《指数摩擦力模型振动系统的动态特性研究》

研究了单自由度滑动摩擦系数随相对速度指数变化的干摩擦振动系统简谐激励响应计算问题,应用等效线性化方法推导了相应的频响方程。通过数值分析,明确了各个系统参数对干摩擦系统振动的影响。     

基于微滑移模型的B-G型叶片干摩擦缘板阻尼器减振特性研究

在干摩擦接触面间引入弹性剪切层来模拟干摩擦接触,考虑摩擦接触界面在振动过程中可能经历完全粘滞、局部滑移、完全滑移三个阶段,提出一种改良的微滑移摩擦阻尼模型。在该阻尼模型基础上对摩擦力-位移迟滞曲线进行了仿真,得到了符合工程实际的迟滞曲线;分析了不同外力下接触面上的摩擦分布,揭示了微滑移模型的本质;利用一次谐波平衡与等效线性化相结合,研究多种参数对阻尼器等效刚度和等效阻尼及减振特性的影响,得到的减振规律为工程中该类阻尼器设计提供了指导。     

非恒定滑动摩擦系数振动系统等效线性化计算方法研究

研究了单自由度滑动摩擦系数随相对速度变化的干摩擦振动系统简谐激励响应计算问题 ,提出了等效线性化处理方法 ,并推导了相应的频响方程。通过一个数值例分析 ,考察了简化为理想干摩擦模型时带来的计算误差     

基于微动滑移摩擦模型的失谐叶盘系统振动分析

在航空发动机叶-盘系统中,由于叶片失谐导致严重的振动局部化,造成局部叶片的高周疲劳,拟采用增加叶根干摩擦的方法降低失谐叶-盘系统振动幅值,减轻其振动局部化程度。基于微动滑移摩擦模型建立叶根阻尼器干摩擦力本构关系,采用等效椭圆代替阻尼器力与位移函数关系的迟滞回线,获得阻尼器的等效阻尼、等效刚度;将等效阻尼、等效刚度作用于叶-盘系统集中参数模型上,建立单个扇区三自由度整周失谐叶-盘系统动力学方程;采用谐波平衡法对其进行振动特性分析,讨论了叶根干摩擦对失谐叶盘系统振动特性的影响。结果表明:叶根摩擦能显著降低系统共振幅值;有叶根摩擦系统较无叶根摩擦系统的共振峰在频率上延后;增加叶根摩擦可有效降低失谐叶-盘系统的振动局部化程度。     

救护直升机机载急救单元减振优化设计

针对某型救护直升机振动特点,采用金属干摩擦阻尼可调式隔振器对机载综合急救单元进行隔振优化设计,在隔振器干摩擦阻尼调节范围内,测试多组隔振器摩擦力曲线,应用谐波叠加法模拟直升机客舱底板激励,并通过仿真优化计算确定最佳摩擦力曲线,进而确定隔振器阻尼最佳工作状态。优化结果表明机载综合急救单元采用该型隔振器,能使加速度均方根响应降低78.75 %,说明该隔振器具有良好的隔振减振性能,适用于直升机机载振动环境。     

金属簧片阻尼隔振器性能分析

建立了金属簧片隔振器振动系统的动力学模型,通过有限元计算得出摩擦力曲线,进一步采用动力学方程研究了系统在简谐激励和冲击激励下的响应.结果表明:电子机柜采用该隔振器,能使最大加速度降低72%,说明该隔振器具有良好的减振隔振和抗冲击性能,为干摩擦隔振器优化设计提供了理论依据.     

Experiments and simulations of direct shear tests: porosity, contact friction and bulk friction

The direct shear testers, in particular the Jenike cell, are widely used to measure the bulk material properties for the design of bulk handling equipment. This paper describes a study of the Jenike shear tester using both experiments and discrete element simulations. A total of 90 tests on spherical glass beads and paired glass beads were performed to study the influence of the particle shape, stress level and packing density on the bulk friction at limiting shear. The data are thus useful for validating particle scale simulations of densely packed granular systems. In an attempt to verify the predictive capability of discrete element method, closely matching 3-dimensional discrete element simulations of the shear tests were performed and compared with the experimental observations. The comparison for single spheres shows good quantitative agreement for the limiting bulk friction when there is a good match in the sample porosity. Further research is needed to produce a comprehensive validation of the discrete element method. Several salient observations from this study provide further insight into the roles of particle shape and contact friction on the resulting packing porosity and bulk friction.     

