Nastran生成adams柔性体mnf文件的方法

利用Hypermesh和nastran创建mnf流程1.建立几何模型，定义材料属性、单元属性。

2.创建约束和特征值卡，如下：约束为无量纲。

定义为mis1,选择下列四点确定一个节点集定义。

定义单元集。

特征值为EIGRL特征。

3.对控制卡进行设置（1）sol（2）PARAMParam fixedb -1Param autospc yesParam post，0(3) case_unsupported_cards一般有以下部分：ADAMSMNF FLEXBODY=YES,OUTGSTRN=YES,OUTGSTRS=yes，EXPORT= BOTHRESVEC=yes，STRFIELD = ALLGPSTRESS=all **要求节点应力输出GPStrain（plot）=all **要求节点应变输出Stress（PLOT）=all **要求单元应力输出STRAIN(FIBER,PLOT) **要求单元应变输出OUTPUT(POST) ** 分界符Set 101=all **为面或者体定义单元集SURFACE 102 SET 101（**上面定义的单元集）FIBER=Z1，NORMAL zSet 103=allVolume 104 set 103 , direct **定义实体单元集的体积(4)bulk _unsupported _cardsDTI,UNITS,1,KG,N,M,S(5) global_case_controlSuper=1 Method=1Stress （plot ）=allStrain （fiber ，plot ）=all Gpstress=all Gpstrain=allCreate an MD DB using MD NastranMD DB can be created in the same was as creating MNF. A new option, EXPORT, is added to ADAMSMNF card to specify the output option.ADAMSMNF FLEXBODY=YES EXPORT=MNF/DB/BOTH MNF: generate modal neutral file DB: generate MD DBBOTH: generate both MNF and DBPlease refer to MD Nastran Quick Reference Guide and Reference Manual for details. Use Flex Toolkit to convert MNF to MD DBUse can also use the mnf2mtx utility to convert MNF to MD DB. The usage is: adams flextk mnf2mtx source.mnf -O dest.MASTERwhere source.mnf is the mnf you want to convert and dest.MASTER is the Database name. If dest.MASTER exists, mnf2mtx will append the flexible body in source.mnf to dest.MASTER. So user can combine MNFs into one MD DB using mnf2mtx. For example, adams flextk mnf2mtx source1.mnf -O dest.MASTER thenadams flextk mnf2mtx source2.mnf -O dest.MASTER点选EIGRL 卡Output 栏中相关主题PopupPopup另请参阅PopupTranslating FE Model Data > Translating MSC.Nastran DataTranslating MSC.Nastran DataThere are two different interfaces that you use to translate MSC.Nastran data for use in Adams/Flex. Learn about:• Using MSC.Nastran 2004 and Above• Using MSC.Nastran 69.x, 70.x, or 2001• Verifying the Model• Computing MSC.Nastran Stress/Strain Modes• MSC.Nastran XDB Support for Stress/Strain Modes• Shortened Stress/Strain ModesUsing MSC.Nastran 2004 and AboveStarting in version 2004, MSC.Nastran provides an improved interface for generating a modal neutral file (MNF). The new MSC.Nastran Adams Interface allows you to generate an MNF directly from MSC.Nastran without generating an OUTPUT2 file. The MSC.Nastran Adams Interface does not require a DMAP alter or a translator to convert MSC.Nastran output files to MNFs.The MSC.Nastran Adams Interface is a licensed feature of MSC.Nastran. For more information, contact your local sales representative. If you already have the MSC.Nastran Adams Interface license,refer to the MSC.Nastran Quick Reference Guide and Reference Manual for information on how to use it.Using MSC.Nastran 69.x, 70.x, or 2001Learn more about translating MSC.Nastran data using later versions of MSC.Nastran:• About the MSC.Nastran DMAP and OUTPUT2 to MNF Translator • Defining Your FE Model • Running MSC.Nastran • Running the Translator• Technical Notes on the MSC.Nastran DMAPNote: V ersions 69.x, 70.x, and 2001 of MSC.Nastran must be licensed to use the DMAP alters andrun solution 103. MSC.VisualNastran for Windows does not meet these requirements.About the MSC.Nastran DMAP and OUTPUT2 to MNF TranslatorTo generate a modal neutral file (MNF ) in versions 69.x, 70.x, or 2001 of MSC.Nastran, you need: • mnfx.alt - A solution sequence-independent DMAP alter. It directs MSC.Nastran to compute the data required for the MNF and write it to an OUTPUT2 file. Adams/Flex includes mnfx.alt DMAP in theAdams distribution.• msc2mnf.exe - MSC.Nastran OUTPUT2 file to MNF translator. It is an executable translator thatreads the MSC.Nastran OUTPUT2 file and writes MNFs.The mnfx.alt DMAP alter extracts flexible body information from MSC.Nastran. It uses thesuperelement techniques of component modal synthesis in MSC.Nastran to generate the flexible body information and output the data to a binary file, in full machine precision.The OUTPUT2 to MNF translator is based on the Adams MNF Toolkit, which you can configure to optimize the MNF .Defining Your FE ModelThe following outline the steps required to set up your MSC.Nastran input file to generate the necessary data for a modal neutral file (MNF ). To set up your MSC.Nastran input file:1. Create a finite element model of the flexible body. The finite element model is defined in the Bulk Data Section. For more information, see the MSC.Nastran Quick Reference Guide .2.Set up an MSC.Nastran analysis of the model using one of the following solution sequences: SOL 103, 111, 112. 3. Include a DTI, UNITS entry in the BULK DATA Section. Learn about setting units .4.Include the mnfx.alt DMAP alter distributed with Adams/Flex. You can obtain the file mnfx.alt from: install_dir /flex/examples/MSCNASTRAN/v69/mnfx.altinstall_dir /flex/examples/MSCNASTRAN/v70/mnfx.alt install_dir /flex/examples/MSCNASTRAN/v70.7/mnfx.alt install_dir /flex/examples/MSCNASTRAN/v2001/mnfx.alt5.In the File Management section of the MSC.Nastran input file, assign a file to be used as the output file and assign the file to unit 20. For example, enter the following to assign the output file test4.out to unit 20: assign output2='test4.out' status=unknown unit=20 form=unformattedNote: Unit must be 20. The DMAP alter is hard-coded to use unit 20.6.To avoid data recovery on the residual structure, include the following in the BULK DATA section: param,fixedb,-1Note: L oads, boundary conditions, and output requests are not necessary to the extent they are in aconventional analysis.Running MSC.NastranYou execute MSC.Nastran