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Masataka TANAKA, Artur GUZIK, Toshiro MATSUMOTO
Article type: Article
Pages
95-96
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper we present an application of FEM-based filtering technique to the estimation of multidimensional, spatially and temporarily varied, boundary conditions (BC) in thermoelasticity problems. The technique allows one to sequentially solve problems with constraints equations based on non-standard time step approximations and, furthermore, exploit measurement data from several time steps. An numerical example demonstrating robustness of the approach is included
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Hirotsugu INOUE, Kazutaka KATO, Kikuko KISHIMOTO
Article type: Article
Pages
97-98
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Thermoelastic stress analysis is a technique of experimental stress analysis to visualize distribution of the sum of the principal stresses utilizing the thermoelastic effect of elastic solid. It is normally assumed that the object is in adiabatic condition and, therefore, that the distributions of the temperature and the sum of the principal stresses are identical. However, this is actually not the case because of the heat conduction within the object. In this study, a simple inversion technique has been proposed for reconstructing the distribution of the sum of the principal stresses from the temperature distribution obtained by the thermography. The effectiveness of this inversion technique has been verified through numerical simulation. In particular, the mollification method is shown to be effective for improving the accuracy of reconstruction.
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Toshiro MATSUMOTO, Masataka TANAKA, Tomoki TSUKAMOTO
Article type: Article
Pages
99-100
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The boundary element method, with the dual reciprocity method (DRM) is applied to an identification problem of point sources in two-dimensional potential problems. The source term consisting of multiple point sources is assumed to be a distributed source and is approximated with a linear combination of radial basis functions. By applying DRM, the domain integral originated from this assumed source term is converted into boundary integrals, so that no internal cells are needed in evaluating unknown coefficients of the approximated source distribution. From the identified source distribution, the positions of the concentrated sources are estimated by calculating the coordinates of the local maximums. Then, the intensities of the point sources are evaluated by starting from the BEM formulation with point sources.
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Hiroshi NOGUCHI, Toyomitsu HARADA, Takashi YOSHIMURA
Article type: Article
Pages
101-102
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper, a notch in a 2-dimensional or 3-dimensional actual structure surface is considered as an observed domain. And the method of crack detection of the observed domain is proposed. A few strain gauges and the stress function in the 2-D or the Body Force Method in the 3-D are used for the method. And the observed domain in 3-D is not treated as a 3-dimensional part. However, the Body Force is distributed in the observed domain, and the influence of 3 dimensions is virtually added to the observed domain of a plane stress problem.
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Masaaki TAKAGI, Daiki SHIOZAWA, Shiro KUBO, Takahide SAKAGAMI
Article type: Article
Pages
103-104
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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When a piezoelectric film is glued on the surface of a cracked structure subjected to mechanical load, change in distribution of electric potential is observed on the surface of piezoelectric film. Based on this phenomenon, the passive electric potential CT (computed tomography) method was developed for the identification of two- and three-dimensional cracks based on the FEM inverse analysis. In this paper, this method was applied to identify through-thickness inclined crack. Electric potential distribution calculated by the FEM showed characteristic changes corresponding to angle and size of crack. Numerical simulations were carried out on estimation of location, size, and angle of the inclined crack. It was found that the passive electric potential CT method using piezoelectric film was useful for the quantitative identification of the through-thickness inclined crack.
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Masataka TANAKA, Toshiro MATSUMOTO, Y. B Wang
Article type: Article
Pages
105-106
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper is concerned with inverse analysis for identification of unknown parameters corresponding to load and material constants of an elastic plate subjected to dynamic loadings. The extended Kalman filter and the boundary element method are combined to use for the inverse analysis. Inverse analysis is carried out using strain responses. The featrues of the present inverse analysis are demonstrated.
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Yoshitsugu KAWAKAMI, Ryuji ENDO, Nobuyoshi TOSAKA
Article type: Article
Pages
107-108
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper is concerned with the inverse analysis of the fluid coupled system by coupled free vibration analysis, in combination with filtering algorithm. The structural damage analysis is generally formulated as an inverse problem. The formulated inverse problem must be analyzed under the consideration of stochastic properties on the response of structural system. The filtering algorithms have been known as one of the inverse analysis method. In this study, algorithm based on parametric projection filter is employed as new analytical algorithm on the inverse analysis. The coupled natural frequencies used as the observations and stochastic properties of system responses adopted the data obtained by experimental modal analysis. From identification results, adaptability and characteristics of the algorithm based on parametric projection filter are made clear through the inverse analysis of the fluid-structure interaction coupled system.
