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H. K. Yang - One of the best experts on this subject based on the ideXlab platform.

  • Significance-based optimization of processing parameters for thin-walled aluminum alloy tube NC Bending with small Bending Radius
    Transactions of Nonferrous Metals Society of China (English Edition), 2012
    Co-Authors: H. K. Yang, Heng Li, Mei Zhan
    Abstract:

    Thin-walled aluminum alloy tube numerical control (NC) Bending with small Bending Radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element (FE) simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC Bending d 50 mm×1 mm ×75 mm and d 70 mm×1.5 mm×105 mm (initial tube outside diameter D 0×initial tube wall thickness t 0×Bending Radius R), and qualified tubes are produced. © 2012 The Nonferrous Metals Society of China.

  • Analysis of wrinkling limit of rotary-draw Bending process for thin-walled rectangular tube
    Journal of Materials Processing Technology, 2010
    Co-Authors: G. Y. Zhao, C. S. Dong, H. K. Yang, Y.l. Liu, X. G. Fan
    Abstract:

    The rotary-draw Bending process for thin-walled rectangular tube of aluminum alloy may produce a wrinkling phenomenon if processing parameters are inappropriate, especially for tubes with thin wall and small Bending Radius. To predict this wrinkling rule rapidly and accurately, here, a wrinkling wave function was proposed and a wrinkling prediction model was developed based on the deformation theory of plasticity combined with the energy method, and then the minimum Bending Radius without the occurrence of wrinkling in the process was obtained. Furthermore, the effects of geometrical parameters and the material properties of the tube on the minimum Bending Radius were analyzed. The results show that larger thickness-to-width ratio (t/b) and thickness-to-height ratio (t/h) are beneficial to improve the wrinkling limit of the tube. The minimum Bending Radius becomes smaller with an increase in strain-hardening exponent of the tube, whereas with the strength coefficient decreasing. And the Young's modulus has little effect on the wrinkling limit. These achievements are helpful to develop the Bending technique and provide a guideline in rotary-draw Bending process for thin-walled rectangular aluminum alloy tube. ?? 2010 Elsevier B.V. All rights reserved.

  • Numerical study on deformation behaviors of thin-walled tube NC Bending with large diameter and small Bending Radius
    Computational Materials Science, 2009
    Co-Authors: Heng Li, J Yan, H. K. Yang, Mei Zhan
    Abstract:

    With respect to wrinkling, wall thinning and cross section deformation, combined with analytical description, the deformation behaviors of thin-walled tube NC Bending with large diameter D/t (50.0-87.0) and small Bending Radius Rd/D (1.0-2.0) are explored via a series of reliable 3D-FE models under ABAQUS platform. The results show that: (1) The segmentation feature is observed for the deformation fields such as effective compressive/tensile regions τc / τt, stress/strain distributions, wrinkling tendency, wall thinning and cross section deformation. With smaller Rd/D, the tangent stress increases and becomes more inhomogenous. The maximum tangent stress σφ at the intrados increases by 46% with Rd/D from 2.0 to 1.2. While the distributions of σφ are nearly similar with larger D/t. With smaller Rd/D and larger D/t, the velocity variation of tube materials becomes more obvious. (2) The wrinkling tendency and cross section deformation degree Δ D increase with smaller Rd/D and larger D/t; With smaller Rd/D, both the wall thinning and thickening degrees increase. The maximum wall thinning and thickening degrees increase by 24.0% and 52.5%, respectively. However, with larger D/t, the wall thinning degree increases, while the thickening degree decreases significantly. The maximum wall thinning degree increases by 31.3%, while the maximum thickening one decreases by 58.9%. Crown Copyright © 2009.

  • Forming characteristics of thin-walled tube Bending process with small Bending Radius
    Transactions of Nonferrous Metals Society of China (English Edition), 2006
    Co-Authors: Heng Li, H. K. Yang, Mei Zhan, R. J. Gu
    Abstract:

    Currently requirements of thin-walled tube with small Bending Radius cause the defects such as wrinkling, overthinning and cross-section distortion more prone to occur in Bending process. Based on the analysis of the forming characteristics by analytical and experimental methods, a complete 3D elastic-plastic FEM model of the process was developed using ABAQUS/Explicit code, including Bending process, balls retracting and unloading process, and thus the plastic deformation characteristics with small Bending Radius were investigated. The main results show that: 1) The utmost deformation feature of the NC Bending process is its continuous progressive deformation. 2) The occurring conditions of the defects such as wrinkling and tension instability in the process are obtained. The wrinkling is traditional on the double compressive stresses state and the tension instability is on the double tension stresses state. 3) The enhanced non-uniform deformation in thin-walled tube with small Bending Radius is demonstrated by comparing the stress/strains distributions under the 1.5D and 1D Bending conditions. 4) For 1D small Bending process, a new method-'stepped mandrel retraction' is proposed to improve the Bending quality in experiment according to the FE simulation. The simulation results are verified by experiment.

