The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Shigeru Asano - One of the best experts on this subject based on the ideXlab platform.
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Strain Amplitude dependent anelasticity in cu ni solid solution due to thermally activated and athermal dislocation point obstacle interactions
Journal of Applied Physics, 1999Co-Authors: S. B. Kustov, Yoichi Nishino, Gérard Gremaud, W. Benoit, S. Golyandin, K. V. Sapozhnikov, Shigeru AsanoAbstract:Experimental investigations of the internal friction and the Young’s modulus defect in single crystals of Cu-(1.3–7.6) at. % Ni have been performed for 7–300 K over a wide range of oscillatory Strain Amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ∼1 kHz. The Strain Amplitude dependence of the anelastic Strain Amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the Strain Amplitude dependence of the internal friction and the Young’s modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low Strain Amplitudes (∼10−7–10−5), the Amplitude-dependent internal friction and the Young’s modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. ...
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Strain Amplitude-dependent anelasticity in Cu–Ni solid solution due to thermally activated and athermal dislocation–point obstacle interactions
Journal of Applied Physics, 1999Co-Authors: S. B. Kustov, Yoichi Nishino, Gérard Gremaud, W. Benoit, S. Golyandin, K. V. Sapozhnikov, Shigeru AsanoAbstract:Experimental investigations of the internal friction and the Young’s modulus defect in single crystals of Cu-(1.3–7.6) at. % Ni have been performed for 7–300 K over a wide range of oscillatory Strain Amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ∼1 kHz. The Strain Amplitude dependence of the anelastic Strain Amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the Strain Amplitude dependence of the internal friction and the Young’s modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low Strain Amplitudes (∼10−7–10−5), the Amplitude-dependent internal friction and the Young’s modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. ...
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Analysis of Strain-Amplitude-dependent internal friction in thin-layer materials
Philosophical Magazine A, 1995Co-Authors: Yoichi Nishino, K. Tanahashi, Shigeru AsanoAbstract:Abstract Internal friction in aluminium thin films on a silicon substrate has been measured as a function of Strain Amplitude by means of a free-decay method of flexural vibration. Procedures for analysing the Strain Amplitude dependence of internal friction in thin-layer materials are presented, firstly for evaluating the internal friction in the film separately from the measured damping of the composite system, and secondly for converting the internal friction in the film into the plastic Strain as a function of effective stress on dislocations. The stress-Strain responses thus obtained for the aluminium films show that plastic Strain of the order of 1019 increases nonlinearly with increasing stress. The microflow stress at a constant level of plastic Strain is inversely proportional to the film thickness, which agrees with the variation in the macroscopic yield strengths.
Paulo Roberto Cetlin - One of the best experts on this subject based on the ideXlab platform.
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Mechanical behavior and microstructures of aluminum processed by low Strain Amplitude multi-directional confined forging
Journal of Materials Research and Technology, 2020Co-Authors: Natanael Geraldo Silva Almeida, Pedro Henrique R. Pereira, C.g. De Faria, Maria Teresa Paulino Aguilar, Paulo Roberto CetlinAbstract:Abstract Severe Plastic Deformation (SPD) leads to grain refinement and strengthening of metals. Among the many SPD processing methods, Multi-Directional Forging (MDF) is the only one where in-situ material stress–Strain curves can be obtained. These are adequate only for specimens re-machined after each compression step, thus avoiding problems connected to specimen shape distortions; re-machining involves complex, expensive and time consuming procedures. This difficulty has been circumvented using confined plane Strain compressions, where the Strain path, however, differs from that in simple, unconfined free compression. A new processing method involving, for each processing step, an initial free simple compression followed by a confined compression (Multi-Directional Confined Forging – MDCF) is proposed, eliminating the specimen re-machining. Strengthening by MDF depends on Strain Amplitude; low Strain Amplitude MDF (LSA-MDF) leads to lower work hardening of the material than high Strain Amplitude MDF, as well as to limited softening and to an increase in the residual work hardening capacity of material previously deformed monotonically or in successive deformation steps with high Strain Amplitudes. This supplies a highly desired enhanced uniform elongation of the material after SPD. It is shown that Low Strain Amplitude Multi-Directional Confined Forging (LSA-MDCF) of aluminum leads to adequate stress–Strain curves up to the contact of the specimen with the confining die walls, as well as to microstructures very similar to those obtained using free compressions with re-machined specimens. This processing route is simpler, faster and cheaper than LSA-MDF with re-machined samples, and thus emerges as a more practical MDF route.
