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Article type: Cover
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Published: July 31, 2000
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Article type: Appendix
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App1-
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Article type: Index
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Toc1-
Published: July 31, 2000
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Keisuke TANAKA, Toshimasa ITO, Yoshiaki AKINIWA, Takahiro ISHII, Yasuh ...
Article type: Article
Pages
1-2
Published: July 31, 2000
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The residual stress in TiN film was measured by the X-ray method. TiN film was deposited on steel substrate by ion beam mixing method and the thickness was 1μm. The residual stress in TiN film was equi-biaxial and the value was about -5.5GPa compression. When uniaxial tensile loading was applied to the substrate, the stress in the film was in the biaxial state of stress because of the mismatch of Poisson's ratio. The result agreed well with the prediction. When the measured stress in the film becomes tension, the stress stop increasing even though the applied strain keep increasing. This leveling of the stress was caused by cracking of the film.
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Lin GAO, Masahiko KATO, Keijiro NAKASA, Teruhito BANSHO, Hidetaka NISH ...
Article type: Article
Pages
3-4
Published: July 31, 2000
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In order to investigate the effect of oxidation on the delamination strength of 8mass%Y_2O_3-ZrO_2 thermal barrier coating deposited on Co-base superalloy with CoNiCrAlY bond coat layer, the specimens were heated in air at 1073K, 1273K and 1473K for 36∿3960ks. Al_2O_3 oxide and complex oxide layers were formed along the interface between the top-coat and the bond at layers, and the thickness of the oxide layers became large with increasing heating temperature and time. The tensile and the edge-indent tests showed that the delamination strength increased to a maximum and decreased with increace in Al_2O_3 layer thickness.
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[in Japanese], [in Japanese]
Article type: Article
Pages
5-6
Published: July 31, 2000
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Thin film coatings toward various types of materials have been used for protecting substrate surface from corrosion damages or adding a lot of functions to them. Till now the studies have been mainly conducted concerning mechanical and chemical properties of TiN thin film coating. However, nanometric defects and cracks were always existed in coated thin film from the initial stage. In actual environment, degradation was generated by corrosive solution intruded from the nanometric defect. Therefore, localized corrosion process toward pitting corrosion or crevice corrosion of coated thin film must be understood in relatively mild environment such as aqueous environment with Cl^- ion when degradation of thin film was examined. For this purpose, morphological changes of localized corrosions were necessary to be grasped through conducting sub-micrometer order observations of generated defects in thin film. Therefore in this study, crevice corrosion resistance of coated specimen was improved through conducting previous treatment of N^+ ion bombardment before TiN coating. Then, localized corrosion process in coated TiN thin film in 3%NaCl aqueous solution was investigated in detail using Atomic Force Microscope (AFM).
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M. OKAZAKI, H. MURAYAMA, Y. YAMAZAKI
Article type: Article
Pages
7-8
Published: July 31, 2000
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Thermal-mechanical fatigue failure of the Ni-base superalloy coated with CoNiCrAlY alloy was clarified, compared with that of the substrate alloy. The results are also compared with the isothermal low cycle fatigue lives. A life prediction method was also explored.
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Masahiko KATO, Keijiro NAKASA, Xu YAN, Ichishige UNOKI
Article type: Article
Pages
9-10
Published: July 31, 2000
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TiN films were deposited on pure titanium specimens by reactive RF magnetron sputtering and gas nitriding methods. Wear tests of the specimens were carried out by using pin-on-disk type testing machine. The results showed that the wear property was modified remarkably by both methods, but the effect disappeared after a large number of rotation cycles. Optical observation of wear scars during wear tests showed that the delamination of small part of the film occurred and the area became large with the increase in rotation cycles. The interfacial fracture toughness was obtained fracture mechanically, which indicated that the interfacial fracture toughness had close relationship with wear performance of film.
