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TSU F.E ANALYSIS

TSU F.E ANALYSIS. YAIR SOFFAIR. Ojective. Dynamic Response Calculation Temperature Distribution LOS Retention due to Temperatures Design Recommendations. Model Description. TSU Casting and Cover Optical Bench Hood PCB’s Mirror, Flexures, Optical Elements, Masses

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TSU F.E ANALYSIS

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  1. TSU F.E ANALYSIS YAIR SOFFAIR

  2. Ojective • Dynamic Response Calculation • Temperature Distribution • LOS Retention due to Temperatures • Design Recommendations

  3. Model Description • TSU Casting and Cover • Optical Bench • Hood • PCB’s • Mirror, Flexures, Optical Elements, Masses • Bolts and Thermal Resistances

  4. The Optical Module and Mirror Assembly

  5. Loads and Runs • Operating (68W) in 52 C Ambient • Natural Frequencies • 15 g/11msec Shock on 3 Directions • 24 g Static Envelope • Random Vibrations on 3 Directions

  6. Structural Analysis - Boundary Conditions

  7. Thermal Analysis Boundary Conditions • The Ambient Temperature outside was set to 52 C • Convection Coefficients were calculculated and entered • The Temperatures inside were calculated during the Analysis

  8. Materials • Casting - Al 356Mil-A-21180 Class 11 • Flexure -Al 7075 T 7351 • Flexure - 17-4 PH H 1025 Steel • Mirror - RG 715 • Adhesive - Ablebond 724 - 14C • Lenses - SFL 6 • PCB’s - Polymide+Copper layers

  9. Results • Natural Frequencies • 118 Hz - Supply card Bending • 126 Hz - Optical Module Bending • 136 Hz - Video card Bending • 155 Hz - CPU card Bending • 166 Hz - Supply card Bending • 189 Hz - Video card Bending • 202 Hz - TSU Twisting+legs&CPU Bending • 204 Hz - CPU Bending • 227 Hz - Optical Module & Flexures Bending

  10. Second Natural Frequency - 126 Hz

  11. Seventh Natural Frequency - 202 Hz

  12. The Maximum Accelerations during 15g/11msec Shock in X direction

  13. The Maximum Accelerations during 15g/11msec Shock in Y direction

  14. The Maximum Accelerations during 15g/11msec Shock in Z direction

  15. The Accelerations on several components during Z Shock

  16. Maximum Accelerations and Displacements on PCB’s - Z Shock

  17. Checking the PCB’s - Steinberg Criteria during Z Shock • The critical PCB is the SupplyPCB • The Displacement on the critical component is 0.53 mm • The allowed Displacement for such component according to Steinberg criteria is 1.41 mm

  18. The displacements on Supply while subjected to 24g static load - Z

  19. The Maximum Stresses during 24g static envelope - X direction

  20. The Maximum Stresses during 24g static envelope - Y direction

  21. Principal Stresses on the Mirror, 24g static envelope, Y direction

  22. The Maximum Stresses during 24g static envelope - Z direction

  23. Von Mises Stresses on the Optical Module, 24g static, Z direction

  24. Von Mises Stresses on the Al Flexure, 24g static envelope, Z direction

  25. Design Improvements • Adhesive thickness is increased to 0.35 mm. • Three flexures and two ribs were added to the Optical Module in order to increase the second natural frequency and reducethe gains. • The Mirror thickness was reduced from 13 mm to 11 mm.

  26. The new bonding configuration

  27. The Maximum Stresses during 17g static envelope - Z direction

  28. Tensile Stresses on the Adhesive, 17g static envelope, Z direction

  29. Random Endurance Vibration X

  30. Random Endurance Vibration Y

  31. Random Endurance Vibration Z

  32. The RMS Accelerations during Random Vibration, X direction

  33. The RMS Stresses during Random Vibration - X direction

  34. The RMS Accelerations during Random Vibration, Y direction

  35. The RMS Stresses during Random Vibration - Y direction

  36. The RMS Accelerations during Random Vibration, Z direction

  37. RMS Accelerations & Displacements on PCB’s (1), Z (C/Ccr=2%)

  38. The RMS Stresses during Random Vibration - Z direction

  39. Checking the PCB’s - Steinberg Criteria during Z Vibration • The critical PCB is the CPU • Total life time : 5.5 hours • M.S=2.74 • The PCB’s free edges must be captured and bonding of the critical components to the board is recommended

  40. Thermal Analysis - 52 C AmbientMain parts temperature distribution

  41. The inside Temperatures • PCB area : 69.5 C • R area : 60.6 C • Hood inside air : 61.2 C

  42. L.O.S Retention - operation in -30 C (CRT contact angle 38)

  43. L.O.S Retention - operation in 52 C (CRT contact angle 38)

  44. Temperature distribution on the optical Module

  45. Temperature distribution on the CPU

  46. Discussion and Recommendations • There is no stress problem. • The critical dynamic case is Z shock. • The critical parts are : Al Flexure, the Adhesive and the Mirror. • The critical PCB, Z shock : Supply. • M.S=2.66 • The critical PCB, Z vibration : CPU.

  47. Discussion and Recommendations • M.S=2.74 • free edges should be captured and bonding of the critical components to the board is recommended. • L.O.S Retention during operating in 52 C is very good in elevation even while adding the R error.

  48. Discussion and Recommendations • In azimuth, the error is strongly dependent on the contact angle between the CRT and the Optical Module. • In order to minimize this error, the contact angle is set to 40°. • L.O.S error during operation in -30°C is larger, but within the allowed tolerance.

  49. Discussion and Recommendations • significant improvement can be made by Temperature or electrical calibration. • The critical PCB’s : Video & Supply. • Gap filler (T-form 460) is added to the Video hot components in order to transfer heat to the H.S. • Gap filler is recommended to connect the PCB hot component to the Main Housing.

  50. Discussion and Recommendations • Sinusoidal scanning of the Optical modulealone (3 flexures) showed first natural frequency of 150 Hz. • Thermal experiment of the system operating at 52°C showed temperatures of 71°C on the CRT interface and mid wall.Analysis showed 69°C, 68°C respectively.

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