RACK 2 – 8 PU STOWAGE DRAWERSTRUCTURAL ANALYSIS SUMMARYMarshall Philips(281) 333-75142• Finite Element Model (FEM) Development and Analysis• FEM Description• Factors of Safety• Margin of Safety Summary• Model Check• Dynamic Analysis• Analysis Cases• Load GenerationOVERVIEW3OVERVIEW (CONT)• Crew Induced Load Analysis• Depressurization / Repressurization Analysis• Fatigue Analysis• Fracture Screening– Containment– Fail-Safe• Conclusion• Open Work4Factor of Safety SummaryUntested Factors of Safety were used for nominal condition•FSult= 2.0•FSyld= 1.25For Fail-Safe:• FS = 1.05Minimum Margin of Safety Summary0.5950 lbsLatch handleCrew InducedLarge0.020 psi (pressure load)Top PanelRepress / Depress0.81125 lbsFront PanelCrew Induced0.36Tension: 2280 lbsShear: 580 lbsFastener(left panel to front panel)Landing / Fail-Safe0.35Tension: 2183 lbsShear: 390 lbsFastener(left panel to front panel)LandingFastener(left panel to front panel)Fastener (right panel to front panel)Location0.29Tension: 2353 lbsShear: 689 lbsLaunch / Fail-Safe0.10Tension: 2226 lbsShear: 696 lbsLaunchMinimum Margin (Ult.)Applied LoadLoadCase6FEM DESCRIPTION• The finite element model of the Rack 2 – 8PU Stowage Drawer was built using IDEAS ms7 and analyzed with MSC/NASTRAN.• The stowed components are represented by a single concentrated mass located at the c.g. of the drawer and connected to the six walls of the drawer using rigid elements and springs. The spring constant for the springs is chosen to approximate the foam packing.78PU Stowage Drawer – Front Isometric View88PU Stowage Drawer – Rear Isometric View9FEM WEIGHT SUMMARY• 8PU stowage drawer weighs (empty): 21.45 lbs• Slide guide assembly: 8.40 lbs each (rack mounted hardware)• Stowage contents weigh: 67.8 lbs• FEM analysis weight: 89.25 lbs (drawer + contents)10MODEL CHECKS• Rigid body modes, unit enforced displacements, and 1-g reaction load checks were performed on the model• Model check results indicate no unintentional constraints or ill-conditioning within the model11DYNAMIC ANALYSIS• Drawer with slide guide assemblies FEM was used for normal mode analysis. The slide guides are constrained at the rack interface attachments • Normal mode analysis was performed using NASTRAN and system frequencies and mode shapes recovered for the empty drawer.• The system mode frequencies were found to be 154 Hz, 428 Hz, and 274 Hz for X, Y, and Z-directions, respectively12Analysis Cases• Launch Analysis– Nominal (two handles and two rack bolts intact)– Fail-safe (one rack bolt failed)– Fail-safe (one handle failed)• Landing Analysis– Nominal (two handles intact / no rack bolts)– Fail-safe (one handle failed)13Launch Analysis• Random vibration loads are calculated from the dynamic response of the empty drawer.• Random vibration loads are combined with quasi-static launch loads and applied to the drawer structure.• Random vibration loads are not applied to the contents of the drawer because the foam packing isolates the stowed components from high frequency vibrations.14Landing Analysis• The purpose of the landing analysis is to see if the drawer can survive a landing without the two rack bolts installed.