日本造船学会論文集
Online ISSN : 1884-2070
Print ISSN : 0514-8499
ISSN-L : 0514-8499
2004 巻, 195 号
選択された号の論文の32件中1~32を表示しています
  • 北澤 大輔, 多部田 茂, 木下 嗣基, 藤野 正隆, 加藤 孝義, 佐々木 啓, 井梅 俊行
    2004 年 2004 巻 195 号 p. 1-13
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Blue mussels on a floating structure filter a lot of suspended particles in the ambient seawater. They also consume oxygen and release nutrients in their respiration and excretion. These activities of blue mussels may cause water quality to change, so the impacts of them on the surrounding environment should be assessed before construction of the floating structure. To predict quantitatively the change in the pelagic environment, numerical simulation by means of a model of blue mussels is one of the powerful tools. The model contains several parameters such as the relative filtration and respiration rates, whose numerical values should be determined appropriately. To obtain the numerical values of the parameters, decreasing rates of chlorophyll-a and dissolved oxygen are measured in the real sea, instead of determining them from the experimental results in the laboratory. As a result, decreasing rate of chlorophyll-a does not correspond to the concentration of chlorophyll-a around the blue mussels because the filtration of them is limited by low levels of salinity and dissolved oxygen. On the other hand, decreasing rate of dissolved oxygen generally agrees with the amount of dissolved oxygen in the seawater. Then the model of blue mussels is improved using the experimental results. Consequently, it is revealed that the numerical values of the relative filtration and respiration rates are getting larger and larger with increase in water temperature, and they change drastically at the salinity of 12-16 psu. Further, changes in these rates due to water temperature and salinity can be described well using the exponential and switch functions, respectively.
  • 千賀 英敬, 洪 龍杓, 吉松 隆行, 小寺山 亘
    2004 年 2004 巻 195 号 p. 15-23
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    A numerical simulation scheme has been developed for the vortex induced vibration response of flexible risers and has been validated by experimental results. In the experiments, a riser model was forced to surge by fixing the top end of the model to a forced oscillating apparatus in an experimental towing tank. To measure the three-dimensional motion of the model, six CCD cameras were used for each direction, horizontal and vertical. A numerical simulation scheme for three-dimensional dynamics of the flexible risers considering the VIV effects has been developed which is based on the ‘Hamilton's principle’and mode expansion method. The numerical simulation method was validated by comparing with experimental results and showed a good agreement.
  • その3 海面におけるマイクロ波散乱の数値シミュレーション
    林 昌奎, 小林 豪毅
    2004 年 2004 巻 195 号 p. 25-31
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    The basic principle of the sea surface measurement by active microwave remote sensing is the difference in microwave backscatter by the sea surface conditions. In order to develop more advanced measurement, it is necessary to understand the mechanism of microwave scattering at the sea surface in detail. This phenomenon consists of two physical processes. One is the formation of the sea surface by the composite action of wind, waves and currents, and the other is microwave scattering at that surface. This paper describes the analysis of the latter process by numerical simulation. The moment method that has been used for the antenna analysis is applied to the scattering problem at the irregular surface in recent years. In this research, the statistical characteristics of microwave scattering at the sea surface are analyzed by Monte Carlo simulation of the moment method. If only ripples exist at the sea surface, scattering coefficients calculated by the Bragg scattering theory and the physical optics (Kirchhoff approximation) are close to numerical results. Also in the case of the general sea surface, the influence of long gravity waves to the average backscattering coefficient is relatively small. This result assures that it is not necessary to take the influence of long gravity waves into account in the observation algorism of the wind.
  • 佐藤 徹, 吉川 拓郎, 斉藤 周, 土屋 好寛
    2004 年 2004 巻 195 号 p. 33-42
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    There is a discussion on the relation between Isahaya Dyke and the recent environmental change in Ariake Bay, which may devastate the Noni crop and exterminate shellfish. On the other hand, some say that the recent tidal decay in the outer sea is the main cause of the change in tidal current in Ariake Bay. Whatever the cause is, some ways to improve water quality are urgently needed even if they are local and temporal. We proposed a local engineering solution, a kind of seawater-quality enhancer, and simulated numerically and experimentally the diffusion of nutrient-rich water emitted by the apparatus. It is shown that 1-3% of the emitted water keeps to remain on the euphotic layer in Isahaya Inlet for a couple of weeks. This may imply the possibility of improvement of water quality by this engineering countermeasure.
