In this research, the effects of torque tightening on the stress distribution in double lap simple bolted and hybrid (bolted-bonded) joints have been investigated numerically. In order to determine the bolt clamping force value due to tightening torque in simple bolted and hybrid joints, which is necessary in numerical simulation, an experimental approach has been proposed. To do so, two kinds of joints, i.e. double lap simple and hybrid joints were prepared. To determine the bolt clamping force or pretension resulting from the torque tightening, at different applied torques, for both kinds of joints a special experimental method was designed using a steel hollow cylinder that was placed between the nut and the plate. In order to obtain the stress distribution in the joint plates for both kinds of the joints, with two different amounts of tightening torque, three-dimensional finite element models were simulated by a general finite element code. The obtained results revealed that the amounts of resultant stresses were reduced by increasing the tightening torque due to compressive stresses. Furthermore, in the hybrid joints, the stress concentration around the hole is reduced significantly. Finally, the comparison of the obtained results, confirms that the hybrid joints have better static strength than simple joints for all levels of the tightening torque. تفاصيل المقالة

In this research, the effects of notch shape on the fatigue strength of 2024-T3 aluminum alloy notched specimens have been studied using experimental and multiaxial fatigue analysis. For this purpose, four set of specimens with different notch shape were prepared and then fatigue tests were carried out at various cyclic longitudinal load levels. Load controlled fatigue tests of mentioned specimens have been conducted on a 250kN servo-hydraulic Amsler H250 fatigue testing machine with the frequency of 10Hz. A nonlinear finite element ANSYS code was used to obtain stress and strain distribution in the specimens due to the longitudinal applied loads for all kinds of specimens. Estimation fatigue lives of the specimens were carried out with several different multiaxial fatigue criteria by means of local stress and strain distribution obtained from finite element analysis, i.e. KBM, FS, Crossland, VF and WY, by means of local stress and strain values obtained from finite element simulations. Results obtained from the multiaxial analysis revealed that among the applied criteria, the Crossland’s criterion has the best accuracy for all types of the specimens. تفاصيل المقالة