In today's software market, much effort is being expended on the development of data base management systems (DBMS). Most commercially available DBMS were designed for business use. However, the need for such systems within the engineering and scientific communities is becoming apparent. A potential DBMS application that appears attractive is the handling of data for finite element engineering models. The applications of a commercially available, business-oriented DBMS to a structural engineering, finite element model is explored. The model, DBMS, an approach to using the DBMS, advantages and disadvantages are described. Plans for research on a scientific and engineering DBMS are discussed

Rogers, J. L., Jr.

English

NASA Technical Reports Server

APPLICATIONOF A DATABASEMANAGEMENTSYSTEMTO A
FINITE ELEMENTMODEL
James L. Rogers, Jr.
Langley Research Center
INTRODUCTION
In today's software market, much effort is being expended on the develop-
ment of data base management systems (DBMS). Most commercially available
DBMSwere designed for business use. However, the need for such systems with-
in the engineering and scientific communities is becoming apparent.
A potential DBMSapplication that appears attractive is the handling of
data for finite element engineering models. The purpose of this paper is to
explore the application of a commercially available, business-oriented DBMS
to a structural engineering, finite element model. The model, DBMS,an
approach to using the DBMS,advantages and disadvantages are explored in de-
tail; and plans for research on a scientific and engineering DBMSare dis-
cussed.
THE FINITE ELEMENTMODEL
Many organizations use more than one finite element computer program
for analyzing structural models. For instance NASTRANmight be used because
of its generality, standardization, and universal acceptance, or SPAR
might be used to gain quick turnaround and interactive capability. Input
into these programs usually consists of data representing a finite element
model. Typically, the model has a single physical representation which
can easily be pictured as a hierarchial structure composed of the complete
model, substructures, elements, and grid points (see fig. I). This single
representation, however, can take the form of input to any one or more of
the many finite element programs available today.
If an engineer wishes to use more than one application program for
analysis, a separate input deck must be maintained for each program, although
in truth only one model is being analyzed. This proliferationof input
decks can lead to a loss of integrityin the data, becauseof the difficulty
in keepingall relatedinput decks at the same level of modification--
especiallywhen many changesare being made to the model. To solve the
proliferationproblemand maintain integrityof the data, the finiteelement
model input data can be stored in a data base.
223
https://ntrs.nasa.gov/search.jsp?R=19800016168 2020-03-21T19:01:08+00:00Z
THE DATABASEMANAGEMENTSYSTEM1
Storing the model input data in a data base independent of all the
application programs that are to make use of it as input can solve the
problem of proliferation of input decks and aid in maintaining the integrity
of the model. The data base is loaded into the DBMSin the steps shown
in figure 2. Step 1 simply defines a data base name for the user to work
with. The model input data must now be stored in data elements, the basic
components of a data base. By using the data base definition the hierarchial
structure of the finite element model is easily adapted to the hierarchial
structure of the data base. A typical data base definition is shown in
figure 3. Particular attention should be paid to its generality and its
hierarchial arrangement. Most any finite element model, large or small,
can be input with this definition. The hierarchial structure can be seen
by scanning the indentation of the definition. Data element 1 allows
input of a model name. Data element 2 is a repeating group (RG) of sub-
structures. A repeating group allows more than one substructure per model
to be input. Data element 3 allows input of a substructure name. Data
element 4 is a repeating group of finite elements within a substructure.
Data elements 5-10 provide for input of element information. Data element
II is a repeating group of grid points within a finite element. Data elements
12-16 provide for input of grid point information. Data elements 20-49
define supporting information (not necessarily hierarchial) about the
model such as element properties, single point constraints, omitted coordinates,
and eigenvalue information. Step 3 (fig. 2) inputs the finite element
model into the data base through the data base definition.
