It is well known that at the meso-scale, a fusion cast refractory usually exhibits local heterogeneities. During the fabrication or heating process, these heterogeneities generate stresses that might lead to failure. It is very necessary to investigate these microscopic stresses associated to the local heterogeneities. It is also difficult to analyze the microscopic stress using a traditional procedure such as the finite element method. This is mainly due to the fact that we cannot numerically solve the stress without considering the multi -scale problem, i.e. the coupling of macro- and meso-scale. In this paper we propose the use of the mesh superposition method, which is one of the effective multi-scale numerical methods, to analyze the correlation between the local and global behavior. The advantage of this method resides in the possibility of performing the stress analysis on both of the macro- and the mesostructures simultaneously by superimposing the local mesh that expresses the local heterogeneity, such as an inclusion, onto the global mesh that expresses the homogenous media. The results obtained by our proposed procedure and those obtained by the traditional method using a fine mesh were compared. The comparison revealed that the results of both procedures were very close. This validation proves that our proposed procedure has a good accuracy to justify its use instead of time consuming traditional method with a fine mesh.

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The wear properties of CrN mm has been investigated as a function of arc current which is one of the processing parameter of arc ion plating (AIP) method. CrN films were coated onto high-speed tool steel substrate under four arc currents of 50, 100, 150 and 200 A. CrN films were also examined using X-ray diffraction. The results obtained in the present study were summarized as follows. The dynamic micro hardness was hardly influenced by the arc current. For SEM observation, many droplets existed on the CrN film, which were generated by the dropping out of the macro-particle of non-evaporated Cr. The distribution of droplet depended markedly on the arc current. The wear weight was also dependent on the arc current. CrN film, which was synthesized at low arc current of 50 A markedly improved the wear resistance. For CrN film coated under the high arc current of 200 A, the wear resistance was less than that of film of 50 A. By the successive observation of wear track using optical microscope, the large adhesive matter was observed on the wear track. For opposite ball, the wear weight increased with decreasing the arc current. It was also seen from SEM observation and EDX that for the wear track, the adhesive matter was opposite ball. The area of adhesion of wear track for CrN film was less for 50 A than for 200 A. For 50 A CrN film, the decreases of adhesion contributed to increases in the wear resistance.

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Japanese utilities are increasing their use of gas turbines for generation of electricity. In order to maintain competitive electricity rates, the utilities need to find ways to reduce maintenance costs. There is a need to develop nondestructive evaluation (NDE) methods that can be applied to gas turbine blades in situ during periodic turbine maintenance, and to be able to use the NDE results and operating history to predict future degradation. This paper describes the development of methods for detecting cracks right under MCrAlY overlay coatings, and entimating crack depths from the results of eddy current testing. For these purposes, an eddy-current measurement system has been developed, and Ni-base superalloy specimens with the CoCrAlY coatings have been prepared for the eddy-current measurements. Notches simulating the cracks right under the coatings can be detected, discriminating from surface-breaking notches in the phase angles of their eddy-current responses. The proposed flaw-sizing approach can provide more accurately the estimated depths of the cracks, irrespective of their lengths.

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Notched specimens of two kinds of porous ceramics with porosity 40% whose mean grain sizes were 200 and 500 μm were fractured under four-point bending. A single edge notch with nine depths ranging from 0.1 to 4.8 mm was introduced to the rectangular specimen with a height of 8 mm. Small notches were non-damaging and fracture did not start from the notches. The size of the non-damaging notch was larger for larger grain-sized material. The load versus strain record showed nonlinearity before reaching the maximum load for all specimens fractured from the notch. The critical stress intensity factor for crack initiation from the notch was nearly constant. The resistance curve was constructed by estimating the crack length from the compliance change of the specimen, and was successfully used for determining the maximum load point in bending tests. Fractographic observations showed that fracture occurred at the binder phase or in the particle containing many tiny holes.

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At a tee junction point of piping system, hot water and cold water is mixed with each other in a whirl. The vibrating mixing boundary between the hot and cold water causes a temperature fluctuation on an inside surface of the pipe just after the connection point. The temperature fluctuation yields a cyclic thermal stress near the pipe surface and results in the crack initiation. In this study the thermal fatigue tests using disk specimens in simulated BWR environment were performed and the thermal fatigue crack initiation strength was compared with the mechanical fatigue strength. Furthermore the thermal fatigue crack arrest depth was analyzed using the linear fracture mechanics, and the arrest depth was found to be in proportion to the reciprocal root of the frequency of temperature fluctuation, and the experimental results agreed well with the analytical ones.

