The Experts below are selected from a list of 4017 Experts worldwide ranked by ideXlab platform
Hisao Matsunaga - One of the best experts on this subject based on the ideXlab platform.
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dual roles of Pearlite Microstructure to interfere facilitate gaseous hydrogen assisted fatigue crack growth in plain carbon steels
International Journal of Fatigue, 2022Co-Authors: Yuhei Ogawa, Haruki Nishida, Masami Nakamura, Vigdis Olden, Alexey Vinogradov, Hisao MatsunagaAbstract:Abstract Fatigue crack growth of two carbon steels with different Pearlite volume fractions were studied in pressurized gaseous hydrogen environment. Notably, Pearlite was found to mitigate hydrogen-assisted fatigue crack acceleration. This positive impact of Pearlite was ascribed to ferrite/cementite lamellar aligned perpendicularly to the cracking direction, which functioned as barriers to intermittently arrest the crack propagation. Meanwhile, brittle delamination fracture ensued in the Pearlite lamellar lying parallel to the crack-plane increased the crack growth rate and compromised the above positive effect to some extent. The material behavior is rationalized in light of fractographical observations and microstructural analyses of the crack-wake.
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slow strain rate tensile and fatigue properties of cr mo and carbon steels in a 115 mpa hydrogen gas atmosphere
International Journal of Hydrogen Energy, 2015Co-Authors: Hisao Matsunaga, Michio Yoshikawa, Ryota Kondo, Junichiro Yamabe, Saburo MatsuokaAbstract:Abstract Slow strain rate tensile (SSRT) tests were performed using smooth specimens of two types of steels, the Cr–Mo steel, JIS-SCM435, which has a tempered, martensitic Microstructure, and the carbon steel, JIS-SM490B, which has a ferrite/Pearlite Microstructure. The tests were carried out in nitrogen gas and hydrogen gas, under a pressure of 115 MPa at three different temperatures: 233 K, room temperature and 393 K. In nitrogen gas, these steels exhibited the so-called cup-and-cone fracture at every temperature. In contrast, surface cracking led to a marked reduction in ductility in both steels in hydrogen gas. Nonetheless, even in hydrogen gas, JIS-SCM435 exhibited some reduction of area after the stress-displacement curve reached the tensile strength (TS), whereas JIS-SM490B demonstrated little, if any, necking in hydrogen gas. In addition, tension-compression fatigue testing at room temperature revealed that these steels show no noticeable degradation in fatigue strengths in hydrogen gas, especially in the relatively long-life regime. Considering that there was little or no hydrogen-induced degradation in either the TS or the fatigue strength in JIS-SCM435, it is suggested that the JIS-SCM435 is eligible for safety factor-based fatigue limit design for hydrogen service under pressures up to 115 MPa.
Tetsuya Ohashi - One of the best experts on this subject based on the ideXlab platform.
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Strain-hardening characteristics of ferrite layers in Pearlite Microstructure
Materials Science and Technology, 2017Co-Authors: Yohei Yasuda, Tetsuya Ohashi, Tomotsugu Shimokawa, Tomoaki NiiyamaAbstract:Strain hardening of ferrite layers in Pearlite Microstructures plays a crucial role in the stability of elasto-plastic deformation of Pearlite. The effects of layer thickness, crystal orientation r...
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elasto plastic deformation of colony boundaries in Pearlite Microstructure by finite element analyses
Applied Mechanics and Materials, 2015Co-Authors: Lidyana Roslan, Tetsuya Ohashi, Yohei Yasuda, Chikara SurugaAbstract:Elasto-plastic tensile deformations in multi-colony structures are studied by finite element analyses to investigate how the deformation in multi-colony structures influence the strain concentration around colony boundary. The results obtained from plastic strain distributions show that plastic strain concentrates around colony boundary when there is a large difference of deformation between adjacent colonies and around the point where boundaries of differently aligned colonies meet.