using the command nastran (your system administrator can assign a different name to the command). You specify keywords with the nastran command to request options for how to execute the MSC.Nastran job.Formatnastran input.dat keyword_1 = value_1 keyword_2 = value_2 ... where input.dat is the MSC.Nastran input file. Some common keywords are listed below. For information on keywords and their defaults, see the MSC.Nastran Installation and Operations Guide . Keyword DescriptionRunning the TranslatorOnce you've generated an output file, you can run the translator, msc2mnf.exe, to generate the modal neutral file (MNF ). You can run the translator:• Through the Adams/Flex Toolkit, which you access through Adams toolbar on UNIX and the StartMenu on Windows.For instructions about running the translator through the Adams/Flex toolkit, see Running theMSC.Nastran Translator .Before running the translator, be sure to set up the translation as explained in Setting Up TranslationOptions through the MNF Toolkit .To run the translator from the command window: Enter the following where file .out is the MSC.Nastran output file: msc2mnf.exe file.out For example, enter:msc2mnf.exe test4.outAlso, verify that the free body normal modes have a reasonable natural frequency. You should expect to see six rigid body modes, unless you fixed the DOFs with displacement boundary conditions.Technical Notes on MSC.Nastran DMAPThe next sections describe the DMAP alter in more detail and explain some optional parameters and settings that you might want to set before running a translation:• More on DMAP Alter• Optional Parameters You Can Set • Setting UnitsMore on DMAP AlterThe MSC.Nastran DMAP alter is organized on a superelement-by-superelement basis so you can output multiple MNF files from a single MSC.Nastran job. The input requirement is that each Adams flexible component be its own superelement.By default, the alter automatically orthogonalizes component modes within MSC/Nastran before outputting the data to the intermediate output file. A case control subcase and corresponding eigenvalue extraction entry (for example, EIGRL) are not necessary for the orthogonalization. Adams skips the subsequent orthogonalization phase if it detects diagonal mass and stiffness matrix input. You can generate additional diagnostic output and send it to the *.f06 file by setting the parameter check to 1 (param, check,1 in BULK DATA). For more information on diagnostics, see OptionalParameters You Can Set .The information that the alter provides is:• Units information, provided in a DTI entry. (For more information, see Setting Units .)• Grid and element connectivity output to neutral file, eliminating the need for any *.f06 output to beread.• Multiple coordinate systems because all quantities are transformed to the basic coordinate system priorto output.• Flexible body data including the following, which is written to the intermediate output file: • Grid data (BGPDT)• Element connection data (ECT) • Physical mass distribution (MGG)• Orthogonalized Craig-Bampton component modes• Generalized stiffness and generalized mass corresponding to the Craig-Bampton modesNote that WTMASS has been removed from all output mass quantities (physical and generalized). Units data input to Adams is expected to resolve all potential discrepancies.Optional Parameters You Can SetYou can set the following parameters in BULK DATA before translating the model using the param,name,value format:Setting UnitsBecause Adams/View and Adams/Solver require units, you must specify units in MSC.Nastran data using a DTI BULK DATA entry that includes the unique identifier UNITS. When you specify the units, the units apply to all superelements in your model.The format of the DTI BULK DATA entry is shown next. The table below lists the appropriate unit labels.DTI UNITS 1 MASS FORCE LENGTH TIMEFor example, you can enter the following for units:DTI UNITS 1 KG N M SUnit LabelsNote: A lthough you need the MSC.Nastran's WTMASS parameter to ensure consistent units inMSC.Nastran, MSC.Nastran ignores WTMASS when generating output for Adams/Flex. Instead, you supply units data for Adams/Flex using the DTI, UNITS entry, as explained earlier.For example, if you model mass in grams, force in Newtons, length in meters, and time in seconds, you set the WTMASS parameter to 0.001, ensuring that MSC.Nastran works with the consistent set of kg, N, and m. You then set the units for Adams/Flex by entering: DTI, UNITS, 1, GRAM, N, M, SOn the other hand, if you model length in inches and force in pounds, you can enter the mass in slug units with WTMASS set to 0.083 (=1/12), or in units of pounds mass with WTMASS set to 2.588e-3 (=1/32.2/12=1/386.4). The DTI, UNITS choices for Adams/Flex are, therefore, either of the following:DTI, UNITS, 1, SLUG, LBF, IN, S DTI, UNITS, 1, LBM, LBF, IN, SApplying the WTMASS parameter directly to the mass (for example, specifying density in terms of [12slug/in**3]) is not acceptable for Adams/Flex because [12slug] is not a mass unit known to Adams.Verifying the ModelThe MSC.Nastran translator writes a summary of the modal neutral file (MNF ) export to the terminal window. If you are using MSC.Nastran 2004 or above, the Adams interface writes a summary of the MNF export to the MSC.Nastran output file. Please review this data for any concerns. In particular, ensure that the:• Mass, center of mass location, and moments of inertia are as expected.• During the MNF write, the constraint modes and the constrained normal modes are orthogonalized.This yields modes that are:• An approximation of the free-body normal modes.