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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 article, a 3D systematic relationship of transmissivity with stress and wavelength was established by analyzing the periodic extinction phenomenon of isochromatic fringe pattern obtained from white light photoelasticity.
Abstract: To face the increasing demand of residual stress measurement in many hi-tech industries, the integration of photoelasticity and advanced image acquisition equipment is a natural trend. With the integration of photoelasticity and spectrometry, the measurement capability of low-level stress and the stress in low birefringence materials can be enhanced. In fact, there is a significant correlation between the stress level and transmissivity spectrum. The key of the stress measurement method proposed in this paper is to find this scarcely explored correlation. By analyzing the periodic extinction phenomenon of isochromatic fringe pattern obtained from white light photoelasticity and the equation of transmissivity spectrum expressed in stress and wavelength, a three-dimensional (3D) systematic relationship of transmissivity with stress and wavelength can be established. By applying the 3D systematic transmissivity with stress and wavelength, the stress value can be determined directly from the transmissivity of the light transmitted through the polariscope. Moreover, when the proposed method is employed, the required parameters can be directly obtained from the database. There is no need to know the wavelength-dependent stress-optic coefficient beforehand. Glass, a very low birefringence material, was used to confirm the feasibility of the proposed method. Two regression approaches to search the transmissivity extremities were attempted to find the optimum systematic relationship.
9 citations
TL;DR: In this paper, a novel experimental configuration is presented which simultaneously applies radial and axial ball bearing loads on a bearing housing into which an assembled photoelastic model of the bearing is mounted.
Abstract: Although stress analysis of the bearing contact problem has been a subject of significant interest, it is rare to find experimental studies on the topic. The problem is attributed to the difficulty in designing an experimental system, which can apply radial and axial loads and permit direct measurement of the bearing contact stresses. A novel experimental configuration is presented which simultaneously applies radial and axial ball bearing loads on a bearing housing into which an assembled photoelastic model of the bearing is mounted. The technique is demonstrated and validated by measuring contact stresses of angular contact ball bearings using the “frozen stress” photoelastic experimental hybrid method (PEHM). Experimental results reveal that ball deformations are mainly concentrated at the contact points. Ball 0, positioned at the base of the bearing housing, experienced the highest magnitude of stresses located near the geometric center of the contact region. Stresses are observed to progressively decrease with increased distance from ball 0 along the circular bearing groove toward balls 4 L and 4R (near the three and nine o-clock positions) where the lowest stress magnitudes were observed. It was also shown that the most highly loaded balls were located in the lower semi-circular section. PEHM measurements are found to be in very good agreement with finite element analysis.
9 citations
TL;DR: In this paper, a new digital photoelastic method based on phase shifting using monochromatic light source is presented It provides full field values of isoclinics (θ) and isochromatics (N) in a true sense among the several methods available for data acquisition, phase shifting / polarization stepping techniques are most widely used for their simplicity and accuracy
Abstract: Photoelasticity is one of the most widely used techniques for experimental stress and strain analysis With the availability of low cost digital image processing systems, a separate branch of photoelasticity known as digital photoelasticity came into existence providing whole-field values of the isoclinics (θ) and isochromatics (N) in a true sense Among the several methods available for data acquisition, phase shifting / polarization stepping techniques are most widely used for their simplicity and accuracy In this paper a new digital photoelastic method based on phase shifting using monochromatic light source is presented It provides full field values of θ and N The arrangement is carefully chosen with the intention of reducing the influence of quarter wave mismatch error in the evaluation of θ and N The methodology is validated for the benchmark problem of a disk under diametral compression
9 citations
Cites background or methods from "Digital Photoelasticity: Advanced T..."
...Several techniques are available for data acquisition in digital photoelasticity [1]....
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...Reference [1] recommends that θc and δc are to be evaluated by atan2 () function....
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...The intensity equations for various optical arrangements are derived using Jones calculus [1]....
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...This is termed as ambiguity in the isoclinic phase map [1]....
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...These techniques can be broadly classified into polarization stepping, phase shifting, load stepping and Fourier transform approach [1]....
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TL;DR: In this paper, a phase-field fracture propagation model was developed to characterize the material failure mechanisms that play a significant role during the shale maturation process, and the numerical model consists of coupled solid deformation, pore pressure, and fracture propagation mechanisms.
Abstract: The emergence of hydrocarbons within shale as a major recoverable resource has sparked interest in fluid transport through these tight mudstones. Recent studies suggest the importance to recovery of microfracture networks that connect localized zones with large organic content to the inorganic matrix. This paper presents a joint modeling and experimental study to examine the onset, formation, and evolution of microfracture networks as shale matures. Both the stress field and fractures are simulated and imaged. A novel laboratory-scale, phase-field fracture propagation model was developed to characterize the material failure mechanisms that play a significant role during the shale maturation process. The numerical model developed consists of coupled solid deformation, pore pressure, and fracture propagation mechanisms. Benchmark tests were conducted to validate model accuracy. Laboratory-grade gelatins with varying Young’s modulus were used as scaled-rock analogs in a two-dimensional Hele-Shaw cell apparatus. Yeast within the gelatin generates gas in a fashion analogous to hydrocarbon formation as shale matures. These setups allow study and visualization of host rock elastic-brittle fracture and fracture network propagation mechanisms. The experimental setup was fitted to utilize photoelasticity principles coupled with birefringence properties of gelatin to explore visually the stress field of the gelatin as the fracture network developed. Stress optics image analysis and linear elastic fracture mechanics (LEFM) principles for crack propagation were used to monitor fracture growth for each gelatin type. Observed and simulated responses suggest gas diffusion within and deformation of the gelatin matrix as predominant mechanisms for energy dissipation depending on gelatin strength. LEFM, an experimental estimation of principal stress development with fracture growth, at different stages was determined for each gelatin rheology. The interplay of gas diffusion and material deformation determines the resulting frequency and pattern of fractures. Results correlate with Young’s modulus. Experimental and computed stress fields reveal that fractures resulting from internal gas generation are similar to, but not identical to, type 1 opening mode.
9 citations
Cites methods from "Digital Photoelasticity: Advanced T..."
...The optical principles and functional description of the polariscope are well described in the literature (Anderson 1978; Phillips 2008; Ramesh 2000; Li 2010; Baek et al. 2014; and Ju et al. 2017) and are not the focus of this work....
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TL;DR: In this article, the strain intensity factor at the tip of a rigid line inclusion, embedded in an isotropic matrix, is studied using analytical and numerical techniques, which is appropriate for quantifying the magnitude of singularities at the inclusion tip.
9 citations