GLAST LAT ProjectMarch 24, 2003 HPS-102090-0002 Tracker Peer Review, WBS 4.1.4 Section 2-D 1 GLAST...

GLAST LAT Project March 24, 2003

HPS-102090-0002 Tracker Peer Review, WBS 4.1.4 Section 2-D 1

GLAST Large Area Telescope:GLAST Large Area Telescope:

Tracker SubsystemWBS 4.1.4

Structural Design and Analysis Overview

Erik SwensenHYTEC, Inc.Tracker Mechanical Engineer

[email protected]

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope



Presentation OutlinePresentation 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



Design Requirements: Quasi-Static LoadsDesign Requirements: Quasi-Static Loads

• Static-Equivalent Accelerations

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.

Lift-Off/

Transonic1 MECO2

Lateral 2.34 0.2 3.7 4.6 gAxial 4.43 6.8 6.8 8.5 g

Rot X/Y 20.2 rad/s2

Rot Z 20.2 rad/s2

Scale Factor 1.25

UnitDesign

Launch Event Accept3 Qual3



Design Requirements: Grid MotionDesign Requirements: Grid Motion

• Tracker-to-Grid Maximum Interface Distortion– Superimposed on MECO design limit loads– NOT superimposed on vibration analysis or testing

Source: LAT-SS-00788-01-D4, “LAT Environmental Specification,” 15 Nov 2002.

Radial (µm) Vertical (µm)0° Midside Flexure 46 93+45° Corner Flexure 81 165+90° Midside Flexure 14 91+135° Midside Flexure -60 24-180° Midside Flexure -29 0-135° Midside Flexure 20 0-90° Midside Flexure 0 0-45° Midside Flexure -11 13

DisplacementsFlexure Location



Design Requirements: Flexure LoadsDesign Requirements: Flexure Loads

• Corner Flexure Maximum Design Limit Loads– Maximum from two CLA cycles


• Side Flexure Maximum Design Limit Loads– Maximum from two CLA cycles


Shear 1003Tension 1277Compression 1277

Load DirectionFlexure Design Limit Loads

(N)

Shear 2266Tension 391Compression 391

Load DirectionFlexure Design Limit Loads

(N)



Design Requirements: Sine VibeDesign Requirements: Sine Vibe


5 to 6.2 1.27 cm (0.5 in.) double amplitude 4 oct/min6.2 to 50 1.0 g (zero to peak) N/A

Lateral 5 to 50 0.7 g (zero to peak) 4 oct/min

5 to 7.4 1.27 cm (0.5 in.) double amplitude 4 oct/min7.4 to 50 1.4 g (zero to peak)5 to 6.2 1.27 cm (0.5 in.) double amplitude 4 oct/min6.2 to 50 1.0 g (zero to peak)

5 to 7.4 1.27 cm (0.5 in.) double amplitude 2 oct/min7.4 to 50 1.4 g (zero to peak)5 to 6.2 1.27 cm (0.5 in.) double amplitude 2 oct/min6.2 to 50 1.0 g (zero to peak)

AxisFrequency

(Hz)Test Levels Sweep Rate

Acceptance Test Levels

Proto-Flight Qualification Test Levels

Qualification Test Levels

Thrust

Thrust

Lateral

Thrust

Lateral



Design Requirements: Random VibeDesign Requirements: Random Vibe

• GEVS General Spec applied along all three axes independently

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.

Acceptance Qualification20 0.01 0.0250 0.06 0.12800 0.06 0.12

2000 0.01 0.02Overall 8.7 G rms 12.3 G rms

ASD Level (G2/Hz)Frequency (Hz)

Acceleration Spectral Density Function

0.010

0.100

1.000

10 100 1000 10000

Frequency (Hz)

ASD

(G2/H

z)

Qualification

Acceptance

Revised RV ASD

20 0.0180 0.04500 0.04

2000 0.01Overall 6.8 G rms

Frequency (Hz)

Revised ASD Test Level*

(G2/Hz)



Design Requirements: Dynamic ClearanceDesign 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



Design Requirements: TemperatureDesign Requirements: Temperature

• Tracker Temperature Requirements– Maximum heat load = 8.7W– Maximum Temperature @ top of tower module = 30°C

• Tracker-to-Grid Interface Temperatures


Qualification -30 +50 Low = -30Acceptance Test -20 +30 High = +50Operating -15 +30 N/A

StateLow Temp Limits

(°C)High Temp

Limits Survival

(°C)



Additional RequirementsAdditional 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.



