Air Bearing Upgrade for Split-Hopkinson Pressure Bar Experiment

Transcript Air Bearing Upgrade for Split-Hopkinson Pressure Bar Experiment

Air Bearing Upgrade for Split-Hopkinson Pressure Bar (SHPB) Experiment Donald Hayes II, Joseph Chason, Sarah Napier, Zachary Johnson

Department of Mechanical Engineering

Sponsor Dr. Joel House Eglin Air Force Base Research Laboratory Advisor Erica Cosmutto FAMU/FSU College of Engineering April 12, 2012

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Overview

Introduction Concept Generation & Selection Final Concept Components Functional Diagram Results & Discussion Project Budget Safety Concerns Conclusion Acknowledgements Questions 2

Introduction: SHPB Basics

Initial Strain Pulse Striker Mechanism Incident Bar / Strain Gauges / Bushings Reflected Pulse Material Sample Transmitter Bar / Strain Gauges / Bushings Transmitted Pulse Momentum Trap 3

Introduction: SHPB Basics

Striker Mechanism Strain Gauges Material Sample Data Data Acquisition System Strain Gauges Momentum Trap 4

Introduction: Needs Assessment

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Research air bearings for existing 5/8 inch diameter journal bearing system

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Develop:

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Bar alignment method

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System upgrade from journal bearings to air bearings

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Determine efficiency of air bearings over journal bearings 5

Introduction: Objectives

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Analyze SHPB design based on use of air bearings Analyze:

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Hardware cost



Interface requirements

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Installation procedures

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Impact on bar geometry Assess strain gauge technology Develop procedure to align bars Design a working prototype to show knowledge of system Remain within $2500 budget 6

Generating Concepts: Methodology

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Break system into base components Treat components as individual systems Generate multiple solutions per system Determine most suitable components Combine and implement into design 7

Generating Concepts: Components & Concerns

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SHPB Components

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Base Structure

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Striker Mechanism

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Incident & Transmission Bars

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Strain Gauges

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Air Bushings

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Momentum Trap

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Air Supply System Concerns

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Bar Alignment Method

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Data Acquisition 8

Generating Concepts: Criteria

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Cost Weight

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Size Simplicity

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Durability

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Portability Scalability

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Accuracy Data Quality

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Ease of Use 9

Selecting Concepts

Cost Mass Size Simplicity Portability Scalability Data Quality Ease of use Durability Accuracy Score

Final Concept

Component Base Structure Striker Mechanism Incident, Transmission & Striker Bars Strain Gauges Air Bushings Momentum Trap Gas Supply Data Acquisition Bushing Alignment Method Final Selection T-Slotted Framing Electric Solenoid 0.75” dia. 1566 Steel Foil Type (Vishay Co.) 0.75” ID (New Way Air Bearing Co.) Custom Compressed Argon NI Hardware & Software (LabView) Laser Insert 13

Components: Striker Mechanism

Solenoid Striker bar Striker bar tube McMaster Carr 336 ozf.

Air line

Components: Air Bushings

Bushing block housing Air bushing New Way Air Bearings 0.75” Inner Diameter 30 lb. Radial Load 15

Components: Strain Gauges and Material Sample

Strain gauges 16

Components: Strain Gauges and Material Sample

Vishay Micromeasurements Gauge factor ≈ 2 Resistance = 120 Ω Located 6” from sample Strain gauges 17

Components: Strain Gauges and Material Sample

Copper specimen ~ 0.3” diameter ~ 0.3” thick 18

Components: Momentum Trap (bar stopper)

Final Concept

Incident bar Length = 8 ft.

Width = 7 in.

Height = 3.5 in. Copper specimen Striker bar mechanism Air bushing Strain gauges Transmitter bar Momentum trap 20

120 Volts AC

Functional Diagram

DC Power Supply Wheatstone Bridges Data Acquisition System Data Recording & Storage Activation Switch Striker Mechanism Incident Bar / Strain Gauges / Bushings Material Sample Transmitter Bar / Strain Gauges / Bushings Momentum Trap Data Power Gas Gas Supply 21

Steel Incident Bar Copper Sample Steel Transmitter Bar 22

Reduced Sample Area

Strain Pulse: Visualization

D steel D Copper 0.75 in 0.31 in 23

Visualizing the Strain Pulse

Surface: Von Mises Stress Yield Stress σ y Copper ½ σ y Steel 24

Analyzing Data

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LabView hardware & software 250 kHz Sampling rate

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Measured Voltage Calculated Strain Strain Waves Strain Energy

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Geometric Definitions + Boundary Conditions Material Description 25

Data Acquired 26

Incident Wave Equal to Consequent Waves 27

Elastic Impulse Wave Area

Strain-Seconds % of Initial Pulse Incident 1.15 x 10 -8 ∫dε*dt (s) Reflected 4.47 x 10 9 100 % 38.7 % Transmitted 5.46 x 10 -9 "Absorbed" 47.3 % 14 % Low sampling rate error 28

Discussion

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Potential improvements in system

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Use of stainless steel bars

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Potential improvements in testing

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Annealed copper specimen

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Higher data rates

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Used 250 kHz Recommend

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1 MHz

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Implement friction imitation method to evaluate efficiencies between air bushings and journal bearings 29

Project Budget

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Within budget Total budget

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$2,500

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Total expenditures

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$2117

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Percentage under budget

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15% 30

Bearings 64,0% Allocation of Expenditures Striker 2,8% Support Systems 3,0% Frame 3,1% Bars 11,9% Budget Savings 15,3% 31

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Safety Concerns

Pinching/crushing fingers Flying Fragments Electrocution 32

Review

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Analyzed:



SHPB design based on use of air bushings



Interface requirements

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Installation procedures

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Designed alignment tool

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Impact on bar geometry 33

Review

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Assessed strain gauge technology

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Foil gauges sufficient

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Semiconductor gauges if high accuracy required Designed a working prototype that shows knowledge of system Remained within $2500 budget

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Total expenditures ≈ $2100 34

Conclusion

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Accomplished major requirements!