具有调谐质量阻尼器(TMD)的干摩擦隔振系统的研究

本文基于增量谐波平衡（IHB）法研究了顶部装有TMD的干摩擦隔振系统及TMD对隔振性能的影响，进而在干摩擦隔振系统中引入了主动控制的概念，分析了主动控制对隔振系统性能的影响，为干摩擦隔振系统在工程上的应用提供了理论依据。     

变摩擦TMD特性和简谐激励控制效果的研究

提出一种变正压力式变摩擦装置,通过改变摩擦面正压力实现摩擦力随系统位移增大而增大。将其用于TMD能有效克服常摩擦TMD摩擦力不可变的缺点。采用一阶谐波平衡法推导了变摩擦系统的等效阻尼比和等效频率,分析了系统各参数对其等效阻尼比和等效频率的影响,通过与经典阻尼单自由度系统的比较探讨了单自由度变摩擦系统的频率响应特性。从理论和试验两个方面研究了简谐激励下变摩擦TMD对单自由度主结构振动控制的特点。分析结果表明,变摩擦TMD的频率响应特性与经典阻尼TMD类似,二者都能有效减小主结构频率响应曲线的峰值,试验结果验证了变摩擦TMD在简谐激励下的有效性     

干摩擦隔振系统稳态周期响应最优化计算方法

本文通过双折线泛函本构关系Foueier级数展开技巧及一次谐波平衡法与非线性方程组最优化解法相结合 ,提出了两自由度激振质量含有立方非线性粘性阻尼双线性滞迟振动系统简谐激励下稳态周期响应的迭代计算方法 ,数值分析结果表明该方法具有很高的计算精度 ,具有一定的工程应用价值     

考虑接触点摩擦的索滑移行为分析

连续索在接触点处滑移时会受接触点摩擦的影响,导致连续索在接触点两侧索力不相等。张拉连续索施加预应力时,接触点处的摩擦力使远离张拉端的索段预应力存在一定程度的损失。针对索在接触点处滑移时的摩擦问题,该文采用有限质点法,将连续索离散成相互联系的质点集合,质点间通过索单元连接,滑移索单元内力根据接触点力传递系数和索单元原长不变原则求解。该文推导了考虑接触点摩擦的滑移索单元内力求解公式,提出了索滑移判定准则,并给出了接触点力传递系数计算方法,通过自编程序对算例进行计算分析,验证了考虑接触点摩擦的滑移索单元的正确性和合理性。     

色噪声与确定性谐波联合激励下Bouc-Wen动力系统响应的统计线性化方法

提出了一种用于求解色噪声和确定性谐波联合作用下单自由度Bouc?Wen系统响应的统计线性化方法.基于系统响应可分解为确定性谐波和零均值随机分量之和的假定,将原滞回运动方程等效地化为两组耦合的且分别以确定性和随机动力响应为未知量的非线性微分方程.利用谐波平衡法求解确定性运动方程,利用统计线性化方法求解色噪声激励下的随机运...     

Effect of base roughness on size segregation in dry granular flows

This paper presents simulations of dry granular flows along a sloping channel using the discrete element method. The kinetic sieving and squeeze expulsion theories are utilized to study the effects of base roughness on size segregation and the underlying mechanisms. Basal friction has a significant influence on flowing regimes inside the granular body, and a larger base friction accelerates the size segregation process. The front zone of the granular body is more likely to be collision dominated with increasing base friction; as a result, the energy dissipated by frictional shearing decreases, and damping energy due to particles collisions is enhanced. Meanwhile, granular flows become much looser, and collisions between particles increase rapidly. It is shown that the differences in the kinetics among grains of mixed sizes and the mechanical effects of particle contacts can explain the mechanism of size segregation. The parameter representing the intensity of particles exchange also increases as base friction increases. The forces acting on particles are also affected by base friction. The dimensionless contact force describing the contribution of contact channel-normal stress increases as base friction increases, which indicates that a higher dispersive trend has developed inside the granular body.     

