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Nuclear power generation has been spotlighted as a substitute for petroleum. Efforts are being exerted for the development of more reliable nuclear power plants. This paper describes the present status of such development activities in Japan, especially to enhance reliability of non-destructive flaw detection and to improve component integrity through the cooperative efforts of experts in materials, structural design, fracture mechanics, fabrication and non-destructive examination.

Slow notch bend tests with semi-killed, killed and HT 52 high tensile steels were performed. Fracture appearance transition temperatures Tii and energy transition temperatures are nearly the same, and transition temperatures in ductility criterion Ti, those in low energy level TrLE (10 kg-m/cm2) and those in reduction in thickness Trφ (4 %) and also nearly the same for three kinds of steels.Results of slow bend tests are compared with the results of Charpy and Tipper tests in same steels. As to fracture appearance transition temperature, slow bend test is most sensitive and Tipper test is the next.

As a recently results of the irradiation test, it has been found that the brittleductile transition temperature shifts to higher temperature for the structural steels when these are irradiated. Therefore, the problem of the brittle fracture of the reactor pressure vessel is now emphasized from the standpoint of the safety of reactor operation.This paper describes the theoretical and experimental studies on the neutron irradiation brittleness both in Japan and other countries. The paper also points out the some problems encountered in the irradiation tests.

This paper deals with the results of the low cycle fatigue tests on hour-glass type and round notched specimens of SM 41 A. Strain-controlled and load-controlled low cycle fatigue tests at ambient temperature were carried out to investigate the notch effect on the fatigue strength reduction factor.The following conclusions were obtained :1) A visible crack of 0.2 to 0. 5 mm in length will be initiated on the notch root of a notched specimen with any shape factor at an approximately same number of cycles, if the same equivalent strain at the root of a notch is used as the measure of evaluating strain amplitude.2) A concept was proposed on low cycle fatigue strength reduction factor. The fatigue strength reduction factor Kf, _??_ which is calculated from the results of strain-controlled low cycle fatigue tests on smooth and notched specimens, would be equal to the dynamic strain concentration factor. In case that no low cycle fatigue tests would be carried out, the fatigue strength reduction factor may be obtained from the result of dynamic strain analysis.3) “A” factor for a carbon steel, which is given in the Fig. D-201 in the Nuclear Piping Code (USAS B 31. 7 1969), is found to give lower and higher value than the Kf, _??_ value depending on an applied stress amplitude. It is also revealed that “A” factor in the Nuclear Power Piping Code is much lower than that obtained by the Method proposed by S. W. Tagart for the material used in the present test.

The stress concentration problem of thin elastic plates is one of the classical problems in the theory of elasticity, and since E. Goursat's work on the complex variable representation of stress functions in plane elasticity problems, much work has been done all over the world, and Muskhelishvili and others have established the unified theory on the two-dimensional elasticity problems. Unfortunately, however, the existing theoretical solutions obtained along this line are quite limited for the practical purpose and the development of a more practical method of analysis is definitely required. It seems that the energy methods will provide the alternative procedure powerful enough to treat the more practical problems although actually not attempt along this line has been made. In this paper, a first effort is made in the application of energy methods to the stress analysis of a perforated rectangular plate, the result of which is found consistent with the famous Howland's solution on the perforated plate strip problem and some test results.

The first nuclear power station in Japan (Advanced Calder Hall type, 166 MW electric) is now under construction at Tokaimura.Construction of several new nuclear power stations will begin within a few years and also building project of the first nuclear powered ship (6500 G.T.) has been started in 1963.Al-killed steel plates 8094 mm thick were manually welded for Tokai reactor pressure vessel and its steam raising units were constructed with 5474 mm thick boiler plates using both submerged arc and manual welding. JPDR is a small BWR (12.5 MW electric), and the inner surface of its pressure vessel was stainless steel cladded by submerged arc process.Researches on the welding of the nuclear reactor have been extensively carried out by Japan Welding Engineering Society and also each industrial plant is doing its own researches. The study on the effect of irradiation on the properties of materials has been just started.