After the data has been loaded into the data base, it cannot be used in
an application program without undergoing some sort of conversion. The
easiest approach when working with already existing programs, is to use
FORTRANpre-processor programs to convert the data from the independent
data base format to an input format for a particular application program
such as NASTRANor SPAR(see fig. 4). Pre-processor programs for converting
data base input into NASTRANand SPARinput decks are shown in Appendices
I and II, respectively. A different pre-processor is needed for each
application program that will use the model data as input. A data manipulation
language (DML) which can be embeddedwithin the pre-processor programs allows
the user to write a FORTRANprogram that will interact with the data base.
The DMLstatements of the programs in the appendices have *PL in columns I-3.
ISYSTEM2000, a commercially available data base management system developed
by MRI Systems Corporation, was used for all research done for this paper.
However, almost any DBMSwith a FORTRANprocedural language and query language
could have been used. Use of commercial products and names of manufacturers
in this report does not constitute an official endorsement of such products or
manufacturers either expressed or implied, by the National Aeronautics and
Space Administration.
224
Another powerful tool of some DBMSis the query language. This language
allows the user to interactively query the data base. Using this language,
he can list the grid points associated with a particular finite element or
vice-versa he can list the finite elements associated with a particular grid
point. Many other associations can be listed depending upon the relationships
defined in the data base definition.
This has only been a brief introduction into the world of DBMS. More
details concerning the data base definition, data base input, DML, query
language, and creation of a data base, can be obtained from manuals available
from the developer of a specific DBMS.
APPLILCATIONOF A DBMSTO A FINITE ELEMENTCANTILEVERBEAM
The data base input of a cantilever beam is shown in figure 5. Close
attention should be paid to the correlation of numbers between figure 3 (data
base definition) and figure 5 (data base input). To demonstrate the process
shown in figure 4, a cantilever beam finite element model is created (see
fig. 6). The data base definition and data base input described above and
shown in figures 3 and 5 are used in this demonstration. After the data is
stored in the data base, it is input into the pre-processor programs shown
in appendices. Other input that does not pertain to the model but is necessary
input to NASTRANand SPAR(e.g., Executive and Case Control decks of NASTRAN)
are read in from another file and inserted into the proper place in the output
from the pre-processor programs. The pre-processor program for NASTRANis not
set up to handle PARAMand CNGRNTBulk Data cards, thus these cards are also
read from the same file as the Executive and Case Control cards. The pre-
processor programs could be expanded and made sufficiently general to handle
almost any input requirement. The pre-processor programs output a file ready
for input into either NASTRAN(fig. 7) or SPAR(fig. 8). Thus it is shown
that a finite element model data can be stored in a data base, independent of
any application program which would use the model data as input. With the aid
of pre-processor FORTRANprograms, the model data can subsequently be converted
to a format for direct input into one of several application programs.
ADVANTAGESANDDISADVANTAGES
The advantages in using a data base to store a finite element model have
been discussed in detail in previous sections so only a summary appears in
this section. The data base requires only one copy of the model to be stored
even though the data may be used as input to more than one application program.
This situation aids in maintaining the integrity of the model, especially
a model undergoing frequent changes. The stored data are independent of the
application programs that use it, thus changes can be made to the programs
and/or the data without having cross effects. A query language in the DBMS
gives the user easy interactive access to the data, allowing listings of many
types of data elements and cross-references between data elements.
225
The use of a DBMSis not without disadvantages. Of primary importance
is the computer storage overhead (disk space) required to store a model. The
small cantilever beam problem described earlier took almost II,00010 words of
storage. Changing the NON-KEYvalues to KEY in the data base definition re-
sults in the data base requiring 23,50010 words of storage. (A KEY value per-
mits the user to make sorts on that particular data element.) The user must
judiciously choose which data elements are KEYto minimize storage overhead.
Another disadvantage is that most business-oriented DBMSdo not permit "E"
formats (scientific notation). Since many structural terms involve very large
or very small numbers, the "E" format is essential. One final disadvantage is
the lack of support for matrix or vector input to the data base. Although
this capability is not required to store finit element model data, it would
be particularly useful when storing and querying intermediate or final results
from the application programs.
These are the major advantages and disadvantages revealed during the course
of the research. The user will have to make trade-offs in determining the most
optimal way to use a DBMSwith finite element models and computer programs.
