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Shigetaka OKANO, Daisuke KANAMARU, Masahito MOCHIZUKI
Session ID: OS09-10
Published: 2016
Released on J-STAGE: June 19, 2017
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In this study, semi-nondestructive and simultaneous measurement of distributions of residual stress and plastic strain within surface layer of materials were developed through instrumented indentation technique. The developed technique was applied to estimate the depth-directional distributions of residual stress and plastic strain within waterjet peened layer of nickel-based alloy. The estimated results were compared with those obtained through the X-ray diffraction method and the Vickers hardness test. From the results, we concluded that the developed procedure using instrumented indentation technique was expected to be useful.
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Kiminobu HOJO
Session ID: OS09-11
Published: 2016
Released on J-STAGE: June 19, 2017
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A revision of flaw evaluation of cast stainless steel pipe of JSME rules on fitness for service is planned. The points are to apply the limit load method to unaged or low SC pipe, introduce prediction models for S-S and J-R curve due to thermal aging embrittlement and revised Z-factor equations proposed by other authors. To confirm the applicability of the degradation model and the current and proposed Z-factors of JSME rules, EPFM analysis was performed and Z-factor was directly deduced from the analysis. Input conditions were provided at the ASME Section XI meeting. Directly deduced Z-factors were compared with those of JSME rules and ASME Section XI. It is revealed that the draft prediction models of JSME has good accuracy, Z-factors of JSME have a very large conservativeness, and those of ASME Section XI have proper values.
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(Comparison between US and Japanese Code and Future Issues)
Koichi KASHIMA
Session ID: OS09-12
Published: 2016
Released on J-STAGE: June 19, 2017
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Allowable crack is one of the most important concepts to maintain the structural integrity of nuclear power plant components and it is introduced in the Fitness-For-Service codes in US and Japan. This paper shows the comparison of ASME Code Section XI on the allowable crack for nuclear piping with JSME code and also presents some new proposals, including future issues.
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Shotaro HAYASHI, Mayumi OCHI, Kiminobu HOJO, Wataru NISHI
Session ID: OS09-13
Published: 2016
Released on J-STAGE: June 19, 2017
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The allowable flaw sizes of cast austenitic stainless steel(CASS) pipes were determined by probabilistic fracture mechanics (PFM) analysis code “PREFACE”, in a similar way as the technical basis of ASME Section XI Code Case N-838(CC-N-838) to set the target sizes of performance demonstration certification of nondestructive testing. In order to confirm the validity of PREFACE, the allowable flaw sizes calculated by PREFACE were compared with those in the technical basis of CC-N-838. As a result, although J calculation method and the embrittlement prediction model of CASS are different, these allowable flaw sizes were qualitatively consistent.
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Naoki MIURA
Session ID: OS09-14
Published: 2016
Released on J-STAGE: June 19, 2017
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The flaw evaluation methods for Classes 2 and 3 components have been provided in JSME fitness-for-service rule for nuclear power plants. Articles EC-2000 and ED-3000 in the code prescribe the acceptance standards for Classes 2 and 3 components, respectively. For austenitic stainless steel, the acceptance standards for Classes 2 and 3 piping is the same as those for Class 1 piping since the fracture toughness is assumed adequately high. In contrast, Classes 2 and 3 Ferritic piping has wide range of fracture toughness, therefore, specific acceptance standards are prepared in consideration of the level of fracture toughness. In this paper, a case study to configure allowable flaw sizes for Classes 2 and 3 with realistic material properties was conducted. The margins of the allowable flaws against failure were also examined.
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Hideo MACHIDA
Session ID: OS09-15
Published: 2016
Released on J-STAGE: June 19, 2017
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In the manufacturing process of piping, radiographic testing (RT) for weld joints is carried out. However, RT is poor in detection of the planar flaws compared with ultrasonic testing (UT) used in in-service inspection, there is a possibility of overlooking of planar flaws in the weld joints. Then, assuming the initial embedded flaw in the weld joints, growth of it during plant operation life was evaluated. Since the cause of growth is limited to fatigue for embedded flaws and the growth rate of them is lower than in water environment, flaws hardly grow during plant operation life, and the reduction of fracture strength of a pipe by embedded flaws is negligible. Therefore, the weld joints whose integrity was confirmed by the weld testing and the pressure test will not break throughout the plant life even if there are initial embedded flaws in the weld joints.
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Masaki NAGAI, Lu KAI, Masayuki KAMAYA
Session ID: OS09-16
Published: 2016
Released on J-STAGE: June 19, 2017
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In nuclear power plants, some cracks attributed to stress corrosion cracking (SCC) have been detected in welds made with nickel alloy weld metals. One of the characteristics of these cracks is that crack aspect ratio a/ℓ is greater than 0.5, where a is the crack depth and ℓ is the crack length. When a crack is detected in components of nuclear power plants during in-service inspection, flaw evaluation is conducted according to the requirement of codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants. Here, the stress intensity factor plays an important role for predicting crack growth behavior due to fatigue and/or SCC. Although several solutions of the stress intensity factor are already given in the JSME code, no solutions are available for the cracks with a/ℓ > 0.5. According to the current code, surface cracks with a/ℓ > 0.5 are characterized as semi-circular shape ℓ = 2a. To evaluate these cracks in a rational manner, several solutions have been proposed for cracks with a/ℓ > 0.5. In this paper, comprehensive comparison was made between solutions for cracks a/ℓ > 0.5, and benchmark analysis on SCC crack growth was performed.