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Microstructural evolution and mechanical behavior of copper processed by low Strain Amplitude multi-directional forging
Materials Science and Engineering: A, 2019Co-Authors: Paula Cibely Alves Flausino, Pedro Henrique R. Pereira, Maria Teresa Paulino Aguilar, Maria Elisa Landim Nassif, Franco De Castro Bubani, Paulo Roberto CetlinAbstract:Abstract Experiments were performed to analyze the microstructural evolution and mechanical behavior of commercial-purity copper (99.8%) processed by up to 48 cycles of multi-directional forging (MDF) using a low Strain Amplitude of ∼0.075 (total accumulated Strain e ≈ 10.8). Parabolic work-hardening concomitantly with increasing dislocation densities was observed up to e ≈ 2, followed by a practically constant flow stress due to dynamic recovery. The average grain size was reduced from 30.5 μm in the annealed metal down to 4.1 μm for e ≈ 7.2; the fraction of sub-micrometric grains reached ∼12% for e ≈ 10.8. The microstructural changes were attributed to the fragmentation of the original grains by dislocation structures having low misorientation angles which gradually evolved into arrays of high-angle grain boundaries with increasing numbers of MDF cycles. The Cu samples subjected to 48 cycles of MDF displayed limited dynamic recrystallization, exhibiting basically dislocation cells and sub-grains with an average size of ∼0.6 μm. It is demonstrated that low Strain Amplitude MDF delays the kinetics of grain refinement in copper compared with MDF using higher Strain Amplitudes.
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microstructural evolution in the low Strain Amplitude multi axial compression lsa mac after equal channel equal pressing ecap of aluminum
Materials Letters, 2018Co-Authors: Cleber Granato De Faria, Natanael Geraldo Silva Almeida, Maria Teresa Paulino Aguilar, Franco De Castro Bubani, K Balzuweit, Paulo Roberto CetlinAbstract:Abstract Low Strain Amplitude multi-axial compression (LSA-MAC) increases the work hardening capacity and uniform ductility of Aluminum after Severe Plastic Deformation (SPD) through Equal Channel Angular Pressing (ECAP). The mechanisms associated with this processing after ECAP are analyzed. LSA-MAC after 1 ECAP pass in Aluminum softens the material and is connected to the stabilization of the dislocation structures induced by ECAP into a configuration displaying an increased fraction of High Angle Grain Boundaries (HAGB). This occurs for a lower total imposed Strain than that through a sequence of high Strain ECAP passes or high Strain Amplitude multi-axial compression (HAS-MAC).
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EFFECT OF THE CYCLIC Strain Amplitude ON THE HOT DYNAMIC RESTORATION OF COPPER
Scripta Materialia, 2001Co-Authors: I.p. Pinheiro, Ronaldo Barbosa, Paulo Roberto CetlinAbstract:Federal University of MinasGerais, Department of Metallurgical and Materials Engineering, Rua Espi´rito Santo 35, s206,Centro, 30160-030, Belo Horizonte, Minas Gerais, Brazil(Received May 18, 2000)(Accepted in revised form July 20, 2000)Keywords: Dynamic phenomena; Recrystallization and recovery; Copper; Hot cyclic StrainingIntroductionThe microstructures developed during hot and warm working of metals are profoundly affected byvariables such as the prevailing temperatures, Strain rates and Strains [1,2]. Another variable that hasbeen receiving attention is the Strain path [3,4], with special emphasis on cyclic and multiaxial Straining.This can be of particular importance in the industrial rolling of flat and long products. For both cases,there is a cyclic superficial shearing associated to the change of direction of the friction shear stressesas the material traverses the rolling gap [5]. For long products, there is also a 45° or 90° change in thecompression direction from one rolling pass to the next one. The situation is particularly relevant to thefinishing stands of wire rod mills, where interpass times are very low [6] and softening between passesis probably not important.Cyclic cold Straining of metals leads to lower work hardening rates than monotonic deformation. Thedegree of hardening decreases as the Strain Amplitude is lowered [7]. It has also been shown [3] that theflow stress of copper in hot cyclic torsion is substantially lower than under monotonic torsion. Theeffect of Strain Amplitude was the same as for cold working, and the dynamic recrystallization peak waseliminated. These facts are illustrated in Figure 1.The effects of hot cyclic Straining depend on the Strain Amplitude (De) in the cycle. The availabledata for copper at 500°C and a Strain rate of 0.1s
Yanyao Jiang - One of the best experts on this subject based on the ideXlab platform.