  • 松倉 洋史, 勝原 光治郎, 渋谷 理, 久保 登, 小林 充
    2004 年 2004 巻 195 号 p. 43-51
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Enterprises compete keenly against domestic and foreign companies. They are under strong pressure to reduce physical distribution cost to survive the competition. Major inter-business methods to achieve it are accommodation, joint ship allocation, and as their ultimate form, companies merger. But in physical distribution process a lot of factors, for example means of transport, factories, storage facilities, markets, and other external environment effect each other dynamically. Therefore it is diffcult to evaluate the methods' various effects comprehensively, quantitatively, and accurately. We think the difficulty is one of major obstacles to improve the distribution systems. This paper deals with domestic maritime cement transportation as an example. First, we develop compute simulation of physical distribution routine. Secondly, we model industry cooperation of logistics and develop ship allocation algorism and effects estimation system. Lastly, we execute several case-studies and discuss the cooperation's effects on logistics.
  • 安藤 英幸, 大和 裕幸, 中野 知彦, 増田 宏
    2004 年 2004 巻 195 号 p. 53-61
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    In this paper, we propose a method for analyzing failure reports written in natural language. We introduce text coding methodology, which is mainly used in the field of sociology. Although this methodology is useful to improve the reliability of analysis, it is very costly and tedious work to assign codes to a large amount of sentences. Therefore, we introduce two methods to support coding work. One method is the clustering of sentences in failure reports. This clustering method supports users to generate adequate codes as the metric of failure reports and to systematize them. The other is a rule-based code assignment method, which correctly handles synonymous words and conceptually similar words using the ontology of failure reports. We applied our coding methods to nearly one thousand reports and analyzed their failure status. The result shows our system is promising to realize the reliable failure analysis.
  • 安藤 英幸, 大和 裕幸, 角田 領
    2004 年 2004 巻 195 号 p. 63-70
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    For reducing human errors in navigating ships, crews on a bridge must cooperate. To understand how the cooperation is conducted is necessary for improving trainings and manuals. We apply three types of discourse analysis, quantitative analysis, qualitative analysis and sequence analysis. We developed information systems, named CORAS (COoperation Record and Analyze System.), to support these analyses. CORAS manages several types of time-series data, which includes video, audio, environment data and trainers' evaluations. By using CORAS, we analyze two simulator trainings and reveal a dynamic mechanism of team cooperation.
  • コンテナ流動量に応じた Discount の設定を通じて
    Hasanbasri Mursyid, 小瀬 邦冶, 安川 宏紀, 佐野 将昭
    2004 年 2004 巻 195 号 p. 71-78
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Nowadays marine transportation system has been demonstrated as a dominant support for global economy and there has been so severe competition among ports and shipping industries. To take economies of scale into consideration, there has been a remarkable growth of ship sizes. The resulting massive flow has reduced unit-shipping cost. However, it has increased the cost in port as a dominant part of the total cost. Hence, discount policy in port cost is worth to note.
    In this paper a genetic algorithm-based analysis is conducted for marine transportation network that consider discount model for port-related charge. In this discount model, discount rate is a function of bundled flows in the interhub links, which are characterized by non-linearity and thus is hard to solve. The result shows that bundled flows tend to several big hub ports and results in reduced total cost for the entire network system.
  • 中住 昭吾, 鈴木 克幸, 大坪 英臣
    2004 年 2004 巻 195 号 p. 79-86
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    In this paper, a new approach to crack propagation analysis for large-scale or complicated geometry structures is presented. That is the connection of mesh superposition method and extended finite element method. In the former technique, two types of meshes are used and displacement is represented as the sum of them. And in the latter technique, discontinuity across the crack segment and singularity around the crack tips are represented in the approximation by enriching the nodal degrees. This technique does not require meshes to conform to the crack geometry. This enables crack propagation procedure with no re-meshing process. By using this approach, some numerical examples are presented.