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The iterative Domain Decomposition Method (DDM) is one of the most effective parallel algorithm for large scale problems due to its excellent parallelism and variety of researches have already been done. As the iterative DDM satisfies continuity among subdomains through the iterative calculations, it is indispensable to reduce the number of iterations with a preconditioning technique especially for speed-up for computing. Thus, we have chosen the Balancing Domain Decomposition (BDD) proposed by J. Mandel. The BDD is a Neumann-Neumann type preconditioner with a coarse grid correction, and then its convergence estimates are independent of the number of subdomains. In this research, we introduce the BDD algorithm and how to apply it for elastic problems, then we develop a parallel BDD based on the Hierarchical DDM (HDDM) and apply it to some numerical examples on parallel computers.

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The interface fracture between sub-micron films can be classified into two types: opening mode and sliding mode. Corresponding to fracture mode, the interface strength should be evaluated quantitatively, but it is difficult to apply mode-controlled load. In this study, the criteria of crack initiation at the edge of interface between thin films for an LSI are examined under opening mode and sliding mode, respectively. Not only the evaluation method for opening mode but also that for sliding mode is proposed. The Si₃N₄/Cu/TaN films on a Si substrate is tested. The crack initiates at the Si₃N₄ (thickness: 100 nm)/Cu (thickness: 400 nm) interface in both modes. Stress analysis reveals that singularity fields of σ_xy and τ_xy appear near the edge in opening mode and sliding mode, respectively. On the basis of fracture mechanics concept, the interface fracture toughness of both modes are evaluated. The fracture toughness of sliding mode is smaller than that of opening mode and it is a characteristic of the interface strength between thin films.

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The finite element models of the Euler-Bernoulli beam theory and Timoshenko beam theory are now standard. The Timoshenko beam theory includes the effect of transverse shear deformation. This theory is called the first-order shear deformation theory. The first author developed a beam element based on a displacement formulation of Timoshenko beam theory. The objective of this paper is to present a formulation for beam element based on the refined plate theory proposed by Shimpi. The present theory accounts for the cubic variation of the in-plane displacements through the beam thickness. Furthermore, the transverse displacement w is given by w = w_b + w_s, where w_b and w_s are its components due to bending and shear, respectively. The efficacy of the present beam element is demonstrated through the numerical examples of static flexure and free vibration.

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A general solution for a viscoelastic medium with arbitrary-shaped cavity of free or fixed boundary is given for the cases of uniform out-of-plane loads at infinity, and shows as the closed-form solution, the closed-form solution. This analysis is based on the complex variable method using the conformal mapping technique and the correspondence principle between elasticity and linear viscoelasticity. Using the solution, the stresses and displacements around arbitrary-shaped cavity of free or fixed boundary are discussed under time variation. Several numerical examples for out-of-plane problem are shown by graphical representation for various arbitrary-shaped cavities.

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Many investigations have been done on dynamic behavior of solids or hypervelocity behavior of condensed matters. However, general formulas between two collision velocities and material constants et al. before collision and physical quantities of two continuous bodies immediately after collision have not been yet sufficiently established when two continuous bodies collide each other at any collision velocity including two cases above mentioned. In the present paper, it is newly shown that relational formulas among physical quantities produced by plane collision are expressed in terms of two collision velocities, material constants and the slope of the relation between propagation speed of precursor and particle velocity of the compressive stress wave. And, theoretical equations are derived based on the proposed general formulas in a few special cases and considered. Those approximate formulas and applicable conditions are given.

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A general formula in a 1-dimensional plane collision was established in an another report in which any physical quantities in both bodies immediately after collision are expressed in terms of collision velocities, material constants and coefficients before collision when both bodies collide with any collision velocities. In the present paper, the equations in the calculation to obtain any physical quantity are derived from the proposed general formula when two bodies are of the same material and the same cross-sectional area and both bodies collide each other and then shock wave is produced in the target at rest. And calculated values based on the derived theory are compared with experiments of the relation between shock pressure and relative volume. Consequently, both theory and experiment agree precisely, the proposed general formula in a 1-dimensional plane collision is proved to be valid also in the case of hypervelocity collision.

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Bone tissue is a composite material composed of hydroxyapatite (HAp) and collagen. Because HAp in bone tissue makes a crystal structure, an X-ray diffraction method is available to measure the strain of HAp. In the X-ray diffraction method using characteristic X-rays with a unique wavelength, HAp in compact bone has much lower crystallization than metal as steel. The peak position of diffracted intensity is not easy to determine from the gradual intensity-angle profile. This work proposes a method to calculate the lattice strain from the information of a whole diffraction profile without a peak position. In this experiment, strip specimens of 28×8×2 mm in size with their long axis aligned to the bone axial or the circumferential direction were cut from cortical bone in a shaft of bovine femur. To confirm the relationship between applied macroscopic strain and lattice strain in bone tissue, a four-point bending device was developed to apply bending load to the specimen during the X-ray irradiation. Macroscopic strain of the specimen was measured by a strain-gauge bonded to opposite side of the surface irradiated by X-rays. As a result, the accuracy of measurement by this method was better improved.

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