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Yoshiaki AKINIWA, Keisuke TANAKA, Tomoyuki FUJII
Article type: Article
Pages
195-196
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Simulation method for analyzing the fracture behavior of brittle materials was developed on the basis of the initiation of micro-cracks. Deformation and fracture behavior of porous ceramics containing initial cracks were numerically simulated. The mean stress model was adopted as the condition of the initiation of micro-cracks. The micro-cracks were located in a regular manner as the bonds of a square lattice. The critical strength of the bond was given as random variables. When the initial crack length was small, the calculated relationship between the applied strain and the stress became linear. Variance of the critical strength of micro-crack initiation had significant effect to the linearity. The fracture strength decreased with increasing the size of the initial crack. The size of the non-damaging defects could be evaluated by the proposed method. The resistance curve calculated was independent of the initial crack length. As the variance of the critical strength increased, the increasing rate of the resistance curve became large.
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Toshimitsu Yokobori, Daisuke Kobayashi, Akio Fuji
Article type: Article
Pages
197-198
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Precipitated hardening advanced heat resistant materials such as Ni-base super alloys have been developed so that a creep crack grows in a branched manner due to the strengthening effect of the second phase of material structure. In this paper, using IN100 alloys with γ' strengthening structure, in-situ observational creep tests were conducted to observe branched crack growth behaviors. On the basis of this phenomenon, a mechanical model of a branched crack was constructed and FEM analysis on the creep crack growth was conducted by the method of releasing nodal points. This result showed the mechanical effect of a branched crack on the creep crack growth curve.
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Seiichi OHTAKI, Shin KOBAYASHI, Nobuhoko TATSUMOTO
Article type: Article
Pages
199-200
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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High performance of personal computers enables to conduct complicated numerical simulations in a short time. The finite element method is one of the most effective tools especially for the numerical analysis of the elastic-plastic problem. Whereas, the photoelastic coating method is the experimental way to study the elastic-plastic behaviors of metals. In this study, authors investigate the elastic-plastic simulation of cross-shaped specimens with a central hole using the finite element software LUSAS. The results are compared with the experimental ones in the cases of the perforated plates subjected to uni-axial tension.
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Tsutomu EZUMI, Shintaro MATSUSHIMA
Article type: Article
Pages
201-202
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In general, the contact side product is extremely narrow though the contact of the object has the contact side product of limited by the transformation. It is assumed that these cause the surface damage by straightening, and generating extremely high contact pressure power in the vicinity of contact side. A static load is loaded to the disc where a part of crack exists, and then, the stress field in the point of contact neighborhood is analyzed, and examined experimentally in this research. Concretely, how parameters of the contact side obtained by the formula of the stress intensity factor obtained from an experimental analysis by a photodynamic technique and the hertz and the contact pressure, etc. exert the influence is considered to the crack parameter of the disk. A static load loaded by the lever equation loading device, and the specimen experimented by installing in the specimen fixation mount of making by oneself.
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Tetsuo NOGUCHI, Tsutomu EZUMI
Article type: Article
Pages
203-204
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Recently, the influence of the intervention thing by the intervention thing in the structure causes a trouble. Waste lumber was discovered in Hanshin-Awaji big earthquake disaster inside the ferroconcrete leg pillar of the expressway high bridge, and it caused a trouble. The one due at the work that it was mixed in the concrete at the Shinkansen tunnel became a cause, and a concrete lump fell. A report by the experiment is hardly seen though a report by the calculation is seen about the influence by the intervention thing. Nevertheless, it is this research. An influence by tensile load in the elliptic inclusion thing is examined about the object which contains inquiry, an intervention thing. This research can be applied to repression of multiplication of the cancer cell more, and it can think that the convalescence of the cancer patient can be improved.
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Haruo ENDOH, Yoichiro HIWATASHI, Tsutomu HOSHIMIYA
Article type: Article
Pages
205-206
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In this study, the imaging of simulated subsurface defect using a photoacoustic (PA) microscope has been demonstrated. Two types of subsurface defects were fabricated in an aluminum plate specimen mechanically. The first subsurface defect has a cylindrical shape with length and diameter d of 2.0mm and 0.4mm, respectively and aligned parallel to the sample surface. The second subsurface defect had concave top shape, with lateral length of 6.0mm and aligned parallel to the specimen surface. The obtained PA image clearly showed the location and the size of both subsurface defects. The estimated specimen shape obtained from PA signal intensity distribution showed good agreement with the embedded actual specimen shape.
