Investigation of Fringe Pattern Distribution in Circular Disk by Reflection Polariscope Technique

2016 ◽  
Vol 848 ◽  
pp. 68-71
Author(s):  
Yongyut Manjit ◽  
Saksit Sukprasong ◽  
Apichart Limpichaipanit ◽  
Athipong Ngamjarurojana
Keyword(s):  
Stress Distribution ◽  
Fringe Pattern ◽  
Digital Camera ◽  
Circular Disk ◽  
Transparent Material ◽  
Isochromatic Fringe ◽  
Pattern Distribution ◽  
Fringe Patterns

In this study, the fringe pattern distribution of various loads on circular disk of homogeneous acrylic in different thicknesses by using reflection polariscope technique was carried out. The load was pressed at the top and the bottom to produce the fringe patterns, which were recorded by digital camera. Then the results were analyzed. The number of isochromatic fringe pattern depends on the magnitude of force acting on the circular disk and these relation is linearly. The application of these research is used to predict stress distribution on the transparent material in the case of different dimension of the circular disk shape.

Study of Stress Distribution in Homogeneous Plastic by Photoelastic Analysis System

2016 ◽  
Vol 675-676 ◽  
pp. 708-711 ◽  
Author(s):  
Yongyut Manjit ◽  
Saksit Sukprasong ◽  
Apichart Limpichaipanit ◽  
Athipong Ngamjarurojana
Keyword(s):  
Stress Distribution ◽  
Fringe Pattern ◽  
Digital Camera ◽  
Circular Disk ◽  
Dark Field ◽  
Bright Field ◽  
Photoelastic Analysis ◽  
Fringe Patterns ◽  
Analysis System

The experiment was conducted to study the stress distribution on a homogeneous plastic using photoelastic analysis system where the stress was observed by reflection polariscope. The circular disk of homogeneous plastic was used for study in this research. The sample was pressed at the top and bottom. The fringe patterns were produced from sample on the model being stressed, which could be observed in the bright field and dark field. The fringe patterns were recorded by digital camera. Then the results were analyzed; the fringe pattern looked different when applying various magnitudes of force because the stress distribution in sample was changed in homogeneous plastic.

scholarly journals Single-shot detection of 8 unique monochrome fringe patterns representing 4 distinct directions via multispectral fringe projection profilometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Parsa Omidi ◽  
Mohamadreza Najiminaini ◽  
Mamadou Diop ◽  
Jeffrey J. L. Carson
Keyword(s):  
Spatial Resolution ◽  
Fringe Pattern ◽  
Three Dimensional ◽  
Fringe Projection ◽  
Video Frame ◽  
Single Shot ◽  
Shot Detection ◽  
Fringe Patterns ◽  
Fringe Projection Profilometry ◽  
Multispectral Camera

AbstractSpatial resolution in three-dimensional fringe projection profilometry is determined in large part by the number and spacing of fringes projected onto an object. Due to the intensity-based nature of fringe projection profilometry, fringe patterns must be generated in succession, which is time-consuming. As a result, the surface features of highly dynamic objects are difficult to measure. Here, we introduce multispectral fringe projection profilometry, a novel method that utilizes multispectral illumination to project a multispectral fringe pattern onto an object combined with a multispectral camera to detect the deformation of the fringe patterns due to the object. The multispectral camera enables the detection of 8 unique monochrome fringe patterns representing 4 distinct directions in a single snapshot. Furthermore, for each direction, the camera detects two π-phase shifted fringe patterns. Each pair of fringe patterns can be differenced to generate a differential fringe pattern that corrects for illumination offsets and mitigates the effects of glare from highly reflective surfaces. The new multispectral method solves many practical problems related to conventional fringe projection profilometry and doubles the effective spatial resolution. The method is suitable for high-quality fast 3D profilometry at video frame rates.

scholarly journals Experimental determination and finite element analysis of coefficients of the multi-parameter Williams series expansion in the vicinity of the crack tip in linear elastic materials. Part I

2020 ◽  
pp. 237-249
Author(s):  
L. V Stepanova
Keyword(s):  
Series Expansion ◽  
Digital Image ◽  
Power Series Expansion ◽  
Crack Tip ◽  
Higher Order ◽  
Accurate Estimation ◽  
Principal Stresses ◽  
Isochromatic Fringe ◽  
Higher Order Terms ◽  
Fringe Patterns

