Free-edge stress singularity usually appears at the intersection of free surfaces and the interface of bonded dissimilar materials. Not only isotropic material but also anisotropic material is used for making a bonded dissimilar materials. In this study, free-edge stress singularity of bonded dissimilar orthotropic materials were investigated theoretically using the characteristic equation deduced in terms of Airy's stress function. The characteristic equation deduced in this study can be applied for the case when the wedge angles were not right angles. Stress distribution on the interface was calculated numerically by using the boundary element method. The values of the order of stress singularity determined by the boundary element method agreed well with the theoretical ones obtained using the characteristic equation. It was found that free-edge stress singularity disappeared for certain combinations of wedge angles of the pair of materials which had stress singularity when two materials were bonded at right angle to the free surfaces.

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Piezoelectric materials are gradually expected in industrial areas from the excellent characteristics of the mechanical and electrical couplings such as the sensors and actuators. In general, piezoelectric materials possess anisotropic property. And it is important to study mechanical and electro-physical quantity of piezoelectric material by theoretical analysis sense. In this paper, two-dimensional electro elastic analysis is performed for anisotropic piezoelectric materials containing multilayered elliptical inclusions under out-of-plane mechanical and in-plane electrical loads at infinity. General solutions are provided in terms of complex functions. And several numerical examples are shown by graphical representation for mechanical and electrical load.

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This paper is concerned with an application of the homotopy boundary element method originally proposed by Liao and Chwang to analysis of nonlinear transient heat conduction in anisotropic solids. Usually, a domain integral arises in the boundary integral equation of this formulation. Some ideas are needed to keep the boundary-only feature of BEM. In this paper, the resulting domain integral is transformed into a boundary integral by the dual reciprocity method using a new set of radial basis functions. Mathematical formulations of this approach for two-dimensional problems are presented in detail. Two schemes are discussed in this paper : The “isotropic” scheme, in which the state before mapping is considered as steady state heat conduction in isotropic solids, and the “anisotropic” scheme, where the state before mapping as steady state heat conduction in anisotropic solids. The proposed solution procedure is applied to a couple of typical examples, and the accuracy and other numerical properties of the proposed BEM are demonstrated through discussions of the results obtained.

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A general approach is presented for generating compliant mechanisms from a highly connected ground structure. The structure is modeled as a pin-jointed truss, and geometrical nonlinearity is considered. An optimization problem is formulated for minimizing the total structural volume under constraints on the displacement at the specified node, and stiffnesses at initial and final states. The design variables are cross-sectional areas and the nodal coordinates. It is shown in the numerical examples that several mechanisms can be naturally found as a result of optimization starting from randomly selected initial solutions.

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In this paper, the elastoplastic nonlinear behavior of circular tubes subjected to statical axial compression is studied by using finite element method. In order to estimate the performance of compressive energy absorbtion for circular tubes, the effects of material and geometrical properties on first peak compressive stress o are investigated. From this study, it is found that the peak stressσ₁ can be expressed as σ₁/E≅f (t/R, (∂_σ/∂_ε) σ=σ₁/E), regardless of the stress-strain formulations. Here, t is the thickness, R is the radius of a tube, E is Young's modulus and (∂_σ/∂_ε) σ=σ₁ is the stress gradient at σ=σ₁. Based on this fact, one can estimate the stress σ₁ for the power law hardening material from the results of al for the material with the strain-hardening portion of stress-strain curve being a straight line.

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Problems such as casing collapse and so on are apt to occur in a steam injection well for enhanced oil recovery, since the well casing is subjected to compressive axial stress more than the yield stress of the material at the elevated temperature during the steam injection. However, the collapse pressure has not been evaluated under the excessive compressive axial stress. We conducted collapse tests under the axial stress state and derived an empirical collapse pressure formula considering expansion of the outside diameter of the casing and work-hardening of the yield stress due to the excessive axial stress. As estimate by the derived formula can give moderately accurate coincidence with experiment, so estimation of collapse pressure be ready in whole axial stress state including previously proposed formulas under ordinary and excessive tensile axial stress states.

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To investigate the effects of the surface roughness of substrate on fatigue properties of a thermally sprayed specimen, three types of substrates with different surface roughness were prepared. After thermal spraying, two types of post heat treatments (fusing) were performed by an induction heating system and a vacuum furnace. Then rotational bending fatigue tests were carried out. Two types of fatigue fracture mechanisms were observed; in the former was an interface delamination mode and in the latter was a coating fracture mode. In the case of the interface delamination mode, substrate roughness strongly affected the fatigue strength of the sprayed specimen; the rougher the substrate surface, the higher the fatigue strength. This is because rougher substrate leads to higher adhesive strength between the coatings and the substrate. In the case of the specimen failure in the coating fracture mode, the surface roughness of the substrate had no remarkable effect on the faigue strength of the sprayed specimen.

