This paper describes summarized results of the appraisal on measured corrosion data of hull structure which are obtained through periodical surveys, the corrosion test of specimens of various weld joint, the fatigue test and the stress analysis of corroded specimens. To grasp the conditions of corrosion and the strength is indispensable for the integrity of hull structure through ship's life.
Statistical analysis of pitting corrosion on bottom plate of oil tankers is carried out with good results. It is also found that tank cleaning has considerable effect on the progress of pitting corrosion. Data of plate thickness on lower part of side frames of bulk carriers is appraised by two parameters namely initiation life and progress rate of corrosion wastage. The results show that the progress rate of corrosion wastage is larger than conventional numerals.
Corrosion test of weld joint specimens is carried out under the cycles of sea water and the air. Grooving corrosion has initiated at weld toe of butt joints as a result of the test. The cause of grooving corrosion is presumed due to difference of corrosion potential between HAZ and base metal/weld metal of the specimen. Tensile fatigue test and stress analysis of corroded specimens are carried out. The results are examined as to the relation of fatigue strength and stress concentration factor. It is confirmed that in the case of butt joint stress concentration factor has increased by corrosion and then fatigue strength is reduced. On the other hand, in the case of cruciform joint the factor has nearly unchanged and then the fatigue strength is almost not reduced.

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Many fracture toughness tests under quasi-static condition suggest that fracture toughness is the function of yield stress at fracture initiation point. Since yield stress is the function of strain ratetemperature parameter (R) at arbitrary strain rate and temperature, we assumed that fracture toughness is the function of R value at fracture initiation point.
In the previous paper, we reported that R value keeps some constant value in fracture process zone which is named Intensely Deformed Nonlinear Zone (IDNZ). (The following R_r, notes some constant R value in IDNZ.) Then we reported fracture toughness is the function of R_r, at fracture initiation. On the basis of this result, we enabled to estimate fracture toughness at arbitrary loading rate by fracture toughness test under quasi-static condition and thermal elastic-plastic FEM which is developed by us. But it is a lot of time and labor to estimate R_r value by using thermal elastic-plastic FEM.
In this paper, the simple method to calculate strain rate and temperature rise due to plastic work on loading process is studied for the purpose of obtaining R_r value which is the function of strain rate and temperature in IDNZ. HRR singularity solution of stress and strain distribution in the vicinity of crack tip is adopted to calculate strain rate and temperature rise in this simple method.
Then we investigate the validity of R_r value calculated by this simple method. As a result, we show the validity of this simple method to calculate R_r value.

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It is generally known that stress and strain relation is affected by strain rate and temperature. Constitutive relation between stress, strain, strain rate and temperature is very important to make clear the problem acting on dynamic load. Then many constitutive equations have been proposed by many researchers.
In the previous paper, we suggested the constitutive equation for mild steel can be presented as a function of strain rate-temperature parameter (R). It is in good agreement with experimental data. But we need to carry out many round bar tension tests if we want to estimate constitutive equations for other structural steels.
In this paper, we investigate the simple method to decide on the material constants for estimating constitutive equation by using our suggested method. In this method, we can easily decide on the material constants if only the yield stress under quasi-static condition at room temperature (20°C) is given.
Then we try to estimate constitutive equations for cases of mild steel and HT-80 steel at various strain rates and temperatures. As a result, it becomes clear that we can get easily constitutive equations for arbitrary structural steels if only the yield stress under quasi-static condition at room temperature (20°C) is given.