PLANSFORDBMSWORKWITH FINITE ELEMENTMODELS
New data base management systems (DBMS) are now being designed and de-
veloped for engineering and scientific applications. For this reason, as well
as the previously discussed disadvantages, no future research is planned
using a commercial business-oriented DBMSwith a finite element model. Future
research is planned using E/S DMS,a scientific and engineering oriented DBMS
being developed under a NASAgrant at the University of Texas. E/S DMSis
scheduled to be delivered to NASALangley in August 1979. It executes on
CDCCYBERcomputers with a NOSoperating system. It has been proposed to imple-
ment E/S DMSon a minicomputer allowing users to distribute the data base as
well as the processing between a mainframe and a minicomputer. This arrange-
ment would give the user a very powerful tool; because the design and modeling
could then be done on the faster (line speed) interactive graphics terminal,
while the "number crunching" applications programs such as NASTRANand SPAR
could be executed on the more powerful mainframe. Future research is planned
along these lines.
CONCLUDINGREMARKS
A structural engineering, finite element model can be represented as a
hierarchial structure within a business-oriented data base management system
(DBMS). Use of the DBMSand conversion pre-processor computer programs, allow
the data to be stored independent of application programs that use the data
as input. This arrangement has the advantage that only one copy of the data
needs to be stored and maintained even though more than one application program
can use the data as input. The DBMSmay also allow the user to query the data
base as an aid in his modeling. The data manipulation language of the DBMS
gives the application programmer the power and flexibility of FORTRANcombined
226
with the data storage capabilities of the data base. A small example problem
demonstrates the use of a data base with one specific finite element model.
Output of the conversion programs is shown in the form of input decks to
both the NASTRANand SPAR structural analysis application programs. Advantages
and disadvantages are described to show that while although a DBMScreated for
business-oriented data can be useful for handling a finite element engineering
model, it does not have all the capabilities required for engineering and
scientific computing.
22'7
STRUCTURE
SUBSTRUCTURE
WING TAIL FUSELAGE
ELEMENTS
NODES
• X,Y,Z
Figure l.- Hierarchial structure of a finite element model.
STEPI-CREATETHEDATABASE [ DATABASENAME ]
! J
STEP2 - LOADTHEDATABASEDEFINITION DATABASENAME
STEP3-LOADTHEDATABASEINPUT DATABASENAME
Figure 2.- Steps for loading a data base.
228
1. MODEL (NAME X(21))!
2* SUBSTRUCTURES(RG}I
3* SUBSTRUCTURE NAME (NAME X(lO) IN 2);
#* SUBSTRUCTURE ELEMENTS(RG IN 2);
5* ELEMENT ID (INTEGER NUMBER 9(/) IN 4)I
6* ELEMENT NAME (NON-KEY NAME X(r} IN _);
7* XI VECTOR COMPONENT (NON-KEY DECIMAL NUMBER IN _);
8* X2 VECTOR COMPONENT (NON-KEY DECIMAL NUMBER IN _);
9* X3 VECTOR COMPONENT (NON-KEY DECIMAL NUMBER IN 4)!
