The high resolution technique of electronic speckle pattern interferometry (ESPI) can be very useful in determining deformation of laboratory specimens and identifying initiation of failure. The in-plane ESPI theory is described and the fringe pattern of the processed ESPI image is analyzed to determine deformation and crack opening displacement. Fringes on the ESPI image represent lines of equal intensity, which relate to surface displacement. An ESPI system was constructed and calibrated for measuring uni-directional displacements. Several types of the experiments, such as uniaxial compression and fracture testing, were conducted to demonstrate the utility of ESPI.
#2Luigi Biolzi(Polytechnic University of Milan)H-Index: 26
In the classical work of Fairhurst and co-workers on machine stiffness, it was shown that the failure response of a rock specimen can be a mixture of material and structural behavior. This is due to the development, around peak stress, of a localized region of microcracking called the intrinsic zone, which may be a property of the rock. The inhomogeneity formed by the intrinsic zone has a fundamental importance for defining the system behavior in terms of material strength and post-peak instabil...
This paper presents the experimental results obtained with a two-dimensional indentation device controlled by a servo-hydraulic loading system and monitored with the nondestructive techniques of acoustic emission and electronic speckle pattern interferometry. The goals of this research were to evaluate the indentation pressure as well as the size of a damage (plastic) zone, and to study the initiation of tensile fracture at the intact rock-damaged rock boundary, that is, the elasto-plastic inter...
Most chapters include an Introduction, Summary, References and Exercises. 1. Introduction to Fracture Mechanics. Historical Overview of Brittle Fracture. Elementary Brittle-Fracture Theories. Crack Extension Behavior. 2. Elements of Solid Mechanics. Concepts of Stress and Strain. Equations of Elasticity in Cartesian Coordinates. Equations of Elasticity in Polar Coordinates. Solution of the Biharmonic Equation. The Problem of the Elliptical Hole. 3. Elasticity of Singular Stress Fields. Overview....
Some laboratory nondestructive evaluation techniques have been invaluable in studying fracture processes in concrete. Several nondestructive evaluation methods including acoustic emission (AE), computer vision, digital speckle pattern interferometry (DSPI), and X-ray microtomography (XMT) were used to examine the fracture behavior of concrete in tension and compression. Acoustic emission testing was used in an attempt to characterize the fracture properties of individual microcracks. As the spec...
#1Jon N. Petzing(Lboro: Loughborough University)H-Index: 14
#2John R. Tyrer(Lboro: Loughborough University)H-Index: 21
AbstractElectronic speckle pattern interferometry (ESPI) is a wholefield non-contact optical metrology technique for displacement measurement, based on the optical physics of surface-generated laser speckle. Since its inception during the early 1970s ESPI has gradually evolved into different optical designs and has been applied to a range of engineering and non-engineering applications. Development of ESPI has continued during the 1990s with the introduction of new laser and optical technology i...
Last. Robert E. Rowlands(UW: University of Wisconsin-Madison)H-Index: 23
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The fracture process zone (FPZ) ahead of a crack tip in concrete and mortar beams subjected to threepoint bending was studied using moire interferometry. A large FPZ can occur in concrete before the external load reaches its maximum value. Comparing the experimental results between concrete and mortar suggests that the aggregate contributes to the formation of the large FPZ in concrete. The formation of this large FPZ makes concrete less brittle than mortar. The effect of the FPZ on the fracture...
Last. John R. Tyrer(Lboro: Loughborough University)H-Index: 21
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We describe an electronic speckle pattern interferometer devised to measure orthogonal in-plane strain components simultaneously and automatically. The interferometer is based on an earlier system that measured two in-plane displacement components simultaneously. Automatic displacement analysis is achieved using a phase-stepping technique. The surface strain is then calculated by numerical differentiation of the displacement data. Simultaneous measurement of the two displacement components is im...
Electronic speckle pattern interferometry (ESPI) can be a powerful tool for efficient non-destructive testing and evaluation of micro-deformations of materials and structures. Unlike traditional transducers, ESPI requires no direct contact with the inspected object and the full-field visualization provides better understanding of the surface behaviour. The authors describe an in-plane deformation inspection system, which offers automatic acquisitions of interferograms at different stages of a te...
#1Gary Cloud(MSU: Michigan State University)H-Index: 15
Introduction 1. Light and interference 2. Classical interferometry 3. Photoelasticity theory 4. Basic applied photoelasticity 5. Photoelasticity methods and applications 6. Geometrical moire theory 7. In-plane motion and strain measurement 8. Moire mapping of slope, contour and displacement 9. Diffraction and Fourier optics 10. Moire with diffraction and Fourier optical processing 11. Procedures of moire analysis with optical processing 12. Principles of moire interferometry 13. A moire interfer...
