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.

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.

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.

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

Effects of Anisotropy on the Performance Sensitivity of the Mesh-Free Random Grid Method for Whole Field Strain Measurement

2009 ◽  
Author(s):  
A. P. Iliopoulos ◽  
J. G. Michopoulos
Keyword(s):  
Sensitivity Analysis ◽  
Anisotropic Medium ◽  
Orientation Angle ◽  
Grid Method ◽  
Strain Fields ◽  
Mesh Free ◽  
Random Grid ◽  
Open Hole ◽  
Realistic Choice ◽  
Accuracy Performance

The recently developed mesh-free random grid method (MFRGM) has been exhibiting very promising characteristics of accuracy, adaptability, implementation flexibility and efficiency. These are essential features enabling material characterization methodologies that depend on the experimental measurement of displacement and strain fields. The aim of the present paper is to present a sensitivity analysis that aids into determining the effects of the material or loading orientation of an anisotropic medium with an open hole and critical computational parameters characterizing the MFRGM in terms of its accuracy performance. First a brief outline of the MFRGM is provided. A sensitivity analysis based on the effect of the orientation angle of an anisotropic medium with an open hole is presented for a realistic choice of experimental (optical) characteristics. Finally, the effects of the mean dot size and dot distance (that are essential experimental parameters of the method) on the strain fields, are presented.

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.

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.

Performance Sensitivity Analysis of the Mesh-Free Random Grid Method for Whole Field Strain Measurements

2008 ◽  
Author(s):  
A. P. Iliopoulos ◽  
J. G. Michopoulos ◽  
N. P. Andrianopoulos
Keyword(s):  
Sensitivity Analysis ◽  
Grid Method ◽  
Performance Characteristics ◽  
Field Strain ◽  
Performance Specification ◽  
Mesh Free ◽  
Random Grid ◽  
Minimization Algorithms ◽  
Selection Of

In responding to the needs of the material characterization community, the recently developed mesh-free random grid method (MFRGM) has been exhibiting very promising characteristics of accuracy, adaptability, implementation flexibility and efficiency. In order to address the design specification of the method according to the intended application, in the present paper we are presenting a sensitivity analysis that aids into determining the effects of the experimental and computational parameters characterizing the MFRGM in terms of its performance. There are two sets of parameters that affect the performance characteristics of MFRGM for whole field strain measurement applications. The first set involves parameters associated with the characteristics of the experimental setup and the random grid applied on the specimen under measurement. The second set involves the computational characteristics of the mesh-free approximation and the solution (minimization) algorithms utilized. The performance characteristics of the MFRGM are mainly its accuracy, sensitivity, smoothing properties and efficiency. In the present paper we are presenting a classification of the first set of parameters as well as their relationship followed by the above mentioned sensitivity analysis to establish the influence trends in the performance characteristics with the intension to optimize the selection of the user controlled variables for a desired performance specification.

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.

Experimental Validation of the 2D Meshless Random Grid Method

2011 ◽  
Author(s):  
Athanasios Iliopoulos ◽  
John G. Michopoulos ◽  
Adrian C. Orifici ◽  
Rodney S. Thomson
Keyword(s):  
Experimental Validation ◽  
Grid Method ◽  
Element Analysis ◽  
Full Field ◽  
Full Field Measurement ◽  
Preliminary Validation ◽  
Systematic Effort ◽  
Random Grid ◽  
Open Hole ◽  
Accuracy Performance

This paper presents the first systematic effort for the experimental validation of the 2D Meshless Random Grid Method (MRGM) for the full field measurement of displacement and strain fields. Although the MRGM has been demonstrating very promising characteristics of accuracy, performance and ease of application based on previously conducted sensitivity analysis supported by virtual data, extensive experimental validation was not available until now. This work comes to fill this gap and presents preliminary validation results against strain gauge data collected from open hole tension experiments of composite specimens. In addition, strain and displacement field verification is performed by comparison studies with finite element analysis results.

Development of a Full-Field Displacement Measurement Technique at the Microscale and Application to the Study of Strain Fields in a Tensile Steel Specimen

2007 ◽  
Vol 7-8 ◽  
pp. 181-186
Author(s):  
Raphaël Moulart ◽  
René Rotinat ◽  
Fabrice Pierron ◽  
Gilles Lérondel
Keyword(s):  
Mechanical Test ◽  
Grid Method ◽  
Steel Specimen ◽  
Field Method ◽  
Phase Shifting ◽  
Periodic Pattern ◽  
Test Results ◽  
Strain Fields ◽  
Full Field ◽  
Basic Features

This work deals with the development of a full-field extensometric method at a micrometric scale in order to precisely identify the local features of a metallic alloy at the scale of the grains. The full-field method that has been chosen is the grid method that applies a spatial phase-shifting algorithm to a periodic pattern. To mark the sample, direct interferometric photolithography was used. The paper presents the basic features of the technique and first mechanical test results are commented.

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