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Yoichiro HIWATASHI, Haruo ENDOH, Tsutomu HOSHIMIYA
Article type: Article
Pages
207-208
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In this paper, nondestructive imaging and observation of pitting corrosions on pure aluminum plate, that were generated in sodium halides alcoholic aqueous solution by photoacoustic microscope (PAM) has been investigated. Immersion tests of a pure aluminum plates were conducted in these solutions for 144 hours. Nondestructive measurement of real pitting corrosions was carried out using PAM. The amplitude and phase of the photoacoustic (PA) signal were measured at every point of the scan, and PA amplitude images were obtained. The PA amplitude signal intensity varied with both the shape and depth of the pitting corrosion.
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Juhachi ODA, Takefumi SUZUKI, Kenichi SAKANO
Article type: Article
Pages
209-210
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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When a static load is applied to a brittle material beam, the beam fractures at the fixed end. However, such a phenomenon does not necessarily happen in the case of dynamic load. In dynamic load the fracture behavior changes with the situation of the stress wave propagation, the material properties and the shape of beam. In this research, an impact fracture behavior of brittle material beam is analyzed using the discrete element method (DEM), and the results are compared with the experiment values. From the results, the impact fracture mechanism of brittle material beam is considered.
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Satoru TAKAHASHI, Masayuki YOSHIBA, Masaharu NAKAMORI
Article type: Article
Pages
211-212
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In situ observation of the mechanical failure behavior was conducted of different kinds of the plasma sprayed thermal barrier coating (TBC) systems by means of an optical microscopy under the static loadings at ambient temperature; as the most fundamental aspect, in order to clarify the failure mechanism of TBCs. Several kinds of TBC systems were prepared by using different coating parameters of ether water plasma spraying or air plasma spraying process for top-coat, heat treatment condition and so forth. Mechanical tensile or compressive loadings were applied progressively to the TBC specimen in the four-point bending test methodology. The influence of TBC microstructure on the crack initiation and propagation behavior was investigated in detail. Furthermore, the TBC failure was quantitatively evaluated in relation with the mechanical strain applied on the top-coat surface.
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Hideaki KANEKO, Taiji TORIGOE, Koji TAKAHASHI
Article type: Article
Pages
213-214
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Advanced cooling scheme and Thermal Barrier Coating (TBC) have been applied to industrial gas turbine hot parts as turbine inlet temperature increasing. TBC is effective method for preventing base metal temperature over heating as well as increasing thermal efficiency of plant by cooling air flow reducing. Good coating quality and high durability in long term operation service of power plant are important to obtain high reliability of TBC. In this study, coating quality evaluation method and durability test method of TBC were examined. As a results, it was confirmed that static bending test and Laser thermal cycling test were useful methods
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Akira YOSHIDA, Takashi WATANABE, Toshiyuki HASHIDA
Article type: Article
Pages
215-216
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The fracture process in thermal barrier coatings (TBCs) was investigated by conducting furnace heating tests. The uniform heating tests were conducted using TBC specimens with a top coat (YSZ) and bond coat (NiCrAlY), and the fracture process was examined by monitoring AE events. Two types of TBCs with different roughness of the bond coat surface were tested to examine the effect of the interface property on the fracture process. SEM observation in conjunction with the AE activity revealed that a number of distributed microcracks were observed to initiate along the vicinity of the top coat/bond coat interface only at the cooling stage of heating test. The coalescence of those discontinous microcracks resulted in the delamination and eventual spallation of the top coat due to buckling deformation when the TBC was further cooled down. The AE results were used to obtain the temperature condition at which the significant delamination took place in the TBCs and to determine the temperature drop ΔT_i from the maximum heating temperature T_<max>. It was shown that ΔT_i was approximately constant irrespective of T_<max>, suggesting the importance of the thermal shrinkage after T_<max> for the delamination growth.
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Tohru HISAMATSU, Akito NITTA, Taiji TORIGOE, Tsuneji KAMEDA, Hideyuki ...
Article type: Article
Pages
217-218
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Thermal barrier coatings (TBC) for a 1700℃-class advanced closed-cycle gas turbine system are studied, aiming at the surface temperature of higher than 1300℃ and the allowable temperature-difference of higher than 350℃. As a result of the studies, it is showed that following processes are effective to improve the durability of TBC, i ) increasing the purity of raw powder for top-coat, ii ) using ZrO_2-Er_2O_3 as top-coat material, iii ) shaping top-coat in columnar structure by EB-PVD.
