Journal of the Society of Materials Science, Japan
White etching area may be recoginized at the flaking part of a rolling bearing on which high cont... more White etching area may be recoginized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball have been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, internal residual stress distributions of ball by using high energy white X-ray of SPring-8 (A method) and laboratorial Xray measurement equipment (B method) were investigated. The former was moddified by surface residual stress accoding to B method. The latter was modified by releasing stress in the form of electrolytic polishing. The results showed modified residual stress distributions almost agree qualitatively.
Proceedings of the Asian Pacific Conference on Fracture and Strength and International Conference on Advanced Technology in Experimental Mechanics
The titanium nitride (TiN) films with the thickness of O.5, 1,O, 2.0ptm were coated on a steel su... more The titanium nitride (TiN) films with the thickness of O.5, 1,O, 2.0ptm were coated on a steel substrate by the ion beam mixing method, The film had a strong fiber texture with <110> axis perpendicular to the film surface. The initial residual stresses are equi-biaxial compression between-42oo to-55ooMPa. For all thickness cases, the initial part ef the changes of the in-plane stresses in the film due to extemal tensile loading agreed well with the prediction based on elasticity, While the substrate is under uniaxial stresses, the film was in the biaxial state of stress because of the mismatch of Poisson's ratio, When the measured stress in the film exceeds a certain value, the stress departs from the linear relation and levels off. The onset of nonlinearity is coincident with the first appearance of cracks. The stresses at the onset of nonlinearity and leveling-off decrease with increasing film thickness. The ratio of Ydung's modulus between loading and unloading decreases as the film thickness increases, suggesting the increasing disjointed area, Kay woizis : TiN film, Ion beam mixing, X-ray stress analysis, Residual stress, Fracture strength, Reuss model, Four-point bending, Stress-strain curveboading stress,
The Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics
Titanium nitride (TiN) thin films were deposited by the ion beam mixing (IBM) on the steel substr... more Titanium nitride (TiN) thin films were deposited by the ion beam mixing (IBM) on the steel substrate. TiN thin films had a fiber texture with the fiber axis of <001> direction perpendicular to the film surface and the film thicknesses were 0.5, 1.0, 2.0, 4.0µm. These specimens were subjected to four point bending, and the stresses in films and substrates were measured by the X-ray diffraction method at each applied strain. In the examination, the films surface were replicated with cellulose acetate sheets at each applied strain and the replicated sheets were observed by scanning electron microscopy. The initial residual stress was equi-biaxial compression between-3.0,-2.7,-2.3,-0.9 GPa for the cases of 0.5, 1.0, 2.0 and 4.0µm, respectively. For thinner specimens, the rate of the increase of measured value of σ 11 with the applied strain is lower than that of prediction, while for the film with 4.0µm the experimental value agrees well with the prediction. While the substrate is under uniaxial stresses, the film was in the biaxial state of stress because of the mismatch of Poisson's ratio. When the measured stress in the film exceeds a certain value, the stress departs from the linear relation and levels off. The onset of nonlinearity is slightly after the first appearance of cracks and the leveling of the stress was caused by multiple cracks in the film. The maximum stress measured in films increased with decreasing thickness.
Journal of the Society of Materials Science, Japan
Thin films of titanium carbide (TiC) were coated on various substrates such as cemented carbide (... more Thin films of titanium carbide (TiC) were coated on various substrates such as cemented carbide (WC-Co) with different cobalt contents, ferritic and austenitic steels by the chemical vapor deposition (CVD) method. Thin films did surement. The residual stress was tensile for WC-Co substrates, while compressive for steel substrates. The residual stress was nearly uniform within the film thickness for the cases of WC-Co substrates, while it had rather steep distribution for the cases of steel substrates. The magnitude of the residual stress increased in proportion to the mismatch of the coefficient of thermal expansion (CTE). The measured stress was more compressive than the prediction by CTE mismatch. Under the uniaxial applied stress, the stress in the thin film was biaxial because of the mismatch of Poisson's ratio, and increased in proportion to the applied strain as predicted from the elasticity relation of coated layers. At high applied strains, the stress in the thin film measured by X-rays did not increase because of cracking. The tensile fracture strength of TiC films on WC-Co substrates was found to be around 750 to 800MPa. This value is about twice the fracture strength of bulk materials.
Journal of the Society of Materials Science, Japan
Copper thin films with a thickness of 600nm were coated on the undercoating by sputtering. The to... more Copper thin films with a thickness of 600nm were coated on the undercoating by sputtering. The top layer of the undercoating was TiN with the thickness of 50nm sputtered on SiO2 layer on Si wafers. Films were subjected to heat microscopy and scanning electron microscopy, The X-ray diffraction method was used to measure the residual stress intensity ratio of 222 to 200 diffraction increased, while the half value breadth decreased. The residual stress at room temperature was equi-biaxial tension. The residual stress increased from 270MPa before heating to 350MPa after the prediction based on the model proposed by Thouless et al.
