Showing papers in "Journal of The Society of Materials Science, Japan in 1995"
804 citations
Journal Article•
205 citations
TL;DR: In this paper, the authors examined the possibility of X-ray measurement by analyzing the whole part of Debye-Scherrer ring and proposed a new method for the determination of stress without the above approximation on angle η.
Abstract: This study was performed to examine the possibility of X-ray measurement by analyzing the whole part of Debye-Scherrer ring. An imaging plate (IP) was used for the detection of X-ray in order to obtain a high degree of accuracy and efficiency. Through the investigation on the Tanaka's method, we proposed new equations for σy and τxy. We also found that the Tanaka's method involved an assumption that the angle η is constant. So we proposed a new method for the determination of stress from Debye-Scherrer ring without the above approximation on angle η. For the experiment, a new system of processing image data, calculating stresses and a back-reflection Laue camera for IP with a four-point-bending-device was manufactured. The stress applied mechanically with this device was compared to that obtained from the present method. The result showed that it was possible to obtain the stress with the same accuracy as that obtained by the sin2φ method. The advantage of this method is that one can obtain all three components of the stress in a plane stress state from one diffraction ring with single incidence of X-ray beam.
45 citations
TL;DR: In this paper, a simulation technique was applied to predict the residual stress distribution caused by shot peening, and the predicted stress profile shows good correspondence with the experimental value every shot-peening condition of this experiment.
Abstract: It is generally recognized that one of the reasons for improvement on fatigue durability by shot peening is surface compressive residual stress. And a shot peening condition decides a residual stress profile on surface layer. But, at this moment the method to confirm this profile is only measurement by X-ray difractometer. In this study, a simulation technique was applied to predict the residual stress distribution caused by shot peening. Firstly, the residual stress on shot peened plate specimens was measured by X-ray difractometer and the effect of shot peening condition on profile was confirmed. The equation to simulate the profile was obtained by the superposition method of simple three stresses, based on the equation that Y.F. Al-Obaid suggested. It was confirmed that the predicted stress profile shows good correspondence with the experimental value every shot peening condition of this experiment.
33 citations
TL;DR: In this article, a pyrolysis method was applied for recycling of carbon fiber in CFRP, and the recovered carbon fiber has good mechanical properties and a surface condition as those of the original, enough to be used again.
Abstract: A pyrolysis method was applied for recycling of carbon fiber in CFRP. From the results of thermo-gra-vimetry and differential thermal analysis, carbon fiber in CFRP began to be oxidized after almost all the resin in CFRP disappeared by pyrolysis. Consequently, it was possible to recover carbon fiber with an almost 100% yield as a residue by pyrolyzing CFRP under appropriate conditions. The recovered carbon fiber has good mechanical properties and a surface condition as those of the original, enough to be used again.
29 citations
TL;DR: In this paper, the authors developed the viscoplasticity theory based on overstress (VBO) that can model unusual deformation behaviors in metallic alloys and polymers at ambient and elevated temperatures.
Abstract: Transient tests are used to demonstrate unusual or even paradoxical deformation behaviors in metallic alloys and polymers at ambient and elevated temperatures. Included are repeated relaxation tests and creep tests of short duration. It is shown that creep rate need not increase with a stress increase and that, at the same stress level, creep rate can be different on loading and unloading. Also, a stress magnitude increase can be found during relaxation. Once steady inelastic flow is reached, the relaxation rate is nearly independent of the stress and strain at which relaxation starts; it depends mainly on the preceding prior inelastic strain rate. These phenomena can be modeled using an overstress (effective stress) dependence of inelastic rate of deformation and a proper evolution law for a single state variable, the equilibrium stress (back stress) within the context of a “unified” state variable theory. The author and his students have developed the viscoplasticity theory based on overstress (VBO) that can model these unusual behaviors.
21 citations
TL;DR: In this paper, the shape of the yield surface in principal stress space is a part of an ellipsoid whose axis coincides with the hydrostatic stress axis, which qualitatively agrees with experimental observations.
