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MODULE EJECTOR ASSEMBLYFEA STRUCTURAL& WEARANALYSIS
D . B L A N C H E T
3 / 7 / 2 0 1 3
3 B A S S O C I A T E S
ASSUMPTIONS:
Material Stainless Steel – 316 alloy yield strength = 42,000 psi
Module weight = 3.6 lbs
Loading cases :
§ 20G half sine shock 11msec applied in the module extraction direction§ For shock assume no retention force at the connector – worst case§ Random vibration loads are negligible.§ Extraction load = 15 lbs per lever.
Margin of safety (M.O.S.) = (yield strength/applied stress) – 1.0
Solidworks Advanced Professional FEA Simulation
SIMPLIFIED MODULE ….STRUCTURAL MODEL
Total Module Weight = 3.6 lbs
Assume no connectorRetention at this edge
(Worst case)
Guide rails
Shock pulsedirection
Flat head chassis retention screw 2 places
ExtractionLevers
Provide noStructuralsupport
FEA MODEL – MESHED , HANDLE DETAIL
Shockpulse
MAXIMUM BENDING STRESS UNDER 20G SHOCK PULSE
Max stress = 709 psi M.O.S. = (42000/709) – 1.0 = 58
Module to ChassisRetention screw
location
AMPLIFIED DISTORTION PLOTS – 3000X
20G half sine 11msec shock pulse load case
Stress 709 psi max Displacement << .001 inches
chassiswallfixed
chassiswallfixed
Extractiondirection
LEVER EXTRACTION LOADING MODEL
Determine the stress in the handle during module extraction
AppliedForce
~ 10 lbResultantExtraction
Load~ 50 lb or
100 lb per module
STRESS CONTOUR VIEWS – HANDLE SHOWN DEFORMED @100X
.0025
Maximum bending stress= 10,000 psiM.O.S. = 3.1
F = 10 lbs
Maxdeflection
A Very Effective design
CONCLUSIONS:BASELINE EXTRACTOR ASSEMBLY IN STAINLESS STEEL
The extractor body has a margin of safety of 58 ; a robust design
The handle when loaded to provide 50 lbs of extraction force (100 lb total) has a margin of safety of 3.1
9
APPENDIX ALEVER JAWS CONTACT WEAR ANALYSIS
S T A I N L E S S S T E E L V S . A L U M I N U M W E A R E S T I M A T E S
GOALS & LIMITATIONS
Use Archard’s wear Law supported by FEA to estimate the relative wear of an aluminum vs. stainless steel lever.
Metal wear is a complex phenomena which is still primarily measured by laboratory testing.
Recent advances in FEA are using complex non-linear modeling to estimate material removal rates due to contact pressure and material/plating harnesses.
This study uses simple linear FEA to calculate one key variable in Archard’s Law.
ARCHARD’S WEAR LAW CIRCA 1930
W = K/H * S * P§ W = metal removal cubic inches§ K = a constant for metal categories§ H = hardness ( Rockwell or Brinell scale)§ S = sliding distance§ P = contact pressure
Sanity check§ More pressure > more wear§ Harder target material > less wear§ Assumes target material is softer than the contacting material
Use linear FEA to calculate the local contact pressure P , in p.s.i.
Testing has verified this Law for first order calculations.
FEA CONTACT MODEL
Infinitely hard“wall” material
fixed
High density mesh with sliding contact elements
Applied Load
20 lbs
Fixedrotation
Target material
FEA RESULTS , STRESS PLOTS
Stress is not significantly different not a primary variable
Steel lever max contact stress = 55,000 psi
Aluminum lever max contact stress = 50,000 psi
CALCULATE A WEAR “FIGURE OF MERIT” FOR THIS DESIGN
F.O.M. ---- Figure of Merit , lower value indicates less wear potential
LeverMaterial
K HRockwell B
S Pp.s.i.(FEA)
WF.O.M.
316Stainless
Steel
1 95 1 55,000 579
Aluminum6061-T6
1 60 1 50,000 833
WEAR PREDICTION CONCLUSION
Using Archard’s Wear Law a steel lever is predicted to have less potential for wear.
Aluminum will wear at a rate (833/579) = 144 % faster.