Determination of Principal-Stress Directions by Three-Step Color Phase Shifting Technique

2006 ◽  
Vol 321-323 ◽  
pp. 1284-1287
Author(s):  
Pichet Pinit ◽  
Tobita Susumu ◽  
Eisaku Umezaki
Keyword(s):  
Principal Stress ◽  
White Light ◽  
Digital Camera ◽  
Circular Disk ◽  
Dark Field ◽  
Phase Shifting ◽  
Automatic Determination ◽  
Stress Directions ◽  
Field Plane

A three-step phase shifting approach for automatic determination of the isoclinic parameter in photoelasticity is presented. Unreliable isoclinic values affected by the isochromatic parameter are solved using the white light. The method uses three fringe images digitally captured by a digital camera for three different configurations of the dark-field plane polariscope. For a circular disk under compression, results show the method permits the isoclinic parameter in the range -π/2 to π/2 with almost free of the isochromatic parameter and comparable with theory.

Application of Determination of Principal-Stress Directions by Color Phase Shifting Technique to Model Containing Isotropic Points

2006 ◽  
Vol 326-328 ◽  
pp. 75-78
Author(s):  
Pichet Pinit ◽  
Eisaku Umezaki
Keyword(s):  
Principal Stress ◽  
Circular Ring ◽  
Binary Image ◽  
Phase Shifting ◽  
Entire Domain ◽  
Diametral Compression ◽  
Phase Shifting Technique ◽  
Stress Directions ◽  
Intersection Operation

This paper presents an application of a new point-wise technique for unwrapping the isoclinic parameter determined by a four-step color phase shifting. The unwrapping technique is based on a largest region in a binary image that corresponds to a largest visible-wrapped period of the computed isoclinic parameter. The largest region is obtained using an intersection operation between the extended ranges of the computed isoclinic parameter. The method uses four raw photoelastic fringe images. The technique is applied to a circular ring containing isotropic points subjected to diametral compression. Results show the method provides the correct isoclinic parameter in the true interval over the entire domain.

Determination of In-Situ Stresses From Hydraulically Fractured Spherical Cavities

1983 ◽  
Vol 105 (2) ◽  
pp. 125-127 ◽  
Author(s):  
W. E. Warren
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Spherical Cavity ◽  
Hydraulic Fractures ◽  
Stress Measurements ◽  
In Situ Stresses ◽  
Spherical Cavities ◽  
Stress Directions

Several problems in analysis can arise in estimating in-situ stresses from standard hydraulic fracturing operations if the borehole is not aligned with one of the principal stress directions. In these nonaligned situations, the possibility of fracturing a spherical cavity for estimating the in-situ stresses is investigated. The theory utilizes all the advantages of direct stress measurements associated with hydraulic fracturing and eliminates the geometrical problems associated with the analysis of hydraulic fractures in cylindrical boreholes.

scholarly journals METHODOLOGY FOR AUTOMATIC DETERMINATION OF CONTRAST OF LASER MARKING FOR DIFFERENT MATERIALS

2019 ◽  
Vol 3 ◽  
pp. 134
Author(s):  
Lyubomir Lazov ◽  
Edmunds Teirumnieks ◽  
Nikolay Angelov ◽  
Erika Teirumnieka
Keyword(s):  
Laser System ◽  
Digital Camera ◽  
Test Field ◽  
Automatic Determination ◽  
Technological Parameters ◽  
Test Analysis ◽  
Laser Marking ◽  
Different Types

A new methodology for determining and optimizing the contrast of the technological laser marking process has been developed. It can evaluate the quality of the markings regardless of the type of material and the type of laser system. To perform the test analysis, a specialized test field is programmed, which including the change of two of the main parameters influencing the marking process: the linear energy density (LED) and the linear density of the pulses (LDI). Marking of a test field consisting of squares of a certain size is done by means of a raster marking method with a constant step between the lines. The results are processed with a digital camera and specialized software. The maximum blackening is compared with the background of all fields and is juxtaposed with the effective energy needed to obtain a certain contrast. Several consecutive iterations are made, with each of the following experiments excluding the variants with least contrast. Thus, the study consistently brings the result to a minimum working area of the basic technological parameters, providing the user's desired contrast of the marking. The developed author's method of automatically determining the contrast of the laser marking reduces the time for preliminary experimental research and gives a reliable and subjectively absent way of qualitatively marking different types of industrial products.

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