LOCAL APPROACH OF FRACTURE BASED ON CONTINUUM DAMAGE MECHANICS AND THE RELATED PROBLEMS
Sumio MURAKAMI and Yam LIU
Review Paper (Vol.2 No.3)
LOCAL APPROACH OF FRACTURE BASED ON CONTINUUM DAMAGE MECHANICS AND THE RELATED PROBLEMS |
|
Sumio MURAKAMI and Yam LIU |
131 |
General Papers (Vol.2 No.3)
EFFECT OF PRESSURE ON THE VISCOSITY B COEFFICIENT OF CESIUM CHLORIDE IN WATER |
|
Takehiro NAKAI, Seiii SAWAMURA, Yoshihiro TANIGUCHI and Yuichi YAMAURA |
143 |
REVERSIBLE ACTUATOR OF SINE-MEMORY ALLOY FILM WITH INVERSE FORCE LAYER |
|
Sotohiro TAKABAYASHI, Hirofumi NABESAWA, Satoshi FUJIKI, Katsumi TANINO and Shin-ya YAMASHITA |
148 |
RESIDUAL STRESS OF ALUMINUM THIN FILMS MEASURED BY X-RAY AND CURVATURE METHODS |
|
Keisuke TANAKA, Keisaku ISHIHARA, Yoshiaki AKINIWA and Hiroyuki OHTA |
153 |
ANALYSIS OF VIBRATION DAMPING PROPERTIES OF HYBRID COMPOSITE WITH FLEXIBLE MATRIX RESIN |
|
Akihiko GOTO, Zenichiro MAEKAWA and Kumiko MIYAKE |
160 |
FRACTURE BEHAVIOR OF ARAMID/EPOXY COMPOSITE NTH A CIRCULAR HOLE SUBJECTED TO COMPRESSIVE LOAD |
|
Hiroyuki KAWADA, Tomohiro WATANABE and Takeshi HONDA |
166 |
SIMULATION OF FRACTURING PROCESS OF WOOD BY FINITE ELEMENT METHOD |
|
Hiroshi YOSHIHARA and Masamitsu OHTA |
173 |
MECHANICAL PROPERTIES AND PHASE STRUCTURE OF YTTRIA-STABILIZED TETRAGONAL ZIRCONIA POLYCRYSTALS AFTER LOW-TEMPERATURE AGING FOR LONG TERM |
|
Manabu OISHI, Yukishige KITANO, Hikaru IWANAGA and Takaki MASAKI |
181 |
FATIGUE CRACK PROPAGATION BEHAVIOR OF Si3N4 CERAMICS IN CORROSIVE ENVIRONMENTS |
|
Takuji OKABE, Gohnojoh KATAYAMA, Mitsuo KIDO and Naoki UDAKA |
187 |
INTERFACE STRUCTURE AND MECHANICAL PROPERTIES OF POWDER METALLURGICAL 6061 ALUMINUM MATRIX COMPOSITES REINFORCED WITH VARIOUS KINDS OF OXIDE WHISKERS |
|
Kenzo FUKAURA, Hisakichi SUNADA, Hitoshi MATSUDA and Yasuhiro HASHIMOTO |
193 |
CREEP RUPTURE OF A UNIDIRECTIONAL SCS-6/BETA21S METAL MATRIX COMPOSITE AT 450, 500 AND 550 Ž |
|
Nobutada OHNO, Teruyuki FUJITA, Takushi MIYAKE, Hiroshi NKATANI and Mamoru IMUTA |
199 |
Short comunication (Vol.2 No.3)
EFFECT OF THE PRECIPITATION OF METAL PARTICLES ON THE ELECTRICAL PROPERTIES OF SnO2-GLASS COMPOSITE | |
Haruhisa SHIOMI, Kaori UMEHARA and Masahiko NAMURA |
207 |
Vol.2 No.3 ABSTRACT
LOCAL APPROACH OF FRACTURE BASED ON CONTINUUM DAMAGE MECHANICS AND THE RELATED PROBLEMS
Sumio MURAKAMI and Yam LIU
Abstract:Recent development of the local approach to fracture based continuum damage mechanics and finite element method together with the related numerical problems is reviewed. After brief description of the concept, procedure and applicability of the local approach, the essential features and the causes of the mesh-dependence of numerical results are discussed. As regularization methods to avoid or to improve the mesh-dependence in time-independent materials, schemes based on localization limiters and nonlocal damage theory are discussed in some detail. The mesh-dependence problem in time-dependent damage, i.e., creep damage, are also discussed. Key Words:Continuum damage mechanics, Local approach, Fracture, Mesh dependence. Strain softening, Bifurcation, Nonlocal damage, Creep damage
EFFECT OF PRESSURE ON THE VISCOSITY B COEFFICIENT OF CESIUM CHLORIDE IN WATER
Takehiro NAKAI, Seiii SAWAMURA, Yoshihiro TANIGUCHI and Yuichi YAMAURA
Abstract:Viscosity of aqueous cesium chloride (CsCl) solution was measured in the ranges of 0.1-5.0 mol kg-1 and 0.1- 375 MPa at 283.2 and 323.2 K. The Jones-Dole B coefficient of CsCl increased with increasing pressure and then decreased passing over a maximum as well as previously observed one at 298.2 K. The maximum B became more remarkable with decreasing temperature from 323.2 K to 283.2 K. These phenomena were compared with the dielectric friction theory supposing solvent water as a continuum fluid. Inconsistency of the theory at low pressure suggested an existence of any structure in water. Pressure dependence of B is ascribed to a balance between the water structure and the dielectric friction effect. Key Words:Viscosity, Cesium chloride. Aqueous solution, B coefficient, High pressure
