scholarly journals Sequential-Digital Image Correlation for Mapping Human Posterior Sclera and Optic Nerve Head Deformation

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Jeffrey D. Pyne ◽  
Katia Genovese ◽  
Luciana Casaletto ◽  
Jonathan P. Vande Geest
Keyword(s):  
Optic Nerve ◽  
Digital Image Correlation ◽  
Optic Nerve Head ◽  
Digital Image ◽  
Complex Geometry ◽  
Open Angle Glaucoma ◽  
Image Correlation ◽  
Optical Methods ◽  
Retinal Ganglion ◽  
Position Measurement

Optic nerve head (ONH) deformations may be involved in the onset or further development of glaucoma, including in patients with relatively normal intraocular pressures (IOPs). Characterizing posterior scleral deformations over physiological pressures may provide a better understanding of how changes in IOP lead to changes in the mechanical environment of the ONH and possibly retinal ganglion cell death. Pressure inflation measurement test protocols are commonly used to measure deformation of the peripapillary sclera with full-field noncontact optical methods. The purpose of this work was to develop and validate a new sequential 3D digital image correlation (S-DIC) approach for quantification of posterior scleral pressure induced deformation that improves z (in-depth) resolution of the DIC measurement without losing in-plane sensitivity, while also being able to contour and map deformations of the complex-shaped ONH. Our approach combines two orthogonal axes of parallax with standard 3D DIC methods using a single high-resolution camera. The enhanced capabilities of S-DIC with respect to standard 3D DIC has been demonstrated by carrying out a complete benchmark for shape, deformation, and strain measurement on an object of known complex geometry. Our S-DIC method provided a reconstruction accuracy of 0.17% and an uncertainty in z-position measurement of 8 μm. The developed methodology has also been applied to a human posterior scleral shell, including the full peripapillary sclera and optic nerve. The relatively inexpensive S-DIC approach may provide new information on the biomechanical deformations of the optic nerve head and, thus, the death of retinal ganglion cells in primary open angle glaucoma.

scholarly journals Application of 3D Digital Image Correlation for Development and Validation of FEM Model of Self-Supporting Arch Structures

2019 ◽  
Vol 9 (7) ◽  
pp. 1305 ◽  
Author(s):  
Krzysztof Malowany ◽  
Artur Piekarczuk ◽  
Marcin Malesa ◽  
Małgorzata Kujawińska ◽  
Przemysław Więch
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Complex Geometry ◽  
Image Correlation ◽  
Building Structures ◽  
Local Loss ◽  
Steel Sheets ◽  
3D Digital Image Correlation ◽  
Arch Structures ◽  
Development And Validation

Many building structures, due to a complex geometry and non-linear material properties, are cumbersome to analyze with finite element method (FEM). A good example is a self-supporting arch-shaped steel sheets. Considering the uncommon geometry and material profile of an arch (due to plastic deformations, cross section of a trough, a goffer pattern), the local loss of stability can occur in unexpected regions. Therefore, the hybrid experimental-numerical methodology of analysis and optimization of arch structures have been proposed. The methodology is based on three steps of development and validation of a FEM with utilization of a digital image correlation (DIC) method. The experiments are performed by means of 3D DIC systems adopted sequentially for each measurement step conditions from small size sections, through few segment constructions up to full scale in situ objects.

scholarly journals Investigation by Digital Image Correlation of Mixed-Mode I and II Fracture Behavior of Polymeric IASCB Specimens with Additive Manufactured Crack-Like Notch

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1084
Author(s):  
Tommaso Maria Brugo ◽  
Ivo Campione ◽  
Giangiacomo Minak
Keyword(s):  
Additive Manufacturing ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Complex Geometry ◽  
Selective Laser Sintering ◽  
Fem Analysis ◽  
Image Correlation ◽  
Mode I ◽  
Plastic Behavior ◽  
J Integral

