The Experts below are selected from a list of 12309 Experts worldwide ranked by ideXlab platform
Gu Ruijie - One of the best experts on this subject based on the ideXlab platform.
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role of Mandrel in nc precision bending process of thin walled tube
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Li Heng, Yang He, Sun Zhichao, Gu RuijieAbstract:Abstract The thin-walled tube NC bending process is a much complex physical process with multi-factors coupling interactive effects. The Mandrel is the key to improve bending limit and to achieve high quality. In this study, one analytical model of the Mandrel (including Mandrel shank and balls) has been established and some reference formulas have been deduced in order to select the Mandrel parameters preliminarily, i.e. Mandrel diameter d, Mandrel extension e, number of balls n, thickness of balls k, space length between balls p and nose radius r. The experiment has been carried out to verify the analytical model. Based on the above analysis, a 3D elastic–plastic FEM model of the NC bending process is established using the dynamic explicit FEM code ABAQUS/Explicit. Thus, the influences of Mandrel on stress distribution during the bending process have been investigated, and then the role of the Mandrel in the NC precision bending process such as wrinkling prevention has been revealed. The results show the following: (1) Wrinkling in the tube NC bending process is conditional on membrane biaxial compressive stress state; the smaller the difference between the biaxial membrane stresses is, the more possibility of wrinkling occurs. (2) If the Mandrels of larger sizes are used, it will cause the neutral axial to move outward and the difference between the in-plane compressive stresses to become more obvious, which may increase minimum wrinkling energy and anti-wrinkling ability. But the larger Mandrel sizes make outside tube over-thinning. (3) When the Mandrel extension length increases, the neutral axial will move outward and the difference between the biaxial compressive stresses becomes larger, but the significance is less than that of the Mandrel diameter. The excessive extension will cause tube to over thin or even crack. (4) The significance of ball number's effect on the neutral axial position and difference between biaxial compressive stresses is between ones of Mandrel diameter and Mandrel extension. Increasing the ball number will enhance the thinning degree and manufacturing cost. The results may help to better understanding of Mandrel role on the improvement of forming limit and forming quality in the process.
Heng Li - One of the best experts on this subject based on the ideXlab platform.
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comparison between the effects of pvc Mandrel and Mandrel cores die on the forming quality of bending rectangular h96 tube
International Journal of Mechanical Sciences, 2013Co-Authors: Heng Li, H YangAbstract:Abstract A new type of Mandrel, which is PVC material and supposed as elastic–plastic deformable part in the simulation, is proposed to use in rotary-draw bending process, due to it can fill the tube entirely. The effect of PVC Mandrel on the forming quality of rectangular H96 tube, such as tube damage distribution, wall thickness variation, section deformation, springback, is researched by comparing with the traditional Mandrel-cores die. It is found that, the maximum damage value obtained with PVC Mandrel is smaller than that with Mandrel-cores die. The PVC Mandrel leads to a smaller tube thickness variation and a more uniform tube thickness distribution compared with the Mandrel-cores, for the PVC Mandrel brings about smaller stress in the bending process. The PVC Mandrel is recommended to be used in the rotary-draw bending process due to its advantage in the prevention of height deformation, though, the constraint effect on the tube width provided by the PVC Mandrel is a little weaker than that by Mandrel-cores die. Especially, the PVC Mandrel with 1.5 times plastic hardening performs excellent well on the reduction of sectional height deformation of symmetrical line. The springback angle obtained with Mandrel-cores die is smaller due to the retracting Mandrel process. The PVC Mandrel should be taken away from the tube before the springback occurs, which can be realized by heating the Mandrel to soft.
