The influence of pre-straining on the high-cycle fatigue performance of two hot-dip galvanised car body steels

The high-cycle fatigue behaviour of a hot-dip galvanised ferritic-pearlitic steel and of a hot-dip galvanised Ti-alloyed high-strength interstitial-free steel was investigated. The testing mode was constant displacement, fully reversed plane bending. Both test materials were tested unstrained and 10% uniaxially pre-strained. Pre-straining improves the high-cycle fatigue behaviour of both steels, probably due to strain-hardening of the matrix. Some relations that have been put forward in attempts to mathematically describe the high-cycle fatigue range of the S-N curve (by Stromeyer, Weibull, Heywood, Basquin) were compared to the experimental data. The Basquin relation was found to agree best.