GLAST LAT Project
March 24, 2003
GLAST Large Area Telescope:
Gamma-ray Large
Area Space
Telescope
Tracker Subsystem
WBS 4.1.4
Structural Design and Analysis
Overview
Erik Swensen
HYTEC, Inc.
Tracker Mechanical Engineer
swensen@hytecinc.com
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
1
GLAST LAT Project
March 24, 2003
Presentation Outline
•
•
•
•
•
•
Design Requirements
Historical Perspective
Tower Structural Design Overview
Material Selection & Allowables
Tower Structural Analysis Overview
Attachment Component Design & Analysis Overview
– Flexures
– Thermal Straps
• Testing
– Completed & In-progress tests
– Scheduled tests
• Open Issues
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
2
GLAST LAT Project
March 24, 2003
Design Requirements: Quasi-Static Loads
• Static-Equivalent Accelerations
Launch Event
Design
Lift-Off/
1
MECO
0.2
6.8
2
Accept3
Qual 3
Unit
3.7
6.8
4.6
8.5
g
g
Lateral
Axial
Transonic
2.34
4.43
Rot X/Y
20.2
rad/s
Rot Z
Scale Factor
20.2
rad/s2
2
1.25
Source
(1) “Summary of the GLAST Preliminary CLA Results,” Farhad Tahmasebi, 11 Dec
2001.
(2) 433-IRD-0001, “Large Area Telescope (LAT) Instrument – Spacecraft Interface
Requirements Document,” May, 2002.
(3) “LAT Tracker Random Vibration Test Levels,” Farhad Tahmasebi, 27 Feb 2002.
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
3
GLAST LAT Project
March 24, 2003
Design Requirements: Grid Motion
• Tracker-to-Grid Maximum Interface Distortion
– Superimposed on MECO design limit loads
– NOT superimposed on vibration analysis or testing
Flexure Location
0° Midside Flexure
+45° Corner Flexure
+90° Midside Flexure
+135° Midside Flexure
-180° Midside Flexure
-135° Midside Flexure
-90° Midside Flexure
-45° Midside Flexure
Displacements
Radial (µm)
Vertical (µm)
46
93
81
165
14
91
-60
24
-29
0
20
0
0
0
-11
13
Source: LAT-SS-00788-01-D4, “LAT Environmental Specification,” 15 Nov 2002.
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
4
GLAST LAT Project
March 24, 2003
Design Requirements: Flexure Loads
• Corner Flexure Maximum Design Limit Loads
– Maximum from two CLA cycles
Load Direction
Shear
Tension
Compression
Flexure Design Limit Loads
(N)
1003
1277
1277
Source: LAT-SS-00788-01-D4, “LAT Environmental Specification,” 15 Nov 2002.
• Side Flexure Maximum Design Limit Loads
– Maximum from two CLA cycles
Load Direction
Shear
Tension
Compression
Flexure Design Limit Loads
(N)
2266
391
391
Source: LAT-SS-00788-01-D4, “LAT Environmental Specification,” 15 Nov 2002.
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
5
GLAST LAT Project
March 24, 2003
Design Requirements: Sine Vibe
Frequency
(Hz)
Acceptance Test Levels
5 to 6.2
Thrust
6.2 to 50
Lateral
5 to 50
Axis
Test Levels
Sweep Rate
1.27 cm (0.5 in.) double amplitude
1.0 g (zero to peak)
0.7 g (zero to peak)
4 oct/min
N/A
4 oct/min
Proto-Flight Qualification Test Levels
5 to 7.4
1.27 cm (0.5 in.) double amplitude
Thrust
7.4 to 50
1.4 g (zero to peak)
5 to 6.2
1.27 cm (0.5 in.) double amplitude
Lateral
6.2 to 50
1.0 g (zero to peak)
Qualification Test Levels
5 to 7.4
1.27 cm (0.5 in.) double amplitude
Thrust
7.4 to 50
1.4 g (zero to peak)
5 to 6.2
1.27 cm (0.5 in.) double amplitude
Lateral
6.2 to 50
1.0 g (zero to peak)
4 oct/min
4 oct/min
2 oct/min
2 oct/min
Source: LAT-SS-00788-01-D4, “LAT Environmental Specification,” 15 Nov 2002.
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
6
GLAST LAT Project
March 24, 2003
Design Requirements: Random Vibe
• GEVS General Spec applied along all three axes independently
20
50
800
2000
Overall
Frequency
(Hz)
20
80
500
2000
Overall
ASD Level (G2/Hz)
Acceptance
Qualification
0.01
0.02
0.06
0.12
0.06
0.12
0.01
0.02
8.7 Grms
12.3 Grms
Revised ASD Test Level*
(G2/Hz)
0.01
0.04
0.04
0.01
6.8 Grms
Acceleration Spectral Density Function
1.000
Qualification
Acceptance
Revised RV ASD
ASD (G 2/Hz)
Frequency
(Hz)
0.100
0.010
10
100
1000
10000
Frequency (Hz)
Source: GEVS-SE Rev A, “General Environmental Verification Specification for STS &
ELV Payloads, Subsystems, and Components,” June 1996, Section 2.4.2.5.
* Pending approval from GSFC & SLAC program offices.
