A method is proposed for the determination of the internal stresses in a two-dimensional system from data furnished by photoelastic analysis. The method involves the numerical integrations of the Laplace and Poisson difference equations over a region with known boundary values by the iteration of a set of improvement formulas. New procedures for increasing the speed and accuracy of such computations are described and application is made to a typical photoelastic study. In this the complete system of internal stresses is computed, using the data obtained from the usual fringe photograph, without recourse to isoclinic and isopachic lines, or other supplementary experimental measurements. As an application of method, the photoelastic investigation of stress distribution in square plate subjected to diagonal compression in carried out and the results are compared with that obtained by Frocht, and to yield results of good accuracy.

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It is widely recognized that stress intensity factor around crack tip is quite usefuto explain quantitatively material damage accompanying cracks and researching works are ongoing in this area in various ways. Generally, a crack can be regarded as a notch in the extremity with a sharp tip of infinitively small radius and it is considered important to comfirm experimentally the relation between crack and notch and the effect of crack tip shapes on stress intensity factors. In this paper. stress intensity factors were determined by hybrid methods of photoelastics and caustic methods. The model specimen was made from epoxy resin plate with four crack tip shapes (radius, slot, cast, razor). The effect of crack tip shapes on stress intensity factors was experimentally compared together with factor of rupture and stress concentration factor, and the results were discussed.

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Amethod of reconstructing some quantities of the dielectric tensor field in a birefringent and optically active body is theoreticany and numerically investigated by using optical equivalent method in shoe-type tomography. Reconstruction of an optical rotatory power of natural optical activity, differences and direCtions of the secondary principal dielectric values of the body is made numerically along a light path. Initial distributions of these values are given arbitrarily along the path and they are well reconstruCted by an algorithrm on the basis of tihe method

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In the fracture of the machine and the structure, the fatigue fracture is majority. The crack, which occurs because of fatigue, should often consider not only the single crack but also plural cracks' occurring. In this paper, the material strength when two or more cracks occurred because of fatigue etc. was examined by calculating stress intensity factor K value by using caustics method and the photoelasticity. In general, plural cracks are known K_I value decreases compared with the single crack. Therefore, the influence on K value was experimentally examined from the point of the distance between the cracks, the angle, and the crack length and the mode change. As a result, K_I value influences destruction in plural in exist only mode I and the mixed mode of mode I and mode II like this research cracks. When the crack length becomes long if the distance between the cracks narrows, the decrease of K_I value grows. In addition, it has been understood that the decrease of K_I value is influenced by a/W on the boundary of d/a=1 (the distance between the cracks is equal to the crack length).

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Recently, it is urgent need to look for the methods, which are applied to the elastoplastic and plastic stress-strain analysis to clarify the mechanism of plastic deformation and to establish the guideline for plastic design. While, Photoplasticity is a full-field technique that is based on the interpretation of optical patterns in transparent birefringent materials that have been stressed beyond their elastic limit. We tried to find the availability of the strain freezing method for the stress-strain analysis in photoplastic experiment prior to the present research. As a result a very fine linear relation was obtained between isochromatic fringe order (N) and principal strain difference (∈₁-∈₂) in the very wide range of various stress state. But these experimental studies were done only by the premise that static load state. In the present research, the aim of this paper is to discuss the relation between fringe order and principal strain in the one-dimensional stress at fixed strain state, to find and also to propose the best plastic strain freezing cycle at fixed strain state.

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C-column is on the marked recently for a building. The C-column has a diaphragm inside of the column at the portion where a beam will be welded. The diaphragm is devided two parts and has a space between the parts getting a welding machine to pass through. Then it is important to analyse the stress distribution in the diaphragm and design to be minimize the effect of deviding two parts. C-column is designed under the many scrupulous theoretical and experimental analysis such as finite element method, strain gage method and real structure testing. In this paper, the sterss distribution in a diaphragm is analysed by photoelastic experiment and real structural photoplastic experiment, and the effects of diaphragm thickness, reinforced rib, shape of reiforced rib and notch on the corner of diaphragm on the stress distribution over the diaphragm is reported.

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In the present paper, the fundamental stresses of the arch type tunnel and its boundary condition governing the elastic theory of curved beam whose stress distribution is assumed to obey Bernoulli-Navier's hypothesis are studied in case when especially the earth pressure applied to the tunnel linearly varying in the depth direction of the tunnel is considered. As the results, it is clarified that above method generally can be obtained for axial compression, shear force, bending moment, angle of deflection, and deflection. Good agreement was also obtained between photoelastic stress analysis results and the present theory.

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