  • 佐々木 健
    2004 年 2004 巻 195 号 p. 87-93
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    The present paper proposes a method to classify objects' surfaces by analyzing relative spectrum of an ultrasonic echo with respect to the spectrum of an echo from a flat plane. Time-of-flight is obtained from linear phase shift between the reference echo and the echo from the object. Distance between two planes separated along longitudinal direction is obtained from frequency dips in the echo spectrum. Surface features such as an edge of a prism can be recognized by a decrease of power in higher frequencies and constant phase shift with respect to the reference echo. It is also shown that phase spectrum is useful for determining arrival time of an echo coming from an oblique surface with respect to the center axis. The theoretical analysis and some experimental data are presented.
  • (第1報) パイプユニット組立への適用
    奥本 泰久, 比翼 謙太郎, 鈴木 長生, 井関 隆太郎
    2004 年 2004 巻 195 号 p. 95-101
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    This paper introduces the outline of the digital manufacturing in shipbuilding and the application results of it, with the aim of the modernization of ship manufacturing, following the application of shipbuilding CIM. The pipe unit assembly in a shipyard was taken up as an example, because the assembly work has depended on individual experience of skilled workers, and not been generalized and digitized. As a result of the work analysis in the site, it was found that the assembly worker often moves to observe the drawing plan to image the final feature of the assembly unit even veteran workers. Hence, the assembly simulation program was developed and a PC was introduced in the site, so as to assemble the pipe unit in accordance with the computer simulation on the display. The method was effectively tested and verified in the site. In addition, the wearable computer system was applied in a pipe factory to check the delivered pipes, to sort them, and to allot them to the pallets. These applications were confirmed as one of the effective digital manufacturing system.
  • 第七報 ニューラルネットワークを使った荷物持上げ時の身体負荷解析
    奥本 泰久, 東野 雅弘
    2004 年 2004 巻 195 号 p. 103-109
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Lifting work is frequently observed in the production site of shipbuilding companies. It seems to be the work in which the body burden is bigger, and it often causes low back pain and injury of knee for aged shipbuilding workers. The low back pain concerns the compressive force on intervertebral disks, while the injury of knee concerns torque on the joint of knee. The analysis of such force and torque during the lifting job can be carried out using the biomechanical analysis, however, the calculation is usually complex and needs special know-how. Hence, the neural network method was applied in this paper to obtain the low back compression force (force on intervertebral disks) and torque on knee by developing C language program. The original teaching data were provided by the simulation using general-purpose software “Jack” applying virtual human model, and the neural network model learned these teaching data. Then, it was compared with the analytical results of “Jack” for the low back compression force and torque on knee, and both data obtained from the neural network and “Jack” were well coincided. Hence, the low back compression force and torque on knee at lifting work can be approximately gained by this neural network model without applying human software “Jack”.
  • 大和 裕幸, 安藤 英幸, 唐澤 武郎, 内藤 紀彦
    2004 年 2004 巻 195 号 p. 111-122
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Authors have developed a CAD system with the design support by the Semantic Web and workflow. The system aims to support designers by retrieving the appropriate knowledge by documents, data and so forth with the semantic web and also by giving the design guide with the workflow system. The system has been extended to support the ship basic design from the decision of principal particulars to the hydrostatic characteristic. As for the core CAD system, the TRIBON is employed in this paper. The proposed system shows the effectiveness and efficiency for the ship basic design by illustrating an example practice of design scenario of a bulk carrier.
  • 増田 宏, 吉岡 康博, 和田 顕男, 大和 裕幸
    2004 年 2004 巻 195 号 p. 123-129
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    In developing large-scale products, it is important to review the design of products from multiple perspectives and to prevent inconsistency in design. Web-based information sharing is very promising for realizing efficient design reviews. In this paper, we propose a design review system based on 3D models shared on the Web. We call comments and locations defined on a 3D model as annotations. In our system, annotations on 3D models are stored in a client-server framework, and can be shared among the design team. We propose four types of annotation methods, which consist of billboards, direct 3D painting, 2D drawing on a snapshot, and feature extraction. Since all of them are defined using 2D strokes and transformation matrices, they can be very easily and interactively specified by reviewers. These annotated regions are associated with comments, and are shared by designers through network. We implemented our review system and applied it to 3D models represented in the VRML format.
