The Experts below are selected from a list of 100374 Experts worldwide ranked by ideXlab platform
Terence G Langdon - One of the best experts on this subject based on the ideXlab platform.
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using Finite Element Modeling to examine the temperature distribution in quasi constrained high pressure torsion
Acta Materialia, 2012Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G Langdon, Pedro Henrique R Pereira, Maria Teresa Paulino AguilarAbstract:Abstract Processing by quasi-constrained high-pressure torsion (HPT) is important for achieving substantial grain refinement in bulk solids, but very little information is available at present on the rise in temperature that occurs in the HPT specimens during the processing operation. This problem was addressed by using Finite Element Modeling with an analytical component to evaluate the thermal characteristics in quasi-constrained HPT. The analysis incorporates the effects of various parameters, including the material strength, the rotation rate, the applied pressure and the volume of the anvils. The calculations show that the temperature rise varies directly with the material strength and the rotation rate, but depends only slightly on the applied pressure. Using this analysis, a normalized master curve is constructed that may be used to predict the rise in temperature during HPT processing. It is demonstrated that the predictions from this curve are in good agreement with experimental data for three different materials.
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using Finite Element Modeling to examine the flow processes in quasi constrained high pressure torsion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G LangdonAbstract:Abstract Finite Element Modeling was used to examine the flow processes in high-pressure torsion (HPT) when using quasi-constrained conditions where disks are contained within depressions on the inner surfaces of the upper and lower anvils. Separate simulations were performed using applied pressures from 0.5 to 2.0 GPa, rotations up to 1.5 turns and friction coefficients from 0 to 1.0 outside of the depressions. The simulations demonstrate the distribution of effective strain within the depressions is comparable to the prediction by ideal torsion, and the applied pressure and the friction coefficient outside the depressions play only a minor role in the distribution of effective strain. The mean stresses during processing vary linearly with the distance from the center of the disk such that there are higher compressive stresses in the disk centers and lower stresses at the edges. The torque required for rotation of the anvil is strongly dependent upon the friction coefficient between the sample and the anvil outside the depressions.
Roberto B Figueiredo - One of the best experts on this subject based on the ideXlab platform.
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using Finite Element Modeling to examine the temperature distribution in quasi constrained high pressure torsion
Acta Materialia, 2012Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G Langdon, Pedro Henrique R Pereira, Maria Teresa Paulino AguilarAbstract:Abstract Processing by quasi-constrained high-pressure torsion (HPT) is important for achieving substantial grain refinement in bulk solids, but very little information is available at present on the rise in temperature that occurs in the HPT specimens during the processing operation. This problem was addressed by using Finite Element Modeling with an analytical component to evaluate the thermal characteristics in quasi-constrained HPT. The analysis incorporates the effects of various parameters, including the material strength, the rotation rate, the applied pressure and the volume of the anvils. The calculations show that the temperature rise varies directly with the material strength and the rotation rate, but depends only slightly on the applied pressure. Using this analysis, a normalized master curve is constructed that may be used to predict the rise in temperature during HPT processing. It is demonstrated that the predictions from this curve are in good agreement with experimental data for three different materials.
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using Finite Element Modeling to examine the flow processes in quasi constrained high pressure torsion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G LangdonAbstract:Abstract Finite Element Modeling was used to examine the flow processes in high-pressure torsion (HPT) when using quasi-constrained conditions where disks are contained within depressions on the inner surfaces of the upper and lower anvils. Separate simulations were performed using applied pressures from 0.5 to 2.0 GPa, rotations up to 1.5 turns and friction coefficients from 0 to 1.0 outside of the depressions. The simulations demonstrate the distribution of effective strain within the depressions is comparable to the prediction by ideal torsion, and the applied pressure and the friction coefficient outside the depressions play only a minor role in the distribution of effective strain. The mean stresses during processing vary linearly with the distance from the center of the disk such that there are higher compressive stresses in the disk centers and lower stresses at the edges. The torque required for rotation of the anvil is strongly dependent upon the friction coefficient between the sample and the anvil outside the depressions.
