Structural members occasionally fail. The reason for the failure may e.g. be undetected fabrication defects. Acceptable defect sizes, which may safely remain undetected, can be determined using available deterministic and/or probabilistic computer programs based on fracture mechanics theory.

Purpose

One of the advantages of performing fracture mechanics and fatigue assessments is to determine the acceptable defect sizes for e.g. structural members, components and pipes.

Benefits

Fracture mechanics and fatigue assessments will help the client to determine the acceptable defect sizes for a given material and design. This could e.g. be used to reduce the level of required repair welding during pipe offshore installation.

Fracture mechanics assessments may also be used for lifetime extension. A number of platforms are in an excellent condition after the original design life has expired and there is frequently a need to extent the service life of these structures.

Features

DNV has the technical competence, testing facilities and computer tools to perform fracture mechanics and fatigue assessments.

Acceptable defect sizes, which may safely remain undetected, can be determined using available deterministic and/or probabilistic computer programs based on fracture mechanics theory. During service, the calculated safety can be updated by taking into account the result from inspection. The significance of detected defects may be assessed, and required inspection intervals may be established.

DNV’s laboratory is equipped to carry out the necessary testing to determine parameters for the properties of the materials involved.

In addition to IDEAS and ABAQUS for structural analyses, a number of software tools are used for fracture mechanics and fatigue assessments, including:

• CRACKWISE and FATIGUEWISE for fracture mechanics assessments
• Program for weldability and weld cracking evaluations
• Various programs including PROBAN and PROINSP for reliability calculations
• Proprietary spread sheets for cathodic protection design calculations
• Program "COMCAPS" for calculating the performance of designed cathodic protection systems
• Program "CORROLINE" for prediction of material loss in pipeline.