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
7
GLAST LAT Project
March 24, 2003
Design Requirements: Dynamic Clearance
• Maintain positive clearance between adjacent TKR tower modules
(tower-to-tower collisions) (Source: Tracker-LAT ICD)
– Maintain minimum allocation of 1.5mm for dynamic response of
towers
• After fabrication/assembly tolerances, alignment, EMI
shielding, static response, & thermal distortion are considered
– Maximum dynamic response goal <145 µm RMS (Acceptance)
• Assumes adjacent towers are out-of-phase
• Maintain positive clearance between adjacent trays (tray-to-tray
collisions)
– Maintain minimum clearance of 2mm between adjacent trays
• Silicon-to-silicon clearance
– Minimum frequency goal of 500 Hz
• Fixed base boundary conditions at tray attachment locations
• Assumes adjacent trays are out-of-phase
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
8
GLAST LAT Project
March 24, 2003
Design Requirements: Temperature
• Tracker Temperature Requirements
– Maximum heat load = 8.7W
– Maximum Temperature @ top of tower module = 30°C
• Tracker-to-Grid Interface Temperatures
State
Qualification
Acceptance Test
Operating
Low Temp Limits
(°C)
-30
-20
-15
High Temp
Limits
+50
+30
+30
Survival
(°C)
Low = -30
High = +50
N/A
Source: LAT-SS-00788-01-D4, “LAT Environmental Specification,” 15 Nov 2002.
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
9
GLAST LAT Project
March 24, 2003
Additional Requirements
• Stay Clear Dimensions (Source: Tracker-LAT ICD)
– Straightness ≤ 300 µm from top to bottom
– Maximum outside dimensions (x & y) ≤ 371.7 mm
– Maximum height ≤ 640 mm above grid surface
• Launch Pressure (Source: LAT Environmental Specification)
– Shall survive the time rate of change of pressure per the Delta II
Payload Planner’s Guide, Section 4.2.1, Figure 4.2.
– Extreme pressure conditions are experienced in the first 70 sec of
fairing venting.
• Venting (Source: Tracker-LAT ICD)
– Sufficient venting of all TKR components is required to allow
trapped gasses to release during launch.
• EMI Shielding (Source: Tracker-LAT ICD)
– Each TKR tower shall be covered on all 6 sides by at least 50 µm
of aluminum electrically connected to the Grid.
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
10
GLAST LAT Project
March 24, 2003
Historical Perspective
• Build-Test-Build Design Approach
– Limited schedule and budget to do all the analysis and material
testing judged necessary
– Tracker Tower ’01 Prototype was viewed as an engineering
evaluation model to reduce risk to the E/M Tower Testing
• Identify weaknesses in design early to allow for modifications
• Compressed schedule after E/M testing made it crucial to
insure against failures at that juncture
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
11
GLAST LAT Project
March 24, 2003
Hist Persp: Mechanical Prototypes
• Full-scale tray prototypes
– 14+ trays total (3 top/bottom, 7 thinconverter, 4 thick-converter)
• Full-scale tower prototype
– 10 composite trays w/ silicon payload
– 9 aluminum mass mockups
– YS-90A Sidewalls
• Prototype Tower Function
– Test component fabrication/assembly
procedures
– Test tray assembly tooling
– Test tower assembly procedures
– Validation of finite element models
– Test to environmental requirements at the
tray and tower level
– Reduce risk to E/M by identifying
weaknesses at prototype level
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
12
GLAST LAT Project
March 24, 2003
Hist Persp: Random Vibration Testing
• Qualification level random vibration testing performed along the lateral and
thrust axes to GEVS general specification
• Failures during 1st RV test
– Thermal gasket plastically deformed
@ -12dB
• Loss of thermal interface
– Loss of preload in sidewall fasteners
• @ 0dB in thrust direction
• @ -3dB in lateral direction
– Hairline fracture identified in one
corner after 0dB lateral test
• Prototype activities have a silver lining
– No evidence of structural damage @ -6dB (1.25dB below proposed
spec)
– Established manufacturing and assembly procedures for flight articles
– Minimizes risk of E/M tower by exposing weaknesses early
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
13
GLAST LAT Project
March 24, 2003
Tracker Tower Mechanical Configuration
• 5 Tray configurations supported by Thermal/Mechanical sidewalls
• 16 Towers separated by 2.5mm
Thermal/Mechanical
Sidewalls (4)
Top Tray (1)
{Not Shown for Clarity}
Thin-Converter
Trays (11)
