部分柔顺翅翼机构及其动力学分析

提出将包含"固定-铰接"的柔顺片段的部分柔顺机构作为微扑翼飞行器的翅翼机构。在简要介绍刚性、含弹簧和部分柔顺三种翅翼机构的结构和特点之后,利用伪刚体法对部分柔顺翅翼机构进行了动态静力分析,并将结果与相同条件下刚性及含弹簧的翅翼机构进行了比较。研究表明部分柔顺和含弹簧的翅翼机构都能明显地减小刚性翅翼机构的运动副反力和平衡力矩的峰值,而在一周期内部分柔顺翅翼机构运动副反力和平衡力矩的平均值比含弹簧翅翼机构的平均值的要小。通过验证,这些结论在不同的曲柄转速下是相同的。     

Further developments on the estimation of rigid body properties from experimental data

The evaluation of the rigid body properties of a structure is a very important issue for the study of its dynamic behaviour when the influence of the rigid body modes is considerably significant.Various approaches exist for this purpose. In the present work the authors explore a particular group of methods where ten rigid body properties are estimated from modal information extracted from Frequency Response Data (FRF) measured on structures. This kind of methods, usually known as modal methods, use the identified modal properties associated to the rigid body modes and their orthogonality properties. However, some difficulties have been reported in cases when a high degree of symmetry exists in the structure, when double modes appear or when it is not possible to excite all the six rigid body modes. New improvements and methodologies are proposed to help solving such situations.     

Frequencies of circular plate with concentric ring and elastic edge support

Exact solutions for the flexural vibrations of circular plates having elastic edge conditions along with rigid concentric ring support have been presented in this paper. Values of frequency parameter for the considered circular plate are computed for different sets of values of elastic rotational and translation restraints and the radius of internal rigid ring support. The results for the first three modes of plate vibrations are computed and are presented in tabular form. The effects of rotational and linear restraints and the radius of the rigid ring support on the vibration behavior of circular plates are studied over a wide range of non-dimensional parametric values. The values of the exact frequency parameter presented in this paper for varying values of restraint parameters and the radius of the rigid ring support can better serve in design and as benchmark solutions to validate the numerical methods obtained by using other methods of solution.     

回转梁动力学方程求解的数值方法研究

考虑驱动力矩、重力、哥氏力、运动阻力和惯性耦合力,根据考虑横向弯曲变形的Euler-Bemoulli细梁模型,并考虑离心力作用下的拉伸变形,建立回转运动梁的动力学模型。将梁根部的回转角度分解为整体刚性运动回转角度和刚体运动和柔性运动激发刚柔耦合回转角。将梁的柔性振动位移也分解为由整体刚性回转角所激发的动力激励振动和刚柔耦合回转角运动及刚柔耦合项共同激发的刚柔耦合振动。整体刚性回转角和动力激励振动,通过数值方法(如龙格-库塔法)求解,而将刚柔耦合回转角和刚柔耦合振动,通过奇异摄动法求解。通过数值方法和奇异摄动法相结合的方法,能够正确计算刚柔耦合回转角及其对梁振动位移的影响,更精确、深入地分析回转梁的动力学特性。     

有限刚体元方法在微扑翼飞行器翅翼动力分析中的应用

仿生微扑翼飞行器的翅翼具有较大的柔性,并有较大的变形。寻求一种翅翼动力分析的方便、有效的方法是翅翼机构设计和分析的关键问题之一。将有限刚体元(Rigid Finite Element)方法应用于翅翼的动力分析,包括一般有限刚体元方法和改进的有限刚体元方法。研究表明,当翅翼的分段数目达到一定数目的时候,有限刚体元方法的计算结果与采用有限元方法的计算结果相差不大,而前者具有简单、方便、省时的优点。     

Formulae for the squeeze film between a rigid cylinder and a thin elastic layer with sinusoidal waviness

A set of formulae for the variation of the film thickness with time when a rigid cylinder approaching a thin elastic layer with sinusoidal waviness is derived. The shapes of the solids are assumed to be the same as the elastically deformed surfaces under dry conditions. Two geometrical configurations are investigated. First, the layer is resting without friction on a rigid substrate (unbonded layer). Second, the layer is attached firmly to a rigid substrate (bonded layer). The obtained results showed a good agreement with those reported for a smooth bonded layer.     

