Plastic zone around fatigue cracks of pure iron in vacuum and dry air

Abstract

Specimens of pure iron were fatigued in vacuum or in dry air. The plastic zone, which was identified by the surface roughening around fatigue cracks, was investigated. Under a fixed environmental condition, the plastic zone width, Δ, at a short fatigue life is larger than that at a long fatigue life and is proportional to the corrected stress amplitude. Under different environmental conditions, however, Δ at the same stress amplitude is about 3 times larger in vacuum than in dry air, though the fatigue life is longer in the former than in the latter.