High strength steels (HSS) offer a unique opportunity insofar as reducing the weight of heavy-duty machinery such as trucks, trailers and agricultural machinery. Such equipment is subjected to continuous cyclic loading and fatigue failure often occurs at stress concentrations as a result of joining procedures. Previous studies have demonstrated how increasing HSS yield strength does not correspond to a proportional increase in fatigue resistance, particularly in weld joints [1]. The utilisation of bolted joints as an alternative to weld joints is proposed as a viable solution with regard to the limited fatigue performance of HSS structures. Hole-making procedures represent an essential factor in bolted connections. Different hole-making techniques - drilling, punching, laser cutting - yield different surface qualities and residual stresses which consequently impact the final fatigue limit [2]. Furthermore, the microstructure of each HSS grade will play an important role in the crack initiation and propagation [3]. A series of fatigue tests with moderately thick plates of HSS were carried out using different hole-making techniques. Different HSS grades were evaluated with yield strengths ranging from 500 to 960 MPa. Fractography analyses were performed with scanning electron microscopy. The research conducted evaluated the influence of cutting processes and microstructure on the fatigue performance of the HSS grades. [1] RFCS project FATWELDHSS, Improving the fatigue life of high strength steel welded structures by post weld treatments and specific filler material (2010). [2] Brown JD, Lubitz DJ, Cekov YC, Frank KH, Keating PB. Evaluation of influence of hole making upon the performance of structural steel plates and connections. 2007. [3] de Jesus AMP, Matos R, Fontoura BFC, Rebelo C, Simões da Silva L, Veljkovic M. A comparison of the fatigue behavior between S355 and S690 steel grades. Journal of Constructional Steel Research. 2012;79:140-50.
High Strength Steel
,Fatigue
