Pipes inevitably encounter high ambient pressure and bending moment during the deepwater pipe-laying process,which can lead to elliptical buckling and even deterioration failure.For the safety of pipe-laying operation...Pipes inevitably encounter high ambient pressure and bending moment during the deepwater pipe-laying process,which can lead to elliptical buckling and even deterioration failure.For the safety of pipe-laying operation,available formulas for the pipe stability are established on the basis of the assumption of uniform deformation along the tube length and symmetrical buckling.This method can predict the nonlinear response of elliptical collapse of steel circular tubes for different ratios of diameter to thickness（D/t）under pure bending or combined bending and external pressure.In these formulas,the strain-displacement relationship is deduced from the nonlinear ring theory,and the Ramberg-Osgood constitutive model is applied to simulate the inelastic material behavior.Meanwhile,the principle of virtual work is adopted to derive the equilibrium equations.A set of equations is solved by the Newton-Raphson method,and the iterative scheme contains nested iteration for the constitutive relation.In order to check the effectiveness of this theoretical method,illustrative examples are presented in this paper.Besides,the numerical simulation is carried out by use of ANSYS.A comparison of the results shows that the theoretical method can provide reasonable prediction for engineering practice.展开更多
In this paper we use the Green function method to solve the problem of steady one dimensional flow of an incompressible viscous, electrically conducting fluid through a pipe with partial circular ring cross sec- tion ...In this paper we use the Green function method to solve the problem of steady one dimensional flow of an incompressible viscous, electrically conducting fluid through a pipe with partial circular ring cross sec- tion and one with annular cross section, in the presence of an applied transverse uniform magnetic field, We ob- tain analytic solutions and carry out some numerical calculations of the velocity distribution and induced magnet- ic field.展开更多
Research on compact manufacturing technology for shape and performance controllability of metallic components can reanze the simplification and high-reliability of manufacturing process on the premise of satisfying th...Research on compact manufacturing technology for shape and performance controllability of metallic components can reanze the simplification and high-reliability of manufacturing process on the premise of satisfying the requirement of macro/micro-structure. It is not only the key paths in improving performance, saving material and energy, and green manufacturing of components used in major equipments, but also the challenging subjects in frontiers of advanced plastic forming. To provide a novel horizon for the manufacturing in the critical components is significant. Focused on the high-performance large-scale components such as bearing rings, flanges, railway wheels, thick-walled pipes, etc, the conventional processes and their developing situations are summarized. The existing problems including multi-pass heating, wasting material and energy, high cost and high-emission are discussed, and the present study unable to meet the manufacturing in high-quality components is also pointed out. Thus, the new techniques related to casting-rolling compound precise forming of rings, compact manufacturing for duplex-metal composite rings, compact manufacturing for railway wheels, and casting-extruding continuous forming of thick-walled pipes are introduced in detail, respectively. The corresponding research contents, such as casting ring blank, hot ring rolling, near solid-state pressure forming, hot extruding, are elaborated. Some findings in through-thickness microstructure evolution and mechanical properties are also presented. The components produced by the new techniques are mainly characterized by fine and homogeneous grains. Moreover, the possible directions for fin＇ther development of those techniques are suggested. Finally, the key scientific problems are first proposed. All of these results and conclusions have reference value and guiding significance for the integrated control of shape and performance in advanced compact manufacturing.展开更多
超大断面隧道(断面面积大于100 m 2)开挖面积大,围岩扰动性强,因此常常需要进行超前支护控制隧道施工安全,管棚注浆加固是一种常见的隧道超前支护方式,其主要通过在隧道围岩上方形成注浆加固圈从而控制围岩应力和变形大小。在进行数值...超大断面隧道(断面面积大于100 m 2)开挖面积大,围岩扰动性强,因此常常需要进行超前支护控制隧道施工安全,管棚注浆加固是一种常见的隧道超前支护方式,其主要通过在隧道围岩上方形成注浆加固圈从而控制围岩应力和变形大小。在进行数值模拟计算过程中,注浆加固圈厚度是计算结果准确的关键。依托渝黔铁路张家山隧道工程,考虑管棚外插角和搭接长度对注浆加固圈厚度的影响,对传统计算公式进行优化,采用FLAC3D对比分析未使用管棚注浆加固和使用管棚注浆加固两种计算工况。结果表明:①优化后的注浆加固圈厚度计算公式与管棚外插角、浆液扩散半径、管棚长度、管棚纵向间距和环向间距5个参数相关,且使用优化后计算公式得到的数值模拟结果与现场监测数据更接近,计算结果更准确;②相较于未使用超前管棚注浆支护,使用超前管棚注浆支护拱顶沉降位移为12.65 mm,减小31.06%;③管棚注浆支护能够降低围岩竖向最大压应力20.72%和最大竖向拉应力44.68%,同时能够降低初期支护结构最大主压应力15.87%和最大主拉应力23.81%;④管棚注浆加固的地表沉降最大值为8.95 mm,较未使用管棚注浆加固减少24.25%;⑤管棚注浆加固效果与浆液扩散半径、管棚外插角和管棚长度呈正相关,与管棚纵向间距和环向间距呈负相关,其中浆液扩散半径影响效果最显著,管棚外插角影响最小。展开更多
基金supported by the National High Technology Research and Development Programof China(863 Program,Grant No.2006AA09A105)
文摘Pipes inevitably encounter high ambient pressure and bending moment during the deepwater pipe-laying process,which can lead to elliptical buckling and even deterioration failure.For the safety of pipe-laying operation,available formulas for the pipe stability are established on the basis of the assumption of uniform deformation along the tube length and symmetrical buckling.This method can predict the nonlinear response of elliptical collapse of steel circular tubes for different ratios of diameter to thickness（D/t）under pure bending or combined bending and external pressure.In these formulas,the strain-displacement relationship is deduced from the nonlinear ring theory,and the Ramberg-Osgood constitutive model is applied to simulate the inelastic material behavior.Meanwhile,the principle of virtual work is adopted to derive the equilibrium equations.A set of equations is solved by the Newton-Raphson method,and the iterative scheme contains nested iteration for the constitutive relation.In order to check the effectiveness of this theoretical method,illustrative examples are presented in this paper.Besides,the numerical simulation is carried out by use of ANSYS.A comparison of the results shows that the theoretical method can provide reasonable prediction for engineering practice.