A series of slow notch bend tests was performed to investigate the effect of residual welding stress on brittle fracture of steel.Chemical composition and mechanical properties of steel tested are shown in Table 1.Following 9 types of test specimens were prepared. (Fig. 1).(1) parent metal, as rolled, notched.(2) parent metal, prebent at room temperature as shown in Fig. 2a, notch side tension, permanent deflection 2. 5mm.(3) parent metal, prebent as shown in Fig. 2b, notch side compression, permanent deflection 2. 5mm.(4) welded specimen, as welded, notched.(5) welded specimen, similar to (2).(6) welded specimen, similar to (3).(7) welded specimen, pretensioned at elastic nominal stress of 25 kg/mm2, then notched.(8) do. pretensioned up to yield point. (9) do. pretensioned, permanent strain 2. 5% for 100mm gauge length.Fracture test procedure is the same as Van der Veen test.Temperatures were varied from 0° to -70°C. Fracture appearance are shown in Figs. 3-5.Depth of fibre are shown in Figs. 6-8, and fracture appearance transition temperatures Till are listed in Table 3. Among welded specimens, type (4) (as welded) has highest (TII = -18°C) and type (8) (pretensioned up to yield point) has lowest (TII=-38°C) transition temperature.Residual stress measurement was performed by resistance wire strain gauge. From the results of our experiment, we can conclude that residual welding stress has a pretty effect on brittle fracture of welded structure.

From the viewpoint of the three-dimensional theory of elasticity, a direct method of solution for the natural vibration of a circular cylindrical shell is formulated based on the principle of virtual work. In the present method of solution, all the assumptions, on which the majority of existing theories are based are abandoned, and the vibration characteristics of a circular cylindrical shell with arbitrary thickness to curvature ratio will be studied in the unified way. In a numerical analysis influences of the length-curvature as well as thickness-curvature ratios are extensively studied for various cases of geometrical boundary conditions.

In this paper a numerical method of elastic stress analysis is proposed which will be applicable to various structures composed of thin plates. Generally speaking, analytical method is not suitable to stress analysis of a finite plate. In the case that interaction of plates composing an actual structure is studied, numerical method which is powerful for analysis of finite plate should be applied, since the analytical solution of an infinite plate is considered to be meaningless. In this case the reaction force which acts to one plate from another plates can be involved in the equilibrium equation of the plate as a term of body force, and for each plate this partial differential equation is solved numerically using iterative method to coincide reaction forces and displacements in each plate on the connecting line of plates.As an example the stress distributions in a stiffened plate with a side notch are investigated. By changing width of stiffener and length of slit notch, this example problem is solved numerically in this way. In several cases of slit notch, the distributions of stresses calculated numerically are compared with the experimental results.

In order to analyze gases included in the porosity of welds of aluminium alloy, we formerly constructed an apparatus of gas analysis and investigated the relation between several welding conditions and results of gas analysis on the welds.In this paper, we report on a comparison of the results of several porosity inspections with the results of gas analysis on the welds. For porosity inspections, we have made codes of micrographic inspection and X-ray inspection. These codes are convenient for comparison of the results of gas analysis.We have obtained experimental results as following :1) In precise inspection, it is necessary to use micrographic inspection together with X-ray inspection.2) Gas contents mainly hydrogen included in welds of aluminium alloy (NP 5/6) are about 1-3ml/100g at 0 percentage void.3) According to the observation of the distribution of pores of each size, microporosities (

The convergence of a mixed finite element scheme for plate bending, previously proposed by the present authors, is discussed on the basis of functional analysis. First, the outline of the formulation is presented with some mathematical preliminaries. Then, several kinds of energy inequalities are established to assure the stability of the approximate solution. Thus, the rate of convergence may be obtained by the evaluation of the degrees of the completeness and consistency of the employed shape functions. Some remarks are also given with respect to the extension of the method to initial value problems.

