An affix-type multipoint pressure sensor was developed by using the Fiber Bragg Grating (FBG) technology. The FBG technology is commonly used in optical communications and is being applied to the stress/strain measurement of a large structure recently. In this paper, the developed pressure sensor by use of FBG and the pressure measurement system are described. The FBG pressure sensor can be stuck on the surface of a body on which pressures will be measured, and is capable of the temperature compensation by using an FBG temperature sensor. The material and diameter of the diaphragm of the sensor and the pre-tension of the fiber were determined according to the pressure measurement test under static pressures. Pressure distributions on a circular cylinder in uniform flow were measured in a circular water channel, where pressures were also measured by a conventional strain-gauge type pressure sensor. Comparing the measured pressures, performances of the FBG pressure sensor are discussed.

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An affix-type multipoint pressure sensor was developed by using the Fiber Bragg Grating (FBG) technology. In the 1st report, the measurement system of FBG pressure sensor was described and the performance was confirmed in a pressure measurement test on a circular cylinder in uniform flow. In the 2nd report, the FBG pressure sensors were stuck on the surface of the fore- and aft-body of a model ship and resistance tests were conducted. The FBG pressure sensor enables to measure the multi-point pressures on curved surfaces of a ship with the temperature compensation. The measured pressures were compared with the result of CFD calculations, and the effects on the ship's resistance were investigated. It was found from the experimental results that the FBG pressure sensor is effective to measure multipoint pressure on the surface of the model ship in resistance tests.

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It is known that ocean color depends on contained materials in seawater. It is possible to use it for detecting significant information of sea. Since the reflection and absorbance of light can be expressed by superposing these effects of material and sea conditions, the spectral distribution is in a characteristics matter. In order to separate and extract the information, particularly the material concentration, an appropriate mathematical or physical model can be used for the measurement. As the result of examination on measured data and optical spectrum, it is found that the so-called principal component regression (PCR) method is effective. It gives good result in the case of liner system. The physical model, which is shown by mathematical expression, however, should be need for general case of course.In this paper, the authors have proposed a sophisticate measurement method for materials in seawater, phytoplankton, particle matter (PM) and also chromophoric dissolved organic matter (CDOM), using the PCR method and also the optimization technique of mathematical physics model with quasi-Newton's method. Effectiveness of the present method is shown by several measurements of coastal seawater.

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At stormy weather, dredging and filling operation and so on, the water with high concentrations of solids arises in coastal sea area. Growth of seaweed and algae is obstructed to interrupt sunlight by water with this high turbidity. To make matters worse, sediments has the character to adsorb the nutrient and organic matter on those surfaces. Water involved high concentration of solids with nutrient and organic matter make seawater and seabed polluted. In order to improve them, it is very important to measure the spatial and temporal variability of solids dynamics and to monitor the coastal environment.In this study, the authors proposed a new measurement method of solids depth profiles by using Acoustic Doppler Current Profilers (ADCP). Authors regarded the propagation of ultrasonic waves as inverse problems in underwater and modeled these factors, which influences the propagation of ultrasonic waves. By using ADCP and optical turbidity sensor, the depth profile of the solids concentration can be measured. Since ADCP can be obtained the three-dimensional velocity, the present method is suitable for monitoring in order to understand the solids dynamics in seawater.

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Re- entry operation is requested to make the connection of the riser end with the bottom platform (BOP). In re-entry operation, the relative position between the riser end and the bottom platform should be measured. To facilitate re- entry operation, the paper presents an image analysis approach that is convenient to measure the relative position between the riser end and the bottom platform with a single waving camera installed on a ROV. In the image analysis approach, and the targets of the riser end and the bottom platform are recognized from the obtained image by matching the shape models of targets, and the shape regions of targets are highlighted. In the shape regions, the position of riser end referred to the camera, and the orientation of camera referred to the bottom platform, are calculated from circle marks on the tabs attached on the riser end and the bottom platform. Also the relative position between the riser end and the bottom platform can be got thereby, not influenced by the orientation of the waving camera. To check the accuracy of the image analysis approach, the experiments were carried out, and the results are shown in the paper. To test the applicability of the approach to the riser end survey, the model experiments of re- entry operation in water tank were carried out also, and the successful results are shown in the paper.