Thick-Converter
Trays (4)
Standard Trays,
No Converter (2)
Bottom Tray (1)
Thermal Straps
- Copper (4)
HPS-102090-0002
Tower-to-Grid Flexure
Attachment (8)
Tracker Peer Review, WBS 4.1.4 Section 2-D
14
GLAST LAT Project
March 24, 2003
Tracker Tower Configuration
• Full coverage Gr/CE tower sidewalls
used for heat removal, stiffness,
EMI shielding
• Radial blade flexure configuration
for CTE mismatch with the Al grid
• Copper heat straps to conduct heat
away from the tower and into the
grid
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
15
GLAST LAT Project
March 24, 2003
Thermal/Mechanical Sidewalls
• Laminate Design
– [0/90fabric, 0, 157.5, 22.5, 45, 90, 135|s
– 50 µm Aluminum layer for EMI shielding on outer
surface
• Material
– Baseline @ PDR was YS-90A/RS-3
– Changed to K13D2U/RS-3 for improved thermal
performance
Sidewall Outside Surface
• Function
– Heat transfer: conduct tray heat to bottom tray and grid
– Stiffness: support individual trays, transfer load to
bottom tray
• K13D2U material testing
– Material order is in-progress
– Expected completion by June ‘03
Sidewall Inside Surface
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
16
GLAST LAT Project
March 24, 2003
Sidewall Mounting
• All trays except bottom tray attachment
– M2.5, CRES A286 fasteners
– NO metallic inserts in sidewall
• Bottom tray attachment
– M2.5 & M4, CRES A286 fasteners
– Metallic top-hat design inserts in
sidewall
M4
View of Bottom Tray
Sidewall Inserts
M4
Bottom Sidewall Section
M4
(M2.5 fasteners unless
marked otherwise)
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
17
GLAST LAT Project
March 24, 2003
Tray Sandwich Structure
• Lightweight 4 piece machined closeout frame, bonded to face sheets and
core to form a sandwich structure
Gr/CE Face Sheet
C-C Structural
Closeout Wall
Thermal Boss
1 lb/ft3 Aluminum
Honeycomb Core
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
C-C MCM Closeout Wall
18
GLAST LAT Project
March 24, 2003
Tray Configurations
• Thin-Converter and No-Converter trays are structurally identical
– Machined C-C closeout walls
– 1 lb/ft3 core
– Two 4-ply facesheets
• Balanced about the tray neutral axis
• Top tray uses a modified C-C closeout
– Machined C-C closeout walls
– 1 lb/ft3 core, ¾ thickness
– Two 4-ply facesheets
• Thick-Converter Trays use the same C-C closeout
– Machined C-C closeout
– 3 lb/ft3 core
– Two 6-ply quasi-isotropic facesheets
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
Thin-Converter
Tray Prototype
Top Tray Prototype
19
GLAST LAT Project
March 24, 2003
Machined Closeout Wall Prototypes
• Closeout frame is machined from 3D C-C material into the net shape
• Metallic inserts are bonded in frame for sidewall fasteners
• The frame is bonded in the four corners and mechanically connected
using a mortise and tenon joint
Outside
Outside
Inside
Inside
MCM Closeout Wall
HPS-102090-0002
Structural Closeout Wall
Tracker Peer Review, WBS 4.1.4 Section 2-D
20
GLAST LAT Project
March 24, 2003
Tracker Tray with Payload
• Tray payload is bonded to the sandwich structure using epoxy, with the
exception of silicone used to bond SSD’s
– Silicone decouples the thermal/mechanical effects from the tray
SSD’s
BiasCircuit
Structural
Tray
Converter
Foils
BiasCircuit
SSD’s
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
TMCM
21
GLAST LAT Project
March 24, 2003
Top Tray Configuration
• Uses same materials as the thinconverter trays
• ¾ thick honeycomb core vs. thinconverter trays
Top View
(illustration of
lifting features)
SSD’s
Converter
Foils
Gr/CE
Facesheet
BiasCircuit
1 lb/ft3 Aluminum
Honeycomb Core
C-C Closeout
Frame
TMCM
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
22
GLAST LAT Project
March 24, 2003
Bottom Tray Sandwich Structure
•
Lightweight 4 piece C-C & M55J machined closeout frame, bonded to face
sheets and core to form a sandwich structure
3 lb/ft3 Aluminum
Honeycomb Core
6-Ply Gr/CE Face Sheet
Structural
Closeout Wall
Thermal Boss
Titanium Corner
Reinforcement
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
MCM Closeout Wall
23
GLAST LAT Project
March 24, 2003
Bottom Tray Closeout Walls
• Bonded M55J/RS-3 internal frame
for strength and stiffness
• Machined C-C outside laminate for
thermal transfer of MCM heat
M55J/RS-3
Internal Frame
C-C Outside
Laminate
MCM Closeout Wall
Typical Closeout Wall
Cross-Section
(not to scale)
Structural Closeout Wall
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