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S. Shirai, M. Okazaki
Article type: Article
Pages
109-110
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Behavior of the interfacial crack which grew parallel to the loading axis under cyclic loading in a CoNiCrAIY coated Ni-base superalloy coating was investigated. The result wascompared with that of the opening type of crack. It was shown that the former type of crack revealed different behavior from the latter. The observation of the path of the former type of crack indicated that the contact stress acting on the crack plane played an essential role. Discussion was made on the frictional force, based on Interface mechanics.
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M. Okazaki, S. Shirai, T. Uchiyama
Article type: Article
Pages
111-112
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Effects of process variables and the long term thermal exposure on adhesion strength of top coat in a APS-TBC were studied. The experiments indicated the adhesion strength was significantly changed, under the influences of many factors; e.g., pore ratio, elastic moduli, TGO formation and intersplats microcracks.
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Masayuki ARAI, Uichi IWATA, Tatsuo SUIDZU, Kazumi TANI
Article type: Article
Pages
113-114
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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When thin coated material plate is subjected to a high-temperature, the plate is bended due to difference of thermal expansion coefficient between coating and substrate. Therfore, stress in coating layer under a high-temperature will be able to measure directly through a bending deflection of the plate. The aim of this paper deals with measurement method of in si-tu stress in coating layer under thermal cycling condition. The top coating material treated in this study is conventional and virtical cracked APS 8wt%Y_2O_3-ZrO_2. Bending deflection is measured by laser senser, and in-situ stress in coating layer is obtained based on classic bending beam theory. Comparison about thermal stress between TBCs will be done.
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Takashi NAKAMURA, Hiroshi NAKAMURA, Toru NOGUCHU, Kichiro IMAGAWA, Hit ...
Article type: Article
Pages
115-116
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Polymer materials are widely used for space structures such as satellite members, thermal blankets, adhesives, lubricants etc. There are many hazards for polymers in space environment such as atomic oxygen, UV radiation, ionizing radiation, high vacuum etc. In particular, AO is the most damage source in the low earth orbit (LEO). This paper provides a method of modifying the surface of PEEK sheets by direct-fluorination to protect them from AO. Chemical analyses and tensile test were carried out to study material properties of fluorinated PEEK. AO irradiation experiments were conducted to investigate AO resistance properties of fluorinated PEEK. The results showed that the fluorinated PEEK had better tensile properties than the pristine PEEK, and that AO erosion resistance of PEEK was improved by direct-fluorination method.
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Hidehiko KIMURA, Yoshiaki AKINIWA, Keisuke TANAKA, Yasuaki TAHARA, Yut ...
Article type: Article
Pages
117-118
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The effect of crystallographic orientation and microstructure on fatigue crack propagation behavior in ultrafine-grained specimens with the average grain size of less than 2μm was investigated by EBSP (Electron backscatter patterns). The results show that fatigue crack bifurcation, which has been proven to be the dominant factor of the excellent fatigue property introducing crack closure, was introduced either at grain boundaries or within grains with the ratio of 1 : 1. The mechanism of the bifurcation was explained by introducing the slip factor. ζ. Fatigue crack bifurcates at a grain boundary when it propagates from a grain containing a single slip system with the outstandingly largest ζ to the other grain holding many slip systems with large ζ. The intragranular bifurcation was observed in the grain with dozens of slip systems with the same largest ζ.
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Masao KINEFUCHI, Eiichi TAMURA
Article type: Article
Pages
119-120
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Effect of stress concentration of fatigue strength of hot-rolled sheet steel with high tensile strength was discussed. As a result, fatigue strength reduction factors (β) of notched specimens was equal to the stress concentration factors (α) that were less than 3.0. It was supposed that gradient of stress distribution near the notch root was one of the important factors for fatigue limit. β of lap-joint specimen with machined toe was smaller than that of the notched specimen with the same α. Residual stress introduced welding process was supposed to affect the fatigue limit of the lap joint.
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Hiroshi MATSUNO, Yoshihiko MUKAI
Article type: Article
Pages
121-122
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Equivalent Stress Ratio, which is proposed as a parameter for correspondence between notched and unnotched fatigue data, is applied to fatigue data concerning torsion, bending and their combination loading. Fatigue strength of a notched specimens is formulated as a function between effective stress ranges at notch roots and equivalent stress ratios. Fatigue crack propagation rates is also constructed based on the equivalent stress ratio.
