In this study, a method for reducing the domain of analysis is developed for the homogenization analysis of plain-woven laminates. To this end, by assuming the in-phase and out-of-phase laminate configurations of plain fabrics in laminates, it is shown that the internal structures of the laminates have point-symmetry. Then, the point-symmetry is utilized to the boundary condition for unit cell problems, reducing the domain of analysis to 1/4 and 1/8 for the in-phase and out-of-phase laminate configurations, respectively. Using the present method, the in-plane elastic-viscoplastic deformation of plain-woven GFRP laminates is analyzed. Moreover, the in-plane uniaxial tensile tests of plain-woven GFRP laminates at a constant strain rate are performed at a room temperature. It is thus shown that the present method successfully predicts the in-plane elastic-viscoplastic behavior of plain-woven GFRP laminates. It is also shown that the laminate configurations of plain fabrics have an influence on the viscoplastic behavior of the laminates.

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Generally, reinforcement clusters are formed in a composite. For the case that the rapture strain of the reinforcement in such a composite is smaller than that of the matrix, some of the reinforcements may break in the cluster when the composite is subjected to the external force. Thus the broken reinforcements and the unbroken reinforcements coexist within the cluster. Such a cluster can be regarded as a multi-phase inhomogeneity because the cluster contains different inhomogeneities corresponding to the broken and the unbroken reinforcements. From another viewpoint, the cluster can be regarded as a triple inhomogeneity because a crack exists in the reinforcement and the reinforcements are gathered to the cluster. Therefore, the reinforcement cluster in the composite can be modeled as a multi-phase triple inhomogeneity. As a first step, the multi-phase triple inclusion isolated in an infinite medium is taken into consideration in the present study and the average total strain, the average eigenstress and hence the average interaction strain induced in the multi-phase triple inclusion are derived by adopting the idea of the double inclusion method into the model.

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Carbon fiber reinforced plastics (CFRP) have been well developed for many engineering structural components in the aircraft, automotive and modern space industries with high specific rigidity and high specific strength. But it is poor in vibration and noise reduction as same as many metal materials. In this research, in order to improve the damping properties of CFRP, the innovative CFRP/SDR sandwich composite materials with damping rubber sheet were developed, and the mechanical and damping behaviors were investigated by three-point bending test, center vibration method and dynamic mechanical analysis (DMA), respectively. As a result, it is shown that the mechanical and damping properties of the developed 8 types of CFRP/SDR sandwich laminates depend deeply on the fiber orientation of lamina, the property of rubber sheet and its layer number and sequence. Among these materials, the optimal sequence for the CFRP and SDR sheet was obtained, which showed excellent both mechanical and damping properties.

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Prismatic dislocation loops have so far been observed around the misfitting particle embedded in the matrix. They are generated from the precipitate-matrix interface on which the local shear stress in the maximum. In the present study, the dislocation emissions and the subsequent formation of the prismatic dislocation loop around the inclusion embedded in the single crystalline aluminum or copper matrix are simulated by molecular dynamics. At a result, the maximum shear stress occurs at the precipitate-matrix interface on the {1 1 1} plane intersecting the spherical precipitate at the height of Rp/√2. Afterwards, the prismatic dislocation loops, which have the same gliding direction but not on the same slip planes, are attained by energetically unstable interactions around the precipitate. The representative size of the prismatic dislocation loop is found to depend on the diameter of the precipitate.

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Slip deformation in symmetric-type bicrystal models subjected to tensile load is investigated by a finite element crystal plasticity analysis code. Accumulation of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) are studied in detail. Some results of the analysis show local strain hardening of slip systems and activity of secondary slip systems with accumulation of GNDs on primary slip system in the form of band. Mechanism of local strain hardening of primary slip systems in symmetric-type bicrystals is discussed from the viewpoint of dislocation interaction between primary and secondary slip systems and effects of high density pattern formation of GNDs on primary slip system.

