Fracture Toughness in Aggressive Environments

Webinar on Fracture Toughness in Aggressive Environments:
Effect of Crack Monitoring Techniques on Test Results

There is an industry requirement to generate accurate fracture toughness data in aggressive environments for engineering critical assessments (ECAs). The use of clip gauges in aggressive environments limits the quality of the test data and the range of tests performed by TWI’s world-leading environmental testing laboratories. Furthermore, on many occasions, the severity of the test environment does not allow the use of a clip gauge. Therefore, to maintain a competitive advantage in the field, TWI is developing the direct current potential drop (DCPD) approach further and is hereby performing a detailed comparative study, to understand if the load line displacement indirect estimations for the environmental tests are within the level of accuracy suggested by the air testing standards. This webinar reflects on the fracture toughness resistance (R-) curve testing using the unloading compliance (UC) method and the rising displacement method using DCPD for the crack monitoring. The test environment was deaerated saltwater (DSW) at 4°C, with cathodic protection (CP). The tests were performed on compact tension (CT) specimens from F22-75K material, following the ASTM E1820-23b standard. Three different K-rates have been used in order to evaluate the effect of K-rate on the fracture toughness result. An attempt to evaluate the accuracy of the predicted crack length using clip gauges or DCPD has been made by stopping some tests shortly after cracking developed under the test conditions, and comparing with the actual crack on the fracture faces. Finally, the normalisation method has been used to compare test results with those generated from testing specimens using DCPD.

This webinar describes the test procedures, data analysis methods and results for the fracture toughness testing performed in this research.

Speakers

Fokion Oikonomidis

Senior Project Engineer, Technology
TWI Ltd

Fokion joined TWI in 2012 as a Project Leader and has since developed expertise in small and large scale fracture toughness testing in air, seawater, sour and H2 environments. Fokion has supervised postgraduate students in NSIRC and has been involved in the group's quality systems for 9 years. During the six years before joining TWI, he worked in the area of Fracture Mechanics both in a research centre in Belgium and during his 1st PhD at the University of Bristol. Fokion is a chartered mechanical engineer with work experience in the fields of water and wastewater treatment, building services, health and safety and business process management in the aerospace industry. Fokion has served in the Hellenic Air Force and has an MBA degree in general business administration from the University of Hull. Fokion obtained his 2nd PhD in Change Management at the University of Newcastle upon Tyne.