TSU F'E ANALYSIS

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TSU F.E ANALYSIS

• YAIR SOFFAIR

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Ojective

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

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Model Description

• TSU Casting and Cover
• Optical Bench
• Hood
• PCBs
• Mirror, Flexures, Optical Elements, Masses
• Bolts and Thermal Resistances

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The Optical Module and Mirror Assembly
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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

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Structural Analysis - Boundary Conditions
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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

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Materials

• Casting - Al 356 Mil-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
• PCBs - PolymideCopper layers

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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 TwistinglegsCPU Bending
• 204 Hz - CPU Bending
• 227 Hz - Optical Module Flexures Bending

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Second Natural Frequency - 126 Hz
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Seventh Natural Frequency - 202 Hz
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The Maximum Accelerations during 15g/11msec Shock
in X direction
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The Maximum Accelerations during 15g/11msec Shock
in Y direction
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The Maximum Accelerations during 15g/11msec Shock
in Z direction
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The Accelerations on several components during Z
Shock
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Maximum Accelerations and Displacements on PCBs
- Z Shock
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Checking the PCBs - Steinberg Criteria during Z
Shock

• The critical PCB is the Supply PCB
• The Displacement on the critical component is
  0.53 mm
• The allowed Displacement for such component
  according to Steinberg criteria is 1.41 mm

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The displacements on Supply while subjected to
24g static load - Z
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The Maximum Stresses during 24g static envelope -
X direction
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The Maximum Stresses during 24g static envelope -
Y direction
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Principal Stresses on the Mirror, 24g static
envelope, Y direction
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The Maximum Stresses during 24g static envelope -
Z direction
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Von Mises Stresses on the Optical Module, 24g
static, Z direction
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Von Mises Stresses on the Al Flexure, 24g static
envelope, Z direction
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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.

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The new bonding configuration
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The Maximum Stresses during 17g static envelope -
Z direction
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Tensile Stresses on the Adhesive, 17g static
envelope, Z direction
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Random Endurance Vibration X
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Random Endurance Vibration Y
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Random Endurance Vibration Z
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The RMS Accelerations during Random Vibration, X
direction
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The RMS Stresses during Random Vibration - X
direction
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The RMS Accelerations during Random Vibration, Y
direction
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The RMS Stresses during Random Vibration - Y
direction
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The RMS Accelerations during Random Vibration, Z
direction
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RMS Accelerations Displacements on PCBs (1?),
Z (C/Ccr2)
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The RMS Stresses during Random Vibration - Z
direction
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Checking the PCBs - Steinberg Criteria during Z
Vibration

• The critical PCB is the CPU
• Total life time 5.5 hours
• M.S2.74
• The PCBs free edges must be captured and bonding
  of the critical components to the board is
  recommended

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Thermal Analysis - 52 C AmbientMain parts
temperature distribution
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The inside Temperatures

• PCB area 69.5 C
• R area 60.6 C
• Hood inside air 61.2 C
  

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L.O.S Retention - operation in -30 ?C (CRT
contact angle 38?)
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L.O.S Retention - operation in 52 ?C (CRT
contact angle 38?)
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Temperature distribution on the optical Module
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Temperature distribution on the CPU
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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.S2.66
• The critical PCB, Z vibration CPU.

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Discussion and Recommendations

• M.S2.74
• 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.

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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 -30C is
  larger, but within the allowed tolerance.

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Discussion and Recommendations

• significant improvement can be made by
  Temperature or electrical calibration.
• The critical PCBs 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.

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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
  52C showed temperatures of 71C on the CRT
  interface and mid wall.Analysis showed 69C,
  68C respectively.