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Hiroyuki IWANAGA, Kohei MIYAZAWA
Article type: Article
Pages
11-12
Published: July 31, 2000
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This study was intened to develop the corrosion resistance of Ti-Ni shape memory alloy. As the first step, the passivation treatment which is recommended to be used for prevention of crevice corrosion in "Methode of pitting potential measurement for stainless steel" in JIS was adopted. Electrochemical behavior of Ti-Ni shape memory alloy were measured in 0.9% NaCl solution. The main results obtained are as follows. (i) The corrosion potential of passivation treated specimen showed a more noble potential of 0.07V (vs. S. C. E.) than the untreated specimen. (ii) Corrosion resistance of Ti-Ni shape memory alloy can be improved by forming the oxide film on surface from the results of pitting initiation potential.
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Takeshi OGAWA, Goro TOKIWA, Yoshifumi KOBAYASHI, Yoshio HARADA
Article type: Article
Pages
13-14
Published: July 31, 2000
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Rolling contact fatigue was investigated by sphere-plane contact fatigue machine developed in this study for WC-cermet sprayed materials prepared by HVOF. The fatigue strength strongly depended on the spraying conditions, i.e. three levels of gas pressures, due to the different fatigue mechanisms. When the gas pressure was high, the coating has higher hardness and contact fatigue strength. The contact fatigue strength was evaluated by measuring groove widths of contact region during the fatigue tests.
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Hiroyuki WAKI, Izuru NISHIKAWA, Keiji OGURA
Article type: Article
Pages
15-16
Published: July 31, 2000
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In order to investigate the effect of stress concentration on the fatigue strength of ceramics coated stainless steel, tension-compression fatigue tests of notched specimen were conducted at 893K and room temperature. U-shaped notch specimens made of type 304 stainless steel were coated with ZrO_2-8%Y_2O_3 by the plasma-spraying method. Stress concentration factor of substrate was selected as 2.1. The surface strain at notch root was measured by using the laser speckle strain/displacement gauge (SSDG) during fatigue test. The cracking in the ceramics layer was found to occur just after a first load cycle. However, this crack was not able to penetrate into the substrate. Therefore, the cracking in the ceramics layer was found not to be a cause of a decrease in fatigue life.
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Hideto SUZUKI, Kazutoshi KATAHIRA, Shinitsi NUMATA, Byungjun LEE, Masa ...
Article type: Article
Pages
17-18
Published: July 31, 2000
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"P-S-N Globe" is useful method in order to estimate fatigue reliability of surface modified materials. In this study, we propose the estimation system which is able to improve fatigue reliability of surface modified materials. And finally, the organized data, which is taken by the fatigue reliability estimation of surface modified materials, is shown.
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Shinichi NISHIDA, Nobusuke Hattori, Naozumi Morita
Article type: Article
Pages
19-20
Published: July 31, 2000
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In this study torsional fatigue test has been performed to investigate fatigue strength of notched specimen. There are two of notched specimen, i. e., type H is specimen with a drill hole, type P is specimen with a drill hole with chamfer by plastic deformation by press working. The main results obtained in this test are as follows; (1) The fatigue limit of type P is 1.6 times higher that of type H. (2) The work-hardening layer by plastic deformation suppress the crack growth rate at early stage. (3) The fatigue crack of type H initiates at edge of drill hole. On the other hands, that of type P initiates a little apart from the chamfer edge.
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Kiyotaka MASAKI, Yasuo OCHI, Takashi MATSUMURA
Article type: Article
Pages
21-22
Published: July 31, 2000
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Shot-peening treatment is very useful for the improvement of the fatigue strength. But the higher surface roughness induced by the hard shot-peening (HSP) treatment was negative factor of the fatigue strength. So, for the more improvement of the fatigue strength, it can be possible by improving the surface condition of the HSP treated material. In this paper, rotating bending fatigue tests on two type of specimens were carried out. One is the surface polished-HSP specimen and the another is the W-shot peened specimen. As the result of fatigue test, the surface roughness improving was effective for the improvment of fatigue strength on the HSP treated specimen. These fatigue properties were investigated by surface roughness profiles, residual stress distributions and hardness distributions.
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Shinzaburo TAKAFUJI, Yozo KATO
Article type: Article
Pages
23-24
Published: July 31, 2000
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The effect of shot peening on the fatigue strength in the long life range of (10)^7 to (10)^8 cycles were investigated in a β-titanium alloy (Ti-4Al-22V alloy). The specimens were solution treated at 750℃ and then aged at 500℃ (material STA). The fatigue strength for (10)^8 cycles of material STA was 580 MPa. The fatigue strength of the shot peened specimens was 680 MPa. The increment of the fatigue strength was 100 MPa (17%) by shot peening. The strengthening effect originated by cold working prior to the aging was not identified.
