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Case 3 : Buckling Analysis of Front Side Member
ABSTRACT: The buckling analysis of the front side panel is performed to verify aspects of
deformation during a frontal crash. The analysis model is generated from the early design data
(typcially the shapes of the cross section) when there is no detailed design information about the fro
panel of the vehicle. The buckling analysis is also done during the early stages of design, in a period
the structural changes are possible. The front side panel is to be connected to the fender inner pa
dash panel, and the lower dash member of the car body. Since the role of the fender inner panel d
frontal impact is insignificant, the analysis is done by constraining only the locations connected to the
panel and lower dash member. The load is applied at the connections to the fender. The results fr
analysis are used to decide whether reinforment should be added.
Solution Type : Sol 105 Buckling Analysis
< Model Geometry >
206
or each
n
g.
The fir st step : Modeling
File | New... New Data Base Name : case3
There are five neutral files prepared for each component. Before reading these files, create group f
component.
Group | Create New Group to Name : inner
-Apply- Elements to be created from now on will be included i
the current group, inner.
Read a model to be meshed. File | Import...
Find the directory including neutral files and select ‘inner’ file.
Neutral Options...
Select entities required in the first imported file.
Select nodes and elements only.
Ok
- Apply-
Click OK about a message being displayed when importin
207
Display | Finite Elements...
Shrink factor : 0.07
Group | Create... New Group Name : inner_ref
Make Current
Unpost All Other Groups
-Apply-
File | Import... inner_ref.out Click
-Apply-
It is not necessary to define Neutral Option again.
Group | Create... New Group Name : outer
Make Current
Unpost All Other Groups
-Apply-
208
File | Import... out_pan.out.1 Click
-Apply-
Group | Create... New Group Name : extend
Make Current
Unpost All Other Groups
-Apply-
File | Import... add_outer.out.1 Click
-Apply-
Connect each component by RBE2.
209
e
.
Connect the inner panel and the inner reinforcement.
Group | Post... inner
inner_ref
Post onlt two groups.
Define a current Group to the inner group.
Set nodes in the inner group to be
independent nodes, and creat
RBE2 (nodes inside circles).
Finite Elements
Determine the dependent node and the independent node
210
e
y
s
Auto Switch is on.
Select one dependent node to on
independent node, and create RBE2.
If clicking nodes of the inner_ref
component, then it becomes an
independent node.
Fix all DOF via dragging mouse.
Select independent nodes b
referring to the previous picture,
and click apply under Define
Terms....
Select nodes from left to right.
Define nodes in the inner group a
independent nodes.
Node Label (depen. Indepen.)
(8 259) (9 260) (10 261)
(11 262) (12 263)
Create five RBE2 according to
node label.
211
(175 337) (176 338) (180 293)
(179 326) (186 294) (225 295)
(230 329 ) (223 303) (47 324)
(101 449) (99 448) (33 400)
212
(34 401) (35 402) (36 403)
(195 346) (193 349) (192 374)
(133 381) (132 387)
(127 390) (119 395)
213
s
Connect the inner component and the outer component.
Group | Post... Post the inner and the outer only.
The current group is the inner group.
Create | MPC | RBE2 Define Terms...
Connect the flange line between components.
Connect nodes of theflange line
crossly.
Define nodes in the inner group a
independent nodes by referring to
the location of circles.
(726 265) (718 266) (724 267)
(716 268) (722 275) (714 325)
214
.
215
(888 705) ( 890 450) (874 501)
Keep connecting the flange line
(876 497) (873 399)
(1118 502) (508 848)
(509 940) (942 484)
(513 943) (946 578) (947 930)
Connect the lower-end flange
line.
216
o
s
Create | MPC | RBE2
MPC ID
From 46
Define Terms
Keep defining nodes in the inner
group as independent nodes.
(759 363) (756 361) (762 365)
(755 352)
MPC 21 to MPC 24 are created by
the edit adding dependent nodes t
MPC created already.