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Masato NAKAYAMA, Tooru HISAMATSU, Taiji TORIGOE, Tsuneji KAMEDA, Hidey ...
Article type: Article
Pages
219-220
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A high heat flux thermal testing apparatus using plasma was manufactured in order to evaluate the TBC's environmental resistance. The testing apparatus is able to control the composition of plasma gas. High heat thermal cyclic tests using air plasma with/without H_2O(g) were implemented for four kinds of the developed TBC (top coating; high purity YSZ(APS), ErSZ(APS), ScSZ(EB-PVD), La_2Zr_2O_7(APS)). Results of the thermal cyclic test have revealed that; (1) In the case of the top coating which has characteristics of low sintering resistance, temperature on the surface of the substrate was increased as cycled. (2) The presence of H_2O(g) influences the degradation and damage such as sintering behavior of the top coating and oxidation of the interface of the top coating/bond coating.
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Hiroyuki WAKI, Keiji OGURA, Izuru NISHIKAWA, Noritaka YAMAMOTO
Article type: Article
Pages
221-222
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Fatigue tests were conducted at both 893K and room temperature for Thermal Barrier Coated (TBC) type 304 stainless steel. Surface strain during the fatigue test was monitored to examine the delamination of a subsurface layer using a laser speckle strain gauge. The strength of an APS-bond-coating was so low that multiple cracks occurred, while the strength of a LPPS-bond-coating was so high that a single crack occurred. In case of the specimen with a low strength APS-bond-coating, the fatigue fracture life of an Al_2O_3-sprayed specimen which bond-coating was delaminated was longer than that of a ZrO_2-8Y_2O_3-sprayed specimen which bond-coating was not delaminated. The reason was that the crack initiated at a bond-coating penetrated into a substrate for a non-delaminated specimen. In case of the specimen with a high strength LPPS-bond-coating, the fatigue fracture life of a specimen with a high adhesive strength thermal-aged-bond-coating was longer than that with a non-thermal-aged-bond-coating and the fatigue lives of these specimens were longer than those with APS-bond-coatings. The improvement of the fatigue fracture life was caused by the restriction of a crack initiation into the substrate due to the LPPS-bond-coating with a relatively higher strength. It was concluded that a bond-coating with high strength and high adhesive strength was effective on the improvement of fatigue fracture lives of plasma sprayed materials.
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Masatoshi TANNO, Toshiki KATO, Kazuhiro OGAWA, Tetsuo SHOJI
Article type: Article
Pages
223-224
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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It is well known, that thermally grown oxide (TGO) is formed at an interface of thermal barrier top coating (TBC) and bond coating during service. In the previous work, TGO layer contained at least two layers with different oxides was observed by SEM images. One was Al_2O_3,and the other was mixed oxide of NiO, CoO, Cr_2O_3,or their spinels. It was supposed that a reason of the macro-crack formation near an interface is due to decrease in bond strength or due to formation of stress concentration site caused by a formation of pores in the mixed oxide. In order for an improvement of bond strength, a modified bond coating material was developed which was MCrAlY with Ce and Si addition. Four point bending tests were carried out to measure a bond strength on conventional TBC and modified TBC with modified bond coating. As a result, the TBC with modified bond coating had superior bond strength than conventional one. It is likely that the reason can be a decrease of mixed oxide formation.
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Takamasa ONOKI, Tetsuro TONOMORI, Kazuhiro OGAWA, Toshiyuki HASHIDA, T ...
Article type: Article
Pages
225-226
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Knowledge of the degradation mode in thermal barrier coatings (TBCs) is a prerequisite for the prediction of their remaining life of gas turbine blades. This paper describes the effects of thermal aging on the microstructure in a YSZ-based thermal barrier coating system deposited on Ni based superalloy substrates. The heat treatment of the TBC specimens were conducted at 1373K for 100h, 500h and 1000h in air for thermal aging. The thermally aged coating system had thermally grown oxide (TGO) layer between the substrate and the TBC. TGO consisted of not only alumina but also other oxides. This oxide layer that named mixed oxides (MO) is composed of Ni, Co, Cr and O. 4 point bending tests were carried out in order to evaluate the TBC/substrate interface strength. The interface strength depended on the period of thermal aging in both type of tests. The interface strength increased initially up to the aging time of 100h, and then decreased drastically for the longer aging time. In 4 point bending tests, crack propagated along the interface between TBC and substrate. These results suggested that the interface strength depended on not only the formation of oxides but also the fracture properties of the top coatings.