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Haeng Nam KO, Chuji KAGAYA, Hisatake ITOGA, Tatsuya HASEGAWA
Article type: Article
Pages
25-26
Published: July 31, 2000
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The cantilever-type rotary bending test was performed at room temperature on high carbon chromium steel, preparing three kinds of specimens, fine particle bombarded, shot peened and untreated. Each specimen had a transition stress from surface fracture initiation to interior. The transition stress was higher for FPB specimen than for SP specimen, and the effect of surface treatment appeared at stress level more than the transition stress of untreated specimen. This effect seemed to disappear at lower stress level, although the features of fish-eye were different.
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Daisuke YONEKURA, Junji NODA, Jun KOMOTORI, Masao SHIMIZU, Yoshio MIYA ...
Article type: Article
Pages
27-28
Published: July 31, 2000
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Rotational bending fatigue tests were carried out using SCM420H steel with special focus on the effects of Wide Peening Cleaning (WPC) treatment on fatigue properties. Measurements of residual stress and hardness in surface layer were also performed. It was found that WPC process has a beneficial effect on increasing the fatigue strength. This is because WPC process generates the hardened surface layer with high compressive residual stress.
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Chuji KAGAYA, Koji OGASAWARA, Yasuhiro KATAOKA, Masanori KATO, Yoshio ...
Article type: Article
Pages
29-30
Published: July 31, 2000
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In order to make clear the effects of fine particle bombarding on the fatigue strength behaviors of vacuum carburized SCM415,rotating bending fatigue tests were carried out in air at room temperature, using both smooth and notched specimens. Furthermore, the micro structure, the residual stress, and the fracture surface of specimens were also investigated. Based on the above results, the improvement of fatigue properties was discussed by comparing them with both fine particle bombarded specimen and as carburized specimen.
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Yosio Miyasaka, Hirohide Kubota
Article type: Article
Pages
31-32
Published: July 31, 2000
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The purpose of this study is to examine the effects of the material, machining accuracy, heat treatment and surface modification of gears on the tooth surface strength. Namely, the effect of soft resistance under operating condition, abnormal surface layer produced by gas carburizing and micro dimples formed by fine particle peening were investigated. Based on these results, the improvement of tooth surface strength was discussed.
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Katsuki KAMIYA, Noboru EGAMI, Hiroaki TAKESHITA
Article type: Article
Pages
33-34
Published: July 31, 2000
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In order to study on surface modification of SCM415 steel by carbonitriding and fine particle peening. The characteristics of fatigue crack propagation were investigated for three-point bending tests. Fine particle peening was used two different shot sizes of 50 and 100μm. The three-point bending fatigue tests were conducted at 20Hz and two stress ratios R=0.1 and 0.3. It was found that the fatigue strength of fine particle peening materials yielded high compressive residual stress was improved, and also showed extreme delay of the crack propagation in the carburized case. And crack propagation rate was correlated with stress intensity factor range ⊿K and effective stress intensity factor range ⊿K_<eff>.
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Kenichi ITO, Hayato MAEDA, Noboru EGAMI
Article type: Article
Pages
35-36
Published: July 31, 2000
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This study examines numerical analysis of particle velocity and temperature distribution of struck material surface in fine particle peening. When the particle is accelerated using a direct-pressure type, the velocity of a 50μm particle, just before striking the metal surface, was calculated to be 222m/s. In applying air pressure, the acceleration of fine particles show significant increase compared to larger sizes. Moreover, the experimental values agree well with the calculated ones. On the other hand, the temperature distributions show the maximum surface temperature to be 1500K and cools instantly.