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Surya Irawan Yudy, Yoshihiko HAGIWARA, Shinichi OHYA
Article type: Article
Pages
123-124
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Fatigue crack of pure aluminum plates with unique anisotropy propagated to rolling direction that made 30° to loading direction. The crack propagated as a mixed mode I+II crack. Effects of plate thickness to fatigue crack were observed by conducting fatigue test on CCT specimens with thickness of 0.8mm, 1.5mm and 2.5mm. The stress intensity factor of the crack was analyzed with Finite Element Method (FEM) using the displacement extrapolation method. As the result, the crack starts to grow to rolling direction as △K_<*>=5∿8MPa・m^<1/2>. It is also confirmed that the thicker plates cause the smaller monotonic plastic zone size r_p on the crack tip. It leads to near plane-strain condition on the crack tip and the crack grows easier to rolling direction.
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Takashi HONDA, Masazumi TANAKA, Etsuji YOSHIHISA, Yutaka MAEDA
Article type: Article
Pages
125-126
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The link chains, which are used in lifting machines such as a chain hoist and a conveyor, are very important components in those machines because the fatal accident may occur by the falling of a load when a link chain is fractured. They are usually fractured by fatigue. Therefore the fatigue of the link chain becomes large problem in loading facilities. However, not only fatigue characteristics but also stress distributions have not been clear due to the complex shape of a link chain. In this paper, in order to clarify fatigue characteristics of link chain, the stress distribution in a link chain was analyzed by the finite element analysis (FEM) and the result was compared with the measurement values by strain gauges. In addition, fatigue tests of link chains were carried out in order to evaluate the fatigue strength, and then the fatigue fracture surfaces were observed by the scanning electron microscope (SEM).
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Ryuichiro EBARA
Article type: Article
Pages
127-128
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this paper, ultrasonic fatigue testing results of various materials is briefly reviewed. The emphasis is focused upon the rapidness and effectiveness of ultrasonic fatigue testing which enable screening tests for structural materials such as steam turbine blade materials. It is also exemplified that the ⊿K_<th> can be easily measured at the very slow da/dN between (10)^<-8>∿(10)^<-14>m/cycle. Long term fatigue and corrosion fatigue behavior of structural materials can be investigated by use of ultrasonic fatigue testing. The generation of heat in specimen and frequency effect are also discussed. Finally a couple of future problems to be solved are touched in brief.
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Motohiko YAMADA
Article type: Article
Pages
129-130
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The original purpose of this study is to develop an evaluation system of corrosion level in the inner surface of galvanized steel tubular sections as a maintenance engineering for steel structures. As the first step of this study, the application of ultrasonic testing is attempted to the thicness measurement of galvanized steel plate elements, which is not yet authorized as a practical measure. In a preliminary study, it was clarified that the application of the speed of longitudinal ultrasonic wave in zinc to the layers composed of zinc and several alloys of iron and zinc results in a conspicuous underestimation of the thickness of galvanized steel plate, and in the present sudy, the speed of longitudinal ultrasonic wave in the specimen's steel plate is applied to the whole specimen of galvanized steel plate. This result is compareed with the thickness obtained by the different devices.
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Motohiko YAMADA
Article type: Article
Pages
131-132
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The final goal of this study is to develop an evaluation system of corrosion level in the inner surface of steel tubular sections as a maintenance engineering for steel structures. As the first step of this study, the ultrasonic testing with high frequency transducers was applied to the detection of artificial roughness in the steel plate's reverse side which was composed of parallel thin grooves. The correlation between the roughness and the ultrasonic echo was minutely examined on various conditions of both the roughness level and the ultrasonic excitation frequency, and the following results were obtained; (1) the change of thickness is related to a statistic amplitude of grooves such as Ry, and (2) the pitch of groove corresponds to the half wave length of the wave component in the echo excited by roughness.
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Hitoshi ISHII, Yoshikazu IWASE
Article type: Article
Pages
133-134
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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To obtain long life fatigue properties of various materials within a reasonable time, intermittent ultrasonic loading method is a promising one. The signal pattern of the intermittent ultrasonic loading method consists of a block of duty period and pause period. However, no systematic work of the effect of duty period on the S-N diagram has been done. In the present study, various duty periods were applied to SNCM 439 temperd at high or low temperature and the difference in their fatigue properties was studied. No practical difference was observed, and as long as the fundamental condition that the intermittent method is applied for suppressing the heat generation by internal damping is maintained, any combination of the duty and pause period can be used to obtain the reasonable fatigue data.
