Atomistic study of hydrogen distribution and diffusion around a {112}<111> edge dislocation in alpha iron

Despite extensive investigations, the distribution of hydrogen around a stress singularity field is still not well understood. In this study, we conducted molecular statics (MS) analyses of the hydrogen-trap energy around a {112} edge dislocation in alpha iron. The distribution of hydrogen in crystals is generally assumed to be dominated by hydrostatic stress. However, the MS results indicate that the hydrogen-trap energy is sensitive to shear stress as well as hydrostatic stress, thus indicating that strong trap sites are distributed across a wide range on the slip plane around the dislocation core. We also performed molecular dynamics simulation of hydrogen diffusion, and revealed the anisotropic diffusion behaviour of hydrogen around the dislocation core

Atomistic study of the competitive relationship between edge dislocation motion and hydrogen diffusion in alpha iron

The interaction between a dislocation and hydrogen is considered to play an important role in hydrogen-related fractures for metals; it has been experimentally reported that hydrogen affects the dislocation mobility. These studies, however, show different macroscopic softening and/or hardening effects in iron, and the interaction between the dislocation and hydrogen remains unclear. In this study, we investigated the occurrence of interactions between a {112} edge dislocation and a hydrogen atom via the estimation of the stress-dependent energy barriers for the dislocation motion and hydrogen diffusion in alpha iron using atomistic calculations. Our results show the existence of boundary stress conditions: dislocation mobility increment (softening) occurs at a lower applied stress, dislocation mobility decrement (hardening) occurs at an intermediate stress, and no effects occur for the steady motion of a dislocation at a higher stress in this analysis condition

Influence of shear strain on the hydrogen trapped in bcc-Fe: A first-principles-based study

To advance our understanding of hydrogen-related fractures of metals and alloys, it is essential to understand the influence of lattice defects and stress on the hydrogen existence state and its concentrations. In this study, we use density functional theory and interatomic potential to clearly show that shear strain in body-centered cubic Fe yields strong hydrogen trap energy, comparable to that of volumetric strain

Renovation of Concrete Water Tank in Chiba Prefecture, Japan

This paper describes the renovation of a circular concrete water tank that had suffered significant deterioration in its dome. After a feasibility study, it was determined that the most desirable solution consisted of the replacement of the existing concrete dome with one made of structural aluminum. The key features of the construction work, including existing dome demolition and installation of the new one, are presented herein with the intent of providing a case study to engineers, contractors, and owners facing similar challenges