10- ELEMENT PROPERTY ID (INTEGER NUMBER 9(7) IN 4};
11" ELEMENT GRID POINTS (RG IN 4);
12- GRID POINT ID (INTEGER NUMBER 9(7} IN 11);
13. X COORDINATE (NON-KEY DECIMAL NUMBER IN 11};
14- Y COORDINATE (NON-KEY DEClMAL NUMBER IN 11);
15- Z COORDINATE (NON-KEY DECIMAL NUMBER IN 11);
16" PERMANENT SPC (NON-KEY INTEGER NUMBER 9(7) IN 11);
20* ELEMENT PROPERTIES (RG IN 2);
21" PROPERTY ID (INTEGER NUMBER _(7) IN gO);
22* MATERIAL ID (NON-KEY INTEGER NUMBER 9(7) IN 20);
23* AREA (NON-KEY NAME X(/) IN 20);
2_* MOMENTS OF INERTIA (NON-KEY NAME X(7) IN _0);
25* YOUNGS MODULUS (NON-KEY NAME X(/) IN 20);
26* SHEAR MODULUS (NON-KEY DECIMAL NUMBER IN _0);
2(* POISSONS RATIO (NON-KEY DECIMAL NUMBER IN £0);
2d* MASS DENSITY (NON-KEY DECIMAL NUMBER IN _O)i
29* PROPERTY NAME (NON-KEY NAME X(1) IN _0);
35* SINGLE POINT CONSTRAINTS(RG IN 2);
36* SPC SET ID (NON-KEY INTEGER NUMBER 9(1) IN 35);
37* SPC GRID ID (NON-KEY INTEGER NUMBER 9(7} IN 3b};
38- SPC COMPONENT NUMBER (NON-KEY INTEGER NUMBER 9(/} IN 3b};
39* OMITTED COORDINATES(RG IN 2};
#0. OMIT GRID ID (NON-KEY INTEGER NUMBER 9(7) IN 39);
#J* OMIT COMPONENT NUMBER (NON-KEY INTEGER NUMBER V(7) IN 39)I
4_* EIGENVALUE INFORMATION(RG IN 2);
_3- EIGENVALUE SET ID (NON-KEY INTEGER NUMBER 9(7) IN #_);
#4* METHOD (NON-KEY NAME X(7) IN 42);
$5. LO FREQ (NON-KEY DECIMAL NUMBER IN 42);
#6- HI FREQ (NON-KEY DECIMAL NUMBER IN 42);
#7* ESTIMATE OF ROOTS (NON-KEY INTEGER NUMdER V(7) IN _2);
#8- DESIRED ROOTS (NON-KEY INTEGER NUMBER 9(() IN 4_);
_9- NORMALIZING METHOD (NON-KEY NAME X(7) IN 4_);
Figure 3.- Data base definition for a finite element model,
229
DATABASE OF A
FIHITE ELEMENTRODEL
CONVERSION CONVERSION
PROGRAM $1 PROGRAM $2
I H'ASTRRHOUTPUTi ISPAR OUTPUT
Figure 4.- Flowchart of finite element data ba§e process.
230
I.DATA _ASE TEST*
_*3*CANT _LAM _
II*I_*I* 13"0.0" Ib_1345"
|I'12"2"
4o5-12" b*CBAR* 7*0.0 8"I." 900.* I00_01 _
11"12o2" 13"0.I ° 1001345*
II*I_'3"
4"5"13" 6*CBA_* l*O. * _01.* 9_0.* I00_01 *
II*I_'3" 1300.2- 16-134b*
11.12o4"
4,5-14o O*CBARO 7*0.0 B*I.* 9-0.* I0"_01"
_1o12o4- |_*0._ _ _bOI_45 *
|I*12._o
4.b0150 b*CSAR* 7*0.0 _*I.* 900.* 10"_01"
II*120b* 13-0.4" Ib*13_50
II*12o6.
4.50160 b*CBA_* 7*0. ° _*i.* 900.* I0"_01"
II*IZo_0 13"0.5" 16013_5.
I1012"7.
4"5"1/* b*C_ARo 700.0 _*I.* 900.* 10"_01"
I1012.10 13*O.bo 16-134b*
llol2*_*
4,5018- b*CBA_O ?*0.* 8°I.* 9-0.* I0"_01"
11.12"8" 13"0.7" 16_13_5"
1101209*
_05_190 O*CBARO 7*0.0 S*l.o 9*0.0 I0"_01"
11"12"9" 13*U.B_ Ib*13_bo
ll*l_olO*
4*5*20* b*CBAR* 1"0. ° B01.0 900. ° I0 °_01°
11.12"10" 13"0.9" Ib*13_b*
I1012_Ii *
405021- b*CBAR* 7°0.° _*I.* 9o0.* 10"_01"
II*I_*II* 13"1.0 ° 16.1345"
11012-12.
