转子系统非线性动力学DEM建模研究

THE STUDY OF NONLINEAR DYNAMICS DEM MODELING OF ROTOR SYSTEMS

将ＤＥＭ方法引入转子系统非线性动力学的分析计算，对其建模过程和有关本构关系，作了比较详尽的介绍．该模型可用于碰摩、弯曲振动和扭转振动等转子系统的大部分动力学和运动学问题分析计算，不仅适用于单跨转子系统，也适用于多跨转子系统，尤其是在碰摩计算时，可考虑其摩擦特性随时间历程而变的特点，从而使分析计算更加接近实际情况．

A rotor system consists of rotors, bearings, oil film, supports and other parts, which can get in touch with the rotors in motion. As we know, abnormal vibration in a rotor system can often cause severe accidents. Since H. H. Jeffcott began to study dynamic behaviors of rotor system by using a single-disk deflective rotor model in the earlier of 20th centuxy, how to set up the dynamic model of a rotor system is always one of the problems to which are paid the most attention. It's no doubt now that many nonlinear factors act much influence on the local and global dynamic characteristics of a rotor system. For example, if deflective deformation or whirling amplitude of a rotor surpasses certain value in procession, some of its parts will come into contact with and impact those adjacent ones, which is habitually called 'rub-impacting'. As concerned with many complicated factors, continual rub-impacting will lead to energy transfer and accumulation from rotation to elastic deformation, and it even may cause the rotor's sudden break away However, they are just those factors which make theory study and numerical simulation on rub-impacting difficult to deal with, especially about setting up its dynamic model. One of those factors is that the following characteristic of a rotor system are decided by a series of initial conditions such as occurrence of rub-impacting or rub-impacting force and friction force and relations between them, and so on. Another is that the rotor sometimes contact and sometimes departs with other adjacent parts, making occurrence of rub-impacting random and difficult to decide. In spite of a lot of present research on rub-impacting none doesn't need further study including study of nonlinear method. Therefore, we attempt to make some further research on complicated dynamic behavior of rotor system by building a better dynamic model through Discrete Element Method (DEM). In this paper the DEM is introduced for investigation of nonlinear dynamical behavior of rotor systems. The modeling procedure and constitutive relations were explained in detail. This model may be used for most of dynamical problems of rotor systems, such as rub-impacting, bending vibration and tensional vibration etc. Especially it is suitable for studying the rub-impacting problem of rotor system because of considering variable characteristic of friction force with time. After a great deal of calculation on the DEM model of rotor system built in this paper we fined that our results are in accordance to the experimental results from [16] in nature, it is said that DEM is suitable for calculation on rotor system and our model is reliable. With our DEM model, one can calculate most kinds of complicated dynamic behaviors of a rotor system with many nonlinear factors without limitation of DOF. Therefore, calculation results on a rotor system with DEM model of will be more creditable.