Abstract: We have been investigating in the past the compaction behaviour of powder by particulate modeling in two-dimensions and three-dimensions. This model incorporates plastic deformation of particles at contact besides inter-particle friction, viscous force and gravity. An attempt is made in this study to perform simulation of three-dimensional compaction of powder, where powder is compressed with arbitrary strain rate ratios, and to examine its constitutive behavior, i.e. yield surface and the normality of strain rate vector to the surface. The simulated results show that the shape of the yield surface in principal stress space is a part of an ellipsoid whose axis coincides with hydrostatic stress axis; this qualitatively agree with experimental observations. The normality rule, on the other hand, does not necessarily hold, in particular in a stress state near uni-axial strain compaction.
18 citations
TL;DR: In this paper, the volume resistivity and electromagnetic shielding properties of woodceramics made of porous carbon material were investigated for the purpose of developing a new shielding material, and the measured values of volume resistivities depended on the burning temperature, and changed from 1010Ω·cm to 10-2 ε·cm with increasing burning temperature.
Abstract: The volume resistivity and electromagnetic shielding properties of “Woodceramics” made of porous carbon material were investigated for the purpose of developing a new shielding material.The measured values of volume resistivity depended on the burning temperature, and changed from 1010Ω·cm to 10-2Ω·cm with increasing burning temperature.On the shielding tests with the electromagnetic waves from frequencies of 1000kHz to 1GHz, a good electric shielding effect was observed for those burned above 650°C. When the burning temperature was higher than 700°C, some magnetic shielding effect also appeared. Above 900°C, the shielding effet of more than 40dB on was observed for both of the electric and magnetic shielding in wide frequencies.
15 citations
TL;DR: In this article, a nano-scale polycrystal of pure iron was simulated under static and fatigue loading and a large-scaled slip band formation along each grain boundary was observed.
Abstract: The molecular dynamics simulation of fracture process under static and fatigue loading were done on a nano-scale polycrystal of pure iron, proposed in a previous paper. In the static tension, increasing tensile strain promoted the slip band formation near the grain boundary and finally resulted in microcrack initiation. Formation of subcracks and their growth along grain boundary layer dominated the fracture process at 100K. A large-scaled slip band formation along each grain boundary was observed in the simulation at 700K. The temperature-dependence of fracture process explained well the transition from the cleavage or brittle fracture to the ductile one. Regarding to the fatigue simulation, the fatigue life was decreased with increasing cyclic stress amplitude. At higher stress amplitude, many subcracks were simultaneously formed at the grain boundary and the final failure was dominated by the growth and coalescence of those subcracks. On the other hand, the fatigue fracture was controlled by the primary growth of a single crack formed among the subcracks at lower stress level.
14 citations
TL;DR: In this article, the spatial map of residual stress near welds in ferritic steel socket joints was provided by neutron diffraction measurements of lattice spacings, and the high tensile stress greater than 200MPa was found in the fusion and heat-affected zones in the hoop direction.
Abstract: Neutron diffraction measurements of lattice spacings provide the spatial map of residual stress near welds in ferritic steel socket joints. The high tensile stress greater than 200MPa was found in the fusion and heat-affected zones in the hoop direction. However, the highest tensile stress in the axial direction at the weld root was about 110MPa relatively lower than the expected value from the fatigue test results. The balancing compressive stress was found near the surface of the socket weld fusion zone. Heat treatment at 625°C for 2 hours was sufficient for the relief of residual stress in socket welds.
14 citations
TL;DR: In this article, the diffraction plane dependence of elastic constants in ferritic steel was investigated using a tensile test rig specially degsined for a neutron diffractometer, and the mean elastic constants obtained were E=243GPa and ν=0.28.
Abstract: Neutron diffraction measurement have been made to investigate the diffraction plane dependence of elastic constants in ferritic steel. The measured diffraction planes were 110, 220, 112, 222 and 200. In the measurement a small tensile specimen was loaded in the tensile test rig specially degsined for a neutron diffractometer. The strains obtained for five diffraction planes increased almost in proportion to the applied stress up to 230MPa nearly equivalent to the yield stress. The mean elastic constants obtained were E=243GPa and ν=0.28 for 110, 220 and 112, 182GPa and 0.31 for softest 200, and 268GPa and 0.30 for stiffest 222, respectively. The bulk elastic constants, E=222GPa and ν=0.29, measured by the strain gauges almost agreed with the mean values for 110, 220 and 112. The Kroner elastic model is found to account for the diffraction plane dependence of Young's modulus and Poisson's ratio of the ferritic steel.
