动力减振镗杆系统的非线性动力学特性研究

发布时间：2018-12-15 22:09

【摘要】：随着机械制造工业的快速发展,对工件加工精度的要求越来越高。高速镗削产生的振动降低了加工精度和切削效率,振动引起的噪音严重危害工人的身心健康。本文考虑减振镗杆系统中橡胶圈和阻尼液的非线性因素分别建立了两自由度内置式动力减振镗杆系统模型和三自由度双内置式动力减振镗杆系统模型,基于非线性振动理论,数值计算系统分岔图、Poincaré映射图、PSP图、安全盆和吸引域等,研究了系统动力学参数对系统振动特性的影响、系统振动安全盆对初值的敏感性以及系统局部和全局动力学稳定性,为减振镗杆系统的设计和参数优化提供依据。具体研究内容如下:建立了两自由度动力减振镗杆系统的离散动力学模型,计算了阻尼液的阻尼系数和非线性阻尼力,给出了橡胶圈的非线性弹簧力,得到一个包含橡胶圈和阻尼液非线性项的动力减振镗杆振动方程。针对两自由度动力减振镗杆系统,选择不同的动力学系统参数,借助数值计算方法,研究各动力学参数对系统分岔和混沌特性的影响。研究发现,外激励频率在0.5倍频附近时幅值突然急剧增加,出现强共振响应,系统振动瞬间失稳。当外激励频率大于主倍频后,系统出现稳定周期1运动和拟周期运动相交替的现象。当橡胶圈弹性系数、阻尼液阻尼系数、减振块质量较小时系统出现了鞍结分岔、Hopf分岔以及环面倍化分岔等较为复杂的分岔特性;当橡胶圈弹性系数、阻尼液阻尼系数、减振块质量较大时系统振动较为稳定,但并非稳定的周期运动,而是周期运动和拟周期运动交替出现。研究发现在减振块尺寸一定的条件下,其质量大于0.5倍的主系统质量时,系统振动稳定性增强,故在实际应用中,通过选用密度较大的质量块可以有效抑制减振镗杆的振动。通过计算系统的安全盆研究了两自由度减振镗杆系统振动的安全特性。分析了随外激励频率和阻尼液系数变化时系统安全盆的侵蚀过程。发现随系统参数的变化系统安全盆受到不同程度的侵蚀。为了分析系统振动对初值的敏感性,数值计算了系统各吸引子的吸引域,对系统的局部及全局动力学特性进行稳定性分析,研究发现随动力学参数的变化,系统出现了周期运动与周期运动、周期运动与混沌运动等多种稳态解共存的现象。建立了考虑橡胶圈和阻尼液非线性因素的三自由度内置式双减振镗杆系统的非线性动力学模型,通过计算得到系统的力学参数。研究外激励频率、橡胶圈刚度、减振块质量、阻尼液等对系统动力学特性的影响以及吸引子共存情况。
[Abstract]:With the rapid development of machinery manufacturing industry, the requirement of machining precision of workpiece is more and more high. The vibration caused by high speed boring reduces machining precision and cutting efficiency, and the noise caused by vibration seriously harms workers' physical and mental health. In this paper, considering the nonlinear factors of rubber ring and damping fluid in the vibration absorption and boring bar system, the model of two degree of freedom built-in dynamic vibration absorption boring bar system and the three degree of freedom double internal dynamic vibration absorption boring bar system model are established, respectively, based on the nonlinear vibration theory. The system bifurcation diagram, Poincar 茅 map diagram, PSP diagram, safe basin and attraction region are calculated numerically. The effects of system dynamic parameters on the vibration characteristics of the system are studied. The sensitivity of the system vibration safety basin to the initial value and the local and global dynamic stability of the system provide the basis for the design and parameter optimization of the vibration absorption boring bar system. The main contents are as follows: the discrete dynamic model of two degrees of freedom dynamic vibration absorption boring bar system is established, the damping coefficient and nonlinear damping force of damping fluid are calculated, and the nonlinear spring force of rubber ring is given. A vibration equation of dynamic vibration absorption boring bar with nonlinear term of rubber ring and damping fluid is obtained. Different parameters of dynamic system are selected for two-degree-of-freedom dynamic vibration absorption boring bar system. The effects of dynamic parameters on bifurcation and chaos characteristics of the system are studied by means of numerical calculation method. It is found that when the external excitation frequency is close to 0.5 times frequency, the amplitude increases sharply, the strong resonance response occurs, and the vibration of the system is transient unstable. When the external excitation frequency is larger than the principal frequency doubling, the stable periodic 1 motion and the quasi periodic motion alternately occur in the system. When the elastic coefficient of rubber ring, damping coefficient of damping fluid and mass of damping block are small, the saddle node bifurcation, Hopf bifurcation and torus doubling bifurcation appear. When the elastic coefficient of rubber ring, damping coefficient of damping fluid and mass of damping block are larger, the vibration of the system is more stable, but not a stable periodic motion, but alternate between periodic motion and quasi-periodic motion. It is found that the vibration stability of the system is enhanced when the mass of the main system is more than 0.5 times under the condition of the certain size of the damping block, so it is applied in practice. The vibration of the boring bar can be effectively suppressed by selecting the mass block with high density. The safety characteristics of vibration of two degrees of freedom damping boring bar system are studied by calculating the safety basin of the system. The erosion process of the safe basin is analyzed with the change of external excitation frequency and damping fluid coefficient. It is found that the system safety basin is eroded in varying degrees with the variation of system parameters. In order to analyze the sensitivity of the system vibration to the initial value, the attraction regions of the system attractors are numerically calculated, and the stability of the local and global dynamic characteristics of the system is analyzed. It is found that the stability of the system varies with the dynamic parameters. Periodic motion and periodic motion, periodic motion and chaotic motion coexist in the system. The nonlinear dynamic model of a three-degree-of-freedom built-in double-damping boring bar system considering the nonlinear factors of rubber ring and damping fluid is established. The mechanical parameters of the system are obtained by calculation. The effects of external excitation frequency, stiffness of rubber ring, mass of damping block and damping liquid on the dynamic characteristics of the system and the coexistence of attractors are studied.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG53

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