fracture toughness testing in line pipe
TRANSCRIPT
Strength vs Toughness
PD2t ?
Test Sample Specifying Directions
BondLine
Location 1 2 3 4 5 6 7 8 9 10 11HV10 190.8 198.7 209.6 221.0 223.6 218.4 220.2 228.2 221.7 214.7 190.8HRB
[converted]91.3 92.9 95.0 97.0 97.4 96.5 96.8 98.1 97.1 95.9 91.3
HRC[converted] 10.1 12.1 14.5 16.9 17.4 16.4 16.8 18.3 17.1 15.6 10.1
BondLine
Location 12 13 14 15 16 17 18 19 20 21 22HV10 185.3 197.3 196.4 207.0 202.7 199.1 200.3 205.4 205.8 201.1 185.7HRB
[converted]90.0 92.6 92.4 94.5 93.7 93.0 93.2 94.2 94.3 93.4 90.1
HRC[converted] 8.7 11.7 11.5 14.0 13.0 12.2 12.4 13.6 13.7 12.6 8.8
BondLine
Location 23 24 25 26 27 28 29 30 31 32 33HV10 192.4 197.3 194.3 203.8 207.1 207.4 206.8 205.9 207.8 207.0 190.2HRB
[converted]91.6 92.6 92.0 93.9 94.5 94.6 94.5 94.3 94.7 94.5 91.1
HRC[converted] 10.5 11.7 11.0 13.2 14.0 14.0 13.9 13.7 14.1 14.0 10.0
Near ID
Base HAZ HAZ Base
Mid-Wall
Base HAZ HAZ Base
Near OD
Base HAZ HAZ Base
Test LocationSeam Weld Bond Line
Charpy V-Notch Impact Test• Standardized test: ASTM A370 and
E23• Simple • Inexpensive• A dynamic impact test • Measures the energy to fracture
CVN Impact Test
Lateral expansion
(mle)%
Shear
CVN Impact Test
Transition Temperature• For ferritic steels, the toughness changes
dramatically with temperature
Using Charpy Values
• The energy measured does not distinguish between plastic deformation, crack initiation and propagation
• Fracture energy is not directly applicable to critical flaw size calculations
• Conversions to fracture mechanics based values using empirical correlations must be used
• Transition curve methodology using a master curve approach can be employed.
ERW Seam
KIC Fracture Toughness
• Based on stress intensity solutions.• A linear elastic test
𝐾 = σ π𝑎
KIC Fracture Toughness
Crack Tip Opening DisplacementCTOD
• Easily understood• Applicable to the full
range of toughness• Not size independent• Specimen tested must be
as close to original thickness as possible
Thickness affects toughness
J-Integral Fracture Toughness• Based on a line integral around the crack tip• Allows for greater crack tip plasticity during
testing.• Measures the onset of Stable Tearing
– Can be done using a single edge bend specimen– Prefer a compact tension specimen
SpecimenJ
[lbs/in] Qualification
KJ(Converted)
[Ksi √in]
CTOD at max Load
[in]
J at Max Load
[lbs/in]
KJat Max Load (Converted)
[Ksi √in]432-Demo 90 JQ 55 δm=0.0008 Jm=115 60.0
JIC Testing
Ductile to Brittle Transition Behavior of Ferritic Steels
• Scatter in the toughness data at a given temperature follows a characteristic statistical distribution.
• The shape of the fracture toughness transition curve is the same for all ferritic steels. The only difference is the position.
Master Curve Approach
• Estimate test temperature with Charpy transition data (full size values)
• Test a set of six or more fracture toughness tests at the temperature
• Can use other temperatures.• Use equations in ASTM E1921 to
generate the transition curve.
o28 J100 MPa m 18 CT T= -
Temperature Shift Correlation, ASTM E1921
Master Curve Approach
Conclusions• Fracture toughness testing can be used along with
stress analysis and inspection limits together determine the relative safety of a structure or component.
• Fracture mechanics can be also used to determine the final fracture condition.
• Various testing methods are available for determining a material’s resistance to fracture
• A master curve approach to fracture toughness can give a more complete picture of the material properties.