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Fuminori IWAMATSU, Koichi SAITO, Shinji YOSHIDA, Shunsuke TAKAGI
Session ID: OS09-17
Published: 2016
Released on J-STAGE: June 19, 2017
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An applicability of flaw characterization rules provided by codes, such as JSME fitness-for-service code, to ductile fracture of non-aligned multiple flaws remains an issue of structural integrity evaluation. Hence, this paper deals with investigating evaluation of collapse load of a pipe with non-aligned flaws subjected to bending moment by experiments and analytical approach. Through-wall non-aligned flaws were introduced to 4-inch pipes made of austenitic stainless steel by electric discharge machining. 4-point bending tests of the pipe were conducted to observe collapse behavior and obtain load-displacement relationships. Flaw interactions depending on distances between two flaws were observed from the test results. Finite element models on the basis of the test conditions were generated and elasto-plastic analysis considering non-linear geometry were conducted. Twice elastic slope method was applied to the analysis results to estimate collapse loads. The estimated collapse loads can represent tendency of the test results and derive conservative results.
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Fuminori IWAMATSU, Koichi SAITO, Shinji YOSHIDA, Shunsuke TAKAGI
Session ID: OS09-18
Published: 2016
Released on J-STAGE: June 19, 2017
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Fracture tests of a flat plate were conducted to develop assessment methodology of ductile fracture of non-aligned flaws. Although JSME fitness-for-service code provides flaw characterization rules for multiple flaws, it seems to be determined based on the linear fracture mechanics. Thus, the development of the assessment methodology for a component with non-aligned flaws made of high toughness materials remains an issue of structural integrity. Hence, this paper deals with development of the assessment methodology of non-aligned flaws on the basis of experimental results. Through-wall non-aligned flaws were introduced to flat plates made of austenitic stainless steel by electric discharge machining. Tensile tests of the flat plate were conducted to observe collapse behavior and obtain load-displacement relationships. The previous and present experimental results revealed the flaw lengths and a distance between flawed cross sections are representative parameters of the ductile fracture. The evaluation results using the representative parameters corresponded with the experimental results and the assessment procedure was proposed in this paper.
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Hideo MACHIDA, Manabu ARAKAWA, Takashi WAKAI, Kenichiro SATOH
Session ID: OS09-19
Published: 2016
Released on J-STAGE: June 19, 2017
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Since the piping of fast reactor is used at low internal pressure and its material has high ductility, LBB is easily satisfied in general. Especially when the internal pressure is low and thermal expansion reaction force is small, both crack driving force and fracture load are small, then it is easily imagined that LBB might be easily satisfied. However, the crack opening displacement and leak rate dynamically evaluated are small in such conditions. For this reason, the contradiction occurs that LBB evaluation is not satisfied despite the crack driving force and the fracture load are small. To eliminate such inconsistencies, screening rules to determine the necessity of a detailed LBB evaluation were proposed. According to the rules, the detailed LBB evaluation can be omitted for the cases of low internal pressure and small thermal expansion load as the fracture of pipes do not occur. Based on the piping design of the constructed fast reactor plant, the applicability of the proposed screening rules was examined.
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(Part.2:Influence of internal pressure)
Manabu ARAKAWA, Hideo MACHIDA, Toyohiko SATOMURA
Session ID: OS09-20
Published: 2016
Released on J-STAGE: June 19, 2017
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Based on previous studies, only prevention of the fatigue damage was required as permission for the S class piping in the service condition Ds, and the primary stress limit for the purpose of the prevention of the plastic collapse was actually abolished in the JEAC4601-2008. In this study, the necessity of the stress limit for plastic collapse due to seismic load was examined.
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Yohei ONO, Takuya OGAWA, Takahiro HAYASHI, Toshiyuki SAITO
Session ID: OS09-21
Published: 2016
Released on J-STAGE: June 19, 2017
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Nuclear reactor structures subject to neutron irradiation could have internal distribution of materials properties such as strength and toughness, depending on neutron flux attenuation from near side to far side of the materials surface relative to the core. In order to examine the effect of distribution of materials properties on the structural integrity, it is necessary to prepare a test specimen having distribution of materials properties. In this study, it has been demonstrated in mechanical properties tests that distribution of the strength and toughness due to neutron irradiation can be simulated by applying the graded level of cold working ratio with the plate material having a thickness gradient.
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Kai LU, Jinya KATSUYAMA, Yinsheng LI
Session ID: OS09-22
Published: 2016
Released on J-STAGE: June 19, 2017
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When conducting structural integrity assessments for reactor pressure vessels (RPVs) subjected to pressurized thermal shock (PTS) events, the stress intensity factor (SIF) is evaluated for a postulated crack near the inner surface of RPVs. If the underclad crack is postulated, it is known that the cladding made of a stainless steel has a relatively lower yield stress, the plasticity effect of cladding should be considered in SIF calculations. In the previous study, the authors proposed a plasticity correction method on SIFs for underclad cracks based on three-dimensional finite element analyses for Japanese three-loop RPVs using un-irradiated material properties. In this paper, further studies were conducted to investigate the applicability of the proposed plasticity correction method. The effect of hardening due to neutron irradiation was considered. In addition, different Japanese RPV geometries such as two-loop and four-loop RPVs were also investigated.
