中班育儿知识大全-大连市国税局网

附 录A
1. 关于软件接口连接
UG为三位建模软件， 有较为完善的分析功能，在独立建模是可进行质量，
面积，体积，强度等多方面计算，可自行编程进行导 入式分析。UG软件近几年
在国内开始运用，仍存在许多不足，在本次毕业设计中所体现的主要问题在于 软
件的不完全兼容，UG建模软件与ANSYS分析软件存在结构稍复杂模型不可执行
布尔操作 及分析，主要原因通过解读导入程序得知，在ANSYS分析软件中对UG
实体建模程序转换不完全，所 导致建模文件丢失性较大。存在软件版本配合问题，
同为高版本软件时导入文件出现丢失情况较小。如U G7.5与ANSYS12.0之间导入
文件时仅丢失少部分文件，同平面建模相对导入性较好。适于结 构简单模型进行
运用。
2. 模态实验应考虑的问题
实验模态分析就是以 控制理论为基础，从所测得的输入、输出信息中去
辨识结构的模态参数。近几年来，实验模态技术发展很 快，各种测试手段日
益更新，模态参数识别软件也层出不穷，这为我们获得结构的较为准确的模
态参数带来极大方便。
（1）激振方法
激振方法的选择包括两方面内 容：采用什么样的激振信号；采用单点激
振还是多点激振。问题的中心在于是否能够提供足够的能量，把 需要的频段
中的模态全部激发出来。激励信号可采用随机信号、脉冲信号等。随机信号
可用白噪 声发生器产生，试验中选用了0-160Hz白噪声信号，其优点是，能
量均匀分布在频带上，且在较宽 频率范围内对结构进行激励，总的激振力水
平，便如平均值、均方值等是可以控制的；其缺点是泄漏误差 大。用锤击法
提供脉冲信号，该方法的优点是设备简单，不需要精心设计安装激振器的夹
具，便 于现场测试或在线测试；激振点可以灵活，敲击力方向可以任意；测
试精度能满足一定要求，高于随机激 励。缺点是激振力频率范围不易控制；
仅适合于低频，高频模态不易激出来；由于振动能量分散，从而信 噪比小；
锤击有时可能过载，使结构进入非线性范围。固定的激振点是经过多点试敲
后选定的。 模态分析的频域法有两种：单点激振法和多点激振法。多点激振
法需要昂贵的多点激振设备，试验过程复 杂，但计算比较简单；单点激振法

所需设备简单，试验也较容易， 但计算方法要复杂上些。在本次实验中根据
现有条件，采用单点激振法。
（2）固定方式
在进行部件模态实验分析时，首先要确定被测物体的固定方式。固定方式一般有两种：一种是按照其实际工作状的方式约束，这种固定方式主要是
用于较波折部件或在振动 台上进行试验；二是悬吊式。由于本次实验对象是
车架，不可能选择实际工作状态方式，故采用橡皮绳悬 吊式，使其处于自由
状态下进行分析。结构处于自由状态具有最多的自由度，这样得到的模态参
数便于与其他部件一起进行整体结构的综合模态分析。具体悬吊方江是：车
架左右纵梁前后端各用一根橡 皮绳将整个车架吊挂在大型吊架上，即为四点
悬吊式。经实测，车架挂上后，系统的固有频率（所谓的“ 刚体模态频率”）
中的最高者为0.816Hz，小于第一阶弹性模态频率（FI=20.67Hz）的 15，
可近似认为被吊的车架处于自由状态，这样可以防止悬挂的刚体模戊与车架
的弹性模态发 生耦合。
（3）激励方式
采用电磁式激振器，最大激振力为200N 。激振器的推杆顶端连接一个力
传感器，力传感器固定在车架后横梁右下部。为了保证测试精度，不能让 被
测物体有附加约束而产生其它外力，例如，对结构激振时，除了产生垂直振
动外，还将产生回 转（转角），这时如果因为有激振器连接限制其转动，就
会产生附加的弯矩。为了解决这一问题，激振器 和被测物体之间的推杆需要
有一定的侧向弹性，这样既能保证在激振方向有一定的刚度，不影响激振力< br>的传递，双能减少在侧向对回转的约束。另外，推力杆的自振频率应远离被
测物体的模态频率。在 试验中要求顶杆与车架之间不能脱离，顶杆与力传感
器间不能有任何松动和间隙。此次试验采用顶杆与力 传感器间通过螺纹连
接。为防止顶杆与车架脱离，将力传感器固定在一个小底座上，该底座用螺
纹与一磁铁相联，同时将磁铁块吸附在车架上。还应注意激振点不应与测试
频段内任何一阶振型的节点相 重合。因此在进行正式试验以前应先进行预
测。 ?
（4）试验频段的选择
试验频段的选择应考虑到汽车在运行条件下可能的激振频率范围，通常
认为，远离振源频带 的模态对结构的实际振动影响（贡献量）较小。通俗的
说法就是“低频激励激不出高频模态”。事实上， 高频模态贡献的大小，除
与激振频率有关外，还与激振力的分布状况有关。此外，如果部件进行综合