• Interface modes, where the interface is the collection of all the attachment point DOFs.Also, verify that the free body normal modes have a reasonable natural frequency. You should expect to see six rigid-body modes, unless displacement boundary conditions are present.Computing MSC.Nastran Stress/Strain ModesFor Adams/Durability to process stresses or strains on flexible bodies, modal stress or strain shapes need to be present in the modal neutral file (MNF ) of the flexible body. You do this by havingMSC.Nastran recover a stress or strain mode for every mode shape computed for Component Mode Synthesis (CMS).• MSC.Nastran Grid Point Stresses• Example• Known Limitations, Problems, and RestrictionsMSC.Nastran Grid Point StressesBecause modal information contained in the MNF can only be associated with nodes, the MSC.Nastran grid-point stress data recovery option is required. The following Case Control commands are required in the MSC.Nastran input file to compute stress or strain modes for the MNF:• GPSTRESS: Requests grid point stresses output.• GPSTRAIN: Requests grid point strains output.• STRESS(PLOT): Requests element stress output.• STRAIN(FIBER,PLOT): Requests element strain output.• OUTPUT(POST): Delimiter.• SET: Defines a set of elements for a surface or volume.• SURFACE: Defines a surface of plate elements referenced by the SET command.• VOLUME: Defines a volume of solid elements referenced by the SET command.For more information on these commands, see the Case Control section of the MSC.visualNastran Quick Reference Guide. For more information on computing grid point stresses, see the MSC.Nastran Linear Static Analysis User's Guide.Note: Y ou can only transfer one surface stress or strain fiber of plate elements to the MNF for processing in Adams. If more than one fiber is specified on the SURFACE card, the msc2mnf translator issues a warning message and only transfers the first surface stress fiber it finds inthe OUTPUT2 file.Including stress or strain modes in the MNF can significantly increase the file size. Therefore, it becomes even more important to optimize the MNF if possible. For information onoptimizing the MNF, see Optimizing an MNF or an MD DB. Including both stress and strainmodes will further increase the size of the MNF and is generally not recommended for largemodels, unless both quantities are needed.When defining subcases in Case Control, you must have the GPSTRESS, GPSTRAIN,STRESS, and STRAIN cards before the first SUBCASE card. In addition, the OUTPUT,SURFACE, and VOLUME cards should follow all subcase definitions and appear at the end of the Case Control.ExampleExample above shows the changes that are required in the MSC.Nastran input file when the computation and transfer of both stress and strain modes are desired. Because the model contains solid and shell elements, a surface and a volume are defined for computing these grid-point stresses and strains. The surface fiber selected is Z1 and the grid-point stress/strain coordinate system is consistently defined to be the basic FE model system.Known Limitations, Problems, and Restrictions• Only one FIBER is output on SURFACE.• SURFACE or VOLUME should be defined in consistent coordinate (basic) system.MSC.Nastran XDB Support for Stress/Strain ModesYou can store the ortho-normal stress and/or strain modes in XDB file format that are compatible with the mode shapes in the modal neutral file (MNF) and subsequent modal responses from an Adams simulation. The benefits of this capability are:• Unlimited model size - MSC.Patran can access results from an XDB file of any size and with muchmore efficiency than from an OP2 file.• MSC.Fatigue analysis - Modal coordinates from Adams can be combined with stress or strain modes in XDB file for very efficient MSC.Fatigue analysis using modal superposition.• Element-based support - The XDB file format supports element-based and/or grid-point based stress or strain. Element-based results allow you to perform advanced fatigue analyses such as multi-axial fatigue and weldments.Learn more:• Creating an XDB File• Limitations• ExamplesCreating an XDB FileTo create an XDB file with stress or strain modes, add the following entry in the Bulk Data section: PARAM,POST,0This is in addition to the necessary commands that are added to Case Control (see Computing MSC.Nastran Stress/Strain Modes ). In the case of grid point stresses or strain, however, one additional command is required to output grid point stress or strain modes:STRFIELD = ALLNote that if you are only interested in working with element-based stress or strain, this command is not needed. For more information on these entries and commands see the, MSC.Nastran Quick Reference Guide.Limitations• Grid-point strain modes cannot be stored in the XDB nor can MSC.Patran post-process them. • Element-based stress or strain modes cannot be stored in the MNF nor can Adams/Durability postprocess them.ExamplesThe following are examples of MSC.Nastran input decks. See the Case Control section of theMSC.Nastran Quick Reference Guide for more information on the AdamsMNF command that is being used in these examples.Example of Requesting No Grid Point Stress/StrainIn the following example, no grid point stress or strain modes have been requested. Only element-based strain modes have been requested with STRAIN(PLOT) = ALL. These strains will be stored in the XDB (PARAM,POST,0) for postprocessing in MSC.Patran or for combining with Adams modal responses from Adams/Durability for an MSC.Fatigue analysis. This is the most efficient process for obtaining strains for the