In this work, the fracture mechanics properties of polyamide (PA) specimens manufactured by the selective laser sintering (SLS) technology are investigated, in which an embedded crack-like notch was inserted in the design and produced during the additive manufacturing (AM) phase. To cover a wide variety of mode I/II mixity levels, the inclined asymmetrical semicircular specimen subjected to three points loading (IASCB) was employed. The investigation was carried out by analyzing the full displacement field in the proximity of the crack tip by means of the digital image correlation (DIC) technique. To characterize the material, which exhibits a marked elastic-plastic behavior, the quantity J-integral was evaluated by two different methods: the first one exploits the full fields measured by the DIC, whereas the second one exploits the experimental load–displacement curves along with FEM analysis. The DIC methodology was experimentally validated and proposed as an alternative method to evaluate the J-integral. It is especially suited for conditions in which it is not possible to use the conventional LDC method due to complex and possibly unknown loading conditions. Furthermore, results showed that the AM technique could be used effectively to induce cracks in this type of material. These two aspects together can lead to both a simplification of the fracture characterization process and to the possibility of dealing with a wider number of practical, real-world scenarios. Indeed, because of the nature of the additive manufacturing process, AM crack-like notches can be sintered even having complex geometry, being three-dimensional and/or inside the tested structure.

scholarly journals The Use of Optical Methods in the Analysis of the Areas with Stress Concentration

2018 ◽  
Vol 68 (2) ◽  
pp. 61-76 ◽  
Author(s):  
Miroslav Pástor ◽  
Peter Frankovský ◽  
Martin Hagara ◽  
Pavol Lengvarský
Keyword(s):  
Stress Concentration ◽  
Digital Image Correlation ◽  
Mechanical Stress ◽  
Digital Image ◽  
Image Correlation ◽  
Optical Methods ◽  
Stress Fields ◽  
Plane Model ◽  
Technical Systems

AbstractAnchoring parts of technical systems are often damaged due to the heavy forces acting on these systems during their operation. For that reason, various modifications are suggested and created on the anchoring screws, which should help to reduce the mechanical stress values in a place of the first load-bearing thread of a female screw. For the determination of stress fields on the surface of a plane model of a threaded joint, two non-contact optical methods were used – conventional transmission photoelasticimetry and modern digital image correlation.

scholarly journals Application of the digital image correlation method in the study of cohesive coarse soil deformations

2018 ◽  
Vol 36 ◽  
pp. 03003 ◽  
Author(s):  
Janusz P. Kogut ◽  
Marcin Tekieli
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Optical Method ◽  
Correlation Method ◽  
Test Sample ◽  
Image Correlation ◽  
Optical Methods ◽  
Accurate Information ◽  
Full Field ◽  
Coarse Soil

Non-contact video measurement methods are used to extend the capabilities of standard measurement systems, based on strain gauges or accelerometers. In most cases, they are able to provide more accurate information about the material or construction being tested than traditional sensors, while maintaining a high resolution and measurement stability. With the use of optical methods, it is possible to generate a full field of displacement on the surface of the test sample. The displacement value is the basic (primary) value determined using optical methods, and it is possible to determine the size of the derivative in the form of a sample deformation. This paper presents the application of a non-contact optical method to investigate the deformation of coarse soil material. For this type of soil, it is particularly difficult to obtain basic strength parameters. The use of a non-contact optical method, followed by a digital image correlation (DIC) study of the sample obtained during the tests, effectively completes the description of the behaviour of this type of material.

The Knowledge Acquired by Using of Optical Methods by Strain Fields Investigation

2013 ◽  
Vol 486 ◽  
pp. 141-146
Author(s):  
Martin Hagara ◽  
František Šimčák ◽  
Matúš Kalina
Keyword(s):  
Experimental Investigation ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Speckle Pattern ◽  
Image Correlation ◽  
Optical Methods ◽  
Optical Systems ◽  
Electronic Speckle Pattern Interferometry ◽  
Strain Fields ◽  
Pros And Cons

These days are preferably used contactless optical methods for experimental investigation of strains and displacements, which give some information on whole investigated surface. In this contribution the optical systems working on electronic speckle pattern interferometry (ESPI) principle and digital image correlation (DIC) method are described. By using of ESPI and DIC methods the displacements and strains fields on chosen types of specimens are determined. Pros and cons of particular methods and influence of various factors on reached results accuracy are compared. There are also mentioned the possibilities of using of optical methods in application of devices on authors department.

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