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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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TL;DR: In this paper, the authors evaluated the plasticity-induced crack shielding effect during fatigue crack growth using transmission photoelasticity, based on the evaluation of the stress intensity factors calculated from the analysis of the isochromatic fringe patterns observed at the vicinity of a crack tip.
Abstract: The plasticity-induced crack shielding effect is evaluated during fatigue crack growth using transmission photoelasticity. The proposed methodology is based on the evaluation of the stress intensity factors calculated from the analysis of the isochromatic fringe patterns observed at the vicinity of a crack tip. Four different mathematical models describing the crack tip stress fields (namely models based on Westergaard’s, Williams’s, and Muskhelishvili’s equations and a new model called Christopher–James–Patterson) have been employed. Thus, a comparative study to evaluate which of the models is more suitable for fatigue crack shielding evaluation has been performed. A set of fatigue experiments on polycarbonate middle-tension specimens at different R-ratios have been conducted. Experimental results reveal the presence of plasticity-induced crack shielding on growing fatigue cracks for specimens tested at a low R-ratio. In addition, a retardation effect on the fatigue growth rate has been observed due to the shielding effect induced by the plasticity generated both at the crack tip and along the crack flanks. All these results highlight the enormous potential of transmission photoelasticity for the evaluation of plasticity-induced crack shielding on growing fatigue cracks.
7 citations
TL;DR: In this article, a residual stress measurement tool for the bottle blowing industry is presented, which can be used to examine these residual stresses in the sidewalls and bases of bottles, which may be related to the failure characteristics of the bottle bases.
Abstract: Polyethylene Terephthalate (PET) is used in many packaging applications. PET is especially important in the carbonated soft drink industry, where the pressure of carbonation and the imposed and residual stresses in the bottle bases can sometimes lead to cracking, and failures. In the process of bottle blowing, residual stresses are created and remain in the bottle base as a result of the uniaxial and biaxial stretching in these regions. It is advantageous to measure these residual stresses and the mode of stretching, which may be related to the failure characteristics of the bottle bases. Photoelasticity can be used to examine these residual stresses in the sidewalls and bases of bottles. This work reports on a residual stress measurement tool for the bottle blowing industry.
7 citations
TL;DR: In this paper, the effect of contact compression load on the contact stress distribution of the cam profile at the point of contact was studied and analyzed for a pear cam and roller follower mechanism.
Abstract: The problem of this paper is the high contact stress at the point of contact between the cam and the follower. A pear cam and roller follower mechanism were studied and analyzed for different position of the follower and different contact compression load. The objective of this paper is to study the effect of contact compression load on the contact stress distribution of the cam profile at the point of contact. Four different positions of the follower with the cam was considered (0°, 90°, 180°, and 270°). The theory of circular plate was applied to derive the analytic solution of the contact stress. The numerical simulation had been done using ANSYS Ver. 19.2 package to determine the contact stress, while SolidWorks software was used to investigate follower displacement, velocity, and acceleration. Four distinct values of the compression contact load, such as 3.121 N, 6.242 N, 9.364 N, and 12.485 N, were used in the numerical simulation. In the experiment setup, a photo-elastic technique was carried out in the field of polarized light to exhibit the stress distribution on the cam specimen. The annealed PSM-4 backalate material was used in the experiment setup. The experimental value of contact stress was checked and verified analytically and numerically at the point of contact. The innovation in this paper the use of spring-damper system which reduce the value of contact stress at the point of contact. The contact stress was maximum 2.136 MPa when the follower located at 270° with the cam, while the contact stress was minimum 1.802 MPa when the follower located at 180° at compression load 12.485 N.
7 citations
7 citations
TL;DR: In this article, a new adaptive smoothing algorithm is proposed to remove the noise due to isochromatic-isoclinic interaction that automatically takes care of the isotropic points and π jumps present in the ISO phasemap.
Abstract: In digital photoelasticity, one gets whole field information of isoclinic and isochromatic parameters based on intensity processing. Isoclinic values are undefined at isochromatic fringe contours and this appears as noise in the isoclinic phasemap which affects stress separation adversely. A new adaptive smoothing algorithm to remove the noise due to isochromatic-isoclinic interaction that automatically takes care of the isotropic points and π jumps present in the isoclinic phasemap is proposed. It is validated for the benchmark problem of a ring under diametral compression and verified for an angled bracket.
7 citations
Additional excerpts
...Introduction In digital photoelasticity [1], several techniques are available to obtain isoclinic (h) and isochromatic (N) data, pixel by pixel, in a true sense....
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