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In the authors' previous study, velocity changes of ultrasonic waves under simple and pure shear states were studied both theoretically and experimentally. The research work revealed the quite different longitudinal wave velocity changes between under the simple and pure shear states and also distinguished longitudinal velocity change under the pure shear state, on the other hand transverse wave velocity changes under simple and pure shear states showed almost the same change tendencies similar to the texture development under both shear states. Therefore, to clear the different effects due to plastic deformation on transverse and longitudinal waves velocity changes under simple and pure shear states the microstructural changes of polycrystal solids were investigated via finite element polycrystal model (FEPM). The analyzed results suggested that the transverse wave velocity depends upon texture developments mainly, whereas the longitudinal wave velocity depends heavily upon point defects induced by intersected cross slips among dislocations. The principal object of this paper is experimental verification of point defects dependence of the longitudinal wave velocity using a pure Aluminum single crystal. As a result, no point defects occurring under single slip stage was simulated by FEM analysis for crystal plasticity and experimental evidence of no longitudinal wave velocity changes under same stage was shown. It was confirmed that the longitudinal waves velocity depends under the point defects.

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This paper is concerned with the method for estimating an erosion surface of refractory brick in blast furnace hearth. The boundary element method (BEM) is used combinedly with a cellular automata (CA) method. The meridional cross-section of the blast furnace hearth is divided into a number of uniform cells, and a state variable defined on each cell is altered by local rules and also a transition rule. The cost function is defined as the square sum of differences between the measured and computed temperatures at some selected points on the outer surface. The minimum value of the cost function is searched in an iterative manner. This paper presents a practical guideline for estimation of the erosion line through numerical simulation. It is demonstrated that there is a region of existing erosion lines which can be well estimated from a several mumber of initial shapes of the erosion line by finding the minimum value of the cost function.

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Stress intensity factor ranges for CT and CCT specimens evaluated by infrared method in the previous studies were almost lower than analytical values. In addition, the difference between measurement results and numerical values increased in proportion to those values not to concern with the stress ratio. In this study, the effect of heat conduction in a body of CCT specimens under cyclic loading was conducted by a finite differential analysis in order to examine the source of the discrepancy between measurements and numerical values. As a result, the error was caused that locations of crack tips were misread due to heat conduction and plastic deformation near crack tips. Thus the method specifying a crack tip from a measurement result has been developed. The stress intensity factors evaluated by using accurate locations of crack tips coincided with numerical values within 7%.

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The intelligent hybrid technique proposed by Nishioka et al. enables to analyze stress intensity factor in high accuracy and reliability from displacement data obtained by experiments. However, the hybrid technique suffers from inevitable error and noise involved in displacement fields on boundary obtained experimentally. In this paper, a modified intelligent hybrid technique is developed to improve the current technique succeeding its characteristic features. With the hybrid technique proposed, it is possible to reduce the influence of experimental errors on the boundary of the concerned area. Therefore this technique demonstrates to set up the actual boundary condition from experimental data and to analyze stress and strain in the full-field on the concerned area in high-reliability and accuracy.

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Rotating bending fatigue tests were carried out on austempered ductile cast iron (ADI) with shot peening (SP) treatment, and influences of the SP treatment on fatigue properties and fracture morphologies were investigated in the long life regime. As a result, improvement of fatigue strength for shot peened ADI specimen was identified before the region of the 10⁷ cycles. Moreover the S-N diagram of shot peened ADI and fatigue limit of non-shot peened ADI cross at over 10⁸ cycles. Then fatigue strength at 10⁹ cycles of non-shot peened ADI was about 360 MPa and that of shot peened ADI was about 280 MPa. To invistigate the reason for fatigue strength reduction of shot peened ADI, residual stress distribution and hardness distribution were measured and fracture origin was observed by SEM. As a result, the reason why the fatigue strength of shot peened ADI decreases more than non-shot peened ADI was that the tensile residual stress had acted inside the specimen. The fatigue limits of shot peened ADI were estimated by casting defects size and actual stress distribution in the specimen.

