Determination of strains in photoelastic coatings

Durelli, A. J.; Rajaiah, K.

doi:10.1007/bf02321035

Cited by 10 publications

(3 citation statements)

References 3 publications

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“…There is a known differential electron-projection method for measuring the shape of the surface of an object, the essence of which is to project a reference grid synthesized in a computer, which is an alternation of dark and light stripes, scanning this grid with a digital video camera, then comparing the received image with the synthesized grid and determining the surface parameters in each point [2,6]. Moiré fringes (mechanical interference phenomenon) are possible in the following cases:…”

Section: Resultsmentioning

confidence: 99%

System for determining the state of the object surface based on fuzzy output rules

Lapteva

Kuzyakov

Andreeva

2022

J. Phys.: Conf. Ser.

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The article provides information on hydrocarbon production in the Russian Federation, accidents at facilities supervised by Rostekhnadzor, and also presents a statistical analysis of the causes of accidents at high-risk facilities. Typical issues of studying the condition of the surface of an oil and gas object are considered on the basis of the electron-projection method that simulates the moiré effect and evaluates the surface topology by a system of of fuzzy inference rules implemented in the structure of a neural network.

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Section: Resultsmentioning

confidence: 99%

System for determining the state of the object surface based on fuzzy output rules

Lapteva

Kuzyakov

Andreeva

2022

J. Phys.: Conf. Ser.

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“…The further away the measurement point is from the hole, the greater the error owing to the influence of the stress gradient in the field. Thus, Durelli and Rajaiah [35] suggested making the measurements at distance r 5 1.4a, and Cárdenas-García et al [36] deduced the expressions for taking data at two points on the symmetry axes of the isochromatic fringe pattern, at any distance from the centre of the hole (Fig. 3, points E and F).…”

Section: The Hole Methodsmentioning

confidence: 99%

Stress-separation techniques in photoelasticity: A review

Fernández

Alegre

Díez

et al. 2009

The Journal of Strain Analysis for Engineering Design

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Photoelasticity has been used for decades in the experimental measurement of stresses and strains. As data-acquisition techniques only identify the differences between principal stresses and strains, stress-separation techniques exist to identify each of their values separately. A variety of techniques have been developed since the early days of photoelasticity, aiming to automate the measurement process, to exploit the full potential of photoelastic methods, and to facilitate its application. The purpose of this paper is to provide a general overview of the different stress-separation techniques, and their current state of development and usage. The paper presents the publications and the authors who have contributed to the development of new techniques.

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“…Several methods have been employed with photoelasticity to find a solution to this problem. One method involves the drilling of small circular holes over the surface of the testing object, the diameter of which is on the order of the thickness of the photoelastic coating, creating numerous traction free boundaries [4]. Another method combines normal incidence photoelastic measurements with oblique incidence measurements.…”

Section: Combination Of Thermoelasticity and Photoelasticitymentioning

confidence: 99%

Combined Thermoelastic and Photoelastic Full-Field Stress Measurement

Woolard

Hinders

Welch

1999

Review of Progress in Quantitative Nondestructive Evaluation

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INTRODUCfIONAccurate determination of stress distributions is essential in assessing the structural integrity of a component. Photoelasticity and thennoelasticity are full field nondestructive methods used to measure the stress state of an object.Photoelasticity has been used for decades to accurately measure surface strains in a structure. In this method the test part, complex or not, is first coated with a strain-sensitive plastic coating and then subjected to an external load. The strains which exist throughout the part and over its surface are transferred to the coating and observed as optical interference fringes with a reflection polariscope. Two different fringe patterns are produced with the polariscope --isochromatics via circular polarization and isoclinics via linear polarization. Isochromatic fringes appear as a series of successive and contiguous different-colored bands each representing a different degree of birefringence corresponding to the underlying strain. The patterns can be read like a topographic map to visualize the stress distribution over the surface of the coated test part. The isoclinic fringes appear as black bands providing the direction of the principal strain [1][2]. Now that digital cameras and image processing are common, photoelasticity is undergoing a renaissance.Whereas photoelasticity is an optical method, thennoelasticity is based on temperature changes induced by expansion and compression of the test part. Although this coupling between mechanical defonnation and thennal energy has been known for over a century, it has only been recently that this phenomenon has been exploited as a means of experimental stress analysis. The heat generated from the thennoelastic effect is small --O.2°C for mild steel just below its yielding point --requiring thennoelastic stress analysis to be perfonned under a dynamic loading condition of a sufficiently high frequency to maintain an effectively adiabatic state in the material [3]. For practical thennoelastic measurements using infrared thennography, the object under examination must have a highly emissive surface. For objects with low emissivity, such as metallic surfaces, a coating must be added, such as flat black paint. COMBINATION OF THERMOELASTICITY AND PHOTOELASTICITYThennoelastic signals are proportional to the sum of the principal stresses (a is the thennal conductivity, p is the density, C" is the specific heat capacity) whereas photoelasticity measures the difference of the principal stresses plus the principal stress

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Determination of strains in photoelastic coatings

Cited by 10 publications

References 3 publications

System for determining the state of the object surface based on fuzzy output rules

System for determining the state of the object surface based on fuzzy output rules

Stress-separation techniques in photoelasticity: A review

Combined Thermoelastic and Photoelastic Full-Field Stress Measurement

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