sole purpose of performing a fatigue analysis. If you are not interested in viewing strains in Adams, there is no need to compute grid-point strain modes nor storing them in the MNF . You will also seea savings in file size and processing time from this. The same is true for stress modes if they are desired over strains.SOL 103CENDAdamsMNF, FLEXBODY=YES, OUTGSTRS=NO, OUTGSTRN=NO...STRAIN(PLOT) = ALL...BEGIN BULK...PARAM,POST,0...ENDDATAExample of Requesting Grid-Point Stress on All Solid ElementsIn the following example, grid-point stress (GPSTRESS) modes have been requested on all solid elements (VOLUME). This data, as well as the element-based stress (STRESS) modes, will be stored in the XDB due to the STRFIELD=ALL command and the PARAM,POST,0 card. The grid point stress modes will also be stored in the MNF with the OUTGSTRS=YES option set on the AdamsMNF command. This allows Adams/Durability to postprocess stresses on the flexible body in Adams using the modal stress recovery technique.SOL 103CENDAdamsMNF, FLEXBODY=YES, OUTGSTRS=YES, OUTGSTRN=NOSTRFIELD = ALL...STRESS(PLOT) = ALLGPSTRESS = ALLOUTPUT(POST)SET 92 = ALLVOLUME 12 SET 92 DIRECTBEGIN BULK...PARAM,POST,0...ENDDATAExample of Requesting Grid-Point StressIn the following example, again, grid-point stress modes have been requested. They will not be stored in the XDB, however, because the STRFIELD=ALL command is missing. Therefore, onlyelement-based stress modes will be available in the XDB. Grid-point stress modes will be stored in the MNF because the AdamsMNF option, OUTGSTRS is still set to YES.SOL 103CENDAdamsMNF, FLEXBODY=YES, OUTGSTRS=YES, OUTGSTRN=NO...STRESS(PLOT) = ALLGPSTRESS = ALLOUTPUT(POST)SET 92 = ALLVOLUME 12 SET 92 DIRECTBEGIN BULK...PARAM,POST,0...ENDDATAShortened Stress/Strain ModesShortened stress/strain modes refers to the capability of defining a group or subset of elements in FEA for stress/strain recovery during modal neutral file (MNF) generation. FEA programs allow you to judicially define subregions of your component where stress/strain is of interest. If these subregions are defined during MNF generation, the node length of the stress/strain modes becomes shorter than that for the mode shapes. This reduces the amount of stress/strain data in the MNF, and allows you to avoid doubling the file size when including stress or strain modes. Adams/Durability, however, will only be able to recover stress or strain at those subregions.Support for this capability was first introduced in version 2005. Before 2005, a null tensor (all zero values) would be stored in the MNF for those nodes that did not have stress/strain computed by the FEA program. No reduction in file size was obtained, but worse yet, Adams/Durability would report zero stress/strain for those nodes, which could be misleading. In Adams/Flex 2005 or greater, it is now possible to remove these zero stress/strain states during MNF optimization. More information on how to do this is provided in the next sections.Starting in MSC.Nastran 2005, only grid point stresses that are computed for a subset of the component are output to the MNF. Support for this capability by the other FEA programs is not yet available. Learn more:• Note on MNF Compatibility• MNF Translation and Optimization• Version ScenariosNote on MNF CompatibilityIn general, an MNF is upward, but not necessarily backward, compatible. Adams will always support earlier versions of the MNF. For example, an MNF generated in a version of MSC.Nastran before 2005 will be supported. However, an MNF generated by MSC.Nastran 2005 or later will be incompatible in a version of Adams earlier than 2005. This is because, by default, MSC.Nastran generates a version of the MNF that supports shortened stress/strain modes, or in other words, a reduced MNF. However, an option exists in Adams/Flex to convert a reduced MNF to a full MNF, so that it can be processed by earlier versions of Adams.MNF Translation and OptimizationSupport for shortened stress/strain modes is available in the Adams/Flex MSC-> Translator and -> Optimizer through the menu option Stress & Strain Modes. Three options are available as listed in the table below.Version ScenariosExampleIn this MSC.Nastran example, ten shell elements (CQUAD4) are used to model a beam. Grid point strains are requested (GPSTRAIN) on only four of the elements (4,5,6,7) because of the SET 100 specification on the SURFACE card. This results in a reduced MNF with shortened strain modes on grids that are common to those elements (grids 104 through 108 and 204 through 208).SOL 103CEND$AdamsMNF FLEXBODY=YES,OUTGSTRN=YES,OUTGSTRS=NOMETHOD=300RESVEC=NO$STRAIN(PLOT)=ALLGPSTRAIN(PLOT)=ALLOUTPUT(POST)SET 100 = 4,5,6,7SURFACE 101 SET 100 NORMAL X3 FIBRE=Z1$BEGIN BULKASET1,123,101,111,201,211SPOINT,1001,thru,1003QSET1,0,1001,thru,1003DTI,UNITS,1,KG,N,M,SPARAM,GRDPNT,0$EIGRL 300 -1. 3$GRID 101 0. 0. 0.GRID 102 0.05 0. 0.GRID 103 0.1 0. 0.GRID 104 0.15 0. 0.GRID 105 0.2 0. 0.GRID 106 0.25 0. 0.GRID 107 0.3 0. 0.GRID 108 0.35 0. 0.GRID 109 0.4 0. 0.GRID 110 0.45 0. 0.GRID 111 0.5 0. 0.GRID 201 0. 0.03 0.GRID 202 0.05 0.03 0.GRID 203 0.1 0.03 0.GRID 204 0.15 0.03 0.GRID 205 0.2 0.03 0.GRID 206 0.25 0.03 0.GRID 207 0.3 0.03 0.GRID 208 0.35 0.03 0.GRID 209 0.4 0.03 0.GRID 210 0.45 0.03 0.GRID 211 0.5 0.03 0.$CQUAD4 1 1 101 102 202 201 CQUAD4 2 1 102 103 203 202 CQUAD4 3 1 103 104 204 203 CQUAD4 4 1 104 105 205 204 CQUAD4 5 1 105 106 206 205 CQUAD4 6 1 106 107 207 206 CQUAD4 7 1 107 108 208 207 CQUAD4 8 1 108 109 209 208 CQUAD4 9 1 109 110 210 209 CQUAD4 10 1 110 111 211 210 $MAT1 1 2.+11 .3 7800. PSHELL 1 1 .01 1ENDDATA。

