S2-1 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation SECTION 2 MSC.NASTRAN THERMAL ANALYSIS. - презентация

1 S2-1 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation SECTION 2 MSC.NASTRAN THERMAL ANALYSIS

2 S2-2 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation

3 S2-3 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation OVERVIEW n Why a Structural Analyst may have to perform Thermal Analysis n Modes of Heat Transfer Available in MSC.NASTRAN and MSC.Patran support u Conduction u Convection u Radiation u Transient Analysis versus u Steady State Analysis n Linear versus Nonlinear n Thermal Stress analysis

4 S2-4 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation HEAT TRANSFER Motivation n When the solution for the temperature field in a solid (or fluid) is desired, and the temperature is not influenced by the other unknown fields, a heat transfer analysis is appropriate. q= -k [dT/dx] T1T1 T2T2 T 1 >T 2 q Conduction Modes of Heat Transfer T2T2 AdvectionRadiation T1T1 T2T2 T 1 >T 2 q1q1 q2q2 T1T1 q Convection T2T2 Moving Fluid Removes Heat From Solid T 1 >T 2 q T2T2 T1T1 Heat Moves IN Moving Fluid

5 S2-5 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Motivation When the solution for the temperature field in a solid (or fluid) is desired,and is not influenced by the other unknown fields, heat transfer analysis is appropriate. HEAT TRANSFER MODES Boundary Conditions : Thermal Convection Forced convection Advection(fluid flow) Natural convection Radiation

6 S2-6 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Thermal equilibrium between heat sources, energy flow density and temperature rate is expressed by the Energy Conservation Law, which may be written: Energy flow density is given by a diffusion and convection part: where is L is the conductivity matrix. Assume that the continuum is incompressible and that there is no spatial variation of r and Cp; then the conservation law becomes: HEAT TRANSFER MATHEMATICS

7 S2-7 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation HEAT TRANSFER LOADS & BOUNDARY CONDITIONS

8 S2-8 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation contact HEAT TRANSFER LOADS & BOUNDARY CONDITIONS (CONT.)

9 S2-9 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Only in transient analysis: HEAT TRANSFER INITIAL CONDITIONS.

10 S2-10 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.NASTRAN THERMAL PREFERENCE TABLE (MSC.PATRAN) n The following table outlines the options when the Analysis Type is set to NASTRAN Thermal: ObjectTypeOption RadiationNodal Element Uniform Ambient Space Enclosures(View factor) ConventionNodal Element Uniform To ambient Flow tube to Ambient Coupled Coupled Flow tube Coupled Advection Duct Flow Time Function Spatial field HeatingNodal Element Uniform Element Variable Normal Fluxes Directional Fluxes Nodal Source Volumetric Generation Time function Spatial field TemperatureNodalFixedTime function Spatial field Initial TempNodalInitialTime function Spatial field

11 S2-11 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.NASTRAN FINITE ELEMENTS TypeElements 1DBAR,BEAM,BEND,ROD, TUBE 2DTRIA3,TRIA6,QUAD4, QUAD8 3DHEXA,PENTA,TETRA ScalarCELAS1 or CELAS2, CDAMP2 Axi-symmetricCTRIAX6

12 S2-12 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation

13 S2-13 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.NASTRAN BULK DATA ENTRIES

14 S2-14 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation

15 S2-15 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.Nastran Input File

16 S2-16 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.Nastran Input File (Cont.) File Management Section (FMS): Includes the "NASTRAN" statement (optional - determines overall program control for the current run Allocates files, controls restarts and database operations The goal of the File Management Section is to make the operating system invisible to the user Executive Control Section: Solution type, time allowed, program modifications and system diagnostics Case Control Section Output requests and selects certain Bulk Data items such as loadings and constraints to be used Bulk Data Section Structural model definition and solution conditions

17 S2-17 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.Nastran Input File (Cont.) n The Bulk Data section is where you provide the description of the model and the loading conditions and constraints n As mentioned in the previous section, the Executive Control section provides overall control of the solution and the Case Control provides the control of the individual loadings to be applied and the output requests

18 S2-18 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Introduction to the Bulk Data Section The Bulk Data Section contains all data necessary for describing a structural model Bulk Data definitions include Geometry User-definable coordinate systems Geometric locations of grid points Constraints Material Properties Element Properties Loads The Bulk Data is not required to be input in any set order. It is automatically sorted (alphabetically) at the beginning of the analysis

19 S2-19 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Format of Bulk Data n The format of the Bulk Data section is based each line: u having 80 possible columns u being divided into 10 fields n Each item described in the Bulk Data section is called an Entry n Each Entry may span multiple lines n The format of each Entry is pre-defined - the format of each entry is described in the MSC.NASTRAN Quick Reference Guide (QRG), section 5 n Only a few basic entries will be described in this set of notes n Not all options will be discussed for each entry - for a full description, check the QRG

