Transcript Integration of External Design Criteria with MSC.Nastran

Integration of External Design Criteria with
MSC.Nastran Structural Analysis and Optimization*
D.K. Barker and J.C. Johnson
Lockheed Martin Aeronautics Company, Fort Worth, Texas
E.H. Johnson and D.P. Layfield
MSC.Software Corporation, Santa Ana, California
MSC 3rd Worldwide Aerospace Users Conference and
Technology Showcase, April 8-10, 2002
Paper No. 2001-15
*Copyright  2001 Lockheed Martin Corporation. All rights reserved. Published
by the MSC.Software Corporation with permission.
Lockheed Martin Aeronautics Company
Motivation
Airframe Structural Certification & Drawing Release
 Rigorous Application of Detail Strength Criteria
 FEA Internal Loads Feed “In-House” Methods
 Dependent on Engineering Data Exchange
Internal
Loads
Database
Detail
Structural
Analyses
Structural
Sizing
Updated
External
Loads
“Man-in-the-Loop” is Opportunity for Automation
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MSC.Nastran Enhancements Enable Automation
Laminate Modeling Enhancements
 Membrane Dominant Structure
 Stacking Sequence Negligible
 PCOMP Extensions Minimize Input
 LAM=MEM, SMEAR or SMCORE
½ SMEAR’d laminate
Thickness Offset
½ SMEAR’d laminate
DATABASE
API
API
User Written
MSC.Nastran
Improved Integration Methods
Client Program
Executable
 Evaluated MSC.Nastran Toolkit
MSC-Supplied
MSC.Nastran
Enhancements
Partnership
 Datablock
Indexing Leveraged Through
Client Object Lib.
DMAP Library
• MSC
Extends
Core C.S.
Nastran Product
 Element
Results
in Material
• Lockheed Martin Improves Internal Integration
External
Server1
Criteria
External Responses for MSC.Nastran
 New DRESP3 Bulkdata Entry
Server2
API
MSC.Nastran
 External Criteria Servers
Server i
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i = 1..10
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Automation of Detailed Analysis & Sizing
LM Aero Approach Emphasizes Rapid Structural Increment
 Fully Stressed Design (FSD) – No Sensitivities
 Structural Strength & Practicality Criteria
 Seamless Integration of Standalone External Criteria
Elem. Set
Ref. Variables
FE
Result
DB
Parse Input File
Execute NASTRAN Solution
Evaluate Element Criteria
Enforce Practicality Criteria
Template File
Batch File
Generator
Input File
Update FE Bulkdata
Detail Analysis
Tool
Generate VIEW Results
Converged ?
yes
Title:
Subtitle:
Material:
Panel Width:
Panel Length:
Panel Thick:
Load Case 1:
Load Case 2:
…
Buckling Analysis
Conceptual Input
>>DBGET REFVAR…
>>DBGET REFVAR…
>>DBGET REFVAR…
>>DBGET PROP…
>>DBGET RESULT…
>>DBGET RESULT…
…
no
Output File
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Practicality Criteria
Strength Criteria Alone Not Sufficient
 Production Quality FEM
 Anticipate 50K Unique Properties
 Complex and Not Producible
Practicalization Options Implemented
 Minimum Gage, Property Linking,
Ply Percentage, Drop-off Rate, etc.
Innovative Property Drop-off Approach
 Reduce Model Complexity
 Redistribute Load Concentrations
Control of Property Drop-off Rate
Element Centroid
1
2
3
Plan View of 2-D Element Strip
Allowable
Drop-Off
Rate
Actual DropOff Rate
Allowable
Drop-Off
Rate
Actual DropOff Rate
Initial Thickness
Intermediate Thickness
Revised Thickness
Edge View of 2-D Element Strip
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FSD Demonstration Problem
Intermediate Complexity Wing (ICW)
 Composite Skins
 Metalic Understructure
Membrane Dominant Skins
 0, ±45, and 90-deg plies
 Uses PCOMP LAM=SMEAR
Skins – 64 elements (4 layers/element)
Caps – 110 elements
Webs – 55 elements
357 Independent Design Variables
Design Criteria
Applied Static Load Conditions
Condition
FZ
(103 lb)
MX*
(106 in-lb)
MY*
(106 in-lb)
1
43.316
2.231
-1.027
2
42.533
2.211
- .447
*Moments summed about wing root at mid-chord.
Part
Strength Criteria
Practicality Criteria
Skins
fiber strain
2200me tension
2000me comp.
panel stability
min. layer = 0.025 in.
min. ply % > 8%
max. ply % < 60%
drop-off rate < 0.02*
Caps
axial stress
27 ksi tension
28 ksi compression
min. gage = 0.05 in.
drop-off rate < 0.015*
Webs
max shear stress
24 ksi
min. gage = 0.025 in.
drop-off rate < 0.02*
*Drop-off rate defined by equation 17 (see paper).