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Kazuma Hirosaka, Hidekazu Takazawa, Katsumasa Miyazaki, Norihide Tohya ...
Session ID: OS09-23
Published: 2016
Released on J-STAGE: June 19, 2017
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A reinforced concrete model for impact simulation of a missile is studied. This concrete model is a hybrid model of solid elements and SPH (smooth particle hydrodynamics) elements, and solid elements turn into the SPH elements when the compressive strain 0.01 is satisfied. The residual speed of missile after perforation among simulation results is compared with, predicted results by empirical formula and test results which conducted in CRIEPI in 1990s, and it is shown that the simulation results are in good agreement with the test results rather than the predicted results by the formulae. This model can be used for an impact simulation of concrete structure with single or multiple walls in nuclear power plants.
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Hayato YAMASHITA, Koichi SATO, Shin-ichi KOMAZAKI
Session ID: OS10-01
Published: 2016
Released on J-STAGE: June 19, 2017
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For the clarification of the creep damage detection mechanism by hydrogen, the simulation technique for investigating the effect of creep void on hydrogen thermal desorption characteristics of pure iron has been developed. The dissolved hydrogen was calculated by a kinetics calculation in consideration of trapping and dissociation of hydrogen in voids. In the interaction between hydrogen atoms and voids, the effect of dissociation and adsorption, recombination of hydrogen at the void surface was also taken into account. In addition, hydrogen diffusion inside of samples was calculated according to the diffusion equation. The void number density was used as an input parameter of the simulation. The hydrogen evolution curve obtained from the simulation did not accord with the experimental one. The latter might include the hydrogen desorption from the damages which were too small to be observed by a scanning electron microscope.
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Shogo FUKUDA, Ken-ichi KOBAYASHI
Session ID: OS10-02
Published: 2016
Released on J-STAGE: June 19, 2017
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Small Punch (SP) Creep test has been recognized as a practical procedure to examine creep lives only sampling a very small volume. The SP creep test enables assessment of local points that conventional uniaxial creep test cannot evaluate. In order to assess the applicability of cumulative damage rule using the time fraction rule, a series of SP creep tests were carried out in air at 700°C employing ferritic stainless steel. Experimental test results show that the time fraction rule could be applied for the residual life of slighter pre-damaged specimens. However it would overestimate the severely damaged specimens.
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Ryota KANEKO, Daisuke ITO, Ken-ichi KOBAYASHI, Hideo KOYAMA
Session ID: OS10-03
Published: 2016
Released on J-STAGE: June 19, 2017
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In order to ensure integrity of equipments working under high temperature, simple and convenient creep tests are required. Miniature Creep (MC) test is one of uniaxial creep tests using small size specimen. It can evaluate creep properties of thin or small parts, e.g., turbine blade and HAZ. In this study, using MC tests, authors examined creep characteristics of an aged boiler tube (STBA20) that had been used for nearly 60,000 hours. Creep life of virgin STBA20 material was estimated using Time-Temperature Parameter (TTP) methods, i.e., Larson-Millar and Manson-Hafard parameter methods. Then, there was little difference of creep life between aged and virgin materials, and it was also shown that aged boiler tube would be rarely damaged ; it has almost the same strength of virgin material.
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Tomohisa KUMAGAI, Masatsugu YAGUCHI, Koji TAMURA
Session ID: OS10-04
Published: 2016
Released on J-STAGE: June 19, 2017
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A method to estimate time to creep rupture of repaired welded joints was developed. In the method, repaired weld was divided into several elements. Time to rupture of the each element depended on Rmat, θfs and α, which were ratio for each typical materials formed in repaired weld , angle between fusion line and applied load, and ratio of the each material occupied in the cross section to evaluate. The rupture time of the whole repaired weld was calculated by using the elemental rupture time based on Norton's law. The creep rupture time of almost cross-weld test pieces from repaired weld could be estimated by the developed method. Further, the estimated time to rupture of large test pieces containing repaired weld showed agreement with the experimental values.
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Haruhisa SHIGEYAMA, Yukio TAKAHASHI, Jonathan PARKER
Session ID: OS10-05
Published: 2016
Released on J-STAGE: June 19, 2017
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Creep tests on two kinds of circumferentially notched round bar specimens as well as plain bar specimen of ASME grade 92 steels were performed to obtain the multiaxial and uniaxial creep data. Then creep damage models according to strain fraction rule and energy fraction rule were developed based on the results of these uniaxial and multiaxial creep tests. Additionally, creep damage analyses using a finite element software, MSC Marc, were carried out on notched specimens and creep failure lives were predicted using the classical time fraction rule, as well as the two approaches developed here. Experimental failure lives of all the conditions of notched specimens were compared with analytical results. As a result, creep failure lives obtained by time fraction rule with von Mises equivalent stress were underestimated in the short term region and overestimated in the long term region. On the other hands, the majority of creep failure lives obtained by strain and energy fraction rule showed an agreement within a factor of two with experimental lives.
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Go OZEKI, A. Toshimitsu YOKOBORI, Jr.