  • 青山 和浩, 古賀 毅, 武市 祥司, 野本 敏治
    2004 年 2004 巻 195 号 p. 131-139
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    In order to carry out manufacturing operations more safely, it is necessary to acquire the safety information at the manufacturing planning stage. With the development and spread of IT in recent years, the database of various industrial accident examples is built in a company and the environment which can easily browse and share industrial accident example data is developed using computer networks. However, it is very difficult to acquire the appropriate safety information considering the industrial accident cases relevant to the assembly operations.
    This paper proposes a framework of information system for safety management, by assessing the risk of accident and the cost of safety. In this system, a database of industrial accident cases is introduced and integrated with the virtual assembly simulation. A planner of safety management can make the scenario of assembly operations using the virtual assembly simulation, and get hazards from simulations. Then, the system checks each case of accident using the database and show alternative measures for accidents with the value of risks and costs. He/She can interactively select appropriate measures and the system can show a statement of work to make the assembly operations safer.
  • 村山 英晶, 影山 和郎, 大澤 勇, 鵜沢 潔, 金井 誠, 小川 哲, 今北 明彦, 小野 志郎
    2004 年 2004 巻 195 号 p. 141-150
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    We verified the applicability of a fiber-optic sensor to deformation monitoring of the seal equipped with an air cushion vehicle such as a surface effect ship (SES). The seal is a membrane structure made of an elastomeric material. It is difficult to measure deformation or vibration of the membrane structures by using a sensor which is fixed on it. In laboratory tests, we could measure strain-rate of the seal material subjected to cyclic loading by using the fiber-optic sensor adhered to it. Then, in monitoring tests of a small model of the seal with the sensors, frequency or amplitude of vibration was changed according to the velocity of water flow or the length of the bottom in water. In this paper, we described the results of these tests and showed the good applicability of the fiber-optic sensor to measure the response of membrane structures which have elastomeric properties.
  • (その3) 機関室における熱・煙拡散状態
    鷹尾 潤, 福地 信義, 胡 長洪
    2004 年 2004 巻 195 号 p. 151-161
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    In order to establish the fire safety design of ship engine room, it is important to understand the characteristics of oil pool combustion, the properties of smoke, the conditions of fire spread and smoke movement with heat diffusion. In our previous study, the oil burning experiment was executed to investigate the distinctive features of pool combustion and smoke. And the experimental and numerical analyses of smoke movement were carried out using the 1.2m sized cubic box as a substitute for simplified engine room model.
    In this study, the experiment of smoke movement and diffusion in the 1/15 scale model of engine room with smoke-producing agent was carried out for the fire safety design on fire detection, fire fighting and evacuation. Moreover, a three-dimensional numerical analysis using k-ε based CFD model was performed to investigate the situation of smoke diffusion in an engine room.
    Furthermore, the numerical analyses of smoke and heat diffusion in the full-scale engine room model were executed using the result of oil burning experiment and the numerical method that is already proved the validity to grasp the state of smoke movement. From the interpretation of these results, the phenomena of smoke diffusion in an engine room under several fire conditions can be clarified. By the experiment and the calculation on smoke movement in an engine room, a lot of useful information is obtained for the design of evacuation systems and the arrangements of smoke sensors.
  • 内航コールタール油槽船
    辻本 勝, 武隈 克義
    2004 年 2004 巻 195 号 p. 163-170
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    At the design stage of a ship, the engine output is determined by taking into consideration of a lowering of performance. The lowering is mainly caused by winds, waves, aging deterioration and biological fouling. To keep the speed in actual seas, the output is appended to a proper ratio, which is called sea margin.
    The component of sea margin divides into two groups. One is a weather effect and the other is a deterioration effect which progresses with time. For the estimation of the weather effect, weather forecasting data of 8 years were applied. Also, for the estimation of the deterioration effect, roughness increase of the hull was taken into account.
    In this paper, the desirable sea margin is derived rationally. As an example, for a coastal chemical tanker, Shinko Maru No.28, performance estimation and voyage data analysis were carried out.
    By comparison with the estimated and analyzed sea margin, it made clear that the estimated sea margin agrees with the analyzed one. Consequently the physical meaning of sea margin is explained as a function of wave, wind and time.