Nastran与adams接口介绍通过MSC.NASTRAN软件与MSC.ADAMS软件之间的双向接口，可以将两个软件有机结合起来，实现将零部件级的有限元分析的结果传递到系统级的运动仿真分析中，完成在MSC.ADAMS中的考虑部件弹性影响的分析，同时还可以将MSC.ADAMS软件中的分析结果，如部件在各种工况下运动过程中的受力情况传递给MSC.NASTRAN，以此来定义其载荷的边界条件，从而可以提高了产品整体的分析结果的精度和置信度。

MSC.NASTRAN从2004版本开始，对与MSC.ADAMS的接口提供了更为简便的方法，从MSC.NASTRAN中可以直接生成的MSC.ADAMS软件所需要的模态中性文件（简称MNF 文件）, 这个过程可以在有限元通用的前处理软件MSC.PATRAN中方便实现。

这个接口可应用于模态分析、瞬态响应分析、频响分析以及有预加载荷的模态分析等分析过程中。

对于有非线性变形的部件，要首先使用非线性分析，再用模态分析重新进行计算。

MSC.Nastran生成MNF文件的过程通过在MSC.Patran 中的设定，可产生MNF文件。

MSC.Patran中直接生成mnf文件的过程如下：（1）在模态分析，瞬态分析或频响分析等分析选项中，选择solution parameters,选定msc.adams preparation。

（2）在msc.adams preparation.中对输出内容，输出单位等予以设定。

（3）提交MSC.Nastran分析，将产生mnf文件。

通过以上操作在MSC.Nastran中两个必需的命令将会产生（1）工况控制部分将有产生MNF文件的命令，MSC.ADAMSMNF FLEXBODY=YES（2）数据部分需要指定MSC.ADAMS/Flex单位的命令DTI, UNITS, 1, mass_unit, force_unit, length_unit, time_unit例如DTI,UNITS,1,KG,N,M,SECMSC.Nastran/Msc.adams接口实例下面通过三个例子来说明MSC.Nastran产生MNF文件的过程。

13柔性体介绍................................................ 错误!未定义书签。

柔性体引入ADAMS建模..................................... 错误!未定义书签。

打开原有的X5后悬架模板.............................. 错误!未定义书签。

将小连杆的模态中性文件导入ADAMS ..................... 错误!未定义书签。

利用Hyper Mesh及Motion View软件来生成模态中性文件MNF .. 错误!未定义书签。

创建小连接杆的CAD模型............................... 错误!未定义书签。

将iges格式文件导入到Hyper Mesh划分网格............. 错误!未定义书签。

创建材料............................................. 错误!未定义书签。

创建刚性单元......................................... 错误!未定义书签。

给刚性中心节点编号................................... 错误!未定义书签。

导出nastran模板格式文件............................. 错误!未定义书签。

创建h3d文件及MNF文件............................... 错误!未定义书签。

《柔性体篇》13柔性体介绍在模型中引入柔性体可以提高仿真的精度。

柔性体可采用模态中性文件（MNF）来描述。

该文件是一个二进制文件，包含了以下信息：几何信息（结点位置及其连接）；结点质量和惯量；模态；模态质量和模态刚度。

可以利用ANSYS、NASTRAN、ABAQUS等限元软件包进行分析并将结果写成模态中性文件，输入到ADAMS/View或ADAMS/Car中，建立相应零件的柔性体。

adams建立柔性体ADAMS是美国MDI公司开发的机械系统动力学仿真分析软件,其求解器采用多刚体动力学理论中的拉格朗日方程方法,建立系统动力学方程,对虚拟机械系统进行静力学、运动学和动力学分析,输出位移、速度、加速度和反作用力曲线。