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It is very important for the damage tolerance design of a structure to reveal the behavior of fatigue cracks of the used material. They have some uncertainties, the random applied loads or the residual strength caused by manufacturing process and so on. It is difficult to evaluate the behaviors of real fatigue cracks. In this paper, an evaluation method for fatigue life based on fatigue crack length has been proposed. Fokker-Planck equation, which can describe fatigue crack propagation under random load and random propagation resistance, has been proposed. The distribution of fatigue life has been analyzed by combining both of the distribution of crack initiation life and the distribution of propagation life.

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A criterion is presented that allows us to predict the effects of phase difference and mean stress on the fatigue strength for hole-containing components subjected to combined load. Combined axial and torsional fatigue tests were conducted using annealed S35C and quenched/tempered SCM435H specimens containing a small hole of either 100 μm or 500 μm in diameter. The phase differences between axial and torsional loads were 0 and 90°. Effects of mean or static stresses were also investigated. The non-propagating cracks emanating in the radial direction from the holes were observed at the fatigue limit. Under the same loading condition, they were present on a plane inclined at the same angle to specimen axis. This suggests that a crack on this specific plane, a critical plane, would play an important role in the determination of fatigue strength. A criterion was proposed on the basis of the assumption that at the threshold level, the time-variation in the mode I stress intensity factor of a crack under multiaxial cylic loading is equal to that under uniaxial cyclic loading. Using this criterion, a prediction method of fatigue strength was also presented. This method is useful since no fatigue test is necessary in making predictions. Good agreement between predictions and experimental results was obtained.

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Threshold stress intensity factor ranges ΔK_th on spheroidal cast irons, which are composed of ferritic, ferrite-pearlitic and pearlitic structures, have been measured by ΔK-increasing tests for small cracks, and by ΔK-increasing and ΔK-decreasing tests for long cracks at several stress ratios. With respect to the effect of hardness and stress ratio, ΔK_th for the long cracks under the ΔK-decreasing tests and ΔK_th, for the small cracks are evidently different, while ΔK_th for the long cracks under the ΔK-increasing tests and for the small cracks are similar. Moreover, regardless of the type of matrix structures, the values of ΔK_th for the long cracks under the ΔK-decreasing tests were larger than those for long cracks under the ΔK-increasing tests. These tendencies are due to the fact that the long cracks under the ΔK-decreasing tests have a relatively higher crack closure stress than those under the ΔK-increasing tests. On the fracture surface of the long cracks under the ΔK-decreasing tests, oxide layers caused by fretting were observed around the crack tip on the surface, although oxide layers were not observed under the ΔK-increasing tests.

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In this paper the problem of a finite crack in a slab of functionally graded piezoelectric material (FGPM) is studied. It is assumed that the elastic stiffness, piezoelectric, and dielectric constants of the FGPM vary continuously along the thickness of the slab, and that the slab is under in-plane mechanical and electric loadings. Integral transform technique is used to reduce the problem to the solution of a singular integral equation. The stress intensity factor and the energy density factor are presented for various values of dimensionless parameters representing the crack size, the material nonhomogeneity and the magnitude of the electric loading.

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The distribution of the residual stress in the thermal barrier coating, which was made by an electron beam-physical vapor deposition (EB-PVD) method, was determined using X-ray stress measurements. As the bond coating, NiCoCrAlY was low-pressure plasma sprayed on the substrate of austenitic stainless steel. The 8 mass% Y₂O₃-ZrO₂ was coated on the bond coating using the EB-PVD method as the top coating. The top coating had the preferred orientation with the <111> axis direction perpendicular to the coating plane. The distribution of the in-plane residual stress in the top coating was measured using laboratory X-rays. The value of the in plane stresses was deter-mined by the sin² φ method after the separation of the 133 and 331 diffractions. The distribution of the out-of-plane strain in the top coating was measured using the strain scanning method with hard synchrotron X-rays. The out-of-plane strain was obtained from the 333 diffraction which had strong intensity due to the preferred orientation. The measured value of the in-plane stress in the top coating was a large compression, and steeply decreased near the interface between the top and the bond coating. The distribution of the out-of-plane stress showed a compression, and its magnitude was smaller than that of the in-plane stress.

