Showing papers on "Photoelasticity published in 1970"
TL;DR: In this paper, a 16-spark gap, modified schardin-type camera was constructed for use in dynamic photoelastic analysis of fracturing plastic plates, 3/8 in. × 10 in.
Abstract: A 16-spark gap, modified schardin-type camera was constructed for use in dynamic photoelastic analysis of fracturing plastic plates. Using this camera system, dynamic photoelastic patterns in fracturing Homalite-100 plates, 3/8 in. × 10 in. × 15 in. with an effective test area of 10 in. × 10 in., loaded under fixed grip condition were recorded. The loading conditions were adjusted such that crack acceleration, branching, constant velocity, deceleration and arrest were achieved.
169 citations
TL;DR: In this paper, a holographic method for reconstructing polarization of light emitted by photoelastic model, obtaining isochromatic and isoclinic fringe patterns, was proposed.
Abstract: Holographic method for reconstructing polarization of light emitted by photoelastic model, obtaining isochromatic and isoclinic fringe patterns
46 citations
TL;DR: In this paper, the basic equations governing the propagation of polarized light in a three-dimensional photoelastic model located in a magnetic field are derived, and an algorithm is developed that permits the study of the optical phenomena in the case of arbitrary stress distribution along the wave normal.
Abstract: The basic equations governing the propagation of polarized light in a three-dimensional photoelastic model located in a magnetic field are derived. Optical phenomena in this case can be adequately described by the aid of the theory of characteristic directions developed previously by the author. The case when the principal-stress difference, as well as the magnetic field, is constant is considered in detail. An algorithm is developed that permits the study of the optical phenomena in the case of arbitrary stress distribution along the wave normal. As an example, investigation of the bending of plates is considered; graphs are produced that permit the determination of the stress components on the basis of experimental data. Some considerations of the experimental technique are given.
22 citations
TL;DR: In this article, an automatic method for measuring polarization forms is described, and the application of the preceding results to both automatic two-and three-dimensional photoelasticity by scattered light is described.
14 citations
TL;DR: In this paper, the propagation of plane electromagnetic waves in a non-absorbing material which is subjected to finite deformations is considered and the theory is formulated from both Eulerian and Lagrangian points-of-view.
Abstract: In this paper we consider the propagation of plane electromagnetic waves in a non-absorbing material which is subjected to finite deformations. It is assumed that the material is isotropic when undeformed and when no electromagnetic fields are present and that it is centrosymmetric. The theory is formulated from both Eulerian and Lagrangian points-of-view. The latter formulation rests on the Lagrangian formulation of Maxwell’s equations for a deformed material due to Walker, Pipkin and Rivlin [1].
10 citations
TL;DR: In this paper, the authors deal with stresses and large strains around an elliptic hole located symmetrically in the center of a long plate, where the deformation is sufficiently large to make the hole elliptical with the major axis parallel to the uniform tension.
Abstract: This paper deals with stresses and large strains around an elliptic hole located symmetrically in the center of a long plate. The plate is loaded with uniform tension parallel to the minor axis. The deformation is sufficiently large to make the hole elliptical with the major axis parallel to the uniform tension. A series of five plate widths were investigated. Stresses and strains were analyzed for each plate width and for successive steps of load. Several experimental techniques were combined to solve the problem. Photoelasticity was used to determine stresses which are reported using a new definition for stress. Moire and grids were used to determine strains. Stress and strain concentration factors are evaluated at critical points on the axes.
10 citations
TL;DR: In this article, a set of equations is presented and the effect of rotation of the secondary principal stress axes is discussed, and a technique is suggested which can eliminate any error resulting from rotation.
Abstract: A set of equations is presented and the effect of rotation of the secondary principal stress axes is discussed. The equations, general and relatively simple, adequately describe observed results. In studying the equations, a better understanding of the rotational effect can be achieved, and a technique is suggested which can eliminate any error resulting from rotation. This technique and the concepts involved are substantiated with experimental evidence and reported in this paper.
8 citations
01 Jan 1970
8 citations
TL;DR: In this paper, the stresses caused by shrink fits are evaluated by using Lame's solution or by other analytical methods in which it is assumed that the radial stresses on the surface of contact are distributed uniformly, or in some stepwise manner, and that friction forces between the bodies are zero.