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K. SHIOZAWA, K. MITSUTANI, H. MOJIMA
Article type: Article
Pages
37-38
Published: July 31, 2000
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In order to investigate the effect of surface treatment on fatigue strength of a hard steel, cantilever-type rotating-bending fatigue test in air was conducted using the smooth specimens of alloy tool steel, SKD61,with four kinds of surface treatment; that is, TiN coating by PVD method, plasma assisted ion-nitriding, duplex treatment with the ion-nitriding followed by the TiN coating and gas-nitriding. Fatigue fracture of nitriding specimens was occurred at non-metallic inclusion inside of the specimen with fish-eye. No difference in S-N curve among the surface treated specimens was observed in the region of long fatigue lives, in spite of the difference in distribution of residual stress and hardness.
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Ryuta SUGIYAMA, Kohichi SUGIMOTO, Hiroroh NOMURA, Hitoshi KABASAWA, Hi ...
Article type: Article
Pages
39-40
Published: July 31, 2000
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Microstructure and mechanical properties in hardened layers of SUS 304 steel gas-sulphonitrided in NH_3,N_2,H_2S and C_2H_2 gaseous atmosphere were investigated and these characteristics were compared with those of SUS304 steel gas-sulphonitrided with CO_2 gas. Addition of C_2H_2 gas in carrier gas increased the depth of hardened layer with the decreased thickness of compound layer, in comparison with CO_2 gas addition. An increase in volume fraction of (Fe, Cr)_<2-3>N was found in superficial sulphide layer and compound layer, resulting from enrichment of chromium and nitrogen. Excellent mechanical properties such as increased hardness and crack initiation resistance were also completed by C_2H_2 gas addition, although Young's modulus was reduced by 20% and dynamic friction coefficient was increased somewhat.
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Tatsuro MORITA, Syunsuke FUCHIKAWA, Jun KOMOTORI, Masao SHIMIZU, Kunin ...
Article type: Article
Pages
41-42
Published: July 31, 2000
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This study is conducted to clarify the relationship between the fatigue strength of nitrided titanium and that of the substrate. The result shows that the fatigue strength of nitrided pure titanium is improved by the increase in the fatigue strength of its substrate. This improvement is caused by the reduction of the magnitude of the stress field which is generated in the compound-layer by the slip of the substrate. However, the above improvement is limited in case of nitrided titanium alloys which have a high strength such as Ti-6Al-4V and SP-700 alloys. That is because the compound-layer is subjected to the additional intensive tensile stress induced by the difference of Young's moduli between the layer and the substrate.
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Yoshitaka Misaka, Hisaki Koga, Hajime Nitta, Shigeo Hattori
Article type: Article
Pages
43-44
Published: July 31, 2000
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Since pin portion such as crankshaft is required wear resistance, generally that is locally induction hardened. However, it is pointed out that tensile residual stress in hardened boundary would be affecting to initiation of fatigue crack and fracture. In this study, influence of induction hardening conditions on tensile residual stress distribution in hardened boundary have been discussed. As a result, it is considered that tensile residual stress takes place by heat stress and is influenced by internal material temperature (material strength) during cooling.
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Yutaka KUREBAYASHI, Yasushi MATSUMURA, Sadayuki NAKAMURA
Article type: Article
Pages
45-46
Published: July 31, 2000
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The effect of induction-hardened depth on torsion fatigue strength of several types of notched specimens were investigated. The results are as follow 1) Induction-hardened specimens show the best torsion fatigue strength when the effective case depth/radius ratio is about 0.5. 2) In the case of shallow case depth, the fatigue cracks initiate at the hardened/non-hardened boundary. On the other hand, the fracture of deeply hardened specimens originates at the surface layer.
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Masahiro OKUMIYA, Yoshiki TSUNEKAWA, Toru HAMADA, Kazuhiro KURAHASHI, ...
Article type: Article
Pages
47-48
Published: July 31, 2000
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In this study, natural gas was used as raw material and enriched gas of carrier gas, and the development of the system which shortened the carburization time was examined. The mechanical property of the sample which is treated by using this method was evaluated. The control of carbon potential by the oxygen concentration is possible, if enriched gas flow rate in which soot does not arise is chosen, even if the natural gas is used for enriched gas. And, the responsibility is better than carbon potential control by the carbon dioxide concentration. Using the difference between carbon potential calculated from carbon dioxide concentration and and it calculated from oxygen concentration, the system which foresaw the soot generation was developed. By controlling the carbon potential using this system and oxygen sensor, the carburization time was shortened, and retained methane quantity and using enriched gas quantity are drastically decreased.
