Effects of Bending Moments and Pre-Tightening Forces on the Flexural Stiffness of Contact Interfaces in Rod-Fastened Rotors
Effects of Bending Moments and Pre-Tightening Forces on the Flexural Stiffness of Contact Interfaces in Rod-Fastened Rotors
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DOI：
10.1115/gt2012-68221
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
Jin Gao;Qi Yuan;Pu Li;Hongtao Zhang;Z. Lv
中科院分区：
文献类型：
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作者：
Jin Gao;Qi Yuan;Pu Li;Hongtao Zhang;Z. Lv
杆紧固转子由一系列盘组成，这些盘通过中心拉杆或节圆直径上的几个拉杆夹紧在一起。杆固转子接触界面的等效弯曲刚度是精确分析转子动力学性能的关键。在这项研究中，每个接触界面被建模为刚度为Kc的弯曲弹簧和铰链。取决于预紧力和弯矩（静态）的接触界面的接触状态对Kc有影响。提出了两种接触状态下Kc的计算方法。第一种接触状态是接触界面的整个区域都处于接触状态，Kc由接触表面的凹凸组成的接触层决定。采用Hertz接触理论和GW（Greenwood和威廉姆森）统计模型计算接触层的等效抗弯刚度Kcc。第二种接触状态是接触界面的某些区域分离（当弯矩较大时），转子段的等效弯曲刚度Ksf（不包括Kcc）减小，因为分离区域的材料对转子的弯曲承载能力没有贡献。通过有限元法（FEM）计算的应变能用于确定Ksf。刚度Ksf等于转子段的盘的串联刚度，其弯曲刚度为Kd，并且弹簧在接触界面的位置处的弯曲刚度为Kcf，因此Kc等于第二接触状态下的Kcc和Kcf的串联刚度。一个简化的杆紧固转子的结果表明，对于一个固定的预紧力，Kcc减小与弯矩在第一接触状态，而增加与弯矩在第二接触状态。此外，当转子受到相对大的预紧力时，Kcf和Kc在第二接触状态下随着弯矩的增加而突然减小。最后，采用多点激振法测量了实验固杆转子的模态参数。结果表明，随着预紧力的减小，试验模态频率降低。Copyright © 2012 by ASME
The rod-fastened rotor is comprised of a series of discs clamped together by a central tie rod or several tie rods on the pitch circle diameter. The equivalent flexural stiffness of contact interfaces in the rod-fastened rotor is the key concern for accurate rotor dynamic performance analysis. Each contact interface was modeled as a bending spring with stiffness of Kc and a hinge in this study. The contact states of the contact interfaces which depend on the pre-tightening forces and bending moments (static) have effects on Kc. The approach to calculating Kc in two contact states is presented. The first contact state is that the whole zone of the contact interface is in contact, Kc is determined by the contact layer which consists of asperities of the contact surfaces. Hertz contact theory and the GW (Greenwood and Williamson) statistical model are used to calculate the equivalent flexural stiffness of the contact layer Kcc. The second contact state is that some zones of the contact interface are separated (when the bending moment is relative large), the equivalent flexural stiffness of the rotor segment Ksf (not include Kcc) decreases as the material in the separated zone has no contribution to the bending load carrying capacity of the rotor. The strain energy which is calculated by the finite element method (FEM) is used to determine Ksf. The stiffness Ksf is equivalent to the series stiffness of the discs of the rotor segment with flexural stiffness of Kd and a spring with bending stiffness of Kcf in the location of the contact interface, so Kc is equal to the series stiffness of Kcc and Kcf in the second contact state. The results of a simplified rod-fastened rotor indicate that for a fixed pre-tightening force, Kcc decreases with bending moments in the first contact state whereas increases with bending moments in the second contact state. In addition, Kcf and Kc decreases abruptly with the increase of bending moments in the second contact state when the rotor is subjected to a relatively large pre-tightening force. Finally, the multipoint exciting method was used to measure the modal parameters of the experimental rod-fastened rotor. It is found that the experimental modal frequencies decrease as the pre-tightening force decreases.Copyright © 2012 by ASME