A new photoelastic equipment is made on trial for all visible region of light. A common equipment has two quarter wave plates which satisfy only for a monochromatic light. New equipment has two sets of composite quarter wave plates for all visible region of light. Its set is also composed of a right and left handed circular polarizers. The composite quarter wave plate consists of two phase plates which have suitable retardations and can be easily made from two sheets of transparent polymer. They are adaptable for various wave lengths by changing azimuth angles of phase plates. Their angles can be calculated or cited the numerical tables of composite quarter plates. Its equipment can be also used in the bright and dark field by 90° rotation of the analyzer. We could take several photoelastic photographs by changing color under same conditions except photoelastic sensitivity.

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A method for geometrical analysis of the τxy-network and a finite difference method of applying it to the problem of stresses measurement in a two-dimensional photoelastic model are developed. The distribution of sums of principal stresses is determined by solving Laplace's equation numerically with the boundary conditions obtained isochromatically. Subsequently, the distribution of shear stresses τxy is calculated numerically by solving the equation derived from equations of equilibrium using the sum of principal stresses. The method is illustrated by the application to cases of circular and square plates under opposite compression.
Results by the experimental and computational studies compare well with each other.

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In order to analyze direction of principal stress using photoelasticity, we have proposed a method which separates the isochromatics and the isoclinics from the fringe patterns obtained in the field of a plane polariscope. This method uses the extraction of frequency components of the Fourier transform of three-dimensional image processing. Theoretically, this method gives accurate results because of using a Fourier filter. Practically, however, the results obtained by this method are influenced by errors of experiments and analysis, and decrease accuracy.
In this paper, the effects of experimental noises and analytic errors on the results obtained by this method are discussed, and some methods to reduce them are proposed.

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The mixed-mode stress intensity factors and the effective stress intensity factors for the corner cracks of stepped plate subjected to axial tensile load are evaluated by means of photoelastic experiment. The epoxy resin models are prepared for lots of form factors on crack depth and crack angle.
The image processing analyzer is utilized to get the thinning image of the isochromatic fringe patterns around the crack tip. The intensity factors are estimated by means of personal computer using the program based on the over-deterministic method.
Those obtained stress intensity factors are summarized in the diagrams shown as the behavior for the variations of crack depth and crack angle, and the results are compared with the known theoretical results of the analogous problem, moreover, it is pointed out that the crack angle which produces the maximum effective stress intensity factor coincided with the direction of slip line of Prandel in punch problem.

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Shield tunnel lining is generally designed by assuming the patternized standard loads. But when a tunnel is to be designed under the unprecedented earth conditions or in the case of extremely large tunnel, it is important to ascertain the safty of the design by enough examinations and experiments. In such cases, the verification by the model analysis will be very useful.
In the tunnel lining experiment using photelastic method, the results are usually obtained as the inside stress distribution of lining model.
This paper shows the method of converting the experimental values to the load patterns which are used in the design. The weighted constants corresponding to the each patternized load are obtained by the least squares.

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Stresses around the boundary of a rectangular opening anchored with PS tendons of the precast concrete panel construction are investigated by theory of two dimentional elasticity.
In the case the opening is large, the anchoring of tendons at the boundary cannot be avoided. Then, the high stress concentration is found at the corners of the rectangular opening and is of great importance in engineering practice.
The results of photoelastic experiment and B.E.M. calculation are compared with the theoretical solution.

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A composite quarter-wave plate has been made up of two sheets of phase plate. It is discussed how the composite quarter-wave plate transforms a state of polarized light by using Müller's matrix, Stokes' parameter and Poincaré sphere. Instead of the quarter-wave plate, the composite quarter wave plate can be used for Sénarmont's and Turdy's compensator. That can make it possible to measure retardation of samples for all visible light. Good results of experimental data are obtained.

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Retardations of po1ymer films have been obtained by Senarmont compensator. Its method is used only for monochromatic light, because of dependence of its quater wave plate on wave length. In the present study, retardations of films can be obtained using the composite quater wave plate for all visible lights.
Relation between retardation Δ and optical path difference J of a sample is represented by a equation of
Δ=J·2π/λ,
where λ is optical wave length. On a graph of Δ vs 1/λ, the equation indicats a straight line which passes the origin and its slope is 2πJ.
If measured points for several monochromatic lights are plotted on the graph and a fitted line is calculated, we can obtain the absolute retardation of the test piece from its line.

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A formal mechanism of optical activity described by Mindlin-Aben type equations is clarified. On the basis of this result an approximate method for representing the behavior of polarized light in a photoelastic medium by “Piled Retarders Model (PRM) ” is investigated. PRM is defined as an optical system containing thin wave plates with various relative phase retardations, each of which is rotated with respect to the one preceding it through a definite angle. It is found that Aben's equations are represented as the limit of the equation B (z+Δz) =S (-φ) G (f₀Δz/2) S (φ) B (z) forΔz→0. Here, B is the complex vector of polarized light propagating along the z axis and S (-φ) G (f₀Δz/2) S (φ) represents a single wave plate having the thickness Δz, the retardation f₀Δz=C (σ₁-σ₂) Δz and the orientation φ at a point z in the medium, where σ_j and φ are the secondary principal stresses and the orientation of σ₁, respectively, and C is constant. This result enables us to regard an arbitrary optical path in the photoelastic medium as a system consisting of an infinite number of wave plates, each of which has the retardation f₀ (z) dz, the orientation φ (z) and the infinitesimal thickness dz at the point z, where f₀ (z) and φ (z) varies continuousluy along the path according to the stress distribution.

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The wavelet transform is a new method for time-frequency analysis of transient signal waveforms with short segments. Recently the study of the wavelet transform is developed rapidly and its applications become a center of attention in various field of engineering. In this paper, the wavelet transform is used as a tool for frequency estimation of a sine-wave signal with a short record length, and it is applied to determination of the photoelastic fringe-order using the loadincreasing method practically.

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