Papers by Keyword: Lap Joint

Abstract: In this study, use of adhesive double-sided tape in laser welded ultra-high-strength steel lap joints was evaluated. The test material in the study was abrasion resistant steel (AR400). Optical microscopy was used to investigate macroscopic morphologies of the welds and hardness profiles were measured. Static properties of the joints were evaluated by performing tensile shear strength tests. Fatigue strength of the joints were evaluated by conducting axial fatigue tests. The use of tape resulted in a gap between the welded plates which has several advantages. The gap between the plates markedly increased the width of the weld at the interface of the plates. According to the hardness measurements the hardness of the weld metal was 12% higher compared to the hardness of the AR steel base material. The gap between the plates increased the strength of the joint by up to 20%. The adhesive tape itself did not have a significant effect on the shear strength of the joints. The main advantages of using the tape were a constant air gap and its function as a fastener in welding, so that separate fasteners are not needed.

Abstract: The adhesive lap joints are extensively used in various engineering fields. Various methods were proposed to increase the strength of the lap joint. This paper presents the lap joint's characterization by applying three grades of adhesives in different material properties along the bond line. The stiffest adhesive is employed in the middle bond line, then gradually, those with a lower modulus of elasticity are placed at the ends of the lap joint. This technique reduces the stress concentration at the joining ends, so the stress distribution becomes smoother. Finite element analysis is used to model this problem in two dimensions. One of the adherent edges is applied to the fixed support, and the other end is subjected to tension. The analysis results show that the use of tri-adhesive changes the shear stress distribution along the bond line flatter and increases the strength of tri-adhesive lap joints compared to those single type adhesive applied individually.

Abstract: The requirement to join two dissimilar aluminium alloys produced with two different technological processes, extrusion and die casting, is fundamental in the automotive sector. In this research study was proposed the use of the Friction Stir Welding process to replace the traditional welding process. First of all was verified the weldability by using different process parameters and the results are reported in terms of microstructure and join aspect, which influence the Vickers microhardness. They show a suitable combination between the selected process parameters and the tool choice but also suggest to test different process conditions. Tool geometry and workpiece setup have to be redesigned. The final aim of this preliminary study is to find the best process conditions in order to proceed with components and machine tools design in the perspective of procedure industrialisation for hybrid vehicles battery pack assembly.

Abstract: The paper is focused on the effects of air gap size to mechanical properties of laser welded lap joints. Structural steel plates of 3 mm thickness were used in the laser welding experiments. The laser welding experiments were conducted at two very different energy inputs (EI) of 60 and 320 J/mm. The weld geometries were investigated using optical microscopy. The shear strength of the lap joints was evaluated by uniaxial tensile tests. Results showed that with low EI of 60 J/mm the size of air gap had significant effect on the width of the interface as the larger air gap size increased the width of the interface. At high EI of 320 J/mm, the width of the weld at the interface did not change significantly as the air gap increased. The hardness of the weld metal was greater than the hardness of the base material at both EIs. The shear strength of the joint increased significantly with low EI of 60 J/mm, as air gap size increased. The size of the air gap did not have a large effect on the shear strength of the joint with higher EI of 320 J/mm.

Abstract: This paper investigates the effect of the energy input on the microstructure evolution and mechanical properties of laser-welded dissimilar lap joints of cold work-hardened austenitic stainless steel (CW-ASS) and martensitic abrasion resistant steel (AR600). Microstructure characterization of the welds was conducted using optical microscopy and electron backscatter diffraction in a scanning electron microscope. Subsequently, the mechanical properties of the dissimilar lap joints were determined using microhardness measurements and tensile tests. The microstructure observations show that the phase structure in the fusion zone (FZ) is predominantly ferritic at both energy inputs. Besides, the solidification microstructure in the FZ resembles the cast structure composed of cellular and columnar dendrites with exhibiting elemental segregations. The hardness reaches its peak in the FZ. However, the FZ near AR600 steel exhibited higher hardness values than that near CW-ASS. The dissimilar lap joints welded at low energy input 160 J/mm achieved a higher shear strength than those welded at high energy input 320 J/mm due to the softening of the weld in the former lap joint.