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A residual stress distribution in thermal barrier coatings can be measured using the strain scanning method with high energy X-rays from a synchrotoron source due to its large penetration depth. For the double slits optics, the peak aberration of the measured diffraction becomes large, when the gage volume crosses the surface. The analytical correction method for the peak aberration was proposed in this paper. The surface aberration effect was corrected by taking account of the difference between the center of the goniometer and the optical centroid of the gage volume. Using the correction method, the distribution of the residual stress in thermal barrier coatings were measured from the surface to about 0.26 mm inside. For the as-sprayed top coating, the in-plane residual stress was approximately 30 MPa, and out-of-plane stress increased near by interface. For the coating subjected to the heat cycle (1773 K), the both residual stress were relesed.

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In existing literature, the closed-form solution for stress distribution around an elliptic hole has been expressed in the elliptic coordinate in textbooks of theory of elasticity. However, these conventional solutions are inconvenient for application to strength analysis. In the present paper, a new concise closed-form solution for the stress distribution around an elliptic hole under remote uniform stress, σ_x, σ_y, and τ_xy is given in Cartesian coordinate. The analysis of crack propagation path from the elliptic hole under pure shear stress is carried out with combination of FEM analysis. The contradiction between the crack propagation angle from an elliptic hole and that from a crack under pure shear is made clear by the numerical analysis.

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This paper considered three dimensional internal inclined crack growth behaviors due to repeated rolling thermoelastic contact. In this analysis, crack is modeled as an internal inclined planar crack in a three dimensional half-space. Rolling contact is simulated as a long and narrow distributed load with both normal and shear components moving with constant velocity. In comparing the shearing force with the frictional force of crack surface, the phenomenon of stick and slip were considered. At first, stress intensity factors along the crack contour are analyzed using high carbon chromium bearing steels. Next, numerial results of crack growth contours are given based on a modified Paris power low. And fatigue life is estimated by maximum crack growth. The shapes of crack contour and fatigue life are calculated under various conditions, which change sliding ratio, frictional coefficient, angle of inclined crack and friction coefficient of crack surface. As results, when the friction of crack surface is large, the crack progresses greatly in the direction at no friction of crack.

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It is important to know the impact fracture behaviors in the safety design of the brittle material board. However, the three-dimension analysis for the impact fracture behaviors of the brittle material board is not done over the current. In this research, the impact penetration fracture when the impact body collides with the center of the brittle material board is analyzed by PFC 3 D. It is the general three-dimensional program that uses the Distinct Element Method (DEM). DEM is suitable for the analysis of the fracture behavior of the non-individual body and the break-up body. The analytical results are compared with the experimental one and the validity of analytical results are checked. By this research, it is obvious that the penetration speed and the loss energy increase as the impact velocity, radius and mass of the impact body increase. Moreover, the relations between the parameters of impact body and fracture behavior are clarified.

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The thermally tempered glass has strong resistance for the surface crack, because the residual compressive stress exists near the surface of the glass. On the other hand, it also has the residual tensile stress in the center of the glass. Fracture behavior of the thermally tempered glass depends on the distribution of the residual stress. However, it is very difficult to clarify those relationships by an experiment. In this paper, a thermally tempered glass model using the Extended Distinct Element Method (EDEM) is proposed. Using our proposed model, the impact fracture behavior and the crack velocity are evaluated. As results for the normal glass and tempered glass, it is confirmed that the distribution of residual stresses can be evaluated by the thermally tempered glass model and the thermally tempered glass model is broken to many pieces by the residual tensile stress as well as experimental results. Furthermore, it is found that residual stresses of tempered glass greatly influence the crack velocity.

