High-cycle Fatigue Behaviour of S460N Steel Grade Materials and Bolted Joints Processed by Laser Cutting

Abstract

Background: Prompted by the EN 1090 standard, an important evolution has been observed in recent years about steel structures execution. Laser cutting is appealing for high machining speed and precision in implementation of details with complex geometry, but requires consideration for the effects of the inherent thermal process. Objective: The present study investigates the correlations between material properties altered by the laser cutting process and behaviour of the material and of structural joints subjected to high-cycle fatigue. Method: High-cycle fatigue tests on material samples and on structural bolted connections were carried out in order to correlate the structural response with material properties. For this purpose, hardness and residual stresses were analysed in depth, from the cutting surface inward and specimens processed using different laser cutting parameters and post-annealing treatments were investigated. Results: High-cycle fatigue tests on material samples and on structural bolted connections, processed by laser cutting, show a favourable fatigue behaviour of S460N steel, despite the high values of hardness on cut surface, in agreement with Eurocode 3 fatigue category FAT160 and FAT90, respectively for base material and drilled holes. Conclusion: Structural bolted connections made of S460N steel cut by laser exhibit a favourable fatigue behaviour. Local hardness is an important indicator, favourably complemented by the residual stress distribution to understand the effects of laser cutting and correlate them with the high-cycle fatigue behaviour.