Showing papers on "Photoelasticity published in 1976"
TL;DR: In this article, the authors discussed the nature of the singularity that arises at a sharp edge in contact problems with friction, and the theoretical treatment is based on the Mellin transform of the elastic fields.
Abstract: The paper discusses the nature of the singularity that arises at a sharp edge in contact problems with friction. The theoretical treatment is based on the Mellin transform of the elastic fields. The results regarding the power singularities confirm the previous work of Gdoutos and Theocaris, but it is shown that logarithmic singularities are always present. Some experimental observations in photoelasticity are also presented.
99 citations
TL;DR: In this paper, a dynamic finite-element code, HONDO, was used to analyze two single-edged-notch fracturing Homalite-100 plates which had been previously studied by dynamic photoelasticity.
Abstract: A dynamic-finite-element code, HONDO, was used to analyze two single-edged-notch fracturing Homalite-100 plates which had been previously studied by dynamic photoelasticity. A single-edged crack in the finite-element model was advanced in incremental jumps such that the time-averaged crack velocity matched the measured crack velocity in the Homalite-100 plate. Dynamic-energy-release rates were computed for a constant-velocity crack and a crack which arrested after a somewhat constant deceleration. These results were compared with the corresponding dynamic-energy-release rates, which were computed from the dynamic-stress-intensity factors determined by dynamic photoelasticity, and with static-strain energyrelease rates. Despite the crude modeling of the running crack, the coarseness of the finite-element-grid breakdown and the differences in the modeled and actual grip conditions, the computed and measured dynamic-energy-release rates, except for occasional large differences, generally agreed within 10 percent of each other.
36 citations
TL;DR: In this article, photoelasticity has been reformulated for application to orthotropic composite materials, and stress-optic laws governing two-dimensional plane stress cases are obtained.
28 citations
TL;DR: In this article, the photoelastic tensor elements of the piezoelectric semiconductor ZnO were measured by the comparative acousto-optic diffraction method (reference material, fused quartz) at an acoustic frequency of 250 MHz and an optical wavelength of 0.633 μm.
Abstract: The photoelastic tensor elements of the piezoelectric semiconductor ZnO were measured by the comparative acousto‐optic diffraction method (reference material, fused quartz) at an acoustic frequency of 250 MHz and an optical wavelength of 0.633 μm. Two crystals with different conductivities, one is highly conductive and the other is highly resistive, were used as samples. The measured photoelastic tensor elements for piezoactive strains are different between these two samples. The difference is explained by the electro‐optic contribution to the photoelasticity induced by the electric field accompanying the piezoactive acoustic wave in the highly resistive sample and its screening by free carriers in the highly conductive sample. The contribution of the rotation of the volume element to the photoelasticity has been also observed in photoelastic tensor elements for shear strains.
23 citations
15 citations
13 citations
TL;DR: In this paper, a method for the determination of the side pressure distribution of the pressed powder bed by the scattered-light photoelastic technique has been proposed, where a cylindrical container made of photo-elastic-sensitive material was used as a die, the powder in which was pressed uniaxially.
13 citations
TL;DR: In this paper, the speckle patterns scattered from the boundary surfaces of a birefringent slice are imaged on a photographic plate and the results are similar to those obtained by observing this thin slice in a classical parallel or crossed polariscope.
11 citations
TL;DR: In this paper, a method for fractional-order determination using common rotation of polarizer-analyzer is described, and the relative performance of this method is discussed and its application to the automated bichromatic polariscope described.
Abstract: In most polariscopes, the fringe-order determination is performed by compensators and the fractional orders are measured using the well-known Tardy or Senarmont methods. The method described here provides the capability of fractional-order determination using common rotation of polarizer-analyzer, thus simplifying somewhat the construction and use of the polariscope. The relative performance of this method is discussed and its application to the automated bichromatic polariscope described.
10 citations
TL;DR: In this article, a polariscope has been built for studies of the stresses in optical fibers and the stress optic coefficient has been determined for five different fibers and for one of preforms from which one of the fibers was drawn.