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It is well known that a single tensile overload applied during constant amplitude cycling at a positive stress ratio causes the crack growth retardation. In a case of a negative stress ratio R, however, the fatigue crack growth rate actually accelerated after a tensile overload. This crack propagation behavior is related to the local bulging of specimen thickness, the blunting behavior of crack tips and the residual stress distributions. When the crack tips were blunted during tensile overload and the succeeding compression stress with a high value was applied after the overload, the crack propagation rate got higher level than that before the overload application. In this case, a tensile residual stress was created in front of the crack. To investigate the effect of the negative stress ratio on the fatigue crack propagation, the fatigue tests under R=0, -1 and -1.5 applying the single tensile overload were performed using annealed 0.15% carbon steels. In the present study, a residual life after an overloading was specially investigated, and it was found that the transition phenomenon of the residual life was appeared in the case of the negative stress ratio.

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In this paper, a new method was proposed for evaluating the high-cycle fatigue strength of BGA (Ball Grid Array) packages with Pb-free solder and Pb solder due to a vibration. Attaching a weight induced mixed mode stress in the solder ball of a package. To consider the effect of a mixed mode stress occurred in a solder ball and a frequency to fatigue strength of solder ball, a test was carried out with the four kinds of weights which induced the different ratio of nominal normal stress and nominal shear stress in a solder ball (σ_n/τ_n=2, 4, 5, and 6) at various frequencies (10-27 Hz). Based on the nominal shear stress in solder balls, a new evaluation equation to consider the effect of a mixed mode stress in a solder ball was proposed and the scatters of the fatigue strength in Pb-free packages and Pb packages were evaluated with a Weibull distribution. From a successive observation of a cross section during a fatigue test, a position of crack initiation and a propagation path were found out. Although an intermetallic compounds in both of packages were confirmed by an EDX microprobe analysis, they don't contribute to the initiation of a crack in a solder ball.

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The effect of mode mixty on fatigue crack growth behavior from delamination was investigated with UD laminates (made of unidirectional laminates) and C laminates (made of unidirectional laminates and cloth laminates) of high strength glass fiber reinforced plastics (GFRP).Fatigue crack growth tests were carried out by mixed mode bending specimens at a stress ratio of R=0.1. In UD and C laminates, the crack propagation rate da/dN decreased as mixed mode ratio G_{I max}/G_{T max}decreased when compared at the same total maximum energy release rate G_{T max} (=G_{I max}+ G_{II max}). At a constant crack propagation rate under mixed mode loading, the driving force is expressed in terms of a linear combination of the pure mode I G_{I max}and the pure mode II G_{II max}. The G _{T max} in C laminates approached the G_{T max}in UD laminates as G_{I max}/G_{T max}increased at the same crack propagation rate. In UD and C laminates, fiber bridging took place at G_{I max}/G_{T max}=0.70 and the crack propagation rate was expressed by a power function of the maximum value, G_{T tip max}, of the energy release rate at the crack tip. Fractographic observation UD and C laminates showed that the crack propagation path was on the surface of fibers at G_{I max}/G_{T max}≤0.41 and some resin facture was observed at G_{I max}/G_{T max}=0.70.

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The effects of factors affecting the hammer vibration in Shore hardness testing have been studied. The motion of a hammer was numerically investigated using an elastoplastic finite-element mathod, and was also experimentally studied using a laser doppler vibrometer. Five types of metals were used as specimens, that is, 70/30 brass, 0.54% carbon steel, maraging steel, rail steel and bainitic steel. Although bainitic steel had almost the same hardness as the rail steel, the amplitude of the hammer vibration after the impact for bainite steel was about twice that for the rail steel. By comparing the spectrum of the impact force with that of the hammer acceleration after the impact, it has been clarified that the hammer vibration depends on the wave of the impact force with the frequency, which is the same as the natural frequency of the hammer. The wide difference of the hammer vibration between rail steel and bainitic steel can be explained by the effect of the stress-strain curve on the time variation of the impact force and its spectrum.

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The present paper shows an experimental verification of the impact force identification method developed in the author's previous paper. First, the outline of the impact force identification method based on the relationship between an impact force and the corresponding strain responses is described. In order to discuss the validity of the present method, an impact force identification system is constructed for CFRP laminated plates with PZT piezoelectric sensors. Once an impact acts on the plates, the system that consists of several sensor networks and signal processors can identify both the location and the history of the impact. The experimental results with the plates under two different support conditions are reported. According to the identified results of force location and history, the validity of the present method is verified, and the influence of the modeling error in the finite element model is also discussed.

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The zinc coated steel sheet has been often used for automobile and other industries because of its high corrosion resistance. This paper deals with the development of new ceramics support roll used for a continuous galvanizing pot to manufacture stable galvanized steel sheet. Usually stainless steel rolls are used to support and stabilize the strip in a continuous galvanizing pot, which is filled with molten zinc. However, corrosion and abrasion arise on the roll surface only in a few weeks, and causing the deterioration of quality of plating. Although developing ceramics rolls is most desirable, sometimes fracture occurs when the ceramic roll dips into molten metal. In this paper, therefore, how to reduce the thermal stress is considered when the ceramic rolls are installed in molten metal bath using finite volume method and finite element method. The usefulness of silicon nitride having extreamly high conductivity is also discussed.