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Comparison between the effects of PVC Mandrel and Mandrel-cores die on the forming quality of bending rectangular H96 tube
International Journal of Mechanical Sciences, 2013Co-Authors: Y. X. Zhu, Y.l. Liu, Heng Li, H.k. YangAbstract:A new type of Mandrel, which is PVC material and supposed as elastic-plastic deformable part in the simulation, is proposed to use in rotary-draw bending process, due to it can fill the tube entirely. The effect of PVC Mandrel on the forming quality of rectangular H96 tube, such as tube damage distribution, wall thickness variation, section deformation, springback, is researched by comparing with the traditional Mandrel-cores die. It is found that, the maximum damage value obtained with PVC Mandrel is smaller than that with Mandrel-cores die. The PVC Mandrel leads to a smaller tube thickness variation and a more uniform tube thickness distribution compared with the Mandrel-cores, for the PVC Mandrel brings about smaller stress in the bending process. The PVC Mandrel is recommended to be used in the rotary-draw bending process due to its advantage in the prevention of height deformation, though, the constraint effect on the tube width provided by the PVC Mandrel is a little weaker than that by Mandrel-cores die. Especially, the PVC Mandrel with 1.5 times plastic hardening performs excellent well on the reduction of sectional height deformation of symmetrical line. The springback angle obtained with Mandrel-cores die is smaller due to the retracting Mandrel process. The PVC Mandrel should be taken away from the tube before the springback occurs, which can be realized by heating the Mandrel to soft. ?? 2013 Elsevier Ltd.
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Springback law of thin-walled 6061-T4 Al-alloy tube upon bending
Transactions of Nonferrous Metals Society of China (English Edition), 2012Co-Authors: Heng Li, Kai Peng Shi, H.k. Yang, Yu Li TianAbstract:To achieve the precision bending deformation, the springback behaviors under various forming conditions should be clarified preliminarily. Taking the thin-walled 6061-T4 Al-alloy tube of 50.8 mm×0.889 mm (outer diameter×wall thickness) as the objective, the single-factor experimental analysis and the 3D-FE based numerical orthogonal test are conducted to address the effects of forming parameters on the springback behaviors in 6061-T4 Al-alloy tube bending. The results show that: 1) The springback angle increases linearly with increasing of the bending angle. 2) The significant factors from high to low are the clearance between tube and Mandrel, the bending radius, the friction between tube and pressure die, the clearance between tube and wiper die, the clearance between tube and pressure die, the coefficient of boost velocity, the friction between tube and Mandrel, the number of Mandrel balls. 3) The effect rules of significant parameters on springback of 6061-T4 Al-alloy tube are similar to those of stainless steel and Ti-alloy tubes. Springback becomes larger with increasing of the bending velocity, the tube-die clearance, the relative bending radius, the tube-pressure die friction and relative push assistant speed. While the springback decreases with increasing of the Mandrel extension length, the number of Mandrel balls and tube-Mandrel friction. © 2012 The Nonferrous Metals Society of China.
Li Heng - One of the best experts on this subject based on the ideXlab platform.
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role of Mandrel in nc precision bending process of thin walled tube
International Journal of Machine Tools & Manufacture, 2007Co-Authors: Li Heng, Yang He, Sun Zhichao, Gu RuijieAbstract:Abstract The thin-walled tube NC bending process is a much complex physical process with multi-factors coupling interactive effects. The Mandrel is the key to improve bending limit and to achieve high quality. In this study, one analytical model of the Mandrel (including Mandrel shank and balls) has been established and some reference formulas have been deduced in order to select the Mandrel parameters preliminarily, i.e. Mandrel diameter d, Mandrel extension e, number of balls n, thickness of balls k, space length between balls p and nose radius r. The experiment has been carried out to verify the analytical model. Based on the above analysis, a 3D elastic–plastic FEM model of the NC bending process is established using the dynamic explicit FEM code ABAQUS/Explicit. Thus, the influences of Mandrel on stress distribution during the bending process have been investigated, and then the role of the Mandrel in the NC precision bending process such as wrinkling prevention has been revealed. The results show the following: (1) Wrinkling in the tube NC bending process is conditional on membrane biaxial compressive stress state; the smaller the difference between the biaxial membrane stresses is, the more possibility of wrinkling occurs. (2) If the Mandrels of larger sizes are used, it will cause the neutral axial to move outward and the difference between the in-plane compressive stresses to become more obvious, which may increase minimum wrinkling energy and anti-wrinkling ability. But the larger Mandrel sizes make outside tube over-thinning. (3) When the Mandrel extension length increases, the neutral axial will move outward and the difference between the biaxial compressive stresses becomes larger, but the significance is less than that of the Mandrel diameter. The excessive extension will cause tube to over thin or even crack. (4) The significance of ball number's effect on the neutral axial position and difference between biaxial compressive stresses is between ones of Mandrel diameter and Mandrel extension. Increasing the ball number will enhance the thinning degree and manufacturing cost. The results may help to better understanding of Mandrel role on the improvement of forming limit and forming quality in the process.