The cyclic behaviors of strain in mild steel plate specimens with a central notch were investigated in static tensile test and zero-to-tension cyclic loading test. In the cyclic test a cumulative damage law was applied to the crack initiation life by using the strain behavior at the tip of the notch, and satisfactory results were obtained. The strain controlled fatigue test simulating the strain behavior at the tip of notch was carried out by using small bar specimens of the same material, and a good correlation was found between the crack initiation life of the plate specimen and that of the bar specimen. By comparing the fatigue test of a linearly increasing mean strain and that of a constant mean strain, the crack initiation life in the increasing mean strain test was shorter than that in the constant mean strain test.The fatigue crack propagation in the plate specimen was observed under the condition of a constant, stepwise increased or stepwise decreased net section stress range. The crack propagation rate was correlated to the maximum strain at the tip of a crack or the stress intensity factor range. The characteristics of the crack propagation and the strain behavior after the stepwise decrease of net section stress range were very different from the other condition of net section stress range.

In the previous paper, a pulsating tension test was carried out using wide plate specimens of mild steel with a central notch of stress concentration factor Kt to be 5 and 10. By simulating the cyclic behaviors of the strain at the tip of a notch to hour-glass shaped small specimens, the low-cycle fatigue crack initiation life of a plate specimen was compared with that of a small bar specimen. The results showed good correlation between the wide plate and the small bar specimen, but the life of the plate specimen with a notch of 5 in Kt was slightly longer than that of small bar specimen, while that for notch of 10 in Kt was slightly shorter. This fact shows that the crack initiation life depends on not only the cyclic behavior of strain but also the configulation of a notch.In this paper, a same test was carried out using wide plate specimens and small bar specimens of mild steel and 50 kg/mm2 high tensile steel, and the crack initiation life was investigated more precisely based on the present and previous results. It was revealed that dominant factors affecting the crack initiation at the tip of notch in the pulsating tension test are maximum strain at the first loading, strain amplitude, increasing mean strain and restraint of deformation at the tip of a notch. Since the influence of the restraint of deformation at the tip of notch can not be realized in the strain controlled test simulating the cyclic behavior of strain at the tip of a notch, the larger Kt of a notch is, the shorter the crack initiation life of the plate specimen is than that of simulating test on the small bar specimen. By comparing with the results of completely reversed strain-cycling test of small bar specimens, it was found that mean strain and its increase show supper posed effect on the crack initiation life when the life of the plate specimen is shorter than about 700 cycles. As for the effect of the increasing mean strain, an effect of the increasing mean strain was found to be appeared only when the increasing rate of mean strain is larger than about 0.1%/cycle, from the results of comparing test of linearly increasing mean strain with that of constant mean strain.In this paper, two cumulative damage rules in low-cycle fatigue are proposed taking into consideration of four factors affecting the crack initiation. One is based on the cyclic behavior of strain, and the other on the cyclic behavior of notch opening displacement. These two rules are able to estimate the fatigue life of the plate specimen within a small extent of deviation.

This paper presents a finite element method for large deflection elastic-plastic analysis of shells of revolution. The piecewise linear procedure is employed and nonlinearity can be dealt with as the accumulation of linear analyses of numerous loading steps. As for the incremental stress-strain relation in the plastic range, Reuss' equation is used. Especially, a trial of method of treating snap-through buckling is proposed. Some numerical examples are given in order to demonstrate the validity of the present method, and the results are generally satisfactory.

The determination of the elastic-plastic stresses and strains ahead a sharp notch should be required in the study of the criteria on the initiation and propagation of fracture. Some kinds of modifications of elastic solutions on stress distribution around a notch have been used in the field of fracture mechanics to assess the behaviour of brittle and fatigue failures because of the difficulty of elastic-plastic analysis.Elastic-plastic analysis of stresses and strains ahead a notch is usually investigated with using deformation theory of plasticity, which could not be considered as the exact representation of the physical phenomena. Recent development of high speed digital computer, however, has made it possible to solve numerically elastic-plastic problems with the flow theory of plasticity.In the present paper non-linear system of equations is derived based on flow theory for linearly strain hardening square thin plates with side notches, which are slit shaped and 90°-V shaped notches. The load was increased in increments, and for each increment of load non-linear partial differential equations were solved numerically by using finite difference and iterative methods. The distributions of stresses and strains all over the plates and their changes were studied in this way.The distributions of strains calculated numerically were compared with the values of strain in experiment, and as the result it is concluded that the solution of numerical analysis approximates closely the stresses and strains in the finite plate with sharp side notches.