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electron backscatter diffraction observations of twinning detwinning evolution in a magnesium alloy subjected to large Strain Amplitude cyclic loading
Materials & Design, 2015Co-Authors: Shuai Dong, Yanyao Jiang, Jie Dong, Fenghua Wang, Wenjiang DingAbstract:Abstract An extruded ZK60 magnesium alloy was subjected to fully-reversed Strain-controlled cyclic loading at a Strain Amplitude of 4.0% in the extrusion direction in ambient air. Electron backscatter diffraction (EBSD) analyses were conducted on samples taken from companion specimens terminated at different loading cycles to study the twinning–detwinning process and the evolution of the twin structures at different stages of cyclic deformation. It is observed that the twin nucleation sites are increased whereas twin growth/shrinkage is inhibited due to repeated twinning–detwinning. The enhanced twin nucleation sites are responsible for the observed increase in the number of twin lamellae and the increased twin volume fraction with loading cycles. Cyclic loading enhances formation of compression and double twins which do not result in immediate fracture of the material. With increasing number of loading cycles, more and larger sized residual tension twin lamellae can be detected by EBSD, but the total volume fraction of the residual twins is trivial.
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effect of Strain Amplitude on tension compression fatigue behavior of extruded mg6al1zna magnesium alloy
Scripta Materialia, 2010Co-Authors: Jixi Zhang, Yanyao JiangAbstract:Fully reversed Strain-controlled tension–compression fatigue experiments were conducted on extruded Mg6Al1ZnA (AZ61A) magnesium alloy by employing thin-walled tubular specimens in ambient air. The Strain–life fatigue curve displayed a detectable transition from lower cycle fatigue region to higher cycle fatigue region in the vicinity corresponding to a Strain Amplitude of 0.5%. When the Strain Amplitude was higher than 0.5%, shear cracking and significant twinning were observed. When the Strain Amplitude was lower than 0.5%, tensile cracking and little twinning were observed.
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Effect of Strain Amplitude on tension–compression fatigue behavior of extruded Mg6Al1ZnA magnesium alloy
Scripta Materialia, 2010Co-Authors: Jixi Zhang, Yanyao JiangAbstract:Fully reversed Strain-controlled tension–compression fatigue experiments were conducted on extruded Mg6Al1ZnA (AZ61A) magnesium alloy by employing thin-walled tubular specimens in ambient air. The Strain–life fatigue curve displayed a detectable transition from lower cycle fatigue region to higher cycle fatigue region in the vicinity corresponding to a Strain Amplitude of 0.5%. When the Strain Amplitude was higher than 0.5%, shear cracking and significant twinning were observed. When the Strain Amplitude was lower than 0.5%, tensile cracking and little twinning were observed.
