Ruizhi Zhang

This paper reports the first investigation into the structural performance of lap joints fabricated from the novel nickel-free stainless steel grade EN 1.4678. For comparison, equivalent specimens with the same geometry in conventional austenitic stainless steel grade EN 1.4307 and S355 carbon steel were also tested. The observed failure modes of the 20 tested specimens included 11 by tear-out and 9 by net-section fracture. The study reveals that, overall, the novel stainless steel lap joints exhibit excellent strength and ductility, but these properties can be significantly compromised when shearing is used to cut the constituent plates. In addition to the lap joint tests, material coupon tests on standard dog-bone specimens, notched tension, flat-grooved plate and pure shear specimens were conducted to characterise the material response and fracture behaviour across a range of stress triaxialities and Lode angle parameters. This experimental work is complemented by a nonlinear finite element (FE) modelling campaign that explicitly simulates fracture. Upon validation of the FE model, extensive parametric studies are carried out over a range of end and edge distances. Based on both experimental and numerical results, the accuracy of European code predictions and literature-based design methods for the bearing failure of lap joints is assessed, considering both strength and serviceability criteria. Finally, new design equations are proposed for strength-based and deformation-based design. These new equations are demonstrated to provide more efficient, reliable, and consistent predictions than current codified methods.