The instant distributions of plastic strain in carbon steel Sharpy Test Pieces during impact have been investigated using the photoelastic coating method and a high speed recording technique. Color photoelastic patterns in the coating film which relate to the difference of plastic principal strain ∈₁-∈₂ were satisfactorily taken at various stage of impact of the test pieces by a delay-Xenon-micro-flash system with a resolving power of about 2/1, 000, 000sec. The results obtained show that the plastic strain energy absorbed in the test piece is notably localized to and concentrated in the two regions of the contact point of the hammer and the bottom of the notch at which cracks usually originate. The test pieces used were made of 0.25% carbon steel and were shaped according to the Sharpy impact test piece with a U-notch-JIS No. 3.

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The stress, strain-rate and velocity distributions in the viscous flow with an obstacle by rotating in the channel were analyzed using the photoviscous method. The rotating obstacles used in the present experiment were a rotating cylinder and agitating blades having two or four blades. And the stress distribution in the obstacle by rotating in the viscous flow was analyzed, too.

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Formerly in the photoelastic experiments, indistinct isoclinic lines had to be applied in order to resolve the stresses in axi-symmetrical problem. The problem of axi-symmetrical stresses can be analyzed by the scattered light photoelasticity. This method need to obtain a stress equilibrium equation and three scattered isochromatic fringe patterns by three different incidences of polarized light beam. For the purpose of checking the accuracy of this experimental method, an author performed the stress analysis of a round shaft with a semi-circular groove under the room-temperature tensile loading, and also an author developed the epoxy resin of a new photoelastic material. This material had almost no initial stress and photoelastic stress sensitivity of this material was higher value. As a result, it was proved that this technique led to a higher accuracy of the experimental stress analysis.

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Photoelastic experiments employing stress freezing technique were performed to determine mixed mcde Stress-intensity Factors K_I and K_II of edge cracked strips subjected to uniaxial tensile loading and out plane bending separately. By plotting of normalized apparent SIF vs. square root of normalized distance from the crack tip on the base of isochromatic fringe patterns in the restricted region around a crack tip, the values of these corresponding SIF were obtained. The determined SIF values of tensile specimen in stress frozen state were shown to agree reasonably compare with the complete two dimensional solution in consideration of three dimensional effect. The bending tests were conducted on four strips containing edge cracks inclined to each different direction. Every piece of slices parallel to these strips taken. out from these stress frozen strips was researched following the same photoelastic procedure as described above using multiple fringe photographs. As the results, the variations of tilt angle θ_m in fringe pattern, values of K_I, K_II and its ratio correspond to each depth of these strips formed by different crack angle were presented.

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Stress analysis was made through photoelastic model tests to determine the optimum shapes of hull structural members such as fillet part of cross tie in transverse webs and bracket toe end in longitudinal stiffeners. The stress distribution of hull structural members derived from photoelastic model test were compared with the results theoretically obtained by means of finite element analysis. By comparing these experimental and theoretical results, we found that the epoxy resin model was applicable for the determination of the stress distribution and stress concentration in complex structural members.

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Three-point bending fracture behaviours in central transverse impact of epoxy- and DAP-beams with sharp or blunt notch are analyzed by high speed photoelasticity using a multiple spark gap high speed camera. Dynamic stress intensity factors are obtained from the beginning of impact to the initiation of fracture and also in crack propagating period, and the character of impact fracture is discussed.

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