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Yoshiaki AKINIWA, Keisuke TANAKA, Yuji MURASAME
Article type: Article
Pages
135-136
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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A bearing steel (JIS SUJ2) and nickel chromium molybden steel (SNCM439) were fatigued with the ultrasonic fatigue-testing machine (20kHz) in laboratory air. In the very long-life regime, the decline of fatigue limit was seen. The origins of crack initiation were mostly internal inclusions. However, even when the specimen broke in a long life region, some cracks were initiated from specimen surface. Fracture surface were observed with a scanning electron microscope (SEM). The fish-eyes were observed in the specimens broken from the internal inclusions. The fracture surface could be divided into three regions. The first region surrounding inclusion was a facet area. The crack propagation in the facet region was Stage A and the crack propagation outside the facet region was Stage B. When the fatigue cracks reached the specimen surface, the fatigue cracks propagated as surface cracks. The crack propagation rate in each region was estimated to be a power function of the stress intensity range. Fatigue life was calculated by integrating with the crack propagation laws determined from the data obtained for the rotating bending. The predicted fatigue life agrees with the experimental result.
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Akitoshi MATSUO, Hirohisa KIMACHI, Noboru EGAMI, Shigehito NISHIMURA
Article type: Article
Pages
137-138
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this study, the fatigue tests for some engineering steels under the condition of stress rate R=-1 were conducted by the ultrasonic fatigue testing machine. The frequency of this machine was 20kHz. But net frequency f_<net> was lower than 20kHz. Because the intermittent operation with air cooling were conducted in order to suppress the heat generation by high speed test. The relationship between crack propagation rate and stress intensity factor range was compared with that of conventional fatigue test for low frequency (20kHz). The relation of ultrasonic was good agreement with that of conventional fatigue test. In-situ observation of a crack initiation and propagation was conducted. Striations were observed on the fatigue fracture surface.
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Hitoshi ISHII, Motoshi TERAO
Article type: Article
Pages
139-140
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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To ensure long life reliability of the machine parts with mechanical notches, ultrasonic fatigue tests were performed on the rod specimens with U- or V- shaped circumferential notch at the center. High temperature tempered S35C and low temperature tempered SNCM439 were used as the test materials. The results were compared to the dumbbell type results. No difference was observed in the fatigue behavior by the notch shape. However, some difference was observed in the fatigue strengths, especially those below (10)^7 cycles, by the notch shape. Notched specimen with high stress concentration factor seemed to show a little higher fatigue strength than the one with low stress concentration factor.
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Yoshiyuki Furuya, Saburo Matsuoka
Article type: Article
Pages
141-142
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This report reveals gigacycle fatigue properties for a modified-ausformed SMn443 steel. The steel has an advantage in recycling since the steel dose not contain Cr and Mo which are difficult to be removed in re-melting. Modified-ausformed, oil-quenched and water-quenched steels were prepared for fatigue test, preparing two different tensile strength specimens of 1400 and 2000MPa. The low-strength modified-ausformed steel (AF1400) was free from fish-eye fracture with a fatigue limit of 770MPa at (10)^9 cycles, while the low strength oil-quenched steel (QT1400) caused fish-eye fracture. Although the high-strength modified-ausformed steel (AF2000) was suffered from fish-eye fracture, the fatigue limit at (10)^<10> cycles was 830MPa that was higher than 710MPa of the water-quenched steel (QT2000W) tempered at 473K. The fatigue limit at (10)^9 or (10)^<10> cycles for both oil-quenched steels (QT1400 and QT2000) could not be determined because of temperature increase of specimens in 20kHz tests. The fracture surfaces revealed optically dark areas (ODA) even in modified-ausformed steel since the modified-ausforming was not perfect in this research.
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Takayuki ABE, Yoshiyuki FURUYA, Saburo MATSUOKA
Article type: Article
Pages
143-144
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Giga-cycle fatigue properties were investigated forheats B and C of SUP7 spring steels tempered at 430℃. Rotating bending, high-speed servohydraulic and ultrasconicfatigue testing machines were used for 30 or 100Hz, 600 or 800Hz and 20kHz tests, respectively. S-N curves under each frequency were coincident in case of fish-eye fracture with an origin of Al_2O_3 and TiN inclusions and a matrix crack for each heat, when the control volumes were equal to each other. However, heat C, in which Al_2O_3 inclusions were smaller, revealed a higher fatigue limit than heat B at (10)^<10> cycles.
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Takeshi Yamashita, Ryuichiro Ebara, Katsuaki Kubota
Article type: Article
Pages
145-146
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to clarify the giga cycle faigue behavior of hot forging die steel ultrasonic fatigue tests were conducted up to (10)^9 cycles. The frequency was 20kHz and the R value was-1. The hot forging die forging die steel with different hardness was used. At higher axial stress region fatigue life of the specimen with HRc50.8 was longer than that with HRc47.0. The lower the axial stress, the difference of fatigue life decreased. The fatigue strength at (10)^9 cycles was the same for specimens with different hardness. The effect of ion nitride on fatigue strength was not observed for both steels. Fatigue crack initiated from nonmetallic inclusions located at the subsurface for all tested specimens.
