Depth sizing of stress corrosion crack (SCC) by ultrasonic testing has been required in the inservice inspection of primary loop recirculation pipes in boiled water reactor type power stations. Crack tip diffraction techniques are used for the depth sizing, and inspectors are required their experiences and skills to identify weak crack tip diffraction echoes which are critical for accurate depth sizing. Better understanding of complicated wave propagation behavior around a crack may offer an idea to detect the weak crack tip diffraction echo effectively. In this paper, ultrasonic visualization equipment is constructed to observe how ultrasounds travel in solids, and behavior is discussed as longitudinal and shear waves strike slits or SCCs.

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A new crack tip diffraction technique is proposed for accurate depth sizing of flaws on the surface opposite to the examination surface in which a pair of an angle beam and a 0-degree transducers is used as a transmitter and receiver. In this technique, flaw depth is easily calculated from the time difference between two echoes of a tip diffracted longitudinal wave, which arises after the incident wave from the angle beam transducer impinges on the flaw. One echo is related to the wave traveling directly from the tip to the receiver, and the other is a wave which is reflected at the back surface and subsequently travels to the receiver. These two echoes are detected by the 0-degree transducer located right above the flaw. Depth sizing by the proposed technique is much easier than those by standard crack tip diffraction or TOFD techniques. The new technique will be discussed by use of a finite element program to predict the behavior of wave propagation and received wave forms

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This paper deals with a new crack tip diffraction technique named the “short path of diffraction (SPOD)” technique for accurate depth sizing of flaws on the surface opposite to the examination surface in which a pair of an angle beam and a 0-degree transducers is used as a transmitter and a receiver. In SPOD, flaw depth is calculated from a time difference between two echoes of a tip diffracted longitudinal wave, which arises after an incident wave from the angle beam transducer impinges the flaw. One echo is related to a wave traveling directly from the tip to the receiver, and the other is a wave which reflects at the back surface and subsequently travels to the receiver. The two echoes are detected by the 0-degree transducer located right above the flaw. The new technique will be demonstrated by applying to depth sizing of slits and fatigue cracks in austenitic stainless steel blocks, and slits and stress corrosion cracks in welded austenitic stainless steel specimens.

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In this paper, stress intensity factors for a three dimensional rectangular interfacial crack are considered on the idea of the body force method. In the numerical calculations, unknown body force densities are approximated by the products of the fundamental densities and power series, here the fundamental densities are chosen to express singular stress fields due to an interface crack exactly. The calculation shows that the present method gives rapidly converging numerical solutions and highly satisfied boundary conditions. The stress intensity factors for a rectangular interface crack are indicated accurately with varying the aspect ratio, and biomaterial parameter.

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Rafting of the nickel-base single crystal superalloy CMSX-2 was investigated under the condition of high thermal stress using a newly constructed experimental equipment. The test piece with the diameter of 25 mm was tested at the maximum material temperature of 1 000 degree Celsius for 80 hours. The results showed that the raft structure occurred only under the influence of thermal stress. The raft structure developed parallel to the direction of the compressive thermal stress because of negative lattice misfit. The thickness of gamma phase and gamma prime phase in rafting increase with the increase in the temperature and the thermal stress.

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Phase-field model and computational procedure during static primary recrystallization are developed. The developed procedure consists of following three steps. First, the microstructures of plastically deformed polycrystalline metal are simulated by finite element method based on strain gradient crystal plasticity theory. Second, the results such as the accumulated dislocation density and crystal orientation are mapped onto the regular lattices used in phase-field simulation. The stored energy that act as driving force of the grain boundary migration is calculated from the dislocation density and is smoothed to avoid the computational difficulty. Furthermore, the misorientation required for nucleation criteria is calculated on all lattices. Third, phase-field simulation during static primary recrystallization is performed by using mapped data. By conducting a series of numerical simulations, it has been confirmed that the recrystallization microstructure based on the deformation microstructure can be reproduced.

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Kinetic Monte Carlo (KMC) method realizes the millisecond or second order atomistic thin film growth. Twenty five kinds of events which may occur on Al (111) surface were classified. An attempt frequency and an activation energy of each event were defined using vibration analyses and nudged elastic band (NEB) method by which the minimum energy path (MEP) can be reasonably predicted. Temperature and deposition rate dependences of Al (111) film growth were intensively investigated in the present paper. The higher temperature and the lower rate drive the layer-by-layer film structural change. Two types of islands (fcc and hcp) were seen by modeling without considering the events of diffusion of dimer and trimer, while only fcc islands remain with considering such events. Thus, we find that the primitive events of diffusion of dimer and trimer take important roles in determination of surface morphology.