24
GLAST LAT Project
March 24, 2003
Corner Joint Details
Pins
(Reinforce Butt-Joint)
Sandwich Structure w/
Reinforcement Brackets
(Typ, 4 places)
MCM
Closeout Wall
Bonded Butt-Joint
Corner Reinforcement Bracket
(Bonded)
Structural
Closeout Wall
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
25
GLAST LAT Project
March 24, 2003
Corner Reinforcement Bracket
• Machined Titanium Reinforcement Bracket
– Strength & Stiffness
Sandwich Structure w/
Reinforcement Brackets
(Typ, 4 places)
Typical Machined Taper
(Reduce Peel Stress)
Corner Block
(Shear Reinforcement)
Slots for M55J Closeouts
(Bonded Interface)
Inside View of Corner
Reinforcement Bracket
HPS-102090-0002
Corner Flexure Mounting Slot
(Press Fit, 2 Pins, 1 Fastener)
Tracker Peer Review, WBS 4.1.4 Section 2-D
26
GLAST LAT Project
March 24, 2003
Bottom Tray with Payload
•
•
Payload attached to top side only
Tray payload is bonded to the sandwich structure using epoxy, with the
exception of silicone used to bond SSD’s
– Silicone decouples the thermal/mechanical effects from the tray below
SSD’s
Bias-Circuit
Structural
Tray
HPS-102090-0002
TMCM
Tracker Peer Review, WBS 4.1.4 Section 2-D
27
GLAST LAT Project
March 24, 2003
Mat’l Selection: Structural/Thermal
Component
Material
Tray Sandwich Structure
Facesheets
Honeycomb Core
Closeout Walls (All)
Closeout Walls (Bottom Only)
Corner Brackets (Bottom Only)
Metallic Inserts
Pins (Bottom Only)
Structural Adhesives
YSH-50/RS-3
3
3
1 lb/ft & 3 lb/ft 5056 Aluminum
3D Carbon-Carbon
M55J/RS-3
6AL-4V Titanium (Annealed)
7075-T76 Aluminum
304 Stainless
HYSOL EA-934NA
HYSOL EA-9394
Redux 312 UL
Thermal/Mechanical Sidewalls
Gr/Ce Fabric Plies
YS-90A/RS-3
Gr/Ce Unidirectional Plies
K13D2U/RS-3
EMI Shielding
5056 Aluminum Foil
EMI Tape
3M-1170 Tape
Conductive Paint
Lord Z307
Metallic Inserts
7075-T76 Aluminum
Adhesive
CYTEC/Fiberite FM 73M
Tower
Flexures
6AL-4V Titanium (STA)
Heat Straps
H04 Copper (w/ nickle plating)
Fasteners
Cres-A286 Steel
Pins
304 SST
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
28
GLAST LAT Project
March 24, 2003
Material Allowables: Stresses
Material
Stress
Direction
Ult Material
Allowable
(MPa)
Ult Material
Allowable Method of Verification
(ksi)
Tray Sandwich Structure Assemblies
3D Carbon - Carbon
YS-50/RS-3 (4 Ply)
YS-50/RS-3 (6 Ply)
Alum H/C Core 1.0 PCF
Alum H/C Core 3.0 PCF
3D M55J/RS-3
(Quasi-Iso Layup)
HPS-102090-0002
x
69.0
10.0
B Basis Test Data- Compr
y
54.5
7.9
B Basis Test Data- Compr
z
10.3
1.5
B Basis Test Data
xy
52.1
7.6
B Basis Test Data
zx
25.2
3.7
B Basis Test Data
yz
13.9
2.0
Stress
Direction
Material
Ult Material
Allowable
(MPa)
Ult Material
Allowable Method of Verification
(ksi)
Tray Sandwich Structure Assemblies (Cont)
tu
896.6
130.0
MIL-HDBK-5H
ty
827.6
120.0
MIL-HDBK-5H
u
544.8
79.0
MIL-HDBK-5H
tu
496.6
72.0
MIL-HDBK-5H
ty
427.6
62.0
MIL-HDBK-5H
B Basis Test Data
u
289.7
42.0
MIL-HDBK-5H
Thermal/Mechanical Sidewalls
x
206.0
29.9
Test Data & Comp Analysis
y
206.0
29.9
Test Data & Comp Analysis
xy
155.0
22.5
Test Data & Comp Analysis
Titanium 6AL-4V (Annealed)
Aluminum 7075-T76
YS-90A/RS-3
x
206.0
29.9
Test Data & Comp Analysis
y
304.0
44.1
Test Data & Comp Analysis
xy
178.0
25.8
Test Data & Comp Analysis
compr
0.241
0.035
Hexcel TSB 120
zx
0.310
0.045
Hexcel TSB 120
yz
0.172
0.025
Hexcel TSB 120
compr
1.793
0.260
Hexcel TSB 120
zx
1.379
0.200
Hexcel TSB 120
yz
0.759
0.110
Hexcel TSB 120
K13D2U/RS-3
x
196.4
28.5
Test Data & Comp Analysis
y
122.0
17.7
Test Data & Comp Analysis
x
196.4
28.5
YS-90A Data (need confirmation)
y
122.0
17.7
YS-90A Data (need confirmation)
Tower Assembly
Copper UNS C10100 ;H04
Temper - (Thermal Strap)
Titanium 6AL-4V (STA) (Base Flexures)
tu
344.8
50.0
Common Vendor data
ty
310.3
45.0
Common Vendor Data
u
195.2
28.3
Common Vendor Data
tu
1103.4
160.0
MIL-HDBK-5H
ty
1034.5
150.0
MIL-HDBK-5H
u
689.7
100.0
MIL-HDBK-5H
bond
21.4
3.1
Hysol Product Data
fw
20.7
3.0
Hysol Product Data
bond
29.0
4.2
Hysol Product Data
x
332.1
48.2
80% of Vendor Data - compr
y
332.1
48.2
80% of Vendor Data - compr
z
14.7
2.1
80% of Vendor Data - FW tension
xy
187.0
27.1
80% of Vendor Data
fw
20.7
3.0
Hysol Product Data
zx
52.4
7.6
80% of Vendor Data
bond
35.2
5.1
CYTEC/Fiberite Product Data
yz
52.4
fw
20.7
3.0
Used EA9394 data
HYSOL 934NA Adhesive
HYSOL 9394 Adhesive
CYTEC FM73 Film Adhesive
7.6
80% of Vendor Data
Tracker Peer Review, WBS 4.1.4 Section 2-D
29
GLAST LAT Project
March 24, 2003
Material Allowables: Forces
Material