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In orthopedic field, various new treatments of articular cartilage defect, for example autogenous osteochondral grafts, have been developed. With the spread of these treatments, orthopedists began to focus on the mechanical properties of recovered articular cartilage. The quantiative evaluation of articular cartilage before and after these treatments gives orthopedists the important information to improve these treatments and develop new treatments. We have been investigating the non-contact ultrasonic evaluation for articular cartilage under arthroscopy. In this paper, it was hypothesized that the ultrasonic evaluation depended on the collagen fiber in cartilage. The enzymatically degradation of collagen fiber in cartilage surface was performed. The effect of the degradation on sound velocity, attenuation coefficient and signal intensity, which is the index of cartilage stiffness calculated from the proposed method, was measured. The numerical analysis was performed to clear the relation between the cartilage character and ultrasonic parameters. Experimental and numerical results suggest that the present method can be expanded the sensitive evaluation for cartilage disease in clinical field.

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Nondestructive evaluation method of the density and mean diameter of small defects in the material using wavelet analysis of scattering ultrasonic waves was developed. The relationship between scattering ultrasonic frequancy characteristics (noise energy and center of the frequency) and defects characteristics (diameter and volume density) was determined by numerical calculations. Scattering ultrasonic was detected using 50 MHz forcused transducer for Al-Si sintered materials ; relative density were 99.56%, 99.52% and 99.22%, mean pore diameter were about 2 μm. From the experimental results, it was found that the defects characteristics can be evaluated from the wavelet analysis of scattering ultrasonic.

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The thickness effect of three point bend (3 PB) specimen on dimple fracture behavior is studied experimentally and numerically. At first, fracture toughness tests were conducted using 3 PB specimens with different thicknesses. Fracture toughness values and R-curves are obtained and the thickness effect is discussed. Using Scanning Electron Microscope (SEM), dimple fracture surfaces are observed precisely. It is found that the thickness effect appears clearly on the void growth process. FEM analyses are conducted based on these experimental data. Using Gurson's constituteve equation, nucleation and growth of void during dimple fracture process is simulated. The distribution patterns of stress triaxiality and crack growth process are obtained. The results show good agreement with experimetal ones qualitatively. The effect of the specimen thickness on R-curves are explained well based on these numerical simulation.

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A statistical analysis of ductile fracture surface was performed on JIS FCD400 spheroidal graphite cast iron with ferritic matrix. Both the notched specimens with different notch acuity and the unnotched specimens were employed to obtain a wide range of stress triaxiality. All specimens were loaded to break under tensile loading at room temperature. The maximum nominal stress to break the specimen increased slightly with stress triaxiality, compared with structural steels. However, the extreme value probability of the maximum dimple size in a given unit area showed a clear dependence on the maximum nominal stress. In addition, the lateral growth factor of the maximum dimple against the graphite size increased due to an increased level of transverse stress with stress triaxiality. Thus, the extreme value analysis of the maximum dimple size and the lateral growth factor of the maximum dimple should be expected for providing a positive and quantitative information regarding the fracture behavior of the ductile cast iron.

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In the present paper, mechanical properties of the carbon-nano-fiber reinforced plastic are discussed. Two kinds of carbon-nano-fiber are employed for the filler of the composites, namely vapor grown carbon fiber (VGCF) and cups-stacked carbon nanofiber (CNF (CS)). For the matrix of the composites, three kinds of thermoplastic resin are used which are polypropylene (PP), polyamide (PA 12) and poly-ether-ether-ketone (PEEK). 3-point bending test using short beams are executed to obtain the anisotropic properties of the specimens processed by injection molding. Standard tensile tests are executed to evaluate the stress-strain relation, tensile strength and elastic moduli of the composite materials. Furthermore, Mode I fracture toughness of the composite are evaluated using center-notched flexure specimens. These mechanical properties and characteristics for the specimens are compared and discussed in detail, and the fracture aspects are investigated by scanning electron microscope (SEM).

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To evaluate the strength of porcelain enamel, it is useful to examine a new evaluation method, which considers the fracture criterion of the surface glass layer and the interface bonding strength between the layers and based steel plate. The steel ball dropping test heretofore in use, due to the effect of specimen dimension and the cramping method of specimen, does not precisely reflect the influence of sintering temperature. The steel ball indentation test is combined with AE method to confirm the estimation of initiative load of ring crack, which occurs on glass surface. Furthermore, for the spherical indentation model with a cone crack, FEM analysis is possible to estimate the interface crack initiation of porcelain enamel. This is done by using the observed propagate direction in the cone crack and by determining experimental fracture toughness through SLJ and DCB specimens. This initiation load was estimated to be near the initiative load of ring crack when using the AE method. It is possible to evaluate the strength of porcelain enamel using the steel ball indentation and AE method.

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