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81.
Quasi-static and dynamic crushing behaviors of aluminum and steel tubes with a cutout 总被引:3,自引:0,他引:3
Tubular members are commonly used as an energy absorber in engineering structures and many such members have a cutout. In this study, the crushing behaviors of tubes with a cutout are characterized and the effects of cutout on the energy absorption capabilities of these tubes are quantified. Systematic parametric studies were carried out to study the effect of material properties, including yield and ultimate strength of material, strain rate effect, location of cutout, tube length and impact speed on the crushing behaviors and energy absorption capacity of aluminum and steel tubes. First, a numerical model was constructed with a commercial explicit finite element code. It will be first proven that the numerical simulation can produce sufficiently accurate results in an economic manner. Subsequently, the crushing behavior of aluminum and steel tubes with a cutout was experimentally characterized and their energy absorption capacity was evaluated in terms of mean crushing force, peak crushing force and specific energy absorption (SEA). Tubes of various lengths with a cutout located at different locations, subject to both quasi-static and dynamic impact loadings were considered. For steel tubes, the numerical simulation investigated the influence of the strain rate effect and variation in strain hardening ratio of the material. Empirical equations describing the mean and peak crushing forces of aluminum and steel tubes with a cutout were developed using linear and nonlinear regression methods applied to the results obtained from the numerical and experimental studies. 相似文献
82.
The iterative finite element model, in which an element is used to represent a single particle, is generated to analyze the
global behavior of multiple-material aggregates of materially nonlinear viscoplastic particles. The generalized Maxwell model
is used to define four types of specific nonlinear viscoplastic materials, which are the elasto visco-plastic matter with
linear viscosity, the plasto visco-plastic material with linear viscosity, the elasto visco-plastic media with nonlinear viscosity,
and the plasto visco-plastic media with nonlinear viscosity. The theory and relevant penalty iterative algorithm are developed
to analyze the four representative mixed granular systems consisting of materially nonlinear viscous particles. To verify
precision of stress calculation, solutions of an axis-symmetric radial flow problem are compared with results of the literature
and they are in a great agreement. The results present here provide significant insight into the fundamental behavior of granular
media under compaction conditions, including prediction of the overall aggregates stress-strain response. 相似文献
83.
较系统地介绍了我国第1条国产化的中宽带钢冷连轧生产线,即唐山建龙钢铁控股有限公司900mm冷连轧生产线的工艺流程、主要设备组成及技术特点。重点介绍了900mm 4机架六辊轧机的技术参数、性能特点及自动控制系统。该生产线投产以来,取得了较好效果。 相似文献
84.
中频反应溅射SiO2膜与直流溅射ITO膜的在线联镀 总被引:2,自引:2,他引:0
多数ITO透明导电玻璃生产线在实现SiO2膜与ITO膜在线联镀时,应用SiO2靶射频溅射沉积SiO2膜工艺和ITO靶直流溅射沉积ITO膜工艺,如果SiO2膜应用硅靶反应磁控溅射工艺,存在这种工艺是否可以与ITO靶直流溅射沉积ITO膜工艺在线联用以及如何实现联用的问题。作者对现有的生产线进行了改造设计、加工,做了大量实验、质谱分析和多项测试研究,成功地实现反应溅射SiO2膜与ITO膜在线联镀,做到SiO2镀膜室的工作状态的变化基本上不影响ITO镀膜室的工艺条件。 相似文献
85.
The application of the eXtended finite element method (X-FEM) to thermal problems with moving heat sources and phase boundaries
is presented. Of particular interest is the ability of the method to capture the highly localized, transient solution in the
vicinity of a heat source or material interface. This is effected through the use of a time-dependent basis formed from the
union of traditional shape functions with a set of evolving enrichment functions. The enrichment is constructed through the
partition of unity framework, so that the system of equations remains sparse and the resulting approximation is conforming.
In this manner, local solutions and arbitrary discontinuities that cannot be represented by the standard shape functions are
captured with the enrichment functions. A standard time-projection algorithm is employed to account for the time-dependence
of the enrichment, and an iterative strategy is adopted to satisfy local interface conditions. The separation of the approximation
into classical shape functions that remain fixed in time and the evolving enrichment leads to a very efficient solution strategy.
The robustness and utility of the method is demonstrated with several benchmark problems involving moving heat sources and
phase transformations.
Received 20 May 2001 / Accepted 19 December 2001 相似文献
86.
M. M. Rashid 《International journal for numerical methods in engineering》2002,55(4):431-450
A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
87.
铝电解槽磁流体稳定性有限元分析 总被引:2,自引:0,他引:2
本文采用有限元法求解分层磁流体小扰动方程系统特征值,研究铝电解槽稳定性。研究结果表明,在没有电磁力时,铝液表面波动(内波)是稳定的。存在电磁力时,它会激发铝液表面波动的某些低频长波分量不稳定性,高频短波不受影响。被激发的不稳定波动频率和扰动增长率与电流密度,磁感应强度垂直分量,铝电解槽长宽比,电解质和铝液的密度差,厚度等因素密切相关。减少电流密度,磁感应强度,增加电极距离和铝液厚度可以提高铝电解槽的稳定性。这对铝电解槽优化设计和在线控制有重要意义。 相似文献
88.
R. T. DeHoff 《Journal of microscopy》1985,138(2):143-151
Elements of surfaces that bound a phase (β) in a two phase mixture (α+β) may be classified as: (a) convex (++) if both principal curvatures are positive; (b) concave (? ?) if both are negative; and (c) saddle (+ ?) if one is positive and the other negative. This classification excludes the limiting cases for which one or both of the principal curvatures is zero. The traces of these surfaces that form the boundaries of the β areas on a representative two dimensional section may also be: (a) convex (+) if the local curvature is positive; or (b) concave (?) if it is negative. Line intercepts may be tabulated separately for intersections with convex (+) and concave (?) segments of boundary. This paper presents a derivation of fundamental stereological formulae that relate these counting measurements to three-dimensional geometric properties of the structure they sample. 相似文献
89.
介绍了隔河岩电厂220kV线路保护的原理设计及运行情况,以及采用了双重微机化继电保护装置后带来的优越性,简要描述了CSL-101A高频保护和RCS-931A光纤保护的应用特点。 相似文献
90.