Critical Factors

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Segmented design

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Ease of manufacture

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Team cooperation

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Excellent support 35

Acknowledgements

We would like to thank the following people for their help and support which made this project a success… Dr. House – Eglin AFRL Dr. Shih – FAMU/FSU COE Dr. Kosaraju – FAMU/FSU COE, CAPS Dr. Dalban-Canassy – FAMU/FSU COE, ASC Dr. Hovsapian - CAPS Mr. Bob Walsh - NHMFL Mr. Dustin McRae – FAMU/FSU COE, NHMFL Dr. Solomon – FAMU/FSU COE Mr. Ryan Jantzen – FAMU/FSU COE, HPMI Mr. Bill Starch - ASC Dr. Hellstrom – FAMU/FSU COE, ASC THANK YOU!

Questions? Comments?

Detailed Budget Solenoid T-slot Framing 1 1/2 inch (96 inch length) Incident & Transmission Bar: 1566 Steel Bar 0.75 inch (36inch length) Quantity Unit Cost Total Cost 1 69.94

$69.94

2 48.15

$96.30

2 29.42

$58.84

T-slot Framing 1 1/2 inch (4 foot length for 6 inch braces) Air Manifold (72 inches) Striker Bar: 1566 Steel Bar 0.75 inch (6inch length) Right Angle Fastener Fasteners (Packs of 4) Strain Gauges (Pack of 10) Air Bushings 0.75 inch Bushing Block 0.75 ID 0.25”x3”x72” Aluminum Sheet 0.75” Diameter x 12” Long High Tolerance Aluminum Bar 12” Aluminum U-Channel 0.75” diameter x 6” Long High Tolerance Steel Bar Total 1 1 2 16 16 3 4 4 1 1 1 1 25.15

16.34

5.17

4.06

2.71

20 265 135 40.35

12.1

14.19

5.26

$25.15

$16.34

$10.34

$64.96

$43.36

$60.00

$1,060.00

$540.00

$40.35

$12.10

$14.19

$5.26

$2,117.13

Velocity Calculations The velocity of the striker bar is needed The only requirement is that the specimen plasticaly deform while the incident and transmitter bars are only loaded elasticaly The following equations show the process  yc  70MPa Areac    .4

in 2 2  0.126 in 2 F   yc Areac  Yield stress of copper Area of the copper Force Required to reach Yield Next the mass of the steel bar is computed   7.85

gm cm 3 v    0.75

2 2 in 2  6 in  2.651 in 3 mass  v    0.341 kg Density of steel Volume of the 3/4 inch diameter, 6 inch striker bar Mass of the striker bar 39

Velocity Calculations Next the amount of time the striker bar will impact the incident bar c  6100 m s L  6in t  2  L c  4.997

 10  5  s Speed of wave propogation in steel Length of Striker bar Pressure wave propogating down the strikerbar and returning = 2 x length/speed t  49.967

  s Duration of impact Finaly the minimum velocity of the striker bar needed to plasticaly deform the specimen V  F mass  t  0.832

m s V  1.86

 mi hr Minimum velocity of striker bar needed to plasticaly deform the copper specimen 40

D Velocity Calculations Acc  130ozf mass  m 105.993

s 2 Acceleration available from the chosen solenoid Length of piston with given force  .5A t 2 Generic dynamic position equation timesol  Lsol .5

 0.022 s Vstkr   5.191

 mi hr Derived time, from previous equation Calculated velocity from given solenoid 41

Plastic Energy Derivation • • Stress Strain σ = F/A ε = (Li – Lo) / Lo • Gauge Factor GF = [ (Ri - Ro) / Ro] / ε • Data Strain ε (Ri) = [ (Ri - Ro) / Ro] / GF 42

Plastic Energy Derivation • Strain in Specimen: dε avg / dt = ( c b / L s ) * (ε I – ε R – ε T ) • Integration: ε s = (C b / L s ) * ∫ 0 t [(ε I – ε R – ε T ) *dt] Strain through the specimen 43

Plastic Energy Derivation • Strain energy for each wave Kinetic energy = 0.5 * m * v 2 • • Initial Reflected E I = 0.5* A B * C B * E B * T *ε I 2 E r = 0.5* A B * C B * E B * T *ε R 2 • Transmitted E t = 0.5* A B * C B * E B * T *ε T 2 44

Plastic Energy Derivation • Strain energy δS E = E I – E R – E T • Plastic Energy absorbed by specimen E s = 2 * δS E 45

2000 Solenoid Optimization

Unacceptable Region

1500 1000

Acceptable Region

500 0 0

Unacceptable Region

10 20 30 40 50

Cost ($)

60 70 80 90 46 100

Weak Formulation for FEA   A  d 2 d t 2 T  d d x    d d x u  ) 0       w    A  d 2 d t 2 T  w  d d x    d d x u  )   d ( x t ) 0      (   A )  d d t w  d d t T  )  d ( )   d d t T 0 47

Weak Formulation for FEA 48