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Yukitaka MURAKAMI, Hiroshi NATSUME
Article type: Article
Pages
49-50
Published: July 31, 2000
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The point where the front of a 3-D crack intersects a free surface is called "corner point". The ordinary crack tip stress singularity of r^λ with λ=-0.5 has been well known in fracture mechanics. However, with regard to the stress singularity at the corner point there are several theories which have not been clearly accepted. This paper is concerned with the detailed analysis of the stress singularity at the corner point for a through crack and a semi-circular crack under Mode II loading. According to the theories by Benthem and others, not only K_<II> but also K_<III> has a non-zero value at a corner point which, however, contradicts the stress free boundary condition of free surface. The FEM analysis of the present study based on the careful meshing and accurate determination of singularity (λ) has revealed that although the value of K_<III> increases as the crack front approaches the comer point, the domain of non-zero value of K_<III> decreases infinitesimally and accordingly the influence of K_<III> can be ignored at the corner point. Similarly, the domain of the singular stress field with λ≐̸-0.5 and λ=-0.6∿-0.5 also decreases as the crack front approaches the corner point.
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NaoAki NODA, Yasushi TAKASE, Zhiqiang SUN, Qing WANG
Article type: Article
Pages
51-52
Published: July 31, 2000
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In this study, generalized stress intensity factors K_<I, λ1>, K_<II, λ2> and K_<III, λ4> are calculated for a V-shaped notched round bar under bending or torsion using the singular integral equation of the body force method. The body force method is used to formulate the problem as a system of singular integral equation, where the unknown functions are the densities of body forces distributed in an infinite body. Then, generalized stress intensity factors at the notch tip are systematically calculated for various shapes of V-shaped notches. The accuracy of Benthem-Koiter's formula proposed for a circumferential crack is also examined through the comparison with the present analysis.
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Kenji MACHIDA, Kei ITOH, Kenichi SHIROTA
Article type: Article
Pages
53-54
Published: July 31, 2000
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An interface delamination in IC Packages is a critical issue in both structural design and material selection of plastic IC packages. The 3-D finite element analyses were carried out to examine the stress-intensity factor of delamination interface in IC packages subjected to steady and non-steady thermal stresses. The stress-intensity factor K associated with a thermal interface crack was evaluated by the modified crack closure integral. The conditions of thermal stress, which were steady and non-steady thermal stresses, were compared. Especially, it is considered that K_<III> could not be neglected at the corner part in IC Packages. Therefore, the 3-D finite element analysis is indispensable to the estimation of the stress-intensity factors at the corner part in IC packages.
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Keisuke TANAKA, Yoshiaki AKINIWA, Hirohisa KIMACHI, Huchen YU
Article type: Article
Pages
55-56
Published: July 31, 2000
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Elastic-plastic stress analysis of a circumferential crack in round steel bars under mode I, mode III and mixed mode (I+III) loadings was conducted by the finite element method. The J-integral was found to be the most appropriate fracture mechanics parameter for characterizing the fatigue crack propagation behavior of mode I, mode III and mixed mode (I+III) cracks. In this paper, two methods were used for the estimation of J-integral value of mixed mode (I+III). The one is the simple estimation method, and the other method is the energy method. The J-integral value under the mixed mode (I+III) obtained by the simple method was in good agreement with that estimated from the energy method in the range of applied displacement u≤0.035mm and applied twist angle θ≤0.014rad.
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Akira UENO, Hidehiro KISHIMOTO, Kohji ISOBE
Article type: Article
Pages
57-58
Published: July 31, 2000
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In this study, crack propagation behavior on glass have been studied by using the newly developed in-situ type bi-axial bending machine. The major results of this study are summarized as follows : (1) The threshold stress intensity under mixed mode tends to decrease with increase in the stress mixing ratio R. (2) The criteria in which the crack began to grow under mixed mode condition were proposed.
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Toshihisa NISHIOKA, Takehiro FUJIMOTO, Masanori HASHIMOTO, Hiroki NISH ...
