P. Nagaraj

Investigation on Joining of Aluminum and Mild Steel by Friction Stud Welding

Joining of dissimilar metals has various automotive, aerospace, nuclear, chemical, and cryogenic applications. The present study focuses on friction stud welding of aluminum and mild steel. Experiments had been conducted by varying the process parameters and the strength of the friction welded joints was evaluated. Experimental results show that the speed of rotation, friction time, and axial shortening distance have significant effect on the impact strength of the welded joints. The dissipation of frictional heat from the weld center results in temperature gradient across the welded joint, causing different zones with different microstructures. Scanning electron microscope (SEM) micrograph reveals the presence of three distinctive regions in the heat-affected zone, namely, fully plasticized deformed zone, partially deformed zone, and unaffected base metal zone. The microhardness values were measured across the welded joint. At the interfacial region, there is an increased plastic deformation. This is due to the rise in heat input during friction stage and applied upsetting load in the forging stage. Consequently, there is an increase in hardness at the interfacial region of the welded joint.

NUMERICAL SIMULATION ON JOINING OF CERAMICS WITH METAL BY FRICTION WELDING TECHNIQUE

The joining of ceramic and metals can be done by different techniques such as ultrasonic joining, brazing, transient liquid phase diffusion bonding, and friction welding. Friction Welding is a solid state joining process that generates heat through mechanical friction between a moving workpiece and a stationary component. In this article, numerical simulation on thermal analysis of friction welded ceramic/metal joint has been carried out by using Finite Element Analysis (FEA) software. The finite element analysis helps in better understanding of the friction welding process of joining ceramics with metals and it is important to calculate temperature and stress fields during the welding process. Based on the obtained temperature distribution the graphs were plotted between the lengths of the joint corresponding to the temperatures. To increase the wettability, aluminium sheet was used as an interlayer. Hence, numerical simulation of friction welding process is done by varying the interlayer sheet thickness. Transient thermal analysis had been carried out for each cases and temperature distribution was studied. From the simulation studies, it is found that the increase in interlayer thickness reduces the heat affected zone and eventually improves the joint efficiency of alumina/aluminum alloy joints.

FINITE ELEMENT BASED THERMAL MODELING OF FRICTION WELDING OF DISSIMILAR MATERIALS

Friction welding is a solid state joining process of joining either similar or dissimilar materials. Joining of ceramic/metal joints by friction welding has opened up new possibilities in many engineering applications. In the present work, thermal modeling of friction welding process has been carried out. Using Finite Element Approach (FEA), analytical solutions were arrived for different ceramic/metal combinations. The temperature distributions of cylindrical surfaces of the alumina and the metals are found by means of 1D heat transfer assumption considering the effect of convection. In the thermal analysis, interfacial temperature and thermal conductivity of the material play a significant role. Based on the obtained temperature distribution the graphs are plotted between the length of the joint and the temperatures. Thus the knowledge of the temperature joint distribution could be helpful in predicting the thermal cycle of the process, microstructure evolution and residual stress formation. Thus the obtained graph helps to study and predict the temperature distribution of both the materials.

EVALUATION OF BENDING STRENGTH IN FRICTION WELDED ALUMINA/MILD STEEL JOINTS BY APPLYING FACTORIAL TECHNIQUE

Joining of metal with ceramics has become significant in many applications, because they combine properties like ductility with high hardness and wear resistance. By friction welding technique, alumina can be joined to mild steel with AA1100 sheet of 1mm thickness as interlayer. In the present work, investigation of the effect of friction time on interlayer thickness reduction and bending strength is carried out by factorial design. By using ANOVA, a statistical tool, regression modeling is done. The regression model predicts the bending strength of welded ceramic/metal joints accurately with ± 2% deviation from the experimental values.