The effect of residual stress on hydrogen embrittlement in a type of steel

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: The effect of residual stress on hydrogen embrittlement in a type of steel

ارائه دهنده: Provider: Mohammad reza Parsaeiyan

اساتید راهنما: Supervisors: Rahman Seyfi (Ph. D) AmirHossein Mahmoudi (Ph. D)

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: (Ph. D) Ali Alavi Nia (Ph. D) - Hashem Mazaheri

زمان و تاریخ ارائه: Time and date of presentation: 2025

مکان ارائه: Place of presentation: 55

چکیده: Abstract: Given the increasing importance of hydrogen as a clean energy carrier, hydrogen embrittlement remains one of the principal obstacles to the safe use of this gas, since it degrades the mechanical properties of materials and shortens component service life. This study was undertaken to examine the effects of shot peening and grinding on hydrogen embrittlement, with particular attention to the roles of residual stress and surface roughness. Specimens were first sanded and then subjected either to shot peening—to introduce compressive residual stresses—or to grinding—to induce tensile residual stresses. They were subsequently charged with hydrogen via an electrochemical technique, and their mechanical behavior was assessed by tensile testing. The results showed that shot peening alone does not reliably improve resistance to hydrogen embrittlement; its effectiveness depends on the magnitude of the induced residual stress, the resulting surface roughness, and the specimen geometry. By contrast, the ground specimens—whose surface roughness was improved by approximately 3.5 fold compared to the as sanded condition and which displayed greater dimensional uniformity in the gauge section—exhibited superior performance. In the worst case for ground specimens, ultimate tensile strength decreased by 5.34%, plastic strain fell by 9%, and total elongation dropped by 7%. In the best case, grinding produced virtually no loss in ultimate tensile strength, an 11.85% increase in plastic strain, and a 10% increase in total elongation. Shot peened specimens suffered from dimensional variations of 0.02–0.05 mm in the gauge length, which adversely affected their behavior. These findings underscore the critical importance of surface characteristics in mitigating hydrogen embrittlement. Finally, hydrogen diffusion and its impact on hydrostatic stresses were simulated using Fick’s law within the Abaqus finite element environment. Although this approach can model hydrogen embrittlement and its effects, significant discrepancies between simulation and experimental data were observed, owing to inherent errors and limitations in the simulation methodology.