Microsoft Power Point - FD&E2005-JR

8/9/2019 Microsoft Power Point - FD&E2005-JR

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Rehkopf FD&E Oct. 05

High Strain Rate CharacterizationOf

Engineering Materials

J.D. Rehkopf

Ford Motor Company


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High Strain Rate Behaviour

Materials can behave quite differently at high rates (crash)

compared to quasi-static (e.g. cargo)

At faster strain rates, plastics can becomemuch stiffer, stronger, and more brittle.

Enggstress

Design for crash applications requiresmaterial behaviour at high ratestypically 100s strain per second.

Engg strain

increasing strain rate


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High Strain Rate Behaviour

Energy Absorbing TPOleft: Slow rate, right: High rate

Cladding TPOleft: Slow rate, right: High rate


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High Strain Rate Tensile Testing

Why: behavior at rates appropriate for the application

How: - Plane Stress State

- Uniform Stress/Strain in gauge- High Accuracy Measurement of load and strain

- Rates 1 800 s-1 at 40C to +120C

For: - Direct input for FEA modeling

- Material Development (modulus, strength, ductility)


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How is the data used?

! FEA sofware material models:Account for increased strength with increased strain rate

" Johnson-Cook

" Cowper-Symonds

" Zerrilli-Armstrong

)(lnlnln1

1 pDpfgivesDp

f +=+=

&&

( ) ( ) DfpD

fp

ln1lnln1

1

+=

+=

&

&

)( 1)( +=

o

max

o

max

&

&

&&

n

p

o

CTCTCCC

54310 lnexp +

++=

&

&


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Material Models

15

20

25

30

35

40

45

50

0 100 200 300 400 500

Strain Rate (s-1

)

T

rue

Yield

St

ress

(M

Pa)

Test Data

Johnson-Cook

Cowper-Symonds

Zerilli-Armstrong


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Conducting Good High Rate Tests

! Initial loading

! Constant velocity

! System frequency

! Measurement System

! Time lag

! Filtering

! Specimen Geometry


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Experimental Setup

Piezoelectric load cell

Laser Doppler Extensometer (LDE)

Slack Adapter to attain speed

Melt Pot for alignment

LVDT to measure stroke

pull


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Importance of Test System

TIME

SYSTEM RINGING

MINIMAL

SYSTEM RINGING


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Laser Doppler Extensometer (LDE)

!

Selectable measuring length (gauge), down to 4 mm! Resolution of Strain 1 m

pull


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Laser Doppler Extensometer for High SpeedNon-Contact Strain Measurement

motion #2

motion #1Laser spot

#1

Laser spot#2

Strain calculated fromdifference betweenmotion #2 and motion #1

pull


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Importance of Accurate Strain Measurement

A,B,C from LVDT

a,b,c from LDE (lasers)


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High Rate Characterization of Materials

in the Auto Industry

! SAE High Strain Rate Plastics Consortium" Plastics, Glass Reinforced Plastics

! USAMP/Automotive Composites Consortium Energy Management Working Group" Composites (components primarily)

! A/SP Strain Rate Characterization Committee" Advanced High Strength Steels


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SAE HSRPC

Who *

What

Why

When

How

! GM, Ford, Delphi, Visteon, BASF, Basell, Bayer,DOW, DSM, GE / LNP, LG Chem, Solvay

! SAE Consortium : Cooperative ResearchProgram SAE Subcommittee

! To develop an industry standard for High StrainRate Tensile Testing of Plastics

! Formed in 2001 under impetus of UDRI(Principal Investigator)

! Self-Funded by Membership Dues of$10K + $5Kand In-Kind Work

* Toyota paid initial $10K but did not participate


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HSRPC Main Mission:

To develop an industry standard for High Strain RateTensile Testing of Plastics (incl. LGFR)

Why?

i) to ensure that experimental data is valid and of high quality

ii) to enable sharing of test data across companies and labs

iii) to enhance the understanding of high rate behaviour

Develop better material models for predictive modeling incrash applications.


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Future Work Short Term

! Address specimen geometry issues

(particularly for GFR plastics)! Fiber Orientation

! Geometric Stress Concentration

! Molded vs Machined

! Possible collaboration with ACC-EMWG


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Plastics Applications

! Fascias/Bumpers! Claddings

! Rear Wheel Lips

! Front Wheel Lips

!

