12.在激振器安装/工作中,最为常见的实际错误是什么?

模态激振器相关问题

Misalignment of the stinger is often a significant problem in modal testing. Given a large enough misalignment, the shaker armature coil windings will be damaged due to scraping. More commonly, misalignment results in distortion and poor quality measured frequency response functions, which are uncharacteristic representations of the true system. At times this will cause difficulties in estimating modal parameters from data that has been contaminated with poor shaker alignment. This type of measurement contamination is often overlooked because of other issues related to many inconsistencies in the test structure system due to noise, nonlinearities and other effects. It is all too easy to overlook this simple measurement issue due to other commonplace factors.

模态试验中,推力杆不对中常常是一个很大的问题。在很大的不对中情况下,因为摩擦,激振器动圈绕组将损坏。更为常见的是,不对中导致测得的频响函数失真且质量差,它们不是真正系统的特性表示。有时,这很导致从不良激振器对中所污染的数据中估计模态参数困难。因为试验结构系统中关于不一致的很多其他事情,这种激振器污染常被忽略掉了。不一致性是由于噪声、非线性和其他影响所引起的。

The main problem with shaker misalignment is that the force transducer or impedance head transmits transverse loads that do not align with the sensing axis of the transducer normal to the surface. This causes a distortion of the actual measured force that is applied to the structure. It is very important to make the best possible measurement and alignment is an important part of this process.

激振器不对中的主要问题是,力传感器或者阻抗头传递了横向载荷,它与法向于结构的传感器的灵敏轴向不对中。对于测得最优可能的测量结果,它非常重要,并且对中是这个过程中的重要部分。

Another problem will result when the structure is too compliant at the point of shaker attachment. As a result, the shaker may not have enough stroke for the actual structure displacement observed during testing. While displacement is one effect, consider the shaker coils velocity limitations (5.2 ft/s, around 62 ips for the 2100E11) as well. In these cases the structure wants to deflect (especially at resonant frequencies) and the shaker cannot keep up with the actual displacement/velocity of the structure. This causes a force dropout in the input force spectrum, especially at resonant frequencies. Many times this will be referred to as impedance mismatch between the shaker and structure. In order to remedy this, typically the shaker will need to be moved to another suitable input location where the structure is not as compliant, yet still adequately excites all the modes of interest.

当结构在激振器连接点太柔顺时,会产生另外的问题。因此,在试验过程中,对于观察实际的结构位移,激振器可能没有足够的行程。尽管位移是一种影响,同时也要考虑激振器线圈的速度限制(对2100E1,5.2ft/s,大约62ips)。在这种情况下,结构想要变形(特别是在共振频率附近),而激振器不能“跟得上”结构的实际位移/速度。这种情况会引起输入力谱上的“力陷落”,特别是在共振频率附近。很多时候,把这个称为激振器和结构之间的阻抗不匹配。为了解决这个问题,激振器通常需要移动到另外合适的输入位置上,在那里结构不那么柔顺,但仍然能够充分地激起所有感兴趣的模态。