Although hydrogen embrittlement (HE) behavior has been extensively studied in bulk materials, little is known about H-related deformation and the fracture of nanograined materials. In this study, H segregation and HE mechanisms of nanograined Fe with different grain sizes are unveiled, following the employment of classical molecular dynamics simulations. The H segregation ratio increased, but the local H concentration at the grain boundaries (GBs) decreased with decreases in the grain size at a given bulk H concentration. The results demonstrate that H atoms increased the yield stress of nanograined models irrespective of the grain size. Furthermore, it is revealed that brittle fractures were inhibited, and the resistance to HE increased as the grain size decreased, due to the fact that the small-grain models had a lower local H concentration at the GBs and an enhanced GB-mediated intergranular deformation. These results are a clear indication of the utility of grain refinement to resist H-induced brittle failure.

Chromium-molybdenum steels are extensively used in manufacturing large-volume seamless hydrogen storage vessels, but they still suffer from the hydrogen embrittlement problem. In this study, electrochemical cathodic hydrogen charging is utilized to investigate the hydrogen embrittlement of 4130X steels, with emphasis on the influence of charging current density and temperature on hydrogen permeation and hydrogen embrittlement susceptibility. The hydrogen penetration rate and hydrogen diffusion coefficient of 4130X steel both increase with an increase in hydrogen-charging current density and temperature. The results demonstrate that the degree of hydrogen-induced degradation in tensile ductility is more marked with increasing hydrogen-charging current density, while the hydrogen embrittlement index exhibits a peak at a temperature of 308 K, in which brittle patterns like quasi-cleavage surfaces and crack formations occur. These findings are crucial for understanding hydrogen-induced embrittlement and determining test temperatures of hydrogen-related engineering material applications.

316LN austenitic stainless steel is extensively utilized within the domain of nuclear power, where its susceptibility to high-temperature fatigue and thermomechanical fatigue has emerged as a pivotal area of research for this material. Nevertheless, prior investigations have predominantly concentrated on axial loading outcomes, with a notable absence of studies examining its fatigue failure behavior under torsional loading conditions. The present study undertakes isothermal fatigue testing at temperatures of 450 °C, 550 °C, and 650 °C, along with thermomechanical fatigue testing across a temperature range of 350–550 °C, with strain amplitudes of 0.6%, 0.8%, and 1.2%. The findings reveal that secondary hardening observed under conditions of small deformation is primarily attributed to the enhancement of frictional stress, stemming from the accumulation of planar slip. Furthermore, as the temperature escalates, variations are observed in the intensity of the dynamic strain aging and the dislocation density within the material.

The precision of vibration signal recognition is critical in the safety monitoring of long-distance pipelines. This paper introduces an advanced methodology for signal classification that integrates wavelet denoising with particle swarm optimization...