LAT-PR Section 33-1 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Mechanical Design Integration Peer Review, March Structural Design and Analysis Mechanical Design Integration Peer Review, March Structural Design and Analysis 25 March 2003 Martin

LAT-PR Section 33-2 GLAST LAT ProjectMechanical Design Integration Peer Review, March 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

LAT-PR Section 33-3 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT Structural Schematic Diagram

LAT-PR Section 33-4 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Internal 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

LAT-PR Section 33-5 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT Structural Interface Design Changes Since Delta-PDR Increased Radiator area to 2.78 m 2 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

LAT-PR Section 33-6 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Trade 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

LAT-PR Section 33-7 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Current 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 Model

LAT-PR Section 33-8 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Driving Structural Requirements

LAT-PR Section 33-9 GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 LAT 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 Estimates Source: LAT-TD “LAT Mass Status Report, Mass Estimates for Mar 2003,” 7 Mar 2003 LAT Static-Equivalent Design Accelerations Source: LAT-SS “LAT Environmental Specification,” March 2003 LAT F.E.A. Model Metrics

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Structural 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

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Structural Load Case Definitions LAT Structural Analysis Load Cases

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Modal 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 Modes LAT Drumhead Mode

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Deflections Due to Launch Loads Grid Deflection –6.8 g thrust load at MECO produces maximum Grid bowing –Grid deflections mm at the center of the Grid mm at corner of the Grid LAT Deflected Shape Plot

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 TKR 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-increasing direction have the same sign. Shear forces sum to zero. –Design limit loads are the maxima of the TKR module loads Limit loads identified for peak compressive, tensile, and shear load Peak loads all occur in corner bays Flexure Limit Loads Delta PDR Analysis Model Source: LAT-SS “LAT Environmental Specification,” March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 CAL 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 Loads Delta PDR Analysis Model Source: LAT-SS “LAT Environmental Specification,” March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 ACD 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 Limit Loads Delta PDR Analysis Model Source: LAT-SS “LAT Environmental Specification,” March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Electronics 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 Electronic Box Limit Loads Delta PDR Analysis Model Source: LAT-SS “LAT Environmental Specification,” March 2003

LAT-PR Section GLAST LAT ProjectMechanical Design Integration Peer Review, March 2003 Summary 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