Paulo Roberto Cetlin - One of the best experts on this subject based on the ideXlab platform.
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using Finite Element Modeling to examine the temperature distribution in quasi constrained high pressure torsion
Acta Materialia, 2012Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G Langdon, Pedro Henrique R Pereira, Maria Teresa Paulino AguilarAbstract:Abstract Processing by quasi-constrained high-pressure torsion (HPT) is important for achieving substantial grain refinement in bulk solids, but very little information is available at present on the rise in temperature that occurs in the HPT specimens during the processing operation. This problem was addressed by using Finite Element Modeling with an analytical component to evaluate the thermal characteristics in quasi-constrained HPT. The analysis incorporates the effects of various parameters, including the material strength, the rotation rate, the applied pressure and the volume of the anvils. The calculations show that the temperature rise varies directly with the material strength and the rotation rate, but depends only slightly on the applied pressure. Using this analysis, a normalized master curve is constructed that may be used to predict the rise in temperature during HPT processing. It is demonstrated that the predictions from this curve are in good agreement with experimental data for three different materials.
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using Finite Element Modeling to examine the flow processes in quasi constrained high pressure torsion
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Roberto B Figueiredo, Paulo Roberto Cetlin, Terence G LangdonAbstract:Abstract Finite Element Modeling was used to examine the flow processes in high-pressure torsion (HPT) when using quasi-constrained conditions where disks are contained within depressions on the inner surfaces of the upper and lower anvils. Separate simulations were performed using applied pressures from 0.5 to 2.0 GPa, rotations up to 1.5 turns and friction coefficients from 0 to 1.0 outside of the depressions. The simulations demonstrate the distribution of effective strain within the depressions is comparable to the prediction by ideal torsion, and the applied pressure and the friction coefficient outside the depressions play only a minor role in the distribution of effective strain. The mean stresses during processing vary linearly with the distance from the center of the disk such that there are higher compressive stresses in the disk centers and lower stresses at the edges. The torque required for rotation of the anvil is strongly dependent upon the friction coefficient between the sample and the anvil outside the depressions.
Tony M Keaveny - One of the best experts on this subject based on the ideXlab platform.
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Finite Element Modeling of the human thoracolumbar spine
Spine, 2003Co-Authors: Michael A K Liebschner, David L Kopperdahl, William S Rosenberg, Tony M KeavenyAbstract:Study design Biomechanical properties within cadaveric vertebral bodies were parametrically studied using Finite Element analysis after calibration to experimental data. Objectives To develop and validate three-dimensional Finite Element models of the human thoracolumbar spine based on quantitative computed tomography scans. Specifically, combine Finite Element Modeling together with biomechanical testing circumventing problems associated with direct measurements of shell properties. Summary of background data Finite Element methods can help to understand injury mechanisms and stress distribution patterns within vertebral bodies as an important part in clinical evaluation of spinal injuries. Because of complications in Modeling the vertebral shell, it is not clear if quantitative computed tomography-based Finite Element models of the spine could accurately predict biomechanical properties. Methods We developed a novel Finite Element Modeling technique based on quantitative computed tomography scans of 19 radiographically normal human vertebra bodies and mechanical property data from empirical studies on cylindrical trabecular bone specimens. Structural properties of the vertebral shell were recognized as parametric variables and were calibrated to provide agreement in whole vertebral body stiffness between model and experiment. The mean value of the shell properties thus obtained was used in all models to provide predictions of whole vertebral strength and stiffness. Results Calibration of n = 19 computer models to experimental stiffness yielded a mean effective modulus of the vertebral shell of 457 +/- 931 MPa ranging from 9 to 3216 MPa. No significant correlation was found between vertebral shell effective modulus and either the experimentally measured stiffness or the average trabecular modulus. Using the effective vertebral shell modulus for all 19 models, the predicted vertebral body stiffness was an excellent predictor of experimental measurements of both stiffness (r2= 0.81) and strength (r2 = 0.79). Conclusion These findings indicate that Modeling of the vertebral shell using a constant thickness of 0.35 mm and an effective modulus of 457 MPa, combined with quantitative computed tomography-based Modeling of trabecular properties and vertebral geometry, can accurately predict whole vertebral biomechanical properties. Use of this Modeling technique, therefore, should produce substantial insight into vertebral body biomechanical behavior and may ultimately improve clinical indications of fracture risk of this cohort.