  • 村井 基彦, 井上 義行, 武居 弘基, 鴫原 健, 東原 克成, 上下 真史
    2004 年 2004 巻 195 号 p. 171-178
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Very large floating structures (VLFSs) of several kilometers long and wide are now considered as possible alternatives to land-based big facilities such as an airport. Many feasibility studies are now being carried out on the VLFSs and quite a few numerical methods have been proposed for an estimation of a response of the VLFS and a wave field around the VLFS. There are, however, few experiments that can be compared with the numerical results. One of the reasons is that the principal horizontal dimension of the VLFS is so large that the conventional experimental tanks can not comply with the appropriate similarity law. To overcome this difficulty, an attempt is made to carry out experiments in a very small water tank. With the use of the very small tank, an entire wave field around a model or an entire response pattern of the model in waves can be visualized by making use of certain techniques. Such visualization can not be achieved if the conventional water tanks are used.
    In this study, we propose two techniques for visualizing and measuring wave fields which are around 1mm deformations. The first one is based on Moire's method. The second one is based on a picture analysis. Both techniques can fully inform on the very small deformation of the wave fields in widely and in simultaneously. Then we discuss the accuracy of the measurements of the wave fields by comparing with measurements by laser sensors.
  • 山下 誠也, 坂下 晴空, 高橋 徹, 荒見 敦史
    2004 年 2004 巻 195 号 p. 179-184
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Several aspects of the rolling-motion reduction are discussed for a box-shaped floating body. A simplified formula to predict roll responses of the body in beam waves is given. The design philosophy to reduce rolling motion by exploiting the diagram of roll resonant amplitudes, that is derived from the simplified formula, are illustrated for the box-shaped floating body like a FPSO. Subsequently, the characteristics of the rolling motion of the floating bodies with anti-symmetric sections are investigated experimentally. It is proved the anti-symmetric floating bodies reduce the amplitudes of roll extremely for an incidence of beam waves.
  • 三宅 竜二, 溝上 宗二, 小川 剛孝, 朱 庭耀, 熊野 厚
    2004 年 2004 巻 195 号 p. 185-194
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    A comprehensive model test of a latest post-Panamax container ship is carried out in regular waves for various waveheights, wave angles and wavelengths. Six degrees of motions, two shear forces (vertical and horizontal shear forces), three moments (vertical bending moments as well as horizontal bending moments and torsional moments) at three different cross-sections and hydrodynamic pressures acting on 16 locations are measured. Nonlinear characteristics with respect to ship motions and wave loads are discussed in detail with the experimental results and numerical ones computed by a Rankine source method and a strip method. The validity of the Rankine source method and the strip method for various wave loads, especially the torsional moments is detailedly investigated and discussed by comparing the numerical results with the experimental ones. It was confirmed that the Rankine source method estimates torsional moment, which is very smaller than the vertical bending moment as well as horizontal bending moment with good accuracy.
  • 金 岡秀, 浦 環
    2004 年 2004 巻 195 号 p. 195-202
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    This paper presents a numerical solution algorithm for the optimal guidance law of AUV (Autonomous Underwater Vehicle), when it transfers between two predetermined points in the region of environmental flow disturbances. In the formulation of optimal guidance law, position vector of the vehicle relative to the inertial frame is qualified as the state vector, while the vehicle's heading as the input. Optimized sequence of the vehicle's heading is obtained in time domain as the solution of the formulated optimal guidance law. Heading control of AUV using this optimized sequence as the reference completes the optimally guided navigation under the given disturbances. Proposed algorithm is applicable to time-varying flow disturbances as well as time-invariant ones, if only the distributions of them are known a priori. Minimum time guidances followed by the optimal heading tracking control are applied to the navigation of r2D4, which is the latest version of cruising type AUV, developed by IIS, the University of Tokyo. Effectiveness of the optimal guidance shows its primary dependency on the detailed distribution of flow disturbances.
  • 西村 浩二, 平山 次清, 高山 武彦, 平川 嘉昭, 馬 寧
    2004 年 2004 巻 195 号 p. 203-210
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    The authors intend to develop a navigation-warning system for small ship operators in severe sea. In this system, utilizing the wave information from the general marine radar and motion simulation method, ship operator can take the useful information about encountering waves and large ship motion in near future. To accomplish this system, we need to complete the two elements. One is to improve the wave radar, about this we already realize the practical system1), another is to develop the motion simulation method in time domain that can get the results in short time adequately for real time simulation.
