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Wed, 08 January, 2020

Student Name

Oliver Logan

Research Title

Fracture toughness testing of non-sharp defects

Keywords

Fracture toughness, non-sharp defects, constraint procedures

Sponsor

TWI

Affiliated University

University of Bristol

Supervisors

Dr Isabel Hadley (TWI Ltd.), Dr Nicolas Larrosa (University of Bristol)

Start Date

Sept 2019

Project Outline

Structural integrity assessment procedures conventionally categorise flaws either as infinitely sharp cracks or local thinning areas (LTAs). Defects failing an LTA geometry check are assumed to be sharp cracks, and a fracture mechanics based approach is followed for the assessment. The LTA rule may be appropriate for general corrosion or mechanical gouges where there is a change in wall thickness and plastic collapse is considered to be the failure mechanism. However, for non-sharp defects, the failure mechanism is not clearly defined, in principle.

Simplifying blunt defects to LTAs can be non-conservative on one hand, and to sharp cracks can be excessively so on the other hand. As a result, there is a need to develop procedures that account for non-sharp defects more realistically.

This PhD is based on basic constraint procedures in standards (R6, BS7910) and aims to expand the capabilities to allow less conservative assessment of non-sharp defects.