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Japan Welding Engineering Society (WES) standard WES 2805 gives procedures for safety evaluation of defects at elastic-plastic condition in welded structures on the basis of the CTOD concept. The essential point of fracture strength assessment in WES 2805 is a relationship between CTOD value and local applied strain, so called “CTOD design curve”. It is important to confirm the applicability of local strain based CTOD design curve to the case of the structural stress concentration, because most of brittle fractures in real structures occur from the defects at the structural stress and strain concentrated region.
In this series of studies on fracture strength assessment, an investigation on fracture test results for some kind of structure models with strain concentration was carried out, and modified WES CTOD design curve was proposed. Furthermore, wide plate tests with cracks emanating from a hole and stiffener model tests with a crack in the strain concentrated region were carried out, and applicability of the proposed CTOD design curve was investigated.
In this study, wide plate tests with stress concentration using 2-dimensional finite element analysis were carried out, and it was shown that the relationship between CTOD and local strain was varied with the relative size of the plastically deformed region as compared with defect size. It the plastically deformed region size was lagerer than 4 times of crack length, modified WES CTOD design curve under-estimates CTOD value. It has been revealed that the proposed modified WES CTOD design curve is valid for fracture strength assessment of cracks in the stress concentrated region except above mentioned case.

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In the previous papers, the authors proposed methods for analyzing and evaluating the psychological effects on motion-sickness, using the fuzzy theories.
Another important factor for analyzing and evaluating the motion-sickness incidence is the physiological phenomena arose in the human bodies on board ships and other vehicles. It has been considered difficult, however, to measure and analyze the physiological phenomena such as electroencephalogram (EEG) and electrocardiogram (ECG) under whole-body exposure to low-frequency oscillations, from the viewpoints of medical science.
The authors carried out the measurements of EEG and ECG of subjects exposed very low-frequency oscillation using a ship-motion simulator. They also tried to analyze the measured EEG and ECG by means of spectral analysis, wavelet analysis and other techniques. In the present paper, they show the method for measuring physiological phenomena arose in the subjects brain and heart and also show the method of analyses using spectral analysis and wavelet analysis techniques. Some results which clearly explain the motion-sickness incidence physiologically are shown.

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Measure should be taken for protection of workers against wind and splash of sea water in working environment at sea. Rainwear has been used widely as working suit in marine environment irrespective of the weather conditions such as rain falls and atomospheric temperature. The rainwears gives protection against wind, cold temperature and dirt to marine workers. In this study, firstly, fact-finding on working suit for fishermen in marine environment has been taken, and effectiveness on heat keeping of rainwear which is the most popular working suit for fishermen has been pointed out by some experiments. Secondary, in order to make thermal index of working suit which is applicable to marine environment, co-relation between critical temperature of working environment and wind velocity is considered on each thermal resistance of working suit using thermal equilibrium equation of human body. And also, effectiveness of wind deflector is studied in term of critical temperature of working environment.

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The database of the ship constructed in the past has already been generated in the particular shipyard. However, the application of the database to the design of the new ship is still very difficult since the methodology to extract and to use the knowledge from the database has not been concluded.
This paper proposes the methodology to use the database for the design of the new ship based on the multivariate analysis. The database containing more than three hundred ships were established in this paper. First, the category and its related parameters were defined by the user. For example, the category “Hull Form” was treated using the parameters Cb, L/B, L/d, B/D, D/d and so forth. The whole database was partitioned into clusters and relationship between parameters were established in each cluster. Parameters were determined by the formula obtained here. As some parameters were fixed previously, one must make sure that the set of parameters was in the same cluster. If the ship was assured in the same cluster, one can go into the next category such as “Principal Particulars” and so forth. The process was applied repeatedly to give the final set of design parameters.
The prototype system was built on the Macintosh Quadra 700 computer. Designs of a high speed liner and a car ferry by this system showed good accordance with existing ships.

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In order to define parts in shipbuilding, we need a lot of information which are plate thickness, shapes of grooves, shapes of slots and so on. It is needless to say that ship structure consists from so many parts that the work to generate information of parts is one of the most hard works in shipbuilding industry.
In order to support the work to define parts, the authors have developed system for parts design, by using our previous system which is the prototype system of CIM for shipbuilding, we call it SODAS (System Of Design and Assembling for Shipbuilding).
In this paper, we have proposed a new concept. It is “Superiority and Inferiority of parts” for description of a relation between two parts. The information is inputted into parts as attribute data. Because of recognition of relation between parts by this information at design stage, we can design a detail shape of parts.

