THERMODYNAMICAL ANALYSIS OF PSEUDOELASTICITY AND CALORIMETRY IN SHAPE MEMORY ALLOYS
Sei MIURA and Hiroyuki KATO
Review Paper (Vol.1 No.2)
THERMODYNAMICAL ANALYSIS OF PSEUDOELASTICITY AND CALORIMETRY IN SHAPE MEMORY ALLOYS |
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Sei MIURA and Hiroyuki KATO |
67 |
General Papers (Vol.1 No.2)
MODIFIED BLISTER TESTS FOR EVALUATION OF THIN FLEXIBLE MEMBRANE ADHESION ON RIGID SUBSTRATE |
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Kai-Tak WAN and Yiu-Wing MAI |
78 |
STRESS ANALYSIS OF SANDWICH PLATE BY THE HOMOGENIZATION METHOD |
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Naoki TAKANO, Masaru ZAKO and Noboru KIKUCHI |
82 |
FINITE ELEMENT ANALYSIS OF OUT-OF-PLATE DEFORMATION IN LAMINATED SHEET METALS BASED ON AN ANISOTROPIC PLASTICITY MODEL |
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Shoji IMATANI, Takehiko SAITO and Katsuhiko YAMAGUCHI |
89 |
MOLECULAR DYNAMICS SIMULATION ON FRACTURE MECHANISMS OF NANO-SCALE POLYCRYSTAL UNDER STATIC AND CYCLIC LOADING |
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Hideyuki INOUE, Yasuhiro AKAHOSHI and Shoji HARADA |
95 |
NEAR-THRESHOLD PROPAGATION OF DELAMINATION FATIGUE CRACKS IN UNIDIRECTIONAL CF/PEEK LAMINATES IN AIR AND IN WATER |
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Masaki HOJO, Shojiro OCHIAl and Keisuke TANAKA |
100 |
DEPENDENCE OF STRENGTH ON SIZE OF FLAW DOMINATING FRACTURE IN CERAMICS |
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Toshihiko HOSHIDE and Mitsutoshi MASUDA |
108 |
PERCOLATION PROCESS IN ANISOTROPIC CLUSTER-STRUCTURE OF A TWO-PHASE COMPOSITE |
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Katsukuni YOSHIDA and Sizumasa UEDA |
114 |
PREPARATION OF LANTHANUM- AND MAGNESIUM-MODIFIED LEAD TITANATE CERAMICS AND THIN FILMS, AND THEIR PYROELECTRIC PROPERTIES |
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Masafumi KOBUNE, Satoshi FUJII, Ryoichi TAKAYAMA and Atsushi TOMOZAWA |
120 |
VISCOSITY B COEFFICIENTS FOR THE AQUEOUS SOLUTIONS OF TETRAALKYLAMMONIUM BROMIDE UNDER HIGH PRESSURE |
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Yukihiro YOSHIMURA, Seiji SAWAMUWRA and Yoshihiro TANIGUCHI |
126 |
Short comunications (Vol.1 No.2)
A NOTE ON STRUCTURAL FAILURE DUE TO THE GREAT HANSHIN EARTHQUAKE | |
Taijiro NONAKA, Koji MIMURA and Shinji TANIMURA |
132 |
PENETRATION DEPTH OF X-RAYS FOR STRESS MEASUREMENT OF SILICON NITRIDE | |
Kenji SUZUKI and Keisuke TANAKA |
134 |
Vol.1 No.2 ABSTRACT
THERMODYNAMICAL ANALYSIS OF PSEUDOELASTICITY AND CALORIMETRY IN SHAPE MEMORY ALLOYS
Sei MIURA and Hiroyuki KATO
Abstract:The relation between pseudoelastic behavior and the thermoelastic transformation has been studied by means of the measurements of stress-strain curves in the temperature range above and below the martensitic transition temperatures in so called shape memory alloys. Thermodynamical analysis for the pseudoelasticity associated with the stress-induced martensitic transformation has been briefly reviewed and in conjunction with the measurements of latent heat of transformation, the thermoelastic martensitic properties are discussed form a thermodynamic point of view. It was found that using the Clausius-Clapeyron equation concerning the stress-strain relation obtained by the experiments, the enthalpy change was calculated and agreed reasonably well with the experimental values. The importance of the measurement of latent heat, of transformation was emphasized for the justification of thermodynamical analysis of the pseudoelasticity associated with the stress-induced martensitic transformation in the shape memory alloys. Key Words:Thermoelastic martensitic transformation, shape memory effect, Pseudoelasticity, superelasticity, stress-strain curve, thermodynamics, Clausius-Clapeyron relation
MODIFIED BLISTER TESTS FOR EVALUATION OF THIN FLEXIBLE MEMBRANE ADHESION ON RIGID SUBSTRATE
Kai-Tak WAN and Yiu-Wing MAI
Abstract:The blister test geometry commonly used for the measurement of interfacial work of adhesion W has been re-examined and new fracture mechanics analyses are given for thin flexible membranes on rigid substrates in which the stretching deformations are predominant. Two loading configurations are considered. (1) The blister is pressurized under an internal expansion of a fixed mass of working gas. Here stable crack propagation and multiple measurements per specimen are allowed. (2) The blister is loaded by a shaft at its apex, which also gives stable interface crack propagation. The fracture mechanics analyses are verified with simple experiments using sticky tapes on an aluminum plate based on these two test methods. Additional shaft-loaded blister experiments of nylon 6 films on surface treated aluminum substrates have also been studied and compared to the double cantilever geometry. Key Words:Blister test, Debonding, Thin flexible membrane, Gas pressure, Shaft-loading