The First International Conference on Structural Mechanics in Reactor Technology was held in Berlin, Germany, 20-24 September 1971. The purpose of the Conference was to bring together engineers and scientists actively engaged in structural mechanics problems in the field of reactor technology to meet with fundamentalists in the general field of engieering mechanics and to present and discuss applied and fundamental papers on structural mechanics problems in reactor technalogy.The Conference was organized by the Bundesanstalt fOr MaterialprOfung (BAM), Berlin and Commission of the European Communities, Brussel, in collaboration with cooperating establishments and sponsoring societies. About 800 participants attended and some 340 papers were presented. These were classified into twelve divisions.A: Opening Session, B: Power Reactor Development and Structural Mechanics, C: Fuel and Cladding, D: Fuel Elements, E: Shock and Vibration Analysis of Reactor Components, F: Structural Analysis of Core Support and Coolant Circuit Structures, G: Steel Pressure Vessels, H: Prestressed Concrete Pressure Vessels, J: Analysis of Shell Structures, Containment, K: Seismic Response Analysis of Nuclear Power Plant Systems, L: Thermal and Mechanical Analysis, M: Design, Reliability Methods.

Based on Hellinger-Reissner's variational principle, a rectangular finite element for plate bending is derived with bilinearly varying deflection and incompletely linear moments. This method is an example of the mixed method first proposed by Herrmann, where both displacement and stress are adopted simultaneously as fundamental variables. Because continuity conditions required on the fundamental variables are much relaxed compared with compatible models, suitable shape functions can be easily derived and calculation of the element matrix can be performed by hand. The explicit expression of the element matrix for general orthotropic plates is presented in this paper. A few simple test problems are computed in order to demonstrate the accuracy of the present model, and it is shown that it gives improved results compared with Herrmann's triangular element. Convergence is also assured when suitably small mesh sizes are adopted, and this element can be utilized in general practical problems.

The formulation of the simplified hybrid displacement method for plate bending is given systematically with some extension made to allow for the discontinuity of deflection field. Eight types of finite elements are developed utilizing this principle. They are tested numerically with static, vibration and stability problems of thin elastic plates. The results obtained are in general satisfactory, thus ensuring the feasibility of the method.

Dealing with the strength of ships in bad weather, we must know the external forces acting to ships. Especially the problem of pounding is very important. As the premise of the problem, we had carried out the following experiment.Fine test pieces made of hard alminium alloy 56 S (2mm thick, 11.3-22. 6cm diameter) were strengthened their rigidity with wood plates (about 2cm thick). They were fixed on the falling part of the testing machine (newly designed), and were fallen upon the water surface from 2.5-20cm height. We had measured the impulsive force using piezo-electromagnetic-oscillograph.Consequently we had the empirical formula based on the following assumption : The maximum impulsive force of falling flat plate consists of two parts, one which is proportional to√H has the elastic character, and the other which is proportional to H had the hydrodynamical character. That isPmax=α√2kgMm/M+m√H+βρ gFHwhere Pmax : The maximum impulsive forceα : Empirical constant 0.7 (non-dimension)k : Spring constant of falling bodym : Virtual mass of fluidM : Mass of falling bodyg : Acceleration due to gravityH : Falling heightβ : Empirical constant 18 (non-dimension) ρ : Density of fluidF : Area of flat bottom

Stress concentration problems of thin elastic plates are one of the classical problems in the theory of elasticity, and since E. Goursat's work on the complex variable representation of stress functions in plane elasticity problems, much work has been done all over the world, and Muskhelishvilii and others have established the unified theory on the two dimensional elasticity problems.Unfortunately, however, the exisiting theoretical solutions obtained along this line are quite limited for the practical purpose and the development of the more practical method of analysis is definitely anticipated. One of the authors believes that the energy methods will provide the alternative procedure powerful enough to treat the more practical problems although actually no attempt along this line has been made.In this paper, the first effort is made on the stress analysis of a perforated rectangular plate, the result of which is found consistent with the famous Howland's solution on the perforated plate strip problem and some test results.