Force
Direction
FUlt Material FUlt Material
Allowable
Allowable Method of Verification
(N)
(lbf)
Bolt/Insert Attachments
2.5mm Sidewall No Insert
2.5mm Sidewall w/Insert
4mm Sidewall w/Insert
2.5mm CC w/Insert
2.5mm CC/M55J w/Insert
4mm CC/M55J w/Insert
1.6mm Screw (MCM Board)
2.5mm Screw (Countersunk)
4mm Screw (Countersunk)
4mm Screw (Cap Hd)
HPS-102090-0002
Fs 
Fs//
Faxial
Fs 
Fs//
Faxial
Fs 
Fs//
Faxial
Fs 
Fs//
Faxial
Fs 
Fs//
Faxial
Fs 
Fs//
Faxial
1231
277
B Basis Test Data - YS90
1260
284
B Basis Test Data - YS90
504
113
B Basis Test Data - YS90
1556
350
B Basis Test Data - YS90
1454
327
B Basis Test Data - YS90
656
148
B Basis Test Data - YS90
3073
691
B Basis Test Data - YS90
2764
622
B Basis Test Data - YS90
504
113
based on 2.5mm data
449
101
B Basis Test Data - YS90
449
101
based on perp. Data
1182
266
80% of min
1221
275
analysis w/1.25 FS
1221
275
based on perp. Data
1182
266
from CC insert data
1360
306
from CC Test Data
1360
306
based on perp. Data
1182
266
use 2.5mm Test data
Ft
272
61
Test Data - 80% of min
Ft
Fs
Ft
Fs
Ft
Fs
2979
670
Analysis & MIL-HDBK-5H
920
207
Analysis & MIL-HDBK-5H
5800
1305
Analysis & MIL-HDBK-5H
2642
594
Analysis & MIL-HDBK-5H
7832
1762
Analysis & MIL-HDBK-5H
3925
883
Analysis & MIL-HDBK-5H
Tracker Peer Review, WBS 4.1.4 Section 2-D
30
GLAST LAT Project
March 24, 2003
Analysis FS & MS Requirements
• Factors-of-Safety on static loads/stresses
– Factors-of-Safety to Yield = 1.25
– Factors-of-Safety to Ultimate = 1.4
• Factors-of-Safety on random vibration loads/stresses
– Factors-of-Safety to Yield = 1.00
– Factors-of-Safety to Ultimate = 1.12
– Lower Factors-of-Safety on RV vs Static
• 3σ on GEVS general spec is conservative
• Used lower damping (Q = 10) vs test results indicate (Q ~7)
– Higher amplification of tower response → higher loads/stresses
• Margins-of-Safety
– Margin-of-Safety Equation = Sallowable/(FS * Smax) – 1
– All Margins must be above 0.00
Reference: NASA-STD-5001
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
31
GLAST LAT Project
March 24, 2003
Tower Finite Element Modeling
Element/Node Count
Number
Number
Number
Number
Number
Number
of
of
of
of
of
of
Grids =
BAR Elements =
Spring Elements =
Solid Elements =
Plate Elements =
Rigid Elements =
227653
1038
63316
120628
56442
219
Mass Properties of FEM
Mass = 32.48 kg
Center of Gravity Location:
Xcg = -1.06E-5 m
Ycg = -4.26E-7 m
Zcg = 0.2623 m
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
32
GLAST LAT Project
March 24, 2003
Tower Finite Element Modeling (Con’t)
Model Checks
• Free-Free Modal and Rigid Body checks
were run on the stiffness matrix
• No model grounding or ill-conditioning
of the stiffness matrix
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
33
GLAST LAT Project
March 24, 2003
“CLA” Finite Element Model
• Reduced model delivered to SLAC early March ‘03
Element/Node Count
Number
Number
Number
Number
Number
Number
of
of
of
of
of
of
Grid Points =
BAR Elements =
Spring Elements =
Mass Elements =
Plate Elements =
Rigid Elements =
991
740
48
8
644
24
Mass Properties
Mass = 32.50 kg
Center of Gravity Location:
Xcg = 4.4E-8 m
Ycg = 3.9E-8 m
Zcg = 0.26 m
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
34
GLAST LAT Project
March 24, 2003
Tower Modal Analysis
1st Bending Mode
- Y Direction –
182.1 Hz
HPS-102090-0002
2nd Bending Mode
- X Direction –
183.6 Hz
Tracker Peer Review, WBS 4.1.4 Section 2-D
35
GLAST LAT Project
March 24, 2003
Tower Modal Analysis (Con’t)
1st Axial Mode
- Z Direction –
379.0 Hz
HPS-102090-0002
1st Torsional Mode
- About Z –
461.8 Hz
Tracker Peer Review, WBS 4.1.4 Section 2-D
36
GLAST LAT Project
March 24, 2003
Tower RV Analysis: Accelerations
• Equivalent quasi-static accelerations from random vibration input
Vibration Direction
Input Levels
1 Sigma Response
at CG
3 Sigma Response
at CG
Accept.
Qual
Accept.
Qual
Accept.
Qual
Lateral X
8.6
12.3
11.1
15.7
33.2
47.0
Lateral Y
8.6
12.3
11.2
15.8
33.5
47.3
44.4
63.0
Axial Z
8.6
12.3
14.8
21.0
* Note: Values used in quasi-static analysis and static proof tests
19th Tray
Response
Grms
10th Tray
Response
35
30
Accept.
25
Qual
20
15
10
5
0
Bottom Tray
Response
HPS-102090-0002
0
0.15
0.3
0.45
0.6
Response location from Bottom (m )
Tracker Peer Review, WBS 4.1.4 Section 2-D
37
GLAST LAT Project
March 24, 2003
Tower RV Analysis: RMS Displacements
Displacement Direction (µm)
Y
Z
RV in X (1RMS)
117
1
25
RV in Y (1RMS)
1
118
24
RV in Z (1RMS)
4
1
17
0.24
0.23
4.86
Min M.S.