Abstract: Stresses caused by shrink fits are commonly evaluated by using Lame's solution or by other analytical methods in which it is assumed that the radial stresses on the surface of contact are distributed uniformly, or in some stepwise manner, and that friction forces between the bodies are zero. These assumptions were not necessary in the experimental problem solved. Heretofore, no experimental techniques have been available to check the existing theories on a three-dimensional basis. The stresses which result when a short, hollow, thick-walled cylinder is shrunk over a shaft which is a solid shaft or a thick-walled, hollow shaft were determined. Equipment and techniques using scattered-light three-dimensional photoelasticity with a laser light source were developed and applied.
7 citations
TL;DR: The theory of the polariscope, based on Jones's metric equations, is given and the influence of imperfect quarter-wave plates is discussed in this paper, where the effect of light of incorrect wave-length on the resulting error is considered.
Abstract: The isoclinic parameter can be determined from points of intersection of two systems of characteristic lines called secondary isochromatics. These lines, along which the light intensity is a minimum, can be observed in monochromatic light in an originally linear polariscope with two crossed quarter-wave plates in which the polarizer and analyser have been rotated through small angles in opposite direction.The theory of the polariscope, based on Jones's metric equations, is given and the influence of imperfect quarter-wave plates is discussed. The effect of light of incorrect wave-length on the resulting error is considered. A disc loaded by two opposite compression forces is used for demonstration of the methods.
4 citations
TL;DR: In this paper, a very sensitive photomultiplier tube and laser light source were used to record stress-optic data associated with a moving stress wave using a "gray-field" (which is halfway between a dark and light field) polariscope.
Abstract: A very sensitive, fast-responding photomultiplier tube and laser light source were used to record stress-optic data associated with a moving stress wave. By using a “gray-field” (which is halfway between a dark and light field) polariscope, optical-electrical recordings were obtained which were linearly proportional to strain. A discriminatory record results which exhibits a higher signal-to-noise ratio than semiconductor strain gages. Gage length can be varied from 0.005 in. upwards.
TL;DR: In this article, it was shown that the full-field fringes are little disturbed by the presence of the small perforations and an extension of the method to reveal bending-stress trajectories in plates loaded out of plane.
Abstract: A disadvantage of the embedded-polariscope method is the inability to observe isoclinics because the embedded Polaroid sheets are fixed within the model. Perforating the embedded active layer with an array of small-diameter holes allows observation of stress trajectories in the layer from the isochromatic patterns. Further, it is shown that the full-field fringes are little disturbed by the presence of the small perforations. The techniques of model fabrication are described, as well as an extension of the method to reveal bending-stress trajectories in plates loaded out of plane.
TL;DR: In this article, the authors deal with an experimental determination of the stress distribution in a cylindrical shell with two diametrically opposite reinforced circular holes of different diameters, subjected to internal pressure.
Abstract: This paper deals with an experimental determination of the stress distribution in a cylindrical shell with two diametrically opposite reinforced circular holes of different diameters. The shell is subjected to internal pressure. Both brittle coating and three-dimensional photoelasticity were used in the analysis. The results obtained are compared with those corresponding to a non-reinforced hole in a cylindrical shell with and without ribs.
01 Jan 1970
TL;DR: In this paper, the authors investigated the stress distribution in two-dimensional disCONTinuous plate models with regular orthogonal join sets and found that the model's performance was negatively affected by the presence of VOIDS ALONG JOINTS, the ratio of the applied pressure, and the number of joins.
Abstract: THE STRESS DISTRIBUTION IN TWO-DIMENSIONAL DISCONTINUOUS PLATE MODELS WITH REGULAR ORTHOGONAL JOINT SETS WAS STUDIED. THE JOINT SETS CONSIDERED WERE EITHER HORIZONTAL AND VERTICAL OR INCLINED. THE MODELS WERE MADE FROM GLASS BRICKS OR FRACTURED GLASS PLATES. A NEW BI-AXIAL COMPRESSION TEST RIG WAS DEVELOPED. THE RIG APPLIED UNIFORM PRESSURES EVEN WHEN LARGE RELATIVE DISPLACEMENTS TOOK PLACE ALONG THE EDGES OF THE MODEL DURING LOADING. IT WAS DEMONSTRATED PHOTOELASTICALLY THAT THE STRESS DISTRIBUTION IN A JOINTED ROCK MASS WAS AFFECTED BY (1)THE PRESENCE OF VOIDS ALONG JOINTS, (2) THE RATIO OF THE APPLIED PRESSURES, (3) THE INCLINATION OF JOINTS TO THE DIRECTION OF THE APPLIED PRESSURES, (4) THE MANNER IN WHICH THE PRESSURES WERE APPLIED (STRESS HISTORY). /AUTHOR/
TL;DR: The dispersion of birefringence of three polymers commonly used in photoelasticity studies has been measured at several ir and visible wavelengths and the results have been correlated with transmittance spectra as discussed by the authors.