20 S2-20 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Sample Bulk Data Entry

21 S2-21 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Format of Bulk Data Entries Data in each field may be: Integer5 Real1.0E+7 BCD(Character String) Each field of the input has a pre-determined data type. You must enter you data correctly An integer number has no decimal point Examples:

22 S2-22 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Format of Bulk Data Entries (Cont.) n Real data has a decimal point and may have an exponent n There are several ways to represent real numbers n For example, the real value might be represented using any of the following: E E3 n These all represent the same number

23 S2-23 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Format of Bulk Data Entries (Cont.) n BCD (or character) data is represented as a text string n It must start with a letter (A-Z) n It may contain numbers in the text (0-9) n It must be 8 or fewer characters long n No special characters or embedded blanks may be used n Examples: TEST123 X32 DUM1

24 S2-24 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Format of Bulk Data Entries (Cont.) n The first field of an entry is its name n All subsequent fields provide data as defined for that entry in the QRG n If an entry spans more than one line, then a continuation is needed n Each line of input will use one of three formats: u Small Field u Free Field u Large Field

25 S2-25 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Small Field Format n When using Small Field, each line is divided into 10 fields n Each field is 8 columns long n This is the format used by most pre-processing programs when writing an input file for MSC.Nastran n Example Small Field Entry n When using small field, you must be sure to count the number of columns for each field n There is no requirement that numbers be right- or left-justified (the program handles this for you)

26 S2-26 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Free Field Format n This is similar to small field, but fields are separated by either a comma or a space (using commas is recommended) n Rules: u To skip a field, use two commas in succession u Integers or BCD fields with more than 8 characters will result in a FATAL error u Real numbers with more than 8 characters will be rounded off to 8 characters (therefore, some precision will be lost) n Example: (Same entry as on the previous page) GRID,10,,7.5,8.6,9.,,456

27 S2-27 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Large Field Format n Expands a line in the Bulk Data to 2 lines n When used: u The first and last fields of each line are 8 columns u The intermediate fields are 16 columns (there are only 4 intermediate fields per line - resulting in each line being 80 columns long) n Large Field is denoted by adding an asterisk (*) after the name in the first field of an entry and by an asterisk(*) in the first column of the second line of the entry n See next page for the format

28 S2-28 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Large Field Format (Cont.) n Sample Large Field Format Entry:

29 S2-29 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation General Input Format Rules n Errors result if data extends beyond its field into another field n Fields 1 and 10 must be left justified. Fields 2 through 9 do not have this requirement n Input items should not have embedded blanks

30 S2-30 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation General Input Format Rules (Cont.) n All Real numbers (including zero) must have a decimal point (This is a common error) n Many fields have a default value, if these fields are left blank, the default value will be used (See the QRG)

31 S2-31 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Continuation Entries n Many input entries require more than one line of input n If this is the case, then continuation entries must be used n Continuation entries may be generated automatically when the entries are in sorted order. The parent entry must be blank in columns (field 10), and the continuation entry must be blank in columns 2-8 (field 1). For small field entries, the first column of the continuation entry may be blank or contain a + symbol. For large field entries, the first column of the continuation entry must contain a * symbol

32 S2-32 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Continuation Entries (Cont.) Input rules u Unless you use automatic generation, a (+) or (*) is required in column 1, field 1 of a continuation entry. The remaining contents in field 1 of a continuation entry must be identical to the entry in field 10 (columns 2 through 8) of the parent entry (or the preceding continuation entry) u Any entry in the first column of field 10 on the parent entry is ignored by the continuation entry u Small field and large field continuation entries may be used together in defining a single data item entry n An example of this is shown on the next page

33 S2-33 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Continuation Entries (Cont.)

34 S2-34 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Input Generation – Replication To avoid the time-consuming input of each Bulk Data entry individually, repetitive fields can be generated from a single entry definition. Rules governing this capability are: Duplication of a field from the preceding entry is accomplished by coding the symbol = in the associated field Duplication of all remaining fields from the preceding entry is accomplished by coding the symbol == in the first of the fields to be repeated Generation of a incremented value from the previous entry is defined by coding *X or *(X) where X is the real or integer value of the increment (Note: Parentheses are optional) Repeated replication is indicated by coding =n or the optional =(n) in field 1, where n is the number of entry images to be generated using the values of the increments on the preceding generation entry