Historical PerspectiveHistorical 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



Hist Persp: Mechanical PrototypesHist Persp: Mechanical Prototypes

• Full-scale tray prototypes– 14+ trays total (3 top/bottom, 7 thin-

converter, 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



Hist Persp: Random Vibration TestingHist Persp: Random Vibration Testing

• Qualification level random vibration testing performed along the lateral and thrust axes to GEVS general specification

• 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

• 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



Tracker Tower Mechanical ConfigurationTracker Tower Mechanical Configuration

• 5 Tray configurations supported by Thermal/Mechanical sidewalls

• 16 Towers separated by 2.5mm

Top Tray (1)

Standard Trays, No Converter (2)

Thick-Converter Trays (4)

Thin-Converter Trays (11)

Bottom Tray (1)

Thermal/Mechanical Sidewalls (4)

{Not Shown for Clarity}

Thermal Straps - Copper (4)

Tower-to-Grid Flexure Attachment (8)



Tracker Tower ConfigurationTracker 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



Thermal/Mechanical SidewallsThermal/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

• 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 Outside Surface

Sidewall Inside Surface



Sidewall MountingSidewall 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

Bottom Sidewall Section(M2.5 fasteners unless

marked otherwise)

View of Bottom Tray Sidewall Inserts

M4

M4

M4



Tray Sandwich StructureTray 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 MCM Closeout Wall

Thermal Boss

1 lb/ft3 Aluminum Honeycomb Core

C-C Structural Closeout Wall



Tray ConfigurationsTray 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 Top Tray Prototype

Thin-Converter Tray Prototype



Machined Closeout Wall PrototypesMachined 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

Structural Closeout WallMCM Closeout Wall

Inside

Outside

Inside

Outside



Tracker Tray with PayloadTracker 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

Bias-Circuit

Structural Tray

Converter Foils

TMCM

Bias-Circuit

SSD’s



Top Tray ConfigurationTop Tray Configuration

• Uses same materials as the thin-converter trays

• ¾ thick honeycomb core vs. thin-converter trays

Top View(illustration of

lifting features)

Bias-Circuit

Gr/CE Facesheet

Converter Foils

TMCM

SSD’s


C-C Closeout Frame



Bottom Tray Sandwich StructureBottom Tray Sandwich Structure

MCM Closeout Wall

Thermal Boss


Structural Closeout Wall

6-Ply Gr/CE Face Sheet

Titanium Corner Reinforcement

• Lightweight 4 piece C-C & M55J machined closeout frame, bonded to face sheets and core to form a sandwich structure



Bottom Tray Closeout WallsBottom Tray Closeout Walls

• Bonded M55J/RS-3 internal frame for strength and stiffness

• Machined C-C outside laminate for thermal transfer of MCM heat

MCM Closeout Wall


Typical Closeout WallCross-Section(not to scale)

M55J/RS-3Internal Frame

C-C Outside Laminate



Corner Joint DetailsCorner Joint Details

Pins(Reinforce Butt-Joint)

Sandwich Structure w/ Reinforcement Brackets

(Typ, 4 places)

Corner Reinforcement Bracket(Bonded)

MCM Closeout Wall

Bonded Butt-Joint




Corner Reinforcement BracketCorner Reinforcement Bracket

• Machined Titanium Reinforcement Bracket– Strength & Stiffness

Inside View of Corner Reinforcement Bracket

Sandwich Structure w/ Reinforcement Brackets

(Typ, 4 places)

Slots for M55J Closeouts(Bonded Interface)

Corner Block(Shear Reinforcement)

Corner Flexure Mounting Slot(Press Fit, 2 Pins, 1 Fastener)

Typical Machined Taper(Reduce Peel Stress)