Abstract: The dispersion of birefringence of three polymers commonly used in photoelasticity studies has been measured at several ir and visible wavelengths and the results have been correlated with transmittance spectra. The change of stress-optic coefficient in the visible region ranges from 6% for CR-39 and 16% for P-6 to 17% for polycarbonate. The dispersion of birefringence is anomalous on the short-wavelength side of an absorption band, and normal on the long-wavelength edge. The dispersion is small in spectral regions that are far from resonance frequencies.
DOI•
01 Jan 1970
TL;DR: In this paper, an optimum form of cut-out in the cross-girder is searched out and the authors present several interesting conclusions about the stress distribution in the orthotropic plate.
Abstract: Orthotropic plate has been investigated and the static and dynamic stresses were obtained using several theoretical and experimental methods: finite element method, folded plate theory, modal analysis, strain gauges, photoelasticity. An optimum form of cut-outs in the cross-girder is searched out and the paper presents several interesting conclusions about the stress distribution in the orthotropic plate.
TL;DR: In this paper, the onset of instability and the subsequent buckling process have been analyzed using high speed photography to record change in the photoelastic isoclinic patterns both qualitative and quantitative results are presented concerning the inception of buckling which have never been achieved by other means.
Abstract: This paper contains the results of several investigations conducted by the author with photoelastic circular cylindrical shells under axial compression The onset of instability and the subsequent buckling process have been analyzed using high speed photography to record change in the photoelastic isoclinic patterns Both qualitative and quantitative results are presented concerning the inception of buckling which have never been achieved by other means The application of high speed photography to the photoelastic analysis of some structural stability problems is demonstrated and results compared with reflected light techniques and mechanical measurements
TL;DR: In this article, the authors applied the photoelastic tedinique to obtain the distribution of stresses in some critical points of the human body, specifically in the femur and the mandibular bones.
Abstract: The photoelastic tedinique is applied to obtain the distribution of stresses in some critical points of the human body, specifically in the femur and the mandibular bones. The study is done based on simplified hypothesis, using two and three-dimensional photoelastic models, and the results are correlated with real bones and also compared with some results from the literature.
TL;DR: In this paper, the relation between the optical path difference and the difference in the principal stresses for a plane stressed state over a certain time interval may be expressed in the form of Eq. (7), analogous to the Wertheim equation in photoelasticity.
Abstract: 1.
The material PN-1 used in the method of hereditary photoelasticity is obtained from original oligomers produced on the industrial scale; their hardening presents no difficulties under laboratory conditions.
2.
The absence of optical creep in PN-1 enables us to dispense with the use of isochronic curves in (δ, σ1−σ2) coordinates in order to convert from the optical quantities to the mechanical quantities. The relation between the optical path difference and the difference in the principal stresses for a plane stressed state over a certain time interval may be expressed in the form of Eq. (7), analogous to the Wertheim equation in photoelasticity.
3.
The use of Eq. (7) increases the accuracy of the transition from optical to mechanical quantities, which in turn increases the reliability of the results obtained in the solution of specific problems. The coefficient Ct is determined to a fairly high accuracy from the results of the tests on the samples.
4.
All the mechanical processes in PN-1 take place an order of magnitude more quickly, and the necessary measurements may be made in 1.5–2 h.
TL;DR: In this paper, a case-bonded solid propellant with a stargrain internal boundary was used to determine the stress distribution in a three-dimensional, solid-propellant rocket motor.
Abstract: Scattered-light photoelasticity, a nondestructive technique, is used to determine the stress distribution in a three-dimensional, solid-propellant rocket motor. The model is a case-bonded solid propellant with a stargrain internal boundary. Stresses are induced by internal pressure. The pressure load simulates part of the stresses developed in firing a rocket. The model material is polyurethane rubber which is similar to the binder material in actual rockets. The model construction and data analysis are discussed in detail, and the results are presented in graphical form.
