2. 2
Questions to Answer
• Which metals standards have changed recently?
• Why and how have the standards changed?
• How does it effect me?
• How do I ensure compliance with the latest
standards?
3. 3
Product Standards Linked to Testing Standards
ISO 6892-1
2009
ASTM
E8M:2013
ASTM A370
Standard Test
Methods and
Definitions for
Mechanical Testing of
Steel Products
ANSI/API Spec 5L
Petroleum and natural
gas industries
Steel pipe for pipeline
transportation systems
ISO 3183:2012
Petroleum and natural
gas Industries
Steel pipe for pipeline
transportation systems
ISO 377:1997
Steel and steel
products
Location and
preparation of samples
and test pieces for
mechanical testing
ISO
7438:2005
ASTM
E290:2013
ANSI/API
Spec 5L
ISO
3183:2012
ISO
148-1:2010
ASTM E-23
ANSI/API
Spec 5L
ISO
3183:2012
Bend
Testing
Charpy
Impact
Testing
Tensile Testing
Example: Pipe and
Tube Applications
5. 5
• ISO 6892-1:2009
• Added a Strain Rate method – commonly referred to as
“Method A”
• Separated Method A (strain rate)and Method B (stress
rate)
• Various other small changes
• ASTM E8/E8M-11
• The two separate standards have been combined into
one standard for imperial and metric
• Clarified testing speeds and added tolerances for strain
rate
• Various other small changes
Significant Recent Changes
6. 6
Strain Rate
• What is strain rate?
• Change in Specimen Length/Original Gauge Length/Time
• Change in strain per unit of time (in/in/min, mm/mm/s, %/s, s-
1)
• Typically measured with an extensometer on metals
specimens
• Why is this getting industry-wide attention now?
• In 2009, the primary metals tensile testing standards were
updated to include more strict requirements for strain rates
and more detailed guidance on how to achieve target strain
rates
• ISO 6892-1:2009 superseded EN10002-1
• Occurred at the end of 2009
• Introduced control “Method A” based on maintaining strain
rates
• ASTM E8/E8M–09 was updated to include straining rate method
and guidance on proper test rate control
7. 7
Why Strain Rate?
• Some metals have mechanical properties that are strain-rate
dependant
• From ISO 6892-1
“Method A is intended to minimize the variation of the test
rates during the moment when strain rate sensitive
parameters are determined and to minimize the measurement
uncertainty of the test results.”
• From ASTM E8/E8M-11
“The reproducibility of yield strength test results from machine
to machine and laboratory to laboratory is good.”
“In order to reproduce yield test results, for strain-rate
sensitive materials, it is important that strain rates during the
determination of yield are similar.”
“The yield strength of some materials can change by more
than ten percent when tested with the slowest and then the
highest speeds permitted by E8/E8M.”
8. 8
Control Modes in ISO 6892-1 and ASTM E8M
ISO6892-1:2009
Method A – Closed
Loop Strain Rate
Method A - Estimated
Strain Rate
Method B – Stress
Rate
ASTME8M-11
Method A – Rate of
Stressing
Method B - Rate of
Straining
Method C – Crosshead
Speed Control
Strain control
(Extensometer)
Stress control
(load)
Extension control
(crosshead)
10. 10
System Compliance
Zero load Under load
Deflection
L
o
Zero load
Lo+ΔL
Under load
Compressed lead screw and
drive system deflection
Load cell
deflection
Crosshead and
base deflection
Grip, jaw face and
adaptor deflection
Amplified deflection!
11. 11
System Requirements
• Load frame
• Precise and stable drive system
• Grips
• Able to securely grip the specimen during the test
without slippage
• Extensometer
• High-precision device with stable feedback
• Software/controller
• Responsive control loop able to maintain ±20% or
±40% limits
• Lab environment
• Vibration and shock free
12. 12
ISO 6892-1 Method A – Closed Loop Control
Strain Control Removes Compliance Effects
±20%
Error
Bounds
0.2% Offset
Yield
Strain Control slows
the crosshead down
to compensate
Significant and rapid
change in system stiffness
during the onset of yield
Test being performed in closed loop strain control
13. 13
ISO 6892-1 Method A – Estimated Rate
Test being performed in extension control
±20%
Error
Bounds
Constant crosshead
displacement
0.2% Offset
Yield
Strain rate moves into ±20% error
band during yield. Correct rate
during Rp0.2 calculation point
14. 14
Why Instron® Customers use Strain Control
• Repeatable and comparable results
• As some metals are strain-rate sensitive this reduces
variance between labs and systems
• Improved efficiency
• Shorter testing times with a range of specimens
• Automatic tuning reduces setup time
• No need to use a specimen for tuning
35% time
savings
when compared
to estimated rate
ISO 6892-1 Method B – 10Mpa/s
ISO 6892-1 Method A – Estimated rate 0.00025/s
ISO 6892-1 Method A – Closed Loop rate
0.00025/s
Seconds
50 100
Time taken to run a ISO 6892-1:2009
test on Aluminium
0 25 75
15. 15
ISO 6982-1 or ASTM E8M – Closed Loop vs. Estimated Rate
Steel Specimen on a Rigid Load String
0
100
200
300
400
500
600
700
0 5 10 15 20 25 30 35 40 45 50 55 60 65
TensileStress(MPa)
Time (s)
Closed Loop Estimated Rate
40% time
savings
when compared
to estimated rate
16. 16
Which Systems Meet ISO 6892-1?
ISO 6892-1:2009
Method A
Strain Rate
Closed Loop
Strain Rate
Estimated
Strain Rate
Method B
Stress Rate
Stress Rate
5900 Series – Advanced controller, high precision
3300 Series – Affordable accuracy
17. 17
Instron Solutions
• Controlling the strain rate during the test gives you
more repeatable and comparable results
• Instron's stable, yet responsive, automatic strain
control on 5900 controllers removes the need to
tune time consuming and complex PID gain terms
• Walk up and test capability over a wide range of
metals with various degrees of stiffness (steel,
aluminium, etc.)
• No setup required when changing specimen types
or strengths
• Compliance with the latest international ISO and
ASTM standards
18. Does this sound familiar?
Do you see the same challenges in
your business?
www.instron.com
for more information