Journal of the Society of Materials Science, Japan
Copper thin films with a thickness of 600nm were sputtered on the undercoating. The top layer of ... more Copper thin films with a thickness of 600nm were sputtered on the undercoating. The top layer of the undercoating was TiN with a thickness of 50nm sputtered on SiO2 layer with the thickness of 300nm on the Si wafer. Films
Journal of the Society of Materials Science, Japan
On the bases of Reuss and Voigt models, a new X-ray method is proposed to measure the non-equibia... more On the bases of Reuss and Voigt models, a new X-ray method is proposed to measure the non-equibiaxial state of stresses in thin films which have a fiber texture with <110> axis perpendicular to the film surface. The method was successfully applied to measure the stress in TiN films coated on the steel substrate by the ion-beam mixing method. The film had a strong <110> fiber texture and the initial residual stress was a compression of about-5500MPa. The initial part of the changes of the in-plane stresses in the film due to external tensile loading agreed well with the prediction based on elasticity. While the substrate is under uniaxial stresses, the film was in the biaxial state of stress because of the mismatch of Poisson's ratio. When the measured stress in the film becomes tension, the stress stops increasing even though the applied strain keeps increasing. This leveling of the stress was caused by cracking of the film.
Journal of the Society of Materials Science, Japan
The effect of porosity on the elastic constants for X-ray stress analysis in sintered alumina was... more The effect of porosity on the elastic constants for X-ray stress analysis in sintered alumina was analyzed on the basis of four micromechanics models: Reuss' model, Voigt's model, Mori-Tanaka's model (MT model) and Selfconsistent model (SC model). The X-ray elastic constant E'x/(1+v'x(E'x=Young's modulus, v'x=Poisson's ratio) decreases with decreasing bulk density or increasing porosity. SC model gives the best prediction for the effect of bulk density on the X-ray elastic constants. The prediction based on SC model requires the mechanical elastic constants of sintered alumina as a composite and the X-ray elastic constants of diffracting phases. It is not necessary to know the properties of secondary phases. When the mechanical elastic constants are not known, the bulk density can be used to estimate the X-ray elastic constants of ceramics.
Journal of the Society of Materials Science, Japan
White etching area may be recoginized at the flaking part of a rolling bearing on which high cont... more White etching area may be recoginized at the flaking part of a rolling bearing on which high contact stress of several GPa is applied repeatedly. Up to now, studies of white etching area of a ball have been less than studies of white etching area of inner and outer rings. In this study, as part of the flaking mechanism explication with white etching area of a ball, internal residual stress distributions of ball by using high energy white X-ray of SPring-8 (A method) and laboratorial Xray measurement equipment (B method) were investigated. The former was moddified by surface residual stress accoding to B method. The latter was modified by releasing stress in the form of electrolytic polishing. The results showed modified residual stress distributions almost agree qualitatively.
Proceedings of the Asian Pacific Conference on Fracture and Strength and International Conference on Advanced Technology in Experimental Mechanics
The titanium nitride (TiN) films with the thickness of O.5, 1,O, 2.0ptm were coated on a steel su... more The titanium nitride (TiN) films with the thickness of O.5, 1,O, 2.0ptm were coated on a steel substrate by the ion beam mixing method, The film had a strong fiber texture with <110> axis perpendicular to the film surface. The initial residual stresses are equi-biaxial compression between-42oo to-55ooMPa. For all thickness cases, the initial part ef the changes of the in-plane stresses in the film due to extemal tensile loading agreed well with the prediction based on elasticity, While the substrate is under uniaxial stresses, the film was in the biaxial state of stress because of the mismatch of Poisson's ratio, When the measured stress in the film exceeds a certain value, the stress departs from the linear relation and levels off. The onset of nonlinearity is coincident with the first appearance of cracks. The stresses at the onset of nonlinearity and leveling-off decrease with increasing film thickness. The ratio of Ydung's modulus between loading and unloading decreases as the film thickness increases, suggesting the increasing disjointed area, Kay woizis : TiN film, Ion beam mixing, X-ray stress analysis, Residual stress, Fracture strength, Reuss model, Four-point bending, Stress-strain curveboading stress,
The Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics
Titanium nitride (TiN) thin films were deposited by the ion beam mixing (IBM) on the steel substr... more Titanium nitride (TiN) thin films were deposited by the ion beam mixing (IBM) on the steel substrate. TiN thin films had a fiber texture with the fiber axis of <001> direction perpendicular to the film surface and the film thicknesses were 0.5, 1.0, 2.0, 4.0µm. These specimens were subjected to four point bending, and the stresses in films and substrates were measured by the X-ray diffraction method at each applied strain. In the examination, the films surface were replicated with cellulose acetate sheets at each applied strain and the replicated sheets were observed by scanning electron microscopy. The initial residual stress was equi-biaxial compression between-3.0,-2.7,-2.3,-0.9 GPa for the cases of 0.5, 1.0, 2.0 and 4.0µm, respectively. For thinner specimens, the rate of the increase of measured value of σ 11 with the applied strain is lower than that of prediction, while for the film with 4.0µm the experimental value agrees well with the prediction. While the substrate is under uniaxial stresses, the film was in the biaxial state of stress because of the mismatch of Poisson's ratio. When the measured stress in the film exceeds a certain value, the stress departs from the linear relation and levels off. The onset of nonlinearity is slightly after the first appearance of cracks and the leveling of the stress was caused by multiple cracks in the film. The maximum stress measured in films increased with decreasing thickness.