分析，以求整体结构的模态，为使整体模态具有更高的精确度，部件模 态试
验的频段也应适当放宽，以求得稍多的模态。总值年模态过少，而各部件之
间的连接点较少 时，就不便于对整车进行综合分析。
考虑到汽车的运行速度与路面条件以及车架与其他部件 进行综合分析
的需要，选取0-120Hz作为其试验频段。
（5）测点布置
测点布置原则是：布置在悬架支点，纵、横梁连接点和刚度变化较显著
的点上；尽可能使车 架纵梁布点均匀，左右对称布置。这样，既便于今后的
模态综合，又不致使识别的模态失真。测点布置、 测点数量的选择还应考虑
到以下两方面的要求：能够明确显示在试验频段内所有模态的基本特征及互相间的区别；保证所关心的结构点（如与其它结构的连接点），都在所选的
测量点之中。为提高信噪 比，测点不应选在各阶振型节点附近；在研究的主
要部位，测点布置应较为密集。用压电式加速度传感器 测量各测点在垂直方
向上的振动加速度响应，并将信号记录在磁带机上（锤击法时），或现场采
集信号，实时处理得到频响函数，存储于微机硬盘（白噪声激励时）。
测振时加速度计安装 正确与否，对测量结果的正确性有很大的影响。安
装方式多种多样，我们根据测试频段及车架的构造，采 用永久磁铁吸附法的
安装方式以求简便、准确。
（6）为提高测试精度应采取的措施
1）仔细标定系统灵敏度。在机械阻抗测量时，我们校 正的不仅是单个
传感器的灵敏度，而是力传感器与加速度传感器灵敏度的相对比值。具体方
法见 参考文献。
2）冲击力的大小决定于激起各阶模态所需之能量水平，但过大的冲击
力会造成局部非线性，所以锤击时要控制冲击力的大小。同时锤击的动作要
迅速，不能抖动，特别要防止 试件反弹造成二次冲击。
3)为了减少谱泄漏，在处理时应采用数据窗。对冲击激励函数分 析，采
用指数衰减数据窗可以减少噪声总电平。
4)为检查模态参数可靠性，可采 取互易性来检验，即根据阻抗矩阵的对
称性，在P点激振、L点测振的响应与L点激振、P点测振的响应 相同。
5）进行数据处理时，首先需要确定触发系统。脉冲信号采用信号触发。
即 当有一脉冲信号过来时，才进行一次触发平均。为减少随机误差，应进行
多次平均。
6）考虑到架结构的阻尼较小，频响函数的半功率带较窄，故应尽量提

高频率分辨率。
7）传递函数可信性检验。所有时域信号均在微机上显示，正常时 才往
下进行。每个传递函数都用相干函数检验，相干函数绝大多数都在0.85以
上。
8）力谱要符合要求，幅值差不大于3dB。