Session ID: OS10-06
Published: 2016
Released on J-STAGE: June 19, 2017
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Directionally solidified Ni-base superalloy is used for gas turbine blades for high efficiency thermal power plant. There are many studies using a smooth specimens for directionally solidified Ni-base superalloy. However, these are not so many researches which concern the mechanical behavior of a notched specimen. From the view point of application to actual components, it is important to conduct the research for a notched specimen. And, directionally solidified Ni-base superalloy has large crystal grain. Therefore, crack growth behavior and crack growth life are considered to be affected by crystal orientation around the crack. However, effect of crystal orientation on crack growth life caused by inhomogeneous of grain distribution has not been clarified. In this study, by conducting mechanical analysis using the designed 2-dimensional elastic-plastic creep finite element analysis, scattering behavior of creep crack growth life and effect of pre-damage on creep crack growth behavior for directionally solidified Ni-base superalloy was analyzed.
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Yoshihisa KANEKO, Itsuki TADA, Makoto UCHIDA, Alexei VINOGRADOV
Session ID: OS11-01
Published: 2016
Released on J-STAGE: June 19, 2017
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Cyclic softening behavior of ultrafine-grained (UFG) nickels was investigated in low-cycle fatigue test. Pure nickel samples were severely deformed by equal channel angular pressing (ECAP) technique to obtain UFG microstructure. In the present study, the maximum number of the ECAP pass was eight. After the ECAP processes, average grain size of the 8-pass sample was refined down to 330nm. The ECAPed samples were shaped to small strip specimens for low-cycle fatigue test. The low-cycle fatigue tests were conducted under a constant plastic strain amplitude, in air at room temperature. During the low-cycle fatigue tests, stress amplitude continuously decreased in all the ECAPed samples, although stress amplitude of an as-annealed sample was almost unchanged. Amount of such cyclic softening depended on the number of ECAP pass and ECAP route: the samples processed by 8-pass ECAP revealed moderated cyclic softening.
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Chie EMURA, Toshiyuki KONDO, Hiroyuki HIRAKATA, Kohji MINOSHIMA
Session ID: OS11-02
Published: 2016
Released on J-STAGE: June 19, 2017
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An in-situ FESEM fatigue crack initiation experiment of a 760-nm-thick freestanding single crystalline copper (Cu) film was conducted to clarify the intrinsic mechanisms of fatigue crack initiation excluding the effect of microstructure such as twin boundaries. An hourglass-shaped film specimen with a single-side-edge notch was prepared. The specimen had (001) surface and [110] loading direction. FESEM observations showed that slip lines were formed at the notch root in [110] direction perpendicular to the loading axis. Intrusions/extrusions were then formed along a single slip plane, or (111) plane, and a crack occurred along the slip plane.
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Toshiyuki KONDO, Akihiro SHIN, Masaya AKASAKA, Hiroyuki HIRAKATA, Kohj ...
Session ID: OS11-03
Published: 2016
Released on J-STAGE: June 19, 2017
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To investigate the effects of surface oxide layer on fatigue crack propagation properties, fatigue crack propagation experiments were conducted on approximately 500-nm-thick freestanding copper (Cu) films without surface oxide layer and compared with the properties of the films with roughly 1-nm-thick surface oxide layer. Just before the fatigue crack propagation experiment in a field emission scanning electron microscope (FESEM), surface oxide layer on one side of the specimen was etched by argon ion sputtering. In situ FESEM observations of fatigue crack propagation confirmed that intrusions/extrusions were formed ahead of the fatigue crack tip, and the fatigue crack then propagated preferentially through these intrusions/extrusions in the region of the stress intensity factor range ΔK ≲ 4 MPam1/2. In the region of ΔK ≳ 4 MPam1/2, the fatigue crack propagated in tensile fracture mode. These mechanisms of fatigue crack propagation were similar to that in the films with surface oxide layer. The relationships between fatigue crack propagation rate (da/dN) and ΔK showed no significant effects of surface oxide layer in ΔK ≲ 4MPam1/2.
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Chikara YONEDA, Yoshihisa KANEKO, Makoto UCHIDA
Session ID: OS11-04
Published: 2016
Released on J-STAGE: June 19, 2017
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Characteristics of microstructures that are developed under fatigue fracture surface have been investigated from both EBSD analysis along fracture surface and slip-band observation. A fatigue crack growth test was conducted in a center-cracked tension specimen of polycrystalline copper. After the crack growth test, specimen surface was first observed with a SEM to examine morphology of the slip bands emerged at grains adjoining to the fracture surface. Then, the observed grains were milled by a FIB to obtain tiny flat planes parallel to the fracture surface. The flat planes were analyzed with the EBSD system to estimate local lattice rotation. In the grains showing the slip bands of single slip, large lattice rotation was detected by the EBSD analysis. However, the lattice rotation was relatively suppressed in the grains showing multiple slips at the surface.
