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.

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.

This study investigates the effect of mixed adhesive having different modulus on single Lap joint and also under peel test. The study compares these joints with that of corresponding joint containing single adhesive under two loading rate of 5 and 100 mm/min and three temperature range of room, 100oC and 200oC. Five types of adhesives were used in this assessment namely: silicon, epoxy, mixed epoxy-silicon, epoxy toughened with liquid rubber (CTBN), mixed epoxy toughened with liquid rubber (CTBN)–epoxy. Result indicated better shear strength performance by mixed epoxy-silicon adhesive joint in the single Lap shear at both loading speed followed by epoxy and liquid rubber modified epoxy joints. Similar assessment under the three temperature range also revealed better retention of shear strength for the mixed epoxy-silicon adhesive joint in particular at 200°C. This result revealed about 65 percent reduction in strength for epoxy adhesive as against 31 percent reduction for the mixed epoxy-silicon adhesive. Peel tests showed unstable peeling behavior in all joints except joint with rubber modified epoxy toughened adhesive joint. Further assessment of peel test results showed both mixed adhesives i.e. mixed epoxy-silicon, epoxy toughened with liquid rubber (CTBN), mixed epoxy toughened with liquid rubber (CTBN) -epoxy had higher peel strength compared to the other adhesive joint tested.

In this paper, influence of riveting process parameters, namely, riveting force, sheet thickness, friction coefficient and clearance fit are investigated on residual stress field and fatigue life of single riveted Lap joint of AA2024 type. According to the effect of riveting induced residual stresses on fatigue life of riveted Lap joint, these parameters are optimized to maximize the residual stress field. For this purpose, finite element simulations are performed for various combinations of the parameters according to Taguchi design of experiments. Afterwards, the parameter combination that maximize the residual stress field and the most effective parameters are obtained. The joint with maximum residual stress field is considered to have a semielliptical crack emanating from the rivet hole as an initial defect. Stress intensity factors are calculated by implementing two approaches: First, formulation overview that considers the effect of residual stress field, geometry and secondary bending, and second, the finite element method. The fatigue life of the joint is estimated using the obtained stress intensity factors and Paris-Erdogan rule. Finally, good accordance is found between results of these two approaches.

In the present research work, the reduction of peel stress in the adhesively bonded single-Lap joints has been studied. The distributions of normal and shear stresses generated in the adhesive joint were obtained using the twodimensional elasticity theory, as well as the stress-strain and strain-displacement relationships. Minimization of the peel stress was performed using the bees algorithm, during which the process variables included the adhesive and adherends thicknesses. The composite joint was loaded by a tensile force while the adherends and adhesive layers were considered to behave as isotropic materials with linear elastic properties. The results showed that based on an optimum thickness ratio of 2. 54, the magnitude of the peel stress can be reduced by 36%. As Young's moduli ratio, and consequently, the asymmetric adhesion bonding increased, the maximum amount of peeling stress decreased. Also, the increase in Young's modulus of the bottom layer led to the disruption of stress distribution at the interface of the softer adherend (top layer) and the adhesive layer, while this effect was almost absent at the other interface.

The current paper presents a robust optimum design of friction stir welding (FSW) Lap joint AA1100 aluminum alloy sheets using Monte Carlo simulation, NSGA-II and neural network. First, to find the relation between the inputs and outputs a perceptron neural network model was obtained. In this way, results of thirty friction stir welding tests are used for training and testing the neural network. Using such obtained neural network model, for the reliability robust design of the FSW, a multi-objective genetic algorithm is employed. In this way, the statistical moments of the forces, temperature, strength, elongation, micro-hardness of welded zone, grain size and welded zone thickness are considered as the conflicting objectives. The optimization process was followed by multi criteria decision making process, NIP and TOPSIS, to propose optimum points for each of the pin profiles. It is represented that some beneficial design principles are involved in FSW, which were discovered by the proposed optimization process.

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 the present study, the transient stress distribution caused by a break in the fibers of an adhesive bonding is investigated. Transient stress is a dynamic response of the system to any discontinuity in the fibers from detachment time till their equilibrium state (or steady state). To derive the governing dynamic equilibrium equations shear lag model is used. Here, it is assumed that the tensile load is supported only by the fibers. Employing dimensionless equations, initial conditions and proper boundary conditions, the differential-difference equations are solved using explicit finite difference method and the transient stress distribution is obtained in the presence of discontinuities. The present work aims to investigate the transient stress distribution in a single-Lap joint, caused by the fiber breakage in a single layer of the adhesive joint. For this purpose, the effect of different number of broken fibers (including mid fiber) in the adherend on load distribution in other intact filaments, the location of fiber breaks in the adherend, and the effect of adhesive length is studied on the overall joint behavior. The results show that a the fiber is broken away, the amount of initial shock (maximum load) into the fiber and thus the dynamic overshoot is reduced. Maximum amount of shock in the lateral fibers is broken at this point due to breakage in the thirteenth fiber maximum axial load and shock are introduce to the fourteenth fiber.