Identification of damage stages in bolted metallic joints for different joint geometries and tightening torques using statistical analysis

The main parameters controlling the structural behavior of bolted joints are the tightening torque (T) and the joint geometry such as the edge distance (e) to the bolt hole diameter (D) ratio (e/D) and the joint width (W) to the hole diameter ratio (W/D). In the first part of this study, the effects of W/D and T, with a constant value of e/D (e/D = 3), have been studied experimentally. Three values of W/D (2.25, 3, and 3.75) with six values of T (0, 10, 15, 20, 25, and 30 N m) have been chosen to construct 18 assemblies. Experimental results highlighted the impact of W/D, and T, on the different failure stages of bolted double-lap metallic joints. In the second part of this study, analysis of variance has been adopted to analyze the effects of T and W/D in addition to the effect of e/D which has been studied previously by the authors. The present experimental results showed that the value of applied load at which the sticking failure occurred increased by increasing the tightening torque up to T = 25 N m for all values of W/D. However, the other stages of failure were slightly affected by the value of T. The results obtained from the analysis of variance identified that there is no clear effect of W/D and e/D on the sticking failure load. However, their effects are markedly clear for other stages of failure.