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Article type: Cover
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Published: December 30, 1985
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Article type: Index
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Published: December 30, 1985
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Article type: Appendix
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Yasushi HIGO
Article type: Article
Pages
1-9
Published: December 30, 1985
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In this paper, the non-linear hydrodynamic forces acting on a rectangular cylinder are studied. The rectangular cylinder is heavig with a large amplitude in the vicinity of the free surface. The first-second-and third-order experimental results are com-pared with the corresponding calculated results. The procedure of the calculation is based on the theory where the free surface elevation is assumed small. It is also assumed that the interval of impulsive motions are small enough, so that the impulse response function can be used in the same manner as the previous report (1). It is found through experiments that flow patterns of the flood on the rectangular cylinder caused by its heaving motion are singnificant. The calculations where the flood effects are taken into account show good results.
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Isao NEKI, Hideaki TATAMI
Article type: Article
Pages
11-17
Published: December 30, 1985
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The boundary element method (BEM) is the method of numerical analysis containing some merits, i.e. reducting the number of data and the calculation time, compared with the finite element method (FEM). In the analysis of two-dimensional elastic problem, BEM is already applied and many papers are published. In the practical, the stiffeners exist on the boundary of most two-dimensional elastic problems, but the anallyzing method was not investigated in the past. In this paper, the authors developed the analyzing method of two-dimensional elastic problem having stiffeners on the boundary, and new element, i.e. non-conforming double nodes element. Further, the authors investigated the accuracy of the above method and new element comparing with the former conforming element and FEM in the two-dimen-sional membrane plate, and applied this method to the practical problem of calculating the stress around slot of longitudinal, and confirmed the satisfactory results.
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Junkichi YAGI, Toshihiko FUNAKI, Yoshitaka YANO, Inhen KOH
Article type: Article
Pages
19-29
Published: December 30, 1985
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The catamaran ship has twin hulls and a connecting desk. Stiffness of the deck is generally very small compared with that of each hull. Therefore, to analyze motions of ocean going catamaran ship in waves, effect of elastic deformation of the deck can not be neglected. In the 1st report, considering forces and moments acting in the connecting deck induced by the relative motions of the twin hulls, motions of each hull in waves were analyzed. And it was found that loads acting in the deck due to relative motions of the twin hulls became largest in the transverse waves and effect of hydrodynamic interaction between twin hulls could not be neglected. In the 2nd report, considering the hydrodynamic interaction between twin hulls and the elastic deformation of the deck, motions of each hull in the transverse and oblique waves were analyzed and the loads acting in the deck due to relative motions of the twin hulls were investigated. The connecting deck is acted by two kinds of wave induced stresses. The one is the stress by elastic deformation of the deck due to relative motions of the twin hulls. The other is the stress by elastic deformation of hull structure and the deck due to dynamic pressure and inertia force acting on the ship induced by motions of the twin hulls in the waves. In this report, those wave induced stresses acting in the deck were analyzed and effect of scantling and stiffness of the connecting deck and the twin hulls on the stresses in the deck were investigated.
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Yoshikazu MATSUURA, Kouhei MATSUMOTO, Mitsuru MIZUUCHI, Kenji ARIMA, H ...
Article type: Article
Pages
31-41
Published: December 30, 1985
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This paper deals with the U-type hydrodynamic vibration damper (it is called 'U-type HVD' here) and the spring and hydrodynamic type dynamic damper (it is called 'SH-type DD') for reducing ship vibration. The former damper was developed by the NPL, and the latter one was devised by the authors. The damper effect of two kinds of the dynamic dampers was investigated experimentally and theoretically. The authors obtained the follwing conclusion. (1) The U-type HVD has the higher natural frequency, the lower is its air room height or free surface height. (2) The SH-type DD has two natural frequencies, in which the first order natural frequency originates from the coil spring vibration system, and the second one is from the air water vibration system. (3) The natural vibration of the SH-type DD can be analysed theoretically by using equivalent vibration model with two degree of freedom. (4) The authors obtained theoretical results of damper effect of hydro-dynamic dampers, which agrees with experimentl results, using the energy method.
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Yoichiro OKAMURA, Ryutaro NAKAGUMA
Article type: Article
Pages
43-48
Published: December 30, 1985
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In the previous paper, the relation between the fatigue strength based on crack initiation life N_c and the stress concentration factor K_t and the elastic stress gradient G was clarified in the case of large values of K_t. In this paper, to investigate the effect of K_t and G on the fatigue strength of N_c-basis in the case of small values of K_t, the repeated tensile fatigue tests for SS41 steel plates are carried out in intermediate cycle range. From the test results, the following conclusions are obtained. (1) The relation between the fatigue strength reduction factor of N_c-basis, K_f and K_t for relatively small values of K_t is approximately expressed as the linear function under constant values of N_c and G, which satisfies K_f=1 for K_t=1. (2) From above results, the empirical formula giving K_f, for relatively small values of K_t, is obtained in the following form: [numerical formula] Where d_1, d_2=constants, h_1, h_2=exponents This formula is applied in the extent where G value is not very large. This formula shows good agreement with the results of other researchers in comparatively high cycle range. (3) The size effect factor showing degree of the size effect of notched plates, K_s, for relatively small values of K_t is obtained as a function of G and K_t, i.e., K_s=K_t/K_f.
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[in Japanese]
Article type: Article
Pages
49-53
Published: December 30, 1985
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[in Japanese]
Article type: Article
Pages
55-57
Published: December 30, 1985
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Article type: Appendix
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59-61
Published: December 30, 1985
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Article type: Appendix
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Published: December 30, 1985
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Article type: Appendix
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Published: December 30, 1985
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Article type: Appendix
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Published: December 30, 1985
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Article type: Appendix
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Published: December 30, 1985
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Article type: Appendix
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Published: December 30, 1985
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Article type: Appendix
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Published: December 30, 1985
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Article type: Appendix
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Published: December 30, 1985
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Article type: Cover
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Published: December 30, 1985
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Article type: Cover
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Published: December 30, 1985
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