带凸肩叶片的稳态响应计算及其阻尼减振分析

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。     

高速摩擦制动界面振动信号时频法分析技术研究

利用MM-1000型摩擦制动试验机进行了高速摩擦制动试验,使用加速度传感器采集了摩擦制动过程中界面轴向与径向振动信号。利用Morlet小波变换对不同制动压力、干湿工况下的振动信号进行分析,结合摩擦制动过程中瞬时摩擦系数变化对高速摩擦制动界面振动行为时频法分析技术进行了研究。结果表明:重采样能够大幅减小计算量且对低频段振动时频分析无明显影响;Morlet小波时频分析比短时傅里叶变换和HHT边际谱具有更好的分辨率,对制动界面振动信号处理效果更好;时频图中的斜率与制动过程中的转速变化相对应,表明高速摩擦制动过程中转速基本呈线性降低;结合时频图与瞬时摩擦系数曲线可以评估高速摩擦制动过程中界面状况变化过程;振动能量主要集中在基频、二倍频和三倍频,超过三倍频部分能量较少。     

Contact between rolling beams and flat surfaces

This work presents a new approach to model the contact between a circular cross section beam and a flat surface. In a finite element environment, when working with beam elements in contact with surfaces, it is common to consider node or line to surface approaches for describing contact. An offset can be included in normal gap function due to beam cross section dimensions. Such a procedure can give good results in frictionless scenarios, but the friction effects are not usually properly treated. When friction plays a role (e.g., rolling problems or alternating rolling/sliding) more elaboration is necessary. It is proposed here a method that considers an offset not only in normal gap. The basic idea is to modify the classical definition of tangential gap function in order to include the effect of rigid body rotation that occurs in a rolling scenario and, furthermore, consider the moment of friction force. This paper presents the new gap function definition and also its consistent linearization for a direct implementation in a Newton‐Raphson method to solve nonlinear structural problems modeled using beam elements. The methodology can be generalized to any interaction involving elements with rotational degrees of freedom. Copyright © 2013 John Wiley & Sons, Ltd.     

Vibrations in systems with dry-friction damping elements

Forced vibrations of a mechanical system having one degree of freedom with dry and viscous friction are examined. It is established that dry friction acts as a filter that allows the passage of forced vibrations of a precisely determined frequency range in relation to the ratio of the disturbing force amplitude to amount of dry friction. Addition of viscous friction to dry friction narrows the vibration-passing sections of this filter.Translated from Problemy Prochnosti, No. 4, pp. 33–36, April, 1992.     

偏心轮叠层摩擦阻尼器的滞回性能研究

为解决常规摩擦阻尼器过大压力导致的一系列问题,设计一种新型偏心轮叠层摩擦阻尼器。该阻尼器以并联多层叠加的摩擦面的方法,实现在较小摩擦界面正压力条件下获得目标摩擦阻尼力的目的;设置偏心轮加压装置,使得阻尼器实现变摩擦功能,且阻尼器摩擦面在服役期间的待命阶段的预压力为0,以提高阻尼器的可靠性,进一步解决过大压力的问题。通过往复加载试验对该阻尼器的性能进行了研究,获得了偏心轮叠层摩擦阻尼器阻尼力与位移的关系,并对偏心轮叠层摩擦阻尼器力学性能进行了有限元分析。结果表明:阻尼器摩擦板的叠层设计能够有效放大了摩擦阻尼力;偏心轮叠层摩擦阻尼器可以提供变摩擦滞回曲线,理论公式、有限元模拟结果与试验结果吻合较好,可作为该阻尼器设计的参考依据。     

干摩擦阻尼叶片的界面约束力描述及振动响应求解

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。     

Stochastic analysis of nonlinear vehicle systems using a generalized harmonic linearization technique

The discrete harmonic linearization method which is applicable to stochastic systems could not provide an equivalent stiffness coefficient for a nonlinear restoring element. In this paper, this technique is generalized to obtain linear representations of both nonlinear restoring and damping elements, based on a principle of energy similarity of dynamic elements. A numerical iterative procedure is presented to compute the local linear coefficients of nonlinear dynamic elements. A nonlinear system is then represented by a set of its complex frequency response function matrices, as functions of the excitation frequency. Stochastic analysis of general multi-DOF nonlinear vehicle systems is established in terms of response PSD characteristics.