Abstract: A polariscope has been built for studies of the stresses in optical fibers. The stress optic coefficient has been determined for five different fibers and for one of the preforms from which one of the fibers was drawn. It was found that the coefficient of the preform was larger than that of the fiber from which it was drawn. Calculations based on measurements on a Corning B fiber indicate that the residual stress in the cladding is compressive. The polariscope has also been used in conjunction with a fiber‐drawing machine and a diameter‐measuring instrument to determine the relationship between the tension of a Vycor‐clad quartz fiber, as it is being drawn, and the diameter of the fiber.
10 citations
01 Oct 1976
TL;DR: In this article, a new method for testing material properties under uniform plane stress conditions by means of specially designed plane specimen was proposed, which is of particular importance for fiber composite testing.
Abstract: : This work is concerned with a new method for testing material properties under uniform plane stress conditions by means of specially designed plane specimen. Photoelastic analysis showed that in the significant section of the specimen it is possible to produce uniform plane stress with high accuracy subject to the limitation that the principal stresses are of different signs. An important special case of loading produces shear on the significant section. The method is of particular importance for fiber composite testing. Preliminary experimental results presented are encouraging. (Author)
TL;DR: In this paper, a method for the calibration of equidensity lines produced from conventional fringe patterns by the use of a special Agfa-Gevaert film was presented, which is an important area of application.
Abstract: A method is presented for the calibration of equidensity ‘lines’ produced from conventional fringe patterns by the use of a special Agfa-Gevaert film. Photoelasticity is an important area of application.
TL;DR: In this paper, the properties of the birefringent and the rotatory power of a thin transparent medium are determined statically point by point by phase measurement or by compensation with zero phase change.
TL;DR: In this paper, direct photography and copying from conventional negatives are described and practical considerations indicated, as well as practical considerations for applying equidensity techniques in photoelastic practice and other work requiring evaluation of optical fringes.
Abstract: Agfacontour film has simplified photographic procedures so that equidensity techniques can now be applied in photoelastic practice and other work requiring evaluation of optical fringes for fractional orders. Direct photography and copying from conventional negatives are described and practical considerations indicated.
TL;DR: In this article, the dynamic photoelasticity was used to analyze the Battelle-type wedge-loaded double cantilever beam (DCB) specimen machined from Homalite-100 sheets of 3/8in. (9.5 mm) thickness.
Abstract: Dynamic photoelasticity was used to analyze the Battelle-type wedge-loaded double cantilever beam (DCB) specimen machined from Homalite-100 sheets of 3/8-in. (9.5 mm) thickness. Dynamic stress intensity factors, dynamic energy release rate, crack velocities of straight and curved cracks were determined. Corresponding static stress intensity factors were calculated by the method of finite element analysis. These results were compared against Kanninen's analytical results and experimental results by Hahn et al using steel specimen. While dynamic photoelasticity results show qualitative agreement with Kanninen's results, the two differ in detail.
TL;DR: In this article, the effect of a side notch used as a crack guide in a double-cantilever-beam specimen is investigated, and the resulting stress distribution along the section of symmetry ahead of the notch is obtained from a three-dimensional photoelastic model.
Abstract: The effect of a side notch used as a crack guide in a double-cantilever-beam specimen is investigated. The resulting stress distribution along the section of symmetry ahead of the notch is obtained from a three-dimensional photoelastic model. The effect of the side notch through the thickness and down the side of the specimen is determined. After stress freezing, the model was sliced along principal planes. Along the x-x plane of symmetry, the principal stresses were determined by graphical integration of Filon's transformation of the Lame-Maxwell equations and by subslicing along the x-z plane. Results of the investigation are in good agreement with those of other investigators. The side notch increases the value of the maximum tensile stress at the intersection of the starter notch and the side notch by approximately 22 percent.
TL;DR: By double passing the object beam in photo-elastic-holographic interferometry, separation of the isochromatic-isopachic patterns can be achieved.
Abstract: By double passing the object beam in photoelastic-holographic interferometry, separation of the isochromatic-isopachic patterns can be achieved. The object beam must then interact with a suitable polarizing element between the first and second pass.
TL;DR: In this article, real-time holographic interferometry is applied to determine the absolute retardation fringes in the photoelastic analysis of plane models, which requires only one hologram recorded with the model unloaded.