This study aims at obtaining coefficients of the multi-parameter Williams series expansion for the stress field in the vicinity of the central crack in the rectangular plate and in the semi-circular notched disk under bending by the use of the digital photoelasticity method. The higher-order terms in the Williams asymptotic expansion are retained. It allows us to give a more accurate estimation of the near-crack-tip stress, strain and displacement fields and extend the domain of validity for the Williams power series expansion. The program is specially developed for the interpretation and processing of experimental data from the phototelasticity experiments. By means of the developed tool, the fringe patterns that contain the whole field stress information in terms of the difference in principal stresses (isochromatics) are captured as a digital image, which is processed for quantitative evaluations. The developed tool allows us to find points that belong to isochromatic fringes with the minimal light intensity. The digital image processing with the aid of the developed tool is performed. The points determined with the adopted tool are used further for the calculations of the stress intensity factor, T-stresses and coefficients of higher-order terms in the Williams series expansion. The iterative procedure of the over-deterministic method is utilized to find the higher order terms of the Williams series expansion. The procedure is based on the consistent correction of the coefficients of the Williams series expansion. The first fifteen coefficients are obtained. The experimentally obtained coefficients are used for the reconstruction of the isochromatic fringe pattern in the vicinity of the crack tip. The comparison of the theoretically reconstructed and experimental isochromatic fringe patterns shows that the coefficients of the Williams series expansion have a good match.

Developments in the Application of the Grid Method to Dynamic Problems

1959 ◽  
Vol 26 (4) ◽  
pp. 629-634
Author(s):  
A. J. Durelli ◽  
J. W. Dally ◽  
W. F. Riley
Keyword(s):  
Dynamic Stress ◽  
Grid Method ◽  
Circular Disk ◽  
Model Material ◽  
Dynamic Problems ◽  
Principal Stresses ◽  
Stress Studies ◽  
Low Modulus ◽  
Fringe Patterns ◽  
Dynamic Loading Conditions

Abstract The objective of the research reported in this paper was to develop the grid method further for use in dynamic-stress studies. A rubber-thread grid network in a low-modulus model material (a urethane rubber known as Hysol 8705) was used in conjunction with a microflash light source to record grid distortions and photoelastic fringe patterns in a model subjected to dynamic-loading conditions. By considering a strut subjected to axial impact it was possible to establish that the static and dynamic values of Poisson’s ratio were identical, and the strain-fringe value of the material varied with strain rate. In addition, stresses in the axial and transverse directions were determined along the center line of the strut. Finally, the methods established were applied to the problem of a circular disk subjected to diametrical impact and both principal stresses were determined along a vertical diameter at one instant during impact.

Photoelasticity and Aircraft Design

1951 ◽  
Vol 3 (3) ◽  
pp. 161-172 ◽  
Author(s):  
H.T. Jessop ◽  
C. Snell
Keyword(s):  
Stress Distribution ◽  
Aircraft Design ◽  
Two Dimensional ◽  
Laboratory Technique ◽  
Fringe Patterns ◽  
Practicable Method

It is now more than 25 years since Coker and Filon first developed photoelasticity as a practicable method of exploring the stress distribution in certain types of engineering components. All engineers must be familiar with the striking photographs of fringe patterns obtained by their method in stressed plates of various shapes viewed in a polariscope. In those early days observations were made on Xylonite models and the method was only applicable to components in which stress distribution was of a two-dimensional type. Moreover, with the apparatus then available investigations were somewhat difficult and many engineers at that time were very distrustful of the results obtained from what was, to them, a little understood laboratory technique.

Multi-Frequency Heterodyne Phase Shift Technology in 3-D Measurement

2013 ◽  
Vol 774-776 ◽  
pp. 1582-1585 ◽  
Author(s):  
Le Wang ◽  
Lei Song ◽  
Li Jun Zhong ◽  
Peng Xin ◽  
Shuai Li ◽  
...  
Keyword(s):  
Phase Shift ◽  
Small Area ◽  
Fringe Pattern ◽  
Measurement Accuracy ◽  
High Efficiency ◽  
Median Filter ◽  
Distinct Advantage ◽  
Accuracy Measurement ◽  
Fringe Patterns ◽  
Spin Filtering

According to the characteristics of the fringe patterns noise, came up with a small area spin filtering noise cancellation algorithm based on parallel marker technology. It means that preprocess the fringe pattern before spin filtering, then did a median filter and calculated the stripe direction, finally used the extract the fringe direction to spin filtering of the original image. The algorithm can marked several targets in scanning process at the same time. So it has a high efficiency. The algorithm can be used in the multi-frequency heterodyne phase shift technology .And we can use the technology to complete the measurement of complex surfaces. Experimental results show that the method has a distinct advantage in measurement accuracy, measurement speed, and noise immunity.

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