In recent years, investigations into the changes in the microstructure during the processing of functional metal materials have been carried out by many researchers. Therefore, it is required that the change in the material characteristic during processing by a nondestructive evaluation method be evaluated. However, conventional technology has been restricted to a static material characteristic evaluation. For example, a strain gauge has the problem that it can influence the measurement conditions of the tensile test and can only evaluate the position at which the strain gauge is attached. We then tried to develop a non-contact stress measurement system for tensile testing using an EMAT with a Lamb wave as a first step for the material characterization evaluation during a mechanical testing. The EMAT measures the propagation time of a Lamb wave between the receiver and a transmitter during the tensile testing. The interval between the transmitter and the receiver of the first set is 10 mm and can move in the direction of the tensile load. In this presentation, the specifications of the measurement system and the evaluation results are reported

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In the present study, we clarify the micro- to mesoscopic deformation behavior of semi-crystalline polymer by employing large-deformation finite element homogenization method. 3D structure of lamellae in the spherulite of high density polyethylene is modeled, and tensile/compressive deformation behavior was investigated. A series of computational simulation clarified the difference in degree of strain hardening of tension and compression due to different directional orientation hardening. The localized deformation appears depending on the initial distribution of lamellar direction and interaction with surroundings in the mesoscopic area. These mesoscopic deformations are closely related to such microscopic deformation behavior as the rotation of molecular chains which is characterized by the stretch direction and principal slip system in the crystalline phase. Furthermore, interlamellar shear and normal strain in the amorphous phase generally depend on the direction of initial lamellar normal, however, marked scattering is observed due to the interaction with surroundings.

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This paper suggested one method to analyze a contact problem of two elastic bodies with sliding. The analysis is carried out by using a geometrical condition defined by an angle change of contact surface, meanwhile, a dynamical condition defined by equilibrium of force and the Coulomb's friction law. From the comparison of present results with ones by Hertz static analyses and ANSYS, the availability of this method is clarified.

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A testing for bent fatigue crack propagation under mixed-mode conditions was carried out using fatigue and annealed slant precracks with different slant angles, β, defined as the angle between loading and precrack directions in a rectangular plate. As a result, bent fatigue crack from the fatigue precrack with β=45 deg. propagated under mixed-mode conditions with mode II stress intensity factor (K_II) _est evaluated from the discontinuous displacement measured along the crack. On the other hand, bent fatigue crack from the fatigue precrack with β=60 deg. and from the annealed precracks with both slant angles of β=60 deg.and β=45deg, propagated under the mode I behavior. This was because the compressive residual stress near the fatigue precrack caused contact to each other between the upper and the lower surfaces of the precrack with the smaller slant angle β. The estimated fracture angles, θ _est, calculated using (K_I) est and (K_II) _est corresponded to the measured fracture angles, θ _mes, even for the bent fatigue crack propagation under the mixed-mode condition containing the mode II component. Furthermore, the fatigue crack propagation rates indicated almost the same relationship for all the data, using the mixed-mode effective stress intensity factor (K_M) _est, calculated from the discontinuous displacement measured along the bent fatigue crack.

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In Renormalization Group MD (RGMD) performed using atomic-cluster-based particles, Inverse Renormalized MD (IRMD) is carried out on specified occasions to observe atomic motion in clusters. Then, on the begining of the IRMD, it is necessary to determine initial positions and velocities of atoms in clusters such that physical and/or mechanical coditions of clusters are consistent with those of member atoms. This paper proposes a new method, in which the intial model of the IRMD is generated taking into account the equilibrium of forces in and between clusters, incremental strain state and temperature in clusters. Initial model generation based on the new method has been carried out, for a case of Mode I crack propagation, using an RMD model extracted from MD simulation. It is shown that an initial model containing amorphous state around a crack tip can be generated using the proposed method.