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Qiang Chen, Nu Yan, Qingyuan Wang, Norio Kawagoishi, Hironobu Nisitani
Article type: Article
Pages
147-148
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to investigate the influence of loading frequency on the fatigue strength and fracture mechanism of a high strength Al alloy, ultrasonic fatigue tests were carried out for extruded Al alloys 6061-T6 and 7075-T6,and the results were compared with those of rotating bending fatigue test. Fatigue strength of ultrasonic was higher than that of rotating bending. The crack initiation and the crack growth rate in ultrasonic fatigue were delayed compared with those of rotating bending fatigue.
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Etsuo TAKEUCHI, Yoshiyuki FURUYA, Nobuo NAGASHIMA, Kensuke MIYAHARA, S ...
Article type: Article
Pages
149-150
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The effect of frequency on giga-cycle fatigue properties was investigated for 900-MPa-class Ti-6Al-4V alloy with smoothed specimen and with 0.3mm hole notched specimens, using 120Hz electro-magnetic resonance, 600Hz high-speed servo-hydraulic and 20kHz ultrasonic fatigue testing machines. Fatigue properties were, then, independent of frequency for internal fracture with smoothed specimens and for surface fracture with notched specimens, the properties were dependent of the frequency for surface fracture with smoothed specimens.
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Shigeru DOI, Manabu YASUOKA, Daisuke GOTO
Article type: Article
Pages
151-152
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The Rotating bending fatigue tests were done using notched PDI with ion carburizing. The plain specimen with ion carburized about 30MPa than the virgin PDI, and the fatigue strength of the carburized ion notched specimens were given an equivalent to the virgin PDI. Especially, the ion carburized notched specimens are effective materials they have a better effect than lower that the notched PDI. In the recapitulation, on the element parts demanded a shallow notch, the clear distinction appeared whether ion charge or not, respectively. An important point is that carburized PDI presented two bending S-N curve not clear in high cycle fatigue. If the hardness is constantly holed to an internal point, the shape of S-N curve is unclearly appeared. But, its phenomena appeared from ion boundary layer by observation of the SEM photograph. The ion carburizing can control the charged depth by the sputtering time. Consequently, this method warrants consideration as a non-polluting process and economical use of energy. (1) Pcn S-N curve by ion carburizing effect was controlled to affect on the crack propagating in our researched meso-scopic structure. (2) Typical fracture of quasi-fish eye in the surface vicinity can be decided on a/b. Where, a : equivalent defect radius, b : equivalent cleavage radius. Accordingly, it is expressed by life cycle of S-N curve.
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Norio KAWAGOISHI, Kazuhiro MORINO, Takashi YAMAKITA, Kazunori FUKADA
Article type: Article
Pages
153-154
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to investigate the suitable nitriding condition on fatigue strength of maraging steel, rotating bending fatigue tests were carried out for steels nitrided at 480℃ for 0.5,1 and 5h. The fatigue strength was increased due to nitriding. The increase in fatigue strength and the fracture mechanism were markedly influenced by nitriding time. That is, fracturing of the specimens nitrided for 1h and 5h occurred from the specimen surface in the short life region, and from the interior in the long life region, although all of the specimens nitrided for 0.5h fractured from the surface similar to the aged specimens. Consequently, S-N curves in the former specimens showed a two-step shape. The suitable nitriding time was around 1h at the same nitriding temperature of 480℃.
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Shingo AOI, Ryuichiro EBARA, Takashi NISHIMURA, Hiroyuki TOKUNAGA
Article type: Article
Pages
155-156
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Thermal fatigue crack initiation and propagation tests for boiler steel SB410 were conducted up to 100 cycles at 573,673,773 and 873K by use of a laboratory made thermal fatigue testing apparatus. The higher the heating temperature, the lower the number of cycles for crack initiation was. The higher the heating temperature, the faster the crack propagation rate was. The thermal fatigue crack was observed by optical microscopy. Plural cracks were observed at 873K, and the crack tip was branched. While, the crack length at 573K was very short. The higher the heating temperature, the longer the crack was.
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Yasumi UEGAI
Article type: Article
Pages
157-158
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Aluminum bonding wires have generally been used for power semiconductor modules. It is necessary to clarify the fatigue strength of bonding wires under thermal cycle conditions in order to design highly reliable modules. Mechanical fatigue tests of actual bonded wires were performed at 26 and 80℃. Fatigue strength and P-S-N curves of Φ300μm wires were obtained in the range of the number of cycles between (10)^2 and (10)^7. It was found that the fatigue life of bonding life of bonding wires was almost independent of the temperature within the limit of practical temperature in use. It was also revealed that effects of wiring forms on fatigue life of bonding wires.