TL;DR: In this paper, the microstructural change of a Ti/Al friction weld interface during heat treatment at 673K, 773k, and 873K was described, and it was shown that Si segregation took place before the formation of the Al3Ti phase.
Abstract: This paper describes the microstructural change of a Ti/Al friction weld interface during heat treatment at 673K, 773K, and 873K. TEM/EDS observations of a commercially pure Al/Ti weld confirmed that only the Al3Ti phase formed at the weld interface during heat treatment at 773K or 873K, while no intermetallic compound formed during heat treatment at 673K. The Al3Ti phase was composed of fine equiaxed grains nucleated at the interface boundary and grown up to a few microns in diameter during the heat treatment. Although the Si content was less than 0.12at% in the commercial Al/Ti weld, approximately 5at% Si was solved into the Al3Ti phase and a large amount of Si segregation, almost 20at%, was detected at the Ti/Al3Ti interface. No silicide formed during the heat treatment and the sugregation of Si was always observed. The observation of the specimen heat treated at 673K confirmed that Si segregation took place before the formation of the Al3Ti phase. The faster growth rate of the Al3Ti phase in the highly pure Al/Ti weld at 873K strongly suggested that the Si segregation retarded growth of the Al3Ti phase. The growth rate of the Al3Ti phase heat treated at 873K was in proportion to the square root of the holding time in the early stage of the heat treatment up to 3.6ksec, while it was linearly proportional to the holding time in the latter stage of the heat treatment.
TL;DR: In this article, the authors studied the behavior of mode I interlaminar cracks in a unidirectional carbon/epoxy laminate, Toray T800H/#3631, under cyclic loading at different stress ratios.
Abstract: rowth behavior of mode I interlaminar cracks in a unidirectional carbon/epoxy laminate, Toray T800H/#3631, was studied under cyclic loading at different stress ratios. Under a constant value of the applied stress intensity range, ΔKIap, the crack propagation rate decreased with the crack extension due to crack-tip shielding by fiber bridging. The crack propagation rate was expressed by a power function of the maximum value of the crack-tip stress intensity factor: da/dN=C0(KItip, max/KIc)n, where C0 and fracture toughness KIc are the material constants, while the exponent n strongly depends on the stress ratio. The reduction rate in KItip due to fiber bridging was determined only by the crack extension Δa, but not by the applied load or the stress ratio. The upper bound of the crack propagation rate can be estimated from the scatter of fracture toughness and the fiber-bridging effect of materials. Change in load amplitude has no influence on either the da/dN-KItip, max relation nor the reduction rate in KItip.
TL;DR: In this paper, the authors reported several interesting features in the shape memory alloy observed experimentally under multi-axial complex loading conditions including some temperature changes (the general loading condition).
Abstract: This paper reports several interesting features in the shape memory alloy observed experimentally under multi-axial complex loading conditions including some temperature changes (the general loading condition). The experiments were performed systematically by applying the combined loads of axial force and torque to thin-walled tubular specimen made of a Cu-based polycrystalline shape memory alloy. In these systematic experiments, the strong path dependency of pseudo-elastic phenomenon was observed, and moreover this dependency was disappeared completely only when the materirals went back to the stress free state. This kind of unique behaviour of shape memory alloy may be quite interesting from a view point of new engineering applications of shape memory alloy.
TL;DR: In this paper, it is shown that the Young's modulus changes drastically with plastic deformation and that this is much larger than that estimated from the change in apparent density, and a model that explains this phenomenon is presented.