Door Trim! Pillar Trim

! IPs

! Air Bag Covers


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MMIC TPO Cladding: Tensile Test Results


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MMIC TPO Cladding:Conclusions Material Development

! Color had no effect on the MMICs tested

! ForMMICs and painted TPO, tensile strengthincreased significantly with increasing strain rate,

within the high rate region of 1.3 and 2.5 m/s! MMIC-2 and MMIC-3 had much higher tensile

strength than MMIC-1 and painted TPO

! MMIC-2 and MMIC-3 had much lower failure strainsthan the painted TPO or MMIC-1 (< 6 %)

! Cladding and plaques had the same tensile strengths


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Interior Door Trim (ABS)


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A/SP Strain Rate Characterization Team

Who *

Why

When

How

What

! DCX, GM, Ford, Steel SuppliersLabs: UDRI, Los Alamos, ORNL

! To get high strain rate mechanical properties of AHSS forcrash analysis, using existing material models

! Formed in 1995

! Funded by USAMP, A/SP and In-Kind Work by OEMs andSteel Suppliers

! Split-Hopkinson Compression, Split-Hopkinson Tension,Servo-Hydraulic Tension, Hemispherical Impact of Disks,Double Hinge tests, Conical-column crush (drop tower),circular columns crush (servo-hydraulic)

* Supplier Partnership has varied over the years.


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AHSSFinal Report, Proposal Number R-12436 Prepared for Auto/Steel Partnership, Dec. 2000

ASTM D1822 Type L Specimen (Dimensions in inches)

Gauge 9.5 mm long x 3 mm wide


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Specimen Type #2

Gauge 20 mm long x 10 mm wide


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AHSSFinal Report, No.: TRP 0038 AISI/DOE Technology Roadmap Program , May 2002


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AHSSFinal Report, No.: TRP 0038 AISI/DOE Technology Roadmap Program , May 2002


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Cast Mg and Al for Structural Applications


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AM60 Results High Rate

0 0.05 0.1 0.15 0.2 0.25

Strain (mm/mm)

0

50

100

150

200

250

300

350

Stress(M

Pa)

F5 2m/s

N3 12m/s

M2 4.5m/s

M1 5.7m/s

L5 3m/s

L4 2m/s

F5 2m/s

N3 12m/s

M2 4.5m/s

M1 5.7m/s

L5 3m/s

L4 2m/s


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AM60 Results Rate Effect

0 0.05 0.1 0.15 0.2 0.25

Strain(mm/mm)

0

50

100

150

200

250

300

350

St r

ess(

MP

a)

K2 150 mm/s

J5 93 mm/s

I3 10mm/s

I1 14mm/s

G1 11mm/s

E3a 1mm/s

D2 1mm/s

K2 150 mm/s

J5 93 mm/s

I3 10mm/s

I1 14mm/s

G1 11mm/s

E3a 1mm/s

D2 1mm/s


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AM60 Results - Variability

0 0.05 0.1 0.15 0.2 0.25

Strain (mm/mm)

0

50

100

150

200

250

300

350

Stre

ss(MPa)

K1 15mm/s, RT

JB4 15mm/s, RT

J2 10mm/s, RT

I3a 10mm/s, RT

I2 10mm/s, RT

I1 14mm/s, RT

H5 18mm/s, RT

H3 11mm/s, RT

G1 11mm/s, RT


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AM60 Conclusions

!

Sample-to-sample variability in tensile behaviournot atypical of cast materials

!

No significant effect of temperature over 40Cto + 60C

! No significant effect of strain rate over 0.0625 s-1

to 480 s-1


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Cast Aluminum C448

Cast Aluminum C448

0

50

100

150

200

250

300

0 10 20 30 40

strain %

stress

(M

Pa)

50 mm/s LDE

50 mm/s Extens.

500 mm/s4 m/s (~400 s-1)


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Summary:High Rate Behaviour of Engineering Materials

Need Data -- Good Experiments are Key

Initial loading, ringing in load signal, strain measurement

- Incorporate data into existing FE material models

- Assess model with correlation component test- Develop new models as needed

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Microsoft Power Point - FD&E2005-JR