S. B. Kustov - One of the best experts on this subject based on the ideXlab platform.
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Strain Amplitude dependent anelasticity in cu ni solid solution due to thermally activated and athermal dislocation point obstacle interactions
Journal of Applied Physics, 1999Co-Authors: S. B. Kustov, Yoichi Nishino, Gérard Gremaud, W. Benoit, S. Golyandin, K. V. Sapozhnikov, Shigeru AsanoAbstract:Experimental investigations of the internal friction and the Young’s modulus defect in single crystals of Cu-(1.3–7.6) at. % Ni have been performed for 7–300 K over a wide range of oscillatory Strain Amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ∼1 kHz. The Strain Amplitude dependence of the anelastic Strain Amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the Strain Amplitude dependence of the internal friction and the Young’s modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low Strain Amplitudes (∼10−7–10−5), the Amplitude-dependent internal friction and the Young’s modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. ...
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Strain Amplitude-dependent anelasticity in Cu–Ni solid solution due to thermally activated and athermal dislocation–point obstacle interactions
Journal of Applied Physics, 1999Co-Authors: S. B. Kustov, Yoichi Nishino, Gérard Gremaud, W. Benoit, S. Golyandin, K. V. Sapozhnikov, Shigeru AsanoAbstract:Experimental investigations of the internal friction and the Young’s modulus defect in single crystals of Cu-(1.3–7.6) at. % Ni have been performed for 7–300 K over a wide range of oscillatory Strain Amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ∼1 kHz. The Strain Amplitude dependence of the anelastic Strain Amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the Strain Amplitude dependence of the internal friction and the Young’s modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low Strain Amplitudes (∼10−7–10−5), the Amplitude-dependent internal friction and the Young’s modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. ...
Yoichi Nishino - One of the best experts on this subject based on the ideXlab platform.
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Strain Amplitude dependent anelasticity in cu ni solid solution due to thermally activated and athermal dislocation point obstacle interactions
Journal of Applied Physics, 1999Co-Authors: S. B. Kustov, Yoichi Nishino, Gérard Gremaud, W. Benoit, S. Golyandin, K. V. Sapozhnikov, Shigeru AsanoAbstract:Experimental investigations of the internal friction and the Young’s modulus defect in single crystals of Cu-(1.3–7.6) at. % Ni have been performed for 7–300 K over a wide range of oscillatory Strain Amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ∼1 kHz. The Strain Amplitude dependence of the anelastic Strain Amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the Strain Amplitude dependence of the internal friction and the Young’s modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low Strain Amplitudes (∼10−7–10−5), the Amplitude-dependent internal friction and the Young’s modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. ...
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Strain Amplitude-dependent anelasticity in Cu–Ni solid solution due to thermally activated and athermal dislocation–point obstacle interactions
Journal of Applied Physics, 1999Co-Authors: S. B. Kustov, Yoichi Nishino, Gérard Gremaud, W. Benoit, S. Golyandin, K. V. Sapozhnikov, Shigeru AsanoAbstract:Experimental investigations of the internal friction and the Young’s modulus defect in single crystals of Cu-(1.3–7.6) at. % Ni have been performed for 7–300 K over a wide range of oscillatory Strain Amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ∼1 kHz. The Strain Amplitude dependence of the anelastic Strain Amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the Strain Amplitude dependence of the internal friction and the Young’s modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low Strain Amplitudes (∼10−7–10−5), the Amplitude-dependent internal friction and the Young’s modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. ...
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Analysis of Strain-Amplitude-dependent internal friction in thin-layer materials
Philosophical Magazine A, 1995Co-Authors: Yoichi Nishino, K. Tanahashi, Shigeru AsanoAbstract:Abstract Internal friction in aluminium thin films on a silicon substrate has been measured as a function of Strain Amplitude by means of a free-decay method of flexural vibration. Procedures for analysing the Strain Amplitude dependence of internal friction in thin-layer materials are presented, firstly for evaluating the internal friction in the film separately from the measured damping of the composite system, and secondly for converting the internal friction in the film into the plastic Strain as a function of effective stress on dislocations. The stress-Strain responses thus obtained for the aluminium films show that plastic Strain of the order of 1019 increases nonlinearly with increasing stress. The microflow stress at a constant level of plastic Strain is inversely proportional to the film thickness, which agrees with the variation in the macroscopic yield strengths.