Bottom Tray with PayloadBottom Tray with Payload

Bias-Circuit

Structural Tray TMCM

SSD’s

• 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



Mat’l Selection: Structural/ThermalMat’l Selection: Structural/Thermal

Component Material

Facesheets YSH-50/RS-3

Honeycomb Core 1 lb/ft3 & 3 lb/ft3 5056 Aluminum Closeout Walls (All) 3D Carbon-CarbonCloseout Walls (Bottom Only) M55J/RS-3Corner Brackets (Bottom Only) 6AL-4V Titanium (Annealed)Metallic Inserts 7075-T76 AluminumPins (Bottom Only) 304 Stainless

HYSOL EA-934NAHYSOL EA-9394

Redux 312 UL

Gr/Ce Fabric Plies YS-90A/RS-3Gr/Ce Unidirectional Plies K13D2U/RS-3EMI Shielding 5056 Aluminum FoilEMI Tape 3M-1170 TapeConductive Paint Lord Z307Metallic Inserts 7075-T76 AluminumAdhesive CYTEC/Fiberite FM 73M

Flexures 6AL-4V Titanium (STA)Heat Straps H04 Copper (w/ nickle plating)Fasteners Cres-A286 SteelPins 304 SST

Tray Sandwich Structure

Thermal/Mechanical Sidewalls

Tower

Structural Adhesives



Material Allowables: StressesMaterial Allowables: Stresses

MaterialStress

Direction

Ult Material Allowable

(MPa)


(ksi)Method of Verification Material

Stress Direction


(MPa)


(ksi)Method of Verification

x 69.0 10.0 B Basis Test Data- Compr

tu 896.6 130.0 MIL-HDBK-5H

y 54.5 7.9 B Basis Test Data- Compr

ty 827.6 120.0 MIL-HDBK-5H

z 10.3 1.5 B Basis Test Data

u 544.8 79.0 MIL-HDBK-5H

xy 52.1 7.6 B Basis Test Data

tu 496.6 72.0 MIL-HDBK-5H

zx 25.2 3.7 B Basis Test Data

ty 427.6 62.0 MIL-HDBK-5H

yz 13.9 2.0 B Basis Test Data

u 289.7 42.0 MIL-HDBK-5H

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



x 196.4 28.5 YS-90A Data (need confirmation)


y 122.0 17.7 YS-90A Data (need confirmation)

xy 178.0 25.8 Test Data & Comp Analysis

compr 0.241 0.035 Hexcel TSB 120

tu 344.8 50.0 Common Vendor data

zx 0.310 0.045 Hexcel TSB 120

ty 310.3 45.0 Common Vendor Data

yz 0.172 0.025 Hexcel TSB 120

u 195.2 28.3 Common Vendor Data

compr 1.793 0.260 Hexcel TSB 120

tu 1103.4 160.0 MIL-HDBK-5H

zx 1.379 0.200 Hexcel TSB 120

ty 1034.5 150.0 MIL-HDBK-5H

yz 0.759 0.110 Hexcel TSB 120

u 689.7 100.0 MIL-HDBK-5H

x 332.1 48.2 80% of Vendor Data - compr

bond 21.4 3.1 Hysol Product Data

y 332.1 48.2 80% of Vendor Data - compr

fw 20.7 3.0 Hysol Product Data

z 14.7 2.1 80% of Vendor Data - FW tension

bond 29.0 4.2 Hysol Product Data

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 7.6 80% of Vendor Data

fw 20.7 3.0 Used EA9394 data

K13D2U/RS-3

HYSOL 9394 Adhesive

CYTEC FM73 Film Adhesive

Alum H/C Core 1.0 PCF

Alum H/C Core 3.0 PCF

3D M55J/RS-3 (Quasi-Iso Layup)

Copper UNS C10100 ;H04 Temper - (Thermal Strap)

Titanium 6AL-4V (STA) - (Base Flexures)

HYSOL 934NA Adhesive

Tray Sandwich Structure Assemblies

Thermal/Mechanical Sidewalls

Tower Assembly

Tray Sandwich Structure Assemblies (Cont)

3D Carbon - Carbon

YS-50/RS-3 (4 Ply)

YS-50/RS-3 (6 Ply)

Titanium 6AL-4V (Annealed)

Aluminum 7075-T76

YS-90A/RS-3



Material Allowables: ForcesMaterial Allowables: Forces

MaterialForce

Direction

FUlt Material

Allowable (N)

FUlt Material

Allowable (lbf)

