A Computational Workbench for Remote Full Field 3D Displacement and Strain Measurements

2011 ◽  
Author(s):  
John G. Michopoulos ◽  
Athanasios Iliopoulos
Keyword(s):  
Experimental Results ◽  
Loading Conditions ◽  
Strain Fields ◽  
Full Field ◽  
Strain Measurements ◽  
Flat Surfaces ◽  
3D Space ◽  
Random Grid ◽  
Computational Implementation ◽  
Out Of Plane

The present paper reports on the progress towards the development of a computational workbench infrastructure that implements the Meshless Random Grid (MRG) method for the remote (non contact) measurement of displacement and strain fields in 3D space. The method is applicable to structures bounded by flat surfaces that deform under various mechanical and generalized loading conditions in and out of plane. A brief description of the 3D MRG method is followed by the description of the current prototype of a software workbench developed for the computational implementation of the algorithms involved with the analysis display and export of the experimental results associated with any specific applications of the method.

A Computational Workbench for Remote Full Field 2D Displacement and Strain Measurements

2009 ◽  
Author(s):  
J. G. Michopoulos ◽  
A. P. Iliopoulos
Keyword(s):  
Grid Method ◽  
Experimental Results ◽  
Loading Conditions ◽  
Strain Fields ◽  
Full Field ◽  
Strain Measurements ◽  
Flat Surfaces ◽  
Mesh Free ◽  
Random Grid ◽  
Computational Implementation

The present paper reports on the progress towards the development of a computational workbench infrastructure that implements the Mesh Free Random Grid Method (MFRGM) for the remote (non contact) measurement of displacement and strain fields. The method is applicable to structures bounded by flat surfaces that deform under various mechanical and generalized loading conditions. A brief description of MFRGM is followed by the description of the current prototype of a software workbench developed for the computational implementation of the algorithms involved with the analysis display and export of the experimental results associated with any specific applications of the method. Displacement validation as well as two examples of its usage are also presented.

Accuracy of Inverse Composite Laminate Characterization via the Mesh Free Random Grid Method

2009 ◽  
Author(s):  
J. G. Michopoulos ◽  
A. P. Iliopoulos ◽  
T. Furukawa
Keyword(s):  
Grid Method ◽  
Constitutive Law ◽  
Forward Solution ◽  
Strain Fields ◽  
Flat Surfaces ◽  
Mesh Free ◽  
Random Grid ◽  
Open Hole ◽  
Constitutive Parameters

The present paper reports on the progress towards the evaluation of the Mesh Free Random Grid Method (MFRGM) for the inverse constitutive characterization of composite materials. The method provides the capability for the remote (non contact) measurement of displacement and strain fields of structures bounded by flat surfaces that deform under various mechanical and generalized loading conditions. The known forward solution of an anisotropic plate with an open hole, loaded at infinity, is used to generate synthetic images MFRG. The inverse problem for determining the constitutive parameters formulated directly on the generalized constitutive law. Performance of the technique is evaluated by the usage of just one frame corresponding to one set of strain state for various amounts of noise. The evaluation is repeated by utilizing frames corresponding to different rotations of the laminate relative to the loading direction. Finally the exceedingly accurate behavior of the methodology is discussed.

Multi-Scale Strain Measurements of a Particulate Composite Material

2002 ◽  
Author(s):  
C. T. Liu ◽  
C. W. Smith ◽  
G. Ravichandran
Keyword(s):  
Composite Material ◽  
Particulate Composite ◽  
Experimental Results ◽  
Strain Fields ◽  
Length Scales ◽  
Strain Measurements ◽  
Multi Scale ◽  
Hard Particles ◽  
Particulate Composite Material

In this study, the strain fields on two different length scales in a particulate composite material containing hard particles embedded in a rubbery matrix were investigated, using two different techniques. The experimental results were analyzed and are discussed.

Performance Analysis of the Mesh-Free Random Grid Method for Full-Field Synthetic Strain Measurements

Strain ◽  
2010 ◽  
Vol 48 (1) ◽  
pp. 1-15 ◽  
Author(s):  
A. P. Iliopoulos ◽  
J. G. Michopoulos ◽  
N. P. Andrianopoulos
Keyword(s):  
Performance Analysis ◽  
Grid Method ◽  
Full Field ◽  
Strain Measurements ◽  
Mesh Free ◽  
Random Grid

scholarly journals A novel specimen shape for measurement of linear strain fields by means of digital image correlation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nedaa Amraish ◽  
Andreas Reisinger ◽  
Dieter Pahr
Keyword(s):  
Digital Image Correlation ◽  
Image Correlation ◽  
Strain Gauges ◽  
Linear Strain ◽  
Strain Fields ◽  
Strain Gradients ◽  
Full Field ◽  
Strain Measurements ◽  
Deformation Stages ◽  
Specimen Shape

