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Fracture toughness in aggressive environments: effect of crack monitoring techniques on test results

Project Code: 34847

Start date and planned duration: April 2022, 20 months


  • To investigate the effect of testing techniques (DCPD and unloading compliance) on fracture toughness results generated in aggressive environments

  •       To investigate the effect of K-rate on fracture toughness results generated in aggressive environments with DCPD technique

Project Outline

There is an industry requirement to generate accurate fracture toughness data in aggressive environments for engineering critical assessments. The use of clip gauges in aggressive environments limits the range of tests performed by TWI’s world-leading environmental testing laboratory. As an ever-growing demand to go deeper for oil, test environments are becoming more severe, meaning that high temperature and high-pressure autoclaves are required that cannot accommodate a clip gauge. Therefore, TWI is developing the Direct Current Potential Drop (DCPD) approach further and is performing a detailed comparison study to properly understand if the load line displacement indirect estimations are within the level of accuracy suggested by the testing in air standards.


This CRP is investigating the effect of the crack monitoring testing methods (DCPD and unloading compliance) on fracture toughness results generated in deaerated seawater under cathodic protection. In addition, the effect of K-rate in fracture toughness tests is also being investigated in the same test environment.


Industry Sectors

-      Oil and Gas


 Benefits to Industry

  •       Evaluate the degree of accuracy of DCPD compared to using clip gauges in measuring fracture toughness of steel in dearated seawater under cathodic protection;
  • Understand the effect of loading rate on the fracture toughness of steel using DCPD in the same aggressive test environment;
  •       Evaluate the importance of test measurement method and loading rates in aggressive environments, in contrast to what is specified in relevant fracture toughness testing standard in air.

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