  • Wrinkling analysis for forming limit of tube Bending processes
    Journal of Materials Processing Technology, 2004
    Co-Authors: H. K. Yang, Yan Lin
    Abstract:

    Thin-walled tube Bending processes may produce a wrinkling phenomenon if the process parameters are inappropriate, especially for tubes with large diameter and thin wall thickness. How to predict this phenomenon rapidly and accurately is one of the urgent key problems to be solved for the development of this process at present. In this paper, a wrinkling wave function is proposed and a simplified wrinkling prediction model to predict the minimum Bending Radius for tubes is established based on thin-shell theory, forming theory, the energy principle and wave function. The minimum Bending Radius calculated according to the method established is in agreement with data reported in the literature. Furthermore, effects of parameters on the minimum Bending Radius are also analyzed: (1) the influence of Bending angle on the minimum Bending Radius is negligibly small; (2) the effect of geometrical dimensions and material properties of tubes on the minimum Bending Radius is significantly large; (3) the minimum Bending Radius becomes larger with the original Radius and strength coefficient of tubes increasing, whereas with the wall thickness and strain hardening exponent decreasing. The results are helpful to the design and optimization of the relevant processes in practice. ?? 2004 Elsevier B.V. All rights reserved.

Mei Zhan - One of the best experts on this subject based on the ideXlab platform.

  • Significance-based optimization of processing parameters for thin-walled aluminum alloy tube NC Bending with small Bending Radius
    Transactions of Nonferrous Metals Society of China (English Edition), 2012
    Co-Authors: H. K. Yang, Heng Li, Mei Zhan
    Abstract:

    Thin-walled aluminum alloy tube numerical control (NC) Bending with small Bending Radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element (FE) simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC Bending d 50 mm×1 mm ×75 mm and d 70 mm×1.5 mm×105 mm (initial tube outside diameter D 0×initial tube wall thickness t 0×Bending Radius R), and qualified tubes are produced. © 2012 The Nonferrous Metals Society of China.

  • significance based optimization of processing parameters for thin walled aluminum alloy tube nc Bending with small Bending Radius
    Transactions of Nonferrous Metals Society of China, 2012
    Co-Authors: He Yang, Li Heng, Mei Zhan
    Abstract:

    Abstract Thin-walled aluminum alloy tube numerical control (NC) Bending with small Bending Radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element (FE) simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC Bending d 50 mm×1 mm ×75 mm and d 70 mm×1.5 mm×105 mm (initial tube outside diameter D 0 ×initial tube wall thickness t 0 ×Bending Radius R ), and qualified tubes are produced.

  • Numerical study on deformation behaviors of thin-walled tube NC Bending with large diameter and small Bending Radius
    Computational Materials Science, 2009
    Co-Authors: Heng Li, J Yan, H. K. Yang, Mei Zhan
    Abstract:

    With respect to wrinkling, wall thinning and cross section deformation, combined with analytical description, the deformation behaviors of thin-walled tube NC Bending with large diameter D/t (50.0-87.0) and small Bending Radius Rd/D (1.0-2.0) are explored via a series of reliable 3D-FE models under ABAQUS platform. The results show that: (1) The segmentation feature is observed for the deformation fields such as effective compressive/tensile regions τc / τt, stress/strain distributions, wrinkling tendency, wall thinning and cross section deformation. With smaller Rd/D, the tangent stress increases and becomes more inhomogenous. The maximum tangent stress σφ at the intrados increases by 46% with Rd/D from 2.0 to 1.2. While the distributions of σφ are nearly similar with larger D/t. With smaller Rd/D and larger D/t, the velocity variation of tube materials becomes more obvious. (2) The wrinkling tendency and cross section deformation degree Δ D increase with smaller Rd/D and larger D/t; With smaller Rd/D, both the wall thinning and thickening degrees increase. The maximum wall thinning and thickening degrees increase by 24.0% and 52.5%, respectively. However, with larger D/t, the wall thinning degree increases, while the thickening degree decreases significantly. The maximum wall thinning degree increases by 31.3%, while the maximum thickening one decreases by 58.9%. Crown Copyright © 2009.

