共查询到18条相似文献,搜索用时 500 毫秒
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以凸肩叶片为研究对象,应用Donnell’s简化壳理论建立模型的非线性振动方程,考虑了几何非线性、阻尼、凸肩接触面正压力、摩擦力等因素。采用Galerkin法将振动微分方程离散到模态坐标上,分别应用数值法和近似解析法对方程组求解,得到系统的频率响应曲线,并讨论了系统周期解的稳定性。结果表明,由于凸肩接触面之间摩擦力方向周期性改变,导致系统的振动特性产生不连续性,以摩擦力为正、负方向分别绘制一条频率响应曲线。则随着摩擦力方向T/4周期变换一次,系统的振动也以T/4为周期在两条频率响应曲线上来回跳跃,从而有效抑制叶片的振动响应,提高叶片使用的安全性。 相似文献
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研究壳板凸肩叶片的静态和全局动态分岔。应用Donnell’s简化壳理论建立了壳板凸肩叶片的非线性振动微分方程,并考虑了几何非线性、阻尼、凸肩接触面正压力、摩擦力等因素。运用伽辽金方法对非线性振动微分方程离散化,应用平均法对离散后模态方程组进行解析分析,获得系统主共振情况下的平均方程和分岔方程。利用奇异性理论,得到了系统的转迁集和分岔图。通过研究平均方程的全局行为,得到了壳板凸肩叶片系统参数在各区域变化时系统周期解的变化过程及其具有的非线性动力学特性。研究壳板凸肩叶片的分岔特性可以为壳板凸肩叶片系统的动力学优化设计以及稳定性控制提供理论依据。 相似文献
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带凸肩叶片的稳态响应计算及其阻尼减振分析 总被引:6,自引:0,他引:6
研究干摩擦理论在航空发动机叶片组振动控制方面的应用,着重分析带凸肩叶片的动力特性及凸肩干摩擦副的阻尼减振规律。在引入凸肩干摩擦非线性连接元概念的基础上,将固定界面模态综合法推广应用于带凸肩叶片组动力有限元模型降阶;提出用阻尼因子解决凸肩干摩擦阻尼大小的度量问题;在稳态特性数值计算中构造了两步迭代算法,改善了Picard单步迭代法收敛性差的缺点。编制了相应的计算程序,完成两叶片系统计算模型的数值分析。 相似文献
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为有效地分析阻尼结构叶片系统的动力学特性,本文对计算非线性动力学系统响应的时频域融合算法进行了改进。引入快速抗混迭傅立叶变换,提高时域与频域间转换运算的精度,减少计算时间;针对阻尼结构叶片系统的局部非线性特点,对线性自由度进行减缩,将迭代求解控制在仅和非线性相关的自由度范围之内;采用混合遗传算法改善计算收敛性。使用改进的时频域融合算法对某真实燃机叶片的非线性强迫振动响应进行了分析。在一定的参数条件下,改进的时频域融合算法计算时间为原算法计算时间的 ,且精度误差不超过 。研究表明:改进的时频域融合算法能够适用于复杂摩擦接触下阻尼结构叶片的振动响应计算。 相似文献
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透平机械在运行中其叶片叶冠会发生摩擦现象,其接触面正压力常常不是恒定值。为了分析叶冠接触面摩擦行为的非线性特性,本文建立单自由度的二维变正压力摩擦动力学模型,并详细给出了整个求解过程。牛顿法是求解非线性方程组的常用迭代算法,迭代中过程的切向刚度矩阵是求解的难点。变正压力下具有强非线性,可根据滑移或黏滞的初始状态进行迭代求解。分析了多个数值算例,具体讨论了接触间隙、接触分离以及相位差对幅值和迟滞回线的影响,分析了摩擦力和变正压力的耦合影响,获得了二维运动状态下切向和法向位移的频响曲线。分析结果可应用到实际叶片的振动分析中,为研究透平机械阻尼叶片的振动非线性提供借鉴。 相似文献
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一种正压力随时间变化的微滑移干摩擦模型 总被引:1,自引:0,他引:1
《振动工程学报》2016,(3)
在Csaba摩擦模型的基础上发展了一种能够考虑接触面摩擦运动过程中正压力随时间变化的微滑移干摩擦模型。模型将局部微滑移运动与整体宏滑移运动进行了结合,采用在每个时间迭代上逐步分析判断摩擦微元运动状态的方法来描述摩擦运动过程中的黏滞、局部微动滑移、整体宏滑移以及分离状态,能够克服Csaba摩擦模型只能描述局部微滑移摩擦力、并且正压力分布不变的不足。对单谐波和多谐波外力作用下无分离状态及存在分离状态的干摩擦力进行了模拟。计算了凸肩阻尼结构模拟叶片在复杂激励下的非线性振动响应,研究了系统参数对干摩擦阻尼减振效果的影响,为工程中研究具有干摩擦阻尼结构叶片的接触面摩擦力提供了理论依据。 相似文献
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多自由度振动系统响应集的支撑超平面法 总被引:2,自引:0,他引:2
对激励由凸集合建模的线性振动系统提出了响应集的概念,将数学上的微分包含问题简化为求解多自由度振动系统的响应集问题。在此基础上,利用凸集的性质提出了一种求解响应集的支撑超平面法,它是利用响应集的支撑超平面将问题转化为求解一类优化问题的解。对于三种典型的凸集载荷分别给出了各自的响应集,并比较和分析了它们的结果。 相似文献
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This paper explores mechanical systems undergoing unilateral frictionless contact conditions in the framework of nonlinear modal analysis. The nonlinear eigenproblem is formulated in the frequency domain through the minimization of a Rayleigh quotient subject to non-penetration inequality constraints. An additional equality constraint is introduced for normalization purposes. The resulting constrained minimization problem is then solved using an augmented Lagrangian strategy. Two applications are proposed: a thin longitudinal rod in unilateral contact with a rigid obstacle and a turbomachinery compressor blade in contact with a rigid casing. The first application illustrates the complexity of the nonlinear modal characterization of a system experiencing unilateral contact conditions while the second demonstrates the applicability of the proposed approach to large-scale mechanical systems involving non-smooth nonlinear terms. 相似文献
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P. A. Roy S. A. Meguid 《International Journal of Mechanics and Materials in Design》2018,14(4):709-728