对系统动力分析而言,结构本身的弹性变形与系统的宏观刚体运动同等重要。

ADAMS中的所有物体均以刚体定义,忽略结构柔度对系统的影响,一般的有限元分析软件对包含大位移运动的系统动力学分析又无能为力,因此在ADAMS中实现刚体和柔体相结合的系统动力学分析是一个较可行的解决方法。

1996年,ADAMS推出ADAMS/Flex模块,实现了同时包含刚体和柔体的机构动力学分析。

ADAMS中，有3种建立柔性体的方法：1.利用柔性梁连接，将一个构件离散成许多段刚性构件，离散后的刚性构件之间采用柔性梁连接，只适用于简单的构件，其实质还是刚性构件柔性连接，不算是真正的柔性体；离散柔性连接件：把一个刚性构件离散为几个小刚性构件，小刚性构件之间通过柔性梁连接，离散柔性连接件的变形是柔性梁连接的变形，并不是小刚性构件的变形，小刚性构件的任意两点不能产生相对位移，所以离散柔性连接件本质是刚性构件的范畴内。

每段离散件有自己的质心坐标系、名称、颜色和质量信息等属性，每段离散件是一个独立的刚性构件，可以像编辑其他刚性构件一样来编辑每段离散件。

柔性连接件的优点：这种柔性体可以模拟物体的非线性变形,但只适用于简单结构，可以直接帮助用户计算横截面的属性，比直接使用柔性梁连接将两个构件连接起来方便Build——Flexible bodies——Discrete Flexible LinkName：Dis_flex，系统自动按照Dis_flex_elem1、Dis_flex_elem2......的顺序给每个离散连接件起一个名称，Dis_flex_beam1、Dis_flex_beam2.......的顺序给每个柔性梁连接起一个名字Damping Ratio 设置柔性梁连接的粘性阻尼和刚度之间的比值Attachment 确定起始端和中终止端与其他构件之间的连接关系：free、刚性rigid、柔性flexible2.利用其他有限元分析软件将构件离散成细小的网格，进行模态计算，将计算的模态保存为模态中性文件MNF(Modal Neutral File)，直接读取到ADAMS中建立柔性体；由于采用的是模态线性叠加来模拟物体变形,因此模态式柔性体仅适用于线性结构的受力行为。

13柔性体介绍 (253)13.1柔性体引入ADAMS建模 (253)13.1.1打开原有的X5后悬架模板 (253)13.1.2将小连杆的模态中性文件导入ADAMS (254)13.2利用Hyper Mesh及Motion View软件来生成模态中性文件MNF (256)13.2.1创建小连接杆的CAD模型 (256)13.2.2将iges格式文件导入到Hyper Mesh划分网格 (257)13.2.3创建材料 (268)13.2.4创建刚性单元 (273)13.2.5给刚性中心节点编号 (282)13.2.6导出nastran模板格式文件 (283)13.2.7创建h3d文件及MNF文件 (284)《柔性体篇》13柔性体介绍在模型中引入柔性体可以提高仿真的精度。

柔性体可采用模态中性文件（MNF）来描述。

该文件是一个二进制文件，包含了以下信息：几何信息（结点位置及其连接）；结点质量和惯量；模态；模态质量和模态刚度。

可以利用ANSYS、NASTRAN、ABAQUS等限元软件包进行分析并将结果写成模态中性文件，输入到ADAMS/View或ADAMS/Car中，建立相应零件的柔性体。

13.1柔性体引入ADAMS建模在模型中引入柔性体首先要在ADAMS/Car中读入模态中性文件，然后ADAMS/Car会创建必要的几何实体用以显示柔性体。

然后在模型中与其它刚体部件之间施加约束。

本教程以后悬架的小连接板为例。

13.1.1打开原有的X5后悬架模板13.1.2将小连杆的模态中性文件导入ADAMS在ADAMS/Car中读入模态中性文件的过程如下：1）从Build菜单中选择Parts>Flexible Body>New设定对话框如下，在Left Modal Neutral File和Right Modal Neutral File里右击鼠标选择自己已经创建好的MNF文件，点击OK。

2）创建柔性体与刚体的中间连接体Interface Part柔性体不能直接与刚体建立约束，必须通过中间体来连接。

13柔性体介绍 (253)13.1柔性体引入ADAMS建模 (253)13.1.1打开原有的X5后悬架模板 (253)13.1.2将小连杆的模态中性文件导入ADAMS (254)13.2利用Hyper Mesh及Motion View软件来生成模态中性文件MNF (256)13.2.1创建小连接杆的CAD模型 (256)13.2.2将iges格式文件导入到Hyper Mesh划分网格 (257)13.2.3创建材料 (268)13.2.4创建刚性单元 (273)13.2.5给刚性中心节点编号 (282)13.2.6导出nastran模板格式文件 (283)13.2.7创建h3d文件及MNF文件 (284)《柔性体篇》13柔性体介绍在模型中引入柔性体可以提高仿真的精度。