    In this paper, we propose a practical simulation method that can calculate the large motion introducing the conventional knowledge based on the linear theory. Additionally some experimental results are shown for validation of numerical method. In conclusion, we present some merits and problems of this method and our future work to improve it.
  • 川村 隆文, 渡辺 貴之, 竹腰 善久, 前田 正二, 山口 一
    2004 年 2004 巻 195 号 p. 211-219
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Applications of CFD to simulation of non-cavitating and cavitating flow around a marine propeller are presented in this paper. The influence of the turbulence model and the grid resolution on the accuracy of the propeller performance prediction has been systematically investigated, and the condition for obtainining grid-independent thrust and torque coefficients is proposed.
    Validations carried out for two conventional propellers have shown that quantitative agreement with experiment is achieved at non-cavitating condition. By applying a cavitation model, cavitating flows around a propeller both in uniform and non-uniform flows are also simulated. Comparisons with experiments have shown that the cavity shape and the variation of the cavity volume are qualitatively reproduced. However, it has been also indicated that the present cavitation model is insufficient in accuracy and stability.
  • 人工ピット材を用いた強度調査
    中井 達郎, 松下 久雄, 山本 規雄, 荒井 宏範
    2004 年 2004 巻 195 号 p. 221-231
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    The first report dealt with the investigation of pitting corrosion observed on hold frames of a 14 year old bulk carrier. Tensile strength and buckling strength of actual members taken from the bulk carrier were also investigated.
    In the present study, a series of tensile tests and compression (buckling) tests has been conducted using test specimens with artificial pitting under a wide variety of testing conditions to investigate the effect of pitting corrosion on the strength in more details. The following results have been obtained;
    - Tensile strength decreases gradually and total elongation decreases drastically with the increase of thickness loss. The reduction of tensile strength and total elongation is large when the original thickness is small.
    - In general, ultimate strength of pitted members under compressive loading is smaller than that of uniformly corroded members in terms of average thickness loss.
    Following the experiment, an elasto-plastic analysis has been carried out to simulate the buckling behavior observed in the compression test in order to verify the method of modeling members with pitting corrosion.
  • 模擬腐食ピットを有する構造モデルを用いた4点曲げ試験
    中井 達郎, 松下 久雄, 山本 規雄
    2004 年 2004 巻 195 号 p. 233-242
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    The purpose of this study is to investigate the effect of pitting corrosion on local strength of hold frames of bulk carriers. A series of 4-point bend tests with structural models which consist of web, shell and face plates has been conducted. Artificial pitting was made on the web plate and bending moment has been applied so that tensile load would act on the face plate. In the case of the long-span model, when pitting concentrated on the web plate near the face plate, cracks were initiated at the bottom of the pits. In the case of the short-span model, local buckling of the web plate occurred near the shell plate and the deformation behavior was strongly affected by the existence of pitting.
    Following the experiment, an elasto-plastic analysis has been carried out to simulate the deformation behavior and buckling behavior observed in the experiment in order to verify the method of modeling members with pitting corrosion.
  • 平松 秀基, 道場 康二, 木村 剛, 豊田 政男
    2004 年 2004 巻 195 号 p. 243-251
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    It is significant to predict ductile fracture initiation in plastic forming of metal materials. Tube hidroforming (THF) is attracting general attention.THFprocess requires the control of internal liquid pressure and axial compression. In this case a ductile fracture may occur under stress triaxiality lower than that for uniaxial tension loading. In this report, combined longitudinal tensile and compression to thickness direction tests using thin plate specimens inA5083-Oaluminum alloy to obtain low stress triaxiality were carried out. On the basis of observations of ductile fracture processes it was founded that ductile fracture was shear type fracture controlled by a nucleation of micro-voids in this test. It is seemed that the local inclusion-matrix interfacial stress was constant independently of any stress ratio of tension and compression. Additionally, THFtests for SPFH590 tubes were performed. It was confirmed that the critical interfacial stress obtained using FE analysis forTHFtest was constant.