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It is needless to say that a lot of information on process planning and scheduling are very important for production activities. Therefore a lot of efforts have been conducted to develop systems for production planning and scheduling in Japanese shipyards with the advancement of computer technology.
In order to develop CIM for shipbuilding, the author implement a product definition system. This system is called SODAS (System Of Design and Assembling for Shipbuilding). In previous papers, systems for process planning and scheduling are discussed. However they are not fully integrated.
In this paper a few concepts are introduced, in order to develop production planning for shipbuilding. These are ‘Process Operation’, ‘Task’ and ‘Factory Model’. ‘Process Operation’ and ‘Task’ are models which operate in shipyard operation. ‘Factory Model’ is a model of shipyard. By using a relation between Product Model and ‘Factory Model’, information of ‘Process Operation’ and ‘Task’ are acquired. Information on process planning and scheduling may be generated when good considerations are payed.

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Even though large scale of structures are usually carried by dock side crane, few studies have been done on the technology in the erection stage for shipbuilding. The reason is that those technologies have been thus far supported by the highly skilled people. Now situations is radically changing with respect to human resources. We are facing the problem that we will not be relied on the skillful people. In order to overcome this problem, computer aided technolgy is thought as one of the most powerful methods.
In this paper, a computer simulation system for the erection stage is considerd by using SODAS (System Of Design and Assembling for Shipbuilding). Some simulation results are shown in this paper.

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Life of structures which are subject to fatigue failures involves high degree of uncertainty and risk. In order to design such systems it is necessary to take into account several stochastic elements. As the structure ages, the relationship among initial cost, inspections, maintenance and reliability level becomes important, and it has to be studied in order to achieve a good design from the cost-effectiveness point of view. This paper analyses this relationship and proposes a method to take the best decision among a set of alternatives regarding structural dimensions using a new class of Bayesian loss functions that are based on the concepts of under and over design.

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The results of the first inspection contain information which laboratory experiments can hardly furnish, such as crack initiation time parameters. Moreover, it is pure in a sense that it is not infected by noise coming from previous, imperfect, inspections. In other words, it is a rich source of information that can be analyzed by Bayesian methods. The first inspection time also heavily influences the overall structural reliability, and therefore the overall costs as was noticed from previous works. By minimizing a loss function based on mean Shannon information, a suitable criterion for selecting the first inspection time is proposed.

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With the deterioration of the technical ability of crew members of mixed nationalities, the frequency of incidence of marine accidents such as collisions, running agrounds or ship fires; also tends to increase gradually. The development of a methodology for the reliability analysis of the means available for the prevention of marine accidents originating from human errors is becoming highly desirable in recent years.
This paper presents an analytical method for the estimation of the incidence probability of accidents during the functional design applications of marine systems. This process of probability estimation is divided into three stages. Firstly, the qualitative analysis of the reliability of the functional system under design is carried out using the fault tree. Next, the probability of human error and the frequency of device failure in the functional system are decided by using a degree of unsafeness; which is defined as similar to the sense scale based on the experience and ingenuity of engineers. Lastly, the improved choice of items are used in the calculation using the Boolian function to reduce the risk of accident probability in the functional system. The effects of countermeasures adopted are predicted quantitatively in the calculation based on the fault tree analysis and the fuzzy theory. As a practical example, the conditions for reducing the incidence of fire spreads during a ship fire are investigated using the proposed method.

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Subjective information of human are widely utilized in every sphere of engineering. However, subjective data can not be handled in the same way as objective data, if they are not quantified. As the result, subjective data are not introduced in numerical analysis, usually. In this study, fuzzy membership functions are employed in order to quantify subjective classification information. A probabilistic model which can determine the shape of membership function from fuzzy data is proposed. Further, for the utilization of subjective information in reliability engineering, a recursive method to estimate probability density function from subjective classified data is developed. This probability density function can be used in the reliability analysis in the same way as the ordinary probability density function since all the calculation is carried out based on the probabilistic methods.

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