基于刚柔耦合与联合仿真的AUV发动机动力学研究

结合多刚体动力学和多柔体动力学理论,建立自主式水下航行器发动机中相关柔性体的刚柔耦合运动学、动力学数学模型;在ADAMS中生成虚拟样机,在Matlab／Simulink中建立发动机控制模型,然后基于ADAMS／Control模块与Matlab／Simulink接口得到发动机多刚体联合仿真模型,并利用相关实车数据对其进行了验证;在ANSYS软件中生成柔性体有限元模态中性文件,导入多刚体联合仿真模型,得到刚柔耦舍的联合仿真模型。     

Some applications of electrical network analogues to the elastic analysis of rigid frames

Simple electric analogues are described, which are suitable for the determination of the secondary moments developed in rigid triangulated frames, and also for the analysis of rigid space frames.     

Crushing of thin-walled spheres and sphere arrays

Due to its ideal material properties and very small but uniform wall thickness, ping pong balls are selected to study the plastic crushing behavior of thin-walled spheres and sphere arrays. In experiments, single spheres were compressed by point-load, rigid ball, rigid plate, rigid cap or double rigid balls. A number of bifurcation phenomena are identified and their effect on the crushing force is illustrated. It is noted that when two ping pong balls compress each other, the snap-through deformation randomly occurred in one of the balls while the other one remained undeformed or only deformed elastically. This fact allows us to conveniently employ a single ball's load-deformation relation for predicting the 1-D or 2-D array's load-deformation behavior. A very good agreement between the prediction and the experimental result is shown. If the ping pong balls are connected, the connection part, which can be simulated by a rigid cap, transforms the ball from a type I to a type II structure. Thus, when compressing a 1-D array of connected balls, the deformation will be localized in a ball until the force increases to a certain value, which crushes the next ball. Such a crushing force depends on the size of the connection part, as demonstrated in the case of compression by a rigid cap.     

The elastohydrodynamic lubrication of a cylinder on an elastomeric layer

In this paper the lubrication of a rigid cylinder sliding or rolling on an elastomeric layer which is bonded to a rigid substrate is examined. Results are presented for central and minimum film thicknesses for the complete range of operating conditions and for a wide range of values of the ratio of the semicontact width-to-layer thickness.     

Structural optimization of typical rigid links in a parallel kinematic machine

The motion dynamics and accuracy of parallel kinematic machines largely depend on the weights and rigidity of typical rigid links. Therefore, these parts should be designed in such a way that they are light but rigid. This work employs the techniques of topology and size optimization to design two typical rigid links of a parallel kinematic machine (PKM) and subsequently obtains applicable structures for them. The calculation models are established, and a new algorithm called the Guide-Weight method is introduced to solve topology optimization problems. The commercial software Ansys is used to perform size optimization.     

Contact problems for the thin elastic layer

Simple approximate solutions due to Jaffar and Johnson for the indentation by a rigid frictionless punch of a thin elastic layer on a rigid foundation are extended to the corresponding general three-dimensional problem. Results are given for the case where an incompressible layer is indented by an ellipsoidal punch and an analogy is demonstrated between the flat punch problem with arbitrary plan-form and the St Venant torsion problem.     

