scholarly journals Comparing full-field data from structural components with complicated geometries

2021 ◽  
Vol 8 (9) ◽  
pp. 210916
Author(s):  
W. J. R. Christian ◽  
A. D. Dean ◽  
K. Dvurecenska ◽  
C. A. Middleton ◽  
E. A. Patterson
Keyword(s):  
Thermoelastic Stress ◽  
Image Correlation ◽  
Qr Factorization ◽  
Process Data ◽  
Element Analysis ◽  
Full Field ◽  
Measurement Systems ◽  
Stress And Deformation ◽  
Complicated Geometries ◽  
Comparison Technique

A new decomposition algorithm based on QR factorization is introduced for processing and comparing irregularly shaped stress and deformation datasets found in structural analysis. The algorithm improves the comparison of two-dimensional data fields from the surface of components where data is missing from the field of view due to obstructed measurement systems or component geometry that results in areas where no data is present. The technique enables the comparison of these irregularly shaped datasets without the need for interpolation or warping of the data necessary in some other decomposition techniques, for example, Chebyshev or Zernike decomposition. This ensures comparisons are only made between the available data in each dataset and thus similarity metrics are not biased by missing data. The decomposition and comparison technique has been applied during an impact experiment, a modal analysis, and a fatigue study, with the stress and displacement data obtained from finite-element analysis, digital image correlation and thermoelastic stress analysis. The results demonstrate that the technique can be used to process data from a range of sources and suggests the technique has the potential for use in a wide variety of applications.

scholarly journals Towards a Planar Cruciform Specimen for Biaxial Characterisation of Polymer Matrix Composites

2010 ◽  
Vol 24-25 ◽  
pp. 115-120 ◽  
Author(s):  
Michael R.L. Gower ◽  
Richard M. Shaw
Keyword(s):  
Strain Distribution ◽  
Stress Raiser ◽  
Test Method ◽  
Image Correlation ◽  
Strain Gauges ◽  
Test Machine ◽  
Element Analysis ◽  
Full Field ◽  
Cruciform Specimen ◽  
Gauge Section

This paper details work undertaken towards the development of a standard test method for the biaxial response of planar cruciform specimens manufactured from carbon fibre-reinforced plastic (CFRP) laminates and subject to tension-tension loading. Achieving true biaxial failure in a cruciform specimen without the need for the inclusion of a stress raiser, such as a hole, in the gauge-section, is a subject attracting much research globally and is by no means a trivial exercise. Coupon designs were modelled using finite element analysis (FEA) in order to predict the stress and strain distributions in the central region of the specimen. An Instron biaxial strong-floor test machine was used to test the specimens. Strain gauges were used to measure the strain in the specimen arms and to assess the degree of bending. Digital image correlation (DIC) was used to measure the full-field strain distribution in the central gauge-section of the specimen and this was compared to values measured using strain gauges. The strain readings obtained from strain gauges, DIC and FEA predictions were in good agreement and showed that the strain distribution was uniform in the central gauge-section, but that strain concentrations existed around the tapered thickness zone. These regions of strain concentration resulted in interlaminar failure and delamination of the laminate propagating into the specimen arms.

Shear Test on CFRP Full-Field Measurement and Finite Element Analysis

2010 ◽  
Vol 112 ◽  
pp. 49-62 ◽  
Author(s):  
Sébastien Mistou ◽  
Marina Fazzini ◽  
Moussa Karama
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shear Modulus ◽  
Shear Test ◽  
Image Correlation ◽  
Optical Methods ◽  
Strain Gauges ◽  
Element Analysis ◽  
Full Field ◽  
Full Field Measurement

The purpose of this work is to study the Iosipescu shear test and more precisely its ability to characterize the shear modulus of a carbone/epoxy composite material. The parameters influencing this identification are the fibre orientation, the geometry of the notch and the boundary conditions. Initially these parameters were studied through the finite element analysis of the shear test. Then, the measurement of the shear strains was carried out by traditional methods of measurement (strain gauges) but also by optical methods. These optical methods: the digital image correlation and the electronic speckle pattern interferometry (ESPI); allow for various levels of loading, to reach a full-field measurement of the shear strain. This enabled us to study the strain distribution on the section between the two notches. The finite element model enabled us to study the parameters influencing the calculation of the shear modulus in comparison with strain gauges, image correlation and ESPI. This work makes it possible to conclude on optimal parameters for the Iosipescu test.