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keynote evaluation of the mechanical property of ferrite lamellar in Pearlite Microstructure
The 5th International Conference on Computational Methods (ICCM2014), 2014Co-Authors: Tetsuya Ohashi, Yohei YasudaAbstract:Pearlite Microstructure in steels consists of lamellae of ferrite and cementite and their thicknesses are at an order of sub-micrometers. Single-phase specimen of cementite is known to be brittle, while the flow stress level of ferrite at R.T. with a specimen size larger than millimeter is of an order of few hundred MPa and elongation is larger than 20%. Strong yet ductile property of Pearlite steels is considered to originate from the combination of these phases with largely different mechanical characteristics. One requisite property for the higher plastic flow stress level of the Pearlite is the increase of the flow stress in ferrite, while the ductility of Pearlite is realized when the cementite phase could deform into plastic range. We recently tried to understand this phenomenon with a hypothesis that ferrite lamella sandwiched by cementite lamellae showed higher yield strength and strain hardening. The results were that cementite lamellae could deform well beyond the elastic range when the yield stress and strain hardening of ferrite layers were high enough. In this communication, we use crystal plasticity finite element method to analyze slip deformation in ferrite lamella sandwiched by cementite layers. Densities of statistically stored and geometrically necessary dislocations are obtained and these quantities are utilized to evaluate mechanical response of ferrite layers with various thicknesses. Obtained results show notable increases in the yield stress as well as strain-hardening ratio of the ferrite layers when the layer thickness decreases.
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a multiscale approach for the deformation mechanism in Pearlite Microstructure atomistic study of the role of the heterointerface on ductility
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Tomotsugu Shimokawa, Masaki Tanaka, Kenji Higashida, Takuma Oguro, Tetsuya OhashiAbstract:Abstract The role of the ferrite/cementite heterointerface on the mechanical properties of heavily-drawn-pearlitic steel is investigated via tensile deformation tests of multilayered composite models with brittle and ductile virtual materials in a two-dimensional triangle-lattice system by using molecular dynamics simulations. The interface strength is controlled by introducing a heterointerface potential. The dominant role of heterointerface on the mechanical properties of multilayered composite models is influenced by the interface strength. In case of weak interface strength, the heterointerface acts as a strong barrier to dislocation motion in the ductile phase; hence, the multilayered composite model shows high strength but extremely low ductility. This tendency corresponds well to that of as-drawn pearlitic steel with cementite decomposition. In case of strong interface strength, the heterointerface acts as a dislocation source of the brittle phase by dislocation transmission through the heterointerface from the ductile to brittle phase; hence, the multilayered composite model shows good ductility with a small decrease in strength. This tendency corresponds well to annealed pearlitic steel recovered from cementite decomposition. These results suggest that cementite decomposition decreases the plastic deformation potential of the heterointerface. The conditions necessary for the heterointerface to simultaneously exhibit high strength and ductility are discussed on the basis of the results of atomic simulations.
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a multiscale approach for the deformation mechanism in Pearlite Microstructure experimental measurements of strain distribution using a novel technique of precision markers
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014Co-Authors: Masaki Tanaka, Tomotsugu Shimokawa, Kenji Higashida, Yusuke Yoshimi, Tetsuya OhashiAbstract:Abstract Plastic deformation of fully pearlitic steels was investigated using a multiscale approach: experimentally, the finite element method and molecular dynamics. This paper is the first in a series of three papers demonstrating the strain distribution in uniaxial tensile deformation with high-precision markers drawn by electron beam lithography. Strain was measured at loads of 1.98 kN, 2.21 kN and 2.28 kN in tensile deformation. Scanning electron microscopy (SEM) images and strain maps show the plastic deformation of cementite lamellae and homogenous plastic deformation under uniaxial tensile deformation in the area where the cementite lamellae are aligned in the tensile direction. The areas where strain was enhanced were both block/colony boundaries and the areas where the cementite lamellae are inclined approximately 45° to the tensile direction.
Chris San Marchi - One of the best experts on this subject based on the ideXlab platform.
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effects of Microstructure banding on hydrogen assisted fatigue crack growth in x65 pipeline steels
International Journal of Fatigue, 2016Co-Authors: Joseph Allen Ronevich, Brian P Somerday, Chris San MarchiAbstract:Abstract Banded ferrite–Pearlite X65 pipeline steel was tested in high pressure hydrogen gas to evaluate the effects of oriented Pearlite on hydrogen assisted fatigue crack growth. Test specimens were oriented in the steel pipe such that cracks propagated either parallel or perpendicular to the banded Pearlite. The ferrite–Pearlite Microstructure exhibited orientation dependent behavior in which fatigue crack growth rates were significantly lower for cracks oriented perpendicular to the banded Pearlite compared to cracks oriented parallel to the bands. The reduction of hydrogen assisted fatigue crack growth across the banded Pearlite is attributed to a combination of crack-tip branching and impeded hydrogen diffusion across the banded Pearlite.
