大于或等于2，所以刚性区域至少两个。
7、Solution->ADAMS Connection->Export to ADAMS命令，选择的第4步中建立的界面节点interface nodes，单位选SI即可，输入提取的模态阶数（如输入20，如果界面节点数为2，则生成的mnf文件包含的模态阶数为32，这是因为界面节点是有六个自由度的节点，每个自由度都对应一个约束模态，所以模态中性文件中记录的模态阶数=ANSYS中指定的模态阶数+界面节点数×6），在Element Results一栏选Include Stress and Strain，表明在ADAMS仿真分析之后，在ADAMS/Postprocessor分析时可以显示动态应力和应变。
关于约束：在有限元模型中不用施加约束，只有在及其特殊的情况下才需要约束，比如构件上的某个节点如果在ADAMS的模型中是与大地固结在一起的，那么在该节点处施加约束才是有用的。
三、ANSYS输出模态中性文件需要注意
四、Ansys 如何生成adams的模态中性文件 11.3. Exporting to ADAMS
After building the model in ANSYS (including all interface points), the next step is to invoke the ANSYS-ADAMS Interface to create the modal neutral file, Jobname.MNF. Creation of this file is driven by an ANSYS command macro called ADAMS.MAC.
To start the interface, select the following GUI path. Main Menu> Solution> ADAMS Connection> Export to ADAMS
The Select Interface Points dialog box appears first. From this dialog box, you must select two or more interface points.
Note
Do not choose too many interface points since one point gives rise to 6 degrees of freedom in ADAMS. Too many interface points may lead to huge files and models.
After you confirm your selection by picking OK, the Export to ADAMS dialog box appears.
Figure 11.2 Export to ADAMS Dialog Box
图形在打开的对话框中，
Complete the following steps using this dialog box.
1. System of Model Units: The units used for the model is important to the ADAMS program, whereas ANSYS only requires that you use a
consistent set of units. The units chosen will be written to the .MNF file and can be recalled with the ADAMS/Flex module. If no units are specified, ADAMS assumes that the same units were used in ANSYS as the ones chosen in the ADAMS model. See the /UNITS command for details. If you specify user defined units, a Define User Units dialog box will appear for you to input the conversion factors (for length, mass, force, and time) between SI units and your chosen units. Below is an example of user defined units in which the component has been modeled using millimeter, tonne (metric ton), newton, and second. Length Factor = Mass Factor = Force Factor = Time Factor =
1 meter/millimeter 1 kilogram/tonne 1 newton/newton 1 second/second
= 1000 = 0.001 = 1 = 1
2. Number of Modes to Extract: Input the number of normal modes to compute. Normal modes are the eigenmodes of the component with all degrees of freedom of all interface points fixed. The number of normal modes depends on the frequency range of the excitation you will apply in your ADAMS model. You must choose a sufficient number of modes to represent your structure in that frequency range. In ADAMS, if you have chosen too many normal modes, you are able to deactivate eigenmodes based on the frequency or an energy criterion.
3. Element Results: Specify whether or not the program should write stress and/or strain results. This option has no effect on the output for beam elements. If you want to output stress and strain for only a subset of nodes, you should create a node component named \ADAMS command macro.
4. Shell Element Result Output Control: Specify the shell element output location (top, middle, bottom). This option has no effect on the output for solid elements and beam elements. 5. Filename: Specify a filename for the modal neutral file. The default name is Jobname.MNF. If a file with the chosen name exists, it will be moved to a file named filename.MNFBAK.
6. Export to ADAMS: Choose “Solve and create export file to ADAMS” to initiate the solution sequence. Static and normal modes are computed and all information required by ADAMS is written to the .MNF file specified above. Only the selected elements are considered. The current model is written to the database file Jobname.DBMNF.