Method of Verification

Fs 1231 277 B Basis Test Data - YS90

Fs // 1260 284 B Basis Test Data - YS90

Faxial 504 113 B Basis Test Data - YS90



Faxial 656 148 B Basis Test Data - YS90



Faxial 504 113 based on 2.5mm data


Fs // 449 101 based on perp. Data

Faxial 1182 266 80% of min

Fs 1221 275 analysis w/1.25 FS


Faxial 1182 266 from CC insert data

Fs 1360 306 from CC Test Data


Faxial 1182 266 use 2.5mm Test data

1.6mm Screw (MCM Board) Ft 272 61 Test Data - 80% of min

Ft 2979 670 Analysis & MIL-HDBK-5H

Fs 920 207 Analysis & MIL-HDBK-5H





4mm Screw (Countersunk)

4mm Screw (Cap Hd)

2.5mm CC w/Insert

2.5mm CC/M55J w/Insert

4mm CC/M55J w/Insert

2.5mm Screw (Countersunk)

2.5mm Sidewall No Insert

2.5mm Sidewall w/Insert

4mm Sidewall w/Insert

Bolt/Insert Attachments



Analysis FS & MS RequirementsAnalysis 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



Tower Finite Element ModelingTower Finite Element Modeling

Number of Grids = 227653

Number of BAR Elements = 1038

Number of Spring Elements = 63316

Number of Solid Elements = 120628

Number of Plate Elements = 56442

Number of Rigid Elements = 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

Element/Node Count



Tower Finite Element Modeling (Con’t)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



““CLA” Finite Element ModelCLA” Finite Element Model

• Reduced model delivered to SLAC early March ‘03

Mass Properties

Element/Node Count

Number of Grid Points = 991

Number of BAR Elements = 740

Number of Spring Elements = 48

Number of Mass Elements = 8

Number of Plate Elements = 644

Number of Rigid Elements = 24

Mass = 32.50 kg

Center of Gravity Location:

Xcg = 4.4E-8 m

Ycg = 3.9E-8 m

Zcg = 0.26 m



Tower Modal AnalysisTower Modal Analysis

1st Bending Mode- Y Direction –

182.1 Hz

2nd Bending Mode- X Direction –

183.6 Hz



Tower Modal Analysis (Con’t)Tower Modal Analysis (Con’t)

1st Axial Mode- Z Direction –

379.0 Hz

1st Torsional Mode- About Z –461.8 Hz



Tower RV Analysis: AccelerationsTower RV Analysis: Accelerations

• Equivalent quasi-static accelerations from random vibration input

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

Axial Z 8.6 12.3 14.8 21.0 44.4 63.0

* Note: Values used in quasi-static analysis and static proof tests

Input Levels1 Sigma Response

at CG3 Sigma Response

at CGVibration Direction

19th Tray Response

10th Tray Response

Bottom Tray Response

0

5

10

15

20

25

30

35

0 0.15 0.3 0.45 0.6Response location from Bottom (m )

Grm

s

Accept.

Qual



Tower RV Analysis: RMS DisplacementsTower RV Analysis: RMS Displacements

• Maximum RMS Response to Acceptance Level RV Input

• Min MS is +0.23

X Y Z

RV in X (1RMS) 117 1 25

RV in Y (1RMS) 1 118 24

RV in Z (1RMS) 4 1 17

Min M.S. 0.24 0.23 4.86

Displacement Direction (µm)

Lateral Response to Lateral Y Input(Q = 10)

0.001

0.010

0.100

1.000

10.000

100.000

10.0 100.0 1000.0

Frequency (Hz)

Acc

eler

atio

n (

G^

2/H

z)

Qual Base Input 12.3 Grms

Qual. Tip Response 31.3 Grms

Acceptance Base Input 8.7 Grms

Accept. Tip Response 22.1 Grms

"Revised" Base Input 6.8 Grms

"Revised" Tip Response 17.8 Grms



Tray Finite Element ModelingTray Finite Element Modeling

• Tray FE models were constructed for all five tray types

• Modal and random vibration analysis performed

• Results are summarized in HTN-102070-0005

Detailed HYTEC Tray FEM(Top, Thin-, No-Converter)

Detailed INFN Tray FEM(Thick-Converter)