H.k. Yang - One of the best experts on this subject based on the ideXlab platform.
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Comparison between the effects of PVC Mandrel and Mandrel-cores die on the forming quality of bending rectangular H96 tube
International Journal of Mechanical Sciences, 2013Co-Authors: Y. X. Zhu, Y.l. Liu, Heng Li, H.k. YangAbstract:A new type of Mandrel, which is PVC material and supposed as elastic-plastic deformable part in the simulation, is proposed to use in rotary-draw bending process, due to it can fill the tube entirely. The effect of PVC Mandrel on the forming quality of rectangular H96 tube, such as tube damage distribution, wall thickness variation, section deformation, springback, is researched by comparing with the traditional Mandrel-cores die. It is found that, the maximum damage value obtained with PVC Mandrel is smaller than that with Mandrel-cores die. The PVC Mandrel leads to a smaller tube thickness variation and a more uniform tube thickness distribution compared with the Mandrel-cores, for the PVC Mandrel brings about smaller stress in the bending process. The PVC Mandrel is recommended to be used in the rotary-draw bending process due to its advantage in the prevention of height deformation, though, the constraint effect on the tube width provided by the PVC Mandrel is a little weaker than that by Mandrel-cores die. Especially, the PVC Mandrel with 1.5 times plastic hardening performs excellent well on the reduction of sectional height deformation of symmetrical line. The springback angle obtained with Mandrel-cores die is smaller due to the retracting Mandrel process. The PVC Mandrel should be taken away from the tube before the springback occurs, which can be realized by heating the Mandrel to soft. ?? 2013 Elsevier Ltd.
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Springback law of thin-walled 6061-T4 Al-alloy tube upon bending
Transactions of Nonferrous Metals Society of China (English Edition), 2012Co-Authors: Heng Li, Kai Peng Shi, H.k. Yang, Yu Li TianAbstract:To achieve the precision bending deformation, the springback behaviors under various forming conditions should be clarified preliminarily. Taking the thin-walled 6061-T4 Al-alloy tube of 50.8 mm×0.889 mm (outer diameter×wall thickness) as the objective, the single-factor experimental analysis and the 3D-FE based numerical orthogonal test are conducted to address the effects of forming parameters on the springback behaviors in 6061-T4 Al-alloy tube bending. The results show that: 1) The springback angle increases linearly with increasing of the bending angle. 2) The significant factors from high to low are the clearance between tube and Mandrel, the bending radius, the friction between tube and pressure die, the clearance between tube and wiper die, the clearance between tube and pressure die, the coefficient of boost velocity, the friction between tube and Mandrel, the number of Mandrel balls. 3) The effect rules of significant parameters on springback of 6061-T4 Al-alloy tube are similar to those of stainless steel and Ti-alloy tubes. Springback becomes larger with increasing of the bending velocity, the tube-die clearance, the relative bending radius, the tube-pressure die friction and relative push assistant speed. While the springback decreases with increasing of the Mandrel extension length, the number of Mandrel balls and tube-Mandrel friction. © 2012 The Nonferrous Metals Society of China.
Robert Cook - One of the best experts on this subject based on the ideXlab platform.
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Stiffening of PαMS Mandrels During Curing
Fusion Technology, 2020Co-Authors: M Takagi, Robert Cook, Richard B. Stephens, Jane Gibson, Sally PaguioAbstract:AbstractPoly(α-methylstyrene) (PαMS) Mandrel precursors (a fluorobenzene solution of PαMS surrounding a water core) must be agitated to center the core. The initially fluid PαMS solution stiffens as the organic solvent is extracted, and it eventually becomes brittle; a collision with a stirring propeller will either dent or crack the surface. Dried Mandrels often exhibit dents on the surface or cracks in the wall that may result from such collisions. We have studied the deformation relaxation rate of Mandrel precursors as a function of curing time. We have found a point in the cure at which the core centering process has stopped but permanent denting has not started, and have found a simple test for this condition. We can use this information to produce highly spherical plastic Mandrels by controlling propeller speed as a function of time.
