※一部利用できない機能があります
| 1.
論文 |
論文
|
馬, 志強 ; 八重澤, 美知子 ; 岡部, 佐規一 ; 広瀬, 幸雄
|
||||
| 2.
論文 |
論文
|
矢島, 善次郎 ; 広瀬, 幸雄 ; 田中, 啓介 ; 小河, 弘
概要:
金沢大学大学院自然科学研究科<br />The fracture toughness tests of ductile cast iron (JIS FCD 60) were conducted at ambient and low tem
…
peratures by using compact tension specimens and three-point bending specimens with fatigue pre-cracks. The distribution of the half-value breadth of X-ray diffraction profiles beneath the fracture surface was determined. Based on those results and electron fractographic observation, the mechanism of fracture in ductile cast iron was discussed as a function of test temperature. The main results are summarized as follows : (1) The size of the plastic zone ω_y determined from the half-value breadth distribution is related to the fracture toughness K_i through ω_y=0.13(K_i/σ_Y)^2 where σ_Y is the yield stress. (2) The fracture toughness decreased with lowering temperature and the fracture mode of the matrix changed from dimples to cleavage. The unique relation was established between the fracture surface strain and K^2_i/σ_Y.
続きを見る
|
||||
| 3.
論文 |
論文
|
津田, 政明 ; 広瀬, 幸雄 ; 矢島, 善次郎 ; 田中, 啓介
概要:
金沢大学大学院自然科学研究科<br />stress corrosion cracking tests were conducted by using the compact tension (CT) specimens of 200℃ t
…
empered AISI 4340 steel in a 3.5 % NaCl solution environment under various electrode potentials. The distribution of the residual stress beneath the fracture surface was measured with the X-ray electron microscopy. The Effect of electrode potential on the growth kinetics of stress corrosion cracking was discussed on the bases of the results of X-ray observation and scanning microfractography. The results obtained are summarized as follows:(1) The residual stress measured on the fracture surface was tension under cathodic potential. It decreased with increasing potential, and changed to compression under anodic potential. (2) The relation between the plastic zone depth ω_y and the stress intensity factor K can be approximated by the following fracture mechanics equation:ω_y=α(K/σ_Y)^2 were σ_Y is the yield strength. The α value was 0.084 under the free corrosion condition and 0.053 under the catholic polarization condition.
続きを見る
|
||||
| 4.
論文 |
論文
|
穐田, 竹男 ; 後藤, 昌英 ; 北川, 和夫 ; 生水, 雅之 ; 広瀬, 幸雄
概要:
Microstructures and mechanical properties of ultra fine-grained low carbon steels fabricated by equal channel angular pr
…
essing (ECAP) were investigated. Several specimens statically annealed for 5 hours at temperatures of 773-873K were studied simultaneously. Electron back-scattering diffraction (EBSD) measurements were carried out for microstructure observation. Differential scanning calorimeter (DSC) curves were obtained for studying the thermal stability of specimens. The initial grain size of ∼10μm in the ferrite-pearlite steel was refined to ∼0.2μm by 4 passes of ECAP. The tensile strength of the as-ECAPed specimen was around 2 times higher than that of the initial normalized specimen, although the ductility decreased by half after the process. At annealing temperature of 773-823K, tensile strength and yield stress decreased as the average grain size of each specimen increased. However the grain growth by annealing was not significant. At annealing temperature of 873K, the nonuniform grain growth occurred suddenly, and as a result the tensile strength decreased. On the Hall-Petch relation diagram, the gradient of the diagram over the average grain size of 1mm was slightly different from that of under 1μm. In addition, the nonuniform radical grain growth at the temperature of 873K was in accord with the appearance of the exothermic peak in the DSC curves. The accumulation of the local strain in the 823K-annealed specimen was investigated by the kernel average misorientation (KAM) approach using EBSD, and it is suggested that accumulation of the local strain in the 823K-annealed specimen is one of the causes of the nonuniform radical grain growth at the temperature of 873K.
続きを見る
|
||||
| 5.
論文 |
論文
|
黒瀬, 雅詞 ; 森川, 晶 ; 津田, 政明 ; 広瀬, 幸雄
概要:
金沢大学大学院自然科学研究科<br />The mechanical properties of materials often decrease due to corrosion. For example, stress corrosio
…
n cracking (SCC) is one of the major issues in this problem, because it is difficult to estimate the remaining life of the materials by SCC. A tarnish film is usually created on the surface of copper during corrosion. SCC for pure copper is attributed to the film. In this study, an attention is paid to the growth of the tarnish film. The specimens used were made of pure copper annealed in a vacuum, and were corroded in 1.0 kmol・m^<-3> NaNO_2 solution up to 100ksec. The experiments were conducted by immersing the specimen in the solution under two different conditions: One at free corrosion and another at several electrode potentials. The brightness of specimen surface changed with corrosion. The film was observed by using a CCD camera; the distribution and the extension of the corrosion were examined by using an image processing technique (IPT). A fractal analysis was applied and the applicability of the fractal analysis was investigated. The fractal dimension was effective to evaluate the corrosion stage of pure copper. The results obtained in this study are summarized as follows: (1) Change in average brightness of images against the immersion time occurred at each point of the more anodic electrode potentials. The brightness values measured by IPT showed the corrosion stage of pure copper. (2) The extension of the corrosion state of pure copper showed fractal characteristics at every electrode potential in the present experimental conditions. The fractal dimension of Dark OR image measured by Box counting method showed remarkable change at the current density corresponding the range of the repassivation potential.
続きを見る
|
||||
| 6.
