Strength Of Dissimilar Joints Research Articles

Dynamic growth model of Fe2Al5 during dissimilar joining of Al to steel using the variable polarity cold metal transfer (VP-CMT)

Further development of the car lightweight in automotive industry significantly depends on the reliability of the Al/steel dissimilar joint, since more and more Al alloy parts are used in the car manufacturing. It has been proved that the Al/steel dissimilar joint strength can be effectively increased when the intermetallic compound (IMC) growth, especially the Fe2Al5 layer thickness, is controlled at certain level. Because the Fe2Al5 is the dominant phase of the entire IMC layer in the Al/steel dissimilar joint, and cracks usually initiate at this location when damage is conducted. Therefore, for the automotive industry assembly line, the prediction model monitoring the Fe2Al5 layer thickness of each Al/steel weld seam is desired to ensure the dissimilar joint quality and reliability. In the present research, a numerical dynamic growth model based on element diffusion laws is established to calculate the IMC layer thickness of Fe2Al5 phase during the variable polarity cold metal transfer (VP-CMT) welding of aluminum to steel in the function of welding heat input and location. To build up effective connection between the welding heat input and the actual temperature history of Al/steel interface, a finite element analysis (FEA) model is customized for the present VP-CMT process. The Fe2Al5 layer thickness calculation results are further validated using electron back-scattered diffraction (EBSD) characterization under scanning electron microscopy (SEM), confirming a 2.3 % deviation between the model prediction and actual layer thickness.

Shear force analysis of Resistance Spot Welding of Similar and Dissimilar Material: copper and carbon steel

Resistance spot welding (RSW) is a complicated process, which involves the interaction of electrical, thermal, mechanical, and metallurgical phenomena. In this research we used two types of material (UNS G10050 carbon steel and UNS C10010 copper) and welded them in similar and dissimilar condition with four variables welding current, pressure, squeeze time and welding time. The results of the tensile-shear force were analyzed statistically by the Design of experiments (DOE) utilizing Taguchi method. Tensile-shear test used for counting the strength of the joint, maximum strength was found in similar joining condition for carbon steel, also it is interesting to note that the strength of dissimilar joint is stronger than copper joining in similar condition.

Improvement in tensile strength of Mg/Al alloy dissimilar friction stir welding joints by reducing intermetallic compounds

There has been an increasing demand for joining Al to Mg in transportation vehicles to reduce weight further. However, it is difficult to manufacture high performance Mg/Al dissimilar joints due to the formation of massive intermetallic compounds (IMCs) during welding. In the present study, AZ31B Mg and 6061 Al were friction stir welded with a high joint efficiency by reducing the IMCs formation. Microstructural observations were conducted by using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and the results showed that the content of IMCs reduced from about 31.79% to 7.8%. Mechanical test results showed the tensile strength of joint increase from 92 MPa to 168 MPa. The findings provide an alternative to improve Mg/Al dissimilar joint strength.

The influence of notching and mixed-adhesives at the bonding area on the strength and stress distribution of dissimilar single-lap joints

With the rapid development of new engineering materials, multi-material structures are now widely used to achieve desired performances instead of conventional ones. The increased use of dissimilar adherends such as composites and metals for joining structural parts in aerospace, maritime and civil and transport structures in the past decades make it essential to find methods to improve the performance of this type of joints due to the potential for lightweight products. The first aim of this research is to minimise peak stress concentration by introducing notches in the bonding area to increase the performance of single-lap joints with epoxy adhesive. This is done by utilising the finite element method (FEA) in Abaqus® software to model a series of single lap joints (SLJ) with various notch designs to find the optimum. Experimental tests are carried out to verify the designs.The optimal design is used then to model various SLJs with mono-adhesive and mixed-adhesives to optimise single-lap joints with dissimilar adherends. The novel geometrical modification reduces peak stresses significantly in the joints with dissimilar adherends, which leads to smaller asymmetric stress distribution along bond-line. The experimental results show significant improvement in the dissimilar joint strength. Compared with using a single material as the adhesive, it is found that using both epoxy and polyurethane as adhesive offers a higher failure load. This can be explained as the polyurethane adhesive provides more uniform stress distribution by transferring stress concentration to the interior part of the overlap length.