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Since the reason why the wrinkling and breaking occurs is due to the situation, it is very difficult to make the secure measurement of shape and so in press forming. The forming process is designed mainly on the basis of expert's experience until now. In particular, the draw bead is used in order to prevent a wrinkling and breaking. In this paper, an optimum design is developed for determination of length and position of draw bead. The length and position of draw bead are chosen as the design parameters. The formability is evaluated by wrinkling and thickness uniformity of pressed part that is selected as objective functions. The experiments were made in the same condition with analysis. The results by experiments showed good agreement with those by simulations.

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Cavitation erosion was studied for various pure titanium and titanium alloy samples using a rotating disk method in seawater at 303 K, 318 K, and 333 K. Their respective erosion resistances were evaluated in terms of Vickers hardness (HV). The resistance increased in order with increasing hardness : pure titanium samples of first, second, and third types, and titanium alloy (Ti-6Al-4V). The relative temperature was defined as 273 K for freezing temperature and 373 K for boiling temperature under pressurized water. The volume loss rate of test specimens increased with rising seawater temperature within 289-316 K of the relative temperature, as well as in cases using jet and vibratory apparatuses.

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Aluminum casting alloy with high strength, high conductivity, and heat resistance is required as the secondary conducting material for the high speed induction motor. The liquidus of Al-0.5%Zr-xSi (x=0.02-1.0 mass%) alloy were calculated by CALPHAD method, and casting temperature was decided. Effects of Si content on hardness and conductivity changes during aging at 623-723 K of Al-0.5 mass%Zr-xSi alloys cast process in iron mold were studied, and the heat resistance at 423 K for alloy with optimum characteristic was investigated. A small addition of Si accelerated the hardening and high conductivity of the Al-0.5 mass%Zr remarkably. The maximum hardness was obtained by aging at 673 K. Hardness and conductivity of Al-0.5%Zr-0.45%Si alloy aged at 673 K for 28.8 ks was 61.7 HB and 55 IACS%, respectively, and these characteristics in room temperature hardly changed by isothermal treatment at 423 K.

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To improve the reliability of automobile tires and anti-lock braking system (ABS), smart tires that measure strain of tires are increasingly demanded. The high stiffness of an embedded sensor like a strain gage, however, causes debonding of sensors from tire rubber. In a previous study, the authors proposed a tire strain monitoring method that adopts the tire itself as a sensor with a tuning circuit.Since the deformation of a rectangular specimen used, however, is different from that of an actual tire, the tuning frequency does not change linearly with the strain change of an actual tire. In the present study, the monitoring system with a tuning circuit is applied to an actual radial tire using spectral features of peak spectrum and quality factor as well as tuning frequency to improve the accuracy of strain estimation. As a result, the method is experimentally proved to be effective for the passive wireless strain monitoring of actual radial tires.

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The left ventricular wall motion during systole was investigated from a mechanical point of view by using a magnetic resonance tagging technique. Subjects were seven patients with coronary artery bypass grafting (CABG). At first, in order to evaluate the cardiac contractility in each patient, the circumferential strain in myocardial wall was analyzed. It was found from there results that the circumferential strain in four patients decreased compared with that in healthy humans. Next, the paradoxical wall motion in patients with CABG was quantitatively described by calculating the displacement. The results showed that the radial displacement of septal wall in the patients was smaller than that in healthy humans, and the radial displacement of lateral wall was larger. Furthermore, anterior wall and posterior wall moved toward septal wall. Such left ventricular wall motion was recognized in even the patients with normal cardiac contractility. Therefore, it was considered that the paradoxical wall motion in the patients with CABG was not caused by a drop of the cardiac contractility, but a rigid-body motion of the heart.

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