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FSD Convergence Characteristics
 Relaxation Factor Improves Distributed Convergence
Tenforced = (Trequired / Tinit)a Tinit where “a” is user specified.
 Objective Converges Quickly
 FSD Enables Rapid Prediction of Target Weight
 Critical Criteria Converges More Slowly
 Negative Margins Present After Ten Iterations
Objective Convergence
Critical Criteria Convergence
190
a=0.50
a=0.75
a=1.00
170
160
Min Margin of Safety
Total Weight (lb)
180
150
140
130
0
-0.05
-0.1
-0.15
-0.2
-0.25
a=0.50
-0.3
a=0.75
a=1.00
-0.35
-0.4
-0.45
120
1
2
3
4
5
6
7
Iteration Number
8
9
10
1
2
3
4
5
6
7
8
9
10
Iteration Number
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“Load Chasing” Effect
 Negative Margins Driven By Single Element
 Lower Aft-Spar Cap (Wing-Root Boundary)
 FSD Magnifies Inherent Stress Intensifiers
 Configuration: Aft Swept Wing Pushes Load Aft
 Modeling: Coarse Grid, Rigid Boundary
 Methodology: Increased Gage (i.e., Stiffness) Draws Load
 Sizing Increment Illustrates Gradual Stiffness Redistribution
Critical Criteria Convergence (a=0.5)
Min Margin of Safety
0
-0.1
-0.2
-0.3
All Elements
-0.4
Lower Aft Spar
Cap Excluded
-0.5
1
2
3
4
5
6
7
Iteration Number
8
9
10
Upper Skin Design
Increment at
a=0.5, Iter=8
Increment (in.)
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
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-0.0055
-0.0050
-0.0045
-0.0040
-0.0035
-0.0030
-0.0025
-0.0020
-0.0015
-0.0010
-0.0005
-0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
8
FSD Final Design
 Upper Skin Sized as Anticipated
 Thickness Decreases Radially From Aft Wing-Root
 Buckling Criteria Dominates
 Good Distributed Convergence
 Margins Range From 0.181 to -0.040
 Manual Intervention Required to
Restrict “Load Chasing”
Upper Skin for
a=0.5, Iter=8
Thickness (in.)
A
0.100
B
0.125
C
0.150
D
0.175
E
0.200
F
0.225
G
0.250
H
0.275
I
0.300
J
0.325
K
0.350
L
0.375
M
0.400
N
0.425
O
0.450
Critical Criteria & Margins
Legend
1 - Min. Gage
2 - TM1 Buckling
3 - TM1 Strain
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Integration with MSC.Nastran Optimization
Synthetic Fiber Strain Constraints
 Smeared PCOMP Requires
Synthetic Surface Strain Criteria
 DRESP2 Formulates Fiber Strain
 See Paper for Details
 Simplified Laminate Enables Ply
Percentage Criteria
 Demonstrated With DRESP2
 See Paper for Details
 External Response Server
 Implementation Underway
 Buckling Module Prototyped
$ design constraints for fiber strain.
Synthetic
Ply-2000.,
Percentage
Constraints
DCONSTR, 3, 201,
2200.
DCONSTR, 3, 202, -2000., 2200.
DCONSTR,
3, 203,definition
-2000., 2200.
$ design
variable
DCONSTR,
3, 204,
-2000.,
2200.
$ (0,
-45, +45,
90 deg
plies)
DESVAR, 1, T1, 0.05, 0.025
$ synthetic
DESVAR,
2, T2, fiber
0.05, strain
0.025 responses (Z2)
$ (0, 3,
-45,
and0.025
90 deg plies)
DESVAR,
T3,+45,
0.05,
DRESP2,
E1, 401
DESVAR,
4, 201,
T4, 0.05,
0.025
, DTABLE, A1
DVPREL1, ,1,DRESP1,
PCOMP, 301,
100, 302,
T1 303
DRESP2,
, 1,202,
1. E2, 401
DVPREL1, ,2,DTABLE,
PCOMP, A2
100, T2
301, 302, 303
, ,2,DRESP1,
1.
DRESP2,3,203,
E3, 100,
401 T3
DVPREL1,
PCOMP,
A3
, ,3,DTABLE,
1.
DVPREL1, ,4,DRESP1,
PCOMP, 301,
100, 302,
T4 303
DRESP2,
, 4,204,
1. E4, 401
, DTABLE, A4
DRESP1, 301,
$ design ,constraints
for302,
ply 303
% boundaries
DCONSTR, 2, 501, 8.0, 60.0
$ intrinsic
laminate
strain
DCONSTR,
2, 502,
8.0, 60.0
$ (Ex, 2,
Ey,503,
and 8.0,
Exy) 60.0
for top surface (Z2)
DCONSTR,
DRESP1,2,301,
DCONSTR,
504,EX,
8.0,STRAIN,
60.0 PCOMP, , 11, , 100
DRESP1, 302, EY, STRAIN, PCOMP, , 12, , 100
DRESP1, 303,
STRAIN,response
PCOMP, , 13, , 100
$ synthetic
ply EXY,
percentage
$ (0, -45, +45, 90 deg plies)
$ strain
DRESP2,
501,transformation
PRCNT1, 402 equation.