REVERSIBLE ACTUATOR OF SINE-MEMORY ALLOY FILM WITH INVERSE FORCE LAYER
Sotohiro TAKABAYASHI, Hirofumi NABESAWA, Satoshi FUJIKI, Katsumi TANINO and Shin-ya YAMASHITA
Abstract:The fabrication and processing of an actuator with a TiNi shape memory alloy (SMA) film are discussed and demonstrated. TiNi SMA films were deposited by using sputter deposition techniques, patterned and etched. The films were solution-treated and aging-treated, and then an inverse force layer of chromium was deposited on a SMA film. The frequency response of beam type actuator was measured by the resistance heating. The maximum amplitude was in proportion to inverse force, and was therefore controlled by chromium thickness. The maximum displacement decreased slightly with an increase of frequency. The minimum displacement suddenly increased at more than 0.1 Hz and was constant above 1 Hz. The characteristic of the frequency response of the actuator was not decided by chromium thickness but TiNi thickness, because thickness of the latter was fifteen to forty times larger than that of the former. Because the frequency response depended on the heat radiation of an actuator, TiNi thickness was the most important factor to the actuation. Key Words:Shape memory alloy, TiNi film, Micromachine, Inverse force layer, Reversible shape change, Frequency response
RESIDUAL STRESS OF ALUMINUM THIN FILMS MEASURED BY X-RAY AND CURVATURE METHODS
Keisuke TANAKA, Keisaku ISHIHARA, Yoshiaki AKINIWA and Hiroyuki OHTA
Abstract:The residual stress in aluminum thin films sputtered on silicon substrates was measured by the X-ray diffraction method and the curvature method. Aluminum thin films have a fiber texture with a fiber axis of [111] direction perpendicular to the film surface. In the X-ray method, the residual stress in the films was determined from the strain measurements by using Al 222 and 311 diffractions. The residual stress of as-sputtered films was equi-biaxial tension. The magnitude remained invariant with film thickness and was nearly equal to the value obtained by the curvature method. On the other hand, the residual stress measured by the two methods were different for the films annealed at temperatures above the sputtering temperature (423K). The stress value measured by the X-ray method decreased with annealing temperature; the value by the curvature method had a maximum for the case of annealing at 473K. Line broadening of X-ray diffraction profiles of as-sputtered films was found to increase with increasing thickness. Line broadening increased by annealing at temperatures above the sputtering temperature. Key Words:Residual stress, Aluminum thin film, Silicon wafer, X-ray diffraction, Curvature method, Fiber texture, Equi-biaxial tension, Sputtering temperature, Annealing temperature, Line broadening
ANALYSIS OF VIBRATION DAMPING PROPERTIES OF HYBRID COMPOSITE WITH FLEXIBLE MATRIX RESIN
Akihiko GOTO, Zenichiro MAEKAWA and Kumiko MIYAKE
Abstract:This paper describes an analysis of the damping properties of matrix hybrid composite by Lagrange's equation. The damping properties of matrix hybrid composite are calculated by using viscoelastic properties of homogeneous laminated composite. Two kinds of glass fiber reinforced laminated composites are employed. One is chopped strand glass fiber mat reinforced composites, and the other is unidirectional glass fiber reinforced composite. Hybrid composites of both samples consist of conventional and flexible matrix resins. This analysis method is show to be effective in predicting the loss factor of hybrid composite with flexible matrix resin. Key Words:Damping, Hybrid composite, Flexible resin, Viscosity, Resonance mode, Lagrange's equation
