In this study, we investigate systematically stress intensity factors KI, KII and KIII of the kinds of three mode for a hollow cylindrical bar with three dimensionally inclined crack. Experiments were Performed on the effect of the artificial inclined crack angle φ degree. These inclined cracks in circumferential direction are put in the surface of a hollow cylindrical bar made by the epoxy resin.
Experimental methods of stress intensity factors were proposed as the suitable methods, that was a combined method of the caustic and photoelastic stress freezing method. The mixed mode of KI and KII were determined by photoelastic method of SANFORDS (classical approach) combining with the FORTRAN language of Takahashi and Nogata in the used smallest square method.

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This paper describes stress concentration and distribution on a branch pipe subjected to an in-plane bending moment, as investigated using the photoelastic stress freezing method and also using the Finite Element Method (F.E.M.). We demonstrated the relationship between these factors and the stress concentration factor, and the following facts were ascertained from the experiments. (1) Chamfering wall at the intersectional resulted in a significant decrease in hoop stress at the inner edge. Thus it is recommended to relax the hoop stress, especially in the inner wall. The optimum value is 25%. (2) The ratio of the fillet curvature to the subject pipe diameter appears to affect the fiber stress at the outer wall. In terms of safety, the design of the branch pipe should take the photoelastic result into account. The best optimum value for the ratio is 20%. (3) There was a high stress concentration area at the side near to the branch in all models. From the nature of the branch pipe, we cannot avoid the change in the wall thickness at the intersection but at least we can reduce it by chamfering the inner edge of the area, as mentioned above.

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Centrifugal stress of axial flow cooling fan for high speed compact electric motor is measured by the photoelastical stress frozen method, and also distribution of the bending stress of the fan blade is measured by the method of double layer. Nodes of the natural frequencies of the blade are compared with the distribution bending stress. And also residual stress of the torsional stress of the blade is measured by the method of stress annealing technology. The results of these experiments are centrifugal stress does not reach the limitation of the material allowance, natural frequencies of the fan blade will increase the bending stress, and residual stress is not so large to effect to the torsional area of the fan blade. These results are applicable to the data of designing for the rotating disk with slits.

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The automatic measurement of the total relative phase retardation (ρ_itol) of a photoelastic model is performed in the whole field by using the linearly polarized light at three different wavelengths of monochromatic light. The relative phase retardation (ρ_i) at each wavelength λ_i is obtained from Stokes parameters without the influence of the isoclinic angle. The measurement range of the model can be more widely taken compared with a two-wavelength method. The ρ_itol was calculated by the coincident method using ρ₁, ρ₂ and ρ₃. In the experiment of the circular disk under compression, the ρ_itol in the rang 0-5π agreed well with the theoretical values.

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The mixed mode stress intensity factors for the corner cracks of stepped plate and round bar subjected to bending load are evaluated by means of photoelastic experiment. The stepped plate models are made by machining the epoxy resin plate. The stepped round bar models are completed by machining the epoxy resin round bar without step using a turning machine. The cracks with systematically varied form factors are machined with the diamond disk saw at the corner of steps. The plate models are loaded by pure in-plane bending, and the round bar models are loaded by means of the apparatus made to give pure bending in electric furnace.
The isochromatic fringe patterns are taken by a CCD camera, and recorded in the magneto optical disk. From the thinning images of them obtained by utilizing the image processing analyzer, the required data are collected for the following analysis, and the mixed mode stress intensity factors are estimated by personal computer using the program based on the over-deterministic methodh.
The obtained mixed mode stress intensity factors and the effective stress intensity factors are summarized in lots of diagrams shown as the behavior depending on the form factors of models.

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The authors have previously proposed a basic method for multiplying the original isochromatics obtained from a photoelastic experiment and extracting the isochromatics using the original- or multiplied-isochromatic image. In this study, the method is applied to isochromatics obtained using the color photoelastic coating method. The method uses R, G and B fringes, which are taken using a color CCD camera in dark- and light-field circular polariscopes with a white light. The light intensities in the dark-field image are subtracted from those in the light-field image, and the points with zero values are extracted. The fringe orders are assigned to the extracted isochromatics using calibration curves, which shows the relationships between the fringe orders obtained using a single wavelength and those using R, G and B filters in the CCD camera. The method is applied to isochromatics obtained in an aluminum T-shaped plate subjected to a bending load. As a result, continuous isochromatics with a width of one pixel increased by 2, 4 and 6 times are accurately extracted.

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In this paper, mixed-mode static and dynamic stress intensity factors of different phase plastics were determined by using photoelastic and caustics methods. Specimens were composed by bonding between epoxy resin, PMMA and polycarbonate by epoxy bond. Upper materials of specimens were epoxy resin, PMMA and polycarbonate. Lower materials were polycarbonate with inclined V notch for all. Angle of V notches was 45 degree. As the result of this experiment, stress intensity factor of different phase plastics was lower than non-interface specimen. It is clear that crack tips influenced these interfaces and mechanical properties of upper phase materials. In dynamic behavior, each specimen showed a similar tendency up to 250μs. Dynamic stress intensity factor increase became less at 250μs, and afterwards became more. And cracks were propagated at t=500μs for interface, next reached interface and became interface crack.

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