4"5"_Z* b*CBAR _ 7"0.* _*I.* 9-0.* I0"_01"
II*12"I_* 13-1.1o 16.1345"
llol_*lJ* IJ*l.2* 1601345*
20"21"£01"
230b.0-4"
_4.b.0-90
25.7.0+i00
_7-.30
_8,B6-
290PBAR o
3503b*Z00
37"I*
38_b*
39040013* 41"0"
39040-2. _l*b *
39*40*3* 41*b*
39.40_4, 410b *
3904000, 41060
39*40*60 41"0"
390400/_ 41o6o
39*40*80 41-6o
39040*9* _l*bo
39o40"10" 41"0-
39"40011" 41"6"
39-40-I_* _l*b*
_401NV*
45*0.0*
_b*500.*
47"3_
48*30
END**
Figure 5.- Data base input for a cantilever beam,
231
Y
2 3 4 5 6 7 8 9 10 11 12 13
1 , ,
-- 12m --
Figure 6.- Cantilever beam finite element model.
/
///
/
/
/
/
/
232
TO DATAE_ASEoTEST
APP DISP
50L 3,0
TIME
CENO
TITLE = TEST PQOBLEM FOR DATA 8ASE(NASTRAN CONVERSION}
SUBTITLE = VIBRATION ANALYSIS OF A CANTILEVER BEAM
LINE = 40
ECHO = BOTH
METHO0 = 12
SPC = 20
OUTPUT
DISP = ALL
BEGIN BULK
CBAR |l 201 I 2 0,0 I,O 0,0 I
CBAR 12 201 2 3 0,0 1,0 0,0 I
CBAR 13 201 3 4 0,0 1,0 0.0 I
CBAR 14 201 4 5 0.0 1.0 0.0 I
CBAR 15 201 5 6 0.0 1.0 0.0 I
CBAR 16 201 b 7 0.0 1,0 0,0 I
CBAR 17 201 7 _ 0.0 1.0 0.0 I
CBAR 18 201 8 9 0.0 1.0 0.0 I
CBAR i9 20I 9 I0 0.0 I®0 0.0 I
CBAR 20 201 I0 II 0,0 1,0 0.0 I
CBAR 21 201 II 12 0,0 1,0 0,0 I
CBAR 22 201 12 13 0.0 ).0 0,0 1
GRID 1 0,00 1345
GRID 2 .lO i345
GRID 3 .20 1345
GRID 4 ,30 1345
GRID 5 .40 1345
GRID 6 ,50 1345
GRID ? ,50 1345
GRID _ ,70 1345
GRID 9 .80 1345
GRID I0 .90 134_
GRID II 1,00 1345
GRID 12 I.I0 1345
GRID 13 1.20 1345
PBAR 201 6 6,0-4 5,0-9
MATI 6 7,0*10 0.3 .B6
OMIT 13 6
OMIT 2 6
OMIT 3 o
OMIT 4 6
OMIT 5 6
OMIT o 6
OMIT 7 6
OMIT u 6
OMIT 9 6
OMIT 10 6
OMIT II 6
OMIT 12 6
SPC 20 I 26
EIGR I21NV 0,0 bO0,O 3 3 *BC
*BC MAX
PARAM COUPMASS I
CNGRNT II 12THRU 2_
ENDDATA
Figure 7.- NASTRAN input deck output from pre_processor program NTRNS2K.
233
_XOT TAB
START 13,2 6
TITLE "VIBRATION ANALYSIS OF A CANTILEVER BEAM
TEXT
" TEST PROBLEM FOR DATA BASE(SPAR CONVERSION)
MATERIAL CONSTANT
I 7,0+I0 ,30 ,86
JOINT LOCATIONS
1 0.0
# ,3
5 .#
6 .5
7 .6
8 o'T
9 .8
I0 ,9
11 1.0
12 l°l
13 1.2
CONSTRAINT CASE l
ZERO I 3 # 5
,[XOT ELD
E_3
NSECT=I
1 2
3
3
5
5 6
b 7
7 8
8 9
9 I0
I0 II
II 12
12 13
[XOT EXIT
Figure 8.- SPAR input deck output from pre-processor program SPARS2K.
234


Application of a data base management system to a finite element model

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server