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1.
The dynamic characteristics of joint interfaces affect the dynamic behaviors of a whole machine tool structure notably. An analytic method of virtual material hypothesis-based dynamic modeling on fixed joint interface in machine tools was conducted so as to improve the modeling accuracy of whole machine tools. The microcontact part of two contact surfaces in fixed joint interface was assumed as a virtual isotropic material, which is rigidly connected with two components composing fixed joint interface. The interaction between normal and tangential characteristics of fixed interface was taken into account, a set of analytic solutions of elastic modulus, shear modulus, Poisson ratio and density was deduced from virtual material by adopting Hertz contact theory and fractal theory. Using the finite element structural dynamic modeling approach in existence, when some parameters of material’s elastic modulus, Poisson ratio, density, etc. are known, the dynamic model for virtual material composing a component could be established; therefore, the dynamic model for whole structure, including joint interface, would be obtained. The theoretical mode shapes were compared with the experimental ones (qualitative comparison of similar mode shape and quantitative comparison of the corresponding natural frequency). The comparison results show that the theoretical mode shapes are in excellent agreement with the experimental ones. The relative errors between the theoretical natural frequencies and the experimental ones are less than 9%. The good agreements of theoretical results with experimental ones confirm analytic solutions for virtual material’s parameters. The present solutions would be useful to the precise dynamic modeling of fixed joint interfaces in CNC machine tools in practice.  相似文献
2.
具有弹性连接的组合机身压力机振动分析   总被引:1,自引:0,他引:1  
针对组合机身压力机的结构特点 ,采用自由界面模态综合法进行振动分析 ,为使计算模型符合由拉紧螺栓实现各组合部件间弹性连接的实际结构 ,形成了弹性连接刚度阵 ,并对相关结构的刚度阵进行了修正 ,用该模型对一新型双击式螺旋压力机进行了计算 ,计算得到的固有频率与实测值相符。  相似文献
3.
基于有限元法的码垛机器人模态分析   总被引:1,自引:0,他引:1  
介绍了码垛机器人的设计原理和总体结构.利用有限元分析软件COMSOL,以模态分析为理论基础,建立了码垛机器人的有限元模型,选择了码垛机器人3种典型的位姿,并对各阶固有频率进行了分析,得出各阶固有频率下的模态振型.结果表明:各种位姿的机器人的前六阶固有频率集中在15~ 130 Hz之间;小臂和前后大臂是主要的动态特性影响因素,可以通过适当的增加壁厚或者提高材料的刚度来进行改进;整个机器人的固有频率较低,可以通过优化手臂平行四边形机构来提高整体结构的刚度,从而提高机器的固有频率,改善其振动特性.  相似文献
4.
本文主要研究桥式起重机结构参数固定时,外部各参数对起重机动态性能的影响。以及起重机在作业过程中应注意的问题。  相似文献
5.
本文详细推导了在液压伺服系统中采用对称型液压缸经简化了的传递函数,并给出了相应的阀控液压缸和连铸机结晶器液压振动系统的方框图,对两腔面积比为21的非对称型液压缸与对称型液压缸相比,前者的阀的流量放大系数和压力流量系数均降低了0.05倍.本文还对某一实际采用的连铸机结晶器液压振动系统的主要参数如液压刚度、液压固有频率、液压阻尼比、阀的最大速度增益、阀压降等进行了详细地数值分析和计算,由于非对称型液压缸一系列固有特点在液压伺服系统中获得了广泛应用.  相似文献
6.
A technique based on measurement of change of natural frequencies has been employed to detect multiple cracks in long pipes containing fluid at different pressures. The cracks have straight fronts and are non-leaking. Both theoretical and experimental results are presented. Two different materials, aluminium and mild steel, have been examined. The fluid considered is water; three (gauge) pressures in the range 0–981 kPa, and crack size to thickness ratio in the range 0.19–0.64 are studied. Two simultaneous cracks are considered in the experiments. The crack locations are predicted with an error less than 4.3%. Results on crack-equivalent rotational spring stiffness, which can be useful in the calculation of natural frequencies and crack size predictions, are reported.  相似文献
7.
A systematic procedure is proposed to predict the dynamic behaviours of a whole machine-tool structure. The prediction procedure makes use of a receptance synthesis method, in which the dynamic model is composed of the elements such as the distributed-mass beam, the lumped mass and the joint. As an example, the dynamic characteristics of a guideway joint are analysed through the use of the dynamic fundamental characteristic parameters of joint surfaces at unit area obtained by experiments. The software to predict the dynamic behaviours of a whole machining tool structure is developed based upon the procedure. To demonstrate the utility of the proposed procedure and the developed software, the dynamic modeling of a whole machining centre structure has been established and its natural frequencies are calculated by the software. The dynamic test for the whole machining centre showed that the procedure and the software is valid to predict dynamic behaviours of a whole machine-tool structure at its design stage.  相似文献
8.
提出在高压大流量液压系统中提高速度和减少液压冲击振动所采取的措施;对提高液压元件使用寿命阐述了一些看法;将比例控制技术应用到大型热加工生产线中,使机械手的运动既快又平稳,达到了设计的预期效果。  相似文献
9.
对单自由度系统,其静刚度与固有频率的平方有正比关系。复杂机械结构的静、动刚度与结构的布局有关,但对其某一低阶固有频率和该方向的静刚度,适用上述结论。故通过提高结构的固有频率,可同时改善结构静、动刚度。有限元分析(FEA)方法应用于结构的静、动态设计中,可大大提高结构设计效率。以一数控机床滑座结构为实例,基于结构静、动刚度的关系和FEA方法,对结构进行了改进,使滑座重量减少一半的同时,提高了其结构的静、动态特性。  相似文献
10.
于今  闵为 《机床与液压》2006,(7):165-166,235
液压系统的管路动态特性分析是一个非常复杂的问题,特别是对于复杂的管路系统。本文针对轻轨换轮装置液压缸前的管道偶尔产生强烈振动的现象,采用传递矩阵方法对液压管路和油缸的振动特性建立了数学模型,并在MATLAB中进行了仿真,结果表明预先增大油缸中的充油容积、增大油液粘度、减小管道直径可避免此现象的发生。  相似文献
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