Abstract: In this paper, real-time holographic interferometry is applied to determine the absolute-retardation fringes in the photoelastic analysis of plane models. The method requires only one hologram recorded with the model unloaded. In the reconstruction process, the mcdel is loaded and the polarizers on the reference and object beams are rotated through the same angle. At the points of the model where the polarization direction is parallel to one of the principal stresses, only the corresponding family of absolute retardations is obtained. The technique is demonstrated experimentally using a deep beam centrally loaded.
TL;DR: In this article, stress analysis of the components of a shrinkfit assembly has been carried out by the three-dimensional photoelastic technique and it is concluded that the bending induced in the components due to the asymmetrical placement of the wheel and the contact shear at the interface influences the stress distribution quite considerably.
Abstract: Stress analysis of the components of a shrinkfit assembly has been carried out by the three-dimensional photoelastic technique. Experimental results obtained from the analysis of a typical shrink-fit assembly, wherein a cylindrical wheel is shrink fitted onto a hollow cylindrical hub in an asymmetrical position. Photoelastic models made from hot-setting Araldite B were loaded at the critical temperature in a stress-freezing oven and the meridional and the hoop slices were observed in a transmission polariscope. It is concluded from this investigation that the bending induced in the components due to the asymmetrical placement of the wheel and the contact shear at the interface influences the stress distribution quite considerably. Also, the dimensions of the components in the axial direction have an influence on the mode and contribute to the magnitude of the variation of stress components.
TL;DR: In this paper, a photoelastic model is illuminated by the light from a depolarizing diffuser, and the pattern is obtained by observing the primary image of a hologram doubly exposed with the unstressed and the stressed model.
Abstract: In order to obtain the isochromatic and isopachic fringe pattern which Nisida and Saito have observed in a Mach-Zehnder interferometer, a new holographic method is developed. A photoelastic model is illuminated by the light from a depolarizing diffuser. The pattern is obtained by observing the primary image of a hologram doubly exposed with the unstressed and the stressed model. The experimental condition in this method is as easy as that in the ordinary double-exposure holographic photoelasticity.
TL;DR: In this paper, the authors describe three purely graphical methods and a method requiring conventional compensation for only a single point or along a single line in the isochromatic pattern of the model or slice in the polariscope.
TL;DR: In this article, a technique for applying a well-defined dynamic load to models for studies in dynamic photoelasticity is described, which is suited to studies where simple variation and accurate determination of the load-cycle parameters, as well as precise reproducibility are necessary.
Abstract: A versatile technique for applying a well-defined dynamic load to models for studies in dynamic photoelasticity is described. The method utilizes the shock front produced in a gas-dynamic shock tube to apply a load to models by direct normal impact. The principles and scope of the method are described and some examples of the dynamic stresses arising from shock-front impact on a low-modulus photoelastic model are presented and discussed. The method is suited to studies where simple variation and accurate determination of the load-cycle parameters, as well as precise reproducibility, are necessary. The method, in addition, permits close-field study of the initial response of materials to dynamic loading to be undertaken.
TL;DR: An improved holographic method to obtain the three patterns, that is, Nisida and Saito's pattern, Fourney and Mate's pattern and dark-field isochromatics in photoelasticity is studied in this paper.
Abstract: An improved holographic method to obtain the three patterns, that is, Nisida and Saito's pattern, Fourney and Mate's pattern and dark-field isochromatics in photoelasticity is studied. The present method is to record two components of object polarization separately on a holographic plate and to reconstruct them by using orthogonally polarized reference beams through an alternating arrangement of strip polarizers whose adjacent transmission axes are perpendicular to each other. In this experimental method the three patterns are more easily obtained from a single double-exposure hologram than in the method of Lohmann used to reconstruct object polarization.
TL;DR: In this paper, the authors used a material with a Poisson's ratio equal to about 0.4 at the critical temperature to solve the problem of 3D photoelasticity.
Abstract: The “freezing” method of three-dimensional photoelasticity uses materials which exhibit a Poisson's ratio equal to 0.5 at the critical temperature. Two important limitations follow: 1) the solution obtained applies only to materials with high Poisson's ratio. 2) to obtain principal stresses it is not possible to supplement birefringence measurements with mechanical or moire measurements. The new method uses a material with Poisson's ratio equal to about 0.4. Since the deformations are relatively large, (of the order of 1%) and the material is not incompressible, mechanical or moire measurements can be used to supplement birefringence measurements. If desired the method can be self sufficient and solve completely three-dimensional problems using only mechanical or moire measurements. A sphere subjected to diametral loading is used to illustrate the application of the method and the precision of the results obtained.
