LAT-PR-01278 Section 33-1 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003...

LAT-PR-01278 Section 3 3-1

GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003


3. Structural Design and Analysis3. Structural Design and Analysis


3. Structural Design and Analysis3. Structural Design and Analysis

25 March 2003

Martin Nordby [email protected] Nordby [email protected]


GLAST LAT Project

Mechanical Design Integration Peer Review, March 20033. LAT Structural Analysis (40 charts/75 min)3. LAT Structural Analysis (40 charts/75 min)

• Introduction

– Structural block diagram

– LAT internal design changes since Delta PDR

– Interface design changes since Delta PDR

• Design trade analyses performed and results

• Structural analysis overview

• Structural analysis modeling

– Requirements and compliance

– Analysis parameters and load case definitions• FEA model spec’s• Results are interface loads

• Analysis update

– Modal analysis

– Static-equivalent analyses

– Failure analyses

• Results and flow down (6 charts)

– Interface loads

– Environmental Spec. summary


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003LAT Structural Schematic DiagramLAT Structural Schematic Diagram

LAT Structural Schematic DiagramLAT Structural Schematic Diagram

Rad

iato

rRad

iato

r

Grid Base Ass’y

CAL

TKR

ACD

X-LAT Plate

EM

I S

kir

tRadMntBkt

Electronics

Htr SwBox

Spacecraft

LV Payload Attach Fitting

EM

I Skirt

RadMntBkt

Htr SwBox

SolarArray

SolarArray

Structural

EMI/Grounding

Accommodation

Direction of arrow signifiesdirection of reliance, or structuralsupport


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Internal Structural Design Changes Since Delta-PDRInternal Structural Design Changes Since Delta-PDR

• Stiffened TKR flexure connection to Grid

– This was part of TKR bottom tray re-design

– Effect was to increase TKR first-mode natural frequency

• Updated ACD model to reflect mass increase

– Added tile mass and BEA stiffness

• Tuned Grid Wing and bottom flange designs

– Modified Grid Wing design to attenuate high local loads around SC mount

– Added full bottom flange around Grid perimeter to react localized loads

• Moved Electronics Box structural mount to CAL back plate

– Boxes now hard-mounted to CAL plate by way of moment-bearing stand-offs

– Cleaner structural design simplifies analysis and test plans for CAL and Electronics groups

– Forces on X-LAT Plate are reduced to just inertial loads of the plate


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003LAT Structural Interface Design Changes Since Delta-PDRLAT Structural Interface Design Changes Since Delta-PDR

• Increased Radiator area to 2.78 m2 and finalized dimensions

– Modified Radiator aspect ratio at request of Spectrum

– Agreed on final width, based on reduction in spacing between Radiators

– Agreed on final height, based on final positioning of LAT and PAF stay-clear agreements with Boeing

• Finalized Radiator mount location to SC

– Moved mount location down at request of Spectrum

– This reduced Radiator first-mode natural frequency, but margin to 50 Hz requirements is still large

• Modified LAT-SC mount region

– Bolt-on Wing accommodates interface bracket to accept Spectrum’s flexure

– This reduces local stress concentrations in the Grid, while improving integration access for Spectrum

– Design is still in work—not yet finalized


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Trade Studies Since Delta PDRTrade Studies Since Delta PDR

• Moved Electronics Box structural mount to CAL back plate

– Boxes now hard-mounted to CAL plate by way of moment-bearing stand-offs

– Cleaner structural design simplifies analysis and test plans for CAL and Electronics groups

– Forces on X-LAT Plate are reduced to just inertial loads of the plate

• Radiator panel top profile

– Modified panel to a stepped top profile

– Radiator area is maximized, while providing good access volume under the ACD

• Acoustic test configuration

– Investigated acoustic testing without Radiators, to reduce complexity of STE and potential risk to Radiators

– Decided to keep baseline test configuration as-is: with Radiators integrated. This assures that coupling of acoustic energy into Grid is adequately tested


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Current State of Structural ModelCurrent State of Structural Model

• LAT structural model moved to NASTRAN

– Changed FEA software from ANSYS to NASTRAN to make it more compatible with GLAST project office