Article type: Article
Pages
59-60
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this study, the difference of static and dynamic fracture behavior is discussed to clarify the characteristic of dynamic fracture under mixed-mode load. The automatic moving finite element method with Delaunay triangulation is developed to archive numerical prediction for fracture path of three-point bending specimen. The fracture path of curving crack is predicted by using the maximum hoop stress (σ_<θθ> maximum) criterion and the local symmetry criterion (K_<II>=0 criterion). The numerical results of the fracture path prediction simulations agree with the results of experiment. The predicted paths of static fracture considerably differs from that dynamic fracture under impact load. In the case of static load the fracture paths are not much influenced by the loading eccentricity.
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Toshihisa NISHIOKA, Takehiro FUJIMOTO, Jianliang YAO, Takuma NOZAKI, K ...
Article type: Article
Pages
61-62
Published: July 31, 2000
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In this study, the interfacial crack kinking behavior of bimaterial specimens are investigated. The bimaterial specimen consist of epoxy and aluminum. To produce various mixed-mode states, the loading angle is changed systematically from 0° to 180°. The fracture mechanics parameters for interfacial crack in bimaterial specimens are evaluated by the aid of finite element analyses. All kinked fractures occurred at loading angle ≧120°. Fractures energy supply for interfacial crack is discussed by the measurements of separated J integral. The component separation method is used to estimate stress intensity factor for interfacial crack. In this paper, the stress intensity factors at the characteristic length 1=2a are calculated.
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Toshihisa NISHIOKA, Takehiro FUJIMOTO, Akiomi KAWANO, Stanislav TCHOUI ...
Article type: Article
Pages
63-64
Published: July 31, 2000
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In actual fracture phenomena, branched cracks were often observed. The numerical simulation technique of dynamic crack bifurcation has not been established enough due to some numerical difficulties. The development of this simulation technique is very important to clarify the crack bifurcation mechanism. The authors have previously developed the moving finite element method with Delaunay triangulation for crack bifurcation analyses. In this study, the numerical path prediction is tried by using the moving FEM. For bifurcated cracks, crack propagation paths are predicted according to the maximum hoop stress. The results of numerical prediction agree with the experimental results and the results of generation phase simulation. In these simulations, the fracture mechanics parameters were accurately calculated by special form of the dynamic J integral.
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Hiroshi TANAKA, Keisuke TANAKA, Tohru SHIOTSUKI, Takuji MATSUNO
Article type: Article
Pages
65-66
Published: July 31, 2000
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The propagation behavior of mode I, mode II and mixed-mode I+II interlaminar cracks at 0°/0°, +30°/-30°, +45°/-45° and +60°/-60° interfaces in graphite/toughened epoxy laminates, IM600/#133,was studied under static loadings. The mixed-mode bending (MMB) method was used for mixed-mode I+II tests. The interlaminar fracture toughness increased with crack extension due to significant fiber bridging and transverse cracking but remained constant for 0°/0° interlaminar cracks subjected to mode I dominated loading. The effects of the mixed-mode ratio and fiber orientation on interlaminar fracture toughness at crack initiation were discussed.
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Mariko YAMASAKI, Yasutoshi SASAKI
Article type: Article
Pages
67-68
Published: July 31, 2000
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Yield behavior of wood (Japanese beech : Fagus crenata B1. and Japanese cypress : Chamaecyparis obtusa ENDLICHER) under a combined static axial-shear stresses was examined. The specimen had a rectangular cross section with one of its major axis lying in the fiber (longitudinal) direction. The axial force was applied in the fiber direction (along L) and torque was applied about an axis lying in the same direction as L. Combined loading test was performed according to the proportional deformation loading method. The obtained results were summarized as follows : 1) The determinations of yield points were more influenced by torsion than axial force. 2) The stress-strain relationships of Japanese cypress showed more elastic than those of Japanese beech. 3) The yield loci seemed not to be influenced by the difference between LT and LR planes, and could be expressed by the past yield criteria, like Hill type. 4) It is suggested that the equivalent stress-equivalent strain relation could be used at the determination of yield point.