  • 大野 好和, 大沢 直樹, 冨田 康光, 橋本 聖史
    2004 年 2004 巻 195 号 p. 253-262
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    In order to establish the calculation method of the fatigue crack opening stress level for the surface cracks in ship structural members, the validity of various crack-node release schemes and opening / closure stress definitions are investigated by 2- and 3-dimensional F.E. analysis of the crack closure behavior of a thickness-through crack. As results, followings are found;
    1) The measured and calculated opening stresses defined by the compliance method agree well when the crack tip node is released at the maximum load and the element edge length at the crack tip is chosen so that it is about 1/10 the size of the plastic zone.
    2) The variation of the crack propagation rate with the depth which gives a good account of the changing nature of the crack edge shape of a real thickness-through crack can be derived when the opening stress is defined as the remote stress at the time the compressive local stress at the crack tip node changes to a tensile stress.
    3) It is advisable to define the opening stress by the sign change of the local stress at the crack tip whenKopis evaluated locally by 3-dimensional F.E. analysis.
  • 榎並 啓太郎, 萩原 行人, 三村 宏
    2004 年 2004 巻 195 号 p. 263-270
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    In this paper, ductile and quasi-cleavage fracture behaviour of a 1300MPa class bolt steel was mainly investigated. Ductile crack initiation behaviour was estimated by the relationship between stress triaxiality and the equivalent plastic strain, which we call ductile crack initiation curve. Quasi-cleavage fracture initiation behaviour was estimated by the Weibull stress approach. Round notched bar tension tests and the corresponding FEM analyses were executed for estimation of the ductile crack initiation curve and the Weibull stress. It was found that the ductile and quasi-cleavage fracture initiation behaviour can be estimated quantitatively by the ductile crack initiation curve and the Weibull stress criterion.
  • 渡辺 喜保, 安藤 裕友, 鈴木 英之, 稲崎 洋一
    2004 年 2004 巻 195 号 p. 271-281
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    A deep-sea riser drilling vessel is now under construction in Japan for the purpose of scientific drilling and will be completed in 2005. The target water depth of the vessel is 2, 500m for the time being and will be extended to 4, 000m in future. In the field of offshore oil drilling, it is confirmed that the target water depth of 3, 000m with using steel riser pipe will be possible. However, the drilling up to the water depth of 4, 000m has not been experienced at all and will have a lot of technical issues. One of the most important issues is to make the weight of the riser pipe lighter and its axial rigidity higher.
    The purpose of this research is to make clear the design concept of the mechanical joint between the CFRP pipe and the steel connector and develop a CFRP riser pipe capable of drilling in 4, 000m water depth. Here, a prototype of CFRP riser pipe is designed and five experimental models are fabricated and tested. The experimental results are compared with those of FEM analysis and the findings are reported in this paper.
  • 後藤 浩二, 小沼 恵太郎, 豊貞 雅宏
    2004 年 2004 巻 195 号 p. 283-289
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Many fatigue damages in large welded built-up structures are found near a boxing fillet weld toe. These fatigue cracks usually initiate from the toe and propagate in the cross-section of wall thickness as surface cracks.
    Many attempts based on fracture mechanics for the improvement of fatigue life estimation are proposed, because current practical methods based on the S-N curves and the cumulative damage rules cannot estimate the accurate fatigue life under in-service structures. Whereas stress distributions along the fatigue crack path must be given in order to apply fracture mechanics methods for the precise fatigue life estimation, no stress distribuiton along the path is calculated because the shell type elements are used in finite element analyses in practical structural design stages.
    A simple estimation method of the stress distribution over the cross-section of a plate at weld toe, which corresponds to the supposed fatigue crack path in the case mentioned above, is proposed in this paper. The validity of this method is confirmed by comparing estimation results with ones by finite element analyses in which solid type elements are used.
  • 松下 久雄, 中井 達郎, 山本 規雄
    2004 年 2004 巻 195 号 p. 291-297
    発行日: 2004年
    公開日: 2007/05/30
    ジャーナル フリー
    Corrosion of structural members of ships is one of the main problems for ship safety. In this report static strength of corroded fillet welded joints for ship structure is investigated with experimental result using actual materials taken from old ships and corrosion-simulated specimens. Tensile strength, bending strength, parallel shear strength and normal shear strength of corroded fillet welded joints are obtained. Size-ratio of web-thickness to throat-thickness of weld-bead is an important factor for fracture mode, that is, web fracture and weld-bead fracture, of corroded fillet welded joints. And also failures of hold frames in bulk carriers are discussed with result of this study.
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