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Katuyuki TOKIMASA, Tadahiro TANI
Article type: Article
Pages
159-160
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Fully reversed constant amplitude creep-fatigue tests, so called fast-fast (PP) and slow-fast (CP) tests, were conducted on 316LC austenitic stainless steel thin-walled tubular specimens at 1023K in air under proportional push-pull and cyclic torsion loadings. The experimental data were analyzed based on the strainrange partitioning concept, and the partitioned equivalent inelastic strain range (Δε)_<pp> or (Δε)_<cp>, its corresponding life N_<pp> or N_<cp> and the value of multiaxiality factor MF at the peak equivalent stress was determined for each of them. The effect of stress state on the partitioned inelastic strain range versus life relations was examined by comparing the results obtained in the present study with those for the tubular specimens under push-pull or cyclic torsion loading.
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Katsuyuki TOKIMASA, Shinobu UENOTANI
Article type: Article
Pages
161-162
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The effects of ratcheting strain on creep-fatigue life of Sn-37Pb solder material were studied by conducting isothermal constant amplitude strain controlled creep-fatigue tests under four kinds of triangular strain waveform accompanying a small tensile ratcheting strain at room temperature. Four kinds of strain waveform used are so called fast-fast, fast-slow, slow-fast and slow-slow ones, and teir applied inelastic deformations can be partitioned into (Δε)_<pp>+δ_p, (Δε)_<pp>+(Δε)_<pc>+δ_p, (Δε)_<pp>+(Δε)_<cp>+δ_c, (Δε)_<pp>+(Δε)_<cc>+δ_c, respectively, based on the strainrange partitioning concept, where (Δε)_<jj> (ij=pp, pc, cp and cc), δ_p and δ_c are partitioned inelastic strain ranges, fast-strain-rate ratchet strain and slow-strain-rate ratchet strain, respectively. The test results were analyzed by using (Δε)_<ij>-N_<ij> relationships (ij=pp, pc, cp, cc) and tensile properties of the material. As the results, the creep-fatigue lives in constant amplitude creep-fatigue tests accompanying a tensile ratcheting strain could be evaluated within a accuracy of a factor of 2 by the following equation of life prediction : 1/N_f=1/N_<pp>+1/N_<ij>+δ_i/D_i (ij=pc, cp, cc), where D_p and D_c are values of material ductility obtained by fast and slow straining tensile tests, respectively. It should be noted, however, that this equation tends to evaluate CP-ratchet test life with conservatism, while CP-ratchet test life with nonconservatism.
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Hisanori NISHIMORI, Masaki SHIBUYA, Kengo FUKAZAWA, Masao SHIMIZU
Article type: Article
Pages
163-164
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to clarify the difference of fatigue strength of high strength steel between notched and un-notched specimens in terms of the maximum stress, rotating bending fatigue tests were performed of the specimens having various hardnesses and stress concentration factors with special attention to the transition of fracture mechanism mode. In terms of the nominal stress, the fatigue strength of a notched specimen was lower than that of an un-notched one, but in terms of the maximum stress the fatigue strength of the former was higher than that of the latter. The low hardness specimens showed a small difference between such fatigue strength, where fatigue crack was generated by slip bands at the surface, while the high hardness specimens presented a large difference in the fatigue strength in terms of the maximum stress with increase of stress concentration factor, where fatigue crack was generated in inclusion near the surface. Such a behavior of fatigue strength was coincident with the transition of fracture mechanism mode.
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Takashi MATSUMURA, Yasuo OCHI, Shinya YOSHIDA, Ryo TANAKA, Kiyotaka MA ...
Article type: Article
Pages
165-166
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to investigate the fatigue properties of high strength steels and surface hardened steels in the super-long life range (N≥1×(10)^7), cantilever type rotating bending fatigue tests were carried out for 2 kinds of SNCM 439 steels, which the cleanliness was different on these steels. Also, the surface of notch bottom was removed up to 30μm deep by electro-polishing, because the depth of compression residual stress in the notch bottom of grinding specimen has been 8μm. As a result of fatigue tests, in the case of SNCM 439 (D material) speciem and "high stress amplitude & short life area", it was found that the fatigue life of electro-polishing specimen were almost equal to that of grinding specimen, and in the case of SNCM 439 (S material) speciem and "low stress amplitude & long life area", it was found that the fatigue life of electro-polishing specimen were shorter than that of grinding specimen.