During construction of a reactor steel pressure sessel, the material may be subjected to thermal treatments which have serious effects on the quality of the material. This paper describes the results of studies carried out to investigate the effect of various fabrication thermal histories on brittle, ductile and fatigue fracture properties of A302B steel and its welds. Generally speaking, through a proper thermal history consisting of treatment for hot forming, quench and tempering, stress relief annealing at 625°C, deterioration of materials in the final state of thermal treatment can be practically prevented.

The finite element method is applied to the axisymmetric buckling of shallow spherical shells under uniform external pressure. In order to analyze the nonlinear behavior of shells with sufficient accuracy and efficiency, the simple load incremental method is modified by introducing the mid-increment stiffness matrix and residual load correction. The analysis is performed on a fairly wide range of the geometric parameter α to obtain pressure-deflection curves in both pre-and post-buckling states. The results appear generally satisfactory, at least up to the early stage of post-buckling. In particular, the upper and lower buckling pressures are obtained in excellent agreement with known analytical solutions.

We built a boat with out-board engine for trial from light alloy 56S. The following data is ofintersest: L. O. A. 5.000m; beam 1.486m; depth 0.678m; weight of hull only, 100kg. This weightis about a half compared with the same type wooden one.In future sails will be fitted. The form of the boat is suitable for motor boat trimming by the stern and is suitable for yacht when the boat is even keel except engine.The maximum speed was 27 knots with 22 HP out-board engine.This boat has been and will be used to study work, strength, vibration, corrosion etc.

The first nuclear power station in Japan is being constructed at Tokai-mura in Ibaraki Prefecture. The station is an advanced Calder Hall type. The electrical output is 166 MW. The pressure vessel was fabricated using 80 mm ( 3 5 32 in. ) and 92 mm ( 3 5 8 in. ) thick aluminium killed steel made in Japan. Each part of pressure vessel, bottom cap, belt 1, 2, 3, 4 and top cap were prefabricated, then lifted into the reactor building and assembled. Welding of pressure vessel was carried out by 75 skilled welders of Fuji Electric Co., Ltd. Single sided welding of skirt to skirt forging, C/D nozzle to shell welding and C/D standpipe to nozzle welding were very difficult, particularly to get good penetration and to keep accurate positioning and verticality. As a result of good technical control, hard training of welders, sufficient preparations and preliminary experiments, this difficult work was completed successfully and smoothly to programme.

This paper describes the main results of the examination carried out by the Advisory Committee on Reactor Safeguards (ACRS) to evaluate the safety of the First Nuclear Ship in Japan. After analyzing the hazards in various cases of ship and reactor accidents, the ACRS agreed that the safety of the ship could be secured. The results of a safety analysis on NS Savannah analyzed in accordance with the guide of Japan AEC is also presented.

Through the macroscopic measurement of crack growth under the elevated temperature, the crack propagation rate has been found to be in better correlation with the J contour integral value than with other candidate parameters e.g. elastic stress intensity factor, net section stress. In order that this J value may be defined under the stationary creep condition, we must be aware of a certain singular strain field around the crack tip, which has been theoretically analyzed but the existence of which is not recognized experimentally. Using the Moire topographical method and digital processing of raw Moire grids and fringe patterns, the interesting informations have been obtained regarding the strain concentration at the crack tip.

During the early 1960s, a plentiful, inexpensive supply of petroleum enabled Japanese industry to progress rapidly; however, almost all of this petroleum was imported. Even after the first oil crisis of 1973, the recent annual energy consumption of Japan is calculated to be about 360 million tons in terms of petroleum, and actual petroleum forms 73% of total energy. It is necessary for Japan to reduce reliance on petroleum and to diversify energy resources. The use of other fossil fuels, such as coal, LNG and LPG, and hydraulic energy, is considered as an established alternative.

We now have come to the last part of the symposium. The topic of the panel discussion is education and research in nuclear engineering in the universities and the role they can play in energy futures.