In this paper, we present a shape optimization method for the natural vibration problem of thin-walled or shell structures with or without sitiffeners. The boundary shapes of a shell or stiffeners are determined under the condition where the boundary is movable in the in-plane direction to the surface. The design problems deal with eigenvalue maximization problem and volume minimization problem, which are subject to a volume constraint and an eigenvalue constraint respectively. The both optimization problems are formulated as distributed-parameter shape optimization problems, and the shape gradient functions are derived using the material derivative method and the adjoint variable method. The optimal free-boundary shapes are obtained by applying the derived shape gradient functions to the H¹ gradient method for shells, which is a parameter-free shape optimization method proposed by one of the authors. Several design examples are presented to validate the proposed method and demonstrate its practical utility.

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We have proposed a calculation method for predicting the master curve corresponding to dynamic viscoelastic measurement results of rubber obtained under experimental conditions with temperature variance and constant frequency. Our methodology consists of a calculation method based on linear-viscoelastic theory, which makes it possible to predict the master curve for the storage modulus using the relation between frequency and loss modulus. To investigate the method's effectiveness and stability, we applied it to the experimental results for two material types: carbon-black-filled SBR (SBR/CB) with a volume fraction of 25% and silica-filled SBR (SBR/Silica) with a volume fraction of 20%. These results verified that this method's predictive performance is good and that the stability of the calculated results is excellent.

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To discuss an effect of stress ratio and loading mode on high cycle fatigue performances of extruded magnesium alloys, axial loading fatigue tests under three conditions of stress ratio, R, of 0, -1 and -1.5, and also rotating bending fatigue tests have been performed in laboratory air at room temperature using hourglass shaped specimens of AZ31, AZ61, AZ80 and T5-treated AZ80 alloy. Specimens tested under R=-1 and -1.5 showed a stepwise S-N curve on which two knees appear except R=-1.5 of AZ31, while under the test of R=0 clear fatigue limit existed on the S-N diagram. As the result of rotating bending fatigue test, a stepwise S-N curve occurred on the specimen of AZ80 and AZ80T5 and continuous S-N curve appeared on AZ31 and AZ61. It became clear experimentally that a shape of S-N diagram depended on a kind of tested materials, applied stress ratio and loading mode. From the detail observation of fracture surface, it was suggested that fatigue crack initiation mechanism changed from a twin-induced failure mode at high stress amplitude level to a slip-induced one at low stress amplitude level. This transition was determined with the relation between the minimum stress during a fatigue cycle and the compressive yield stress at which deformation twin occurred. Experimental relationship between the fatigue strength and static mechanical properties of tested materials was discussed in this study.

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In a growth prediction for fitness-for-service assessment, mechanical interaction between multiple cracks was considered by assuming a coalescence of interacting cracks. The current coalescence rule for crack growth prediction is prescribed for interacting two cracks and the effect of size difference is not taken into account. No rule is provided for cracks of more than three and it was pointed out that the current rule is overly conservative. In this study, the coalescence criterion (N-criterion), which has been developed for two cracks of different size, was applied to the multiple cracks. The S-version finite element method was employed to simulate the crack growth behavior under interaction. It was shown that the growth of three cracks could be predicted conservatively by applying the N-criterion. For applying the N-criterion to three cracks, however, the small crack has to be treated properly when the crack was judged to stop growing. Furthermore, it was pointed out that the relative position between multiple cracks should be modeled with care when cracks were coalesced. The detailed procedure for the growth prediction was shown and its validity was shown by predicting the growth of six cracks, which was observed in an actual plant. The proposed procedure could predict the growth of interacting multiple cracks conservatively.

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Since solar energy is nonpolluting and will not be depleted, the development and spread of concentrating solar power technology have been promoting. The study and development of new energies have been also promoting in Miyazaki prefecture. The research project team in faculty of engineering, University of Miyazaki continues to work on study and development of solar energy technologies by making use of Beam-down Solar Concentrator. In the present study, a flat compound plate composed of different kinds of materials is considered in order to examine the heat transfer characteristic and strength at elevated temperature of flat type receiver in which concentrated sunlight is converted to thermal energy. The analytical development of heat conduction and thermal stresses for the compound plate is treated. Then, effects of materials and thickness on the temperature and thermal stresses in the plate are discussed from the theoretical point of view.

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Embedded Flaw Repair technique has been developed in JSME S NA-1. The technique is applied to prevent propagation of Stress Corrosion Crack (SCC). The welding metal with high corrosion resistance is embedded on the surface of component, and could protect cracking part from the aggressive primary water. In this method, the crack is not fully removed from the component. After discussion in JSME, inspection rules after application of Embedded Flaw Repair were established for penetrations of Class 1 vessel's penetration (for example, reactor vessel head penetration and bottom mounted instrument in PWR) and reactor internal components. The focus of discussion is placed on whether the flaw should be monitored by nondestructive inspection. This document describes the technical aspects that JSME code committee studied, such as, flaw evaluation, tolerance of components with defects, inspectability of defects in seal-welded components and the operating experiences of repaired components at U.S. plants. Finally, in-service inspection items for a component repaired by Embedded flaw technique are proposed.

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This study examined the shrinkage stress of a light-cured composite resin on cavity wall experimentally and analytically. The shrinkage force was measured using artificial cylindrical cavities fabricated in two stainless steel plates and a load-cell attached to the steel plate. An analytical model was introduced to evaluate the stress distribution in the cavities and to compare the shrinkage force experimentally determined, and following results were obtained: (1) The shrinkage force was dependent on both the cavity depth and irradiation time of the resin. (2) The analytical model can predict all the important features of the shrinkage force. (3) The stress on the cavity wall was dependent on the irradiation time.

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