High-temperature tensile load-bearing capacity of unidirectional continuous-fibre composites: significance of a specimen-end effect

A specimen-end effect which is of significance for the determination of high-temperature tensile load-bearing capacity of metal-matrix composites reinforced with continuous metal fibres has been indicated. The effect arises from the fact that differential axial straining of the fibre and matrix can occur at high temperatures due to viscous sliding at the fibre-matrix interface. A model-system study has been carried out using a tungsten fibre-copper composite, whose ultimate tensile stress (UTS) at temperatures up to 1000° C is determined indirectly from four-point bending data as well as directly from tensile test results. It is found that at temperatures above 0.6 of the matrix homologous temperature the UTS thus determined has much smaller values than those estimated on the basis of a simple rule-of-mixtures equation. Significance of the result is discussed in terms of potential turbine-blade applications of heat-resistant metal-matrix composites, such as tungsten fibre-reinforced superalloys.     

Investigation on Static Stability of Sheet Pile Quay Wall Improved by Cement Treated Sea-Side Ground from Centrifuge Model Tests

The static stability of sheet pile quay walls on a thick clay deposit against horizontal loads was studied through a series of centrifuge model tests. In the tests, an overconsolidated Kaolin clay layer was prepared over a layer of dense Toyoura sand in a rectangular container. The model quay wall was set to the bottom of the sand layer. The sea-side area adjacent to the quay wall was improved with cement-treated Kawasaki clay. Under 50 g centrifugal acceleration, the clay deposit was consolidated and horizontal line loads of about 0 to 70 kN/m were applied to the quay wall. The width and the depth of the improved area were varied and its performance was compared with that of a quay wall embedded in unimproved ground. Results of the study indicated that the improved ground provided significant resistance against horizontal loading. In addition, a numerical model to estimate the mechanical behavior of the sheet pile quay wall is presented. The outcomes of the numerical model show good agreement with the centrifuge test results.     

A novel technique to synthesize buserite-type manganese oxide thin film

Buserite-type layered magnesium manganese oxide has been prepared in a thin film form by means of the combination of electrochemical and ion-exchange processes. Mg²⁺ ions between the layers of buserite are stable toward ion-exchange with monovalent cations in solution while they can be excluded electrochemically for charge-compensation upon oxidation.     

A fast market splitting matching method for the spot electric power market

A fast, innovative matching method for the spot power market, considering network constraints, has been developed. In this method, buy and sell order bids are respectively divided into the aggregated volume of several band prices. Then, the aggregated volume and the center of each band price are used to calculate an index band clearing price, which contains the real clearing price. The division and calculation process is iterated until the band price is less than the tick size of the bidding price. This method is applied to a real problem in the Japan power market, with 9 bidding areas, 10 area‐connecting lines, and 9000 orders (volume/price pairs). Numerical simulation results show that the new method is ten times faster than conventional linear programming, demonstrating the effectiveness of this method. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(4): 21–29, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20694     

Balancing material selection and inspection requirements in structural design of fast breeder reactors based on “System Based Code” concept

The System Based Code concept proposed by Asada et al. [Asada, Y., Tashimo, M., Ueta, M., 2002a. System Based Code—Principal Concept. Proc. ICONE10, 22730; Asada, Y., Tashimo, M., Ueta, M., 2002b. System Based Code—Basic Structure. Proc. ICONE10, 22731] intends to realize margin exchange, in order to optimize design. This paper presents preliminary calculation of margin exchange between material strength and the accuracy and frequency of inservice inspection (ISI), taking a reactor vessel of a fast breeder reactor, of which dominant failure mode is creep-fatigue, as an example. The original design is a structure of forged rings of 316FR, material with superior creep strength. Alternative designs use either Type 304 stainless steel or welded structure of 316FR plates, leading to increased failure probability compared to the original design. The accuracy and frequency necessary to compensate this increase of failure probability was estimated. Results envisioned margin exchange between material strength and ISI under practical conditions. Sophistication of the procedure to calculate failure probability will ensure the application of the concept of margin exchange to practical design.     

Practical method to determine the filter shape function used in the three-dimensional Fourier filtering method

The procedure to determine the appropriate filter shape function used in the three-dimensional Fourier filtering method (3D-FFM) is discussed from a practical point of view, so as to reduce the artificial contrast induced by the processing and to achieve a high signal-to-noise ratio. The effects of cutting off the high spatial frequency of the filter shape function and damping at low spatial frequency were investigated by using through-focus images of a gold (110) thin film. In addition, the effect of the width of the filtered area was discussed using through-focus images of a carbon nanotube. For reliable image processing, the filter shape function should be cut off beyond the information limit and attenuated with damping at low spatial frequency. Furthermore, the extraction area should include the distributed area of the relevant structural components appearing in the 3-D Fourier spectrum.     

Seismic design method of clamped-free thin cylindrical shells immersed in fluid

We carried out excitation experiments on clamped-free thin cylindrical shells immersed in fluid that represented thermal baffles of a fast breeder reactor. At a certain excitation level, occurred external pressure buckling. We also observed that parametric vibration, which involved high-order circumferential vibration modes, occurred at a certain combination of excitation frequency and excitation level. Concerning seismic design of the thermal baffles, we, therefore, take not only the buckling but also the effect of the parametric vibration into consideration. We adopt buckling eigenvalue analyses to estimate buckling pressure and propose a formula to prevent the buckling. Further, we discuss important factors such as buckling strength reduction caused by initial shape imperfections and interaction between horizontal and vertical seismic response. Concerning the parametric vibration, a significant deformation of cylinders should be prevented. A practical method applying the dynamic stability theory is proposed to obtain the condition, under which the parametric vibration takes place.     

Laminar combined convection heat transfer of liquid sodium flowing through a single horizontal row of cooling tubes in the direction of gravity

The laminar combined convection heat transfer of the liquid sodium which flows through a single horizontal row of cooling tubes in the direction of gravity are studied using numerical analysis. The heat transfer characteristics at large Reynolds numbers are improved when Richardson numbers (= GR/Re²) are increased and the improvement rate is enlarged with an increase in value. The temperature field at small Reynolds numbers does not exhibit much change even when the Richardson number reaches a high value. Consequently the Nusselt numbers do not differ from those of forced convection. In other words, in a decay heat removal system at a low velocity, there is a possibility that an improvement in the heat transfer characteristics by combined convection cannot be expected even in a system with a large Richardson number.