柔性体可采用模态中性文件（MNF）来描述。

该文件是一个二进制文件，包含了以下信息：几何信息（结点位置及其连接）；结点质量和惯量；模态；模态质量和模态刚度。

可以利用ANSYS、NASTRAN、ABAQUS等限元软件包进行分析并将结果写成模态中性文件，输入到ADAMS/View或ADAMS/Car中，建立相应零件的柔性体。

13.1柔性体引入ADAMS建模在模型中引入柔性体首先要在ADAMS/Car中读入模态中性文件，然后ADAMS/Car会创建必要的几何实体用以显示柔性体。

然后在模型中与其它刚体部件之间施加约束。

本教程以后悬架的小连接板为例。

13.1.1打开原有的X5后悬架模板13.1.2将小连杆的模态中性文件导入ADAMS在ADAMS/Car中读入模态中性文件的过程如下：1）从Build菜单中选择Parts>Flexible Body>New设定对话框如下，在Left Modal Neutral File和Right Modal Neutral File里右击鼠标选择自己已经创建好的MNF文件，点击OK。

2）创建柔性体与刚体的中间连接体Interface Part柔性体不能直接与刚体建立约束，必须通过中间体来连接。

13柔性体介绍................................................ 错误!未定义书签。

柔性体引入ADAMS建模..................................... 错误!未定义书签。

打开原有的X5后悬架模板.............................. 错误!未定义书签。

将小连杆的模态中性文件导入ADAMS ..................... 错误!未定义书签。

利用Hyper Mesh及Motion View软件来生成模态中性文件MNF .. 错误!未定义书签。

创建小连接杆的CAD模型............................... 错误!未定义书签。

将iges格式文件导入到Hyper Mesh划分网格............. 错误!未定义书签。

创建材料............................................. 错误!未定义书签。

创建刚性单元......................................... 错误!未定义书签。

给刚性中心节点编号................................... 错误!未定义书签。

导出nastran模板格式文件............................. 错误!未定义书签。

创建h3d文件及MNF文件............................... 错误!未定义书签。

《柔性体篇》13柔性体介绍在模型中引入柔性体可以提高仿真的精度。

柔性体可采用模态中性文件（MNF）来描述。

该文件是一个二进制文件，包含了以下信息：几何信息（结点位置及其连接）；结点质量和惯量；模态；模态质量和模态刚度。

可以利用ANSYS、NASTRAN、ABAQUS等限元软件包进行分析并将结果写成模态中性文件，输入到ADAMS/View或ADAMS/Car中，建立相应零件的柔性体。

分析时如果不考虑柔性体的影响将会造成很大的误差,同；分析步骤；利用A NSYS与ADAMS接口,对运动系统中的柔；在ANSYS软件中建立柔性体部件的有限元模型并利；在ADAMS软件中建立好刚性体的模型,读入模态中；在ANSYS程序中,将载荷文件中对应时刻的载荷施；在ANSYS软件中生成ADAMS软件使用的柔性体；进入ANSYS程序，建立柔性体的模型，并选择适当；分析时如果不考虑柔性体的影响将会造成很大的误差,同样整个系统的运动情况也反过来决定了每个构件的受力状况和运动状态,从而决定了构件内部的应力应变分布.因此如果要精确地模拟整个系统的运动,考虑柔性体部件对系统运动的影响,或者想基于精确的动力学仿真结果, 对运动系统中的柔性体进行应力应变分析则需要用到AN SYS与ADAMS两个软件.分析步骤利用ANSYS与ADAMS接口,对运动系统中的柔性体部件进行应力应变分析的完整步骤如下：在ANSYS软件中建立柔性体部件的有限元模型并利用adams.mac宏文件生成ADAMS软件所需要的柔性体模态中性文件(jobname.mnf)；在ADAMS软件中建立好刚性体的模型,读入模态中性文件,指定好部件之间的连结方式,施加必要的载荷进行系统动力学仿真,在分析完成后输出ANSYS所需要的载荷文件(.lod文件),此文件记录了运动过程中柔性体的运动状态和受到的载荷；在ANSYS程序中, 将载荷文件中对应时刻的载荷施加到柔性体上对柔性体进行应力应变分析。

在ANSYS软件中生成ADAMS软件使用的柔性体模态中性文件(.mnf文件)进入ANSYS程序，建立柔性体的模型，并选择适当的单元类型来划分单元。

在柔性体的转动中心（与刚性体的联接处）必须有节点存在，此节点在ADAMS 中将作为外部节点使用，如果在联接处柔性体为空洞，则需在此处创建一节点,并使用刚性区域处理此节点（外部节点）与其周围的节点。

选择外部节点,运行ANSYS程序的宏命令ADAMS生成ADAMS程序所需要的模态中性文件(jobname.mnf)。

ADAMS是美国MDI公司开发的机械系统动力学仿真分析软件,其求解器采用多刚体动力学理论中的拉格朗日方程方法,建立系统动力学方程,对虚拟机械系统进行静力学、运动学和动力学分析,输出位移、速度、加速度和反作用力曲线。