Abstract: An intelligent V-bending process developed by the authors is briefly described and the importance of change in Young's modulus due to plastic deformation, which influences the amount of springback and therefore the accuracy, is emphasized. The change in Young's modulus in simple tension of a cold rolled steel sheet is experimentally investigated by affixing strain gauges on the specimen. It is shown that the Young's modulus changes drastically with plastic deformation and that this is much larger than that estimated from the change in apparent density. A model that explains this phenomenon is presented. By using the experimentally derived Young's modulus, V-bending process of the same metal is simulated by the finite element method in plane strain; the amount of springback is calculated and compared with the experimental results. It is shown that the springback calculated with the commonly used value of Young's modulus is far less than the experimentally derived one and that the calculation with varying modulus provides the better results. It is thus concluded that, for a better accuracy in sheet bending, the change in Young's modulus due to plastic deformation should be taken into consideration.
TL;DR: In this article, the authors used two kinds of laser cladding specimens to investigate the cladding effect and found that the fatigue life of the laser claddings increased by 2-5 times as compared with the non-treatment specimen, but it was accompanied with a larger scatter in fatigue life and crack growth rate.
Abstract: Laser irradiation treatment is a surface hardening technique developed recently. It has been applied to the improvement of fatigue strength and the prevention of fracture of a cracked specimen etc. But few studies on the laser cladding method have been reported so far, though it is not only efficient to improve the fatigue strength but also can form a heat-, corrosion- and wear-resisting alloy layer on materials. In this paper, fatigue tests using two kinds of laser cladding specimens were carried out in order to investigate the cladding effect.It was found that the fatigue life of the laser cladding specimens increased by 2-5 times as compared with the non-treatment specimen, but it was accompanied with a larger scatter in fatigue life and crack growth rate. The fractography on the fracture surfaces showed the existence of some defects (voids) in the cladding layer. These defects control the fatigue strength and cause the scatter. It was observed that the specimens without large defects were strengthened more notably.
TL;DR: In this article, the authors discuss the effects of different types of transformations on the quality of the environment and the effect of these changes on the performance of the people involved in them.
Abstract: 1 は じ め に 日本刀は,よ く斬れるために必要な硬 さと,折 れない ために必要なじん性 とを兼ね備えている.こ の二つの要 請を満たし,武 器 として優れた機能を発揮することがで きるようになったのは,伝 承と経験によって築かれた刀 匠たちの卓越 した技能によるものである1).この日本刀を 科学的に解明しようという研究はこれまでにもい くつか 行われている2),3).し かし,そ れらは日本刀の化学成分や組 織など,金 属学的立場からの研究がほとんどであ り,力 学的立場からその製作過程を検討 した研究は少ない4).筆 者 らは,す でに相変態を伴う熱 ・力学的現象を解析する ため,温 度-組 織-応力/ひ ずみの連成関係を考慮 した構 成式を5)~11)構 築 し,そ れを用いた解析方法を確立 している. 本研究は,そ の応用 として日本刀の焼入れ過程のシミュ レーシ ョンを行ったものである. まず,焼 入れ過程に至るまでの日本刀の製作過程を簡 単にまとめておく.日 本刀に関わる技術 としては,ま ず, たたらとよばれる日本独特の製鋼法が挙げられる.こ れ は原料として砂鉄 を用い,そ れを1500°C 程度の比較的 低温で還元して作るもので,1800°C 以上の高温で作 ら れる現代の鋼に比べてMnやS,Pな どの不純物が極め て少ないという特長がある.日 本刀はそうして作 られた 玉鋼などを何度も折返し鍛錬 して作 られた炭素濃度の異 なる2~4種 類の鋼を組合わせて作 られる.す なわち, 硬 さの要求 される刃先 には炭素濃度の高い鋼(0.4~ 0.6%C:刃 鉄)を 用 い,じ ん性 の 要 求 され る刀 身 部 に は
TL;DR: In this paper, semi-strand wood particles were collected on a paper sheet on the caul placed at the free-fall distance of 0 to 10 cm from the reciprocating plates.
