【作者】 闫俊霞；

【导师】 刘初升；

【作者基本信息】 中国矿业大学 ， 机械设计及理论， 2011， 博士

【摘要】 大型化、高速化和轻型化是振动筛分设备发展的主要趋势。在满足振动筛的大处理量和高工作效率的同时,保证振动筛结构的强度和刚度是实现振动筛大型化和高速化的关键问题。本课题以抑制振动筛的弹性振动为研究目标,采用对振动筛横梁添加多余约束的方法实现应力集中的弱化和能量的均匀分布,从而保证振动筛在不改变整体质量的前提下提高强度和刚度,为高速大型振动筛的设计提供一种新思路。本课题首先对直线振动筛进行了多余约束设计。在保证其横梁质量和转动惯量不变的前提下,设计出了多余约束结构横梁,并建立了多余约束振动筛的力学模型。在此基础上,建立了静定横梁振动筛和多余约束横梁结构振动筛的有限元模型。对多余约束横梁结构振动筛和静定横梁振动筛有限模型进行了动力学特性分析。分别提取了两种模型的前10阶的固有频率、模态振型和工作频率下的动应力响应。结果表明,多余约束横梁结构振动筛的动应力和变形比静定横梁振动筛有明显下降,整体的刚度和强度比静定横梁振动筛有明显提高。该课题还基于功率流理论研究了多余约束结构对弹性振动的抑制机理。采用基于Ritz级数法的模态功率流方法分析了多余约束横梁和静定横梁内部的能量分布。结果表明:多余约束横梁在整段梁上都有能量波动,且在横梁的两端功率流的幅值较小,多余约束横梁能够使传递能量均匀分布,抑制了能量向侧板的传播,有利于提高侧板寿命。通过对模型机的模态功率流测试对理论分析的结果进行了验证。模态实验时的测点布置参考了有限元模态分析的结果,选择模态变形较大的区域布置测点。由实验结果可知,多余约束横梁的两端能量分布较小,主要振动集中在附板之间,表明附板结构的设计可以有效吸收传递能量。横梁的输入功率流结果表明多余约束横梁的输入功率流向低频段移动,在高频时衰减较快,有利于振动筛的提速实现高速化。实验总体效果与理论分析结论一致。阐明了多余约束结构对弹性振动的抑制机理,对多余约束横梁附板的数量、位置、厚度以及双层附板之间的距离等参数进行了优化设计。优化结果表明:采用单层附板时,附板置于梁中部对弹性振动的抑制效果比较好,且随着附板厚度的增加减振效果增强,附板厚度为管梁壁厚的两倍以上时,增强的效果变的不再明显。采用双层附板时,通过调整两块附板之间的间隔可以获得两倍厚度的单块附板更好的效果,因此在不增加总体质量的前提下采用双层附板较好。对优化后的横梁进行了稳态响应分析,结果表明优化后的多余约束横梁结构对弹性振动具有更显著的抑制作用。该论文有图69幅,表23个,参考文献174篇。更多还原

【Abstract】 Strength and stiffness problems of vibrating screen are the key factors of restricting its development towards high-speed and large-scale. Based on the point of view that restricting the elastic vibration of vibrating screen,a method of adding redundant constraints to the vibration screen beam was put forward in this paper to decrease the stress concentration and uniform the energy distribution,thus improving the strength and stiffness without changing the mass of vibration screen was ensured. This is a new idea of designing high-speed and large-scale vibration screen.Firstly,the properties of the redundant constraints beam were analyzed,and the structure of redundant constraints beam was designed based on the basic principles of mechanics of materials,of which the mass and rotational inertia were designed corresponding to the ordinary tube beam.Then the design calculation of dynamic model of the vibrating screen was done.Dynamics property of the vibrating screen with redundant constraints beam and vibrating screen with general tube beam are analyzed.Two kinds of model of the first 10 natural frequencies, mode shapes and stress response under work frequency were obtained. The results show that dynamic stress and deformation of vibrating screen with redundant constraint beam decreased significantly, and the overall stiffness and strength are improved obviously.The suppressive effect of the redundant constraints beam, which is to reduce the amplitude,was studied on from the angle of energy transfer based on the results of finite element analysis.The modal power flow analysis results from Ritz series method shows the distribution of power flow within the beam.In comparison with ordinary tube beam,the modal power flow of the redundant constraints beam is evenly distributed in each mode,fluctuates throughout the beam and has a low amplitude at the ends of the beam.As a result,the redundant constraints beam can transfer the energy of vibration to the beam ends,helping improving the service life of the side plate.A experimental study of the modal and power flow test on the beam was carried out.The natural frequencies and modal shapes obtained from the modal test corresponds to that from the finite element analysis,indicating that the method of finite element analysis are reliable and the results of test are true.The modal test shows that the energy is concentrated on the central part of the redundant constraints beam between the two attached plates but attenuates at the ends of the beam,indicating that the attached plate can restrain vibration.The power flow test indicates that the power flow of redundant constraints beam attenuates rapidly at high frequencies and moves to low frequencies,it is helpful in speeding up the vibrating screen rapidly.Finally,to make full advantage of redundant constraints beam, the number, location,thickness of attached plates and the distance between double-deck attached plates are optimized respectively.The results show that the single-deck attached plate placed in the middle of the beam suppresses the vibration effectively,the suppressive effect on the vibration increases obviously with the increasing thickness until the twice as thickness as the tube beam.The double-deck attached plates will gain a better result than the single-deck ones with double thickness by adjusting the space between the two attached plates and therefore the double-deck attached plate is a better choice.Comparing the optimized redundant constraints beam with the optimized tube beam,the steady-state response were analyzed.The paper has 69 figures, 23 tables and 174 references.更多还原