– Re-built model to improve dynamic analysis capabilities

– Model is used to generate system structural response and interface limit loads

• Subsystem models updated

– New TKR model from Hytec—including bottom tray and flexure design modifications

– Updated ACD model from GSFC—with new mass baseline

– Incorporated reduced CAL model from NRL

– New Radiator model from LM—including size and mount point modifications

– Re-built electronics—new model based on current E-Box and interface designs LAT Finite Element ModelLAT Finite Element Model


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Driving Structural RequirementsDriving Structural Requirements

Parameter Requirement Design Margin ComplyVer.

MethodLAT Configuration

LAT mass allocation < 3000 kg 2679.4 kg 320.6 kg Y MStructural, Loads

Fixed-base first-mode > 50 Hz 56.4 Hz 6.4 Hz Y T

TKR alignment during normal LAT operation< 7arc-sec 1s

radial4.1 arc-sec peak-

to-peak2.9 arc-sec + 5s Y T, A

Capable of exposure to static-equivalent launch loads

OK Y T, A

Capable of exposure to sinusoidal vibration launch loads

OK Y T

Capable of exposure to acoustic launch loads OK P T


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003LAT FEA Model Boundary ConditionsLAT FEA Model Boundary Conditions

• Accelerations

– Used LAT center-of-mass accelerations from LAT Environmental Spec. for structural load cases

• SC mounting

– X-Side SC mount: LAT restrained in the Y- and Z-directions

– Y-Side SC mount: LAT restrained in the X- and Z-directions

• Radiator mounting

– Radiators mounted to Grid through Radiator Mount Bracket beams

– SC boundary condition fixed in Y-direction (out-of-plane) only

LAT F.E.A. Properties and Current LAT EstimatesLAT F.E.A. Properties and Current LAT Estimates

Source: LAT-TD-00564-06 “LAT Mass Status Report, Mass Estimates for Mar 2003,” 7 Mar 2003

LAT Static-Equivalent Design AccelerationsLAT Static-Equivalent Design Accelerations

Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003

LAT F.E.A. Model MetricsLAT F.E.A. Model Metrics

LAT F.E.A. Current LAT Est.Subsystem Mass

(kg)Center of

Gravity (m)Mass (kg)

Center of Gravity (m)

TKR 520.1 261.85 505 230.0CAL 1375 -138.55 1376 -148.8ACD 268 348.00 270 318.2Radiators 71.67 -1034.30 77 -1368.6Grid Box 250.3 -231.00 253 -218.0Elec. Boxes 199.6 -348.25 199 -352.9Total 2685 -60.53 2679 -86.9

Model Feature Number

Nodes 56,458Total elements 64,091Point elements 448Shell elements 47,819Beam elements 15,160

LAT Design Unit

Launch EventLift-Off/ Airloads

MECO

Lateral 5.1 0.2 gAxial (Z) +4.1/-1.4 +6.8 g


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Structural Analysis Load Cases and RunsStructural Analysis Load Cases and Runs

• Modal analysis

– Mode shape analysis of full model, supported with radially-compliant interface

– Includes analysis of any/all modes of subsystems, and coupling between subsystem and LAT natural frequencies

• Structural analysis methodology

– Analyzed 1g static-equivalent acceleration loading along X, Y, Z axes

– Combined results by linear super-position to produce LAT load cases

– Post-processed results to yield predicted loads and pre-loads at interface joints

– No dynamic analyses were performed C.L.A. provides this

• Structural analysis runs

– Deflection• LAT distortions extracted from analysis results• Relative motions and deflections gleaned from results• These are for static-equivalent loading, only (no dynamic deflections)

– Thermal-mechanical• LAT distortion due to transient changes to the LAT Control Temp• Transient thermo-mechanical analysis only

– Interface Loads• Subsystem interface loads extracted from results


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Structural Load Case DefinitionsStructural Load Case Definitions

