Kaushal Jha

Bio: Kaushal Jha is an academic researcher from Bhabha Atomic Research Centre. The author has contributed to research in topics: Friction stir welding & Welding. The author has an hindex of 4, co-authored 11 publications receiving 74 citations. Previous affiliations of Kaushal Jha include Homi Bhabha National Institute.

Wear-Induced Changes in FSW Tool Pin Profile: Effect of Process Parameters

Abstract: Friction stir welding (FSW) of high melting point metallic (HMPM) materials has limited application due to tool wear and relatively short tool life. Tool wear changes the profile of the tool pin and adversely affects weld properties. A quantitative understanding of tool wear and tool pin profile is crucial to develop the process for joining of HMPM materials. Here we present a quantitative wear study of H13 steel tool pin profile for FSW of CuCrZr alloy. The tool pin profile is analyzed at multiple traverse distances for welding with various tool rotational and traverse speeds. The results indicate that measured wear depth is small near the pin root and significantly increases towards the tip. Near the pin tip, wear depth increases with increase in tool rotational speed. However, change in wear depth near the pin root is minimal. Wear depth also increases with decrease in tool traverse speeds. Tool pin wear from the bottom results in pin length reduction, which is greater for higher tool rotational speeds, and longer traverse distances. The pin profile changes due to wear and result in root defect for long traverse distance. This quantitative understanding of tool wear would be helpful to estimate tool wear, optimize process parameters, and tool pin shape during FSW of HMPM materials.

Friction Stir Welding (FSW) of Aged CuCrZr Alloy Plates

Abstract: Friction Stir Welding (FSW) of Cu-0.80Cr-0.10Zr (in wt pct) alloy under aged condition was performed to study the effects of process parameters on microstructure and properties of the joint. FSW was performed over a wide range of process parameters, like tool-rotation speed (from 800 to 1200 rpm) and tool-travel speed (from 40 to 100 mm/min), and the resulting thermal cycles were recorded on both sides (advancing and retreating) of the joint. The joints were characterized for their microstructure and tensile properties. The welding process resulted in a sound and defect-free weld joint, over the entire range of the process parameters used in this study. Microstructure of the stir zone showed fine and equiaxed grains, the scale of which varied with FSW process parameters. Grain size in the stir zone showed direct correlation with tool rotation and inverse correlation with tool-travel speed. Tensile strength of the weld joints was ranging from 225 to 260 MPa, which is substantially lower than that of the parent metal under aged condition (~ 400 MPa), but superior to that of the parent material under annealed condition (~ 220 MPa). Lower strength of the FSW joint than that of the parent material under aged condition can be attributed to dissolution of the precipitates in the stir zone and TMAZ. These results are presented and discussed in this paper.

A Comparison of Different Finite Element Methods in the Thermal Analysis of Friction Stir Welding (FSW)

Abstract: Friction Stir Welding (FSW) is a novel kind of welding for joining metals that are impossible or difficult to weld by conventional methods. Three-dimensional nature of FSW makes the experimental investigation more complex. Moreover, experimental observations are often costly and time consuming, and usually there is an inaccuracy in measuring the data during experimental tests. Thus, Finite Element Methods (FEMs) has been employed to overcome the complexity, to increase the accuracy and also to reduce costs. It should be noted that, due to the presence of large deformations of the material during FSW, strong distortions of mesh might be happened in the numerical simulation. Therefore, one of the most significant considerations during the process simulation is the selection of the best numerical approach. It must be mentioned that; the numerical approach selection determines the relationship between the finite grid (mesh) and deforming continuum of computing zones. Also, numerical approach determines the ability of the model to overcome large distortions of mesh and provides an accurate resolution of boundaries and interfaces. There are different descriptions for the algorithms of continuum mechanics include Lagrangian and Eulerian. Moreover, by combining the above-mentioned methods, an Arbitrary Lagrangian–Eulerian (ALE) approach is proposed. In this paper, a comparison between different numerical approaches for thermal analysis of FSW at both local and global scales is reviewed and the applications of each method in the FSW process is discussed in detail. Observations showed that, Lagrangian method is usually used for modelling thermal behavior in the whole structure area, while Eulerian approach is seldom employed for modelling of the thermal behavior, and it is usually employed for modelling the material flow. Additionally, for modelling of the heat affected zone, ALE approach is found to be as an appropriate approach. Finally, several significant challenges and subjects remain to be addressed about FSW thermal analysis and opportunities for the future work are proposed.

Innovative potential of additive friction stir deposition among current laser based metal additive manufacturing processes: A review

Abstract: Industry 40 being the new face of manufacturing for future, metal additive manufacturing is a key element in this framework For metal additive manufacturing, laser-based additive manufacturing techniques are dominating today However, some of the inherent technical limitations associated with these techniques lead to a significant gap between the industrial requirements and the final deliverables Additive friction stir deposition is a promising alternative that is still in its early stages of development This review summarizes the vital findings in AFSD with particular emphasis on microstructure evolution and physical properties The technical limitations of laser-based AM techniques are discussed to describe the role of AFSD in their domain AFSD is discussed sequentially covering the basic physical process, features, capabilities, and limitations AFSD, being a solid-state thermomechanical process, results in a refined equiaxed microstructure with enhanced mechanical properties and no signs of porosity and residual stresses In addition to this, AFSD is capable of depositing large scale components at a high build rate that leads to cost and energy-efficient fabrication The existing limitations of the process are discussed with the scope for future improvements This critical review concludes with the suggested strategies for the widespread adoption of AFSD

Comparison among the environmental impact of solid state and fusion welding processes in joining an aluminium alloy

Abstract: The life-cycle assessment methodology was used to evaluate the environmental impact of friction stir welding of AA5754-H114 aluminium alloy sheets. Other works in literature considered the environm...