In this research, the new concept of ‘ BOLTED JOINT affected region (BJAR)’ is introduced to simulate dynamical behavior of BOLTED LAP JOINTs. Such regions are modeled via special elements called contact zone element (CZE) which unify the neighboring contact surfaces of substructures. These elements are different from the thin layer interface elements that form an individual layer between the two substructures. The CZEs have no specified elastic characteristics. They are thus different from the adjoining solid elements and the constitutive relation for them is prescribed in normal and shear components. The unknown parameters of the model can be identified throughout model updating with modal test data. The structure’ s frequency response function (FRF) is measured by excitation with an impact hammer and the measured responses are compared with model predictions including the CZEs’ parameters. The difference between the measured and predicted frequencies is minimized as the objective function. The optimized thickness and density are considered in addition to the elastic properties of BJAR. The competency of the proposed procedure is verified with modeling an actual structure containing a single LAP BOLTED JOINT coupling two identical structural steel beams. The results showed proper conformity with model predictions. This model can be incorporated into the commercial finite element codes to simulate BOLTED JOINTs for large and complex structures considering its accuracy and computationally efficient manner.

In this paper by employing ANSYS Workbench software and three-dimensional finite element simulation, failure analysis of hybrid bonded and BOLTED single and double LAP JOINTs with laminated composite adherends subjected to axial, shear and bending loads were performed. In order to select an appropriate and optimized element number, the convergence behavior of single and double LAP JOINTs were investigated. Then the failure study of each single and double LAP hybrid composite JOINTs for the three time dependent loading cases were performed. To demonstrate the validity and precision of the presented simulations, the obtained results were compared with the results presented in the available literatures. The results of this research indicated that, in the single LAP JOINT subjected to axial load, the replacement of hybrid bonded BOLTED JOINT instead of adhesive JOINT leads to significant increase of 56% in the load bearing capacity of the JOINT.

Two methods of photoelasticity and finite element were employed to analyze contact stresses in BOLTED JOINTs. Samples were made up of photoelastic materials. Photos were taken when samples were loaded with Polaris cope. Finite element models were analyzed using ANSYS 5.6 software. To verify the model, finite element results were compared with those of the experimental ones. The comparison led to an acceptable agreement between the two, with a correlation coefficient (R2) of 0.99. After a validation of the finite element model, the effect of number of engaged threads and different moduli of elasticity of bolt and nut were investigated, using ANSYS software. According to the results obtained, increasing the number of engaged threads in BOLTED JOINTs resulted in a decrease of load concentration percentage in the first thread, and then smoother load distribution was observed to be accomplished. Of course, the behavior of load distribution in "bolt and nut" is not the same as in "body and stud" arrangement, but in either cases, when the number of engaged threads passed 20, this didn't affect stress distribution. For body and stud, the most uniform load is obtained when the Young's modulus ratio of body and stud is in the range of 0.5-1, while this value for nut and bolt is observed to be about 0.1.

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.

This paper aims at investigating the nonlinear behavior of a system which is consisting of two free-free beams which are connected by a nonlinear JOINT. The nonlinear system is modelled as an in-extensional beam with Timoshenko beam theory. In addition, large amplitude vibration assumption is taken into account in order to obtain exact results. The nonlinear assumption in the system necessities existence of the curvature-related and inertia-related nonlinearities. The nonlinear partial differential equations of motion for the longitudinal, transverse, and rotation are derived using the Hamilton’ s principle. A set of coupled nonlinear ordinary differential equations are further obtained with the aid of Galerkin method. The frequency-response curves are presented in the section of numerical results to demonstrate the effect of the different dimensionless parameters. It is shown that the nonlinear BOLTED-LAP JOINT structure exhibits a hardening-type behavior. Furthermore, it is found that by adding a nonlinear spring the system exhibits a stronger hardeningtype behavior. In addition, it is found that the system shows nonlinear behavior even in the absence of the nonlinear spring due to the nonlocal nonlinearity assumption. Moreover, it is shown that considering different engineering beam theories lead to different results and it is found that the Euler-Bernoulli beam theory over-predict the resonance frequency of the structure by ignoring rotary inertia and shear deformation.

In this research, the influence of bolt preload on the fatigue strength of 2024-T3 aluminium alloy double LAP BOLTED JOINTs has been studied experimentally and numerically. To do so, three sets of the specimens were prepared and each of them subjected to tightening torque of 1, 2.5 and 5 N-m and then fatigue tests were conducted under various cyclic axial load levels. In the numerical method, the influence of bolt preload on the fatigue life of double LAP BOLTED JOINTs were studied using the values of fatigue notch factor obtained by volumetric approach. In order to obtain stress distribution around the notch (hole) which is required for volumetric approach, nonlinear finite element simulations were carried out. To estimate the fatigue life, the S-N curve of plain (un-notched) specimen and the fatigue notch factors obtained from volumetric method were used. The estimated fatigue life was compared with those obtained from the experiments. The investigation reveals that there is a good agreement between the life predicted by the volumetric approach and the experimental results for various specimens with different amounts of bolt preload. The volumetric approach and experimental results showed that the fatigue strength of specimens were improved by increasing the bolt preload as the result of compressive stresses which appeared around the bolt hole.

LAP JOINTs of commercially pure magnesium plates to aluminium plates (Magnesium plate on the top, and Aluminium plate, grade 1100, on the bottom side) were conducted by friction stir welding using various traveling and rotation speeds of the tool to investigate the effects of the welding parameters on the JOINT characteristics and strength. Defect-free LAP JOINTs were obtained in the welding traveling speed range of 40-80 mm/min, and rotational speed range of 1200-1600 rpm. The shear tensile strength of Mg/Al JOINTs increased as a result of decreasing the welding speed from 120 to 40 mm/min at constant rotation speed of 1600 rpm. Defects such as surface grooves, excessive flash, tunnels, and voids were observed if the JOINTs prepared out of the mentioned range. The effects of the welding parameters are discussed metallographically based on observations with optical and scanning electron microscopes.

In this study, analytical models considering different material and geometry for both single and double-LAP BOLTED JOINTs were reviewed for better understand how to select the proper model for a particular application. The survey indicates that the analytic models selected for the adhesively single or double BOLTED LAP JOINTs, as well as T, scarf, and stepped JOINTs, with linear material properties are mostly two dimensional and the studies on stress distribution and/or failure of the JOINT are performed either experimentally, analytically or by finite element method. The results seem to be generally accurate and adequate. Additionally, it was shown that any increase in the bolt-hole clearance leads to an increase in bolt rotation, as well as a decrease in bolt-hole contact area, and hence, a reduction in JOINT stiffness. Moreover, studies on hybrid JOINTs have revealed that the proper choice of adhesive material in conjunction with bolts or rivets in a JOINT, allows for significant increase in the static and fatigue strength compared to similar pure bonded JOINTs. Additionally, the results on hybrid scarf JOINTs showed that it is vital to place fasteners closer to the ends of the overLAP to suppress the peak peeling stresses and hence, delay the effects of early crack initiation in the adhesive layer. Experimental studies on fatigue behavior and strength of BOLTED JOINTs have shown that compared to clearance fit specimens, clamping force increases the fatigue life of a BOLTED JOINT. Moreover, higher tightening torque, in general, results in higher fatigue lives in BOLTED JOINTs.