Teruki Sadasue - One of the best experts on this subject based on the ideXlab platform.
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effects of Pearlite morphology and specimen thickness on fatigue crack growth resistance in ferritic pearlitic steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Akhmad A Korda, Yukio Miyashita, Yoshiharu Mutoh, Teruki SadasueAbstract:Abstract Effect of Pearlite morphology and specimen thickness on fatigue crack growth (FCG) behavior in ferritic–pearlitic structural steels was investigated. Two steels with different Pearlite morphologies were employed: one had islands of Pearlite colonies and the other had uniformly distributed Pearlite particles. Δ K -decreasing/increasing FCG test was carried out by using a standard compact tension (CT) specimen with 6 mm thickness and a single edge cracked plate tension (SECT) specimen with 1.5 mm thickness. The results revealed that the uniformly distributed Pearlite Microstructure had a FCG resistance higher than the islands of Pearlite colonies Microstructure. To understand the effect of Pearlite morphology on crack growth behavior in the Paris regime in detail, constant-Δ K FCG tests with in situ SEM observation were also carried out. From in situ observations, tortuous crack path was found in the uniformly distributed Pearlite Microstructure. These tortuous crack paths with large crack deflection angle would promote crack closure as well as crack tip stress shielding and then resulted in higher crack growth resistance. Thin specimen indicated lower FCG rate compared to thick specimen, which resulted from the difference of crack closure behavior.
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in situ observation of fatigue crack retardation in banded ferrite Pearlite Microstructure due to crack branching
Scripta Materialia, 2006Co-Authors: Akhmad A Korda, Teruki Sadasue, Yukio Miyashita, Yoshiharu Mutoh, S L MannanAbstract:This paper reports the results of in situ observation of fatigue crack growth in a ferrite–Pearlite steel. Stress intensity factor range (ΔK) decreasing/increasing and constant-ΔK fatigue tests have been carried out. In banded Pearlite orientation, intense crack branching was observed which leads to fatigue crack retardation. Crack closure during the test was monitored to understand the fatigue crack growth behaviour.
Akhmad A Korda - One of the best experts on this subject based on the ideXlab platform.
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effects of Pearlite morphology and specimen thickness on fatigue crack growth resistance in ferritic pearlitic steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Akhmad A Korda, Yukio Miyashita, Yoshiharu Mutoh, Teruki SadasueAbstract:Abstract Effect of Pearlite morphology and specimen thickness on fatigue crack growth (FCG) behavior in ferritic–pearlitic structural steels was investigated. Two steels with different Pearlite morphologies were employed: one had islands of Pearlite colonies and the other had uniformly distributed Pearlite particles. Δ K -decreasing/increasing FCG test was carried out by using a standard compact tension (CT) specimen with 6 mm thickness and a single edge cracked plate tension (SECT) specimen with 1.5 mm thickness. The results revealed that the uniformly distributed Pearlite Microstructure had a FCG resistance higher than the islands of Pearlite colonies Microstructure. To understand the effect of Pearlite morphology on crack growth behavior in the Paris regime in detail, constant-Δ K FCG tests with in situ SEM observation were also carried out. From in situ observations, tortuous crack path was found in the uniformly distributed Pearlite Microstructure. These tortuous crack paths with large crack deflection angle would promote crack closure as well as crack tip stress shielding and then resulted in higher crack growth resistance. Thin specimen indicated lower FCG rate compared to thick specimen, which resulted from the difference of crack closure behavior.
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in situ observation of fatigue crack retardation in banded ferrite Pearlite Microstructure due to crack branching
Scripta Materialia, 2006Co-Authors: Akhmad A Korda, Teruki Sadasue, Yukio Miyashita, Yoshiharu Mutoh, S L MannanAbstract:This paper reports the results of in situ observation of fatigue crack growth in a ferrite–Pearlite steel. Stress intensity factor range (ΔK) decreasing/increasing and constant-ΔK fatigue tests have been carried out. In banded Pearlite orientation, intense crack branching was observed which leads to fatigue crack retardation. Crack closure during the test was monitored to understand the fatigue crack growth behaviour.