FRACTURE BEHAVIOR OF ARAMID/EPOXY COMPOSITE NTH A CIRCULAR HOLE SUBJECTED TO COMPRESSIVE LOAD
Hiroyuki KAWADA, Tomohiro WATANABE and Takeshi HONDA
Abstract:In this paper, a method for predicting compressive strength of notched AFRP (Aramid Fiber Reinforced plastics) is proposed. The compression tests are performed with an end-tab compression method based on the NASA/Boeing standards. In the experimental procedure, both unidirectional and woven cloth AFRP specimens show the hole radius dependency of the compressive strength. It is also found that the failure modes can be classified by two failure criteria. Therefore, each failure criterion is applied to predict the compressive strength for each failure mode. A fracture simulation is carried out using FEM to predict the compressive strength of the notched AFRP. Fiber micro-buckling is represented by variation of the stiffness of the element at the elastic-plastic stage. The Tsai-Hill law is applied as a yielding criterion, and the maximum compressive strain theory is applied for fracture criterion. The load-displacement curve and compressive strength of the unidirectional AFRP are well simulated. On the other hand, it is found that the woven cloth AFRP is simulated only in the initial failure process. It can be concluded that the proposed fiber micro-buckling model is appropriate to explain the complicated buckling mechanism of laminated composites. Key Words:Composite materials. Compressive strength, Aramid fiber, Fracture mechanism, Simulation
SIMULATION OF FRACTURING PROCESS OF WOOD BY FINITE ELEMENT METHOD
Hiroshi YOSHIHARA and Masamitsu OHTA
Abstract:An existing FEM program for elastic-plastic problems was modified to the one which can be accommodated to the changing of stiffness matrix and the release of stresses at fractured elements. With this program, the fracturing processes of two different mechanical tests of wood were simulated: the JIS shearing test (JIS Z2114) and the JIS bending test (JIS Z2113). The results are summarized as follows: (1) The shearing strength obtained by the calculation was 8.6 MPa. This value agreed with the actual testing data. The fracture initiated and propagated along the grains. This simulated result accorded well with the real fracturing process of the shearing test. (2) The bending strength obtained by the calculation was 127 MPa, which was larger than the actual value because the finite element mesh was rough and thus the scale factors for yielding had been estimated larger. The fracture initiated at the bottom of the specimen, grew to the neutral axis and turned its direction to the grain. This simulated result accorded well with the real fracturing process of the bending test. Key Words:FEM program, Stress-releasing, Fracturing process
Manabu OISHI, Yukishige KITANO, Hikaru IWANAGA and Takaki MASAKI
Abstract:Mechanical properties and phase structure of yttria-stabilized tetragonal zirconia polycrystals aged in air at 200 and 300 deg for 25000 h(about 3 years) were investigated. The bending strength and dynamic hardness of the aged samples were reduced after the aging. The remarkable tetragonal-to-monoclinic phase transformation occurred in surface and sub-surface layers of the sample within 100 mm from the surface. The monoclinic phase fraction of the aged samples, especially aged at 200 deg, was much larger than that of the unaged samples. The bending strength and dynamic hardness decreased drastically when the monoclinic phase fraction exceeded 60%. Several samples were collapsed during the aging at 200 deg of which monoclinic phase fraction finally exceeded 65%. Key Words:Yttria-stabilized tetragonal zirconia polycrystals, Strength, Hardness, Low-temperature aging, Phase transformation
