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Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas

Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas Elevation Membrane Verification PM#04- 17-18 May 2006 Dated November 18 h , 2005. FEM MODEL. ► Membrane: element type SHELL63 thickness 0.005 m ► Fictitious beams: element type BEAM4

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Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas

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  1. Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas • Elevation Membrane Verification • PM#04- 17-18 May 2006 • Dated November 18h, 2005

  2. FEM MODEL ►Membrane: element type SHELL63 thickness 0.005 m ►Fictitious beams: element type BEAM4 Area 0.001 m2 Ixx=Iyy=Izz 1e-5 m4 thickness 0.001 m ►Material model: linear, isotropic Elastic modulus 206 GPa Poisson ratio 0.3 ►Constraints: ux, uy, uz, rotx, roty, rotz along the external perimeter of the membrane

  3. Loads have been assessed from the antenna global model and they have been applied at the central node of the fictitious beams dial

  4. STATIC VERIFICATION 1gx σVM,max=141MPa 1gy σVM,max=42MPa 1gz σVM,max=43MPa

  5. STATIC VERIFICATION ΔT=20°CσVM,max=54.7 MPa Ux=1mm σVM,max=401 MPa

  6. BUCKLING VERIFICATION • Critical Load • Fcr=5.70E6 N • Worst load condition • 4g vertical shock acceleration • Fz~0.45E6 N • Safety factor ~12.5

  7. FATIGUE VERIFICATION • Thermic stress fatigue verification • Assumptions (in advantage of safety) • Daily ΔT=±20°C • cycle no =365×30~1.1e4 • Loads are reduced to Fx component • Biaxial stress • Principal stress in radial and circumferential directions • Verification performed as unidirectional by imposing σa=σ1,max , R=0

  8. FATIGUE VERIFICATION Radial stress σr,max=60 MPa Circumferential stress σc,max=18 MPa Shear stress r,c~0 MPa

  9. FATIGUE VERIFICATION R=-1 σL UTS=680 MPa σA,-1=0.35×UTS=240 MPa σkN=const n=1.1e4 σa=60 MPa σL=490 MPa σ=490/60~8

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