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Masayuki ARAI, Uichi IWATA
Article type: Article
Pages
227-228
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The cohesion of thermal barrier coating is reduced by a formation of thermally growth oxidation (TGO) layer at the interface between top coating and bond coating under a high-temperature environment. TGO growth behavior at a constant temperature has been treated mainly on some papers. It is more important to comprehend TGO growth behavior under variation of temperature, because of subjecting cycling thermal loading in actual gas turbine blade. In this study, TGO growth process under variation of temperature in 8YZ/CoNiCrAlY thermal barrier coating system is examined, and then the growth law is shown.
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M. Okazaki, M. Sakaguchi, I. Ohtera, Y. Harada
Article type: Article
Pages
229-230
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A new method employing coating technique has been proposed, in order to explore the methods to prevent the undesirable effect due to cellular microstructure on mechanical properties of CMSX-4. The experiments supported the validity of the method. The long term stability of the proposed coatings was also investigated.
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Satoru IZAWA, Masaaki MATSUBARA, Kikuo NEZU, Kenji SAKAMOTO, Masayuki ...
Article type: Article
Pages
231-232
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This study is concerned with evaluating effects of a load history on the plastic collapse load of stainless steel pipes with a notch subjected to combined tension and bending. The stress state of a plastic collapse point was assessed using a membrane stress and axial displacement chart as well as a bending stress and deflection angle chart. As a result, it has been found that a different load history affects the formation of the plastic region and also the position of the plastic collapse point.
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Akira MORITA, Hiroyuki KAGAWA, Shiro KUBO
Article type: Article
Pages
233-234
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A series of finite element analyses were performed for a multiply edge-cracked plate with finite width subjected to a concentrated load at a point on the crack surface. The ratio of crack length to plate width a/W was varied in a range from 0.1 to 0.9. Stress intensity factor K was evaluated by means of the virtual crack extension method. Calculated K values were correlated with the equation proposed by Hartranft et al for a single edge cracked semi-infinite plate. K values of a multiple edge cracked plate with finite width subjected to uniform remote tensile stress were evaluated using the present results and compared with the values proposed by Bowie for a multiply edge cracked semi-infinite plate. The validity of K values database calculated in this study was shown by this comparison.
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Terutaka FUJIOKA
Article type: Article
Pages
235-236
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In life assessment of a crack-like defect, treatment of secondary stresses is more important than that of primary stresses in view of practical application to an actual elevated temperature component. However, most of the previous experimental studies have been based on crack propagation tests performed in load-controlled conditions. Thus applicability of fracture mechanics based approach to actual industrial purposes is still uncertain. The author has made some suggestions, based on mostly theoretical and numerical investigations, for crack propagatin life prediction including treatment of realistic secondary stresses. This paper presents an experimental validation of the previously proposed methodologies by performing creep-fatigue crack propagation test of a typical high temperature material, CrMoV forged steel under displacement-controlled loading.
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Hiroyuki KAGAWA, Masato KURITA
Article type: Article
Pages
237-238
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Fatigue crack propagation behavior of IN738LC was investigated under two kinds of loading conditions. Load controlled (LC) tension-compression tests were carried out using center-cracked-tension specimens under the constant temperature condition. Obtained data was correlated with Paris law with the same exponent value and the effect of test temperature and frequency on the coefficient value was investigated. The coefficient value showed obvious dependency upon the loading frequency under the test temperature of 850℃ or higher. Thermal-mechanical fatigue (TMF) tests with out-of-phase cycling were also performed using cylindrical specimens, where temperature range was held constant at 400℃ and minimum temperature was either 400℃ or 500℃. In each test, fatigue loading was interrupted several times, and crack length was measured by means of replica technique. Obtained data was correlated with Paris law and compared with the data of LC tests. Crack propagation data of TMF tests tended to approach the data line of LC tests at the lower temperature, as the crack length became longer.
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Naoto KASAHARA, Hideki TAKASHO
Article type: Article
Pages
239-240
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This study has clarified mechanism of thermal stress induced by spatial fluctuations of fluid temperature. Its mechanism was formulated into a frequency response function of thermal stress to fluid temperature. To validate this function, it was applied to an actual thermal fatigue problem and was compared with finite analysis results.