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An objective of this research is to evaluate the feasibility of the Gaussian distribution model's application for the vertical Chlorophyll-a (Chl-a) estimation in inner bay by the satellite remote sensing. The in-situ Chl-a (N=15) observed as data for a basic Gaussian model verification in Hiroshima Bay between 2004 and 2005 was used. Consequently, the vertical Chl-a in the bay is to approximate by the Gaussian model using six parameters. However, if the equation for the estimation of Gaussian model parameter is not adjusted every time, the vertical Chl-a estimation only from surface Chl-a data obtained from the satellite data is difficult. The most difficult Gaussian model parameter to estimate from the surface Chl-a was Cmax (Chl-a maximum) and Z_max (the depth of the Chl-a maximum).

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Path planning of an autonomous underwater vehicle is one of the most important problems to reduce energy consumption and to navigate safely.Since there exists more or less sea current in most of underwater environments, a current disturbance becomes resistance and a factor to increase the energy consumption according to a direction of motion of AUV.Thus path planning considering a sea current field make possible an improvement of energy consumption.In this paper, optimal path planning considering energy consumption for AUV is formulated as a shortest path problem in Graph Theory.Solution of the formulated problem is obtained by Dijkstra's Algorithm which is an algorithm to find the shortest paths in a weighted, directed graph.The effectiveness of the proposed method is verified through numerical simulation in several current fields with obstacles.Furthermore, authors propose a triangular panel interpolation method for the purpose of applying this technique to measurement data of sea current fields.The method uses the Delaunay Triangulation to generate triangular panels from data points scattered at random.Then sea current data at an arbitrary point are interpolated using triangular panels generated.

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Tsunami is not only causing the raise of free sea surface but also strong horizontal water movement in a bay. Thus, an appropriate countermeasure is required for a passenger ship because the ship may be forced by tsunami to move unexpectedly. In this case, tsunami acts as a variable to limit evacuation time of passengers from a ship to shelter areas. For instance it is estimated that the time to tsunami arrival at Tempozan Passenger Terminal of Osaka Port, that is available time for passengers to evacuate is around 1 hours and 40 minutes (6000 sec). Passengers evacuation, which is caused by tsunami attacks has different problems since passengers not only have to evacuate from a ship, but also have to run to safe areas where they do not receive the impact of tsunami, such as in high land area. This paper describes the use of Discrete Event Simulation (DES) of passengers evacuation process due to tsunami attack considering several scenarios, such as in the morning, day and night scenario considering MSC.1/Circ.1033; therefore, it will be known that how many people are safe in the case of such incident. The outputs of analysis are prediction of time evacuation; as a result, they can be used as consideration of port safety management and evacuation procedure in case of tsunami disaster.

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During drilling operation various forces are exerted on a drill pipe such as a tension due to the weight of the drill string and vessel heave, as well as a bending stress due to vessel movement and ocean current. There is also a hoop stress due to holding by conventional tools "slips" which translate axial load to transverse load. As drilling depth increases, the hoop stress can become greater and can actually damage or in the extreme case crush the drill pipe, called slip-crushing. So, it is necessary to evaluate maximum stress which is assumed to be obtained by superimposing these stresses corresponding to actual drilling operation. There is also another possible strength problem - fatigue strength. Since drilling operation progresses by rotating the drill strings under the condition that it will be bent due to vessel motion, the bending stress will act as an iteration stress. Especially in deep drilling, since the tension on the top of the drill string acting as an average stress become greater, the fatigue strength will be descended. Therefore, it is necessary to establish the method of strength evaluation of the drill pipe including consideration of the hoop stress and evaluation of fatigue strength which can become critical in deep drilling. This paper describes the method of strength evaluation of drill pipe for deep drilling by means of conducting the strength evaluation using it.

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Though many methods are applied to solve the combinatorial optimization problem, there are many cases in which the solution can not be solved in practical computation time, even if the computer becomes more advanced. Recently "ant colony optimization method (ACO)" has been proposed for it as one of the meta-heuristic method. This research tried the ACO in ship production field. Firstly, ACO was applied and verified for the traveling salesman problem (TSP) to obtain the shortest path in many cities, as a representative combinatorial optimization problem. Next, on the basis of the result, ACO was applied to the problem in search of the optimum pathway of the torch of welding robot for the assembly of ship hull structure, and of NC plasma cutting machine of steel plate. As a result, it was confirmed that ACO is effective to solve the optimum path of the machines.