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In present investigation, a three-dimensional virtual crack closure-integral method (VCCM) to evaluate the energy release rate and the stress intensity factor has been developed. Present VCCM assumes the use of second order tetrahedral finite elements. The use of tetrahedral finite elements have became a sort of standard way in large scale three-dimensional finite element analyses, due to the recent advancement of automatic mesh generation software for tetrahedral elements. In this paper, theory, detailed procedures to evaluate the fracture parameters and the results of numerical analyses for mode I problems, are presented and the accuracy of proposed VCCM is critically reviewed.

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In this paper, the mixed-mode thermoelectromechanical fracture problem for a functionally graded piezoelectric material (FGPM) strip with a penny-shaped crack is considered. It is assumed that the thermoelectroelastic properties of the strip vary continuously along the thickness of the strip, and that the strip is under thermoelectric loadings. The crack faces are supposed to be insulated thermally and electrically. By using the Hankel transform, the thermal and electromechanical problems are reduced to a singular integral equation and a system of singular integral equations, respectively. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the crack size, the crack location and the material nonhomogeneity on the stress and electric displacement intensity factors. It can be found that the normalized intensity factors are under the great influence of the geometric parameters and the effect of the material nonhomogeneity on the intensity factors depends on the geometric parameters.

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FRM improving the shortcomings of FRP is widely used as the structural member under the hard environments. However, a fatigue which occupies much of the fracture accidents of the structures cannot be avoided and the growth mechanism of the fatigue damage is very complicated. Because these two things are the serious problem, the establishment of the technique which evaluates the damage and its mechanism is desired. Our aim is to establish the evaluation method for the damage and the fracture mechanism of the fatigue. In this paper, the method that evaluates the fracture types with the chaos analysis and the mahalanobis distance is presented. As the results, the following things became clear : (1) the feature spaces of the matrix damage by the shear mode crack and the fiber breaking are represented by the correlation dimensions and the largest lyapunov exponents of the AE waveforms; (2) the feature spaces of the matrix damage by the tensile mode crack, the fiber deboniding and the fiber pullout are represented by the correlation dimensions and the largest lyapunov exponents of the time fluctuation waveforms of the wavelet coefficient; (3) it became clear that the recognition of each fracture type is evaluated by the mahalanobis distance for each feature space.

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The stiffness of an engineering structure with joints depends not only on the materials and dimensions of the structure but also on the stiffness of the fasteners that connect its components. To evaluate the mechanical behavior of a complex structure with bolted joints, it is important to develop a simple finite element (FE) modeling technique that accounts for the effect of the joint on stiffness. In this study, we developed a modeling technique that simplifies the bolt-jointed structure by using shell and beam elements. The stiffness of the beam element was related to the stiffness of the jointed plates and bolt. We set the equivalent pressure area on the bearing surface region, and the nodes in the equivalent pressure area were connected to the beam element as rigid region by using constraint equations. We measured the eigenvalues of test pieces and calculated those by FE analysis. The analytical eigenvalues agreed well with the experimental results. By using this modeling method of bolt joint, we can evaluate the supporting force of each bolt in the any structure with a large quantities of bolt joints.

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The stiffness of an engineering structure with joint depends not only on the materials and dimensions of the structure but also on the stiffness of the fasteners that connect its components. To evaluate the mechanical behavior of a complex structure with bolted joints, we first developed a simple finite element (FE) modeling technique that was simplified by using shell and beam elements and accounts for the effect of the stiffness of jointed plates and bolts. In evaluating the mechanical behavior, we also need a method for evaluating the strength of bolt joints from the results of FE analysis. In this study, we have developed a strength evaluation method for the beam forces of FE analysis by considering the mechanics of bolt joints. This method can be used to evaluate static failure and fatigue failure of bolts and slippage on clamped plates and bearing surfaces. We can easily evaluate the strength of bolt joints of industrial products with many bolted joints by using this method.

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The present paper describes a method for evaluating the collapse load from the tension- and bending-displacement charts. The plastic constraint factor, the collapse load and the 0.2% proof strength all exceeded the upper bound solution. The two collapse mechanisms observed are tension and bending collapses. Interaction of tension and bending results in a larger collapse load than that obtained from evaluating photo-plastic fringe, especially under simultaneous tension and bending loadings. The maximum load yielded more easily the test collapse load than the two-elastic-slope method.

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JSME Code on Fitness-for-Service for nuclear power generation facilities provides analytical procedures to determine allowable circumferential flaws for pipes subjected to bending moments in the acceptance criteria. The allowable flaws are obtained from limit load criterion or elastic-plastic fracture mechanics. However, analytical procedures for pipes receiving membrane stresses are not provided. In addition, analytical procedure of current Code is only applicable for a single flaw in a pipe. Authors have introduced evaluation method for failure stress of a pipe receiving membrane stress. Furthermore, analytical procedure for circumferential two flaws in a pipe subjected to bending moment has been proposed for the JSME Code.

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