  • Forming characteristics of thin-walled tube Bending process with small Bending Radius
    Transactions of Nonferrous Metals Society of China (English Edition), 2006
    Co-Authors: Heng Li, H. K. Yang, Mei Zhan, R. J. Gu
    Abstract:

    Currently requirements of thin-walled tube with small Bending Radius cause the defects such as wrinkling, overthinning and cross-section distortion more prone to occur in Bending process. Based on the analysis of the forming characteristics by analytical and experimental methods, a complete 3D elastic-plastic FEM model of the process was developed using ABAQUS/Explicit code, including Bending process, balls retracting and unloading process, and thus the plastic deformation characteristics with small Bending Radius were investigated. The main results show that: 1) The utmost deformation feature of the NC Bending process is its continuous progressive deformation. 2) The occurring conditions of the defects such as wrinkling and tension instability in the process are obtained. The wrinkling is traditional on the double compressive stresses state and the tension instability is on the double tension stresses state. 3) The enhanced non-uniform deformation in thin-walled tube with small Bending Radius is demonstrated by comparing the stress/strains distributions under the 1.5D and 1D Bending conditions. 4) For 1D small Bending process, a new method-'stepped mandrel retraction' is proposed to improve the Bending quality in experiment according to the FE simulation. The simulation results are verified by experiment.

Heng Li - One of the best experts on this subject based on the ideXlab platform.

  • bp artificial neural network modeling for accurate Radius prediction and application in incremental in plane Bending
    The International Journal of Advanced Manufacturing Technology, 2015
    Co-Authors: He Yang, Heng Li, Honglie Zhang, Wenting Tang
    Abstract:

    Incremental in-plane Bending (IIB) is a new and advanced flexible manufacturing technology for small-lot production of strip with various Bending radii. The strip of sheet metal is bent incrementally by a beating inclined punch. The Bending Radius is strongly affected by mechanical properties of the material, geometry of the strip, and processing parameters. It is difficult to predict the Bending Radius due to the complex synergistic effects of the controlling parameters. How to predict the Bending Radius accurately has therefore become a key point to be urgently solved in the development of this advanced forming technology. In this paper, a model based on a back propagation neural network (BPNN) is introduced to reveal the relationship of Bending Radius with angle of die α, indentation s, pitch p, and width of strip w. Out of 14 different BPNN architectures trained, the 4-9-9-1 BPNN with two hidden layers having nine neurons trained with the Levenberg-Marquardt algorithm (trainlm) is found to be the optimum network model, and the prediction error is less than 2 % on average. Otherwise, a 1-9-9-4 reverse BPNN is developed to build the processing window for a given Bending Radius. Meanwhile, taking section moment of inertia I as a quantitative index of forming stability, α, p, s, w0 are optimized as design variables in order to make objective functions of I maximized simultaneously. Finally, to verify its predictive capability, the present approach is applied to a case study, and the optimal combination of parameters for stable forming during IIB is obtained.

  • FE-Based Analysis of Heat Bending of Thin-Walled Ti-Alloy Tube with Large Diameter and Small Bending Radius
    Advanced Materials Research, 2012
    Co-Authors: Heng Li, He Yang, Dan Wang, Zhiyong Zhang
    Abstract:

    The numerical control (NC) heat Bending of thin-walled Ti-alloy tube with large diameter and small Bending Radius with Ф50×1×R75mm (diameter OD Bending Radius CLR) is explored by 3D-FE thermal-mechanical coupling simulation of heat conducting and NC Bending. The results show that: (1) The heating of both pressure die and mandrel is proved to be appropriate to obtain the required temperature field. (2) In terms of wall thickness variation, wrinkling and cross-section deformation, the optimum span of the key parameters are obtained: the Bending velocity of 0.4rad/s, the matched pressure die speed of 80%-110%, and temperature of 600-800°C.

  • Significance-based optimization of processing parameters for thin-walled aluminum alloy tube NC Bending with small Bending Radius
    Transactions of Nonferrous Metals Society of China (English Edition), 2012
    Co-Authors: H. K. Yang, Heng Li, Mei Zhan
    Abstract:

    Thin-walled aluminum alloy tube numerical control (NC) Bending with small Bending Radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element (FE) simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC Bending d 50 mm×1 mm ×75 mm and d 70 mm×1.5 mm×105 mm (initial tube outside diameter D 0×initial tube wall thickness t 0×Bending Radius R), and qualified tubes are produced. © 2012 The Nonferrous Metals Society of China.

