Improvement of fatigue performance by cold hole expansion. Part 2: Experimental verification of proposed model

Abstract

The model of fatigue life enhancement by means of cold hole expansion is experimentally verified exploiting the mandrelizing technological process with a rotating and non-rotating mandrel. The residual stress σ r (strain ϵ r), stress-strain curve transformation σ t and microstructural influence gD S are quantified, and the optimal residual strain ϵ r, opt yielding the maximum fatigue limit improvement is computed and experimentally confirmed. Its value provides the possibility of determining the corresponding mandrel oversize. Finally, the relative importance of the factors considered is discussed.