35 S2-35 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Input Generation – Replication (Cont.) n Generation/replication rules apply to all Bulk Data entries unless denoted otherwise on specific entry definition pages in the QRG. n Preprocessing programs generally generate a separate entry for each item and do not use replication. n In this seminar and others, we often use replication as a method to shorten the file so that we can show the complete input, rather than just showing parts of it

36 S2-36 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Generation of Continuation Entries Continuation fields (fields 1 and 10) may be replicated using the following conventions Only letters of the alphabet and integers may be used. They are coded into a base 36 number. That is, the sequence of numbers is 0, 1, 2,...8, 9, A, B,...Z. The first character in the field 1 or 10 is not incremented MSC.Nastran increments continuation fields by +1. The number of characters in an incremented field is not increased. For example, if the field in the first entry is 0, the field in the 37th entry is also 0 resulting in an illegal duplicate entry. A method to solve this problem is to start a first entry with 00. This will provide 36 squared unique fields See Section of the MSC/NASTRAN Handbook for Linear Analysis for examples of continuation entries in small field and large field formats

37 S2-37 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Example of Replication

38 S2-38 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Bulk Data Generated by Replication Example

39 S2-39 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.NASTRAN REPLICATION COMMAND n chbdyp,10,10,line,,,1,2,1 n =,*1,=,=,=,=,*1,*1,== n =7 n CHBDYP LINE n CHBDYP LINE n CHBDYP LINE n CHBDYP LINE n CHBDYP LINE n CHBDYP LINE n CHBDYP LINE n CHBDYP LINE n CHBDYP LINE

40 S2-40 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Replicate the continuity cards n CHBDYG,EID,,TYPE,IVIEWF,IVIEWB,RADMIDF,RADMIDB,+ n +,G1,G2,G3,G4,G5,G6,G7,G8 n CHBDYG,21,,REV,,,,,,,+C1 n +C1,201,202 n CHBDYG,22,,REV,,,,,,,+C2 n +C2,202,203 n CHBDYG,21,,REV,,,,,,,+C1 n =,*1,=,=,=,=,=,=,=,*1 n =7 n +C1,201,202 n *1,*1,*1 n =7

41 S2-41 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation Common Errors in Entry Format n The following are recommendations on how to avoid some commonly made errors in the input Failure to leave the proper number of fields blank when defining data values causes either a fatal error or wrong answers. Be sure to leave the proper number of blanks or include the correct number of commas to delimit data fields Be sure to use the correct format for integer numbers and real numbers. See individual entry format in the MSC/NASTRAN Quick Reference Guide for these specifications Be sure to define all the required fields for the Bulk Data entries

42 S2-42 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation FORMAT OF THE DAT FILE NASTRAN statement (optional) File Management (Use for restart purpose) Executive Control (required - sets solution type) CEND (keyword delimiter) Case Control (declares loads/output requests) BEGIN BULK (keyword delimiter) Bulk Data (specifies model details) ENDDATA (keyword delimiter)

43 S2-43 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation FILE MANAGEMENT n Principal uses u Initialization of the MSC.Nastran database u Restarts u Controlling scratch space - requires manual input u Assigning file units (e.g. to produce output for MSC/PATRAN) - requires manual input

44 S2-44 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation EXECUTIVE CONTROL n Principal uses u Specify MSC.Nastran solution sequence u Specify maximum allowable CPU time n Example: u SOL 153 (Nonlinear steady-state thermal solution sequence) u CEND

45 S2-45 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation CASE CONTROL n Principal uses u Select desired loading and boundary conditions u Specify convergence criteria u Request output sets (sent F06, XDB and/or punch file)

46 S2-46 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation CASE CONTROL - STEADY STATE EXAMPLE ANALYSIS = HEAT (analysis type ) ECHO = NONE (BULK DATA echo control) THERMAL = ALL (nodal temperatures) SPCFORCE = ALL (nodal constraint heats) FLUX = ALL (element fluxes/gradients) SPC = 1 (select constraint set) LOAD = 1 (select static load)

47 S2-47 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation NASTRAN INPUT TEST DECK n BEGIN BULK n $ Direct Text Input for Bulk Data n $ Elements and Element Properties for region : rod n GRID n GRID n CROD n PROD n $ Description of Material : Date: 03-Jun-98 Time: 15:43:43 n MAT

48 S2-48 NAS104, Section 2, March 2004 Copyright 2004 MSC.Software Corporation MSC.NASTRAN FILES n DATInput file describing FE model and run parameters n F06ASCII results file n XDB Binary results file n F04Run history(disk space used, files assigned, etc.) n LOGSummary of execution links n DBALLMain database - contains assembled matrices and solutions(required for restart) n MASTERServes as a directory listing of files used during a run(required for restart)