Load Case X Y Z (Thrust) Comments

LaunchModal on SC Mount Supports fixed in Z and hoop, free radiallyLift-Off/Airloads 1 +5.1g 0 g +4.1g LAT is +X/-X symmetricLift-Off/Airloads 2 0 g +5.1g +4.1g LAT is +Y/-Y symmetricLift-Off/Airloads 3 +3.6 g +3.6 g +4.1 g Diagonal lateral accelerationMECO +0.2 g 0 g +6.8gIntegrationIntegration 1 0 g 0 g +1 g Corner supports, in Integration StandIntegration 2 +1 g 0 g 0 g Corner supports, rotated 90 deg in Int StandIntegration 3 0 g 0 g -1 g Corner supports, upside down in Int StandIntegration 4 0 g 0 g -1 g 3-pt mid-side support, in Int StandIntegration 5 +1 g 0 g 0 g 3-pt mid-side support, rotated 90 deg in Int StandThermalCold Survival Soak -20C TKR, Grid, CAL -40C ACD Cold survival soak. Temp's imposed on

-60C Radiators structural modelHot Survival Soak +30C TKR, CAL, Grid +TBD C ACD Hot survival soak. Temp's imposed on

+20C Radiators structural modelThermal Transient +/- 3C/95 min period Thermal stability of LAT

LAT Structural Analysis Load CasesLAT Structural Analysis Load Cases


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Modal Analysis ResultsModal Analysis Results

• 10 modes below 75 Hz

– 1 significant LAT modes

– Multiple ACD panel, BEA vibration modes

– Multiple Radiator modes and mode combinations

• LAT drumhead mode

– 65.9 Hz at 2679 kg estimate

– 63 Hz at 3000 kg allocation

First 10 LAT ModesFirst 10 LAT Modes

LAT Drumhead ModeLAT Drumhead Mode

# Freq. Effective Mass Fraction Mode Description

1 56.4 9.4% UX, 5.4% UY ACD lateral mode2 58.8 1% UZ ACD mode3 60.6 6.6% UX, 9.8% UY LAT lateral mode at 45 degrees4 62.3 0.1% UY -Y side Radiator out-of-plane mode5 64.1 .16% UY +Y side Radiator out-of-plane mode6 65.9 42% UZ, 26% RX, 26% RY LAT drumhead mode7 67.2 0.1% RZ ACD anti-symmetric mode8 67.4 0.6% RX -Y side Radiator asymmetric mode9 68.7 0.2% UY +Y side Radiator asymmetric mode

10 73.8 1% UX, 3% RY X-axis LAT rocking mode

Parameter Req Design Margin Comply

LAT natural frequency > 50 Hz 56.4 Hz 6.4 Hz Y


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Deflections Due to Launch LoadsDeflections Due to Launch Loads

• Grid Deflection

– 6.8 g thrust load at MECO produces maximum Grid bowing

– Grid deflections• -0.41 mm at the center of the Grid• -0.09 mm at corner of the Grid

LAT Deflected Shape PlotLAT Deflected Shape Plot


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003TKR Interface Load RecoveryTKR Interface Load Recovery

• TKR Flexure joint

– Flexures isolate the carbon-fiber TKR structure from thermal strains of the Grid

– All flexure normals point to the center of a TKR module

– The 8 flexures are not a kinematic mount

• TKR Flexure force recovery

– Nodal forces are retrieved by isolating nodal forces at the TKR Flexure beam elements

– All forces are expressed in local cylindrical coordinates, with the module centerline the z axis

– Shear forces in theta-increasingdirection have the same sign. Shear forces sum to zero.

– Design limit loads are the maximaof the TKR module loads

• Limit loads identified for peakcompressive, tensile, and shear load

• Peak loads all occur in corner bays

TKR-Grid Flexures Design Accept Qual Unit

Launch EventLift-Off/

TransonicMECO

Mid-Side FlexuresShear 2266 2061 2266 2832.5 NTension/Compress. 391 291 391 489 N

Corner FlexuresShear 1,003 80 1,003 1,254 NTension/Compress. 1,277 1,193 1,277 1,596 N

Source (2) (4)

Flexure Limit LoadsFlexure Limit LoadsDelta PDR Analysis ModelDelta PDR Analysis Model



GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003CAL Interface Load RecoveryCAL Interface Load Recovery

• CAL-Grid tab joint

– 1152 bolts (72 per CAL module)

– Joint allows CAL bottom plate to stiffen LAT by closing out bottom side of Grid

• Load recovery

– Interface loads are backed out from the FEA model by resolving nodal forces at the interface into shear and normal loads at the bolt locations

– New NASTRAN model will allow these interface loads to be pulled directly from beam elements forces and moments

Tab Limit LoadsTab Limit LoadsDelta PDR Analysis Model Delta PDR Analysis Model


CAL Design Load Cases Acceptance Test Qualification TestTabs LC1 LC2 LC3 LC1 LC2 LC3 LC1 LC2 LC3 Unit Comments

F(x) 4373 1140 -3302 4373 1140 -3302 5467 1424 -4128 N Across tab in plane of plateF(y) 206 2994 1414 206 2994 1414 258 3742 1767 N Along tabF(z) -195 -11 654 -195 -11 654 -244 -14 817 N Out of plane of plateM(x) 1.39 -0.05 -6.09 1.39 -0.05 -6.09 1.74 -0.06 -7.61 N-m Around x-axisM(y) 0.45 -1.28 0.22 0.45 -1.28 0.22 0.56 -1.60 0.27 N-m Around y-axisM(z) 20.98 4.58 -14.86 20.98 4.58 -14.86 26.22 5.73 -18.57 N-m Around z-axisSource (6) (6) (6)Scale 1 1 1 1.25 1.25 1.25Notes: Interface loads are for CAL tab thickness of 7 mm


GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003ACD Interface Load RecoveryACD Interface Load Recovery

• ACD Base Electronics Assembly (BEA) to Grid Joint

– Bolted connection at 4 corners of BEA carry z-direction (thrust) loads only

– Bolted and pinned connections at the center of each of the 4 sides

• Interface load recovery

– Interface loads evaluated by retrieving nodal forces at rigid extension from Grid to BEA

– Loads shown are the maximum of predicts from ACD subsystem and LAT level analysis

ACD-Grid Mount Design Accept. PFQ Unit CommentCorner Mounts

Shear 0 0 0 N RSS of X, Y max shearTens/Compression 1787 1787 2234 N Parallel to LAT Z-axis

Mid-Side MountsShear 4402 4402 5503 N RSS of X, Z shears in plane of Grid wallTens/Compression 2223 2223 2779 N Normal to Grid wall

Source

ACD Limit LoadsACD Limit LoadsDelta PDR Analysis Model Delta PDR Analysis Model



GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Electronics Interface Load RecoveryElectronics Interface Load Recovery

• Electronics Box to CAL Joint

– Rigid stand-offs carry z-direction (thrust) loads, and lateral loads and moments

• Interface load/deflection recovery

– Loads shown are based on trade study analysis of Electronics box loads through stand-off

– CDR model will be used to update limit loads for this joint

E-Box Stand-Off Design Accept. Qual UnitTension 3,750 3,750 4,688 NCompression 2,625 2,625 3,281 NShear 1,288 1,288 1,609 NBending Moment 19.3 19.3 24.1 N-m

Electronic Box Limit LoadsElectronic Box Limit LoadsDelta PDR Analysis Model Delta PDR Analysis Model



GLAST LAT Project

Mechanical Design Integration Peer Review, March 2003Summary and Further WorkSummary and Further Work

• Summary

– Subsystem structural models have been updated to reflect Peer Review designs

– First look at mode shapes and frequency show that the LAT has margin with respect to its frequency requirement

– Structural model re-work is still in process

• Further Work

– Verify subsystem model integration

– Complete all load cases with LAT CDR model

– Update subsystem interface loads, based on CDR model

– Deliver model to GLAST PO for next CLA cycle

– Incorporate acoustic analysis results into limit load analyses

– Revise “LAT Environmental Specification” with these results

– Start pre-test analysis runs• Dynamic analyses to size accelerometers• STE structural analyses

LAT-PR-01278 Section 33-1 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003...

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Transcript of LAT-PR-01278 Section 33-1 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003...