This study is concerned with an analytical solution for the nonlinear transient dynamic response of a rotating blade in a gas turbine engine experiencing dynamic unbalance due to a blade-off scenario leading to rotor unbalance. As a consequence of rotor unbalance, the blade experiences a pulsating load at its tip due to contact with the casing and a decaying centrifugal force field due to the rotor deceleration. The governing equations of motion consider the blade as an elastic Timoshenko beam of varying thickness subject to changing rotational speeds. The analysis takes into account the variation in the thickness of the beam, the coupled axial and lateral displacements of the beam as a result of Coriolis component of acceleration, shear deformation, rotary inertia, and friction resulting from the contact between the blade and the casing. Our findings indicate that the thickness profile of the beam plays a significant role in the transient response. It further reveals that the decaying centrifugal force field leads to a dramatic change in the dynamic response and the resulting forces on the blade. 相似文献
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发展了一种描述复杂运动状态下界面约束力的三维干摩擦接触数值模型,该模型通过在接触界面建立多个摩擦接触点对得到多点分布的界面约束力,可以描述界面的粘滞-滑动共存状态和法向接触正压力不均匀分布。在该模型中还考虑了界面动静摩擦系数的不同和界面的各向异性。采用三维干摩擦接触数值模型和高阶谐波平衡法,计算了某真实围带阻尼结构汽轮机叶片在复杂激励下的非线性振动响应。计算出叶片振动响应在一个运动周期出现多个局部极值,呈含多谐波的周期函数。 相似文献
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Dimitris L. Karabalis 《Engineering Analysis with Boundary Elements》1993,11(4):277-284
The formulation of a hybrid time domain BEM-FEM scheme is developed for the solution of three-dimensional dynamic soil-structure interaction problems involving contact nonlinearities at the soil-structure interface. Both uplift and sliding are considered at the interface through special thin-layer interface elements. The linear elastic structure, the geometrically nonlinear interface and the linear elastic soil medium are coupled together through equilibrium and compatibility and the analysis proceeds stepwise in time with iterations at each time step in order to define the contact area. Both external dynamic loads and seismic waves are considered. 相似文献
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A theory of high-speed cutting regimes involved in turning of materials has been developed. According to this theory, the
cut layer and the blade are considered as acoustic resonators coupled via a nonlinear contact stiffness and excited by the
lowest antisymmetric Lamb mode. The turning process is described in terms of a parametric oscillatory system. Using the proposed
theory, it is possible to determine optimum turning regimes. 相似文献
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Arif Masud Timothy J. Truster Lawrence A. Bergman 《International journal for numerical methods in engineering》2012,92(2):141-177
We present a derivation of a new interface formulation via a merger of continuous Galerkin and discontinuous Galerkin concepts, enhanced by the variational multiscale method. Developments herein provide treatment for the pure‐displacement form and mixed form of small deformation elasticity as applied to the solution of two problem classes: domain decomposition and contact mechanics with friction. The proposed framework seamlessly accommodates merger of different element types within subregions of the computational domain and nonmatching element faces along embedded interfaces. These features are retained in the treatment of multibody small deformation contact problems as well, where an unbiased treatment of the contact interface stands in contrast to classical master/slave constructs. Numerical results for problems in two and three spatial dimensions illustrate the robustness and versatility of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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分缝结构的非线性响应分析 总被引:3,自引:1,他引:2
本文给出了模拟结构分缝张开和闭合的有限元模型,该模型可以模拟缝面初始压力、抗拉强度的影响,且具有形成方便,适用范围广等优点;文中导出了非线性有限元的计算公式,编制了相应的非线性有限元程序,并对两个块体接触问题和一个分缝拱肋结构的非线性动力响应进行了计算,研究了不同接缝参数、不同初始压力及基座是否设缝对结构非线性响应的影响,给出了有关结论。 相似文献