附 录B
for software interfaces connection
UG for three modeling software, there are more complete analysis, in the
modeling is available to the area, volume, quality and strength for the various
programming for import by itself, but in the analysis. UG software in the past few
years at home and begin to use many. at the graduation design by the main problem
lies in the software is not entirely compatible, modeling and UG ANSYS analysis
software is a model not perform complicated structure and analysis, boolean The main
reason by interpreting the importer, the analysis software ANSYS UG entity modeling
applications for conversion, not by modeling papers missing. there is sexual older
version match, with the high edition software import file a missing information. as a
smaller UG7. 5 and ANSYS12.0 between the import file was missing document, with
a plane model in the import of the better. for simple model be applied.
Modal test should consider
Experimental modal analysis is to control theory, from the measured input and
output information to identify structural modal parameters. In recent years,
experimental modal technology has developed rapidly, growing a variety of test
methods updated modal parameter identification software is also another, which as we
get more accurate structure of the modal parameters of a great convenience.
excitation method
Exciting choice of methods, including two aspects: what kind of excitation signal;
excitation using a single point or multi point excitation. Question is whether the center
can provide enough energy, the band needed to stimulate all the modes. Excitation
signal can be random signals, pulse signals. Random white noise generator signal is
available, test the selected 0-160Hz white noise signal, its advantage is that energy is
uniformly distributed in the band, and a wide frequency range of the structure of
incentives, the total level of the exciting force, just like a mean, mean square values,
etc. can be controlled; its major drawback is that leakage error. Provide pulses with
the hammer method, this method has the advantage of simple equipment, do not
install the exciter fixture designed for easy field testing or online testing; excitation

point can be flexible, percussion force direction can be arbitrary; test accuracy can
meet certain requirements, higher than the random excitation. The disadvantage is
difficult to control the frequency range of exciting force; only suitable for low
frequency, high-frequency modes is not easy to shock them; vibrational energy spread
due to noise ratio is small; hammer can sometimes overload the structure into the
nonlinear range. The excitation point is fixed multi-point try after the selected after
the knock. Modal analysis of frequency-domain method in two ways: single-point
excitation method and multi-point excitation method. Multi-point excitation method
requires expensive multi- point excitation equipment, the testing process complex, but
the calculation is relatively simple; single-point excitation method required simple
equipment, the test is relatively easy, but on a more complicated calculation. In this
experiment, under the existing conditions, using single-point excitation method.
Fixation
During the experimental modal analysis of components, the first object to be
measured to determine a fixed way. Fixed the way to have two: one is shaped in
accordance with the actual work the way constraints, this fixation is mainly used for
more twists and turns parts or the vibration table and tested; second is suspended. As
the object of this experiment is the frame, means the state can not choose the actual
work, so use rubber rope suspended, it is in a free state for analysis. Structure in a free
state with the largest degree of freedom, so easy to obtain the modal parameters
together with other parts of the overall structure of a comprehensive modal analysis.
Jiang is the specific suspension side: left and right frame rails front and back of the
rubber with a hanging rope to the frame in a large hanger, that is, four suspended.
After measurement, the frame mount, the system's natural frequency (the so-called
body mode frequencyin the highest of 0.816Hz, less than the first order
elastic modal frequency (FI = 20.67Hz), 1 5 , can be approximated that the frame
was hanging in a free state, which would prevent suspension rigid with the frame of
the elastic modulus E mode coupling occurs.
Incentives
Using electromagnetic shaker, maximum exciting force of 200N. Exciter
putting the top connected to a force sensor, force sensors fixed on the bottom right of
the frame after the beams. In order to ensure test accuracy, so that the measured object
can not have additional constraints arising from other external forces, for example,

