microsoft power point - fd&e2005-jr
TRANSCRIPT
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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
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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