Combined thermoelastic stress analysis and digital image correlation with a single infrared camera

2011 ◽  
Vol 46 (8) ◽  
pp. 783-793 ◽  
Author(s):  
M L Silva ◽  
G Ravichandran
Keyword(s):  
Digital Image Correlation ◽  
Stress Analysis ◽  
Digital Image ◽  
Thermoelastic Stress ◽  
Infrared Camera ◽  
Image Correlation ◽  
Measured Temperature ◽  
Thermoelastic Stress Analysis ◽  
Alloy Plate ◽  
Full Field

A novel methodology simultaneously combining thermoelastic stress analysis (TSA) and digital image correlation (DIC) with a single infrared camera is presented. DIC is an optical method to determine deformation by image tracking with strains determined via differentiation. TSA is a non-contact measurement technique that provides the full-field stress directly using measured temperature changes. The combination of the two techniques improves the resolution and accuracy of TSA results by correcting for sample motion and distortion during loading. Illustrative examples, including an aluminium alloy plate with an edge crack and a nylon plate with a hole under tension, demonstrate the combined method which simultaneously measures stress and displacement.

On the Calibration of Optical Full-Field Strain Measurement Systems

2006 ◽  
Vol 3-4 ◽  
pp. 397-402 ◽  
Author(s):  
Maurice P. Whelan ◽  
Erwin Hack ◽  
Thorsten Siebert ◽  
Richard L. Burguete ◽  
E.A. Patterson ◽  
...  
Keyword(s):  
Strain Measurement ◽  
Parametric Design ◽  
Image Correlation ◽  
Standard Reference Materials ◽  
Full Field ◽  
Measurement Systems ◽  
Measurement Protocol ◽  
Optical Strain Measurement ◽  
Optical Strain ◽  
Point Bend

There are no standard reference materials suitable for the calibration of full-field optical strain measurement systems. This is hindering the uptake of the technology by industrial end-users since optical metrology instrumentation and procedures cannot be easily integrated into quality assurance systems. The EU-funded SPOTS project is developing a physical reference material (PRM) and measurement protocol that should provide the basis of a calibration standard for establishing the traceability of strain values obtained with optical devices. This paper describes a PRM based on a parametric design of monolithic four-point bend test that can reliably generate a known strain field over a range of specimen sizes. Measurements acquired from strain gauges and LVDTs compared well with data obtained from ESPI, digital image correlation, photoelasticity and thermoelasticity studies, demonstrating excellent repeatability and inter-laboratory reproducibility.

Characterization of Creep Behavior of Actual Lead-Free Solder Joint for Modeling

2014 ◽  
Author(s):  
Hohyung Lee ◽  
Ruiyang Liu ◽  
Seungbae Park ◽  
Jae Kwak
Keyword(s):  
Solder Joint ◽  
Creep Behavior ◽  
Solder Ball ◽  
Life Time ◽  
Bulk Solder ◽  
Image Correlation ◽  
Element Analysis ◽  
Full Field ◽  
2D Digital Image Correlation ◽  
Field Displacement

Creep deformation on solder plays important role in life time of an electronic package. Traditionally, mechanical properties of solders have been tested using bulk solder samples. However, mechanical behaviors of bulk solder and actual solder ball exhibit huge discrepancy due to the different size of the micro structure and existence of inter metallic layers. In this reason, to acquire reliable creep behavior of the solder joint, the actual solder ball need to be tested. In this study, 2D digital image correlation (DIC) technique with microcopy is used to investigate the creep behavior of the actual BGA solder balls from the packages. The full field displacement data of the cross sectioned solder ball are generated while various constant loading is applied at different isothermal temperature. From the full field displacement data, constant creep rates of the actual BGA solder ball are obtained. Using the constants from the experiment, finite element analysis is performed to validate the experiment results by comparing the displacement of the DIC experiment results and FEA modeling.