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Weitao YANG, Shigeaki KOBAYASHI, Sakae SAITO
Session ID: OS11-05
Published: 2016
Released on J-STAGE: June 19, 2017
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Roles of grain boundary microstructure in fatigue crack propagation in SUS430 ferritic stainless steel was investigated to obtain a clue to grain boundary engineering for control of high-cycle fatigue fracture in this alloy. The ratio of intergranular fatigue fracture to the overall fracture path became higher when the SUS430 specimen subjected to cyclic deformation at the condition of lower stress intensity factor range ΔK. Fatigue crack was mainly branched when the crack propagated along grain boundaries. The branching of intergranular fatigue crack occurred when the crack tip which propagated along random boundaries reached at triple junction composed of two low-∑ CSL boundaries. The possible grain boundary microstructure for control for fatigue crack propagation in SUS430 stainless steel was discussed on the basis of the obtained observation results.
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Shigeaki KOBAYASHI, Ryosuke KOBAYASHI
Session ID: OS11-06
Published: 2016
Released on J-STAGE: June 19, 2017
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Grain boundary degradation phenomena, such as sensitization and intergranular corrosion, result in embrittlement in austenitic stainless steel. The connectivity of random boundaries was evaluated by fractal analysis, because grain boundary degradation phenomena preferentially percolated along the random boundary network. SUS304 austenitic stainless steel specimens with different grain structure and grain boundary character distribution were produced by cold rolling and subsequent annealing. The fractal dimension of random boundary network with maximum connectivity (maximum random boundary connectivity, MRBC) in SU304 specimens were estimated ranging from 1.15 to 1.50. The fractal dimension of MRBC tended to increase with increasing length of MRBC. The SUS304 specimen with the lower fractal dimension of MRBC showed the higher corrosion resistance than the specimen with higher fractal dimension of MRBC, even if the specimens had the similar GBCD. The utility of grain boundary engineering for control of grain boundary degradation phenomena was proposed based on the obtained results.
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Masaki TANAKA, Hideya HASHIMOTO, Tatsuya MORIKAWA, Kenji HIGASHIDA
Session ID: OS11-07
Published: 2016
Released on J-STAGE: June 19, 2017
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Wire-drawn fully pearlitic steel was twisted at room temperature. A delamination crack was propagated along the longitudinal direction of the wire. Backscattered electron images indicate that the cementite lamellar beneath the delamination crack was vanished and fine grain structure was observed. It indicates that the delamination fracture is not brittle one but ductile shear one associated with severe plastic deformation.
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Kousuke SAWADA, Atsutomo NAKAMURA, Eita TOCHIGI, Kazuaki TOYOURA, Yuic ...
Session ID: OS11-08
Published: 2016
Released on J-STAGE: June 19, 2017
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A dislocation in a crystalline material has dangling bonds at its core and strong strain field in its vicinity. Therefore, it has a potential to exhibit peculiar physical properties and resolving atomic structure of boundary dislocations is considerable significance. In this study, we investigated atomic structure of boundary dislocations in magnesium oxide (MgO) by using scanning transmission electron microscopy (STEM). MgO is a typical ionic material that has sodium chloride type structure. In order to introduce dislocations in the crystal, we fabricated low-angle grain boundaries by a diffusion bonding technique. Owing to this method, we can arrange dislocations periodically in the crystal and observe dislocation structures easily. It was found that characteristic structures of dislocations.
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Bunpei YAMADA, Yoshihisa KANEKO, Makoto UCHIDA, Alexei VINOGRADOV
Session ID: OS11-09
Published: 2016
Released on J-STAGE: June 19, 2017
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SUS316L austenitic stainless steel which was processed by ECAP was annealed at various temperature ranging from 500°C to 800°C to remove dislocations and residual strain. After, the annealing, the sample was processed by second ECAP via Routes A or Bc. In TEM observation of microstructure, 2A and 2Bc samples which were via annealed at 600°C had the highest nano-twined volume. The maximum tensile strength was obtained by insertional annealing at 600°C,and exceeded the strength of the as-ECAPed sample. Uniform elongation was also improved by the insertional annealing, and was maximized at 700°C.Furthermore, we conducted secondary annealing at 600°C after the second ECAP. The secondary-annealed sample showed the uniform elongation which was two time higher than that before the annealing.
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Makoto UCHIDA, Takahiro ABE, Towa UENO, Yoshihisa KANEKO
Session ID: OS11-10
Published: 2016
Released on J-STAGE: June 19, 2017
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Evaluation of microscopic deformation behavior of polycrystalline metals is very important to predict the mechanical property of the material. In this study, a development of the microscopic deformation field of polycrystalline pure copper is evaluated by digital image correlation method. Then, slip deformation on each slip system is estimated from the in-plane components of strain tensor based on the concept of the crystalline plasticity theory. Experimental results clarified that microscopic nonuniform deformation in the crystalline grain were evaluated, and that slip deformation occurred on specific slip systems.
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Hitoshi Asano, Keita Suzuki, Makoto Uchida, Yoshihisa Kaneko
Session ID: OS11-11
Published: 2016
Released on J-STAGE: June 19, 2017
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The semi-crystalline polymer has complex hierarchical structure. The material composes a two-phase laminar composite structure consisting of the lamella is about several ten nm. During crystallization process, the lamella grows radially and makes a spherical shape structure called as spherulite. The distribution and size of spherulite are closely related to the mechanical property of the semi-crystalline polymer. Therefore, an evaluation of the deformation behavior of the spherulite-distributed microscopic structure is important to know the mechanical property of the material. In this study, effect of thermal history on the crystallization process on the microscopic structure and inelastic deformation behavior is evaluated. Uniaxial tensile tests were performed using PP films and plates with different spheulite structures under constant displacement rate. Distribution of spherulite and relationship between stress and strain were considerably changed by thermal history.
