NA 513

Welded Structures Laboratory/Courses/NA 513

Defect Assessment for Marine Structures (3 Credits)

Defect Assessment of marine structures

Course Description:

Defect Assessment or Engineering-Critical-Assessment (ECA) has become a powerful tool for providing quantitative evaluation of an in-service structure or component’s fitness for continued operation when a flaw or damage is detected. The product of an ECA assessment can be used to support a decision to run as is or implement proper remediation and/or monitoring techniques. ECA has also been increasingly used to support quality acceptance criteria during construction by demonstrating fitness for purpose of any material grade deviation, fabrication, and construction-related imperfections, as well as quality inspection requirements. This course discusses basic mechanics principles associated with modern defect assessment methodologies for applications in engineering structures in general and marine structures in particular. Topic areas include:

Fatigue of structures

  1. Characterization of flaws or damages and idealization:
  • Construction-related flaws (pores, inclusions, hot/cold cracking)
  • Service caused damages: corrosion, corrosion cracking, fatigue cracking, mechanical damages
  1. Failure mode definitions:
  • Brittle (unstable) fracture
  • Ductile tearing
  • Fatigue crack propagation
  • Plastic collapse
  1. Stress categories and modern treatment
  • Primary stresses
  • Secondary stresses
  • Finite element based decomposition
  • Displacement- versus load-controlled loading
  1. Fracture mechanics treatment:
  • Fracture driving force solutions
  • Treatment of small cracks
  • Treatment of residual stresses
  • Limit load definitions
  1. Material resistance characterization:
  • Material fracture toughness (Kmat)
  • Estimation using Charpy toughness data
  • Material stress-strain properties
  • Crack growth rate and S-N curve
  1. Fatigue life calculation:
  • Crack propagation life
  • Variable amplitude loading
  1. Failure assessment diagram (FAD) and usage:
  • Methods in API 579/ASME FFS-1
  • Methods in BS 7910/R6
  1. Real world ECA examples from marine, petrochemical, and power generation industries
  2. On-going research areas and course summary.

Grading: HW (~6): 30%; 2 quizzes: 35% each;.