超高速磨削用液体动静压轴承支撑特性分析

发布时间：2018-02-09 15:30

本文关键词： 超高速磨削主轴系统动静压轴承 CFD分析模态分析　出处：《东北大学》2012年硕士论文　论文类型：学位论文

【摘要】：超高速磨削是二十世纪八十年代发展起来的一种高新磨削加工技术,自面世以来,该技术就受到了国内外学术界和制造业的极大关注。与传统的磨削加工相比,超高速磨削加工在提高生产率,减少产品在磨削加工过程中的热变形、热应力、减轻磨削力、减轻和消除加工设备和磨具在加工过程中的振动,以及实现高精度、高质量零件的加工等诸多方面具有明显的优势。超高速磨床所能达到的最高磨削速度极限很大程度取决于主轴单元的性能,而轴承的性能也是至关重要。液体动静压轴承,综合了静压轴承和动压轴承的特点,具有磨损小、承载能力大、使用寿命长、速度范围宽、动态特性好以及刚度高等突出优点,在超高速磨削机床上的得到了广泛的应用。研究动静压轴承的支撑性能具有实际的应用意义。一方面,轴承的承载力和刚度直接影响机床的加工精度及工作的稳定性；另一方面,随着转速的进一步提高,轴承的发热量增大,油膜的不稳定性提高,易造成“抱轴”、“刮轴”等恶性事故。鉴于此本文对液体动静压轴承及主轴系统做了如下研究： (1)针对超高速磨削用液体动静压轴承承载的复杂性,应用计算流体力学软件FLUENT对超高速磨削用五腔动静压轴承进行了动态特性研究,得到了动静压轴承内部压力场分布,然后进一步计算了轴承的承载力、温度、刚度、阻尼等动态参数,并进一步分析了这些动态参数与偏心率以及转速之间的关系,即,在保持供油压力和轴承偏心率不变的情况下,随着转速的提高,油温上升,轴承承载力及偏位角不断增大；在保持供油压力和主轴转速不变的情况下,随着偏心率的增大,轴承流量有所减少,轴承的承载能力不断增大,偏位角基本保持不变。 (2)针对液体动静压轴承温升机理的复杂性,应用FLUENT对油膜的热特性进行了CFD(计算流体力学)分析,获得了不同输入状态下的油膜温度场分布,并在此基础上得出了油膜温度特性随输入参数变化的规律,分析表明：油膜温升与转速和偏心率为正比例超线性关系,与供油压力为反比例关系,与供油温度为近似正比例线性关系。最后运用正交试验,分析了各输入参数的显著性,结果表明：主轴转速对温升的影响最显著。 (3)针对液体动静压轴承支撑的超高速磨削主轴系统工作的特殊性,考虑到主轴旋转速度高及液体动静压轴承的变刚度支撑,应用有限元分析软件ANSYS建立了超高速磨床主轴系统的三维有限元模型,并对其进行模态分析,得到了各阶固有频率及振型。最后通过设置不同转速下轴承的支撑刚度,获得了主轴系统模态分析结果,并利用图解法求解出主轴系统的临界转速。分析结果表明：主轴系统在高速旋转状态下,系统的结构刚度会发生变化,使得主轴系统的固有频率发生改变,并且随着转速提高差异越显著。 (4)应用动态信号分析仪对超高速磨床主轴系统进行了振动测试,获得了主轴系统的各阶固有频率,并对比了仿真分析结果,验证了主轴系统有限元分析的准确性和可行性,以及CFD分析获得的动静压轴承动态特性参数的可靠性,并分析了产生误差的原因。
[Abstract]:Ultra high speed grinding is a new grinding technology developed in the 1980s, since the launch, the technology has attracted great attention in academic circles at home and abroad and manufacturing industry. Compared with the traditional grinding, ultra-high speed grinding process can increase the productivity, reduce the product in the grinding process of the thermal deformation and thermal stress force, grinding force is reduced, to reduce and eliminate the vibration processing equipment and tools in the machining process, and achieve high precision, has the advantage of high quality parts processing and other aspects.
The performance of ultra high speed grinding machine can achieve the highest grinding speed limit depends on the spindle, and the bearing performance is also very important. The liquid hybrid bearing, the comprehensive characteristics of hydrostatic bearing and hydrodynamic bearing, has small abrasion, large bearing capacity, long service life, wide speed range, and good dynamic characteristics stiffness advantages in ultra high speed grinding machine has been widely used. The significance of application of supporting performance of hydrostatic bearing has practical. On the one hand, the bearing capacity and stiffness of the bearing directly affects the machining precision and working stability of machine tool; on the other hand, with the increase of speed, fever the increase of bearing capacity, improve the oil film instability caused by "axle", "scraping axis" and other accidents. In view of this paper of hybrid bearing spindle system and do the following research:
(1) according to the complexity of ultra high speed grinding with liquid hydrostatic bearing, the computational fluid dynamics software FLUENT for ultra high speed grinding with five cavity bearing the dynamic characteristics of research, has been bearing the internal pressure distribution, and then further calculated the bearing capacity, bearing temperature, stiffness, damping etc. the dynamic parameters, and further analysis of the relationship between these parameters and the dynamic eccentricity ratio and speed, while maintaining the supply pressure and bearing eccentricity is constant, with the increase of rotational speed, oil temperature rise, and the offset angle of increasing bearing force; while maintaining the supply pressure and spindle speed unchanged. With the increase of eccentricity, bearing flow decrease, the bearing capacity is increasing, the deviation angle remained basically unchanged.
(2) according to the complexity of the liquid hybrid bearing temperature rise mechanism, thermal characteristics of FLUENT application on the oil film of CFD (Computational Fluid Dynamics) analysis, oil film temperature distribution in different input state are obtained and analyzed and based on the temperature characteristics of the oil film with the input parameters of the law, show that with the speed and eccentricity ratio is super linear relationship between oil film temperature rise, and the oil pressure is inversely proportional to temperature, and the oil was nearly proportional linear relationship. Finally using orthogonal test, significance, analysis of the input parameters. The results showed that the most significant effect of spindle speed on the temperature rise.
(3) according to the particularity of the liquid hybrid bearing support of ultra high speed grinding spindle system, taking into account the high spindle rotation speed and liquid hydrostatic bearing variable stiffness support, finite element analysis software ANSYS was used to establish a three-dimensional finite element model of ultra high speed spindle system, and carries on the modal analysis. Get the natural frequency and vibration mode. Finally, by setting the different speed of bearing support stiffness, the spindle system modal analysis results, and the use of the graphic method of critical speed of the spindle system. Analysis results show that the spindle system under high rotation speed, the system stiffness of the structure will change, so the natural frequency of the spindle system is changed, and with the rotational speed difference is more obvious.
(4) the application of dynamic signal analyzer of vibration test on super high speed grinder spindle system, obtained the natural frequency of the spindle system, and compared the simulation results, verify the accuracy and feasibility of the spindle system of finite element analysis, and reliability analysis for CFD dynamic static pressure bearing dynamic characteristics parameters, and analysis the cause of the error.

【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TG580.23;TH133.3

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