STRESS ANALYSIS OF SANDWICH PLATE BY THE HOMOGENIZATION METHOD
Naoki TAKANO, Masaru ZAKO and Noboru KIKUCHI
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 honeycomb 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. Key Words:Homogenization method, Sandwich plate, Periodicity, Stress analysis, Corrugated core
Shoji IMATANI, Takehiko SAITO and Katsuhiko YAMAGUCHI
Abstract:An anisotropic plastic constitutive model is applied to a three-dimensional finite element method based on the up-dated Lagrangian type formulation, and out-of-plane deformation of the laminated sheet metal which comprises different materials of stainless steel sheet and aluminum sheet is analyzed. The constitutive model involves a fourth order tensor in its representation, by which not only the initial orthotropy but also the subsequent skewed-anisotropy can be predicted. The variation of anisotropic axis is taken into account with reference to the kinematic relationship of the axis before and after the deformation. The conventional laws of both a power formula for work-hardening and a normality rule for plastic flow are employed in the model. Before the analysis, simple tension tests in various directions are performed to identify the anisotropic material parameters of each component layer. Since the mechanical properties vary in the thickness direction, a fully three-dimensional scheme is adopted in the numerical analysis. Here, we examine the following three kinds of loading patterns: (a)curl in transverse direction under a simple tension, (b) deflection at longitudinal direction in unloaded state following the tension, and (c) strain localization behavior in large deformation regime. The effect of thickness ratio is discussed from the viewpoint of the reduction of out-of-plane deformation, and the difference due to lamination angle is also examined to clarify the combination effect of planer anisotropy. Key Words:Plasticity, Anisotropy, Constitutive equation, Finite element method, Three-dimensional analysis, Laminated sheet metals, Out-of-plane deformation
Hideyuki INOUE, Yasuhiro AKAHOSHI and Shoji HARADA
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 l00 K. A large-scaled slip band formation along each grain boundary was observed in the simulation at 700 K. 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. Key Words:Molecular dynamics, Polycrystalline pure iron, Tensile fracture, Fatigue, Temperature dependence, Fracture model transition, Grain boundary diffusion, Large-scaled slip
Masaki HOJO, Shojiro OCHIAl and Keisuke TANAKA
Abstract:The effects of stress ratio and a water environment on the near-threshold growth of delamination fatigue cracks were investigated with unidirectional laminates made from ICI APC-2 thermoplastic prepregs (AS4/PEEK). Tests were carried out under mode I opening loading by using double cantilever beam specimens. The fatigue crack growth rate near the threshold region was mainly controlled by the stress intensity range rather than the maximum energy release rate and the energy release rate range. The fatigue crack growth resistance of AS4/PEEK laminates was much higher than that of conventional CF/epoxy laminates even near the threshold region. However, the increase in fatigue resistance was smaller than that in fracture toughness. Tests in water did not show large detrimental effects. The crack propagation rate in water was expressed as two power functions of the energy release rate range. The exponent of the power function in the low propagation rate region was smaller than that in the high propagation rate region, and the growth threshold was not observed. The mechanism of the existence of the two power functions was discussed by conducting tests in water at lower frequency of stress cycling. Mesoscopic mechanism of delamination fatigue crack growth in air and in water was discussed on the basis of the fractographic observation. Key Words:Fatigue, Fracture, Composite materials, CFRP, PEEK, Delamination, Crack growth, DCB specimen, water environment.