AbstractStrains on the surface of engineering structures or biological tissues are non-homogeneous. These strain fields can be captured by means of Digital Image Correlation (DIC). However, DIC strain field measurements are prone to noise and filtering of these fields influences measured strain gradients. This study aims to design a novel tensile test specimen showing two linear gradients, to measure full-field linear strain measurements on the surface of test specimens, and to investigate the accuracy of DIC strain measurements globally (full-field) and locally (strain gauges’ positions), with and without filtering of the DIC strain fields. Three materials were employed for this study: aluminium, polymer, and bovine bone. Normalized strain gradients were introduced that are load independent and evaluated at two local positions showing 3.6 and 6.9% strain change per mm. Such levels are typically found in human bones. At these two positions, two strain gauges were applied to check the experimental strain magnitudes. A third strain gauge was applied to measure the strain in a neutral position showing no gradient. The accuracy of the DIC field measurement was evaluated at two deformation stages (at $$\approx $$ ≈ 500 and 1750 μstrain) using the root mean square error (RMSE). The RMSE over the two linear strain fields was less than 500 μstrain for both deformation stages and all materials. Gaussian low-pass filter (LPF) reduced the DIC noise between 25% and 64% on average. As well, filtering improved the accuracy of the local normalized strain gradients measurements with relative difference less than 20% and 12% for the high- and low-gradient, respectively. In summary, a novel specimen shape and methodological approach are presented which are useful for evaluating and improving the accuracy of the DIC measurement where non-homogeneous strain fields are expected such as on bone tissue due to their hierarchical structure.

Curved Wide Plate Testing With Advanced Instrumentation and Interpretation

2012 ◽  
Author(s):  
Stijn Hertelé ◽  
Matthias Verstraete ◽  
Koen Van Minnebruggen ◽  
Rudi Denys ◽  
Wim De Waele
Keyword(s):  
Crack Extension ◽  
Test Procedure ◽  
Element Model ◽  
Field Strain ◽  
Strain Fields ◽  
Full Field ◽  
Strain Measurements ◽  
Experimental Tool ◽  
Unloading Compliance ◽  
Girth Welds

Curved wide plate testing is a valuable experimental tool to determine the strain capacity of flawed pipeline girth welds under tension. However, its design, test procedure and analysis are not standardized to date. In an effort to contribute to these three aspects, the authors have executed medium scale (curved) wide plate tests with full field strain measurements and unloading compliance crack extension measurements. This paper discusses specifications, possibilities and limitations of both features and provides representative results. Full field strain measurements and unloading compliance analysis support the validation of a finite element model for curved wide plate testing, and confirm the ability to obtain uniform strain fields in the pipe sections. It is expected that these results may contribute to a future standardization of the curved wide plate test.

Investigation of Dynamic Responses for Piezoceramic Plates in Resonance by Using Fiber Bragg Grating

2009 ◽  
Vol 25 (4) ◽  
pp. 379-388
Author(s):  
K.-C. Chuang ◽  
C.-C. Ma ◽  
C.-Y. Liang
Keyword(s):  
Fiber Bragg Grating ◽  
Experimental Results ◽  
Sensor System ◽  
Displacement Sensor ◽  
Bragg Grating ◽  
Piezoceramic Plate ◽  
Full Field ◽  
Fbg Sensor ◽  
Out Of Plane ◽  
Dynamic Signal

ABSTRACTA fiber Bragg grating (FBG) sensor system which can simultaneously measure the point-wise, out-of-plane and in-plane dynamic displacements is proposed. A demodulation system based on the fiber Bragg grating filter is used. The steady-state responses of particle motions of a piezoceramic plate measured by the FBG out-of-plane and in-plane displacement sensors are simultaneously compared with those obtained by a laser Doppler vibrometer (LDV) and a surface-mounted FBG strain sensor, respectively. The integration of the FBG displacement sensor with a dynamic signal analyzer (FBG-DSA) forms a measurement system which has the ability to acquire the frequency response of a piezoceramic plate. An LDV-DSA system and an impedance analyzer are used to compare the results obtained from the dynamic signal analyzer combined with the out-of-plane FBG sensor (OFBG-DSA) and the in-plane FBG sensor (IFBG-DSA), respectively. The experimental results of the impulse excitation as well as the random excitation of the piezoceramic plate are also presented. To explain the experimental results, an optical full-field measurement technique called amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and FEM numerical calculations are also used to provide full-field vibration mode shapes of the piezoceramic plate. These results indicate that the proposed displacement sensor system has the multiplexing capability to measure the dynamic displacements up to 45kHz.

scholarly journals X-ray absorption spectroscopy by full-field X-ray microscopy of a thin graphite flake: Imaging and electronic structure via the carbon K-edge

2012 ◽  
Vol 3 ◽  
pp. 345-350 ◽  
Author(s):  
Carla Bittencourt ◽  
Adam P Hitchock ◽  
Xiaoxing Ke ◽  
Gustaaf Van Tendeloo ◽  
Chris P Ewels ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Topological Defects ◽  
Sodium Cholate ◽  
Graphite Flake ◽  
Full Field ◽  
X Ray ◽  
Graphene Layers ◽  
Metal Impurities ◽  
Out Of Plane ◽  
X Ray Absorption

We demonstrate that near-edge X-ray-absorption fine-structure spectra combined with full-field transmission X-ray microscopy can be used to study the electronic structure of graphite flakes consisting of a few graphene layers. The flake was produced by exfoliation using sodium cholate and then isolated by means of density-gradient ultracentrifugation. An image sequence around the carbon K-edge, analyzed by using reference spectra for the in-plane and out-of-plane regions of the sample, is used to map and spectrally characterize the flat and folded regions of the flake. Additional spectral features in both π and σ regions are observed, which may be related to the presence of topological defects. Doping by metal impurities that were present in the original exfoliated graphite is indicated by the presence of a pre-edge signal at 284.2 eV.

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