Title: TSU F'E ANALYSIS
1TSU F.E ANALYSIS
2Ojective
- Dynamic Response Calculation
- Temperature Distribution
- LOS Retention due to Temperatures
- Design Recommendations
3Model Description
- TSU Casting and Cover
- Optical Bench
- Hood
- PCBs
- Mirror, Flexures, Optical Elements, Masses
- Bolts and Thermal Resistances
4The Optical Module and Mirror Assembly
5Loads 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
6Structural Analysis - Boundary Conditions
7Thermal 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
8Materials
- 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
9Results
- 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
10 Second Natural Frequency - 126 Hz
11 Seventh Natural Frequency - 202 Hz
12The Maximum Accelerations during 15g/11msec Shock
in X direction
13The Maximum Accelerations during 15g/11msec Shock
in Y direction
14The Maximum Accelerations during 15g/11msec Shock
in Z direction
15The Accelerations on several components during Z
Shock
16Maximum Accelerations and Displacements on PCBs
- Z Shock
17Checking 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
18The displacements on Supply while subjected to
24g static load - Z
19The Maximum Stresses during 24g static envelope -
X direction
20The Maximum Stresses during 24g static envelope -
Y direction
21Principal Stresses on the Mirror, 24g static
envelope, Y direction
22The Maximum Stresses during 24g static envelope -
Z direction
23Von Mises Stresses on the Optical Module, 24g
static, Z direction
24Von Mises Stresses on the Al Flexure, 24g static
envelope, Z direction
25Design 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.
26The new bonding configuration
27The Maximum Stresses during 17g static envelope -
Z direction
28Tensile Stresses on the Adhesive, 17g static
envelope, Z direction
29Random Endurance Vibration X
30Random Endurance Vibration Y
31Random Endurance Vibration Z
32The RMS Accelerations during Random Vibration, X
direction
33The RMS Stresses during Random Vibration - X
direction
34The RMS Accelerations during Random Vibration, Y
direction
35The RMS Stresses during Random Vibration - Y
direction
36The RMS Accelerations during Random Vibration, Z
direction
37RMS Accelerations Displacements on PCBs (1?),
Z (C/Ccr2)
38The RMS Stresses during Random Vibration - Z
direction
39Checking 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
40Thermal Analysis - 52 C AmbientMain parts
temperature distribution
41The inside Temperatures
- PCB area 69.5 C
- R area 60.6 C
- Hood inside air 61.2 C
42L.O.S Retention - operation in -30 ?C (CRT
contact angle 38?)
43L.O.S Retention - operation in 52 ?C (CRT
contact angle 38?)
44Temperature distribution on the optical Module
45Temperature distribution on the CPU
46Discussion 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.
47Discussion 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.
48Discussion 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.
49Discussion 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.
50Discussion 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.