TL;DR: In this article, a dynamic photoelasticity was employed to determine the velocity of longitudinal stress waves, dynamic modulus of elasticity and attenuation coefficients in rockcore samples 1 in. (25 mm) in diameter, 18 in.(0.46 m) long.
Abstract: Dynamic photoelasticity was employed to determine the velocity of longitudinal stress waves, dynamic modulus of elasticity and attenuation coefficients in rockcore samples 1 in. (25 mm) in diameter, 18 in. (0.46 m) long. Birefringent strips bonded to the core samples of Salem limestone, Charcoal granite and Berea sandstone provided all the data needed for the dynamic characterization of these rock types.
TL;DR: In this paper, a simple method is presented to analyze the time variation of the principal-strain directions, which is applied to the analysis of the resulting principal directions in a region in which a superposition of a compression and a shear wave occurred.
Abstract: In this paper a simple method is presented to analyze the time variation of the principal-strain directions. The experimental arrangement to be used consists of a dark-field linear polariscope, a beam of monochromatic parallel light with a small diameter penetrating the measuring point with normal incidence. The variation of the light intensity behind the analyzer was measured by a photocell and a CRO. According to the method introduced here, two variations of light intensity were measured by choosing two orientations of the crossed system of polarizer and analyzer. The difference between the orientations is 45 deg. This method was applied to the analysis of the resulting principal directions in a region in which a superposition of a compression and a shear wave occurred. These waves were produced in a photoelastic foil, which was cemented on a brass rod impacted longitudinally. The compressional main pulse generated in the rod has a duration of about 25 μs. This experimental arrangement will be used later to investigate the behavior of the photoelastic material under short-time loading.
01 Jan 1976
TL;DR: In this article, the authors compared dynamic finite element and dynamic photoelastic analyses of single edgenotched tension plates and one-dimensional dynamic, and dynamic photosensitivity analyses of wedge-loaded double cantilever beam (DCB) specimens verified the existence of large fluctuations in dynamic stress intensity factors during crack propagation in the specimens considered in these investigations.
Abstract: Previous dynamic photoelasticity results on single edge- notched tension plates without and with stringer reinforcements, dynamic tear test (DTT) specimens and wedge- loaded double cantilever beam (DCB) specimens are reviewed and some common fracture dynamic features in these three specimens machined from 9.53 mm thick Homalite-100 plates are discussed. Comparisons between dynamic finite element and dynamic photoelastic analyses of single edgenotched tension plates and one-dimensional dynamic, and dynamic photoelasticity analyses of wedge-loaded DCB specimens verified the existence of large fluctuations in dynamic stress intensity factors during crack propagation in the specimens considered in these investigations.
TL;DR: An application of polarization holography by Kurtz's method to photoelasticity is presented in this article, by using a diffused and depolarized reference wave a single-exposture and a double-exposure hologram are made for a photo-elastic model.
Abstract: An application of polarization holography by Kurtz's method to photoelasticity is presented. By using a diffused and depolarized reference wave a single-exposture and a double-exposure hologram are made for a photoelastic model. The single-exposure hologram produces isochromatics and isoclinics which are useful for dynamic stress analysis, and the double-exposure hologram produces Nisida and Saito's pattern, Fourney and Mate's pattern and dark-field isochromatics. Kurtz's method as well as Lohmann's method can be applied to photoelastic stress analysis by using the technique of single-exposure and double-exposure holography.
Patent•
09 Jan 1976
TL;DR: In this article, a monochromatic light source is followed by a means of polarisation and a focussing system which transmits a light beam onto a model to be studied.
Abstract: Two dimensional photoelasticity meter and visualisation system, us polarised light and an automatic polarimeter to produce an image of a model, has a monochromatic light source (1) followed by a means of polarisation (3) and a focussing system which transmits a light beam (2) onto a model (4) to be studied. The phase shift introduced into the beam by the model is analysed by an automatic polarimeter (5) which comprises a second light source (10) and a system for deflecting and focussing the received beam in order to form an image of the model illuminated by the second light beam on a screen (17).