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Since the hull form of ship gets slim at fore and aft parts, the arrangement of longitudinal stiffeners on curved shell plate at the parts is difficult compared with midship part. The design of longitudinal stiffener arrangement relies on designer's skill, therefore there is a large possibility that better solutions are obtained when optimization technique is introduced and it is studied here.In this optimization, the space between longitudinal stiffeners and the scantling and angle of them are taken as design variables. But, the number of the longitudinal stiffeners should be given by designer before the optimization. Constraints are strength by rule and requirements from construction. The objective function is total cost, which is calculated from steel weight and man-hour used for assembling longitudinal stiffeners.The number of joints between longitudinal stiffeners should be increase for saving the cost of steel, although the number of joints should be a few in view of reduction of man-hour for assembling. In order to solve this problem, a cost parameter for handling the number of joints is added to the objective function. The creation of the joints is decided from if the two consecutive longitudinal stiffeners have the same scantling and angle. The geometrical condition of longitudinal stiffeners is also added for judging the necessity of the joints.A simplified model, in which the unit cost of man-hour for the joint is changed, is solved for showing the validity of the proposed methods. The design candidate where the steel weight is reduced and the number of joints is increased is obtained when the unit cost of man-hour for the joint is set as low. On the other hand, when the unit cost of man-hour for the joint is set as high, steel weight is increased and the number of joints is reduced.The proposed method is applied into the real ship structure. The hull form of fore and aft parts is imported from the 3 dimensional product model and the genetic algorithm is adopted as an optimization method.

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A structure optimization for the initial design of ship is under consideration in this paper. A bulk career is selected for the object of the optimization. Both the shapes and the plate thicknesses of a bottom structure of ship are taken as design variable simultaneously. Totally 66 design variables, 4 for shape and 62 for thickness, are considered here. Individual mesh sub-division technique and multi-point constrain method are introduced for making this optimization possible. In order for reducing computational effort, a sensitivity analysis is used instead of FEM, and the validity of using it is examined. Degree of influence for design variables to stress is introduced for reducing computational efforts. Computational results are compared with a real ship data and a great performance is observed for the optimal design with considering the size and the plate thickness of a ship structure. Multi Island Genetic algorithm is used for this optimization in this study.

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A methodology to identify crucial tasks of ship design process is proposed in the first report. Crucial tasks of ship design process are identified in the standardized manner to support design knowledge transfer. In this paper, the proposed methodology is implemented as a web based questionnaire system to conduct a large questionnaire-based survey in design department of a shipyard. Unstructured interview after a questionnaire-based survey exhibited the essential characteristics of crucial tasks identified by the methodology. The characteristics in this paper are following three items: Trade-off such as amount of steel product and man hour, capability to extract 3D model and communication skills with outside of his/her team. The survey also pointed out some part of crucial tasks are outsourcing in Japanese shipyards. The proposed methodology is verified in this large empirical study.

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It is very important to estimate the propulsive performance in actual seas, when designers select the principal dimensions of hull and main engine with the reasonable sea margin, from the viewpoint of ship economics. The author reported in the previous papers a new method to evaluate the influence of fouling, aging and resistance increase due to waves on ship performance. In the present paper, an approximation formula to estimate resistance increase in short waves is proposed, and several simulations using the present formula and the previous method are carried out. These results showed the influence of principal particulars on the performance in actual seas is different with the judging point of sea trial, voyage in waves and long term voyage after delivery, in addition to the judging item of propulsive performance such as speed decrease or fuel oil consumption.

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At the International Maritime Organization (IMO), guidelines for reference by masters in assessing operational damage stability for safe return to port by own power or tow is to be developed. To contribute to the works at the IMO, a method to assess the capability for safe voyage to port is proposed on the basis of the weather criterion which is used to guarantee the safety of a dead ship in intact condition in beam wind and waves. To apply the criterion to a damaged ship, a simple prediction method for the roll damping created by internal water is deduced on the basis of experimental data. Using the predicted roll damping, a wind speed limitation for safe return to port of a damaged passenger ships can be calculated by the weather criterion. The results demonstrate that threshold in terms of wind speed depends on ship size and water depth on flooded deck as well as damage length.

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This paper consists of two parts. The first part is on the outline of renewd large forced motion machanism to be used in the maneuvering test on submerged body and surface ship model in the large towing tank of Meguro Model Basin, and model test method. The second part is on the construction of empirical estimation method of hydrodynamic derivatives of two-dimensional linearized equation of longitudinal motion of submerged body utilizing the test results of 37 models of various hull forms and their about 250 model configurations. The empirical estimation method is summarized in functional forms. The hydrodynamic derivatives of hull are expressed as function of equivalent length to diameter ratio, and the contribution of control surface and propeller to the hydrodynamic derivatives are expressed by interference coefficients as function of dia meter to span of exposed control surface ratio, and propeller diameter to hull diamater ratio, based on their open water characteristics respectively.