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Kiyotaka MASAKI, Yasuo OCHI, Takashi MATUMURA
Article type: Article
Pages
167-168
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In order to evaluate the effect of etch-pits on long fatigue life property of SUS304TP, rotating bending fatigue tests were carried out using the specimen, which had a few artificial corrosion pits. Stress intensity factor was used for the evaluation of etch-pit. Stress intensity factor was calculated by the pit diameter at surface and pit depth which were obtained by optical microscope observations or it was calculated by the pit area on fracture surface which obtained by SEM observations. As a result, the stress intensity factor of the pit bottom could be evaluated on the safety side by using optical microscope.
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Masaki NAKAJIMA, Hisatake ITOGA, Nami KAMIYA, Keiro TOKAJI, Haeng Nam ...
Article type: Article
Pages
169-170
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Two-step variable amplitude loading tests were conducted on a high carbon chromium steel, JIS SUJ2,in order to estimate subsurface crack initiation life. Particular emphasis was placed on the granular area seen around a non-metallic inclusion in fish-eye. It is known that the granular area does not appear in short life region at high stress levels, but appears in long life region at low stress levels. Therefore, making use of this property, low-high sequences with different cycle ratios at low stress level were applied to FPB-treated specimens. If the granular area is observed after testing, it can be concluded that the granular area was generated at a cycle ratio examined. It was found that subsurface crack initiation took place at an early stage of fatigue life, i.e. 5% or so.
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Takahiro SHIINA, Takashi NAKAMURA, Toru NOGUCHI
Article type: Article
Pages
171-172
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Uniaxial tension-compression fatigue tests using low-temperature-tempered Ni-Cr-Mo steel "SNCN439" were conducted over (10)^7 cycles. Based on the fractographic analysis around fracture origins and the data arranged by using stress intensity factor range, following results were obtained; (1) Even though fatigue tests were carried out until (10)^8 cycles, the fatigue limit of interior-originating fractures was not found. (2) Interior cracks grew from small defects whose initial stress intensity factor ranges ((ΔK)_<ini>) were not only higher but also lower than growth limits of surface cracks. (3) ODA (Optically Dark Area) was only observed around interior origins. ODA was formed even in a short life region where surface-originating fractures usually occurred. ODA was formed around the interior origin whose (ΔK)_<ini> was not only lower but also higher than the growth limit of the surface crack. (4) The formation of a fine bumpy pattern which was a characteristic of ODA's fracture surface was affected by cyclic load, and the fine bumpy pattern became clear as number of cyclic load increased.
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Takashi NAKAMURA, Hiroyuki OGUMA, Toru NOGUCHI, Yoshito SONOU
Article type: Article
Pages
173-174
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Uniaxial tension fatigue tests and fracture surface observations were carried out on Ti-6Al-4V. The effects of stress ratios R(=σ_<min>/σ_<max>) on fatigue properties and initial crack propagation processes on interior-originating fractures were investigated. As a result, the following were obtained : (1) S-N curves under R<0 showed a steep incline in a long life region where interior-originating fractures occurred although those under R<0 revealed a gentle slope in a whole life. (2) Multiple cracks initiated from plane facets were observed on the fracture surface under R<0,however those multiple facets could not be found under R<0. The result of (1) was probably explained by the idea that positive stress rations facilitated the initiations of many small cracks and the linkage of those cracks.
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Tatsuo SAKAI, Yousuke SATO, Yoshiyuki NAGANO, Mitsuhiro TAKEDA, Noriya ...
Article type: Article
Pages
175-176
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Effect of stress ratio on fatigue properties of a bearing steel including long life region was experimentally examined under axial loading. As a result, the complicated S-N property was well explained as duplex S-N characteristics obtained by superposition of S-N curves for surface induced fracture and interior inclusion induced fracture irrespective of stress ratio. Fish-eye marks were necessarily observed on the fracture surfaces failed in the latter fracture mode and an inclusion was found at the center of the fish-eye. It was finally found that the fatigue fracture of this steel in the long life region occurred through three different processes of (1) formation of the characteristic area of FGA, (2) crack propagation to form the fish-eye and (3) rapid crack propagation to cause the catastrophic fracture.
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Kenji OKADA, Machiko Furuichi, Tatsuo Sakai
Article type: Article
Pages
177-178
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Ultar-long life fatigue properties of SCM435 steel were experimentally examined in rotating bending. High cycle fatigue data of the same kind of steel were extracted from the DATABASE ON FATIGUE STRENGTH OF METALLIC MATERIALS published by JSMS. These results were put altogether and the statistical fatigue properties of this steel were analyzed as duplex P-S-N characteristics.
