nastran创建mnf流程.doc

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）PARAM

Param fixedb -1
Param autospc yes
Param post，0
(3) case_unsupported_cards

一般有以下部分：
ADAMSMNF FLEXBODY=YES,OUTGSTRN=YES,OUTGSTRS=yes，EXPORT= BOTH

RESVEC=yes，STRFIELD = ALL
GPSTRESS=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 z
Set 103=all
Volume 104 set 103 , direct **定义实体单元集的体积
(4) bulk _unsupported _cards

DTI,UNITS,1,KG,N,M,S
(5) global_case_control
Output 栏中
点选EIGRL卡

Super=1
Method=1
Stress（plot）=all
Strain（fiber，plot）=all
Gpstress=all
Gpstrain=all

Create an MD DB using MD Nastran
MD 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 DB
BOTH: generate both MNF and DB
Please refer to MD Nastran Quick Reference Guide and Reference Manual for details.
Use Flex Toolkit to convert MNF to MD DB
Use can also use the mnf2mtx utility to convert MNF to MD DB. The usage is:
adams flextk mnf2mtx source.mnf -O dest.MASTER
where 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
then
adams flextk mnf2mtx source2.mnf -O dest.MASTER
will append the flexible body in source2.mnf to dest.MASTER with INDEX=2.

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Translating FE Model Data > Translating MSC.Nastran Data

Translating MSC.Nastran Data
There 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

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Verifying the Model
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Computing MSC.Nastran Stress/Strain Modes

•
MSC.Nastran XDB Support for Stress/Strain Modes
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Shortened Stress/Strain Modes
Using MSC.Nastran 2004 and Above
Starting 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 2001
Learn more about translating MSC.Nastran data using later versions of MSC.Nastran:
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About the MSC.Nastran DMAP and OUTPUT2 to MNF Translator
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Defining Your FE Model

•
Running MSC.Nastran
•
Running the Translator

•
Technical Notes on the MSC.Nastran DMAP

Note:  
Versions 69.x, 70.x, and 2001 of MSC.Nastran must be licensed to use the DMAP alters and run solution 103. MSC.VisualNastran for Windows does not meet these requirements.
About the MSC.Nastran DMAP and OUTPUT2 to MNF Translator
To generate a modal neutral file (MNF) in versions 69.x, 70.x, or 2001 of MSC.Nastran, you need:
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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 the Adams distribution.
•
msc2mnf.exe - MSC.Nastran OUTPUT2 file to MNF translator. It is an executable translator that reads the MSC.Nastran OUTPUT2 file and writes MNFs.
The mnfx.alt DMAP alter extracts flexible body information from MSC.Nastran. It uses the superelement 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 Model
The 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.alt
install_dir/flex/examples/MSCNASTRAN/v70/mnfx.alt
install_dir/flex/examples/MSCNASTRAN/v70.7/mnfx.alt
install_dir/flex/examples/MSCNASTRAN/v2001/mnfx.alt
5.
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=unformatted

Note:  
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,-1

Note:  
Loads, boundary conditions, and output requests are not necessary to the extent they are in a conventional analysis.
Running MSC.Nastran
You 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.
Format
nastran 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 Description

bat
Batch submittal flag. bat = yes requests that the job is run in a batch or background process. (Default = yes)
scr
Database control flag. scr = yes requests that all data is stored in temporary database files and the database files deleted at the end of the run. This is recommended if disk storage is a concern. (Default = no)
sdir
Scratch directory name. (The default is the temporary or scratch directory established by your system administrator). For large models, it is often necessary to set the scratch directory to a separate disk from where the assign statement in Step 5 of Defining Your FE Model directs the MSC.Nastran output file.
Running the Translator
Once 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:
•
In a command window on any platform.
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Through the Adams/Flex Toolkit, which you access through Adams toolbar on UNIX and the Start Menu on Windows.
For instructions about running the translator through the Adams/Flex toolkit, see Running the MSC.Nastran Translator.
Before running the translator, be sure to set up the translation as explained in Setting Up Translation Options 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.out
Also, 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 DMAP
The 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 Units
More on DMAP Alter
The 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 Optional Parameters 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 be read.

•
Multiple coordinate systems because all quantities are transformed to the basic coordinate system prior to 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 modes
•
Modal loads (PAE) if specified
Note 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 Set
You can set the following parameters in BULK DATA before translating the model using the param,name,value format:

The option:
Does the following:
Orthonormalization range
In general, some of the Craig-Bampton modes in the flexible body will be of extremely high frequency, leading to potential ill-conditioning of the eigenvalue extraction problem. By default, the translator only uses those modes below 1.0e8 Hz, in addition to using the rigid body modes of the structure. The parameters v1ortho and v2ortho set the limits. They have default values of -1.0 and 1.0e8, respectively. You can change the values using the BULK DATA param statement.
Orthonormalization diagnostics
You can obtain orthonormalization diagnostic information by setting the parameter msglvl to any value from 0 to 4. For example, you can set it to 1:
param, msglvl, 1
The default is 0.
Additional diagnostics
You can obtain additional diagnostic output by setting the parameter check to any nonzero value. For example, set it to:
param, check, 1
The default is check,0, or no diagnostic output. For any models of realistic size, you should not set diagnostic output.
Residual load vectors
You can augment the component modes with a deformed mode of the residual load vector of each static load case. For example, set it to:
param, resvec, yes
The default is No.
Element stress or strain modes
You can store element-based stress or strain modes in the MSC.Nastran output file by setting the parameter outstr to any nonzero value. For example, set it to:
param, outstr, 1
The default (0) is to store grid-based stress or strain modes. If you store element-based stress or strain modes in the output file, they will not be transferred to the MNF because the MNF supports only grid-point stress or strain modes. This option is useful if you want to recover element stresses or strains in, for example, MSC.Patran for an MSC.Fatigue analysis, and you are not interested in postprocessing stresses or strains in Adams.
Setting Units
Because 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 TIME
For example, you can enter the following for units:
DTI UNITS 1 KG N M S
Unit Labels

For:
Enter the following:
Unit:
Abbreviation:
Mass
kilogram
pound-mass
slug
gram
ounce-mass
kilopound-mass
megagram
kg
lbm
slug
gram
ozm
klbm
mgg
Force
Newton
pounds-force
kilograms-force
ounce-force
dyne
kilonewton
kilopound-force
millinewton
n
lbf
kgf
ozf
dyne
kn
klbf
mn
Length
kilometer
meter
centimeter
millimeter
mile
foot
inch
km
m
cm
mm
mi
ft
in
Time
hour
minute
second
millisecond
h
min
s
ms

Note:  
Although you need the MSC.Nastran's WTMASS parameter to ensure consistent units in MSC.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, S
On 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, S
Applying 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 Model
The 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