文摘In this paper we use the Green function method to solve the problem of steady one dimensional flow of an incompressible viscous, electrically conducting fluid through a pipe with partial circular ring cross sec- tion and one with annular cross section, in the presence of an applied transverse uniform magnetic field, We ob- tain analytic solutions and carry out some numerical calculations of the velocity distribution and induced magnet- ic field.
基金Supported by National Natural Science Foundation of China(Grant Nos.51675361,51575371)Key Program of National Natural Science Foundation of China(Grant No.51135007)Key Research Project of Shanxi Province(Grant No.03012015004)
文摘Research on compact manufacturing technology for shape and performance controllability of metallic components can reanze the simplification and high-reliability of manufacturing process on the premise of satisfying the requirement of macro/micro-structure. It is not only the key paths in improving performance, saving material and energy, and green manufacturing of components used in major equipments, but also the challenging subjects in frontiers of advanced plastic forming. To provide a novel horizon for the manufacturing in the critical components is significant. Focused on the high-performance large-scale components such as bearing rings, flanges, railway wheels, thick-walled pipes, etc, the conventional processes and their developing situations are summarized. The existing problems including multi-pass heating, wasting material and energy, high cost and high-emission are discussed, and the present study unable to meet the manufacturing in high-quality components is also pointed out. Thus, the new techniques related to casting-rolling compound precise forming of rings, compact manufacturing for duplex-metal composite rings, compact manufacturing for railway wheels, and casting-extruding continuous forming of thick-walled pipes are introduced in detail, respectively. The corresponding research contents, such as casting ring blank, hot ring rolling, near solid-state pressure forming, hot extruding, are elaborated. Some findings in through-thickness microstructure evolution and mechanical properties are also presented. The components produced by the new techniques are mainly characterized by fine and homogeneous grains. Moreover, the possible directions for fin＇ther development of those techniques are suggested. Finally, the key scientific problems are first proposed. All of these results and conclusions have reference value and guiding significance for the integrated control of shape and performance in advanced compact manufacturing.
文摘超大断面隧道(断面面积大于100 m 2)开挖面积大,围岩扰动性强,因此常常需要进行超前支护控制隧道施工安全,管棚注浆加固是一种常见的隧道超前支护方式,其主要通过在隧道围岩上方形成注浆加固圈从而控制围岩应力和变形大小。在进行数值模拟计算过程中,注浆加固圈厚度是计算结果准确的关键。依托渝黔铁路张家山隧道工程,考虑管棚外插角和搭接长度对注浆加固圈厚度的影响,对传统计算公式进行优化,采用FLAC3D对比分析未使用管棚注浆加固和使用管棚注浆加固两种计算工况。结果表明:①优化后的注浆加固圈厚度计算公式与管棚外插角、浆液扩散半径、管棚长度、管棚纵向间距和环向间距5个参数相关,且使用优化后计算公式得到的数值模拟结果与现场监测数据更接近,计算结果更准确;②相较于未使用超前管棚注浆支护,使用超前管棚注浆支护拱顶沉降位移为12.65 mm,减小31.06%;③管棚注浆支护能够降低围岩竖向最大压应力20.72%和最大竖向拉应力44.68%,同时能够降低初期支护结构最大主压应力15.87%和最大主拉应力23.81%;④管棚注浆加固的地表沉降最大值为8.95 mm,较未使用管棚注浆加固减少24.25%;⑤管棚注浆加固效果与浆液扩散半径、管棚外插角和管棚长度呈正相关,与管棚纵向间距和环向间距呈负相关,其中浆液扩散半径影响效果最显著,管棚外插角影响最小。