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Ryuto Oda, Kousuke TAKAHASHI, Kazuaki INABA, Kikuo KISHIMOTO, Shiori T ...
Session ID: OS11-12
Published: 2016
Released on J-STAGE: June 19, 2017
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Release energy of PSA (Pressure-Sensitive Adhesive) is strongly related to fibril formation, but it has not been characterized in detail because the measured adhesive force depends on the experiments conditions such as the separation rate and the layer thickness. In this study, the load-displacement relationship was obtained by AFM (Atomic Force Microscope) to investigate the fracture of single fibril. The maximum adhesive forces were measured by various release rates to examine the strain rate dependence of fibril separation. In addition, the test was repeated without cleaning the cantilever of AFM to clarify the remains of PSA on cantilever surface and to relate to separation mode. As a result it was found that separation occurs at the interface between cantilever and PSA surface at higher release rate, whereas PSA shows cohesive fracture at lower release rate.
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Takahiro MATSUO, Kosuke TAKAHASHI, Shuzo OSHIMA, Kazuaki INABA, Kikuo ...
Session ID: OS11-13
Published: 2016
Released on J-STAGE: June 19, 2017
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Structural interaction between solids and liquids is observed in various industrial fields such as wet-etching process in high aspect ratio pillars. Because a liquid bridge formed from a droplet between solid surfaces generates attraction force due to surface tension, it is necessary to quantitatively evaluate it for structural design. In this study, a pair of polymer plates fixed at one end with a small gap is submerged into liquid, so that capillary rise between the plates and plate deflection can be simultaneously observed. The experimental results of plate deflection are compared with analytical estimation obtained from an equation of motion for liquid column taking account of viscosity of liquid. This estimation corresponded well with the experimental results regardless of dimension of plate and submergence rate. In addition, the relationship between plate deflection and material constants is derived in a non-dimensional form. Therefore, plate deformation due to capillary attraction became predictable without experiments, only from dimension of plates and material constants.
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Byungwoon KIM, Takashi SUMIGAWA, Takayuki KITAMURA, Bongkyun JANG
Session ID: OS11-14
Published: 2016
Released on J-STAGE: June 19, 2017
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We investigate the fracture behavior of single crystal graphene using in-situ tensile test. Pristine graphene, which is generally single crystal is obtained by mechanical peeling method. For fracture testing, we introduce pre-crack with a focused ion beam. Before tensile test, we identify the geometry and crystal structure of the specimen using a scanning electron microscope (SEM) and a transmission electron microscope, and confirm the layer number of the specimen with Raman spectroscopy. The bilayer graphene specimen with center crack fabricated by a focused ion beam, is tensioned using in-situ tensile testing system under scanning electron microscope. From in-situ tensile test, we obtain load-displacement curve and continuous SEM images. The test results explain that the graphene specimen shows an unstable and brittle fracture behavior and that cracks propagate from tips of pre-crack.
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Takashi KAWAI, Toshiyuki KONDO, Hiroyuki HIRAKATA, Kohji MINOSHIMA
Session ID: OS11-15
Published: 2016
Released on J-STAGE: June 19, 2017
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In order to clarify the mechanical criterion of compound formation reaction of Ti/Si multilayered-nano-films, we conducted compressive experiments for micro-pillar specimens fabricated from the Ti/Si multilayer by focused ion beam (FIB). Compressive displacement in the stacking direction was applied to the specimen by a diamond spherical tip using a nano-indenter under in situ field emission scanning electron microscopy (FESEM) observation. In the experiments, some spherical particles appeared at the tip contact region and grew larger with increasing displacement. This suggested that compound formation reaction occurred and compound were formed. In addition, FESEM observation of FIBed cross-sections after the compression tests revealed that the Ti/Si multilayers disappeared at the high stress region. These results suggested the presence of a mechanical criterion of the compound formation reaction.
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Takahiro SHIMADA, Yasumitus ARAKI, Takayuki KITAMURA
Session ID: OS11-16
Published: 2016
Released on J-STAGE: June 19, 2017
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Atomically thin multiferroics with the coexistence and cross-coupling of ferroelectric and (anti-)ferromagnetic order parameters are promising for novel magnetoelectric nanodevices. However, such ferroic order disappears at a critical thickness in nanoscale. Here, we develop a new route to ultrathin multiferroics by engineering edge dislocation cores in nonmagnetic ferroelectric PbTiO3. We demonstrate from first principles that the nonstoichiometry intrinsic to the dislocation cores unexpectedly brings about magnetism with a localized spin moment around the core. This magnetism interacts with polarization directions through ferromagnetic-antiferromagnetic-nonmagnetic phase transitions, i.e., nonlinear magnetoelectric effect. This work therefore shows that the edge dislocations can act as an atomically thin multiferroics.