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Takashi OGATA, Takayuki SAKAI, Masatsugu YAGUCHI
Article type: Article
Pages
241-242
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Assessment procedure of crack initiation life of a gas turbine blade based on analytical way was proposed in this study. Elastic-plastic and creep analysis was conducted using 3D FE model of the blade. It was found that axial and torsional stresses were yield on the surface of the blade and triaxil tensile stress occurs at cooling hole during operation. Crack initiation life of the blade was predicted by previously proposed life prediction method which was defined based on biaxial thermo-mechanical fatigue test results. It was concluded that the most sever portion in terms of crack initiation is mid-height of leading edge and crack initiation lives at mid-height of pressure and suction sides are three to five times longer than that of the leading edge.
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Yeonkyeong LEE, Sinsaku ARIMOTO, Masao SAKANE
Article type: Article
Pages
243-244
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This paper proposes a transmission a.c. potential method for determining the position and depth of internal defects embedded in a component. Alternative currents from 100Hz to 5000Hz were applied to internally holed specimens with 0.5mm-2.0mm diameters and 2.0mm-8.0mm depths. Position and depth of internal defects were determined by two stages scans of two probes. The hole position was determined by the first scan where two probes were scanned simultaneously and hole depth was determined by the second scan where only a probe was scanned. The transmission. a.c. potential method was capable to determine the postion and depth of internal defect accurately.
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Hiroyuki FUKUTOMI, Takashi OGATA
Article type: Article
Pages
245-246
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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It is quite important to nondestructively comprehend the depths of surface-breaking cracks for the life assessment and judgmental standards for timing to recoat blades in land-based gas turbines. Eddy current testing (ECT) is very attractive because it offers both very high detectablity and high scanning speeds. However it is not straightforward to apply a conventional ECT probe to blades having complex geometry. Flexible ECT probe arrays have been developed to overcome the major limitations of existing systems. The use of an array of sensors allows cracks of all lengths to be detected and will ultimately allow real time data imaging to provide rapid inspection and easy interpretation. In this study based on eddy current techniques, crack detection equipment was developed and applied to 1100℃-class gas turbine blades for field use. By using this equipment, ECT data can be quickly taken at leading edges, and concave and convex sides of the blade mounted in a rotor after a turbine casing is removed.
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Yoru WADA
Article type: Article
Pages
247-248
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A large 3.5 inch thick compact tension specimens (CT) were hydrogen pre-charged in an extra high capacity autoclave and crack growth tests were conducted on temper embrittled 2.25Cr-1Mo steels. The recent generation steel with high purity, less temper embrittlement susceptibility, showed sub-critical flaw growth over 10 days at room temperature. The crack growth rate observed was relatively constant rate at 5 to 8x(10)^<-5> mm/sec regardless of the slow increase or decrease in stress intensity factor at the crack tip. On the other hand, the temper embrittled 60's generation steel showed brittle, fast fracture at low stress intensity factor (K_1=45 MPa√<m>). Since the fracture toughness of this steel without hydrogen condition was higher than this, it is considered that the fast fracture was occured due to the presence of hydrogen. This fast fracture took place remarkably below 86℃.
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Takashi MURAKAMI, Satoshi IZUMI, Shinsuke SAKAI, Takashi OGATA
Article type: Article
Pages
249-250
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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For life extension of fossil power plants, one of the most important subjects is to evaluate creep damage in high-temperature components such as boilers and turbines. In the life prediction, hardness is very important, because it has good correlation with some properties of materials and it is easy to measure it. Until now, hot hardness hasn't been used for the life prediction. This paper reports the availability of using hot hardness for more accurate life prediction technique.
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Yoshio TAKAGI, Shigeru Otsuki, Yoru WADA, Yasuhiko TANAKA
Article type: Article
Pages
251-252
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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CrMoV turbine rotor steel is strengthened by dispersed fine carbides, however carbides precipitated and coarsened at grain boundary during creep exposure. The carbide structure also changes from Fe_3C to M_<23>C_6 type carbide as coarsening. The carbide structure was electrochemically isolated by solving the matrix and analyzed with X-ray diffraction analysis. The X-ray peak intensity ratio of M_<23>C_6 to Fe_3C is tentatively defined as J-parameter. In order to evaluate the efficacy of J-parameter for creep damage evaluation, creep interruption test was conducted. The J-parameter increased with increasing creep and also correlated well to mean interparticle spacing. The change in J-parameter was affected by the chemical composition of the steel.
