ejector stress and wear analysis
TRANSCRIPT
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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
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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
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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
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FEA MODEL – MESHED , HANDLE DETAIL
Shockpulse
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MAXIMUM BENDING STRESS UNDER 20G SHOCK PULSE
Max stress = 709 psi M.O.S. = (42000/709) – 1.0 = 58
Module to ChassisRetention screw
location
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AMPLIFIED DISTORTION PLOTS – 3000X
20G half sine 11msec shock pulse load case
Stress 709 psi max Displacement << .001 inches
chassiswallfixed
chassiswallfixed
Extractiondirection
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LEVER EXTRACTION LOADING MODEL
Determine the stress in the handle during module extraction
AppliedForce
~ 10 lbResultantExtraction
Load~ 50 lb or
100 lb per module
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STRESS CONTOUR VIEWS – HANDLE SHOWN DEFORMED @100X
.0025
Maximum bending stress= 10,000 psiM.O.S. = 3.1
F = 10 lbs
Maxdeflection
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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
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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
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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.
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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.
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FEA CONTACT MODEL
Infinitely hard“wall” material
fixed
High density mesh with sliding contact elements
Applied Load
20 lbs
Fixedrotation
Target material
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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
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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
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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.