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Yasutoshi SASAKI, Mariko YAMASAKI
Article type: Article
Pages
69-70
Published: July 31, 2000
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Fatigue behavior and stress-strain properties of wood under a cyclic tension-torsion combined loading were investigated experimentally. Materials used for the experiments were rectangular bars of Japanese cypress (Chamaecyparis obtusa Endl.). Tension and torsion loading were applied along and around the longitudinal axis of the specimen coincided with the longitudinal direction of the wood, respectively. The obtained results were summarized as follows : 1) All data were found to locate in a slightly wide band on the S-N plot in spite of different biaxial combined stress ratios, but the slope of the S-N curves became low in which tensile stress was dominant. 2) Failure modes of the test specimen depended on which tensile or shear stress was dominant in the biaxial stress ratios. 3) Hill's criterion for the static strength showed in better agreement to evaluate the fatigue strength under biaxial combined stress ratios. 4) The longitudinal and transverse elasticity kept the initial states and decayed suddenly just before fatigue failure. However their tendencies owed to the biaxail combined stress ratios and the applied stress levels.
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Yoshihiro FUKUSHIMA, Yukitaka MURAKAMI
Article type: Article
Pages
71-72
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Ryohei MIYOSHI, Yasunobu FUKUDA, Yoshiyuki KOBAYASHI, Yoshihito KUROSH ...
Article type: Article
Pages
73-74
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Kiyotsugu OHJI, Tetsuya TSUJIKAMI, Tomoyuki FUJITA
Article type: Article
Pages
75-76
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In a previous paper, the authors proposed a method of simulating the behavior of a fatigue crack propagating in bonded dissimilar materials by using an equivalent specimen made of single constituent material, and proved in successful with bonded copper-steel (Young's Modulus Ratio : 1.7) plates. This paper is concerned with experimental simulation studies of fatigue crack propagation paths near or across the bonded interface with bonded titanium-copper (YMR : 1.2) and titanium-steel (YMR : 2.0) plates, by using this proposed equivalent specimens. Single-edge-cracked equivalent plate specimens with a 15° or 45° slant interface were used, which was simulated by thickness discontinuity. When a crack propagated from the low to the high Young's modulus side, the crack grew along the interface except for the case of titanium-copper with 45° slant interface. When the initial crack was in the high Young's modulus side, the crack propagated almost straight across the interface, if the interface had enough strength, These behavior agreed quite well with those obtained by BEM numerical simulations of fatigue crack propagation based on the Δσ_θ maximum criterion, which were conducted in a separate paper.
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M. Okazaki, K. Tuchiya, Y. Harada
Article type: Article
Pages
77-78
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Interfacial fatigue crack propagation along the Mar-M247 Ni-based superalloy/CoNiCrAlY alloy coating film was studied at 873 K, and the effect of loading mode was discussed. At first the crack propagation resistance was clarified under Mode I loading, influenced by the substrate surface roughness. Next, efforts was made to understand the naturally initiated interfacial small crack propagation behavior under the Mode II dominant loading condition, in which the cyclic axial load was applied parallel to the interface. The interfacial crack was found to reveal a noteworthy behavior the growth rate proportionally increased with the interfacial crack length just after the crack initiation, then decreased and finally arrested.
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Keisuke TANAKA, Yoshiaki AKINIWA, Teruaki MIKURIYA, Koichi TANAKA
Article type: Article
Pages
79-80
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Tests of fatigue crack propagation from pre-crack under mixed mode loading were performed on S45C thin-walled tubular specimens. For a circumference through crack in thin-walled tubuler specimen, tension and tortion loadings correspond to mode I and mode II loads, respectively. Test results with cyclic torsion and static tension were compered to test results only with cyclic torsion. Crack propagation behavior, threshold condition, and the cruck propagation direction were discussed.
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Masanori KIKUCHI, Tomonori SATAKE
Article type: Article
Pages
81-82
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this study, the mixed II+III mode fatigue test is conducted using a single-axis testing machine. The test specimen is a four-point-shear specimen with a side crack. After the test, the fracture surface is observed using SEM (Scanning Electron Microscope) and the characteristic feature of the mixed mode fatigue surface is obtained. The three-dimensional FEM (Finite Element Method) analysis is conducted and KII and KII are evaluated. For mode II+III fatigue test, the mode I static load is give to avoid the contact of crack surfaces. By the SEM observation, it is found that the contact does not occur during the fatigue test. The fatigue crack grows faster at the surface of the specimen than that of inside of the specimen. The crack growth direction is straight along the original crack direction, which is different from the predicted direction by Erdogan-Sihcriterion. The fracture surface shows a characteristic feature of shear fatigue crack, on which many thin laminas are piled up along the normal direction to the crack front. It agrees with what proposed by Otsuka et al.