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Motohiro YAMASHITA, Yoshihiro OOTAO, Yoshinobu TANIGAWA
Article type: Article
Pages
179-180
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This study is concerned with the theoretical treatment of transient thermal stress problem involving functionally graded cylindrical panel under heated and cooled processes. We obtain the approximate solution for two-dimensional temperature change in a transient state, and thermal stress of simple supported cylindrical panel under the state of plane strain. As an example, numerical calculations are carried out for a functionally graded material of aluminum alloy/alumina, and the behaviors are examined from the initial state of heating to the steady state of the cooled process.
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Takuya MORIMOTO, Yoshinobu TANIGAWA
Article type: Article
Pages
181-182
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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The thermal buckling problem for simply supported inhomogeneous rectangular plates subjected to nonuniform heat supply is investigated for several kinds of in-plane boundary conditions. It is assumed that inhomogeneous material properties such as the coefficient of linear thermal expansion α, the thermal conductivity λ, and Young's modulus of elasticity E are changed in the thickness direction with the power law of the coordinate variable, while Poisson's ratio is assumed to be constant. Critical buckling loads are obtained by the 1-term approximated Galerkin method. Effects of the inhomogeneous material properties, aspect ratio and width-to-thickness ratio on critical buckling temperature are examined.
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Shouetsu ITOU
Article type: Article
Pages
183-184
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Axially symmetric thermal stresses in the vicinity of a finite cylindrical crack in an elastic pipe are calculated. The surface of the crack is assumed to be insulated. The outer surface of the pipe is heated so as to maintain a constant temperature T_d, and the inner surface of the pipe is cooled so as to maintain a constant temperature T_b. Stress intensity factors are defined and calculated numerically for several configurations of the pipe.
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Naotake NODA, Noriyuki YAMAMOTO, Masayuki ISHIHARA
Article type: Article
Pages
185-186
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper discusses crack propagation paths in a ceramic/metal functionally graded plate with two edge cracks under a transient temperature field. When the functionally graded plate is cooled from high temperature, curved or straight multiple cracks are observed on the ceramic surface. There are many types of crack propagation pattern. To investigate the mechanism of multi-crack initiation and crack propagation pattern, two crack paths are simulated using finite element method. The effect of the existence of a crack on propagation path of another crack are investigated and numerical results are shown in figures.
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Sompon TAEPRASARTSIT, Katsumi TAO, Shigeo TAKEZONO
Article type: Article
Pages
187-188
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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This paper is concerned with the numerical analysis of dynamic thermal stress and dynamic buckling of elastic shallow spherical shells made of functionally graded materials. The calculations for evaluating displacements and stresses are based on the conventional theory of elasticity that geometric nonlinearity is taken into account. A modified 8-noded quardrilateral finite element is utilized for the analysis.
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Yasuhiro MATSUNAGA
Article type: Article
Pages
189-190
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this study, the characterization of TiNi shape memory alloy coil springs is described. At first, the results of uniaxial tensile test for the TiNi wire and coil springs are described. By use of the kinetics model and the mixture theory of parallel type and series types, the stress distributions and load-displacement curves for TiNi coil springs are predicted analytically. The numerical calculations are performed by use of the material constants obtained by the previous tests. The both results, analytical and experimental results, are compared and discussed.
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Masayuki ISHIHARA, Naotake NODA
Article type: Article
Pages
191-192
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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Dynamic behavior of a piezoelastic symmetrical cross-ply rectangular laminate subjected to mechanical and electrical loads and simply-supported is investigated considering the effect of damping due to interlaminar shear. The behavior of the laminate is analyzed based on the first-order shear deformation theory. To incorporate the effect of damping due to interlaminar shear, the interlaminar shear stresses which satisfy the Newton's law of viscosity are introduced. Equations of motion in terms of deflection and rotations are derived and solved by the Laplace transform method. The transient deflection due to dynamical loads are obtained. The methods to control the deflection due to mechanical load by applying electrical voltage to the piezoelectric actuators are investigated by showing numerical calculations.
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Takashi TAMAKI, Naotake NODA, Masayuki ISHIHARA
Article type: Article
Pages
193-194
Published: August 05, 2003
Released on J-STAGE: August 01, 2017
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In this analysis, we deal with an unsteady problem of an edge crack in a semi-infinite, transversely isotropic, thermopiezoelastic material under heat loading and electric displacement by means of potential function method and Laplace transform method. The problem is reduced to a singular integral equation. The thermal stress intensity factor at the crack edge is obtained. The effect of the width of the temperature load on the thermal stress intensity factor is examined. From numerical calculations, it is found that the peak of thermal stress intensity factor is found in transient state and that application of electric displacement can control thermal stress intensity factor.
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