relied on comparison with surrogate quantities like force and displacement due to barriers to direct strain measurement–most notably, the small spatial scale of these devices. We demonstrate the use of microscale two-dimensional digital image correlation (2D-DIC) to directly characterize full-field surface strains on a nitinol device coupon under emulated physiological loading. Experiments are performed using a digital optical microscope and a custom, temperature-controlled load frame. Following applicable recommendations from the International DIC Society, hardware and environmental heating studies, noise floor analyses, and in- and out-of-plane rigid body translation studies are first performed to characterize the microscale DIC setup. Uniaxial tension experiments are also performed using a polymeric test specimen up to nominal stains of 5%. Sub-millimeter fields of view and sub-micron displacement accuracies (9 nm mean error) are achieved, and systematic (mean) and random (standard deviation) errors in strain are each estimated to be approximately 1,000 μϵ. The system is then demonstrated by acquiring measurements at the root of a 300 μm-wide nitinol device strut undergoing fixed-free cantilever bending motion. Lüders-like transformation bands are observed originating from the tensile side of the strut that spread toward the neutral axis at an angle of approximately 55°. Optical microscale 2D-DIC setups like that demonstrated herein will be useful in future studies for characterizing cardiovascular implant micromechanics, validating computational models, and guiding the development of next-generation material models for simulating superelastic nitinol.

Error Assessment of Blade Deformation Measurements on a Multi-Megawatt Wind Turbine Based on Digital Image Correlation

2015 ◽  
Author(s):  
Jan Winstroth ◽  
Joerg R. Seume
Keyword(s):  
Digital Image Correlation ◽  
Wind Turbine ◽  
Error Estimation ◽  
Digital Image ◽  
Rotor Blades ◽  
Image Correlation ◽  
Optical Measurements ◽  
Full Field ◽  
Out Of Plane ◽  
Plane Bending

Optical full-field measurement methods such as Digital Image Correlation (DIC) provide a new opportunity for measuring deformation and vibration in wind turbine rotor blades during operation, in high spatial and temporal resolution. Recent field tests on a multi-megawatt wind turbine have demonstrated the vast potential for full scale testing, however little is known about the overall accuracy of DIC measurements on wind turbines. The present work proposes using a virtual 3D wind turbine model for estimating the error associated with the optical measurements. The entire setup is simulated a priori and accurate error estimation becomes possible. The error estimation for a 3.2 MW wind turbine suggests that relative out-of-plane bending of the rotor blades can be measured with an accuracy of ±9.1 mm, relative in-plane bending of the rotor blades can be measured with an accuracy of ±10.2 mm, and relative blade torsion can be measured with an accuracy of ±0.07 deg. This corresponds to a relative error of 0.46% for out-of-plane bending, 1.11% for in-plane bending and 5.46% for blade torsion.

scholarly journals Stereo Digital Image Correlation in MATLAB

2021 ◽  
Vol 11 (11) ◽  
pp. 4904
Author(s):  
Devan Atkinson ◽  
Thorsten Hermann Becker
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
State Of The Art ◽  
Deep Understanding ◽  
Image Correlation ◽  
Educational Resource ◽  
Full Field ◽  
Current State ◽  
Out Of Plane ◽  
Novel Applications

Digital Image Correlation (DIC) has found widespread use in measuring full-field displacements and deformations experienced by a body from images captured of it. Stereo-DIC has received significantly more attention than two-dimensional (2D) DIC since it can account for out-of-plane displacements. Although many aspects of Stereo-DIC that are shared in common with 2D DIC are well documented, there is a lack of resources that cover the theory of Stereo-DIC. Furthermore, publications which do detail aspects of the theory do not detail its implementation in practice. This literature gap makes it difficult for newcomers to the field of DIC to gain a deep understanding of the Stereo-DIC process, although this knowledge is necessary to contribute to the development of the field by either furthering its capabilities or adapting it for novel applications. This gap in literature acts as a barrier thereby limiting the development rate of Stereo-DIC. This paper attempts to address this by presenting the theory of a subset-based Stereo-DIC framework that is predominantly consistent with the current state-of-the-art. The framework is implemented in practice as a 202 line MATLAB code. Validation of the framework shows that it performs on par with well-established Stereo-DIC algorithms, indicating it is sufficiently reliable for practical use. Although the framework is designed to serve as an educational resource, its modularity and validation make it attractive as a means to further the capabilities of DIC.

Experimental Study on Flow-Induced Full-Field Vibration of a Flexible Splitter Plate Behind a Cylinder Using Stereo-Digital Image Correlation

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Ruili Xie ◽  
Liping Yu ◽  
Weidong Zhu ◽  
Bing Pan
Keyword(s):  
Wind Tunnel ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Plane Deformation ◽  
Splitter Plate ◽  
Image Correlation ◽  
Full Field ◽  
Out Of Plane ◽  
Stereo Digital Image Correlation ◽  
Deformation Measurements

Abstract The flow-induced vibration of a flexible splitter plate behind a circular cylinder is investigated experimentally in this study. Unlike previous studies that mainly devoted to flow dynamics, the full-field three-dimensional (3D) dynamic deformation of a splitter plate behind a cylinder in the wind tunnel is measured with an easy-to-implement, compact but practical single-camera high-speed (SCHS) stereo-digital image correlation (DIC) system. The system parameters of the wind tunnel, the configuration of the SCHS-DIC system, and the measurement principles are introduced first. Then, the effectiveness, accuracy, and stability of the SCHS stereo-DIC system are verified by the deformation measurements of the high-stiffness fixed cylinder. Finally, the full-field dynamic 3D deformation measurements of different splitter plates are carried out under different wind speeds. Results of the polyvinyl chloride (PVC) splitter plate show that the out-of-plane deformation is much larger than in-plane deformation. The maximum deformation occurs at the tip region of the plate, the position of which can move non-periodically along the free-end edge. The full-field deformation of the plate presents the characteristics of complex vortex distribution with high and low fluctuations, and exhibits an asymmetric and non-periodic oscillation in the out-of-plane direction. The comparison results reveal how the wind load and material type of the plate affect the oscillation characteristics.

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.

The Stress Intensity Factor of Opening Mode Determined by Digital Image Correlation

2011 ◽  
Vol 83 ◽  
pp. 54-59 ◽  
Author(s):  
Rui Zhang ◽  
Ling Feng He ◽  
Chang Rong Li
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Digital Image Correlation ◽  
Intensity Factor ◽  
Digital Image ◽  
Correlation Method ◽  
Compact Tension ◽  
Image Correlation ◽  
Full Field ◽  
Opening Mode

Applications of the digital image correlation method (DIC) for the determination of the opening mode stress intensity factor (SIF) is investigated using an edge cracked aluminum plate in this paper. Standard compact tension test specimen was tested under tensile loading and the full-field displacement fields of the test sample were recorded using DIC. The SIF associated with unavoidable rigid-body displacement translation were calculated simultaneously from the experimental data by fitting the theoretical displacement field using the method of least-squares. Selection of displacement and convergence values is discussed. For validation, the SIF thus determined is compared with theoretical results, confirming the effectiveness and accuracy of the proposed technique. Therefore it reveals that the DIC is a practical and effective tool for full-field deformation and SIF measurement.

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