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Tokyo International Airport (Haneda Airport) is used as a center of a domestic airport in Japan by about 60 million people a year, and is requested to correspond to the increase of the demand in the metropolis in the future immediately. This is an extremely important agenda to maintain and to improve not only the user's convenience but also the global competitiveness of our country. Then, a new slide was decided to be installed in the sea in parallel to present "B" slide in December, 2001 since the airport capacity, the noise problem, and environmental problems, etc. were considered. On the other hand, the construction of it is expected to give a big influence to the ship sailing in Tokyo Bay, which plays an important role as the marine transport road where an energy resource, an industrial raw material, and the daily commodity, etc. that support an economic activity and the life of the people. It is necessary to change the position of sea route in Tokyo Bay and there is a possibility that sailing becomes difficult for large ships. So, it aims to execute the numerical simulation for a large container ship to examine the influence on the port function and to give one standard to the sea traffic control with the examination of a new first sea route in Tokyo Bay for the index that evaluates the safety of sailing.

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This paper presents a calculation method for the steady cavitating propeller problem. The method is based on a simplified surface panel method "SQCM" which satisfies the Kutta condition at a time even for the 3-D problem. Hess and Smith type source panels are distributed on the propeller and cavity surface. Discrete vortices are distributed on the camber surface according to Lan's QCM (Quasi-Continuous vortex lattice Method). The boundary conditions to determine these singularities are the constant pressure condition on the cavity surface and the zero normal velocity condition on the propeller and camber surfaces. The cavity shape in each radial section is determined so that the zero normal velocity condition are satisfied. In the present method, a cavity length for each radial section is given first. Then the singularities and the cavity shapes are determined. These steps are repeated until both constant pressure condition and normal velocity condition are satisfied on the cavity surface. Next, the cavity length is corrected in order that the opening at the cavity end will get closer to the target value. By using the corrected cavity length, the calculation is repeated from the beginning. These steps are repeated until the opening at the cavity end agrees with the target value in each section. In this method, constant pressure condition is satisfied including cross flow velocity because its effect is not small near the tip of a propeller blade. Cavity pattern, shapes, pressure distributions and forces acting on propellers are calculated for two kinds of propellers. Good agreements are obtained between the calculated results and the experimental data.

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Simulations of zig-zag maneuver and crash astern in regular waves were carried out. The simulation model used for the stopping maneuver takes only wave drift forces into account to usual maneuvering model in still water. On the other hands, the model for the zig-zag maneuver includes wave-induced motion effects in addition to the wave drift forces. In this paper the validity of the methods are confirmed through comparison with free-running model test results in head and beam waves with various wave lengths for SR108 container ship model. It was found that the simulation methods can roughly predict the zig-zag and stopping maneuvers in regular waves, although there is some room for improvement. It may be needed to make more rational hydrodynamic model or improve the calculation accuracy of wave drift forces.

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This paper, for the first time, describes development and demonstration of a CAD/CFD/optimizer-integrated simulation-based design (SBD) framework by introducing an advanced CAD system direct control approach and a high-fidelity viscous free-surface CFD method. The CAD used in the present study is NAPA, which is one of the most accepted CAD systems in the domestic and foreign shipyards. The CFD method is FLOWPACK version 2006 developed by the present authors, a Reynolds-averaged Navier-Stokes equation solver which is capable for predicting viscous wavemaking effects by using free-surface tracking approach. The adopted nonlinear optimization scheme is based on genetic algorithm; currently, Message Passing Interface based parallel and serial computation architectures are implemented; and in this paper, results from the latter will be presented. The above-described three components are integrated to realize the most advanced-level SBD framework ever reported. An overview of the present method is given, and results are presented and discussed for shape optimization of DTMB Model 5415 and catamaran test cases to show capability of the present SBD framework for single- and multi-objective optimizations, respectively. Finally, prognoses of our future work will be addressed.