  • Numerical study on deformation behaviors of thin-walled tube NC Bending with large diameter and small Bending Radius
    Computational Materials Science, 2009
    Co-Authors: Heng Li, J Yan, H. K. Yang, Mei Zhan
    Abstract:

    With respect to wrinkling, wall thinning and cross section deformation, combined with analytical description, the deformation behaviors of thin-walled tube NC Bending with large diameter D/t (50.0-87.0) and small Bending Radius Rd/D (1.0-2.0) are explored via a series of reliable 3D-FE models under ABAQUS platform. The results show that: (1) The segmentation feature is observed for the deformation fields such as effective compressive/tensile regions τc / τt, stress/strain distributions, wrinkling tendency, wall thinning and cross section deformation. With smaller Rd/D, the tangent stress increases and becomes more inhomogenous. The maximum tangent stress σφ at the intrados increases by 46% with Rd/D from 2.0 to 1.2. While the distributions of σφ are nearly similar with larger D/t. With smaller Rd/D and larger D/t, the velocity variation of tube materials becomes more obvious. (2) The wrinkling tendency and cross section deformation degree Δ D increase with smaller Rd/D and larger D/t; With smaller Rd/D, both the wall thinning and thickening degrees increase. The maximum wall thinning and thickening degrees increase by 24.0% and 52.5%, respectively. However, with larger D/t, the wall thinning degree increases, while the thickening degree decreases significantly. The maximum wall thinning degree increases by 31.3%, while the maximum thickening one decreases by 58.9%. Crown Copyright © 2009.

  • Forming characteristics of thin-walled tube Bending process with small Bending Radius
    Transactions of Nonferrous Metals Society of China (English Edition), 2006
    Co-Authors: Heng Li, H. K. Yang, Mei Zhan, R. J. Gu
    Abstract:

    Currently requirements of thin-walled tube with small Bending Radius cause the defects such as wrinkling, overthinning and cross-section distortion more prone to occur in Bending process. Based on the analysis of the forming characteristics by analytical and experimental methods, a complete 3D elastic-plastic FEM model of the process was developed using ABAQUS/Explicit code, including Bending process, balls retracting and unloading process, and thus the plastic deformation characteristics with small Bending Radius were investigated. The main results show that: 1) The utmost deformation feature of the NC Bending process is its continuous progressive deformation. 2) The occurring conditions of the defects such as wrinkling and tension instability in the process are obtained. The wrinkling is traditional on the double compressive stresses state and the tension instability is on the double tension stresses state. 3) The enhanced non-uniform deformation in thin-walled tube with small Bending Radius is demonstrated by comparing the stress/strains distributions under the 1.5D and 1D Bending conditions. 4) For 1D small Bending process, a new method-'stepped mandrel retraction' is proposed to improve the Bending quality in experiment according to the FE simulation. The simulation results are verified by experiment.

Kunimasa Saitoh - One of the best experts on this subject based on the ideXlab platform.

  • All-solid photonic bandgap fibers for fiber laser applications
    2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEOPR), 2013
    Co-Authors: Kunimasa Saitoh, Shota Saitoh, Masahiro Kashiwagi, Shoichiro Matsuo, Liang Yao-dong
    Abstract:

    Core size scaling in all-solid photonic bandgap fibers (AS-PBGFs) is discussed. It is shown that the effectively single-mode AS-PBGF with 100-μm core diameter can be achievable with 40-cm Bending Radius operating in the 3rd PBG.

  • analytical expression of average power coupling coefficients for estimating intercore crosstalk in multicore fibers
    IEEE Photonics Journal, 2012
    Co-Authors: Masanori Koshiba, Kunimasa Saitoh, Katsuhiro Takenaga, Shoichiro Matsuo
    Abstract:

    In order to realize fast and accurate estimation of intercore crosstalk in bent multicore fibers (MCFs), an analytical expression of the average power-coupling coefficient (PCC) based on an exponential autocorrelation function is, for the first time, derived, resulting in no need for heavy numerical computations. It is revealed that, when the Bending Radius is large and the correlation length is large, the average PCC is inversely proportional to the correlation length and to the square of the propagation constant difference Δβmn between core m and core n, and when the Bending Radius is small and the correlation length is large, the average PCC is proportional to the Bending Radius and is independent of the correlation length. When the correlation length is small, on the other hand, the average PCC is proportional to the correlation length and is independent of the Bending Radius. For homogeneous MCFs (Δβmn = 0) with small Bending Radius, the average PCC coincides with the mean crosstalk increase per unit length derived from the coupled-mode theory of Hayashi et al. that is proportional to the Bending Radius. Average crosstalk values calculated by using the analytical expression derived here are in excellent agreement with those of numerical solutions of coupled-power equations, irrespective of the values of Bending Radius and correlation length.

