Fatigue behaviour of structural steels with oxy-fuel, plasma and laser cut straight edges. Definition of Eurocode 3 FAT classes

Thermal cutting is commonly used in engineering practice to obtain the final shape of structural components, and includes oxy-fuel, plasma and laser cut technologies. The characteristics of the cut surface and the material transformations caused by these cutting methods determine the corresponding fatigue behaviour. However, in the case of thermally cut straight edges, design codes, including the Eurocode 3, provide fatigue design curves for oxy-fuel cuts, whereas emergent technologies such as plasma and laser cutting are not associated to any design curve, limiting their use in many engineering applications. This paper analyses the effect of oxy-fuel cutting, plasma cutting and laser cutting on the fatigue behaviour of cut straight edges performed on structural steels S355M, S460M, S690Q and S890Q. An experimental programme composed of 150 fatigue specimens has been completed, combining the four steels, the three thermal cutting methods and two different thicknesses (15 mm and 25 mm). The obtained S–N results have been used to estimate the corresponding Eurocode 3 FAT classes, which have been finally validated by comparing them to numerous experimental data found in the literature.