Modify | MPC
MPC ID
Click the list box and select MPC
21.
Click Modify Terms....
Turn on Modify.
Click column 195 listed up in
Dependent Terms.
Change Select Menu to + and
select Node 809, and then 809 i
listed behind 195.
Do apply twice, and then it is modified.
Again click MPC ID box, and then select MPC 22 on the graphic screen.
Click Modify Terms.... Add nodes listed below to each MPC.
MPC 22 ( Dependent Node : 812 )
MPC 23 (Dependent Node : 814 )
MPC 24 (Dependent Node : 824 )
MPC22
MPC21
MPC23
MPC24
217
e
e
g-
o-
Because RBE2 inside the four large
circle has the same location as th
location where they are connected
with the inner_ref component, use
Modify adapted previously without
creating new one.
MPC 25 (Dependent Node : 820 )
MPC 26 (Dependent Node : 818 )
MPC 27 (Dependent Node : 822 )
Modify | MPC MPC ID Select RBE2 to be modified.
Modify Terms...
Modify
After clicking Dependent Node box, add nodes of th
outer component in Node List Box.
This is to define dependent node as two without chan
ing independent nodes (nodes of the inner comp
nent).
-Apply-
Connect the inner component and the extend component.
MPC25
MPC26
MPC27
218
d
.
Group | Post... Post the inner and the extend groups only.
A current group is the inner.
Create | MPC | RBE2
Define Terms...
Define nodes in the inner compo-
nent as independent nodes an
create RBE2.
(Circles in the picture)
(1081 474) (1078 529)
(1083 559) (1080 531)
Only dependent nodes are posted
(1024 524) (1021 520)
(1026 526) (1023 522)
(1019 528) (1012 535)
219
s). But,
BE2
d
Connect the outer and the extend.
Group | Post... Post the inner, outer, and extend groups.
A current group is the extend.
Create RBE2, selecting dependent and independent node one to one (based on the location of circle
use Modify like the previous way at the junction of three groups, inner, outer, and extend, where R
points are duplicated (modify only the RBE2 of point 1).
For this portion, create RBE2 in
zigzags, and connect the outer an
the extend.
1
220
Create | MPC | RBE2
Define Terms..
(1086 866) MPC52 (add 1082)
(1089 868) (1095 832)
(1091 923) (1094 924)
(1060 902) (1062 908)
(1064 904) (1066 910)
Post only the outer and extend
groups to select nodes easily.
Group | Post...
Post the outer and the extend group.
A current group is the extend group.
(1139 1371) (1138 1369)
(1140 1365) (1132 1131,1363)
Two dependent nodes are used.
(1130 1359) (1129 1357)
(1128 1355)
(1130 1359) (1129 1357)
(1128 1355)
221
(1126 1353) (1127 1337)
(1145 1331) (1098 1271)
(1143 1340) (1097 1255)
( 1142 1346) (1137 1350)
(1136 1377) (1134 1375)
(1133 1373)
222
s nec-
s
).
If the connection between components is done without omitting, then edit the properties and thicknes
essary for analyzing.
First of all, create the material table to apply thickness.
Materials
Define the name of a material.
Click and edit Youngs Modulus (20700) and Poisson
Ratio (0.3).
-Apply-
Edit the thickness of each component. Post only the group whose thickness is 1.2 (inner and inner_ref
Group | Post... Select the inner and the inner_ref.
A current group is the inner.
Properties
Create | 2D | Shell Property Set Name : thick_1.2
Input Properties..
Material Name : steel
Thickness : 1.2
Ok
Select Members
223
-
n
After changing Select Menu to 2D
Shell, select elements on the
screen.
If element list is registered in
Application Region, then do
apply.
Post only the group whose thickness is 1.4 (outer, extend). A current group is the outer.
Create | 2D | Shell Property Set Name : thick_1.4
Input Properties..