excitation of the structure, in addition to generate vertical vibration, it will also
produce rotation (angle), then if the connection limit because of the exciter its rotation,
will produce additional moments. To solve this problem, between the exciter and the
measured object putter need to have some lateral flexibility, so that can guarantee a
certain direction in the excitation of stiffness does not affect the transmission of the
exciting force, can reduce the double In the lateral constraints on the rotation. In
addition, the thrust rod natural frequency away from the modal frequency of the
measured object. Required in the test between the ejector and the frame can not be
separated from the mandrel and the force between the sensor does not have any loose
and gaps. The test used by the ejector and the threaded connection between the force
sensor. To prevent the mandrel and the frame out, the force sensor fixed on a small
base, the base with a thread associated with a magnet while the magnet adsorption on
the frame. Excitation point should also note that the band should not be testing any
vibration mode of the nodes coincide. Therefore, during the trial to be preceded by the
official forecast. ?
the choice of test frequency
Test frequency selection should take into account vehicle operating conditions
possible in the excitation frequency range, generally considered, away from the local
oscillator frequency of modal vibration of the structure of the actual impact
(contribution amount) is small. Popular saying that
laser excitation modes.
in addition with the excitation frequency, but also with the distribution of the exciting
force. In addition, if parts of a comprehensive analysis, the overall structure of the
mode in order for the overall mode has a higher accuracy, the test frequency modal
components should also be relaxed, in order to achieve slightly more modal. Modal
value was too small, and the connection point between the various components when
there are fewer, not to facilitate a comprehensive analysis of the vehicle.
Taking into account the car's speed and road conditions, and other parts of the frame
with a comprehensive analysis of needs, select 0-120Hz band as its pilot.
measuring points
Measuring points principle is: arranged in the suspension pivot, vertical, beam
stiffness of the connection point and the more significant point; distribution frame
rails as far as possible uniform, symmetrical layout. In this way, both for the future of

the modal synthesis, modal identification without causing distortion. Measuring
points, measuring points of the selection should also take into account the following
two requirements: the ability to clearly show the band in the test mode all the basic
characteristics and differences between each other; to ensure the structural point of
interest (such as with the other structures connection point), are among the selected
measurement points. To improve the signal to noise ratio, the measuring point should
be selected in the vicinity of the first vibration mode node; the main part in the study,
measuring points should be more intensive. Piezoelectric acceleration sensor with the
measuring points in the vertical vibration acceleration response, and the signal
recorded on the tape drive (when the hammer method), or on- site signal acquisition,
real-time processing to get frequency response function, stored on computer hard disk
(white noise excitation).
Vibration when the accelerometer is installed correctly or not, the accuracy of the
measurement results have great impact. Install a variety of ways, we test the
frequency and the frame according to the structure, the use of permanent magnets in
order to assay the installation simple and accurate.
To improve test accuracy measures to be taken
1) careful calibration of the system sensitivity. In the mechanical impedance
measurements, we corrected the sensitivity of the sensor is not only the individual, but
force sensor and acceleration sensor relative sensitivity ratio. Specific methods see
reference.
2) The impact depends on the size of the order provoked modal energy level
required, but the impact is too large will result in local non-linear, so when the
hammer impact force to control the size. At the same time hammering action to
quickly, can not shake, particularly to prevent the rebound in the specimen cause
secondary impact.
3) To reduce the spectral leakage, the data should be used in the processing
window. Function analysis of the impact of incentives, the use of exponential decay
data windows can reduce the overall noise level.
4) To check the reliability of modal parameters, reciprocity can be taken to test
that, according to the symmetry of the impedance matrix, excitation at point P, L-point
vibration excitation of the response to L-point, P-point vibration response the same.
5) data processing, you first need to determine the trigger system. The signal pulse

is triggered. That is, when there is a pulse signal over time, triggering an average of
only once. To reduce random error, should be several times the average.
6) Considering the small frame structure, damping, frequency response function of
the half-power band is narrow, it should try to improve the frequency resolution.
7) the credibility of the transfer function test. All time-domain signals are
displayed on the computer, only down to normal. Each transfer function is tested with
the coherence function, coherence function, most of them are above 0.85.
8) power spectrum to meet the requirements, the amplitude difference is less than
3dB.