TL;DR: In this paper, a theory of photoelasticity in ionic crystals is proposed wherein the overlap of the electronic atmospheres of adjacent ions and the effect of strain on the ionic polarisabilities are considered the dominant factors.
Abstract: A theory of photoelasticity in ionic crystals is proposed wherein the overlap of the electronic atmospheres of adjacent ions and the effect of strain on the ionic polarisabilities are considered the dominant factors. The sign of the stress optical constant predicted by this theory is found to be in agreement with the experimental result. The change in the sign of the stress optical constant at lower wavelengths exhibited by some of the alkali halides is also explained. The ‘pure’ temperature effect observed in the thermo-optic behaviour of crystals turns out to be a natural consequence of the proposed theory.
01 Jan 1970
TL;DR: The major methods of photoelasticity are based on the analysis of induced and orientational birefringence by measuring the change of polarized radiant power transmitted or reflected from the body under observation.
Abstract: The term “Photoelasticity“ [5]*) describes methods of investigation and numerical evaluation of some mechanical quantities as strain, stress, mode of deformation, velocity distribution, etc..., in solid and fluid bodies by analyzing the change of state and velocity of electromagnetic radiation interacting with these bodies. The major methods of Photoelasticity are based on the analysis of induced and orientational birefringence by measuring the change of polarized radiant power transmitted or reflected from the body under observation.
01 Apr 1970
TL;DR: In this article, the authors applied dynamic photoelasticity to a study of hypervelocity impact phenomena, and used a Plexiglas rod acting as a Hopkinson pressure bar in a transmission polariscope arrangement, sensing the pressure time history resulting from debris stagnation in the second plate.
Abstract: : The technique of dynamic photoelasticity has been applied to a study of hypervelocity impact phenomena. The target consisted of a cadmium front plate, followed either by a void or a foam filled space, and a rear plate of steel or aluminum. Two series of tests were carried out. The first, employing a Plexiglas rod, acting as a Hopkinson pressure bar in a transmission polariscope arrangement, sensed the pressure time history resulting from debris stagnation in the second plate. In the second series, the rear plate was provided with a photoelastic coating as part of a reflection polariscope. Dynamic stress patterns, produced by a debris impact, were photographed as they developed in time and provided a whole field view of the nature of the pattern. The experimental results indicate that Plexiglas can be used successfully as a pressure bar for dynamic stress measurements in the range of several kilobars. Analysis of dynamic plate motion indicates the presence of elastic extensional waves and shows that second plate deformation and rupture are accompanied by elastic effects.
TL;DR: In this paper, an experimental method is described whereby symmetrically loaded cylinders of non-uniform thickness are analyzed using two-dimensional photoelastic models mounted on elastic foundations.
Abstract: An experimental method is described whereby symmetrically loaded cylinders of nonuniform thickness are analyzed using two-dimensional photoelastic models mounted on elastic foundations. The technique is most conveniently applied to ring-stiffened or notched cylinders. The particular model studied simulated a notched cylindrical pressure vessel which had been previously studied with three-dimensional photoelasticity. The stress-concentration factors at the base of the notch, found using both methods, showed excellent agreement. An analysis was also performed which allows estimation of the error involved when a beam-on-elastic-foundation model does not rigorously simulate a cylinder.
TL;DR: In this paper, it is proved that the immersion analogy can be used to analyze these stresses in composite bodies provided all the materials of such bodies have the same weight per unit volume.
Abstract: This paper is a contribution to the experimental stress analysis of composite structures subjected to gravitational forces. It is proved, generally, that the immersion analogy can be used to analyze these stresses in composite bodies provided all the materials of such bodies have the same weight per unit volume. Applications are described in two-dimensional problems immersing urethane-rubber models bonded to epoxy shells in a thallium-formate solution. Photoelasticity is used to determine stresses. The method increases the response obtained and will have application in the solution of problems where constant-acceleration stresses are important, as in dams and solid-propellant rocket grains.
TL;DR: In this paper, photoelasticity offers definite advantages in the analysis of complex shapes used in plastics in construction, enabling the analyst to see magnitude and direction of stresses, as well as lo cation.
Abstract: Photoelasticity offers definite advantages in the analysis of complex shapes used in plastics in construction. It enables the analyst to see magnitude and direction of stresses, as well as lo cation. Applications include cast-in-place joint seals, highways, butt joints, and lap joints.
01 Jan 1970