Material Name : steel
Thickness : 1.4
Ok
Select Members
After changing Select Menu to 2D Shell, select ele
ments on the screen.
If element list is registered in Application Region, the
do apply.
224
Create boundary conditions.
Loads / BCs
Define from elements of the inner group. Post the inner group only.
Create | Displacement | Nodal New Set Names : all_fixed
Input Data...
Translations < T1 T2 T3 >
< 0 0 0 >
Rotations < R1 R2 R3 >
< 0 0 0 >
Ok
Select Application Regions
FEM
Select Nodes
Select all nodes on the end of the frame model.
Add
Ok
-Apply-
Post the outer and extend groups only and define the outer as a current group.
225
t
, define
.
Modify | Displacement | Nodal
Select all_fixed.
Click Modify Application
Region….
Set Select Menu to =, and selec
the end nodes only.
Add
-Apply-
Edit the loads.
Create a center point at the very front cross-section and define that as the independent node. And then
nodes around the cross-section as dependent nodes and connect the very front nodes by RBE2.
Group | Post... Post the inner and the outer only.
A current group is the outer.
Creating a Center Point
Geometry
Create | Point | Interpolate Option : Point
Number of Point : 1
Uniform
Auto Execute
Point 1 Coordinates List
Node 252
Point 1 Coordinates List
Node 758
Newly created point 1.
Make turn point into node.
Finite Elements
Create | Node | XYZ
Select Point 1 and make node.
And then, node 1378 is generated
226
Finite Elements
Create | MPC | RBE2
Define Terms...
Dependent Node
Node 773 733:758:5 428 429
344:341:-1 282 276 437
438 252:264:6 720
Independent Node
Node 1378
Create RBE2.
Apply load to this center node.
227
◆Loads / BCs
Create | Force | Nodal New Set Name : Force
Input Data.... ==> Click.
Force < F1 F2 F3 > : < 100.,0.,0. >
Analysis Coordinate Frame : Coord 0
OK
Select Application Region.... ==> Click
Geometry Filter
◆ FEM
Application Region
Select Nodes :
Add | OK | Apply
Verify whether load is applied correctly.
Node 1378
228
e
The second step : Solution
1. Creating the MSC/NASTRAN input file
◆Analysis | Analyze | Entire Model | Analysis Deck
Jobname : case 3
Solution Type ===> Click
Solution Type :◆ BUCKLING
OK
Apply ===> Input file named case3.bdf is created in th
current directory.
Verify the input file using editor.
> vi case3.bdf
< The summary of the contents of case3.bdf file >
SOL 105
CEND
ECHO = NONE
SUBCASE 1
SPC = 2
LOAD = 2
DISPLACEMENT(SORT1,REAL)=ALL
SUBCASE 2
SPC = 2
METHOD = 1
VECTOR(SORT1,REAL)=ALL
BEGIN BULK
229
PARAM POST -1
EIGRL 1 1
$ Direct Text Input for Bulk Data
$ Elements and Element Properties for region : thick_1.2
PSHELL 2 1 1.2 1 1
CQUAD4 1 2 1 2 8 7
CQUAD4 2 2 2 3 9 8
CQUAD4 3 2 3 4 10 9
CQUAD4 4 2 4 5 11 10
CQUAD4 5 2 5 6 12 11
CQUAD4 6 2 7 8 14 13
CQUAD4 7 2 8 9 15 14
CQUAD4 8 2 9 10 16 15
CQUAD4 9 2 10 11 17 16
CQUAD4 10 2 11 12 18 17
.
.
.
CQUAD4 967 4 953 1143 1144 1098
CQUAD4 968 4 1098 1144 1145 951
CQUAD4 969 4 949 1127 1145 951
CQUAD4 970 4 954 1142 1137 956
CQUAD4 971 4 961 1128 1126 959
CQUAD4 972 4 976 1135 1139 970
MAT1 1 20700. .3 7.95E-10
$ Multipoint Constraints of the Entire Model
RBE2 1100 259 123456 8
RBE2 1101 260 123456 9
RBE2 1102 261 123456 10
.
