Electronic speckle pattern interferometry observation of brick–mortar interface behaviour under compressionThis article is one of a selection of papers published in this Special Issue on Masonry.

2007 ◽  
Vol 34 (11) ◽  
pp. 1467-1474 ◽  
Author(s):  
A.T. Vermeltfoort ◽  
D.R.W. Martens ◽  
G.P.A.G. van Zijl
Keyword(s):  
Load Transfer ◽  
Axial Strain ◽  
Speckle Pattern ◽  
Strain Curve ◽  
Companion Paper ◽  
Laser Speckle ◽  
Lateral Strain ◽  
Electronic Speckle Pattern Interferometry ◽  
Brick And Mortar ◽  
Large Material

The brick–mortar interaction is important in the mechanical behaviour of masonry. It affects the load transfer considerably, as shown by detailed deformation measurements taken using electronic speckle pattern interferometry (ESPI), a laser speckle interference technique. A companion paper [Canadian Journal of Civil Engineering, 34(11), 1475 (2007)] by the authors of this paper argues that the joint is the only part of contemporary masonry significantly affected by manual action, which is why large material variations appear at the brick–mortar interface. To evaluate this phenomenon, ESPI measurements were performed and compared with accompanying linear variable differential transformer (LVDT) results. The behaviour of specimens loaded with various eccentricities was relatively soft in the brick–mortar interface area when compared with the behaviour shown in the surrounding stiff brick and mortar. The brick–mortar interface was characterized by a central part surrounded by fissures. Most of the load was transmitted in the central part. Because of this, the axial strain curve over the width of the specimens was U-shaped for concentrically loaded specimens (i.e., those with zero eccentricity). Over the height of the two-brick one-joint specimen, a smooth, B-shaped lateral strain curve was observed, in which the largest strains were found in the bricks.

Recent developments and applications in electronic speckle pattern interferometry

1998 ◽  
Vol 33 (2) ◽  
pp. 153-169 ◽  
Author(s):  
J N Petzing ◽  
J R Tyrer
Keyword(s):  
Speckle Pattern ◽  
Laser Speckle ◽  
Optical Metrology ◽  
Electronic Speckle Pattern Interferometry ◽  
Optical Technology ◽  
Engineering Applications ◽  
Recent Developments ◽  
Potential Applicability ◽  
Future Direction ◽  
Near Future

Electronic 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 into the interferometers, allowing further optimization and extending the potential applicability of the technique. This review considers the most notable developments of interferometer design and application that have occurred and been widely published during the 1990s, and examines the current and near-future direction of research into the technique.

scholarly journals Peripapillary and Posterior Scleral Mechanics—Part II: Experimental and Inverse Finite Element Characterization

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Michaël J. A. Girard ◽  
J. Crawford Downs ◽  
Michael Bottlang ◽  
Claude F. Burgoyne ◽  
J.-K. Francis Suh
Keyword(s):  
Finite Element ◽  
Optic Nerve ◽  
Constitutive Model ◽  
Optic Nerve Head ◽  
Speckle Pattern ◽  
Companion Paper ◽  
Tangent Modulus ◽  
Electronic Speckle Pattern Interferometry ◽  
Model Parameters ◽  
Scleral Shell

The posterior sclera likely plays an important role in the development of glaucoma, and accurate characterization of its mechanical properties is needed to understand its impact on the more delicate optic nerve head—the primary site of damage in the disease. The posterior scleral shells from both eyes of one rhesus monkey were individually mounted on a custom-built pressurization apparatus. Intraocular pressure was incrementally increased from 5 mm Hg to 45 mm Hg, and the 3D displacements were measured using electronic speckle pattern interferometry. Finite element meshes of each posterior scleral shell were reconstructed from data generated by a 3D digitizer arm (shape) and a 20 MHz ultrasound transducer (thickness). An anisotropic hyperelastic constitutive model described in a companion paper (Girard, Downs, Burgoyne, and Suh, 2009, “Peripapillary and Posterior Scleral Mechanics—Part I: Development of an Anisotropic Hyperelastic Constitutive Model,” ASME J. Biomech. Eng., 131, p. 051011), which includes stretch-induced stiffening and multidirectional alignment of the collagen fibers, was applied to each reconstructed mesh. Surface node displacements of each model were fitted to the experimental displacements using an inverse finite element method, which estimated a unique set of 13 model parameters. The predictions of the proposed constitutive model matched the 3D experimental displacements well. In both eyes, the tangent modulus increased dramatically with IOP, which indicates that the sclera is mechanically nonlinear. The sclera adjacent to the optic nerve head, known as the peripapillary sclera, was thickest and exhibited the lowest tangent modulus, which might have contributed to the uniform distribution of the structural stiffness for each entire scleral shell. Posterior scleral deformation following acute IOP elevations appears to be nonlinear and governed by the underlying scleral collagen microstructure as predicted by finite element modeling. The method is currently being used to characterize posterior scleral mechanics in normal (young and old), early, and moderately glaucomatous monkey eyes.

Damage Detection Based on ESPI and SVM

2006 ◽  
Vol 324-325 ◽  
pp. 1309-1312
Author(s):  
Long Liu ◽  
Guang Meng ◽  
Hai Huang
Keyword(s):  
Damage Detection ◽  
Learning Algorithm ◽  
Speckle Pattern ◽  
Element Model ◽  
Measuring Method ◽  
Laser Speckle ◽  
Electronic Speckle Pattern Interferometry ◽  
Support Vector ◽  
Fringe Patterns ◽  
Precision Of Processing

An approach of damage detection based on ESPI and SVM is proposed. ESPI (Electronic Speckle Pattern Interferometry) is a non-contacting measuring method, which can measure the small static and dynamitic surface deformations and reveal the flaws by looking for flaw-induced deformation anomalies. Support Vector Machine (SVM) is a machine learning algorithm based on statistical learning theory, and it has recently been established as a powerful tool for classification and regression problems. To develop the precision of processing the pattern fringe data, the SVM is introduced to process the patterns corrupted by the laser speckle effect. The SVM is trained with fringe patterns generated from a finite element model and a simple model of the laser speckle effect. The output pattern is obtained to flag whether the damage exists or not. The trained SVM is tested for robustness with model generated test patterns of a flat plate. The results show that this approach is a promising and effective for damage detection.

Thermal strain analysis of composite materials by electronic speckle pattern interferometry

2000 ◽  
Vol 14 (5) ◽  
pp. 477-482 ◽  
Author(s):  
Koung Suk Kim ◽  
Wan Shik Jang ◽  
Myung Seak Hong ◽  
Ki Soo Kang ◽  
Hyun Chul Jung ◽  
...  
Keyword(s):  
Composite Materials ◽  
Speckle Pattern ◽  
Thermal Strain ◽  
Strain Analysis ◽  
Electronic Speckle Pattern Interferometry
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