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
