Effects of singular and non-singular stress fields on very high cycle fatigue life of adhesive joints

Singular stress fields represent a concern during the design of mechanical connections as they could trigger cracks within the joint, under low-amplitude loads, generating failures and reducing its service life. Appropriate design plans should therefore be implemented to produce more reliable apparatus. This paper explores the effects induced by both the presence and the absence of stress singularities on the very high cycle fatigue (VHCF) performance of adhesively bonded butt joints through analytical, numerical, and experimental methods. Analytical models defined the conditions to design a stress singularity-free joint, global-local finite element descriptions studied the stress distributions in detail, and then VHCF experiments extracted S-N outcomes. The suitability of this approach is confirmed numerically while a substantial increase of the joint life is experimentally observed if the singularity is removed. Nonetheless, a non-singular configuration leads to higher scatter data compared to the original specimen configuration.