論文 |
論文
|
増田, 秀夫 ; 鷹合, 滋樹 ; 比良, 光善 ; 広瀬, 幸雄
概要:
金沢大学大学院自然科学研究科<br />Ni-Co-P/α-Si_3N_4 composite plating excels in wear-and corrosion resistance. It is important to eval
…
uate the residual stress due to the misfit of mechanical and physical properties between plating and substrate during the manufacturing and industrial using. However, in the case of plating specimen which have stress gradient, the sin^2Ψ method is not adequate to use because this material shows severely curved sin^2Ψ diagram. In this study, a fundamental investigation was carried out to apply the X-ray residual stress measurement of the plating material. Fourth kinds of specimens with different thickness of film were prepared. X-ray elastic constants were obtained using the non-liner analysis. Influence of the film thickness on curvature of 2θ-sin^2Ψ diagram was simulated. Residual stress in the plating layer was analyzed under the assumption that the stress state is equivalent biaxial. Some experimental results were observed: sin^2Ψ diagrams were severely curved, and shape of diagrams shows varied by the film thickness and X-ray penetration depth. There is the steep stress gradient in the direction of depth. As the results, X-ray elastic constants of all specimens were independent from the thickness of film. Therefore, the value is constantly. A value of residual compressive stress calculated form present method is grater than value of sin^2Ψ technique. Compressive stress decreased with the film thickness.
続きを見る
|
||||
| 7.
論文 |
論文
|
広瀬, 幸雄 ; 津田, 政明 ; 矢島, 善次郎 ; 田中, 啓介
概要:
金沢大学大学院自然科学研究科
|
||||
| 8.
論文 |
論文
|
岸, 陽一 ; 広瀬, 幸雄 ; 佃, 市三 ; 永井, 滋一 ; 東, 健司
概要:
金沢大学大学院自然科学研究科<br />Tensile properties and stress corrosion cracking (SCC) resistance of Al-8 wt.% Zn-1 wt.% Mg system a
…
lloys with various Cu and La contents were investigated.The influences of additional elements on mechanical properties and SCC life were discussed on the basis of experimental results.The results obtained in the present work are as follows;(1) Additions of elements of Cu and La were effective to decrease the grain size of those materials.In particular,the grain sizes in alloys containing La contents of more than 1.7 wt.% were small at 20μm,comparing with that in the master alloy.(2) For the present alloys containing La,the second phase particles,consisting of Zn and La,have the capacity of hydrogen storage.These particles were between 5 and 10μm in size,and were dispersed in the matrix bomogeneously.(3) Tensile properties were improved with increasing Cu or La content.For the alloys with Cu and La,the tensile strength was from 450 to 500 Mpa,and the elongation between 14 and 17%.(4) The alloys containing La had high resistance to SCC.Their SCC lives were about 15 times as long as that of the master alloy.In conclusion,the alloys added Cu more than 0.6 wt.% and La 4.0 wt.% were much superior to the master alloy in both the tensile properties and the SCC resistance.
続きを見る
|
||||
| 9.
論文 |
論文
|
津田, 政明 ; 広瀬, 幸雄 ; 矢島, 善次郎 ; 田中, 啓介
概要:
金沢大学大学院自然科学研究科<br />Stress corrosion tests were conducted on the notched compact tension specimens of quenchedtempered S
…
NCM 439 steel in three kinds of environmental solution : distilled water,3.5%NaCl, and 0.1N H_2SO_4 The crack nucleation behavior was analysed from a view point of fracture mechanics. The results obtained are summarized as follows. (1) Time to crack nucleation t_n of the notched specimens with various root notch radii was determined by a parameter of K_ρ/(ρ+ρ_0)^<1/2>, where K_ρ is the apparent stress intensity factor, ρ is the notch root radius and ρ_0 is the intrinsic notch root radius. The life got shorter as the hydrogen content became larger in the order of distilled water, 3.5%NaC1, and 0.1N H_2S0_4. (2) Stress corrosion cracks were formed from the notch on three different planes : the original notch plane and two inclined planes to the notch. The crack plane changed depending on environments, notch-root radrii and stress levels. Two inclined plarles of crack initiation from the notch agreed with the plane of the maximum shear stress.
続きを見る
|
||||
| 10.
論文 |
論文
|
矢島, 善次郎 ; 広瀬, 幸雄 ; 田中, 啓介 ; 小河, 弘
概要:
金沢大学大学院自然科学研究科<br />Fracture toughness tests were carried out with blunt notched compact tension specimens of a high-str
…
ength low alloy steel, JIS SNCM 8 (equivalent to AISI 4340), tempered at several temperatures. The stress intensity factor K_ρ at the initiation of crack extension detected by the DC potential method was related to the initial notch-tip radius ρ by K_ρ=K_0(1+ρ/ρ_0)^<1/2> where K_0 and ρ_0 are material constants. This was derived through the concept of the fictitious notch-tip radius proposed by Tanaka and Hirose. The values of material constants K_0 and ρ_0 took the lowest values for the material tempered at 300℃. The residual stress near the fracture surface measured by the X-ray diffraction technique was tension. The depth of the plastic zone ω_y was measured by the distribution of residual stress beneath the fracture surface. It was related to the stress intensity factor at crack initiation K_i by the following fracture mechanics equation : ω_y=α(K_i/σ_Y)^2 where σ_y is the yield stress and α is from 0.14 to 0.12. The values of residual stresses very close to the fracture surface tended to decrease with increasing K_i, and were found to be a single-valued function of the fracture strain at the notch-tip determined from K_0 and ρ_0 values based on the fictitious notch-tip radius concept.
続きを見る
|