An Investigation of the Ring Hoop Tension Test for Anisotropic Tubes

2014 ◽  
Author(s):  
Christopher P. Dick ◽  
Yannis P. Korkolis
Keyword(s):  
Contact Pressure ◽  
Tension Test ◽  
Negligible Effect ◽  
Image Correlation ◽  
Element Analysis ◽  
Material Response ◽  
Full Field ◽  
Al 6061 ◽  
Full Field Measurement ◽  
Nominal Thickness

The ring hoop tension test (RHTT) is investigated experimentally and numerically to determine its validity and limitations in predicting the hoop response of materials in tubular form. Our experiments involved RHT-Testing of Al-6061-T4 tubes. Digital image correlation (DIC) was used to capture the strain evolution in the gage section of the specimens, giving a full-field measurement of the strains. The local hoop stress-strain response of the material was assessed in this way. Finite element analysis was used to further investigate the effects of friction, eccentricity and contact pressure on the recorded response. Friction was found to have a negligible effect on the recorded response for friction coefficient values of 0.01 and lower. However, it was found that larger values of friction may render the test meaningless. Tube eccentricity of the magnitude present in the tubes tested here (±4% of the nominal thickness) was determined to have no effect on the material response. It was also determined that tubes should not be turned to a uniform thickness as this may induce machining damage and release the existing residual stresses, thus causing error in determining the tube response in the hoop direction. The contact pressure was found to not significantly affect the state of uniaxial tension in the specimen and thus to have a negligible effect on the material response. By comparing the hoop with the axial response, the material anisotropy of the Al-6061-T4 tubes was established.

A Full-Field Stress Based Damage Assessment Approach for In Situ Inspection of Composite Structures

2013 ◽  
Vol 569-570 ◽  
pp. 3-10 ◽  
Author(s):  
Janice M. Dulieu-Barton ◽  
R.K. Fruehmann ◽  
Simon Quinn
Keyword(s):  
Composite Structures ◽  
Speckle Pattern ◽  
Stress Raiser ◽  
Thermoelastic Stress ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Inspection Method ◽  
Full Field ◽  
Distribution Of Stresses

This paper describes the development of a stress / strain based in-situ damage inspection strategy focused around, but not exclusively, using thermoelastic stress analysis (TSA). The underlying philosophy is that defects and damage in a component or structure only constitute a cause for concern if these influence the stress field, i.e. the defect or damage acts as a stress raiser that reduces the service load limit. To assess this, it is necessary for the inspection method to map the distribution of stresses in the component, rather than the location and extent of an irregularity in the material. Imaging based techniques, such as TSA, digital image correlation (DIC) or digital speckle pattern interferometry (DSPI) provide non-contact maps of the surface stresses, deformations and/or strains. The full field data enables the engineer to evaluate if stress concentrations are present within the structure and, if data from a previous inspection is available, to assess if the distribution of stresses within the structure has changed from a previous 'undamaged' state. One of the key issues addressed in the current work has been the transition from a standard test setup, as typically used in laboratory work, to a more flexible (portable) setup relevant to industry requirements, e.g. site inspections. An approach that enables similar resolution (by comparison to current laboratory standard setups) stress and strain data to be captured using natural frequency excitation of a structure has been demonstrated on various full scale components.

scholarly journals Determination of the Characteristic Parameters of Tension-Compression Asymmetry of Shape Memory Alloys Using Full-Field Measurements

2013 ◽  
Vol 738-739 ◽  
pp. 281-286 ◽  
Author(s):  
Yves Chemisky ◽  
Rachid Echchorfi ◽  
Fodil Meraghni ◽  
Nadine Bourgeois ◽  
Boris Piotrowski
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Field Measurements ◽  
Type Specimen ◽  
Image Correlation ◽  
Identification Algorithm ◽  
Characteristic Parameters ◽  
Element Analysis ◽  
Full Field ◽  
Tension Compression Asymmetry

In this work, a method for the identification of the transformation surface of Shape Memory Alloys based on full field measurements is presented. An inverse method coupled with a gradient-based algorithm has been developed to determine the characteristic parameters of the transformation surface. The constitutive equations of the chosen model that capture the macroscopic behavior of Shape Memory Alloys are first presented. The material parameters, to be identified, that are characteristic of the tension-compression asymmetry of the alloy are detailed. The identification algorithm, based on full field measurements obtained by Digital Image Correlation (DIC) and numerical simulation by Finite Element Analysis are introduced. The identification algorithm is validated using a numerically generated strain field on a Meuwissen-type specimen.

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