DEPENDENCE OF STRENGTH ON SIZE OF FLAW DOMINATING FRACTURE IN CERAMICS
Toshihiko HOSHIDE and Mitsutoshi MASUDA
Abstract:Bending tests using a silicon nitride and an alumina were carried out under 4-point bending to clarify the relation between the strength and the size of flaw observed at a fracture origin. When the fracture originated from a smaller flaw, the strength was confirmed to be lower than that expected from the fracture toughness criterion. A convenient procedure using the mean strength and the fracture toughness was proposed to estimate the strength degradation depending on flaw size. A new model was also developed assuming the stable cracking caused by the separation per one grain ahead of a flaw prior to the final unstable fracture. A Monte Carlo simulation based on the proposed model was made to explain the anomalous behavior of small flaw. The relation of strength vs. crack length simulated by taking account of grain-size distribution showed good agreement with the experimental result. The lower bound in scatter of strength depending on flaw-size was suggested to be estimated by using the size of the largest grain expected in a material. Key Words:Ceramics, Small flow, Grain fracture model, Bending strength, Probabilistic method, Grain-size, Monte Carlo simulation, Silicon nitride, Alumina
PERCOLATION PROCESS IN ANISOTROPIC CLUSTER-STRUCTURE OF A TWO-PHASE COMPOSITE
Katsukuni YOSHIDA and Sizumasa UEDA
Abstract:Growing process of the clusters in a composite consisting of niobium (Nb) and alumina (Al2O3), which was fabricated by hot-processing under a uniaxial pressure, has been investigated with particular reference to the structural anisotropy and its effect on the percolative behavior of the electric conductivity s. The percolation transition occurs at the critical volume fraction of Nb phase, fc =0.154 or fc =0.185, depending on the spatial direction. The conductivity obeys the critical power law with a universal exponent t=2 after the transition. The statistic behavior of the structural anisotropy was measured with the aid of an image processor. The relationship between this structural anisotropy and the directional anisotropy of s is well explained by developing the link-node-blob model. The result indicates that the sintered media like the above composite realize a percolation system virtually equivalent to the discrete percolation system produced on the lattice. Key Words:Percolation, Structural anisotropy, Clusters, Critical exponents, Sintered mixture, Two-phase composite, Niobium, Alumina, Image processor
Masafumi KOBUNE, Satoshi FUJII, Ryoichi TAKAYAMA and Atsushi TOMOZAWA
Abstract:Lanthanum- and magnesium-modified PbTiO3 {(1-x). Pb0.9LaO.1Ti0.975O3+x. MgO, x=0-0.025, PLMT)} ceramics and thin films were prepared by normal sintering method and rf-magnetron sputtering method, respectively. The pyroelectric properties of PLMT ceramics and thin films were investigated in detail. The Curie temperature for all samples of both ceramics and films decreased linearly with increasing Mg. The highest figures of merit F.M. for the PLMT ceramics and films were around 0.18x10-10 C.cm/J at x=0.005 and 1.05x10-10 C.cm/J at x=0.010, reaching around 2.8 times and 1.5 times as large as those of PL10 (x=0 in PLT)ceramics and films, respectively. The highest F.M. in PLMT films attained to around 5.8 times that in PLMT ceramics. This is principally attributed to substantial differences in pyroelectric properties (er and P) between ceramics and thin films. Key Words:Ferroelectrics, Pyroelectric infrared sensor, Ceramics, Thin film, Curie temperature, Element material, Rf-magnetron sputtering method
VISCOSITY B COEFFICIENTS FOR THE AQUEOUS SOLUTIONS OF TETRAALKYLAMMONIUM BROMIDE UNDER HIGH PRESSURE
Yukihiro YOSHIMURA, Seiji SAWAMUWRA and Yoshihiro TANIGUCHI
Abstract:The viscosities of aqueous solutions of tetraalkylammonium bromide (R4NBr;R=Me, Et, n-Pr, and n-Bu) were measured in the range of 0.1-1.0 mol kg-1 and 5.0-50.0 deg respectively up to a pressure of 375 MPa, using a high pressure rolling-ball viscometer. The activation energy for viscous flow (Ev) and Jones-Dole B coefficient were estimated. The viscosity vs. pressure minimum at 5.0 deg observed for pure water becomes shallow or disappears with increasing concentration of R4NBr salt and increasing temperature. Ev for aqueous solution of Me4NBr is lower than that of pure water in the whole concentration range under high pressure. Two types of the pressure dependence of the Jones-Dole B coefficients are given. These phenomena were interpreted based on the stand point of pressure, temperature, concentration effects for the structure of water. Key Words:Viscosity, Tetraalkylammonium bromide, High pressure, B coefficient, Activation energy for viscous flow