Effect of laser welding process parameters on dissimilar joints of AISI 316 and nickel 201

Abstract The dissimilar butt welding of nickel 201 and AISI 316 was investigated using 4 kW CO2 laser welding machine. The effects of welding power (2580 - 3420 W), welding speed (450 - 1150 mm/min), focal position (-1 to 0 mm), beam angle (84 - 96 degrees) and Beam offset (0 - 0.2 mm) on the welded bead geometry like depth of penetration (DP), bead width (BW), area of penetration (AP) and heat input (HI) were analyzed with Response Surface Methodology (RSM). The central composite design was used for this experimental plan. Mathematical equations were formed to find the required heat input and weld profile responses dissimilar butt welding process. Output responses reflect the results for mathematical models within the range of process parameters used. Numerical optimisation technique was used to identify the optimal condition region of all this laser welding process. It helps to achieve better process parameter combination for the controlled responses of this process. Depth of penetration is the most important output response to achieve the good dissimilar joint. The welding power and welding speed are the two factors which influencing more on the strength of dissimilar joint even though all the other three factors are involving. The beam angle does not show any considerable change on bead width and Fusion Zone Area (FZ) and also there is no significant influence of the beam offset on bead width. An optimization results were confirmed by experiments to validate values of the process parameters values found from RSM. In microstructure studies some delta ferrite is seen in the interdendritic region and also the solidification shows columnar grains. The tensile test results the fracture in the base metal which proves that the weld strength is good as expected

The influence of parameters of friction stir welding modes on the mechanical properties of corrosion-resistant alloys with steel

The article discusses promising technological methods used for the formation of joints of corrosion-resistant alloys with steels by friction stir welding (FSW). The dependences of the strength characteristics modes on the FSW (angle of inclination of the tool, displacement of the tool from the contact line of the welded samples) are presented. The subject of the analysis is the design of the edges of the parts to be welded in the case of FSW and the stage-by-stage analysis of the process of producing butt joints of corrosion-resistant alloys with steels, taking into account the parameters of welding modes. The article analyzes the factors affecting the strength of dissimilar joints of OT4-1 (VT1) alloys and St3 (12H18N10T) steels, made with the help of a FSW. The influence of the geometry of the prepared edges of parts on the strength of welded joints has been studied. The results of strength tests are presented, design and technological methods are recom- mended, aimed at improving the conditions and activating the formation of adhesive dissimilar joints.

Optimization of TIG Welding Process Parameters for X70-304L Dissimilar Joint Using Taguchi Method

The optimization of mechanical properties of the welded joints requires a statistical approach such as Taguchi experimental designs associated with experimental techniques and laboratory characterizations. The aim of this work is to propose a method of optimization of the mechanical performances of a TIG dissimilar welding of two grades of steels: a high strength low alloy steel X70 and an austenitic stainless steel 304L. The experimental designs were chosen according to the Taguchi method L9. The metallurgical characterization includes optical microscopy, SEM microscopy, EDX analyses and mechanical tests to establish a relationship between welding parameters, microstructures and mechanical behavior in different zones of a dissimilar weld joint. The results showed that the hardness is more strongly related to microstructural evolution than tensile strength of dissimilar joint. It was found that gas flow is the main significant TIG welding parameter affecting dissimilar weld characteristics.

軟鋼とアルミ合金の異材スポット溶接部の強度に及ぼす溶接条件の影響

軟鋼とアルミ合金の異材スポット溶接部の強度に及ぼす溶接条件の影響

Effect of Tool pin Profile and Axial Force on Tensile Behavior in Friction Stir Welding of Dissimilar Aluminum Alloys

Aluminium alloys generally has low weldability by traditional fusion welding process. The development of the Friction Stir Welding (FSW) has provided an alternative improved way of producing aluminium joints, in a faster and reliable manner. FSW process has several advantages, in particular the possibility to weld dissimilar aluminium alloys. This study focuses on the behavior of tensile strength of dissimilar joints of AA6351-T6 alloy to AA5083-H111 alloy produced by friction stir welding was analysed. Five different tool pin profile such as Straight Square (SS), Tapered Square (TS), Straight Hexagon (SH), Straight Octagon (SO) and Tapered Octagon (TO) with three different axial force (1tonne, 1.5tonne, 2 tonne) have been used to weld the joints. The effect of pin profiles and axial force on tensile properties and material flow behaviour of the joint was analyzed and it was found that the straight square pin profile with 1.5 tonne produced better tensile strength then other tool pin profile and axial force.

Controlling of Grain Boundary Structure and Interface Structure of Advanced Materials and their Joints

Strength of nanostructured Cr-B and Cr-Ni alloys prepared by sputtering was related with grain size. The alloying of B or Ni to Cr reduces the grain size of the alloys. The increase in volume of grain boundaries or amorphous phase induced by alloying elements causes the departure of strength of nanostructured Cr alloys from the values estimated by the Hall-Petch relation. The formation and microhardness of Cr or Ti base amorphous alloys could be discussed by the chemical bonding between elements. The strength of dissimilar joints was dominated by the thickness and structure of the interfacial reaction zone between SiC and metal. The formation of interfacial reaction zone is discussed by the change of chemical potentials of elements between ceramics and metal.