Evolution of Internal Friction in Low-Carbon Steel During Vibratory Stress Relief

Vibratory stress relief has been reported to induce crystal lattice movements, which are forms of the internal friction of a material. In this study, low-carbon steel specimens were vibrated to analyze the evolutions of their internal frictions and stress-relieving effects. Specific vibration frequencies were found to produce relatively higher internal frictions and stress-relief ratios. For a fixed vibration frequency, higher vibrational amplitudes were found to induce higher internal frictions. When vibrated for the same amount of time but at varying amplitudes, the internal frictions of the specimens either decreased with time (which indicates the effects of stress relief) or increased with time and fracturing the specimen owing to fatigue. These results indicate that the increasing of internal friction could serve as an index for fatigue crack nucleation in low-carbon steel.