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

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.