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Using two hard chine boat models, a torpedo boat with broad span and a passenger ferry with narrow span, fundamental data related to roll instability is obtained from static and dynamic inclining tests and roll tests in waves. The value of GM is confirmed to decrease when transversely inclined by hydrostatic calculation and inclining experiments in calm water and in steady flow. The broad spanned boat is obtained to be more advantageous at high speed. The wave analysis is conducted to get wave spectrum and wave pattern resistance for inclined hulls. At the same time wave pattern transverse force is calculated by Kotchin's formula. Furthermore wavelet transform is adapted to the wave analysis and the positions at which wave resistance and transverse force act are presumed. Wave test for inclined hull is conducted in order to simulate turning in wave. Roll amplitude increases in proportion to mean inclining angle. The transverse force acting in waves decreases the value of GM. With respect to roll at high speed the broad spanned boat is also more dvantageous.

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An estimation method of the seakeeping of fast ships with transom stern is proposed and validated through the comparison with experimental results. The method is based on the potential theory and the Rankine panel method is employed as a numerical computation method. The transom stern is carefully observed in the experiments and it is confirmed that the transom stern is completely dry even in free motion in waves. A condition corresponding to the observation is derived and imposed as the boundary condition at the free-surface just behind the stern. Numerical results are compared with experiments from the aspects of hydrodynamic forces, ship motions and unsteady waves around the ship. Through the comparisons, the adequacy of the transom stern condition proposed in the present study and also the significant influence of the sinkage and trim in the seakeeping estimations are confirmed.

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When a ship runs in following and quartering seas, she could occasionally face broaching-to, which is a major threat of ship capsizing, or difficulty to keep her desired course due to wave-induce forces. It is noteworthy that usually a PID auto-pilot is used in model experiments and numerical simulations for investigating broaching-to but a PID auto-pilot is not so suitable for identifying operational limits. Thus, in this paper, the optimal control problem for ship maneuvering motion in following and quartering seas was discussed. As a result, while a proportional auto-pilot fails to keep the desired course,optimal control obtained here successfully keeps the desired course as a Bang-Bang control. If wave steepness further increases, even this optimal control may face a difficulty to keep her desired course and then broaching-to could be more rigorously identified.

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Practical ships need to have low total resistance in waves. The present paper proposes a hull optimization method for reducing resistance in still water and added resistance in wave, using the real-coded genetic algorithms. The real-coded genetic algorithm of the optimization method, employs the crossover operator for combining of the methods called the LUNDX-m(UNDX on m Latent Variables) and the EDX(Extrapolation-Directed Crossover), and employs the modified POSS (Pareto Optimal Selection Strategy) as a generation-alternation model. The panel-shift type Rankine source method is used for the calculation of wave-making resistance. The estimate formula based on statistical analysis is used for the form factor. Takahashi's formula and Maruo's formula are used for added resistance in waves. The hull optimization for KRISO 3000TEU container ship is carried out using the program which is based on the present method. In the optimization, many Pareto solutions are obtained. It is confirmed that these hull forms have low total resistance in still water and added resistance in waves comparing with the original form.

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It is well known that the buckling strength of spherical shell and cylindrical shell is reduced by initial shape imperfections and the reduction rate is much influenced by stress conditions. This reduction rate will vary in accordance with the imperfection shape even for the same maximum magnitude. In this study, the geometrical non-linear FE analysis is performed in order to examine what kind of initial imperfection shape will most reduce the buckling strength of cylindrical shell, spherical shell, and ellipsoidal spherical shell under various stress conditions, such as one-directional compression, two-directional compressions, and combined one-directional compression and another directional tension. In the case of both-ends simply-supported cylindrical shells under axial compression, the axi-symmetrical shape imperfection, which is axially of the buckling mode, reduces the buckling strength more than any other imperfection shape with the same maximum magnitude. In contrast to this, cylindrical shells under lateral pressure or under external pressure (combined lateral and axial end pressure) , spherical shell under external pressure and in the partial filling condition that produces the meridian compressive and latitude tensional stress conditions just below the equator, and ellipsoidal spherical shell under the same loading condition as for spherical shell, the imperfection of asymmetrical buckling mode reduces the buckling strength more than any other imperfection shape. The buckling strength of cylindrical shell is much influenced by imperfection mode, while that of spherical and ellipsoidal spherical shells less influenced. In addition, the buckling strength of sandwich (laminated) shell structures with steal skin plate and foam core are examined. The sandwich shell structure is found to have a larger buckling strength and less imperfection sensibility than the homogeneous shell with the same weight.

