sheet metal large cover design trade-off study show the advantages of a deep drawn domed shape

1. STIFFNESS AND STRENGTH OF
FORMED DEEP DRAWN
SHEET METAL
FEA trade study
3/25/2016
Don Blanchet
3B Associates
339-234-3544
NRCM hydraulic presses

2. GOALS – FEA simulations
 Examine various designs for a large
sheet metal cover used for a flight
worthy rugged computer.
 Requirements - analyses
– Shock and vibration natural frequency
– weight
– Deflection and stress under internal
pressurization of 1.0 psi

3. Design parameters
 2024 aluminum .093 thick
 36 x 36 inches
 Edge depth - 4.0 inches
 Center depth – 6.0 inches

4. Formed deep drawn

5. Formed deep drawn

6. Mode shape – Fn = 148hz

7. Max Deflection under
internal pressure

8. Maximum stress

9. Radiused edges

10. Flat welded

11. Welded ribs

12. Summary of results
Design
Thin shell
0.1 inch
Natural
Frequency
hz
Weight
lbs
Pressurized
Deflection
inches
Maximum
Stress
psi
flat
welded
31 22.0 0.79 13,740
Deep drawn
Design #1
148 19.5 0.03 3,100
Flat
Radiused
edges
26 21.6 0.38 8,420
welded
ribs
44 22.6 0.40 14,960

13. Study conclusions
 Deep drawn design
– Highest natural frequency best in shock
and vibration environments
– Lightest weight
– Smallest deflection under pressure
– Lowest stress
 Disadvantage – high tooling cost