• Maximum RMS Response to
Acceptance Level RV Input
• Min MS is +0.23
Lateral Response to Lateral Y Input
(Q = 10)
100.000
Qual Base Input 12.3 Grms
Qual. Tip Response 31.3 Grms
Acceptance Base Input 8.7 Grms
10.000
Accept. Tip Response 22.1 Grms
"Revised" Base Input 6.8 Grms
"Revised" Tip Response 17.8 Grms
Acceleration (G^2/Hz)
X
1.000
0.100
0.010
0.001
10.0
100.0
1000.0
Frequency (Hz)
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
38
GLAST LAT Project
March 24, 2003
Tray Finite Element Modeling
• Tray FE models were constructed
for all five tray types
• Modal and random vibration
analysis performed
• Results are summarized in HTN102070-0005
Detailed HYTEC Tray FEM
(Top, Thin-, No-Converter)
Detailed INFN Tray FEM
(Thick-Converter)
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
39
GLAST LAT Project
March 24, 2003
FE Modal Analysis Results
Tray Description
Top Tray
Thin-Converter Tray
Thick-Converter Tray
No-Converter Tray
Bottom Tray
Frequencies (Hz)
Without Payload
With Payload
Stiffness Effects
Stiffness Effects
569
584
N/A
718
767
673
711
518
764
788
• Fixed Base Boundary Conditions
– Simply supported at sidewall
attachment locations
• Payload stiffness effects include
Tungsten and bias-circuits
– Silicon applied as mass only
Typical 1st Mode Shape of
the Thin-Converter Tray
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
40
GLAST LAT Project
March 24, 2003
Bottom Tray Finite Element Modeling
• Fidelity of FEM is sufficient to calculate stresses
• Analysis in tower configuration
• Static analysis to estimate stresses during design phase
– Equivalent static accelerations calculated to simulate 3σ random
vibe environment
• Random Vibe Analysis to calculated RMS stresses to finalize design
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
41
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Design Limit Loads
• Liftoff & Transonic Minimum Margin-of-Safety
– Minimum Margins & Failure are shown
MS= 9.95
Ply Failure
MS= 10.38
Core Crush
MS= 10.77
Ply Failure
MS= 7.18
M55J Flatwise
Tension
MS= 7.32
Ti Ftg Bond Shear
MS= 7.21
M2.5 Bolt Shear
HPS-102090-0002
MS= 5.20
M4 Bolt Shear
Tracker Peer Review, WBS 4.1.4 Section 2-D
Tension
Zero
Compression
42
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Design Limit Loads
• Main Engine Cut-Off (MECO) Minimum Margin-of-Safety
– Minimum Margins & Failure are shown
– Grid Distortion included
MS= 3.28
Ply Failure
MS= 2.78
Core Crush
MS= 3.59
Ply Failure
MS= 1.41
M55J Flatwise
Tension
MS= 6.12
M2.5 Bolt Shear
MS= 2.64
Ti Ftg Bond Shear
Tension
MS= 6.13
C-C Flatwise Tension
HPS-102090-0002
MS= 3.45
M4 Bolt Shear
Tracker Peer Review, WBS 4.1.4 Section 2-D
Zero
Compression
43
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Random Vibrations
• RMS stresses calculated from random vibration analysis
– 3σ stresses used in margin calculation
• Sandwich structure Minimum Margin-of-Safety shown
MS= 1.13
[RV in X]
Ply Failure
MS= 1.36
[RV in X]
Ply Failure
MS= 0.84
[RV in X]
Core Crush
Tension
Zero
Compression
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
44
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Random Vibrations
• RMS stresses calculated from random vibration analysis
– 3σ stresses used in margin calculation
• M55J/RS-3 Closeout Frame Minimum Margin-of-Safety shown
MS= 1.40
[RV in Y]
M55J IL Shear
MS= .40
[RV in X]
Flatwise Tensile
MS= 2.44
[RV in Y]
M55J Ply Failure
Tension
Zero
Compression
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
45
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Random Vibrations
• RMS stresses calculated from random vibration analysis
– 3σ stresses used in margin calculation
• C-C Closeout Frame Minimum Margin-of-Safety shown
MS= .47
[RV in X]
C-C IL Shear
(Near Bolt)
MS= 1.65
[RV in Y]
C-C IL Shear
(Boss transition)
Tension
Zero
Compression
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
46
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Random Vibrations
• RMS stresses calculated from random vibration analysis
– 3σ stresses used in margin calculation
• Closeout Frame Assy Minimum Margin-of-Safety shown
MS= .51
[RV in X]
Ti Ftg Bond Shear
MS= .34
[RV in Y]
M2.5 Bolt Shear
HPS-102090-0002
MS= 2.18
[RV in X]
M55J to CC Bond Shear
MS= .54
[RV in Y]
Flexure Bond
Shear
Tracker Peer Review, WBS 4.1.4 Section 2-D
Tension
Zero
Compression
47
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Random Vibrations
• RMS stresses calculated from random vibration analysis
– 3σ stresses used in margin calculation
• Ti Corner Bracket Minimum Margin-of-Safety shown
MS= 3.40
Max VM Stress
[RV in Y]
Tension
Zero
Compression
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
48
GLAST LAT Project
March 24, 2003
Side Wall Margins of Safety
• Insert MS is calculated using the interaction of the vertical and
lateral loads