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Choosing four Panamax-size bulk carriers and four Aframax-size oil tankers designed by different criteria in different times, reliability analysis has been performed to compare their safety levels from the viewpoint of ultimate hull girder strength in longitudinal bending. For evaluation of the ultimate hull girder strength and its sensitivities with respect to design parameters, a series of progressive collapse analysis is performed applying the Smith's Method. On the other hand, applying the nonlinear Strip Method, time-dependent nonlinear ship motion analysis is performed to estimate wave-induced bending moment. On the basis of the obtained time history of wave bending moment, statistic characteristics of the extreme bending moment is estimated. Utilising the calculated results, reliability index and failure probability are calculated applying the First Order Reliability Method (FORM). Investigating into the obtained results, it has been found that in general the safety level becomes higher with the times depending on the design criteria.

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In order to simulate mechanical fatigue phenomena represented by cyclic plasticity such as ratcheting and hysterisis loop, the plastic stretching within a yield surface has to be described, whilst the plastic strain is induced remarkably as the stress approaches the dominant yielding state. The traditional plastic constitutive equation, however, is capable of describing deformation behavior for the stress path only near the monotonic/proportional loading, since the inside of the yield surface is assumed to be an elastic state. In this study, an unconventional plasticity model is proposed for the description of the cyclic loading behavior observed during so-called high cycle fatigue subjected to the cyclic stresses lower than the yield stress. The extended elastoplastic constitutive equation is formulated by introducing both the elastic boundary and the damage concepts. The former is introduced to describe a purely elastic response for the stresses lower than the proportional limit, and the later is to describe the damage effect represented by a progressive degradation of stiffness of materials, which is caused by the accumulation of plastic strain even under the macroscopically elastic condition. The proposed model exhibits a smooth elastic-plastic transition with increase of stress to the dominant yielding state with both plasticity and damage effects. Finally, the extended elasto-plastic model is applied for metals obeying not only isotropic but also kinematic hardening law, and the mechanical responses under cyclic loading condition are examined briefly and compared with the corresponding experimental results for SN490B.

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In the previous paper, influence of applied stress, residual stress and toughness of welded joint on brittle crack propagation was analyzed based on a fracture mechanics model developed by the authors. This model assumes that a crack propagates along the cleavage plane with the highest tensile normal stress among the cleavage planes. Results of numerical simulation were compared with the experimental results which were carried out in the SR 147 research committee of the Shipbuilding Research Association of Japan, and it was shown that the model used could explain the experimental results. In this paper, influence of weld heat input and texture of base metal on brittle crack propagation behavior along welded joint is analyzed using the above mentioned model. Weld heat input involves influence of residual stress (small or large) and toughness of welded joint (welded joint is divided into weld metal, CGHAZ and other HAZ, and toughness of each zone is assumed to be different). Texture of base metal is reflected by normal distribution, and by random for comparison. It is concluded that crack propagation path is dependent very much on weld heat input, but is not dependent on texture of base metal when a crack propagates in welded joint.

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Fatigue cracks may initiate and propagate at welded joints of marine structures due to repeated wave loading. When fatigue cracks are detected in service condition, it is preferable to have an evaluation tool to determine the necessary countermeasure action with minimum intervention to the operation. For this purpose, the authors have been developing a prediction system of fatigue crack propagation, "CP-System". In the present paper, the crack opening and closing simulation is applied to structural components in welding residual stress so that fatigue crack propagation can be reasonably estimated for welded structures under variable amplitude loading. In order to confirm the applicability of the proposed method, fatigue tests using base metal specimen and welded joint specimen are carried out. The predictions were found to be in good agreement with various fatigue test results including variable amplitude tests

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This paper presents a method for predicting the CTOD fracture toughness transition temperature T_i^CTOD for structural steels from Charpy impact toughness T_i^Charpy. T_i^CTOD and T_i^Charpy are defined as the temperature at which brittle fracture coincides with ductile cracking in both Charpy and CTOD testing. This method is proposed based on "local plastic strain criterion" for ductile crack initiation and "Weibull stress criterion" for brittle fracture initiation. The validity of this method is investigated for 490 MPa class strength steel; T_i^CTOD predicted in accordance with proposed method is almost consistent with that measured in experiment. For industrial applications, an engineering formula is established for predicting the transition temperature difference ΔT_i = T_iCharpy - T_i^CTOD from Charpy impact test for structural steels with yield strength from 300 MPa to 900 MPa. In this formula, ΔTi is dependent on the material properties that are the ductility level (&epsirlon;_p ^tip)_i and Charpy impact toughness level T_i^Charpy and flow properties (yield stress σ_Y and 2% Mises stress). The applicability of this formula is verified for 490 MPa, 590 MPa, and 780 MPa strength class structural steels.

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