DEQATN
401
=External
, DVPREL1,
1,thetar(theta,ex,ey,exy)
2, 3, Server1
4, 1
theta * PI(1) / 180. ; Criteria
DRESP2, 502, PRCNT2, 402
= 4, 2
, DVPREL1,exfiber
1, 2, 3,
1.0e+6
DRESP2, 503, PRCNT3,
402 *
(ex*cos(thetar)**2
+
, DVPREL1, 1,
2, 3, 4, 3
ey*sin(thetar)**2
+
DRESP2, 504, PRCNT4,
402
Server2
MSC.Nastran
, DVPREL1, 1,exy*sin(thetar)*cos(thetar))
2, 3, 4,API
4
External Response Server
Integrated Detail
Analysis Tools
Production
Integration
$ table
of constant
parameters (ply angles).
$ ply
percentage
formulation.
DTABLE,
a2, -45., a3, 45., a4,
DEQATN
402a1, 0.,
total(t1,t2,t3,t4,ti)
= 90.
(t1 +t2 +t3 +t4);
plyprcnt =
i = 1..10
i
1.e2 * Server
(ti / total)
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MP Demonstration Problem
 FSD Demonstration Repeated Using MP Methodology
 Same Criteria Except Property Drop-off Not Applied
 Convergence Achieved After 5 Iterations
 Increase of 20 lbs Over FSD Solution
 All Criteria Are Satisfied
Objective Convergence
Critical Criteria Convergence
6.00
Max Constraint Value
Total Weight (lbs)
160.00
150.00
140.00
130.00
120.00
110.00
100.00
5.00
4.00
3.00
2.00
1.00
0.00
1
2
3
4
Iteration Number
5
6
1
2
3
4
5
6
Iteration Number
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MP Final Design
 Upper Skin Contour Similar to FSD
 Slightly Thicker than FSD
 Thickness Added Forward of Center Spar
 Distributed Convergence Characteristics
 Minimum Margin is -0.005
 Oversized Inboard Region Reduces
Load In Lower Aft-Spar Cap
Critical Criteria & Margins
Legend
Upper Skin
Final Iteration
1 - Min. Gage
2 - TM1 Buckling
3 - TM1 Strain
Thickness (in.)
A
0.200
B
0.225
C
0.250
D
0.275
E
0.300
F
0.325
G
0.350
H
0.375
I
0.400
J
0.425
K
0.450
L
0.475
M
0.500
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Comparison of FSD and MP Designs
Carry-Thru Bending Moment Distribution
90-deg
plies
MP
800
(1000 in-lbs)
0-deg
plies
Bending Moment, MX
FSD
700
600
FSD
MP
500
400
300
0-deg
plies
90-deg
plies
200
100
0
18
30
42
54
66
Fuselage Station (in.)
*Moments summed about wing root.
45-deg
plies
Ply Percentage
A
5.0
B
10.0
C
15.0
D
20.0
E
25.0
F
30.0
G
35.0
H
40.0
I
45.0
J
50.0
K
55.0
L
60.0
MP Shifts Load
Forward
45-deg
plies
Reduces Load
In Lower AftSpar Cap
Transition From CompressionBuckling Design (Wing Root) to
Shear-Buckling Design (Mid-Span)
Ply Percentage
A
5.0
B
10.0
C
15.0
D
20.0
E
25.0
F
30.0
G
35.0
H
40.0
I
45.0
J
50.0
K
55.0
L
60.0
Minimal Transition Provides
Evenly Balanced Wing-Bending
and Wing-Torsion Efficiency
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13
Summary and Conclusions
 LM Aero & MSC.Software Partnership
 New Functional Features for MSC.Nastran 2001
 Improved Integration With “In-House” Tools
 Sample Problems Illustrate Strengths of FSD and MP
MP
Criteria: Multi-Disciplinary Criteria (Sensitivities)
Speed:
Size: Conceptual/Preliminary-Quality FEM
FSD
Strength & Practicality Criteria
Independent Local Analyses
Production-Quality FEM
Intent: Define General Structural Characteristics Supports Structural Certification
 Effective Usage Scenario
 MP Addresses MDO Requirements at Concept/Prelim. Phase
 Establish Min. Structural Requirements (Gage, Ply %, etc.)
 FSD Provides Increment for Detail Strength Criteria
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14
Acknowledgements
Xiaoming Yu
 PCOMP Enhancements
Shengua Zhang
 DRESP3 Development
Vinh Lam and Steve Wilder
 MSC.Toolkit Enhancements
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