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Masataka Mori, Takahiro MATSUI, Takahiro SHIMADA, Takayuki KITAMURA
Session ID: OS11-17
Published: 2016
Released on J-STAGE: June 19, 2017
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Multiferroic properties of crystallographic shear (CS) plane in BiFeO3 are calculated using first-principles calculations. We find that the polarization and the magnetic moment are spontaneously rotated by 109 degrees through CS plane, while those in BiFeO3 bulk are uniform. The rotation of the polarization shows the transition involving its continuous rotation and discontinuous head-to-head type reversal, which is generally unstable in perfect crystal. These multiferroic properties are caused by edge-sharing of oxygen octahedra and localization of hole which emerges by nonstoichiometry of CS plane.
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Kairi MASUDA, Takahiro SHIMADA, Takayuki KITAMURA
Session ID: OS11-18
Published: 2016
Released on J-STAGE: June 19, 2017
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Ferroelectric behavior in strained SrTiO3 nano porous is investigated using phase-field simulations. We find, in the paraelectric nano-porous, the polarization vortex emerges around each pore due to strain concentration and forms a periodically arrayed ferroelectric nano region. The ferroelectric region expands and connects each other with increasing strain, and finally forms a ferroelectric network, which can be regarded as a nanostructure. Our finding provides a new strategy to tailor ferroelectric nano structure through mechanical load.
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Masaya UKITA, Atsutomo NAKAMURA, Katsuyuki MATSUNAGA
Session ID: OS11-19
Published: 2016
Released on J-STAGE: June 19, 2017
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Alkali halide crystals having the rock-salt crystal structure are generally brittle at low temperatures, but AgCl with the same structure is much more ductile than the other alkali halide crystals. Such a difference cannot be explained from a simple ionic picture of interatomic bonding, and thus should be closely related to the atomic structures at the dislocation cores. In this study, atomic structures and core energies of the two symmetric core configuration of edge dislocations for the slip system of {110}<110> in NaCl and AgCl were investigated in a first principles manner. The two symmetric atomic configurations were found to have almost equal dislocation core energies. It was found that the dislocation core structure in AgCl had lower core energy than that in NaCl, resulting from unique electronic structure at dislocation core in AgCl.
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Ken SUZUKI, Masaki KITAJO, Hideo MIURA
Session ID: OS11-20
Published: 2016
Released on J-STAGE: June 19, 2017
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Physical properties of electroplated copper thin film used for interconnection materials of devices have a wide distribution in the manufacturing process. In this study, effects of the microtexture of a seed layer on mechanical properties and crystallinity of an electroplated copper thin film were investigated. It was found that quality of the atomic arrangement and crystallographic orientation of the electroplated thin film changed drastically depending on the microtexture of a seed layer. As a result, hardness and Young’s modulus of the electroplated thin film varied from about 1.1 to 2.6 GPa and 115 to 150 GPa, respectively.
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Hiroyuki HIRAKATA, Ryota KOTOGE, Yuya MAEGAWA, Toshiyuki KONDO, Masayu ...
Session ID: OS11-21
Published: 2016
Released on J-STAGE: June 19, 2017
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To clarify the creep crack propagation mechanisms of Au submicron films, a creep crack propagation experiment is conducted for a 359-nm-thick Au freestanding film with a center notch under in situ FESEM observation. The notch root largely blunts and then a crack is initiated at the blunted notch root. A few voids nucleate ahead of the crack tip and the main crack propagates by coalescence of the crack and the voids. In the early stage where creep crack propagation rate is low, creep damage around the crack tip is confined to a small region less than 1-2 μm. In the later stage, creep damage spreads over a larger distance, resulting in the slower creep crack propagation rate.
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Kosuke SHIMBARA, Toshiyuki KONDO, Hiroyuki HIRAKATA, Kohji MINOSHIMA
Session ID: OS11-22
Published: 2016
Released on J-STAGE: June 19, 2017
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To clarify tensile creep properties of single crystalline gold (Au) submicron structures, tensile creep tests for ~0.5-μm- and ~1.5-μm-thick specimens were conducted under in-situ field emission scanning electron microscopy (FESEM) observation. The specimens having (100) surface and [010] loading direction were prepared by focused ion beam (FIB). Tensile tests were performed under a constant displacement rate. Stress fluctuated after yielding and ductile fracture occurred in both specimens. In creep tests, intermittent strain bursts were observed in both ~0.5-μm and ~1.5-μm specimens, suggesting a characteristic creep mechanism in submicron structures which is different from that of bulk counterpart.
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Kensuke YAMAMOTO, Satoshi NAKATA, Koji SUGANO, Yoshitada ISONO
Session ID: OS11-23
Published: 2016
Released on J-STAGE: June 19, 2017
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Although single crystal silicon (Si) is a brittle material at room temperature, three-dimensional creep forming of Si can be performed at a high temperature. The objective of this research is to propose a new process technique of 3D MEMS tactile sensor based on a combination of creep deformation forming and impurity diffusion processes. Since creep deformation and impurity diffusion processes of Si depend on the process time, stress and temperature, this research will find a rational process condition. As the first step of this research, we have clarified creep parameters of Norton's rule for Si thin films by a backward analysis using the finite element method and punch creep test at high temperature, which are required for a design and process simulation of Si-based 3D MEMS tactile sensor.
