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Crack analysis is performed for plates characterized by the power hardening material law. A new superposition method of the analytical and the finite element models is proposed with the use of the penalty function, which is frequently adopted to solve the optimization problems. The characteristic distributions of the stress and strain around the crack tip are calculated and compared with the analytical results. Numerical discussion is also made regarding the effects of the crack length to plate width ratio and the power exponent in the hardening law on the nondimensional values of the J-integral, the crack opening displacement, and the residual load point displacement.

Results are presented from an investigation of crack arrest toughness K a , on ASTM A533B Class 1 and A508 Class 3 steels using ASTM-proposed specimens and ESSO specimens. The results show that the values of K a , measured in accordance with the ASTM test method, increased with an increase in test temperature, and that the size requirements in the method were appropriate to obtain valid values of plane-strain crack arrest toughness K I a . It was also found that the ASTM and ESSO tests lead to about the same crack arrest toughness values when applied to large specimens of the same size. The lower bound of K I a data was significantly under that of K I c data on the test materials, though both bounds were well over the American Society of Mechanical Engineers (ASME) K I R curve.

Binaphthosemiquinones are proved to show ambipolar transistor properties. These compounds have characteristic blue colors owing to the small energy gaps, because the quinone part acts as an electron acceptor and the alkoxy group acts as an electron donor. Accordingly, these molecules have an analogous electronic structure to indigo. The crystal structure changes depending on the alkoxy groups, though these compounds generally have stacking structures.

Cracked plates of power hardening material under plane strain and incompressibility conditions are investigated in this work by using a penalty function and superposition method. The present numerical method is found to be quite efficient for the relevant problems if the hardening exponent of material is not so large.

This paper presents an experimental and analytical study on pressure pulse propagation phenomena in a plastically deforming pipe filled with water. The simple and well-defined experiments have been performed in order to provide the fundamental data to verify a two-dimensional fluid-structure interaction code. The experimental facility consists of a test pipe and a pulse gun filled with water at room temperature. The pressure pulse was generated in the pulse gun by low velocity SK explosive, high velocity pentolite or a low energy detonator. Experiments have been performed on 3 m long, 16 cm OD and 0.287 cm thick stainless steel-316 pipe both with and without elbow section. Transient pressure, transient strain and plastic deformation are measured when the pressure pulse propagates along the test pipe which is jointed rigidly to the pulse gun. On entering the test pipe, the pulse attenuates rapidly to the yield pressure of the pipe (14 MPa) in about 40 cm. Large plastic deformation occurs over wider range in low velocity explosive experiments than high velocity explosive experiments. Peak pressure reduces in the elbow section more in the high velocity explosive experiments than the low velocity explosive experiments. The experimental results have been analyzed by using a two-dimensional code. The comparison between experiment and prediction for the pressure pulse propagation behavior shows fairly good results. However, the strains are 30–100% over-estimated by the code. This discrepancy is attributable to the influence of the strain rate on stress and the limitation of the calculational model for simulating the detailed structure of the test facility.

This paper presents a parametric analysis of the creep buckling of a shallow spherical shell subjected to uniform external pressure using the finite-element incremental method. Axisymmetric creep deformation analysis is first performed to obtain pre-buckling behavior by the time incremental method. The buckling modes considered are both bifurcation and axisymmetric snap-through types. Fourier expansion technique is conveniently employed to construct the stiffness matrices corresponding to asymmetric bifurcation as well as axisymmetric snap-through modes of deformation. The critical time for creep buckling is defined by the time at which either stiffness matrices corresponding to the axisymmetric or asymmetric modes lose their positive definiteness. The critical times and the buckling modes are obtained over a fairly wide range of the geometric parameters pertaining to shallow spherical shell subjected to uniform external pressure.

Heavy section steel pressure vessels for light water reactor and aluminum tank for liquefied natural gas carrier are chosen to review the fabrication of pressure vessels. With regard to RPV, materials, effects of fabrication thermal history, fabrication procedure and advanced welding technique are dealt with. For the fabrication of aluminum cryogenic tanks for LNG carrier, a special factory equipped with plasma arc cutting, various automatic gas metal arc welding machines and so on, is advisable.

An urgent problem for nuclear power plants is to assess the structural integrity of the reactor pressure vessel under pressurized thermal shock. In order to estimate crack behavior under combined force of thermal shock and tension simulating pressurized thermal shock, two series of experiments are demonstrated: one to study the effect of material deterioration due to neutron irradiation on the fracture behavior, and the other to study the effect of system compliance on fracture behavior. The test results are discussed with the three-dimensional elastic-plastic fracture parameters, J and Jˆ integrals.

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.

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.

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.

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 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.

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.

A finite element method is presented, which deals with structures subjected to both high temperatures and neutron irradiation. The material effects discussed in this paper include the usual thermo-elastoplastic effects, thermal and irradiation-induced creep and swelling due to the fast neutron fluence. Heat conduction equations and equilibrium equations are derived by assuming a specific form of free energy together with the thermodynamic laws, von Mises yield criteria and the associated flow rule. To demonstrate the effectiveness of the present formulation, the transient creep analysis of a three-dimensional solid subjected to creep effect is presented.

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.

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.