Understanding
FRACTURE TOUGHNESS
for Pipeline Crack Assessments
November 21, 2024 | Blade Energy Partners’ office | Houston

Course Syllabus

Chapter 1: How Pipelines Fracture

• Understanding what controls fracture of pipelines under burst and cyclic conditions
• Fracture process
• Initiation
• Stable propagation
• Arrest
• Fracture of pipelines with sharp cracks and notch-like/blunted defects
• Fracture behaviors
• Brittle cleavage
• Quasi cleavage
• Ductile micro void coalescence
• Intergranular and transgranular fractures

Chapter 2: Fracture Toughness Testing

• Common fracture toughness definitions, description of toughness test methods, and identification of the relevant physical fracture event they measure
• Charpy impact notch toughness testing
• Brittle lower shelf, ductile upper shelf, and transition regions
• When ductile initiation can be assumed
• Quasistatic fracture toughness testing
• Brittle and ductile fracture initiation, and ductile tearing stability
• J-integral, and its qualifications: JC, JU, JIC and J-R crack growth resistance curve
• Crack Tip Opening Displacement CTOD: δC, δU, δIC
• Engineering meaning of Charpy, J-integral and CTOD toughness data
• Considerations for selecting toughness values for in engineering assessments
• Common tests specimens and form of loading
• C(T), SEN(B), SEN(T), M(T)
• Constraint effects
• Effects of test specimen size, loading configuration, flattening, and temperature
• Considerations when testing the seam weld area: bondline, HAZ
• Factors that affect the fracture transition test temperature
• Common sources of measurement errors
• A fracture toughness database of pipe body and seam weld locations obtained from API 5L vintage and modern line pipe steels
• Is there a lower bound fracture toughness for API 5L vintage steels?

Chapter 3: Fracture Toughness Correlations

• Transferability of toughness results from sub-size test samples to full size pipelines applications
• Common initiation toughness Charpy to J and K and CTOD correlations
• Origin of correlations including the type of tests performed and steel characteristics
• Correlations applicability space
• lower shelf brittle behavior
• transition fracture behavior
• upper shelf ductile behavior
• Charpy to ductile stable tearing JR- Δa correlations and their engineering meaning
• Physical fracture parameters used to correlate the toughness values
• Quantifying the degree of conservatism in the correlations
• Comparison of correlations with toughness data obtained from API 5L line pipe steel: pipe body and seam weld toughness

Chapter 4: Fracture Toughness for Pipeline Engineering Applications

• Application of fracture toughness values in failure pressure predictions and fatigue crack growth life estimations
• Crack and crack-like anomalies assessment requirements in PHMSA regulations in §192.933 (d) and fracture toughness requirements in §192.712 (d)
• Relationship of the chosen failure stress model, fracture behavior being evaluated, and the necessary type of fracture toughness
• Effects of fracture toughness and defect dimension on the failure pressure prediction
• The influence of fracture toughness in fatigue crack life estimation
• Options when no measured fracture toughness data are available
• Input fracture toughness options in failure stress models: NG-18 ln-sec, Newman-Raju, CorLAS, API 579/ASME FFS, and MAT-8