FE Modal Analysis ResultsFE Modal Analysis Results

• 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

Without Payload Stiffness Effects

With Payload Stiffness Effects

Top Tray 569 673Thin-Converter Tray 584 711Thick-Converter Tray N/A 518No-Converter Tray 718 764Bottom Tray 767 788

Frequencies (Hz)Tray Description



Bottom Tray Finite Element ModelingBottom 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



Bottom Tray Margins: Design Limit LoadsBottom Tray Margins: Design Limit Loads

• Liftoff & Transonic Minimum Margin-of-Safety– Minimum Margins & Failure are shown

Tension

Zero

Compression

MS= 9.95Ply Failure

MS= 10.38Core Crush

MS= 10.77Ply Failure

MS= 5.20M4 Bolt Shear

MS= 7.21M2.5 Bolt Shear

MS= 7.18M55J Flatwise

Tension

MS= 7.32Ti Ftg Bond Shear



Bottom Tray Margins: Design Limit LoadsBottom Tray Margins: Design Limit Loads

Tension

Zero

Compression

• Main Engine Cut-Off (MECO) Minimum Margin-of-Safety– Minimum Margins & Failure are shown– Grid Distortion included

MS= 3.28Ply Failure

MS= 2.78Core Crush

MS= 3.59Ply Failure

MS= 3.45M4 Bolt Shear

MS= 6.13C-C Flatwise Tension


Tension

MS= 2.64Ti Ftg Bond Shear




Bottom Tray Margins: Random VibrationsBottom 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= 0.84[RV in X]

Core Crush

MS= 1.36[RV in X]

Ply Failure

Tension

Zero

Compression





• M55J/RS-3 Closeout Frame Minimum Margin-of-Safety shown

Tension

Zero

Compression

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





• C-C Closeout Frame Minimum Margin-of-Safety shown

Tension

Zero

Compression

MS= .47[RV in X]

C-C IL Shear (Near Bolt)

MS= 1.65[RV in Y]

C-C IL Shear (Boss transition)





• Closeout Frame Assy Minimum Margin-of-Safety shown

MS= 2.18[RV in X]

M55J to CC Bond Shear

MS= .34[RV in Y]

M2.5 Bolt Shear

MS= .51[RV in X]

Ti Ftg Bond Shear

Tension

Zero

Compression

MS= .54[RV in Y]

Flexure Bond Shear





• Ti Corner Bracket Minimum Margin-of-Safety shown

Tension

Zero

Compression

MS= 3.40Max VM Stress

[RV in Y]



Side Wall Margins of SafetySide Wall Margins of Safety

Tension

Zero

Compression

MS= .40M4 Side Wall Insert Shear

[RV in X]

• Insert MS is calculated using the interaction of the vertical and lateral loads

Load Case Min MS

L/O 1.70

MECO 1.02

RV 1.56

Side WallPly Failure

Load Case Min MS

L/O 5.20

MECO 2.18

RV in Y 0.04

M4 Side Wall Insert Shearout

Basic Interaction Eqn: MS = 1/sqrt[Rx^2+Ry^2] –1 (Where: Rx = σx/

σallowable)



Tray’s 2-19 Minimum MarginsTray’s 2-19 Minimum Margins

Tension

Zero

Compression

Load Case Min MS

L/O 8.25

MECO 2.59

Random Vibe (Y) 0.26

Load Case Min MS

L/O 13.09

MECO 9.67

Random Vibe (X) 1.49

M2.5 C-C Shearout

M2.5 C-C Shearout

Load Case Min MS

L/O 14.12

MECO 10.43

Random Vibe (Y) 1.20

C-C Section Stress w/SC Factor of 2.0

M2.5 C-C Shearout

Load Case Min MS

L/O 33.01

MECO 12.38

Random Vibe (Z) 0.87

(Bottom Tray Not Shown)



Bottom Tray Margins: Revised RV SpecBottom Tray Margins: Revised RV Spec

• Lowered Max Lateral Equiv. Static G’s from 47.3 to 27.0– Minimum Margins & Failure are shown

Tension

Zero

Compression

MS= 2.74Ply Failure

MS= 2.21Core Crush

MS= 3.14Ply Failure

MS= 0.83M4 Sidewall

Insert Shearout



Tension

MS= 1.12Ti Ftg Bond Tensile



TKR Tower Margin-of-Safety SummaryTKR 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)