对系统动力分析而言,结构本身的弹性变形与系统的宏观刚体运动同等重要。

ADAMS中的所有物体均以刚体定义,忽略结构柔度对系统的影响,一般的有限元分析软件对包含大位移运动的系统动力学分析又无能为力,因此在ADAMS中实现刚体和柔体相结合的系统动力学分析是一个较可行的解决方法。

1996年,ADAMS推出ADAMS/Flex模块,实现了同时包含刚体和柔体的机构动力学分析。

ADAMS中，有3种建立柔性体的方法：1.利用柔性梁连接，将一个构件离散成许多段刚性构件，离散后的刚性构件之间采用柔性梁连接，只适用于简单的构件，其实质还是刚性构件柔性连接，不算是真正的柔性体；离散柔性连接件：把一个刚性构件离散为几个小刚性构件，小刚性构件之间通过柔性梁连接，离散柔性连接件的变形是柔性梁连接的变形，并不是小刚性构件的变形，小刚性构件的任意两点不能产生相对位移，所以离散柔性连接件本质是刚性构件的范畴内。

每段离散件有自己的质心坐标系、名称、颜色和质量信息等属性，每段离散件是一个独立的刚性构件，可以像编辑其他刚性构件一样来编辑每段离散件。

柔性连接件的优点：这种柔性体可以模拟物体的非线性变形,但只适用于简单结构，可以直接帮助用户计算横截面的属性，比直接使用柔性梁连接将两个构件连接起来方便Build——Flexible bodies——Discrete Flexible LinkName：Dis_flex，系统自动按照Dis_flex_elem1、Dis_flex_elem2......的顺序给每个离散连接件起一个名称，Dis_flex_beam1、Dis_flex_beam2.......的顺序给每个柔性梁连接起一个名字Damping Ratio 设置柔性梁连接的粘性阻尼和刚度之间的比值Attachment 确定起始端和中终止端与其他构件之间的连接关系：free、刚性rigid、柔性flexible2.利用其他有限元分析软件将构件离散成细小的网格，进行模态计算，将计算的模态保存为模态中性文件MNF(Modal Neutral File)，直接读取到ADAMS中建立柔性体；由于采用的是模态线性叠加来模拟物体变形,因此模态式柔性体仅适用于线性结构的受力行为。

Nastran生成柔性体mnf文件的方法（北京诺思多维科技有限公司内部资料，forengineer@ 未经授权，严禁传播）Nastran软件只是有限元求解器，需要前处理软件生成提交给Nastran计算的模型文件，前处理软件有很多，不论用哪个前处理，输出的Nastran模型文件格式都相同。

Nastran原来由多家公司所共同开发，所以有多个Nastran版本，如NEi Nastran、CSA/NASTRAN、UAI/NASTRAN、MSC NASTRAN、SAS/NASTRAN、COSMIC NASTRAN、VR/Nastran和NX/NASTRAN，其中就计算精度和计算速度来讲，NEi Nastran都要领先于其他版本的Nastran和有限元求解器。

Nastran的求解功能如下所示：●LINEAR STATIC（线性静力分析）●PRESTRESS STATIC（线性预应力静力学分析）●NONLINEAR STATIC（非线性静力学分析）●MODAL（模态分析）●MODAL COMPLEX EIGENVALUE（复特征值分析）●LINEAR PRESTRESS MODAL（线性预应力模态分析）●NONLINEAR PRESTRESS MODAL（非线性预应力模态分析）●LINEAR PRESTRESS COMPLEX EIGENVALUE（线性预应力幅特征值分析）●NONLINEAR PRESTRESS COMPLEX EIGENVALUE（非线性预应力复特征值分析）●LINEAR BUCKLING（线性屈曲分析）●NONLINEAR BUCKLING（非线性屈曲分析）●DIRECT FREQUENCY RESPONSE（直接法频率响应分析）●MODAL FREQUENCY RESPONSE（模态法频率响应分析）●LINEAR PRESTRESS FREQUENCY RESPONSE（线性预应力频率响应分析）●NONLINEAR PRESTRESS FREQUENCY RESPONSE（非线性预应力频率响应分析）●DIRECT TRANSIENT RESPONSE（直接法瞬态响应分析）●MODAL TRANSIENT RESPONSE（模态法瞬态响应分析）●NONLINEAR TRANSIENT RESPONSE（非线性瞬态响应分析）●LINEAR PRESTRESS TRANSIENT RESPONSE（线性预应力瞬态响应分析）●NONLINEAR PRESTRESS TRANSIENT RESPONSE（非线性预应力瞬态响应分析）●LINEAR STEADY STATE HEAT TRANSFER（线性稳态热传递分析）●NONLINEAR STEADY STATE HEAT TRANSFER（非线性稳态热传递分析）●NONLINEAR TRANSIENT HEAT TRANSFER（非线性瞬态热传递分析）Nastran的模型文件是文本文件，可以用文本编辑软件，如记事本、写字板等打开进行编辑，对Nastran 的详细使用可以参考本书作者所著的《Nastran快速入门与实例》一书。