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We investigated the mechanism of crack propagation in micro-solder joints in a semiconductor structure and developed a new crack propagation model. In micro-solder joints, solder crack might propagate not only at the interface itself but also near the solder and land interfaces. Conventional crack propagation models based on fracture mechanics, however, cannot explain this phenomenon. In our model, the fatigue life of solder is evaluated based on the damage that accumulates during crack propagation, and the crack paths are automatically calculated. Using this model, we analyzed the crack path of a ball grid array (BGA) structure and determined that this model can reproduce two-dimensional crack paths.

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JSME code on Fitness-for-Service for nuclear power plants defines allowable flaws for Class 1 vessels and piping in the Acceptance Standards. When the size of a detected flaw during in-service inspection does not exceed the size given by the Acceptance Standards, the flaw is accepted for continuing service without any analytical procedures. When a detected flaw is a subsurface flaw located near component surface, the subsurface flaw is transformed into a surface flaw. This paper describes the inconsistency of the subsurface transforming to surface flaw in the Acceptance Standards. Authors have developed an improving method and propose revised subsurface flaws for the Class 1 vessels and piping in the Acceptance Standards of the JSME Code.

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The effect of hydrogen on fatigue crack growth behavior and ductility loss after fatigue cycles of austenitic stainless steels, SUS 304 and SUS 316, was investigated. In the hydrogen-charged specimens, the crack growth rates were approximately twice higher than those of the uncharged specimens for crack growing from 100μm to 1000μm. The aspect ratio for the crack with 2a≥800 μm was smaller in the hydrogen-charged specimens than in the uncharged specimens due to higher hydrogen content in the surface layer than in the subsurface. The slip band density around the crack in the hydrogen-charged specimens was less than in the uncharged specimens. The ductility loss was measured by tensile test carried out by interrupting fatigue test. There was a critical crack length for a decrease in ductility. There were no definite differences in ductility loss between the hydrogen-charged specimens and the uncharged specimens within the hydrogen content and the test strain rate of this study. The ductility loss in hydrogen-charged specimens was dependent only on the length of the main crack produced during fatigue cycles. Although many small cracks were observed on the surface of hydrogen-charged specimens, they did not give more influence on the ductility loss than fatigue cracks. These small cracks were nucleated by the synergetic effect of the hydrogen contained in specimen, the applied tensile stress and the martensitic transformation which was detected after tensile test.

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The non-combustible Magnesium alloy was developed by the present authors. The ignition point was raised to 1000K by adding calcium in this material.In this report, specification of a fatigue crack origin and N=10⁷ fatigue strength of 3 kinds of non-combustible Mg alloy was discussed. Consequently, it was clarified that fatigue crack origins of all materials are inclusions and that the material containing more Al is higher N=10⁷ fatigue strength. Moreover, the fatigue strengths at N =10⁷ of these materials were successfully estimated on the basis of the inclusion size distributions in the material.

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The present study investigated experimentally the effects of temperature and pressure upon effective thermal conductivity of packed bed of magnesium alloy particles. The test particles made of AM50A or AZ91D were poured into a cylindrical vessel and were applied a given superficial pressure for six hours under a constant temperature condition. The superficial pressure was changed between 2.5 MPa and 10 MPa, and the temperature was varied from 95.5°C to 457°C. After removing the packed bed of magnesium alloy particles from the cylindrical vessel, the measurement of effective thermal conductivity was carried out under the steady state comparison method. The effective thermal conductivity increased with an increasing in the pressure, temperature and the thermal conductivity of the particle. At a given material of particle, the effective thermal conductivity was mainly dominated by the relative density and was increased with an increasing in the relative density. The dependency of the effective thermal conductivity upon the relative dencity was remarkable in the low relative dencity region and the high relative dencity region.