Journal of the Society of Materials Science, Japan
Thin films of titanium carbide (TiC) were coated on various substrates such as cemented carbide (... more Thin films of titanium carbide (TiC) were coated on various substrates such as cemented carbide (WC-Co) with different cobalt contents, ferritic and austenitic steels by the chemical vapor deposition (CVD) method. Thin films did surement. The residual stress was tensile for WC-Co substrates, while compressive for steel substrates. The residual stress was nearly uniform within the film thickness for the cases of WC-Co substrates, while it had rather steep distribution for the cases of steel substrates. The magnitude of the residual stress increased in proportion to the mismatch of the coefficient of thermal expansion (CTE). The measured stress was more compressive than the prediction by CTE mismatch. Under the uniaxial applied stress, the stress in the thin film was biaxial because of the mismatch of Poisson's ratio, and increased in proportion to the applied strain as predicted from the elasticity relation of coated layers. At high applied strains, the stress in the thin film measured by X-rays did not increase because of cracking. The tensile fracture strength of TiC films on WC-Co substrates was found to be around 750 to 800MPa. This value is about twice the fracture strength of bulk materials.
Journal of the Society of Materials Science, Japan
Copper thin films with a thickness of 600nm were coated on the undercoating by sputtering. The to... more Copper thin films with a thickness of 600nm were coated on the undercoating by sputtering. The top layer of the undercoating was TiN with the thickness of 50nm sputtered on SiO2 layer on Si wafers. Films were subjected to heat microscopy and scanning electron microscopy, The X-ray diffraction method was used to measure the residual stress intensity ratio of 222 to 200 diffraction increased, while the half value breadth decreased. The residual stress at room temperature was equi-biaxial tension. The residual stress increased from 270MPa before heating to 350MPa after the prediction based on the model proposed by Thouless et al.
Journal of the Society of Materials Science, Japan
Copper thin films with a thickness of 600nm were sputtered on the undercoating. The top layer of ... more Copper thin films with a thickness of 600nm were sputtered on the undercoating. The top layer of the undercoating was TiN with a thickness of 50nm sputtered on SiO2 layer with the thickness of 300nm on the Si wafer. Films
Journal of the Society of Materials Science, Japan
On the bases of Reuss and Voigt models, a new X-ray method is proposed to measure the non-equibia... more On the bases of Reuss and Voigt models, a new X-ray method is proposed to measure the non-equibiaxial state of stresses in thin films which have a fiber texture with <110> axis perpendicular to the film surface. The method was successfully applied to measure the stress in TiN films coated on the steel substrate by the ion-beam mixing method. The film had a strong <110> fiber texture and the initial residual stress was a compression of about-5500MPa. The initial part of the changes of the in-plane stresses in the film due to external tensile loading agreed well with the prediction based on elasticity. While the substrate is under uniaxial stresses, the film was in the biaxial state of stress because of the mismatch of Poisson's ratio. When the measured stress in the film becomes tension, the stress stops increasing even though the applied strain keeps increasing. This leveling of the stress was caused by cracking of the film.
Journal of the Society of Materials Science, Japan
The effect of porosity on the elastic constants for X-ray stress analysis in sintered alumina was... more The effect of porosity on the elastic constants for X-ray stress analysis in sintered alumina was analyzed on the basis of four micromechanics models: Reuss' model, Voigt's model, Mori-Tanaka's model (MT model) and Selfconsistent model (SC model). The X-ray elastic constant E'x/(1+v'x(E'x=Young's modulus, v'x=Poisson's ratio) decreases with decreasing bulk density or increasing porosity. SC model gives the best prediction for the effect of bulk density on the X-ray elastic constants. The prediction based on SC model requires the mechanical elastic constants of sintered alumina as a composite and the X-ray elastic constants of diffracting phases. It is not necessary to know the properties of secondary phases. When the mechanical elastic constants are not known, the bulk density can be used to estimate the X-ray elastic constants of ceramics.
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Papers by Toshimasa ITO