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progress in 2 mm glow discharge polymer Mandrel development for nif
Fusion Science and Technology, 2004Co-Authors: A Nikroo, Robert Cook, J Bousquet, B W Mcquillan, R R Paguio, M TakagiAbstract:All planned National Ignition Facility (NIF) capsule targets except machined beryllium require a glow discharge polymer (GDP) Mandrel upon which the ablator is applied. This Mandrel, {approx}2 mm in diameter, must at least meet if not exceed the symmetry and surface finish requirements of the final capsule. Such Mandrels are currently produced by the three-step depolymerizable Mandrel technique. The quality of the final Mandrel depends upon precise optimization and execution of each of the three steps. We had shown previously that fabrication of a Mandrel which met the symmetry and surface finish requirements was feasible using this technique. In this paper we will discuss recent progress towards converting this process into a high yield, production scale process.
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fabrication of polymer shells using a depolymerizable Mandrel
Fusion Technology, 1995Co-Authors: Stephan A. Letts, Evelyn Fearon, Leslie M. Allison, Steven R. Buckley, M. Saculla, Robert CookAbstract:AbstractA new technique for producing hollow shell laser fusion fuel capsules has been developed that starts with a depolymerizable Mandrel. In this technique we use poly(α-methylstyrene) (PAMS) beads or shells as Mandrels which are overcoated with plasma polymer. The PAMS Mandrel is thermally depolymerized to gas phase monomer, which diffuses through the permeable and thermally more stable plasma polymer coating, leaving a hollow shell. Using this technique we made shells from 200 µm to 4 mm diameter with 15 to 100 µm wall thickness having sphericity better than 0.5 µm and surface finish better than 10 nm RMS.
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Decomposable Mandrel Project. Progress report
1995Co-Authors: Stephan A. Letts, Evelyn Fearon, Leslie M. Allison, Steven R. Buckley, M. Saculla, Robert CookAbstract:We report on our progress in developing a new technology to produce both Nova and NIF scale capsules using a depolymerizable Mandrel. In this technique we use poly({alpha}-methylstyrene) (PAMS) beads or shells as Mandrels which are overcoated with plasma polymer. The poly({alpha}-methylstyrene) Mandrel is then thermally depolymerized to gas phase monomer which diffuses away through the more thermally stable plasma polymer coating, leaving a hollow shell. Since our last report we have concentrated on characterization of the final shell. Starting with PAMS bead Mandrels leads to distorted pyrolyzed shells because of thermally induced creep of the CH coating. We found that plasma polymer coatings on hollow shell Mandrels shrink isotropically during pyrolysis and maintain sphericity. We are now concentrating our efforts on the use of microencapsulated shells to prepare targets with buried diagnostic layers or inner wall surface texture.
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Production and characterization of doped Mandrels for inertial-confinement fusion experiments
Journal of Vacuum Science and Technology, 1994Co-Authors: Robert Cook, Steven R. Buckley, G.e. Overturf, Randall L. MceachernAbstract:A key feature of current inertial‐confinement fusion (ICF) experiments is the incorporation of dopant atoms into the thin polymer microshell which, in a finished ICF capsule, forms its inner wall. These dopants provide a spectroscopic signal during the implosion that can be used to diagnose the degree of mix at the capsule–fuel interface. The high‐Z dopants can also be used to directly image the fuel–pusher interface. The current status of doped Mandrel development is reviewed, with a focus on the Mandrel surface smoothness. With the development of unique surface mapping characterization tools which will be described, it has been discovered that Mandrel surface smoothness is a function of the polymers used to form the Mandrels. In this report it will be shown that Cl‐doped Mandrels produced from a blend of polystyrene and poly(p‐chlorostyrene) are rough on a length scale of 10’s of microns with amplitudes of as much as a 100 nm. The origin of this roughness will be discussed, and it will be shown that thi...