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Finite Element Modeling of the human thoracolumbar spine
Spine, 2003Co-Authors: Michael A K Liebschner, David L Kopperdahl, William S Rosenberg, Tony M KeavenyAbstract:Study Design. Biomechanical properties within cadaveric vertebral bodies were parametrically studied using Finite Element analysis after calibration to experimental data. Objectives. To develop and validate three-dimensional Finite Element models of the human theracolumbar spine based on quantitative computed tomography scans. Specifically, combine Finite Element Modeling together with in vitro biomechanical testing circumventing problems associated with direct measurements of shell properties. of Background Data. Finite Element methods can help to understand injury mechanisms and stress distribution patterns within vertebral bodies as an important part in clinical evaluation of spinal injuries. Because of complications in Modeling the vertebral shell, it is not clear if quantitative computed tomography-based Finite Element models of the spine could accurately predict biomechanical properties. Methods. We developed a novel Finite Element Modeling technique based on quantitative computed tomography scans of 19 radiographically normal human vertebra bodies and mechanical property data from empirical studies on cylindrical trabecuiar bone specimens. Structural properties of the vertebral shell were recognized as parametric variables and were calibrated to provide agreement in whole vertebral body stiffness between model and experiment. The mean value of the shell properties thus obtained was used in all models to provide predictions of whole vertebral strength and stiffness. Results. Calibration of n = 19 computer models to experimental stiffness yielded a mean effective modulus of the vertebral shell of 457 ± 931 MPa ranging from 9 to 3216 MPa. No significant correlations was found between vertebral shell effective modulus and either the experimentally measured stiffness or the average trabecuiar modulus. Using the effective vertebral shell modulus for all 19 models, the predicted vertebral body stiffness was an excellent predictor of experimental measurements of both stiffness (r 2 = 0.81) and strength (r 2 = 0.79). Conclusion. These findings indicate that Modeling of the vertebra shell using a constant thickness of 0.35 mm and an effective modulus of.457 MPa, combined with quantitative computed tomography-based Modeling of trabecular properties and vertebral geometry, can accurately predict whole vertebral biomechanical properties. Use of this Modeling technique, therefore, should produce substantial insight into vertebral body biomechanical behavior and may ultimately improve clinical indications of fracture risk of this cohort.
Y W Zhang - One of the best experts on this subject based on the ideXlab platform.
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Controlling of residual stress in additive manufacturing of Ti6Al4V by Finite Element Modeling
Additive Manufacturing, 2016Co-Authors: Guglielmo Vastola, Qing Xiang Pei, G Zhang, Y W ZhangAbstract:Minimizing the residual stress build-up in metal-based additive manufacturing plays a pivotal role in selecting a particular material and technique for making an industrial part. In beam-based additive manufacturing, although a great deal of effort has been made to minimize the residual stresses, it is still elusive how to do so by simply optimizing the manufacturing parameters, such as beam size, beam power, and scan speed. With reference to the Ti6Al4V alloy and manufacturing by electron beam melting, we perform systematic Finite Element Modeling of one-pass scanning to study the effects of beam size, beam power density, beam scan speed, and chamber bed temperature on the magnitude and distribution of residual stresses. Our study elucidates both qualitative and quantitative features of the residual stress fields originated by these manufacturing parameters. Our findings can serve as useful guidelines for engineers and designers to deal with residual stress build-up during additive manufacturing of Ti6Al4V.