• There are no random vibration loads for the landing analysis, quasi-static landing loads from SSP 57000 Rev. E are applied.15ANALYSIS LOADS• FEM analysis launch loads are a generated by combining quasi-static and random vibration loads • Launch loads are combined with random vibration loads, one direction at a time, to generate the FEM analysis loads.• Quasi-static load factors are obtained from the SSP 57000 rev. ETable 1. Payload ISPR Mounting Equipment Load FactorsEvent Nx (g) Ny (g) Nz (g)Liftoff +/- 7.7 +/- 11.6 +/- 9.9Landing +/- 5.4 +/- 7.7 +/- 8.8SSP 57000, Rev. D, Table 3.1.1.3-416LOAD GENERATION• Random vibration load factors are generated using Mile’s equation in conjunction with the modal mass participation method. Details of the approach are delineated in section 4.1.5, SSP52005B• The PSD values are obtained from SSP 57000, Rev. ERandom Vibration Criteria for ISPR Post-Mounted Equipment Weighing 100 Pounds or Less in the MPLMFrequency (Hz) PSD (g2/Hz) or Slope(dB/octave)20 0.005 g2/Hz20 - 70 +5 dB/octave70-200 0.04 g2/Hz200 - 2000 -3.9 dB/octave2000 0.002 g2/HzComposite 4.4 grmsSSP 57000, Rev. E, Table 3.1.1.3-217LOAD GENERATION (continued) • Random Vibration Load Factors (RVLFn) computation using Miles’ Equation.Where,fn= Normal mode frequency (n = x, y, z)Q = Amplification factor (10)PSDn= Random vibration environment Power Spectral Density at fn(n = x, y, z)nnn PSD*f*Q*2*3RVLFπ=18LOAD GENERATION (continued) • Quasi-static and random load combination is based on the following criteria SSP 52005B 4.1.2-1Load Combination Criteria for Space Station Components19LOAD GENERATION (continued)• Lift-off quasi-static load factors are combined with random vibration load factors in one direction at a time to form 24 load cases. The combined load factors are as followsLoad CaseQuasi-Static Load Factor Random Vibration Load Factor Combined Load FactorXY Z XY Z XY ZLift-off1 7.7 11.6 9.9 11.26 14.35 11.60 9.902 7.7 11.6 -9.9 11.26 14.35 11.60 -9.903 7.7 -11.6 9.9 11.26 14.35 -11.60 9.904 7.7 -11.6 -9.9 11.26 14.35 -11.60 -9.905 -7.7 11.6 9.9 -11.26 -13.04 11.60 9.906 -7.7 11.6 -9.9 -11.26 -13.04 11.60 -9.907 -7.7 -11.6 9.9 -11.26 -13.04 -11.60 9.908 -7.7 -11.6 -9.9 -11.26 -13.04 -11.60 -9.90Lift-off1 7.7 11.6 9.9 10.57 7.70 15.70 9.902 7.7 11.6 -9.9 10.57 7.70 15.70 -9.903 7.7 -11.6 9.9 -10.57 7.70 -15.70 9.904 7.7 -11.6 -9.9 -10.57 7.70 -15.70 -9.905 -7.7 11.6 9.9 10.57 -7.70 15.70 9.906 -7.7 11.6 -9.9 10.57 -7.70 15.70 -9.907 -7.7 -11.6 9.9 -10.57 -7.70 -15.70 9.908 -7.7 -11.6 -9.9 -10.57 -7.70 -15.70 -9.90Lift-off1 7.7 11.6 9.9 10.35 7.70 11.60 14.322 7.7 11.6 -9.9 -10.35 7.70 11.60 -14.323 7.7 -11.6 9.9 10.35 7.70 -11.60 14.324 7.7 -11.6 -9.9 -10.35 7.70 -11.60 -14.325 -7.7 11.6 9.9 10.35 -7.70 11.60 14.326 -7.7 11.6 -9.9 -10.35 -7.70 11.60 -14.327 -7.7 -11.6 9.9 10.35 -7.70 -11.60 14.328 -7.7 -11.6 -9.9 -10.35 -7.70 -11.60 -14.3220Stress AnalysisMargins of safety were calculated with the following equations:Where: Fult= Ultimate AllowableFyld= Yield allowable 1σ*FSFMSpultult−= 1σ*FSFMSvmyldyld−=21CREW INDUCED LOAD• A 125 lbf kick load was applied to the front panel, per 57000 rev. D, Table 3.1.13-1• 50 lbs operational load applied to