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Takashi SUMIGAWA, Shuhei TANAKA, Hiroki UNNO, Takayuki Kitamura
Session ID: OS11-24
Published: 2016
Released on J-STAGE: June 19, 2017
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In order to examine the size effect of a stress concentration region on fracture strength at the nanometer scale, fracture experiments were carried using silicon single crystal cantilever specimens with a notch. A crack was initiated along the (110) cleavage plane from the notch root. Finite element analyses pointed out that the fracture strength, which was evaluated by the normal stress at 1 nm from the notch root, gradually increased with decrease of the stress concentration region size and reached the ideal strength of the (110) cleavage plane of silicon.
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Kenya NAKAJIMA, Akihiro HATAYAMA, Susumu KUMAGAI, Akihito WATANABE, Fu ...
Session ID: OS12-01
Published: 2016
Released on J-STAGE: June 19, 2017
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This work deals with the mechanical property of triaxial CFRP from low to high temperatures. We performed tensile tests of this composite at 100 K, room temperature and 373 K. Mechanical load was applied along both the axial and transverse directions, and the effects of temperature and loading direction on the fracture load were discussed. We also fabricated the triaxial CFRP with barium titanate nanoparticles, and examined the damping properties at room temperature.
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Tomoaki SHIMPO, Satoshi KOBAYASHI, Ken GOTO, Minoru IWATA
Session ID: OS12-02
Published: 2016
Released on J-STAGE: June 19, 2017
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The purpose of this study is to evaluate cyclic thermal loading on microscopic damage progress and associated degradation of mechanical properties of CFRP which is used in antenna's radial ribs of new radio astronomy satellite. Thermal cycle test was conducted on the CFRP specimen and specimen was observed to characterize microscopic damages. Then, three point bending test were conducted to evaluate the bending modulus. Thermal stress analysis was also conducted to evaluate temperature gradient during thermal cycles. During thermal cycle tests, transverse crack occurred. On the other hand, bending modulus did not degrade.
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Shogo MATSUDA, Shijie ZHU, Arimitsu USUKI, Makoto KATO
Session ID: OS12-03
Published: 2016
Released on J-STAGE: June 19, 2017
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The thermal exposure tests are conducted to evaluate high temperature durability of nylon 6 clay hybrid nanocomposite (NCH). The degree of crystallinity is reduced by the thermal exposure at 120 °C and 150 °C, based on Differential Scanning Calorimetry (DSC) analysis. The tensile strength, elongation and fatigue strength are also decreased by the thermal exposure. The fracture origin is changed from the surface in as-received specimens to interior in the exposed specimens.
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Naoto NOGAWA, Masahiro ARAI, Keita GOTO, Takashi ISHIKAWA
Session ID: OS12-04
Published: 2016
Released on J-STAGE: June 19, 2017
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In the present paper, carbon fiber reinforced thermoplastic (CFRTP) were evaluated using a homogenization theory, based on the finite element method (FEM). Homogenization theory was employed to estimate the inelastic constitutive equation of the composite material by combining the constitutive equations of matrix and fiber respectively. Thermo-elasto-viscoplastic property of matrix was then evaluated by unidirectional tensile tests under several strain rates and temperatures. Thus, inelastic constitutive equation of composite can be estimated numerically by homogenization theory with FEM. It was shown that unidirectional CFRTP has in-plane anisotropy and shows nonlinear stress-strain relation depends on strain rates. In addition, it was also confirmed that elasto-viscoplastic constitutive equation of matrix has temperature dependency.
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Tsubasa OGAKI, Jin TOYOMURA, Tetsuya MATSUDA, Masahiro ARAI
Session ID: OS12-05
Published: 2016
Released on J-STAGE: June 19, 2017
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In this study, spring-in analysis of a L-shaped carbon fiber-reinforced plastic (CFRP) is performed in the macro- and micro-scales simultaneously. For this purpose, a thermoelastoviscoplasitc homogenization theory is constructed by introducing the effect of thermal expansion into the time-depended homogenization theory. Then, using this theory, thermoelastoviscoplastic two-scale analysis method considering finite deformation is established. Using the present method, spring-in behavior and thermal residual stress of a L-shaped CFRP are investigated.
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Yuya HASEGAWA, Kenichi SHIMIZU, Keisuke TANAKA
Session ID: OS12-06
Published: 2016
Released on J-STAGE: June 19, 2017
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The influence of plate thickness on the crack propagation behavior was studied with single edge-notched specimens which were cut from injection-molded plates (IMP) of short carbon-fiber reinforced polyphenylene sulfide(PPS) at two fiber angles relative to the molding flow direction (MFD), i. e. θ=0° (MD), 90°(TD) . The thickness of IMP was 1, 2 and 3mm. Specimens (SLP) made of only shell layer was also produced from IMP. IMP have three layer laminated structure where the fiber orientation in the shell layer was parallel to MFD and that of the core layer was nearly perpendicular to MFD. The fraction of the shell layer decreases with decreasing plate thickness. The macroscopic crack propagation path was perpendicular to the loading axis in MD and TD, showing mode I propagation. In the relation between crack propagation rate, da/dN, and stress intensity factor, ΔK, MD of SLP had the slowest rate and TD of SLP the fastest rate. For MD, the rate increases with increasing thickness, while for TD the opposite was true. The thickness dependence decreased when da/dN was correlated to the crack-tip-opening parameter, HΔG, where H is a compliance parameter and ΔG is the range of energy release rate. The fraction of shell layer determine the resistance of plates to fatigue crack propagation.
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