.
.
RBE2 1183 1346 123456 1142
RBE2 1184 1350 123456 1137
RBE2 1185 1377 123456 1136
RBE2 1186 1375 123456 1134
RBE2 1187 1373 123456 1133
RBE2 1188 1378 123456 252 258 264 276 282 + A
230
+ A 341 342 343 344 428 429 437 438 + B
+ B 720 733 738 743 748 753 758 773
$ Nodes of the Entire Model
GRID 1 -535. 441.399 309.
GRID 2 -500. 441.399 309.
GRID 3 -465. 441.399 309.
GRID 4 -430. 441.399 309.
GRID 5 -395. 441.399 309.
GRID 6 -360. 441.399 309.
GRID 7 -535. 468.200 310.737
GRID 8 -500. 468.200 310.737
GRID 9 -465. 468.200 310.737
GRID 10 -430. 468.200 310.737
.
.
.
.
GRID 1371 87.0110 451.5 146.
GRID 1373 86.9819 435.776 124.091
GRID 1375 87.0017 412.969 92.3450
GRID 1377 90.7357 394.344 66.8584
GRID 1378 -540.900 470.700 219.649
$ Loads for Load Case : Default
SPCADD 2 1
LOAD 2 1. 1. 1
$ Displacement Constraints of Load Set : all_fixed
SPC1 1 123456 562 563 564 565 566 567 + C
+ C 579 584 592
SPC1 1 123456 608 THRU 630
SPC1 1 123456 898 899 900 901 917 918 + D
+ D 919 920 935 937 1039 1040 1041 1043 + E
+ E 1048 1049 1050 1051 1054 1055 1056 1059 + F
+ F 1071 1072
$ Nodal Forces of Load Set : force
FORCE 1 1378 0 100. 1. 0. 0.
ENDDATA
231
After checking the input file, execute MSC/NASTRAN.
❑ nast69 case3.bdf
If running the job is done, then check the result files.
First of all, check whether there are fatal errors and verify whether the value of epsilon is less than 10-6.
>vi case3.f06
< The summary of the contents of case3.f06 file >
..
0 N A S T R A N E X E C U T I V E C O N T R O L D E C K E C H O
SOL 105
CEND
0
0 C A S E C O N T R O L D E C K E C H O
CARD
COUNT
1 ECHO = NONE
2 SUBCASE 1
3 SPC = 2
4 LOAD = 2
5 DISPLACEMENT(SORT1,REAL)=ALL
6 SUBCASE 2
7 SPC = 2
8 METHOD = 1
9 VECTOR(SORT1,REAL)=ALL
10 BEGIN BULK
INPUT BULK DATA CARD COUNT = 2379
TOTAL COUNT= 2272
OLOAD RESULTANT
T1 T2 T3 R1 R2 R3
0 1 1.0000000E+02 0.0000000E+00 0.0000000E+00 0.0000000E+00 2.1964900E+04 -4.7070000E+04
...
0*** USER INFORMATION MESSAGE 5293 FOR DATA BLOCK KLL
232
S
LOAD SEQ. NO. EPSILON EXTERNAL WORK EPSILONS LARGER THAN .001 ARE FLAGGED WITH ASTERISK1 2.9074562E-13 2.3728092E+00
SUBCASE 1
.
.
.