  • Enlargement of effective area of effectively single-mode all-solid photonic bandgap fiber with low Bending loss
    2012 17th Opto-Electronics and Communications Conference, 2012
    Co-Authors: T. Ichige, Masahiro Kashiwagi, Shoichiro Matsuo, Kunimasa Saitoh, K. Takenaga, S. Tanigawa, M. Fujimaki
    Abstract:

    Effectively single-mode all-solid photonic bandgap fiber with an effective area of 830 μm2 and a Bending loss of less than 0.1 dB/m at a Bending Radius of 15-cm has been demonstrated.

  • Design and Fabrication of Large-Mode Area Air-Clad Leakage Channel Fiber With Superior Bending Characteristics
    IEEE Photonics Technology Letters, 2012
    Co-Authors: Kunimasa Saitoh, M. C. Paul, Debashri Ghosh, S. K. Bhadra
    Abstract:

    We investigate the Bending characteristics of leakage channel fibers (LCFs) to achieve large-mode area and effectively single-mode operation with a practically allowable Bending Radius of 5 cm for compact Yb-doped fiber laser applications. We design and fabricate a two-ring air-clad LCF whose Bending characteristics have been studied both by numerical analysis through the full-vectorial finite element method and experimentally. The LCF has bend-loss of 0.09 dB/m and effective area of 350 μm2 for a 5-cm Bending Radius. The single-mode nature of the bent LCF at 1064 nm is presented.

Li Heng - One of the best experts on this subject based on the ideXlab platform.

  • Experimental study on thinning of thin-walled tube NC Bending process with small Bending Radius
    Forging and Stamping Technology, 2020
    Co-Authors: Li Heng
    Abstract:

    Outwall thinning is a main flaw in tube NC Bending process,especially for the thin-walled tube with a small Bending Radius(R/D≤2).Wall thinning of Bending section in this forming process was investigated by the method of experiment.The influence laws of forming parameters,such as mandrel balls number,mandrel extension length,Bending angle,friction between boost and tube,velocity of pressure die,Bending Radius and material parameters,were obtained.The results show that increasing the pressure die speed and friction between pressure die and tube suitably are benefit to wall thinning controlling.The deformation characteristic of 1Cr18Ni9Ti tube is different from that of LF2M tube,and LF2M tube is easily to be cracked.

  • Experimental study on cross-section ovalization of thin-walled tube in NC Bending process
    Journal of Plasticity Engineering, 2020
    Co-Authors: Li Heng
    Abstract:

    Cross-section ovalization is one of the flaws in the thin-walled tube NC Bending process.The effects of some parameters,such as mandrel ball numbers,mandrel extension length,Bending angle,lubrication condition of pressure die,relative Bending Radius and material,on ovalization have been investigated by experimental method,and the effective methods to reduce the ovalization are proposed.The results show that increasing the ball numbers and mandrel extension length may reduce the ovalization,but leads to more remarkable wall thinning; the ovalization becomes more severe with the larger Bending angle; the smaller the relative Bending Radius,the larger the ovalization is;the ovalization and wall thinning degrees are both smaller in the case of pressure die with dry lubricant; and under the same Bending condition,the ovalization of LF2M tube is larger than the one of 1Cr18Ni9Ti tube.

  • significance based optimization of processing parameters for thin walled aluminum alloy tube nc Bending with small Bending Radius
    Transactions of Nonferrous Metals Society of China, 2012
    Co-Authors: He Yang, Li Heng, Mei Zhan
    Abstract:

    Abstract Thin-walled aluminum alloy tube numerical control (NC) Bending with small Bending Radius is a complex process with multi-factor coupling effects and multi-die constraints. A significance-based optimization method of the parameters was proposed based on the finite element (FE) simulation, and the significance analysis of the processing parameters on the forming quality in terms of the maximum wall thinning ratio and the maximum cross section distortion degree was implemented using the fractional factorial design. The optimum value of the significant parameter, the clearance between the tube and the wiper die, was obtained, and the values of the other parameters, including the friction coefficients and the clearances between the tube and the dies, the mandrel extension length and the boost velocity were estimated. The results are applied to aluminum alloy tube NC Bending d 50 mm×1 mm ×75 mm and d 70 mm×1.5 mm×105 mm (initial tube outside diameter D 0 ×initial tube wall thickness t 0 ×Bending Radius R ), and qualified tubes are produced.