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<p>This study systematically investigated the influence of loading rates and pre-cracking environment on the fracture toughness of L245 pipeline steel in a 6 MPa hydrogen gas environment. The measured fracture toughness values exhibit a dependence on the loading rate employed during testing. Notably, a critical threshold in loading rate was identified, which significantly exceeding the upper limit specified by standard testing protocols. When the loading rate remains below this critical threshold, the fracture toughness values stabilize and remain virtually unchanged. This critical loading rate can be determined by correlating the hydrogen diffusion rate, obtained from in-situ gas-phase hydrogen permeation experiments, with the crack growth rate observed in fracture toughness tests. It was found that the fracture toughness of specimen pre-cracked in air could not be determined when tested under sufficiently slow loading rates. This phenomenon is attributed to crack tip blunting for stress concentration alleviation and dislocation-mediated hydrogen trapping for mitigation of hydrogen-induced damage.</p>

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Loading Rate Threshold and Pre-cracking Environment Influence on Fracture Toughness of L245 Pipeline Steel in High-Pressure Hydrogen Environment

  • 期刊论文

  • 发表日期：

    2026年2月16日

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  • Kaiyu Zhang,
  • Wanliang Zhang,
  • Xin Liu,
  • Chengshuang Zhou,
  • Jinyang Zheng,
  • Lin Zhang

摘要

This study systematically investigated the influence of loading rates and pre-cracking environment on the fracture toughness of L245 pipeline steel in a 6 MPa hydrogen gas environment. The measured fracture toughness values exhibit a dependence on the loading rate employed during testing. Notably, a critical threshold in loading rate was identified, which significantly exceeding the upper limit specified by standard testing protocols. When the loading rate remains below this critical threshold, the fracture toughness values stabilize and remain virtually unchanged. This critical loading rate can be determined by correlating the hydrogen diffusion rate, obtained from in-situ gas-phase hydrogen permeation experiments, with the crack growth rate observed in fracture toughness tests. It was found that the fracture toughness of specimen pre-cracked in air could not be determined when tested under sufficiently slow loading rates. This phenomenon is attributed to crack tip blunting for stress concentration alleviation and dislocation-mediated hydrogen trapping for mitigation of hydrogen-induced damage.