M4 Side Wall
Insert Shearout
Load Case
Min MS
L/O
5.20
MECO
2.18
RV in Y
0.04
Side Wall
Ply Failure
MS= .40
M4 Side Wall
Insert Shear
[RV in X]
Load Case
Min MS
L/O
1.70
MECO
1.02
RV
1.56
Tension
Basic Interaction Eqn: MS = 1/sqrt[Rx^2+Ry^2] –1
(Where: Rx = σx/ σallowable)
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
Zero
Compression
49
GLAST LAT Project
March 24, 2003
Tray’s 2-19 Minimum Margins
M2.5 C-C Shearout
Load Case
M2.5 C-C Shearout
Min MS
Load Case
Min MS
L/O
13.09
L/O
14.12
MECO
9.67
MECO
10.43
Random Vibe (X)
1.49
Random Vibe (Y)
1.20
C-C Section Stress
w/SC Factor of 2.0
Load Case
M2.5 C-C Shearout
Load Case
Min MS
Min MS
L/O
8.25
L/O
33.01
MECO
2.59
MECO
12.38
Random Vibe (Y)
0.26
Random Vibe (Z)
0.87
Tension
(Bottom Tray Not Shown)
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
Zero
Compression
50
GLAST LAT Project
March 24, 2003
Bottom Tray Margins: Revised RV Spec
• Lowered Max Lateral Equiv. Static G’s from 47.3 to 27.0
– Minimum Margins & Failure are shown
MS= 2.74
Ply Failure
MS= 2.21
Core Crush
MS= 3.14
Ply Failure
MS= 1.46
M55J Flatwise
Tension
MS= 1.12
Ti Ftg Bond Tensile
MS= 1.35
M2.5 Bolt Shear
HPS-102090-0002
MS= 0.83
M4 Sidewall
Insert Shearout
Tracker Peer Review, WBS 4.1.4 Section 2-D
Tension
Zero
Compression
51
GLAST LAT Project
March 24, 2003
TKR Tower Margin-of-Safety Summary
• Liftoff-and-Transonic
– Minimum Margin-of-Safety is +1.70
• Sidewall ply failure
• MECO + Grid Distortion
– Minimum Margin-of-Safety is +1.02
• Sidewall ply failure
• Random Vibration
– Minimum Margin-of-Safety in X is +0.40
• M4 Side Wall Corner Insert Shearout
– Minimum Margin-of-Safety in Y is +0.04
• M4 Side Wall Corner Insert Shearout
– Minimum Margin-of-Safety in Z is +1.37
• M4 Side Wall Corner Insert Shearout
• ALL Margins-of-Safety Meet Requirement (>0.00)
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
52
GLAST LAT Project
March 24, 2003
Flexure-to-Grid Attachment Configuration
•
•
8-Blade Configuration
– 4 blades in each corner
– 4 blades along each side
Allow radial distortion of grid due to thermal input
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
53
GLAST LAT Project
March 24, 2003
Titanium Flexures
•
•
•
Material – 6Al-4V Titanium STA
Tapered 3-Blade Design
– Minimize length/maximize stiffness
Center Stiffener to increase critical buckling
3-Blade Design
(High Shear Strength,
Maximize Axial Stiffness)
Side Flexure
Thick Center Section
(Increase Euler Buckling)
Tapered Blade
(High Shear Strength,
Minimum Normal Stiffness)
Typical Blade
Features
HPS-102090-0002
Corner Flexure
Tracker Peer Review, WBS 4.1.4 Section 2-D
54
GLAST LAT Project
March 24, 2003
Flexure Finite Element Modeling
• Detailed finite element model of each flexure
type was constructed
– Evaluated loads equivalent to 47.3 G’s
lateral and 63 G’s vertical
Corner Flexure FEM
Side Flexure FEM
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
55
GLAST LAT Project
March 24, 2003
Corner Flexure Margins
Load Case
Interface Design Loads
Liftoff & Transonic
MECO + Grid Distortion
Random Vibration Loads
Thermal Distortion
(CTE Mismatch w/ Grid)
Margin-of-Safety
Ultimate
Yield
0.83
0.92
2.16
2.32
1.86
2.00
0.29
0.35
1.13
von Mises Stresses
from Shear Load
1.24
Note: All Margin calculations include fabrication tolerances
von Mises Stresses
from Normal Load
Von Mises Stresses
High
Medium
Low
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
56
GLAST LAT Project
March 24, 2003
Side Flexure Margins
Load Case
Interface Design Loads
Liftoff & Transonic
MECO + Grid Distortion
Random Vibration Loads
Thermal Distortion
(CTE Mismatch w/ Grid)
Margin-of-Safety
Ultimate
Yield
0.77
0.86
1.84
1.98
1.89
2.04
0.41
0.48
1.01
von Mises Stresses
from Shear Load
1.12
Note: All Margin calculations include fabrication tolerances
von Mises Stresses
from Normal Load
Von Mises Stresses
High
Medium
Low
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
57
GLAST LAT Project
March 24, 2003
Heat Strap-to-Grid Attachment Configuration
•
4-Strap Configuration
– Sandwiched between the thermal boss and sidewall
– RTV adhesive to improve heat transfer between interfaces (TKR side
only)
– Bolted interface w/ pressure plate (not shown) for dry interface
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
58
GLAST LAT Project
March 24, 2003
Heat Strap Design
Angle in Section
Reduces Stiffness
Slots in Section
Reduces Stiffness
Cross-Section
Stress Relief
(Holes)
Illustration of
Copper Layers
Pressure Plate
(Grid Interface)
HPS-102090-0002
4 Stacked Cu Foils
t = 0.2 mm each
t = 0.8 mm total
(Reduce Stress)
Tracker Peer Review, WBS 4.1.4 Section 2-D
59
GLAST LAT Project
March 24, 2003
Heat Strap Analysis: Stress Analysis
• Maximum load case is the lateral
random vibration
– Shear deformation shown below
• Minimum Margin-of-Safety is +0.52
Von Mises Stresses