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Tomohei KOBAYASHI, Kanta NIHEI, Hideo ONO, Shigeki KOUE
Article type: Article
Pages
83-84
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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It is wellknown fact that metal fatigue crack propagates normal to the direction of maximum principal stress under the multi-axial stress condition. But the fatigue crack growth direction is not clear when the near-cracktip principal stress directions of the repeated component is different from that of the constant component. Axial-shear fatigue crack growth tests with mild steel pipe specimens have been carried out to measure the direction of fatigue crack growths. As a result, it is found that the fatigue crack growth direction is influenced by the repeated component of the stress intensity factor.
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Go MATSUBARA, Hiroyasu NISHIKAWA
Article type: Article
Pages
85-86
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Properties of fatigue growth from circular delamination between a unidirectional and a cloth laminates in a GFRP was investigated. The fatigue growth tests were carried out at stress ratios : R=0.1 and -1. The results were as follows. (1) At the stress ratio : R=0.1,the pure mode II fatigue crack growth behavior from circular delamination was different in the crack growth direction. (2) At the same stress ratio, the pure mode II and the pure mode III fatigue crack growth behavior from circular delamination were almost equivalent. However, at R=0.1,it is necessary to take the average of the pure mode II crack growth rate to the bidirection.
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Shouetsu ITOU
Article type: Article
Pages
87-88
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Stresses around a propagating finite crack having a constant velocity in an elastic layer sandwiched between two elastic half-planes are determined. The self-equilibrated system of pressure is applied to the crack surfaces. Application of the Fourier transform technique reduces the problem to that of solving dual integral equations. In order to solve the equations, the differences of the crack surface displacements are expanded in a series of functions that are equal to zero outside of the crack. The unknown coefficients in the series are solved using the Schmidt method. The stress intensity factors are calculated numerically for a crack in a layer made of epoxy resin sandwiched between two half-planes made of aluminum.
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Qing Wang, NaoAki NODA, Masaaki HONDA, Mengcheng CHEN
Article type: Article
Pages
89-90
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this paper a singular integral equation method is applied to calculate the distribution of stress intensity factor along the crack front of a 3 D rectangular crack. The stress field induced by body force doublet in an infinite body is used as the fundamental solution. Then, the problem is formulated as an integral equation with a singularity of the form of r^-3. In solving the integral equation, the unknown functions of body force densities are approximated by the product of a polynomial and a fundamental density function, which expresses stress singularity along the crack front in an infinite body. The calculation shows that the present method gives the smooth variation of stress intensity factors along the crack front for various aspect ratio, The present method gives rapidly converging numerical results and highly satisfied boundary conditions throughout the crack boundary.
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Akihide SAIMOTO, Yasufumi IMAI, Fumitaka MOTOMURA
Article type: Article
Pages
91-92
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The applicability of thermal stress cleaving (TSC) for relatively thich brittle material is studied. The crack opening is observed for two different shapes of initial cracks, namely the semi-circular surface crack and through-thickness crack, under the mode I thermal loading condition induced by a point or a line heater applied to the surface of specimen. Numerical results modeling the TSC for 3D solid showed the good correspondences with experimental observations.
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Masayuki ISHIHARA, Naotake NODA
Article type: Article
Pages
93-94
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this study, we treat analytically a two-dimensional electroelastic problem of an infinite piezoelectric body with two circular piezoelectric inhomogeneities one of which contains a crack. We consider that the body is subjected to anti-plane shear load and in-plane electric load at infinity. The problem is solved based on Bueckner's principle and is finally reduced to a problem of a singular integral equation of the first kind with respect to the distribution function of screw dislocation. Stress intensity factor is formulated. Some numerical results are shown to investigate the influence of micromechanics parameters on electroelastic field and stress intensity factor.
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