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Residual stress is generated in ceramic spraying coatings, which were fabricated by a plasma spray technology, by difference of coefficient of thermal expansion between the coating and the substrate. From previous experimental results obtained by X-ray diffraction method and strain gage method, it is known that the residual stress at the ceramic coating surface is in tensile for as-spray one. In this study, the evaluation method that can predict exactly such residual stress is suggested based on an actual thermal spray process. Residual stress model proposed in this method is consisted of (1) quenching stress, which was formed in molten spray particles impinged onto the substrate, and (2) thermal stress, which was generated by difference of thermal expansion between the particle-deposited layer and the substrate. It was shown herein that residual stress estimated by the proposed model almost coincides with experimental one with a good accuracy.

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In the present paper, numerical simulation about press forming process of glass lens using finite element method is investigated. It is well known that constitutive equation (elastic constants) of glass depend on time-history and temperature. Therefore, stress relaxation or creep arise on the glass subjected to applied loading, and these behaviors vary drastically depending on the temperature. In the present study, creep test has been conducted to determine the thermo-viscoelastic properties of glass. The creep function obtained by the experiment has been transformed into relaxation function employing Laplace transform and its inversion. Shift factor which gives the relation between the time and temperature can be determined by creep test under several temterature, too. Using typical glass “TaF-3” which has been used for press forming, some numerical simulation by FEM are demonstrated. Residual stresses and residual deformations under some processing conditions are estimated, and the optimal conditions of forming process for glass lens are discussed in detail.

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We evaluated the strength of thermally sprayed Al₂O₃ on aluminum. The thermally sprayed Al₂O₃ films were processed using low-pressure plasma spraying. The thickness of the thermally sprayed Al₂O₃ was 0.3 mm and 0.7 mm. We used a 4-point bending test and a heating test to evaluate the strength of the thermally sprayed Al₂O₃. We also investigated the effect of residual stress on the strength by measuring deformation of the thermally sprayed Al₂O₃ after removing the aluminum substrates. The bending strength was 120 MPa, regardless of thickness. We assumed that the bending strength equaled tensile strength because the thermally sprayed Al₂O₃ films were very thin. A crack was generated at 433 K, regardless of thickness. The thermal stress was 160 MPa when the crack was generated. It was 40 MPa higher than we estimated. We found that the residual stress was compression stress that measured 40 MPa, which contributed to the prevention of the crack generation. We presume that the tensile strength was lower than the thermal stress because the residual stress was reduced by the relaxing of the stress of the aluminum near the interface in the bending test.

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The residual stress and deformation behaviors of rectangular plate, induced by the inherent strain of surface controlled layer due to manufacturing processes, was clarified by a polynomial expression using the dimensionless parameters of σ· (1-ν_c) / (E_c·ε₁) and u·T/ (L²·ε₁). (σ : residual stress, ν_c : Poisson's ratio of coating, E_c : Young's modulus of coating, ε₁ : inherent strain of surface controlled layer, u : displacement, T : thickness of substrate and L : length of substrate) We made clear the rectangular plate size for measuring the inherent strain of surface controlled member with high accuracy for preventing the plastic deformation effect of substrate and the cracking effect of surface controlled layer in case of the blasted mild steel.

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The mode III crack growth tests were carried out by edge crack torsion specimens under cyclic and monotonic loadings 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). The test results of mode III crack growth were compared with those of mode I and II. The fracture toughness, G_IIIR, was nearly constant during the crack extension of about 2 mm for UD and C laminates. The fracture toughness value for UD laminates was much lower than that of C laminates. The fracture toughness increased in the order of mode I, III, and II. Fatigue crack growth tests were carried out at the stress ratios of R =0.1, -0.5, and -1. In the low growth rate region, the crack growth behavior was controlled by the range of the energy release rate, ΔG_III, in UD and C laminates. The threshold value of the range, ΔG_IIIth, was independent of the stness ratio in UD lanninate, while, in C lanninates, the value of ΔG_IIth at the negative stress ratio was about 1.6 times larger than at positive stress ratio. In the high growth rate region of UD and C laminates, the crack growth behavior was controlled by the maximum value of the energy release rate, G_IIImax, as in the case of mode II.