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Hideo TANAKA, Masaharu MURATA, Fujio ABE, Koichi YAGI
Article type: Article
Pages
253-254
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In order to assess material deterioration at long times, the microstructural evolution has been investigated for SUS316 austenitic stainless steel after creep rupture tests for up to 150,000 h at 550 to 750℃. A variety of second phases, such as M_<23>C_6 carbides, G phase, Laves phase, σ phase and χ phase, precipitate at grain boundaries and within grain during creep. The σ phase forms earlier as temperature increases and continues to grow in size over 100,000 h. The length of σ phase can exceed 50μm during long-term creep tests. The total amount of precipitates reaches an equilibrium by 2,000 h at high temperatures of 700 and 750℃, while it needs long times of 20,000 and 50,000 h at 650 and 600℃, respectively. The acceleration effect of stress on the precipitation during creep decreases with decreasing stress and increasing test duration. The distributions of precipitates are substantially the same between the specimen gauge portion under stress and the specimen head portion under no stress at long time conditions over 100,000 h. The amount of total precipitates or σ phase particles can provide a useful measure for the estimation of operating temperature and time of high-temperature components.
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Hidetaka NISHIDA
Article type: Article
Pages
255-256
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The surface of welded joint specimens for service material are applied by Boron element, they are taken Heat Treatment at 630℃×1000Hour. We have creep rupture tests them at 630℃×58.8MPa, as a result, Residual Life extends 1.9 times, and one of Simulated Coarse, Fine Heat Affected Zone Specimens are 2.5〜4.5 times at 630℃×78.4MPa on creep rupture tests, and it is confirmed that Boron is segregated on the Grain Boundary and trespass to center section of specimen by diffusion, therefore, We consider that recovery of life by applying Boron is possible on the stress above 58.8 MPa.
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Yasuihiro HARA, Tsukasa OKAZAKI
Article type: Article
Pages
257-258
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Many cracks occurred at 308 austenitic stainless welds made by flux cored arc welding(FCAW) process in hot-wall type fluid catalytic cracking(FCC) units operated at a service temperature of more than 640℃ in oil refineries. During investigation the cause of cracking, it was cleared that the high temperature characteristics of these welds such as creep strength at over 640℃ are not fully understood due to little available data. Among many factors that may have caused cracks, a small amount of Bi contained in the weld metals was considered to be the most predominant factor that deteriorated creep ductility and increased reheat cracking susceptibility of the weld metals. This report shows also the results of the effect of welding process and weld metal type on creep rupture properties that contain Bi free and Bi free weld metal.
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Nobuyoshi Sato
Article type: Article
Pages
259-260
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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On of the major causes of leaks of storage tanks is thickness reduction of bottom plates due to unexpected corrosion of down surfaces of plates. And it is extremely difficult to detect such defects or analyze corrosive trend of the whole bottom plates by ordinary spot inspection methods using ultrasonic inspection equipment. The high-speed bottom plate inspection system consisting of ultrasonic measuring unit having a 300mm of inspection width and data processing unit enables to identify such corroded condition accurately by continuous measurement of whole bottom plates of tanks. This system will contribute to dedicated predictive maintenance to ensure safety operations of tanks.
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Kimihiro KAIMORI, Makoto NAGASE, Akihiko HIRANO, Sadato SHIMIZU
Article type: Article
Pages
261-262
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This paper introduces the Risk Based Maintenance method for Nuclear power plants (NPPs) in US. By implementing this method, one US nuclear power plant has achieved huge cost and Man-REM savings. These reductions have been brought by optimization of inspection/maintenance planning. As a result of that optimization, many NPPs have been operating at 18- or 24-months cycles and their utilities can get much income. To achieve these objects in Japan, Hitachi has started to construct knowledge database that is based on manufacturing know-how, engineering and/or design skills, operating data and laboratory data. Furthermore, Hitachi is trying to make a criterion that is based on probability of unplanned shutdown to determine risk significance of nuclear power plants.
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Kazunari FUJIYAMA, Taiji HIRASAWA, Kazuhiro SAITO, Toshihiro FUJIWARA, ...
Article type: Article
Pages
263-264
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A risk-based maintenance system was established to improve economical benefits of maintenance based on probabilistic risk assessment. The system has four subsystems for field data management, for probabilistic life assessment, for probabilistic risk assessment and for maintenance planing. Unreliability functions of operation hours or number of starts were derived from the reliability analysis of field inspection data and the life assessment using statistical material data. The risk was calculated by summing up the recovery costs expected by the unreliability along event trees. The maintenance planning was conducted by comparing operation benefits, preventive maintenance costs and risk costs. This system can be applied to various types of steam turbines by using the unified unreliability functions expressed by life or event governing parameters.