基于拉格朗日乘子法的Delta并联机器人简化刚体动力学建模方法

针对广泛应用于高速抓放操作的Delta并联机器人,提出了一种基于拉格朗日乘子法的刚体动力学建模方法,并利用约束方程的全微分求解出了动力学模型的显示表达式。建立了机器人的逆运动学以及刚体动力学模型,考虑机器人从动臂臂杆为轻质碳纤维杆,两端为较重的金属附件的特点,建立了简化刚体动力学模型。并针对机器人常用的高速抓放轨迹进行仿真,将简化前后的2种动力学模型与ADAMS仿真结果进行对比。     

硬脆材料磨削加工机理的理论分析

通过对硬脆材料 (玻璃 )的切削试验 ,建立了硬脆材料的磨削模型 ,讨论了硬脆材料在磨粒作用下的塑性变形和断裂行为     

三坐标测量机非刚性误差的分析与补偿

根据移动桥式三坐标测量机非刚性效应测量误差的分布特征 ,通过对坐标测量机构件进行受力变形分析与建模 ,对坐标测量机的非刚性效应测量误差进行了分析 ,为高精度坐标测量机的误差补偿技术提供了新的思路     

计及二阶效应的刚柔耦合连杆系统动力学分析

根据虚功原理和达郎伯原理推导了计及二阶效应的柔性单元运动方程,并利用刚化条件得到了刚性梁单元运动方程,给出了刚柔耦合连杆系统动力学建模与分析的方法.对构件刚度相差悬殊的多体系统进行动力学分析时,如若当作多刚体系统分析,会因忽略弹性变形导致结果不准确;当作多柔体系统建模分析求解,则因自由度太多导致方程庞大难求解.可行的方法是:将刚性单元与柔性单元耦合建模,在多柔体系统基础上,引入刚性单元和刚性约束条件,对刚性构件自身的动力学特性进行等效,然后按照一般弹性系统有限元方法集成得到虚拟柔性系统动力学方程,建立过渡坐标与广义坐标关系,消除非独立坐标,得到真实的系统运动方程,降低系统方程维数,提高分析效率.以曲柄滑块机构为例,介绍了计及二阶效应的刚柔耦合系统动力学的建模分析过程.     

The Isothermal Lubrication of Cylinders

When the hydrodynamic problem of cylinder lubrication is considered, two distinct types of solution emerge. For light loads the cylinders retain their unloaded geometry; the Martin solution for this condition is well known. When the contact forces are large, significant elastic deformation may occur; the resulting elastohydrodynamic regime has been extensively analyzed in recent years.

Equations are now available for the calculation of minimum film thickness in the “rigid” and “elastic” situations. In this paper computing methods appropriate to each range of conditions are summarized, and the nature of the solutions is considered in some detail. In particular the valid range of application of the “rigid” and “elastic” film thickness relationships is discussed. An intermediate range of conditions between the “rigid” and “elastic” regimes is defined.

Finally, a chart is presented to enable a particular problem to be located in the “rigid,” “intermediate,” or “elastic” zones.     

基于刚柔耦合模型的工程车辆转向机构设计研究

应用多体系统动力学方法对SGA3550矿用汽车转向机构进行设计研究。首先,应用有限元软件建立转向横拉杆的柔性体模型,并得到其固有模态和振型;其次,结合ADAMS软件建立车辆的刚柔耦合模型;最后,对比分析多刚体模型和刚柔耦合模型的动力学特征,包括转向过程中的车轮转角、直线行驶时的轮距和车轮反向跳动过程中的车轮摆角。结果表明,刚柔耦合模型更为准确地反映了车辆的动力学特征,为转向机构设计提供了更为准确的依据。     

The use of moiré techniques to measure rigid body displacements

The relative advantages and disadvantages of a variety of experimental electron microscopical techniques for the measurement of rigid body displacements are considered. The principles of the application of a moiré method of great simplicity and high potential accuracy are then further discussed as are the experimental difficulties associated with the superposition of suitable reference latices on a substrate. The method is then applied to obtain an upper limit for the rigid body displacement at {111} Σ3 twin boundaries in stainless steel.