FATIGUE CRACK PROPAGATION BEHAVIOR OF Si3N4 CERAMICS IN CORROSIVE ENVIRONMENTS
Takuji OKABE, Gohnojoh KATAYAMA, Mitsuo KIDO and Naoki UDAKA
Abstract:The effect of corrosion on fatigue fracturing of silicon nitride ceramics was investigated in 1N and 3N H2SO4 solutions. The crack propagation rate da/dt increased when the stress ratio R under cyclic loading was decreased. The higher concentrated solution enlarges the stress ratio dependence of da/dt. Therefore, it is considered that corrosion increases the effect of cyclic loading on da/dt. According to results of an energy dispersive X-ray spectroscopy (EDX) analysis, it was found that the sintering additive components of Al and Y decreased at the crack tip. This suggests that the grain boundary phase at the region dissolved. In addition, a similar effect was also observed by scanning electron microscopy (SEM). Consequently, it is concluded that the dissolution of the grain boundary phase contributes to the increase of da/dt in H2SO4 solutions. Key Words:Fatigue, Corrosion, Silicon nitride, Crack propagation, Sulfuric acid solution
Kenzo FUKAURA, Hisakichi SUNADA, Hitoshi MATSUDA and Yasuhiro HASHIMOTO
Abstract:The compatibility of oxide whiskers with 6061 Al alloy and the age hardening behavior of composites prepared from powder metallurgy were investigated. Interface reactants containing Mg were shown to be formed during hot pressing and hot extruding for every composite. The composites did not reveal age hardening behavior due to the depletion of Mg in the matrix at all. To keep whiskers from the interfacial reaction, electroless nickel plating onto whiskers was carried out. Although the composite with Ni plated whiskers revealed the age hardening, its hot workability was too poor to apply practical fabrication because of the formation of brittle intermetallic compound Al3Mi in the matrix. Key Words:6061 Al Matrix composites, Oxide whiskers, Interface reaction, Powder metallurgy, Electroless nickel plating, Age hardening
CREEP RUPTURE OF A UNIDIRECTIONAL SCS-6/BETA21S METAL MATRIX COMPOSITE AT 450, 500 AND 550 Ž
Nobutada OHNO, Teruyuki FUJITA, Takushi MIYAKE, Hiroshi NKATANI and Mamoru IMUTA
Abstract:Longitudinal creep tests of a 6-ply unidirectional SCS-6/Beta21S metal matrix composite with 38 percent fiber volume fraction were performed at three temperatures of 450, 500 and 550.C at four stresses ranging from 900 to 1350 MPa. Elongation and acoustic emission in the gage section were measured during creep testing, and the specimens were subjected to observation of the fibers exposed by etching the outer matrix layers after creep testing. Also performed were creep tests of the matrix material and tensile tests of the fibers extracted from a virgin specimen. In the creep tests of the composite it was observed that the increase of temperature hastened greatly creep rupture while fiber damage and acoustic emission occurred with little dependence on temperature. It was shown that the activation of matrix creep with temperature is mainly responsible for hastening creep rupture of the composite. Besides it was shown that the fiber bundle strength determined from the tensile tests of extracted fibers is effective in estimating the level of applied stress at which the composite survived long in the creep tests. Key Words:Metal matrix composite, Continuous fiber, Creep, Creep rupture, Temperature dependence, Fiber damage, Acoustic emission