Last. Qi Zhao(BFU: Beijing Forestry University)H-Index: 1
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Monitoring the cracks initiation and propagation of construction materials, as well as determining the fracture process zone, constitute two key factors to understand the damage mechanism of materials in order to control the risk of material degradation and failure. This paper demonstrates the results of a laboratory static test designed to investigate the in situ monitoring of crack tip growth in wood. LT-type single-edge notched specimens made of Chinese fir with the seam height ratio of 0.1, ...
Last. Bo Yuan(Guida: Guizhou University)H-Index: 1
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In order to study the size effect in concrete fracture, three-point bending tests are performed on five groups of geometrically similar concrete beams. The electronic speckle pattern interferometry...
#1Ziguang Chen(HUST: Huazhong University of Science and Technology)H-Index: 17
#2Sina Niazi(NU: University of Nebraska–Lincoln)H-Index: 9
Last. Florin Bobaru(NU: University of Nebraska–Lincoln)H-Index: 32
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Abstract We introduce a peridynamic (PD) model for simulating brittle damage and fracture in elastic porous materials based on an Intermediate Homogenization (IH) approach. In this approach, instead of explicitly representing the detailed pore geometry, we use homogenization but maintain some information about the microstructure (porosity) in the model. Porosity is introduced in the model as initial peridynamic damage, implemented by stochastically pre-breaking peridynamic bonds to match the des...
Abstract The fracture properties of graphite produced in China, named as CLG, were studied by performing three-point bending tests on center-notched beams. The load-deflection (P-δ) curves and load-crack mouth opening displacement (P-CMOD) curves of the beams in the entire loading process were obtained. Electronic speckle pattern interferometry (ESPI) technique was used to measure the full-field displacement of the beams. Through analysis on the relationship between the δ and CMOD, the δ-CMOD cu...
#1Yinlong Lu(CUMT: China University of Mining and Technology)H-Index: 6
#2Wenshuai Li(CUMT: China University of Mining and Technology)H-Index: 4
Last. Xiaodong Zhang(CUMT: China University of Mining and Technology)H-Index: 1
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Abstract A new microscale visualization experimental system is proposed for in-situ measurement of microcracking and microdeformation behaviour of macroscopic specimens during real-time loading. A series of three-point bending experiments were conducted on sandstone beam specimens containing a Mode I pre-crack. The newly developed microscopic experimental system and two other traditional experimental techniques, including acoustic emission (AE) monitoring and macroscopic charge coupled device (C...
Last. H.G. Zhang(Guida: Guizhou University)H-Index: 1
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Abstract Three-point bending tests are performed on center-notched graphite beams to study the fracture properties of IG11 graphite. Electronic speckle pattern interferometry (ESPI) is used to measure the full-field deformation of the graphite beams. A clip gauge is used to measure the crack mouth opening displacement (CMOD) of the beams, which validates the ESPI measurements. In addition, finite element (FE) analysis is performed by using the ABAQUS code coupled with the extended FE method to s...
In order to study crack evolution in concrete, Electronic Speckle Pattern Interferometry (ESPI) technique was applied to measure full-field displacement of concrete beam subjected to three-point bending. Basic principles of ESPI technique were introduced. Mid-span deflection and crack mouth opening displacement were measured by linear variable differential transformers (LVDTs) and clip gauge, respectively. Typical load-displacement curves measured by different methods were compared and analyzed....
#1Ali Tarokh(UMN: University of Minnesota)H-Index: 8
#2Roman Y. Makhnenko(UIUC: University of Illinois at Urbana–Champaign)H-Index: 12
Last. Joseph F. Labuz(UMN: University of Minnesota)H-Index: 32
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The zone of microcracks surrounding a notch tip—the process zone—is a phenomenon observed in fracture of quasi-brittle materials, and the characterization of the process zone is the topic of the paper. Specimens of different sizes with a center notch fabricated from a granite of large grain (Rockville granite, average grain size of 10 mm), were tested in three-point bending. Acoustic emissions were recorded and locations of microcracks were determined up to peak load. The results show that both ...
Abstract Laser Speckle Correlation, Electronic Speckle Pattern Interferometry and Digital Holographic interferometry have evolved for decades to become relevant techniques in many fields of today’s wide spectrum of knowledge and disciplines. Indeed, with today׳s advances in optics, photonics, electronics and computing there are many important applications for them and strictly speaking there are an almost infinite number of applications that one can think of, as they are non-contact optical tech...
