Comparisons of the Solutions of Common FFS Standard Procedures to Benchmark Problems

The common practice in industry to assess the severity of crack-like defects in structural components is to follow methodologies usually compiled within standardised procedures or codes. The most popular Fitness-For-Service (FFS) procedures are (1) the UK nuclear industry standard for fracture assessment R6, (2) the American Petroleum Institute FFS procedures, API 579, and (3) the British Standards Institution assessment procedure, BS7910. These codes usually assess structural integrity by means of the Failure Assessment Diagrams (FAD) in which elastic fracture and plastic collapse are assessed independently and combined in a graphical way. Due to the formulations within the codes being different, some divergence is expected in the results provided. The aim of this paper is to show the differences in the results in the assessment of two candidate problems assessed by the API 579, R6 and BS 7910 procedures and to highlight and discuss the possible reasons behind these differences.