Abstract: Semi-strand particles (ca. 0.5×2.3×26.4mm) of sugi (Cryptomeria japonica D. Don) were aligned by a laboratory-size mechanical orienter having many reciprocating plates of regular intervals. Wood particles were collected on a paper sheet on the caul placed at the free-fall distance of 0 to 10cm from the reciprocating plates. The pictures of particles on the sheets were fed to an image analyzer equipped with the fast Fourier transform (FFT) function, and transformed to the power spectral patterns after the adjustment of contrast and the removal of window infection. With this procedure, it became possible to evaluate angular distribution of particles quantitatively by the polar coordinate analysis of these patterns.In addition, the surface pictures of particle boards were printed and recorded on papers by a Xerox, and then the degree of particle alignment was estimated by the similar method.
TL;DR: In this article, the compositional dependence of apatite formation on the surface of glasses in the system CaO-B2O3-SiO2 was examined in the simulated body fluid.
Abstract: The essential condition for glasses and glass-ceramics to bond to living bone is the formation of a biologically active bone-like apatite layer on their surfaces in the body. In the present study, in order to investigate fundamentally the effect of B2O3 on the bioactivity of glasses and glass-ceramics, the compositional dependence of apatite formation on the surface of glasses in the system CaO-B2O3-SiO2 was examined in the simulated body fluid. Substitution of small amounts of B2O3 for SiO2 in CaO·SiO2 formula increased the rate of apatite formation on the surface of the glass, while substitution of more than 30 mol% B2O3 for SiO2 decreased it. The substitution of B2O3 for SiO2 in CaO-SiO2 binary glasses accelerated the dissolution of Ca(II) ion from the glasses, and hence enhanced the increasing rate of degree of supersaturation of the surrounding fluid with respect to apatite. The decrease in the apatite forming ability by substitution of large amounts of B2O3 for SiO2 is attributed to the suppression of formation of silica hydrogel layer which plays an important role in apatite nucleation.
TL;DR: In this article, a new grain boundary damage parameter, D-parameter, is proposed to evaluate grain boundaries damaged and to estimate the remaining life of components under creep loading at high temperature.
Abstract: A new grain boundary damage parameter, D-parameter, is proposed to evaluate grain boundaries damaged and to estimate the remaining life of components under creep loading at high temperature. This method is significantly different from the others firstly by specifying the grain boundaries normal to the principal stress direction in the area and secondly by defining the grain boundary damage by coalescence of voids. As the damage is analyzed from the surface structure of components, the replica is inspected by a SEM. The D-parameter method was practiced in in-situ observation of creep deformation for Ni based super alloy by SEM, and found useful for structural materials in which fine voids nucleate, grow and coalesce at the grain boundaries and cause an intergranular fracture.
TL;DR: In this article, the authors investigated the near-threshold growth of delamination fatigue cracks under different stress ratios with unidirectional laminates made from ICI APC-2(AS4/PEEK).
Abstract: The near-threshold growth of delamination fatigue cracks under different stress ratios was investigated with unidirectional laminates made from ICI APC-2(AS4/PEEK). Tests of mode I delamination fatigue crack propagation were carried out by using double cantilever beam specimens. The crack growth rate decreased with crack extension under the constant maximum energy release rate (Gmax-constant) test. The true growth law which is not affected by fiber bridging was obtained by the growth rate at zero-increment of the crack length from a series of Gmax-constant fatigue test. Then, the increase of the crack growth resistance caused by fiber bridging was evaluated. Although the saturated level of this increase was almost the same for both the fatigue and static tests, the length of the saturation for this increase was much longer for the fatigue test than that for the static test. The differences of the crack growth behavior and the stress ratio dependency between the Gmax-constant test and the conventional Gmax-decreasing test were discussed on the basis of the mechanism consideration.
TL;DR: In this article, the electric conduction of woodceramics was investigated to use it as a porous conductor in low temperature and the carrier transport process was discussed, the temperature variation of resistivity was the same as that of semiconductor; it decreases with increasing temperature.
