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The J-integral range or the cyclic J-integral, Δ J , is frequently utilized to deal with the fatigue crack growth of ductile materials with large scale yielding. Δ J was originally defined as a line integral similar to the J-integral proposed by Rice. Many researchers correlated fatigue crack growth rate of ductile materials with Δ J defined by J m a x − J m i n . Although it is theoretically shown that the latter definition of Δ J , that is, Δ J = J m a x − J m i n , is not equivalent to the former defined by a line integral, why is the latter definition of Δ J utilized so frequently? This question is main concern of the present paper. To answer this question, we derive the expression of Δ J represented by a line integral for HRR singular fields, which govern the vicinity of a crack tip under large scale yielding, then formulate the difference between the Δ J represented by a line integral and Δ J = J m a x − J m i n . We perform the error estimation for three-point bending specimens to clarify how accurately ( J m a x − J m i n ) predicts the Δ J -value, compared with the Δ J represented by a line integral, which is supposed to provide the exact Δ J -value. As a result, the Δ J -value calculated from ( J m a x − J m i n ) is identical to the Δ J -value calculated from a line integral in the case of the zero-tension cyclic loading conditions, and the deviation between the former and latter values is small under near zero-tension and large cyclic loading amplitude conditions. The use of the Δ J defined by ( J m a x − J m i n ) should be limited to the cases where near zero-tension and large cyclic loading amplitude conditions are satisfied.

The effect of hydrogen on the material strengths of metals is known as the hydrogen embrittlement, which affects the structural integrity of a hydrogen energy system. In the present paper, we developed a computer program for a transient hydrogen diffusion–elastoplastic coupling analysis by combining an in-house finite element program with a general purpose finite element computer program to analyze hydrogen diffusion. In this program, we use a hypothesis that the hydrogen absorbed in the metal affects the yield stress of the metal. In the present paper, we discuss the effects of the cyclic loading on the hydrogen concentration near the crack tip. An important finding we obtained here is the fact that the hydrogen concentration near the crack tip greatly depends on the loading frequency. This result indicates that the fatigue lives of the components in a hydrogen system depend not only on the number of loading cycles but also on the loading frequency.

The finite element method was applied to a generation phase analysis for stable crack growth in inhomogeneous materials. Experimental data on stable crack growth in bimaterial CT specimens, which were made of a weldment of the A533B Class 1 steel and HT80 steel, were numerically simulated using the node-release technique to obtain the variations of the fracture mechanics parameters such as the J-integral, T∗-integral, Ĵ-integral and CTOA with crack extension. New evaluation schemes for the integral fracture mechanics parameters were proposed as being valid for integral paths passing a fusion line of dissimilar materials. It was examined whether the simple formulae of the J-integral for a monolithic CT specimen can be applied to a bimaterial CT specimen or not. The effect of inhomogeneity on the fracture mechanics parameter is discussed in terms of the Q-factor.

In some experiments conducted by other authors, axially compressive cylindrical shells with a large ratio of radius to thickness were observed to buckle with circumferential waves. In this paper, the finite element method is used to study this buckling phenomenon. The bifurcation mode and the axisymmetric mode were considered in the analysis as the mode of creep buckling. The number of circumferential waves obtained from the present analysis agrees well with experimental results. This implies that the circumferential waves observed in the creep buckling experiments are due to bifurcation.

The stress intensity factor analyses of surface cracks in various three-dimensional structures were performed using the finite element computer program EPAS-J1. The results obtained by EPAS-J1 were compared with other finite element solutions or the results obtained by the simplified estimation methods. Among the simplified estimation methods, the equations proposed by Newman and Raju give the distributions of the stress intensity factors along a crack front, which were compared with the results obtained by EPAS-J1. It was confirmed by comparing the results that the finite element program EPAS-J1 gives the reasonable stress intensity factors of surface cracks in three-dimensional structures.

The purpose of pipe rupture studies in JAERI is to perform model tests on pipe whip, restraint behavior, jet impingement and jet thrust force, and to establish a computational method for analyzing these phenomena. This report presents the analytical results of 4-inch pipe whip tests under BWR LOCA conditions. Dynamic response analyses were performed using the general-purpose finite element program ADINA. The test pipe was modelled by straight beam elements and the four restraints were modelled by a single truss element. The analytical results were compared with the experimental results. Impact time and maximum total restraint force showed good agreement with experimental results. On the other hand, pipe strain and pipe deflection could not be predicted so well. The reason for this is that the sliding of the restraint during the pipe whip movement cannot be considered in the analyses.

This paper presents experimental and analytical results of pipe whip tests performed under PWR LOCA conditions using a test pipe of 4-inch diameter and U-shaped restraints. In the tests, the effects of the overhang length on the pipe whip behavior of the pipe-restraints system were studied by measuring the strains and deformations of the test pipe and restraints, and the restraints forces. The equation for predicting the maximum strain at the outer surface of the pipe was derived using a static equilibrium condition. The calculated maximum strains at the outer surface of the pipe agree fairly well with experimental data. The dynamic response analysis of the pipe-restraints system was conducted by the finite element program ADINA. The applicability of the ADINA program to the pipe whip analysis is made clear through this analysis.