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The elliptic growth behavior of interlaminar fatigue cracks from internal circular 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). The fatigue growth tests were carried out using specimens with circular delamination by 3 points bending at the stress ratios of R=0.1 and 1, and tests results were compared with those obtained for through-thickness cracks. The interlaminar crack extended in an elliptic shape under mode II and III deformation. In UD laminates, the growth behavior of the elliptic crack under pure mode II and III agreed with that of the through crack under a respective mode. In the case of C laminates, the crack growth behavior of the elliptic crack under pure mode III agreed with that of the through cracks under pure mode III, while the crack growth resistance of pure mode II of the elliptic crack was about 1/2 of that of through cracks. This difference comes from an error in the G-value evaluation of elliptic cracks performed using the macroscopic mechanical propertis on elastic orthotropy. The G value for actual cracks is larger than the evaluated value, because the resin rich region near the crack tip increases the deformation. At a constant crack growth rate under mixed mode loading, the driving force is expressed in terms of a linear combination of the pure mode II G_IImax and the pure mode III G_IIImax.

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Strength of MEMS micromirror is greatly affected by various kinds of ICP-RIE damage. Notching is one of the most important etching damage in MEMS fabrication process. Many experimental approaches toward notching-free process have been carried out. We have proposed a dual-direction bending test method for evaluating the strength of the notching damage subjected to torsion loading. Proposed method is applied to two kinds of specimens involving different etching damage and same geometry. As a result, it is found that the strength of the specimen with 0.25μm notching roughness is 1 148 MPa and that with 0.13 1, Lm is 1 353 MPa. It exists linear relationship between notching roughness and strength. As the roughness decreases 0.1μm, the increase in the strength of about 230 MN can be observed.

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MEMS micromirrors have been used in optical switches and scanning devices. In these kinds of applications, the beams supporting the micromirror are twisted and deformed to a large extent. Consequently, these single crystal silicon beams have failed catastrophically from brittle fractures. In this paper, a simple fracture test method for the torsional strength of MEMS micromirror has been proposed. This method can be realized through the improvement of the previously proposed bending-torsion combined loading test with respect to the specimen dimensions and loading configuration. The developed method was applied to the actual specimens and it was obtained that shape parameter is 4.40 and scale parameter is 1 575 MPa. From the observation of fracture initiation point, it was found that the torsional fracture has taken place competitively at the sidewall subjected to high stress and the notching region involving high etching damage. Therefore, the proposed simple torsional test realizes the evaluation of the torsional strength of MEMS micromirror, which is governed by inhomogeneous defect and stress distributions.

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In this study, we performed a tensile test on as-received, quenched and tempered S 45 C steel samples using the intelligent universal test machine and measurement of the yield point and the elasticity-plasticity transition point from the relationship between stress and strain rate, thereby obtaining the following results. (1) As for the tempered material, only the upper yield point appeared using the intelligent universal test machine. (2) As for the quenched materials, a clear yield point emerged on the stress-strain curve under appropriate test conditions using the intelligent universal test machine. (3) As for the as-received material, yield points did not appear on the stress-strain curve using the intelligent universal test machine. However, it is possible to find elasticity-plasticity transition point by analyzing the strain rate. We determined that there was an appropriate testing condition for producing the reducibility strain of material to show the yield point and the elasticity-plasticity transition point.

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Using a low frequency range in long-range inspection of a plate with Lamb waves, directivity of Lamb waves becomes weak and Lamb wave propagation is affected by the both sides of a plate. Thus, dispersion curves for a plate with a finite width should be used in nondestructive testing for it. Since dispersion curves for a plate with a finite width cannot be analytically obtained, guided wave calculation technique developed by authors using a semi-analytical finite element method is useful. In this study, therefore, theoretical dispersion curves for a plate with a finite width were derived using the calculation technique, and the characteristic of dispersion curves and the relationship between dispersion curves and vibration distributions were described. And also, the theoretical dispersion curves and vibration distributions obtained by the calculation were verified by experiments in which vibration distributions were obtained by measuring waveforms at many points with a laser interferometer

