Digital Image Correlation: Advanced Methods and Applications

125 Pages·2017·7.042 MB·English

by  David Chambers, (Editor)

MATERIALS SCIENCE AND TECHNOLOGIES

D I C
IGITAL MAGE ORRELATION

A M
DVANCED ETHODS
A
AND PPLICATIONS

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M S
ATERIALS CIENCE
T
AND ECHNOLOGIES

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MATERIALS SCIENCE AND TECHNOLOGIES

D I C
IGITAL MAGE ORRELATION

A M
DVANCED ETHODS
A
AND PPLICATIONS

DAVID CHAMBERS
EDITOR
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ISBN: (cid:28)(cid:26)(cid:27)(cid:16)(cid:20)(cid:16)(cid:24)(cid:22)(cid:25)(cid:20)(cid:20)(cid:16)(cid:27)(cid:28)(cid:20)(cid:16)(cid:28)(cid:3)(cid:11)(cid:72)(cid:37)(cid:82)(cid:82)(cid:78)(cid:12)

Published by Nova Science Publishers, Inc. † New York
CONTENTS

Preface vii
Chapter 1 Improving the Reliability of 2D DIC by Using
Fourier-Mellin Transform 1
Oleksandr P. Maksymenko
and Oleksandr M. Sakharuk
Chapter 2 Incipient Necking Criteria for the
Determination of Forming Limit Curves
Using Digital Image Correlation 37
Gang Huang and Sriram Sadagopan
Chapter 3 A Robust Optical Method for
Tracking Mechanism Components 65
A. A. Cruz-Cabrera, M. Herzberg,
M. Palaviccini, D. Z. Turner
and S. Walkington
vi Contents
Chapter 4 Digital Image Correlation Applied to Analyze the
Stress-Strain Evolution of Structural Materials
under Compression 85
Alonso Saldaña Heredia,
Pedro A. Márquez Aguilar
and Arturo Molina Ocampo
Index 111
PREFACE

During surface deformations measurements in objects, materials or
structural element samples, which move in the space, recorded speckle
images are transformed by these displacements. In Chapter One, an
algorithm for speckle image relative geometrical transformations
parameters determination is proposed on the basis of Fourier-Mellin
transform. Usage of this algorithm will allow increasing reliability of
deformation fields’ determination for constructional materials after
appropriate correction of speckle-images, which are used during
calculations. In Chapter Two, methods are presented to determine forming
limit curves (FLCs) for sheets of advanced high strength steels (AHSS)
using digital image correlation (DIC). FLC is a valuable tool for failure
prediction in forming simulation at design stage and die try-out in press
shops. Chapter Three presents a novel algorithm for recovering the
trajectories of mechanism components from high speed video by means of
multidimensional simplex optimization and conformal templates. The
focus of this chapter is on a simplex-based approach to digital image
correlation (DIC) with arbitrarily shaped subsets that provides a number of
advantages over the traditional gradient based approach with strictly square
subsets. Finally, Chapter Four aims to develop a different technique that
allows the obtention of the stress-strain evolution of materials while they
are under axial loads.
viii David Chambers
Chapter 1 - During surface deformation measurements in objects,
material or structural element samples, that move in space, recorded
speckle images are transformed by such displacements. During
measurement, relative rotations of a studied surface and change in distance
between a video camera and lens typically occur. They cause recorded
images relative rotations and scale changes. An algorithm for determining
speckle image relative geometrical transformations parameters is proposed
on the basis of the Fourier-Mellin transform. An image transformation
parameter determined by this algorithm, can be used further to analyze
spatial displacements of a control surface in relation to the recording
system and to correct the speckle-images. Using this algorithm will
improve the reliability of deformation field determination for
constructional materials, after appropriate correction of the speckle-images
used during calculations. Corrective parameter errors determination by the
proposed algorithm was analyzed and their influence on the accuracy of
real deformation field determination was demonstrated. Analytical error
equations for determining speckle-image geometric transformation
parameters were derived. According to these expressions, the errors
depend on the image size and precision of sub-pixel accuracy algorithm
used for determining cross-correlation peak coordinates. Computer
simulation and experimental measurements were utilized for demonstrating
the validity of the analytical estimations. The obtained results show that
usage of a simple, inexpensive video camera with a resolution of 1280 ×
1024 pixels and the developed algorithm can provide accurate parameters
of speckle-image relative geometrical transformation. It was proven by
experiment that errors of speckle-image relative rotation angle
determination are linearly and inversely proportional to image size and are
less than 0.01 degrees for the relative speckle-images rotation within a
range of ± 5 degrees. The errors of scale detrmination do not exceed 0.1%
for the speckle-image scale changes within ±0.5%. For unambiguous cross-
correlation peak detection during the proposed algorithm realization, high-
frequency filtering of speckle images spectrum amplitudes prior to log-
polar transformations is recommended. A Hann spatial filter was used for
this purpose. The conducted experiments also indicated that the developed
Preface ix
algorithm can be used successfully for determining the change in distance
to an object control surface with a relative error of tenths of a percent. The
optical system should be adjusted before measurement in order to establish
the relationship between speckle-image scale change and distance.
Chapter 2 - Forming limit curve (FLC) is a valuable tool for failure
prediction in forming simulation at design stage and die try-out in press
shops. In this chapter, methods are presented to determine FLCs for sheets
of advanced high strength steels (AHSS) using digital image correlation
(DIC). Dome tests were conducted on AHSS specimens using DIC system
for strain measurement. Two incipient necking criteria are developed to
determine the onset of localized necking by analyzing the strain history at
critical locations. The first criterion is based on the time dependent
characteristic of the incipient necking formation, and the second criterion
uses the time and position relationship during the course of necking
development of AHSS. The second incipient necking criterion has been
implemented into the commercial DIC software Vic-3D (Correlated
Solution Inc.). The measured FLCs for several AHSS were compared to
the FLCs using ISO 12004-2, the conventional North American
experimental measurements and empirical equations. The results of
comparison revealed that FLCs using DIC are in good correlation with
other existing data, thus validating the presented methodologies.
Chapter 3 - This work presents a novel algorithm for recovering the
trajectories of mechanism components from high speed video by means of
multidimensional simplex optimization and conformal templates. The
proposed method is robust in that it can be used for patterned or
unpatterned components, parts with oblong shapes, and mechanisms that
involve moving obstructions that block the camera’s field of view. The
focus of this work is on a simplex-based approach to digital image
correlation (DIC) with arbitrarily shaped subsets that provides a number of
advantages over the traditional gradient-based approach with strictly
square subsets. The authors demonstrate the effectiveness of the proposed
approach for a number of complex problems that cannot be surmounted by
traditional methods.