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Shinsuke SAKAI, Satoshi IZUMI, Takashi YOKOYAMA, Toshiaki MAKINO
Article type: Article
Pages
265-266
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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We attach importance to the decision-making performance in risk assessment. Though conventional risk assessment is used in the operational stage, it is investigated to apply the risk assessment in the design stage of railroad train. Specifically, the design of ceiling-shelf module is considered. By introducing the risk evaluation, not only the evaluation of function of single part but also the total performance for safety can easily be treated. Besides, uncertainty property is also able to be included in the assessment. After the formulation of risk assessment is stated, the application for several decision-makings in ceiling-shelf module will be shown.
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Toshikazu SHIBASAKI, Takayasu TAHARA, Shinsuke SAKAI
Article type: Article
Pages
267-268
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The research committee of RBM organized by HPI performed the questionnaire to investigate the usage of RBI in Japan in 2001. This paper describes the result of analysis and to point out problems to implement RBI widely.
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Koichi Yagi
Article type: Article
Pages
269-270
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The development of Materials Risk Information Platform was started from 2001,in order to support the selection of safe materials and the safe use of materials, receiving a risk. This platform is developed under the cooperation of academic societies, research institute and industries as the center of National Institute for Materials Science. This paper shows the present status of this development, especially of main system.
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Jun TAKAHASHI, Hiroaki ZUSHI, Kazuro KAGEYAMA, Hitoshi YOSHINARI
Article type: Article
Pages
271-272
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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As pure risks this paper shows first a climate change and a jump in crude oil price, and an ultra-lightening weight of mass production automobiles by using carbon fiber reinforced plastics (CFRP) is shown as an effective measure against these risks. Then, speculative risks including losses and benefit due to the ultra-lightening, such as a greater impact deceleration at collision, lower fuel expenses, etc., are shown and necessary researches for CFRP are discussed. Finally, techniques concerning low cost and speedy manufacturing, 3R (reduce, reuse and recycle), performance evaluation and numerical simulation are shown to be established.
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Hiroaki ZUSHI, Jun TAKAHASHI, Kazuro KAGEYAMA, Hitoshi YOSHINARI
Article type: Article
Pages
273-274
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Substitution of carbon fiber reinforced plastics (CFRP) for the structural material of transport vehicle is quite effective in mass reduction, fuel efficiency and, hence, the mitigation of global warming. In this paper, life cycle energy consumption and CO2 emission of gasoline and fuel cell vehicles are estimated first in both conservative and ultra lightweight cases. Then the effect of these ultra lightweight automobiles on the world-wide CO2 reduction from 2010 to 2040 is simulated under the Asian motorization.
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Satoru NAGAOKA, Hiroaki ZUSHI, Jun TAKAHASHI, Hitoshi YOSHINARI, Kazur ...
Article type: Article
Pages
275-276
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Lightening of vehicles is quite effective to reduce global oil consumption and CO2 emission. For this purpose, CFRP (carbon fiber reinforced plastics) has lately attracted attention as an ultimate lightweight structural material. In this paper, the condition of public acceptance of CFRP as a structural material of mass production automobile is discussed. At a driving stage, we found great benefit of CFRP concerning cost, performance and comfort due to its lightweight and flexibility in design. On the contrary, at a manufacturing stage, the price of carbon fiber is still expensive and low cost and speedy manufacturing techniques should be established. And 3R technology must be also developed, and which was shown to play an important role to reduce the price of CFRP. Finally, to relieve the greater impact damage of lighter automobile at collision, shock absorber and additional safety equipment can be prepared by using a small part of the lightening weight.
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Shoji Yamane, Fujio Itani, Toshiyuki Kuroki, Yoshihiro Endo, Yutaka Mi ...
Article type: Article
Pages
277-278
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Technology of Carbon Fiber Reinforced Plastics (CFRP) recycling and Standardization of CFRP recycled products were investigated. CFRP with epoxy resin matrix was successfully crushed with a shearing type crusher and the size of the crushed CFRP was classified by passing through a mesh screen. Various methods of matrix resin removal from CFRP to yield recycled carbon fiber (CF) were also investigated. Thermal decomposition of matrix resin in air or inert atmosphere was found to be a good candidate of recycling CF. A standardization plan of the measuring methods of crushed CFRP and recycled CF will be proposed. This investigation is executed under the consignment of NEDO (New Energy and Industrial Technology Development Organization).
