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Digital Photoelasticity: Advanced Techniques and Applications
01 Jan 2000-
TL;DR: In this article, phase shifting, Polarization Stepping and Fourier Transform Methods are used for phase unwrapping and Optically Enhanced Tiling in digital photoelasticity.
Abstract: Transmission Photoelasticity.- Reflection Photoelasticity.- Digital Image Processing.- Fringe Multiplication.- Fringe Thinning and Fringe Clustering.- Phase Shifting, Polarization Stepping and Fourier Transform Methods.- Phase Unwrapping and Optically Enhanced Tiling in Digital Photoelasticity.- Colour Image Processing Techniques.- Evaluation of Contact Stress Parameters and Fracture Parameters.- Stress Separation Techniques.- Fusion of Digital Photoelasticity, Rapid Prototyping and Rapid Tooling Technologies.- Recent Developments and Future Trends.
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01 Apr 2011
TL;DR: In this article, a compact, phasemultiplied, circular polariscope and series interferometer arrangement is developed for high-resolution, full-field stress measurement in single======crystals with weak piezo-optical coefficients.
Abstract: A compact, phase-multiplied, circular polariscope
and series interferometer arrangement is developed
for high-resolution, full-field stress measurement in single
crystals with weak piezo-optical coefficients. We present a
general stress-optic law, derived from anisotropic piezooptical
constitutive relations, which provides the theoretical
framework for obtaining stress field components from
measured optical isoclinic, isochromatic and isopachic
phase maps. A new phase image processing technique is
also developed, which combines data obtained from
different interference configurations for the successful
removal of low-modulation zones within isoclinic and
isopachic phase maps. The validity and accuracy of the
proposed interferometer arrangement and stress measurement
methodology are demonstrated through a compression
test of a c-cut single crystal sapphire plate loaded by a
cylindrical indenter.
6 citations
Cites methods from "Digital Photoelasticity: Advanced T..."
...A widely use numerical approach is the shear difference method [ 19 , 20], which allows for stress separation by integrating one of the equilibrium equations on a line-byline basis....
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TL;DR: In this article, the integrated phase shifting technique (IPST) can real-time analyze the photoelastic parameters at a video rate of the high speed CCD camera, and fourteen algorithms are described by different configurations of the rotating an analyzer at a constant rate and an output quarter-wave plate at another constant rate.
6 citations
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TL;DR: In this paper, a microsecond controlled blasting case involved with the interactions between blast waves and an opposite propagating crack is studied using dynamic photoelasticity method, and the results show that the stress waves influence the local stress field of dynamic crack tip, and alter the crack propagation behavior.
6 citations
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TL;DR: In this paper, a PID closed-loop frequency difference controlling system based on the piezoelectric transducer is proposed and realized for the Nd:YAG dual-frequency solid-state microchip laser with stable and adjustable frequency difference.
Abstract: Dual-frequency solid-state microchip lasers have advantages, such as large frequency differences, high pumping efficiency, high beam quality, and narrow laser linewidth. In addition, they are characterized by simplicity, compactness, stability, long lifetime, etc. However, the frequency difference of the dual-frequency solid-state microchip laser cannot be modulated and is only determined by its internal stress. The stress distribution inside the microchip laser is uneven and the stability of the frequency difference needs to be improved furthermore, which limits its applications. The structure of a Nd:YAG laser resonator, the mechanism of dual-frequency generation, and the output characteristics are studied. The relationship between the polarization direction of the pumping laser and the intensities of the dual-frequency components is theoretically and experimentally researched, realizing the maximum amplitude of the beat signal. Based on the photoelasticity theory, the relationship between the frequency difference and the external force is analyzed and the PID closed-loop frequency difference controlling system based on the piezoelectric transducer is proposed and realized. By applying the closed-loop control, the frequency difference of the Nd:YAG laser can be continuously modulated in the range from 24 to 30 MHz and the fluctuation is less than 450 kHz. The high-performance Nd:YAG dual-frequency solid-state microchip laser with stable and adjustable frequency difference is achieved.
6 citations
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01 Mar 2017TL;DR: In this paper, the authors show that the zerstorungsfrei prufende, flachenformige methodik der Polarisationsoptik zur objektiven Bewertung geeignet ist Hierbei werden zum einen die vollflachige Visualisierung and Erforschung der Anisotropien an vorgespannten Glasscheiben prasentiert sowie the Entwicklung neuer Messmethoden fur die bestimmung der
Abstract: Bei den seit Jahren mit Erfolg eingesetzten Glasprodukten ESG und TVG gibt es in der Praxis haufig Streitigkeiten aufgrund von Anisotropien (Doppelbrechungen, die zu sichtbaren farbigen Effekten fuhren) Erkenntnisse aus Schadensfallen und Forschungsergebnisse zeigen, dass Anisotropien unter verschiedenen Aspekten beurteilt werden mussen und dass es zwingend notwendig ist, diese mit geeigneten Prufmethoden zu bewerten In diesem Beitrag zeigen die RWTH Aachen und die HS Munchen, dass die zerstorungsfrei prufende, flachenformige Methodik der Polarisationsoptik zur objektiven Bewertung geeignet ist Hierbei werden zum einen die vollflachige Visualisierung und Erforschung der Anisotropien an vorgespannten Glasscheiben prasentiert sowie die Entwicklung neuer Messmethoden fur die Bestimmung der Kantenmembranspannung dargelegt
6 citations
Cites background from "Digital Photoelasticity: Advanced T..."
...Die hier beschriebenen Analyseverfahren basieren auf den Grundlagen zur Ermittlung der Isochromatenordnung aus den Isochromatenbildern mittels Computeralgorithmen, welche in [10] beschrieben sind....
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