D I S P L A C E M E N T V E C T O R
POINT ID. TYPE T1 T2 T3 R1 R2 R3
1 G 3.235775E-03 2.235421E-01 -1.816825E-01 -1.152107E-04 -3.644177E-04 -4.386741E-04
2 G 3.238796E-03 2.080157E-01 -1.695592E-01 -7.757525E-05 -3.215211E-04 -4.496954E-04
3 G 3.253969E-03 1.924683E-01 -1.574537E-01 -1.138076E-04 -3.673213E-04 -4.401017E-04
4 G 3.303498E-03 1.769516E-01 -1.454092E-01 -1.001949E-04 -3.195727E-04 -4.485227E-04
5 G 3.378572E-03 1.615387E-01 -1.334580E-01 -1.118659E-04 -3.769469E-04 -4.343758E-04
6 G 3.470389E-03 1.463215E-01 -1.216843E-01 -1.666119E-04 -2.771154E-04 -4.302906E-04
7 G 1.452225E-02 2.237154E-01 -1.843373E-01 -8.291727E-05 -3.877734E-04 .0
8 G 1.451239E-02 2.081915E-01 -1.721896E-01 -1.170768E-04 -3.346481E-04 -3.579081E-04
.
.
.
TABLE OF SHIFTS: (REIGL)
SHIFT # SHIFT VALUE FREQUENCY, CYCLES # EIGENVALUES BELOW # NEW EIGENVALUES FOUND
1. -2.3553771E-01 -7.7241436E-02 0 0
2. 5.8078220E+01 1.2129049E+00 1 1
3. -1.9761407E+02 -2.2373250E+00 2 2
SUBCASE 2
E I G E N V A L U E A N A L Y S I S S U M M A R Y (REIGL MODULE)
BLOCK SIZE USED ...................... 2
NUMBER OF DECOMPOSITIONS ............. 3
NUMBER OF ROOTS FOUND ................ 1
233
NUMBER OF SOLVES REQUIRED ............ 28
SUBCASE 2
R E A L E I G E N V A L U E S
MODE EXTRACTION EIGENVALUE RADIANS CYCLES GENERALIZED GENERALIZED
NO. ORDER MASS STIFFNESS
1 1 5.190937E+01 7.204816E+00 1.146682E+00 7.798079E-01 4.047934E+01
.
.
SUBCASE 2
EIGENVALUE = 5.363318E+01
R E A L E I G E N V E C T O R N O . 1
POINT ID. TYPE T1 T2 T3 R1 R2 R3
1 G -8.566538E-03 1.921882E-01 1.249841E-02 -1.855682E-05 2.163814E-05 -3.388280E-04
2 G -8.567329E-03 1.802863E-01 1.191208E-02 -2.687820E-05 9.734243E-06 -3.393966E-04
3 G -8.571602E-03 1.683882E-01 1.132989E-02 -1.592053E-05 2.422794E-05 -3.410026E-04
4 G -8.584733E-03 1.564814E-01 1.076477E-02 -2.291050E-05 4.678557E-06 -3.389617E-04
5 G -8.606226E-03 1.445532E-01 1.022823E-02 -1.672048E-05 3.139912E-05 -3.420617E-04
6 G -8.642131E-03 1.325594E-01 9.759452E-03 -6.581736E-06 -1.307769E-05 -3.458741E-04
7 G 5.766959E-04 1.922327E-01 1.181289E-02 -3.036291E-05 -2.821347E-07 .0
8 G 5.784986E-04 1.803324E-01 1.118401E-02 -2.522108E-05 2.027580E-05 -4.640249E-04
9 G 5.763102E-04 1.684324E-01 1.066793E-02 -3.241406E-05 2.485410E-05 -4.643961E-04
10 G 5.741392E-04 1.565349E-01 9.993046E-03 -3.336949E-05 2.754011E-05 -4.567042E-04
*** USER INFORMATION MESSAGE 4110 (OUTPX2)END-OF-DATA SIMULATION ON FORTRAN UNIT 12
(MAXIMUM SIZE OF FORTRAN RECORDS WRITTEN = 1 WORDS.)
(NUMBER OF FORTRAN RECORDS WRITTEN = 1 RECORDS.)
(TOTAL DATA WRITTEN FOR EOF MARKER = 1 WORDS.)