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Shinsuke SAKAI
Article type: Article
Pages
279-280
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This paper shows the way to apply LCA as a decision making tool using sensitivity analysis. First, some problems to be solved in current LCA are summarized. Next, the importance of introduction of sensitivity analysis in LCA will be shown and its application to improvement analysis is proposed. Finally, the proposed idea is confirmed by applying the method to an example of steel making process.
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Tetsuya SUZUKI, Fumi TESHIBA, Hiroaki ZUSHI, Jun TAKAHASHI, Kazuro KAG ...
Article type: Article
Pages
281-282
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Nowadays, vehicles impose more and more burdens on environment. They are largest in driving, so it brings the greatest result on improving fuel consumption by lightening their weight. Therefore between current and lightweight automobiles using CFRP, we compare and study their energy consumption and CO_2 emission by LCA. Basic unit, such as energy consumption and CO_2 emission per weight, of current CFRP is very large, so that the life cycle environmental load of the automobile increases instead of decreasing weight. Finally, simulations in this study clearly show that 3R technology of CFRP must be developed to apply and decrease the life cycle environmental load of automobiles.
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Hideki NAGAI, Jun TAKAHASHI, Kiyoshi KEMMOCHI, Junichi Matsui
Article type: Article
Pages
283-284
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This paper described an estimation of inventory data of advanced composite materials. Inventory analysis, especially about energy consumption of production and recycling processes of carbon fiber reinforced plastics (CFRP) was mentioned. In production process, data of energy consumption and emissions in various fabricating processes were calculated and compared with the data of production of carbon fiber and prepreg (pre-impregnation materials). Amount of energy required in production of carbon fiber is much larger than other processes and it was proved that it is most important process for improvement. In recycling process, data of material, chemical and thermal recycling were estimated. Since energy needed in material recycling is much smaller than that of production process, the validity of material recycling was shown.
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Masako Yamato
Article type: Article
Pages
285-286
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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LCA (life Cycle Assessment) is a method for evaluation environmental impact of product life cycle. The scope of evaluation is from resources extraction to disposal. LCA is used as a tool for design in consideration of life cycle environment. (ES)^3 is the lightweight concept car that has some technology for fuel-efficient and low emission. The aluminum body was adopted as one of the lightweight technology. We have done LCA in order to evaluate environmental improvement effect of not only running phase but also total life. This report introduces the LCA result.
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[in Japanese], [in Japanese], [in Japanese]
Article type: Article
Pages
287-288
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In order to reduce CO_2 emissions from automobiles, a highly fuel-efficient hybrid vehicle, the "Insight", has been developed at Honda. Life cycle CO_2 emissions are compared for the aluminum-bodied Insight, a simulated steel-bodied Insight, and a conventional gasoline vehicle. Life cycle CO_2 emission is still dominated by the in-use fuel consumption. However, the contribution of CO_2 emission from material use and processing could increase when the vehicle fuel consumption is greatly reduced. The use of recycled aluminum reduces CO_2 emission from the aluminum-bodied Insight.
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Hiroyoshi Murakami
Article type: Article
Pages
289-290
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Kanichiro OGAWA, Juksanee VIRULSRI, Shinsuke SAKAI
Article type: Article
Pages
291-292
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In the recent years, the necessity of flaw evaluation system is increasing with a lot of demands in applicable program that is convenient for users to operate. So it is important to share the technique of flaw evaluation system all over the world and Java is expected to be a very strong tool to achieve this purpose. This paper presents the developed programming system. The past system doesn't have general-purpose. But new system is distributed for high general-purpose. For distributing system, JavaRMI and XML are introduced.
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Kenta YAMAGIWA, Satoshi IZUMI, Shinsuke SAKAI
Article type: Article
Pages
293-294
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This paper describes the proposition of the characterizing method of fracture surface using the wavelet transformation, and the discussion of the validity of the method. The analyzed fracture surface is the fatigue fracture surface, and the method characterizes the local feature of striation. By the method, the boundary line between the striation area and the non-striation area is distinguished, and the striated surface ratio is calculated. The method estimates the absolute value of wavelet coefficient and the mother function is the Gabor function. Applying the method to the real fracture surface and the simulated fracture surface, the availability of the method is examined.
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