共查询到16条相似文献,搜索用时 434 毫秒
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基于解析法的非均匀张力作用下运动薄膜的稳定性 总被引:1,自引:1,他引:0
目的针对高速印刷运动薄膜在传输制备过程中由于相邻导纸辊等支撑副的平行度误差,料膜沿宽度方向张力分布易出现不均匀性问题,研究提高印刷设备的工作稳定性的方法。方法根据D’Alembert原理建立运动薄膜的横向振动微分方程,引入无量纲量,将微分方程转化为无量纲形式,利用解析法求解运动薄膜的复频率方程。结果得到不同参数下无量纲复频率与无量纲速度的变化曲线,当增大张力系数、张力比,或者减小长宽比时,薄膜系统达到发散失稳的临界无量纲速度增大,运动薄膜系统越稳定。结论获得了在不同张力比、张力系数、长宽比等参数下薄膜系统达到发散失稳的临界无量纲速度。 相似文献
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目的 印刷电子薄膜要求涂层均匀、套印精度高,文中旨在研究不同参数对柔性电子多层膜动态稳定性的影响,为柔性电子膜的稳定传输提供理论指导。方法 应用Hamilton原理建立运动多层膜结构的振动微分方程,采用隐式龙格库塔法求解离散得到的状态方程,根据Floquet理论计算系统 时对应的Ω和c1。结果 在对边简支对边固支边界条件下,运动多层膜稳定区域更大。此外,减小平均速度、张力比、非均匀张力系数,增大长宽比,可以提高运动多层膜的稳定性,其中平均速度变化的影响最为显著。结论 通过建立实际生产中运动柔性电子多层膜数学模型,得到了不同参数对运动多层膜动态稳定性影响规律,研究结果为柔性电子多层膜稳定传输,提高涂层均匀性、叠印精度提供了理论依据。 相似文献
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矩形薄板在随从力作用下的动力稳定性分析 总被引:15,自引:0,他引:15
本文用Levy法和有限差分法相结合,研究了两对边简支、另两对边为三种典型支承任意组合的六种弹性矩形薄板在切向均布随从力作用下的动力稳定性问题.通过数值计算,给出各种支承板的失稳形式及相应的临界载荷,并分析了泊松比、板的边长比对板的失稳形式及临界载荷的影响. 相似文献
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介绍在线涂布聚酯薄膜生产设备、工艺流程,以及对影响在线涂布薄膜发展的涂布膜生产稳定性的因素进行分析。 相似文献
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A. Y. T. Leung W. E. Zhou C. W. Lim R. K. K. Yuen U. Lee 《International journal for numerical methods in engineering》2001,51(5):531-552
A follower force is an applied force whose direction changes according to the deformed shape during the course of deformation. The dynamic stiffness matrix of a non‐uniform Timoshenko column under follower force is formed by the power‐series method. The dynamic stiffness matrix is unsymmetrical due to the non‐conservative nature of the follower force. The frequency‐dependent mass matrix is still symmetrical and positive definite according to the extended Leung theorem. An arc length continuation method is introduced to find the influence of a concentrated follower force, distributed follower force, end mass and stiffness, slenderness, and taper ratio on the natural frequency and stability. It is found that the power‐series method can handle a very wide class of dynamic stiffness problem. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Experimental and numerical investigations have been carried out to study the effect of processing parameters on edge cracks in cold rolling process of silicon steels. The onset of edge cracks has been simulated by using finite element method (FEM) based on the Gurson–Tvergaard–Needleman damage model. Factorial design and Taguchi experimental design methods have been proposed to analyze the effects of reduction ratio, tension, work roll diameter, and friction coefficient on the formation of edge cracks. Parametric studies indicated that with the increasing of reduction ratio, friction coefficient, and tension, the crack length increases. A bigger work roll is beneficial to restrict the edge crack growth as well. The rank according to the impact degrees on the crack initiation from high to low is reduction ratio, tension, work roll diameter, and friction coefficient. Meanwhile, the combined effect curve of reduction ratio and tension on crack length was obtained which was validated by the experimental results as well. 相似文献
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褶皱变形是柔性薄膜结构的一种常见的失稳模式,其数值模拟具有挑战性。基于连续体和张力场理论,提出了一种适用于充气薄膜结构褶皱分析的互补共旋有限元方法。采用共旋坐标法,将物体的大变形分解为结构整体坐标系下的刚体运动和单元局部坐标系下小应变变形,推导了一个空间三节点三角形膜单元的切线刚度矩阵。该刚度矩阵包含材料刚度、旋转刚度和平衡投影刚度矩阵三个部分,涵盖了随动载荷对单元刚度的影响。在单元局部坐标系下,依据双模量材料本构关系构造了一个褶皱模型,能够判断单元处于“张紧”“褶皱”或“松弛”状态。进一步通过建立等价的线性互补问题,消除了迭代求解过程中的内力振荡,改善了算法的稳定性。数值算例表明:该文方法能够准确地预测充气薄膜结构的位移、应力以及褶皱区域。较之已有的“拟动态”和“惩罚”方法,该方法不需要引入额外的求解技术来保证收敛,具有良好的稳定性。 相似文献
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Y. Leterrier D. Pellaton D. Mendels R. Glauser J. Andersons J.-A. E. Månson 《Journal of Materials Science》2001,36(9):2213-2225
Crack patterns of 53 nm and 103 nm thick silicon oxide coatings on poly(ethylene terephthalate) films are analyzed under equibiaxial stress loading, by means of a bulging cell mounted under an optical microscope with stepwise pressurization of film specimens. The biaxial stress and strain are modeled from classical elastic membrane equations, and an excellent agreement is obtained with a finite element method. In the large pressure range, the derivation of the biaxial strain from force equilibrium considerations are found to reproduce accurately the measured data up to 25% strain. The examination of the fragmentation process of the coating under increasing pressure levels reveals that the crack onset strain of the oxide coating is similar to that measured under uniaxial tension. The fragmentation of the coating under biaxial tension is also characterized by complex dynamic phenomena which image the peculiarities of the stress field, resulting in considerable broadening of the fragment size distribution. The evolution of the average fragment area as a function of biaxial stress in the early stages of the fragmentation process is analyzed using Weibull statistics to describe the coating strength. 相似文献
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目的解决新型悬浮包装缓冲衬垫生产中薄膜张力难以控制的问题。方法建立非连续覆膜环节中张力系统的数学模型,提出以Lab VIEW为仿真软件,模糊自适应PID为控制算法的仿真策略。分析在不同卷径、不同加速度和加减速方式下,薄膜张力的变化情况和算法的控制效果。结果仿真结果表明,薄膜卷径越小张力波动越大,运行加速度越大薄膜张力波动越大。在不同工况下,模糊自适应PID较常规PID有更快的响应速度和更小的超调量。结论模糊自适应PID参数调整简单,适应性好,能满足非连续覆膜过程中薄膜张力稳定的控制要求。 相似文献