1 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts B. C. Bigelow, UM Physics 3/24/05

2 Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts Motivations: 1.Provide a common mount design for Vis and IR detectors 2.Minimize detector package SS thermal stresses 3.Minimize detector package SS temperature gradients 4.Accommodate various detector package materials (Invar, TZM) 5.Accommodate various FPA baseplate materials (TZM, SiC, ?) 6.Accommodate local detector PCBs, connectors, heaters, etc. 7.Minimize weight, maximize first resonance

3 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts Detector space frame! – but fabrication unfriendly…

4 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts A fabrication-friendly version…

5 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts Fabrication options for hexapod: 1.Fabrication method may depend on hexapod material choice 2.Powder metallurgy methods (HIP, laser sintering) 3.Abrasive water-jet cutting 4.Laser cutting 5.Plunging and/or wire EDM 6.Stress-relieve rough blanks prior to cutting 7.Polish blanks flat and parallel prior to cutting 8.Final grind/polish mounting pads to spec. after cutting 9.Other?

6 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts

7 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts Arbitrary mount height of 12mm – can be lower

8 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts

9 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts

10 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts

11 3/24/05Bruce C. Bigelow -- UM Physics Finite Element Analyses Quantify performance via FE analyses : 1.Hexapod flexures are 1mm wide x 3mm high (all cases) 2.Hexapod material is TZM (Invar another option) 3.Static analyses: 100g deflections and stresses 4.Dynamic analyses: first 10 frequencies and mode shapes 5.Steady-state thermal: stress for -150K temp excursions 6.Steady-state thermal: heat flow and temperature gradients 7.Summary follows individual results

12 3/24/05Bruce C. Bigelow -- UM Physics Focal Plane Material Properties Material Properties TZM (Moly) Invar 36SiC (CVD) E (GPa) Yield (MPa) Density (kg/m^3) CTE (PPM/K) K (W/mK) Room temp. material properties

13 3/24/05Bruce C. Bigelow -- UM Physics FEA - static Static FEA: 1.100g accelerations, Gx, Gy, Gz 2.Det. package base models only, no AlN, MCT, epoxy, etc. 3.Two material combinations – Invar/TZM, and TZM/TZM 4.Simplified model of hexapod mount (no “pads”) 5.Max deflections: microns 6.Max stresses: MPa (Invar/TZM) Invar yield = 300 MPa TZM yield = 860 Mpa 7.Low stress in package material - max. 20 Mpa (point load)

14 3/24/05Bruce C. Bigelow -- UM Physics FEA - static Gz, Z-axis deflections – 1.4 microns max Deflections in meters, 1.4 microns max.

15 3/24/05Bruce C. Bigelow -- UM Physics FEA - static Gz, Z-axis deflections – 1.4 microns max Stress in Pa, 26 MPa max., (point loads)

16 3/24/05Bruce C. Bigelow -- UM Physics FEA - dynamic Dynamic FEA: 1.Det. package base models only, no AlN, Si, MCT, epoxy, etc. 2.Two material combinations – Invar/TZM, and TZM/TZM 3.Simplified model of TZM hexapod mount 4.First resonances: TZM/invar – 3000 Hz TZM/TZM – 3053 Hz

17 3/24/05Bruce C. Bigelow -- UM Physics FEA - dynamic Gz, Z-axis deflections – 1.4 microns max

18 3/24/05Bruce C. Bigelow -- UM Physics FEA – steady state thermal Steady-state thermal stress: 1.Minus 150 K temperature excursion 2.Baseplate, hexapod mount, and package base 3.Four material combinations for baseplate and package: TZM/Invar, TZM/TZM, SiC/TZM, SiC/Invar 4.Simplified model of hexapod mount (no “pads”) 5.Deflections: 6.9 – 8.7 microns (TZM/TZM, TZM/Invar) 6.Deflections: microns (SiC/Invar, SiC/TZM) 7.Pkg stresses: 2.3 Mpa (TZM/Invar) 8.Pkg stresses: Mpa (SiC/TZM, SiC/Invar)

19 3/24/05Bruce C. Bigelow -- UM Physics FEA – steady state thermal Gz, Z-axis deflections – 1.4 microns max Elements

20 3/24/05Bruce C. Bigelow -- UM Physics FEA – steady state thermal Stress in Pa, 14.8 MPa max. (point loads)

21 3/24/05Bruce C. Bigelow -- UM Physics FEA – steady state thermal Steady-state heat flow: 1.Baseplate, hexapod mount, and package base mW heat load imposed on top surface of package 3.Baseplate – back side sunk to a cold source at 140 K 4.Four material combinations for baseplate and package: TZM/Invar, TZM/TZM, SiC/TZM, SiC/Invar 5.Simplified model of TZM hexapod mount (no “pads”) 6.Max. temp variation: 0.56 K (TZM/Invar) 7.Min. temp variation: 0.05 K (SiC/TZM and TZM/TZM) 8.Min final temp: K (SiC/TZM) 9.Max final temp: K (TZM/Invar)

22 3/24/05Bruce C. Bigelow -- UM Physics FEA – steady state thermal Boundary cond.

23 3/24/05Bruce C. Bigelow -- UM Physics FEA – steady state thermal Temp variations (K) – SiC/TZM

24 3/24/05Bruce C. Bigelow -- UM Physics FEA summary MaterialsPkg, 100g, X,Y,ZFn-150Khexpkg D T TfTf BasePkguxuyuz s,MPa Hz uz s, Mpa s, MPa KK TZMInv TZM SiCInv SiCTZM deflections, u, in microns

25 3/24/05Bruce C. Bigelow -- UM Physics Detector mount taxonomy Yale flexLBL flex UM flexUM hexapod

26 3/24/05Bruce C. Bigelow -- UM Physics Detector mount comparison Pkg thermal stress, -150K Pkg temp gradient First resonance Design:MPaKHz Yale flex LBL flex UM flex UM hexapod

27 3/24/05Bruce C. Bigelow -- UM Physics Hexapod Detector Mounts Conclusions: 1.Hexapod mount kinematically connects detectors to focal plane: Low thermal stress for -150 K temperature change Large conduction cross-section minimizes thermal gradients Common mount design works for both NIR and VIS detector packages Very low thermal stresses in base plate, mount, and packages 2.Hexapod provides “optimal” support for detectors: Minimum mass, maximum stiffness solution Very high first resonance – 3000 Hz or higher 3.Hexapod mount is readily fabricable by standard methods 4.Hexapod performance demonstrated via FE analysis