Flexure-to-Grid Attachment ConfigurationFlexure-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



Titanium FlexuresTitanium Flexures

• Material – 6Al-4V Titanium STA

• Tapered 3-Blade Design

– Minimize length/maximize stiffness

• Center Stiffener to increase critical buckling

Side Flexure

Corner FlexureTypical Blade

Features

Tapered Blade(High Shear Strength,

Minimum Normal Stiffness)

Thick Center Section(Increase Euler Buckling)

3-Blade Design(High Shear Strength,

Maximize Axial Stiffness)



Flexure Finite Element ModelingFlexure 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



Corner Flexure MarginsCorner Flexure Margins

High

Medium

Low

Von Mises Stresses

von Mises Stresses from Normal Load

von Mises Stresses from Shear Load

Ultimate YieldInterface Design Loads 0.83 0.92Liftoff & Transonic 2.16 2.32MECO + Grid Distortion 1.86 2.00Random Vibration Loads 0.29 0.35

Note: All Margin calculations include fabrication tolerances

Margin-of-SafetyLoad Case

Thermal Distortion (CTE Mismatch w/ Grid)

1.13 1.24



Side Flexure MarginsSide Flexure Margins

von Mises Stresses from Normal Load

von Mises Stresses from Shear Load

Ultimate YieldInterface Design Loads 0.77 0.86Liftoff & Transonic 1.84 1.98MECO + Grid Distortion 1.89 2.04Random Vibration Loads 0.41 0.48

Note: All Margin calculations include fabrication tolerances

Margin-of-SafetyLoad Case

Thermal Distortion (CTE Mismatch w/ Grid)

1.01 1.12

High

Medium

Low

Von Mises Stresses



Heat Strap-to-Grid Attachment ConfigurationHeat 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



Heat Strap DesignHeat Strap Design

Cross-Section

Illustration of Copper Layers

4 Stacked Cu Foils t = 0.2 mm eacht = 0.8 mm total(Reduce Stress)

Pressure Plate(Grid Interface)

Angle in Section Reduces Stiffness

Stress Relief(Holes)

Slots in Section Reduces Stiffness



Heat Strap Analysis: Stress AnalysisHeat Strap Analysis: Stress Analysis

• Maximum load case is the lateral random vibration– Shear deformation shown below

• Minimum Margin-of-Safety is +0.52

High

Medium

Low

Von Mises Stresses



TestingTesting

• 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



Tray Vibration TestingTray 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

• 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



• 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

Tray Vibration Testing (Con’t)Tray Vibration Testing (Con’t)

• Conclusions

– Measured 580 Hz fundamental frequency vs. 518 Hz FEA

– No indication of damage after qualification level (0dB) RV test



• 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

Static Proof Test of Bottom Tray InterfaceStatic Proof Test of Bottom Tray Interface

{Sidewall not shown for clarity}



Bottom Tray Test ConfigurationBottom Tray Test Configuration

Flight Equivalent Sidewalls

(K13D2U/RS-3)

C.G. Reaction Point

Grid Simulator Flexures

Bottom Tray

Tower Simulator

Base Reaction Frame

Heat Straps

Tray #2



Lateral Test ConfigurationLateral Test Configuration

Reaction Frame{Outer Plate Not Shown}

Spring Assembly

Load Cell

Displacement Probes

Reaction Shaft/Nut

Base Reaction into Granite Table

{Not Shown}



Vertical Test ConfigurationVertical Test Configuration

Reaction Frame

Spring Assembly

Load CellDisplacement

Probes

Reaction Shaft/Nut

Base Reaction into Granite Table

{Not Shown}



E/M TestingE/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



Open IssuesOpen 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



Backup SlidesBackup Slides



Thermal DistortionThermal Distortion

• 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

T

P P'

x

z

Q

Q'

T = 2°C[x=0 → T=2; x=h → T=0]

T = 5°C[x=0 → T=5; x=h → T=0]

Material

CTE(ppm/°C)

P'x

(m)

P'z

(m)

Q'x

(m)

P'x

(m)

P'z

(m)

Q'x

(m)

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

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GLAST LAT ProjectMarch 24, 2003 HPS-102090-0002 Tracker Peer Review, WBS 4.1.4 Section 2-D 1 GLAST...

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