RESULTS OF A ROUND ROBIN ON STRETCH ZONE WIDTH DETERMINATION*

Abstract

Abstract— ‐A round robin on experimental stretch zone width (SZW) measurement was conducted. The SZW of eight different materials showing an SZW range of 5 to 200 μm was measured by evaluating a set of micrographs. The round robin was carried out by 14 participants from different firms and institutes. The standard deviation of the experimental SZW measurement was found to be in a range of smaller than 75% of the stretch zone average SZW. For 90% of the micrographs the standard deviation of SZW remains in a range smaller than 35% of SZW. This scatter range was not significantly influenced by the experience of the participants in measuring the individual SZW, the materials tested and the magnitude of the SZW itself. The SZW results determined in this round robin match well with a theoretical SZW determination using the recently developed blunting line equation including strain hardening: SZW = 0.4 dn* J/E.