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Super long life Fatigue properties of Al-Si-Cu Die Casting Alloy were investigated by using ultrasonic fatigue tests at room temperature. The results were compared to fatigue data acquired from conventional fatigue tests, and the fatigue strength were stsudied quantitatively considering the casting defect that was the origin of fatigue crack. The main results obtained are as follows : (1) The S-N curves obtained by using ultrasonic fatigue tests broke in the regime around 10⁷ cycles-as well as conventional fatigue tests. (2) The origin of fatigue crack is casting defect and the fracture surface at around the fatigue crack initiation portion was Mode I fracture surface as well as conventional fatigue tests. (3) From the S-N curve, the fracture mode and etc., ultrasonic fatigue tests seem to be the effective evaluation method of super-long life fatigue properties. (4) Below σ =100 MPa, some specimen were broke, some were not broke. tests seem to be the effective evaluation method of super-long life fatigue properties. (4) Below σ=100 MPa, some specimen were broke, some were not broke. The √area parameter model with casting defect size can explain whether a specimen breaks. but the fatigue limit predicted by the √area parameter model shows the upper level (5) The fatigue limit predicted by the relationship between the stress intensity factor range ΔK_CD obtained from the casting defect size in the regime more than 10⁷ cycles and casting defect size √area are in good agreement with the fatigue limit from the S-N curve.

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This paper reports on a study in which the method of extinction ratio improvement of plane polarized laser which passes the synthetic sapphire which is brazed to a laser device package. The sapphire is used as a semiconductor laser window. Stresses which develop variant azimuths of stress birefringence are applied to the sapphire when the sapphire is brazed to a laser package. As a result, the extinction ratio of plane polarized laser which passes the sapphire is decreased. Variant azimuths of stress birefringence in a brazed synthetic sapphire are narrowed by the increased form birefringence which is induced by tilting the sapphire. Narrowing down the variation of azimuths improve the extinction ratio of plane polarized laser which passes the sapphire. The total azimuth of the birefringence which is the superposition of the stress birefringence and the form birefringence is measured using our scanning optical retardation mapping system. As a result, it has been demonstrated that variance of azimuths of birefringence in the sapphires is narrowed to one hundredth. The extinction ratio of plane polarized laser will increase when the azimuths of birefringence in sapphire coincide with the azimuth of the plane polarizued laser. The narrowing the variance of azimuths of stress birefringence in sapphire allows semiconductor lasers to increase data transmission efficiency.

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Multiple regression analysis was applied to the X-ray stress measurements of silicon single crystal wafer which has the [001] direction perpendicular to the surface. Using an X-ray diffractometer with parallel beam optics, X-ray profiles were recored by a scintillation counter while the specimen was oscillated around two axes. The X-ray measurement conditions were first determined, and then the method was successfully applied to measure the loading stress in a silicon single specimen subjected to four-point bending. The oscillation of the specimen between ±1 to 2 deg during recording was necessary to determine in peak position. An setting error of the specimen position of ±100 μm gave an error in diffraction angle of ±0.004 deg at most, corresponding to an error in stress of 3 MPa. The uniaxial stress was applied in [110] direction (longitudinal direction) of the specimen. Three stress components, σ₁₁, σ₂₂ andσ₁₂ were determined from the measurement of diffraction angles of five diffractions, 133, 133, 313, 3 13, 331, which had the same spacing between diffraction planes. The measured stress of σ₁₁ is 0.993 of the applied stress and the two other components, σ₂₂ and σ₁₂, were nearly zero. Multiple regression analysis was proved to be powerful to determine three stress components of single crystals under the plane stress state. The residual stress in polished silicone wafer was small tension of the order of 10 MPa.