Abstract: The paper investigates experimentally the usability of ultra-high-strength stainless steel and abrasion resistant steel in laser-welded sandwich structures. The fatigue and shear strength of laser joints were investigated using lap joints that were welded using two very different energy inputs. Also the effect of multiple weld tracks was investigated. The properties of separate laser welds were characterized by hardness testing and optical microscopy. Results of the hardness measurements showed that there was softened area at heat-affected-zone and weld metal of the ultra-high-strength stainless steel welds. AR steels weld metal was harder than base metal and there was softened zone in heat-affected-zone of the weld. The shear strength of tested single weld joints of the ultra-high-strength stainless steel was higher compared abrasion resistant steel single weld joints, but stronger joint can be made with multiple weld seams for abrasion resistant steel. Fatigue strength of investigated ultra-high-strength stainless steel lap joint was lower than fatigue strength of abrasion resistant steel lap joint in the low-cycle regime, but there was no practical difference in fatigue limit (10e7 cycles).

Abstract: Welding process is an efficient joining process of metals that is achieved by gas metal arc welding (GMAW) process. Localized heating during welding process can result in distortion of the welded plate. The estimation of magnitude and distribution of distortion are important to maintain the quality of products. Finite element method is implemented to investigate the distortions behavior of thin steel plate, cold rolled (SPCC) material in lap joint using GMAW process. A three-dimensional, two-step thermomechanical finite element model study was applied to analyze and evaluate distortion behavior in lap joint. The result of distortion from finite element analysis (FEA) was compared to experimental data to validate the accuracy of the method.

Abstract: SS400/SUS304 steels lap joint was applied in various industries due to flexible andbeneficial properties of these dissimilar metals joint. Therefore, an investigation for optimization ofa gas metal arc welding (GMAW) for producing the dissimilar metal lap joint should be conductedfor advancing the manufacturing industries. This research applied GMAW with various currents andspeeds to weld SS400/SUS304 lap joint and studied the relationship between the parameters andresuted joint properties. The experiment showed that an increase in the wedling current and a decreasein the welding speed affected to increase the fracture strength, the displacement of the lap joint, andthe joint hardness due to high combination of the materials at the joint interface. The uncombinedmaterials at the carbon steel/weld metal interface had the different hardness and resulted to initiatethe crack that then was propergated until the joint was broken. The weld metal showed the formationof the finer and smaller dendrite structure with increasing the welding current and decreasing thewelding speed.

Abstract: In this paper, friction stir welding (FSW) was used to weld the dissimilar A6063 Aluminum/SUS430 stainless steel lap joint with various parameter setting in a welding process. The setting included a rotating speed between 125-750 rpm, a welding speed between the 25-175 mm/min and 0-5 degrees of tool tilted angle. The welded lap joints were systematically examined in regard of the tensile-shear strength, the fracture path, and microstructure. The experimental results were concluded as follows. The decrease in the welding heat input generated from the low rotating speed and the high welding resulted in decreasing of the shear strength. A degree of a tool tilted angle affected a shear strength, and a change in the strength came from the different rate in material combination at the joint interface. The increase in a tensile-shear strength occurred for specimens produced in 0-2 degrees of a tool tilted angle while 3-5 degrees affected in decreasing. The highest shear strength of 11,870 N was obtained when the lap joint was produced by the rotating speed of 500 rpm, the welding speed of 50 mm/min and the tool tilted angle at 2 degrees. The fracture path found in the specimen with the maximum shear strength was located in the Al stirred zone, not in the joint interface.

Abstract: The goal of the present work is to investigate the validity limits and safe application range of Stress Severity Factor methodology in estimating fatigue life of aircraft fuselage joints. Fatigue tests were conducted and recorded data from aluminum alloys joints was subjected to analytical evaluation. FE models were created to obtain fasteners load distribution and determine normal stress due to secondary bending. Severity Factor method conservatively estimated fatigue life of 74% for the analyzed joints. Its robustness was verified for lap joints fatigue life estimative, but for almost all single strap joints, secondary bending effect were significant. Thus for this kind of joints, a term accounting for bending stress was added to the original severity factor formulation to increase level of safety in fatigue life estimates.