High
Medium
Low
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
60
GLAST LAT Project
March 24, 2003
Testing
• Mechanical testing of materials/joints
– Composite material testing
• Closeouts, facesheets, sidewalls, sandwich structure
– Joints
• M2.5 & M4 inserts in sidewall and closeouts
– Bonding
• Facesheets-to-closeout, corner joints
• Thermal testing of materials/joints
– Conductivity testing of composite materials
• CTE mismatch testing:
– Si detector bonding to composite sandwich structure
– Bottom tray-to-grid attachment configuration
• Venting of trays: Verify acceptable venting under vacuum
• Modal Testing: Thin- & thick-converter tray modal survey
• Random Vibration Testing: TKR tower ’01 prototype
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
61
GLAST LAT Project
March 24, 2003
Tray Vibration Testing
• Thin-Converter Tray Vibration Test
– Performed in Albuquerque, NM
– Fixed boundary conditions at
Sidewall attachment locations
– Modal survey in Thrust direction
– Random vibration test to GEVS
general spec @ qualification level
•
HPS-102090-0002
Conclusions
– Measured 710 Hz fundamental
frequency vs. 711 Hz FEA
– No indication of damage after
qualification level (0dB) RV test
– No indication of Carbon
dusting after test
Tracker Peer Review, WBS 4.1.4 Section 2-D
62
GLAST LAT Project
March 24, 2003
Tray Vibration Testing (Con’t)
• Thick-Converter Tray Vibration Test
– Performed in Milan, Italy
– Fixed boundary conditions at
Sidewall attachment locations
– Modal survey in Thrust direction
– Random vibration test to GEVS
general spec @ qualification level
•
HPS-102090-0002
Conclusions
– Measured 580 Hz fundamental
frequency vs. 518 Hz FEA
– No indication of damage after
qualification level (0dB) RV test
Tracker Peer Review, WBS 4.1.4 Section 2-D
63
GLAST LAT Project
March 24, 2003
Static Proof Test of Bottom Tray Interface
•
•
•
•
Validate bottom tray and flexure design with static proof test in the lateral
and vertical direction, scheduled for May ‘03
– Proof test to ±110% of Max expected load (GEVS qualification level RV
equivalent static load)
• 47.3 g’s in lateral direction
• 63.0 g’s in thrust direction
Two bottom trays will be tested
– 1 will be used in E/M RV test
– 1 will be tested to failure
2nd tray included in test
Static test goals
– Measure interface stiffness
– Proof test E/M bottom tray
– Verify capability of bottom tray design
– Verify flexure and heat strap design
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
{Sidewall not
shown for clarity}
64
GLAST LAT Project
March 24, 2003
Bottom Tray Test Configuration
C.G. Reaction Point
Tower Simulator
Flight Equivalent
Sidewalls
(K13D2U/RS-3)
Tray #2
Bottom Tray
Heat Straps
Flexures
Grid Simulator
Base Reaction
Frame
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
65
GLAST LAT Project
March 24, 2003
Lateral Test Configuration
Base Reaction into
Granite Table
Load Cell
{Not Shown}
Spring Assembly
Reaction Frame
{Outer Plate Not Shown}
HPS-102090-0002
Reaction
Shaft/Nut
Tracker Peer Review, WBS 4.1.4 Section 2-D
Displacement
Probes
66
GLAST LAT Project
March 24, 2003
Vertical Test Configuration
Base Reaction into
Granite Table
Reaction
Shaft/Nut
{Not Shown}
Spring Assembly
Reaction Frame
Load Cell
HPS-102090-0002
Displacement
Probes
Tracker Peer Review, WBS 4.1.4 Section 2-D
67
GLAST LAT Project
March 24, 2003
E/M Testing
• E/M prototype trays are being fabricated
– E/M bottom tray is scheduled for delivery to INFN in June ’03
– Testing scheduled to begin at the end of June ’03
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
68
GLAST LAT Project
March 24, 2003
Open Issues
• Need confirmation of material/joint allowables
– C-C & M55J material testing is not complete
• Completion by Instrument CDR
– M2.5 & M4 bottom tray joint testing is not complete
• Completion by Instrument CDR
– K13D2U/RS-3 Sidewall testing is not complete
• Completion by TBD
• Static proof testing will be completed after Instrument CDR
– Scheduled for May/June ‘03
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
69
GLAST LAT Project
March 24, 2003
Backup Slides
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
70
GLAST LAT Project
March 24, 2003
Thermal Distortion
Ma
T = 2°C
T = 5°C
[x=0 → T=2; x=h → T=0]
[x=0 → T=5; x=h → T=0]
CTE
(ppm/°C)
P'x
(mm)
P'z
(mm)
Q'x
(mm)
P'x
(mm)
P'z
(mm)
Q'x
(mm)
Aluminum
23.6
23.1
29.3
32.4
57.7
73.2
80.9
Beryllium
11.3
11.1
14.0
15.5
27.6
35.0
38.7
Gr-CE
Composite
z: -1.5
x: -0.5
-1.5
-1.9
-1.8
-3.7
-4.7
-4.4
CC
Composite
z: -1.5
x: -1.2
-1.5
-1.9
-2.2
-3.7
-4.7
-5.5
terial
z
• Pre-PDR Thermal Distortion analysis
• Thermal Distortion of tower considered benign
w/ Gr/CE structural materials
• Thermal Distortion of grid is not – grid design
responsibility
P'
P
 Q
Q'
T
HPS-102090-0002
Tracker Peer Review, WBS 4.1.4 Section 2-D
x
71