Determination of the critical socket depths of 10.9 and 8.8 grade M8 bolts with hexagonal socket form

Abstract

In this work, the effect of various socket depths of fasteners was investigated for the sake of weight reduction. M8x1.25 x 50 Full Thread (FT) bolts with 10.9 and 8.8 grade were examined in detail. The finite element simulations were performed by using SIMUFACT Forming Software. Empirical studies including fatigue and torque-tension experiments were conducted with the bolts having various socket depths. In addition, the effect of washer as used in most assembly conditions was investigated. One of the analytical methods used in the literature was also employed to compare the results obtained by the numerical and experimental methods. Based on the results obtained in this study, critical socket depths leading to the shift of failures from the thread region to head region were obtained for the investigated M8x1.25 x 50 FT bolts with 10.9 and 8.8 grades. The experimental results were compared with the analytical model and found that the analytical model underestimated the critical socket depths for both 10.9 and 8.8 grade bolts.