Abstract: Woodceramics is a carbon material sintered from wood or woodymaterial to be used as an industrial material. All the woodceramics has the following characteristics: porous structure, light weight, hard property, heat resistance, anticorrosion and low cost in production. Today, the woodceramics is being studied for practical applications in various fields.In the present study, the electric conduction of woodceramics was investigated to use it as a porous conductor in low temperature. The temperature dependence of electric resistance of the woodceramics was measured in low temperature and the carrier transport process was discussed. The temperature variation of resistivity was the same as that of semiconductor; it decreases with increasing temperature. This semiconductive behavior may be attributed to the intra-layer interaction of π-electron in graphite microcrystals.
TL;DR: In this article, the wear properties of woodceramics were analyzed by using an alumina ball (R=1.5, 4.0mm) or a semispherical diamond pin (R =0.075mm) sliding against a woodceramic plate (MDF-800), under an unlubricated condition in air, under a base-oil impregnated condition and in water.
Abstract: The purpose of this investigation is to analyze fundamental wear properties of woodceramics. For this purpose, wear tests were carried out by using an alumina ball (R=1.5, 4.0mm) or a semispherical diamond pin (R=0.075mm) sliding against a woodceramics plate (MDF-800), under an unlubricated condition in air, under a base-oil impregnated condition and in water. The specific wear rate was calculated from the profile of worn surface in order to evaluate wear characteristics. By introducing the contact pressure parameter (W/R2)1/3, the relationship between the specific wear rate and the contact pressure parameter was obtained. The worn surfaces were observed microscopically by using a scanning electron microscope (SEM) in order to clarify the microscopic wear mechanisms. The following principal results were obtained.(1) The specific wear rate of woodceramics increases rapidly with increasing contact pressure parameter (W/R2)1/3, under the unlubicated condition in air, under the base-oil impregnated condition and in water.(2) When the contact pressure parameter (W/R2)1/3 is less than a certain critical value, the specific wear rate of woodceramics is less than 10-8[mm2/N] which is low enough for practical use.(3) The wear mode of woodceramics can be classified into the following three modes; the large scale brittle fracture induced wear (flake formation), the small scale brittle fracture induced wear (powder formation), and the ultra mild wear (ploughing).
TL;DR: In this paper, a fracture criterion based on the concept of linear notch mechanics for predicting strength in static load is subjected to further theoretical and experimental scrutiny, which examines the effects of notch-root radius and fiber orientation on the fracture behavior of FRP plates.
Abstract: A fracture criterion based on the concept of linear notch mechanics for predicting strength in static load is subjected to further theoretical and experimental scrutiny. An experimental program is presented which examines the effects of notch-root radius and fiber orientation on the fracture behavior of FRP plates. This is accomplished by obtaining experimental data in tension and bending tests on a glass cloth/epoxy laminate (JIS: EL-GEM) containing notches with a wide range of notch-root radii. To examine the effect of fiber orientation on the fracture behavior, the stress distributions near the notch root of notched FRP plates were determined by finite element analysis. The experiment showed that the nominal stress at fracture decreased with decreasing notch-root radius for a constant notch depth. It has been verified that the maximum elastic stress at the notch root when the specimen fails, σmax, c, is governed by the notch-root radius ρ only and independent of type of static load. In other words, the one-to-one relation curve between σmax, c and ρ for notched FRP plates in tension tests agrees well with the curve in bending tests. The fracture characteristics mentioned above was independent of fiber orientation. On the basis of the concept of linear notch mechanics, the experimental results can be clearly explained.
TL;DR: In this article, the application of the homogenization method to those composite structures is discussed, and a method to homogenize the complicated geometry to a simple solid model, to get the homogeneized material constants, and to calculate the microscopic stress is proposed.
Abstract: The effectiveness of the homogenization method for analysis of composite materials has been shown since it was firstly introduced in 1970's. As this method is applicable to periodic problems only, however, some engineering problems remain unsolved. For instance, we could not apply it to honey-comb sandwich plates and panels with reinforcing ribs because these structures are not periodic in the thickness direction. In this paper, the application of the homogenization method to those composite structures is discussed. As a practical example, stress analysis of single-layered corrugated core sandwich plate is presented. A method to homogenize the complicated geometry to a simple solid model, to get the homogenized material constants, and to calculate the microscopic stress is proposed.