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MODULE EJECTOR ASSEMBLY FEA STRUCTURAL & WEAR ANALYSIS D. BLANCHET 3/7/2013 3B ASSOCIATES

Ejector stress and wear analysis

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Page 1: Ejector stress and wear analysis

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

Page 2: Ejector stress and wear analysis

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

Page 3: Ejector stress and wear analysis

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

Page 4: Ejector stress and wear analysis

FEA MODEL – MESHED , HANDLE DETAIL

Shockpulse

Page 5: Ejector stress and wear analysis

MAXIMUM BENDING STRESS UNDER 20G SHOCK PULSE

Max stress = 709 psi M.O.S. = (42000/709) – 1.0 = 58

Module to ChassisRetention screw

location

Page 6: Ejector stress and wear analysis

AMPLIFIED DISTORTION PLOTS – 3000X

20G half sine 11msec shock pulse load case

Stress 709 psi max Displacement << .001 inches

chassiswallfixed

chassiswallfixed

Extractiondirection

Page 7: Ejector stress and wear analysis

LEVER EXTRACTION LOADING MODEL

Determine the stress in the handle during module extraction

AppliedForce

~ 10 lbResultantExtraction

Load~ 50 lb or

100 lb per module

Page 8: Ejector stress and wear analysis

STRESS CONTOUR VIEWS – HANDLE SHOWN DEFORMED @100X

.0025

Maximum bending stress= 10,000 psiM.O.S. = 3.1

F = 10 lbs

Maxdeflection

Page 9: Ejector stress and wear analysis

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

Page 10: Ejector stress and wear analysis

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

Page 11: Ejector stress and wear analysis

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.

Page 12: Ejector stress and wear analysis

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.

Page 13: Ejector stress and wear analysis

FEA CONTACT MODEL

Infinitely hard“wall” material

fixed

High density mesh with sliding contact elements

Applied Load

20 lbs

Fixedrotation

Target material

Page 14: Ejector stress and wear analysis

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

Page 15: Ejector stress and wear analysis

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

Page 16: Ejector stress and wear analysis

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.