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Crack Energy Density (CED), that is, the parameter that enables a unified description of crack behavior without any restriction on constitutive equation and its applicability had been shown for ordinary materials was extended to piezoelectric body in the previous paper. Taking into consideration this new knowledge about CED, in this paper, the energy release rate for piezoelectric body is discussed and the fundamental matters such as the relations of energy release rate with CED, its derivatives and J integral are elicited. A crack is modeled by a notch with a sufficiently small root radius and a sharp crack is treated as the limit when root radius approaches zero. Energy release rate is derived through two different procedures and it is shown that energy release rate is equal to the electric enthalpy area density, that is, the difference between mechanical CED and complementary electrical CED. Moreover, how mechanical and electrical contributions of energy release rate are given is also discussed.

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Bolt-nut tightening systems are widely used in mechanical structures since the disassembly for maintenance is easy without much cost. However, vibration induced loosening has been unsolved subject. In this paper, we have paid attention to the mechanisms of small loosening process due to micro bearing-surface slip in the framework of the three-dimensional finite element method (FEM). Results show good agreement with Kasei's experimental results. It was found that early-stage nut rotation obtained by the experiments originates from bolt-nut simultaneous rotation induced by tightening torsion of bolt and does not correspond to the loosening rotation. Therefore, loosening rotation must be defined by the relative rotational angle of nut with respect to bolt. It was also found that the small loosening initiates when the vibrational force reaches about 50 to 60 % of that bearing-surface slip occurs. It is necessary to pay attention to the contact state of both bearing surface and thread surface for the consideration of loosening of bolt-nut tightening systems. Contact states are classified into three kinds of states, that is, complete slip involving no sticking region, micro slip involving no ever-sticking region over a vibration cycle, and localized slip involving ever-sticking region over a vibration cycle. A total of nine kinds of contact states are defined by the combination of the bearing surface and thread surface. It is also found that loosening rotation can proceed when micro slip or complete slip occurs at both thread and bearing contact surfaces.

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The dynamic behavior of a rotating circular plate impacting on a plane block of aluminum alloy was investigated experimentally. The approach and rebound velocities during the impacting process were measured using a high-speed video camera. The relationship between the coefficient of restitution, the approach velocity and the rotating velocity was studied on the basis of a modified hybrid nonlinear visco-elastic model. It was found that the rotation had more influence on the coefficient of restitution particularly in the region of lower approach velocities than that in the region of higher approach velocities. However, the coefficient of friction had little influence on the coefficient of restitution

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The dynamic fracture problem for a functionally graded piezoelectric slab containing a center crack parallel to the free boundaries is considered in this study. It is assumed that the electroelastic properties of the medium vary continuously in the thickness direction, and that the slab is under inplane mechanical and electric impact loadings. Integral transform techniques and dislocation density functions are employed to reduce the problem to the solutions of a system of singular integral eqations. The dynamic stress and electric displacement intensity factors versus time are presented for various values of dimensionless parameters representing the crack size, the material non-homogeneity and the loading combination.

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The effect of p-type (B) or n-type (P or As) dopant concentration on the formation energy E_F of point defects in Si crystals during cooling process of Czochralski method was studied with first principles analysis. EF of several charge states of vacancy (V) and interstitial Si (I) was calculated as a function of Fermi level. By considering the dependence of Fermi level on crystal temperature, E_F of the most stable state of V and I in Si crystals was estimated. It was found that V concentration decreases in p-type while increases in n-type Si crystals when dopant concentration is higher than about 1×10¹⁹ atom/cm³. This result well explains the reported experimental results for void formation behavior in Si crystals, i.e., void formation is suppressed by increase in p-type dopant concentration higher than about 1×10¹⁹ atom/cm³, while void formation is enhanced by increase in n-type dopant concentration to about 3×10¹⁹ atom/cm₃. The other calculations showed that, at an initial stage of void formation, the reduction of the total energy of stable P-V_n or As-V_n complex formation was larger than that of stable V_n complex formation from an isolated P or As atom vacancies.

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