SUBCASE 2
* * * * D B D I C T P R I N T * * * * SUBDMAP = PRTSUM , DMAP STATEMENT NO. 13
234
N
* * * * A N A L Y S I S S U M M A R Y T A B L E * * * *
SEID PEID PROJ VERS APRCH SEMG SEMR SEKR SELG SELR MODES DYNRED SOLLIN PVALID SOLNL LOOPID DESIG
CYCLE SENSITIVITY
--------------------------------------------------------------------------------------------------------------------------
0 0 1 1 ' ' T T T T T T F T 0 F -1 0 F
SEID = SUPERELEMENT ID.
PEID = PRIMARY SUPERELEMENT ID OF IMAGE SUPERELEMENT.
PROJ = PROJECT ID NUMBER.
VERS = VERSION ID.
APRCH = BLANK FOR STRUCTURAL ANALYSIS. HEAT FOR HEAT TRANSFER ANALYSIS.
SEMG = STIFFNESS AND MASS MATRIX GENERATION STEP.
SEMR = MASS MATRIX REDUCTION STEP (INCLUDES EIGENVALUE SOLUTION FOR MODES).
SEKR = STIFFNESS MATRIX REDUCTION STEP.
SELG = LOAD MATRIX GENERATION STEP.
SELR = LOAD MATRIX REDUCTION STEP.
MODES = T (TRUE) IF NORMAL MODES OR BUCKLING MODES CALCULATED.
DYNRED = T (TRUE) MEANS GENERALIZED DYNAMIC AND/OR COMPONENT MODE REDUCTION PERFORMED.
SOLLIN = T (TRUE) IF LINEAR SOLUTION EXISTS IN DATABASE.
PVALID = P-DISTRIBUTION ID OF P-VALUE FOR P-ELEMENTS
LOOPID = THE LAST LOOPID VALUE USED IN THE NONLINEAR ANALYSIS. USEFUL FOR RESTARTS.
SOLNL = T (TRUE) IF NONLINEAR SOLUTION EXISTS IN DATABASE.
DESIGN CYCLE = THE LAST DESIGN CYCLE (ONLY VALID IN OPTIMIZATION).
SENSITIVITY = SENSITIVITY MATRIX GENERATION FLAG.
1 * * * END OF JOB * * *
******************************************************************************************************************
The load used in the static analysis is 100.0 N, and the first eigenvalue in case3.f06 file is 5.190937E+01.
Therefore, the buckling load is;
Pcr = λ * P(external forces)
= 5.190937E+01 * 100. = 5190.937 N
235
ase 1.
n
The third step : Post-processing
If the verification of the text results is done, then read case3.op2 in PATRAN
υAnalysis
Read Output2 | Resulties | Translate Select Result File... ===> Click
Select Result File : case3.op2 ===> Click
OK
Apply
Display the deformed shapes.
υResults | Basic
For the buckling analysis, the results are divided into two based on two Subcase.
The result of Subcase 1 is equal to the result of the static structural analysis, and
the result of Subcase 2 represents the result of the normal mode analysis performed based on Subc
Display the deformed shapes of the static results first.
Select Result Cases
1.1- Default,Static Subcase
Select Fringe Result
1.1-Displacement,Translational
Result Quantity : Magnitude
Select Deformation Result
1. 1_Displacement,Translational
Apply
Before processing, include elements only into a current group.
Group | Create
New Group Name : all_fem
Selection Entity : Add All FEM
-Apply-
Exclude MPC.
Group | Modify
Target Group to Modify : all_fem
Select MPC 1:89 to Member List.
If they are listed up in Member List to Add/Remove box, the
click Remove.
Original Model is the following.
236
The deformed shape of the static result
Display the buckling modes of the buckling analysis results.
237
Select Result Cases
1. 2-Load Case 2,Mode 1
Select Fringe Result
2.1-Eigenvectors, Translational
Result Quantity : Magnitude
Select Deformation Result
2.1-Eigenvectors, Translational
Apply
238
239