Author
K Kumar
Other affiliations: University of North Texas, Missouri University of Science and Technology
Bio: K Kumar is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Friction stir welding & Welding. The author has an hindex of 16, co-authored 23 publications receiving 1120 citations. Previous affiliations of K Kumar include University of North Texas & Missouri University of Science and Technology.
Papers
More filters
25 Jun 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an attempt has been made to understand the mechanism of friction stir weld formation and the role of the friction stir welding tool in it by understanding the material flow pattern in the weld produced in a special experiment.
Abstract: In this investigation an attempt has been made to understand the mechanism of friction stir weld formation and the role of friction stir welding tool in it. This has been done by understanding the material flow pattern in the weld produced in a special experiment, where the interaction of the friction stir welding tool with the base material is continuously increased. The results show that there are two different modes of material flow regimes involved in the friction stir weld formation; namely “pin-driven flow” and “shoulder-driven flow”. These material flow regimes merge together to form a defect-free weld. The etching contrast in these regimes gives rise to onion ring pattern in friction stir welds. In addition to that based on the material flow characteristics a mechanism of weld formation is proposed.
418 citations
TL;DR: In this article, the authors investigated the tensile strength of the friction stir welded joint and found that there is an optimal axial load, above which the weld is defect-free, with joint strength of 84%.
119 citations
TL;DR: In this article, A356 and 6061 aluminum alloys were friction stir welded under tool rotational speed of 1000-1400 rpm and traversing speed of 80-240 mm/min, keeping other parameters same.
112 citations
TL;DR: In this paper, the phase transformation was governed by severe plastic deformation in the austenitic region followed by cooling, and the strain rate and peak temperature played key roles in controlling the prior-austenitic grain size and were correlated to the Zener-Hollomon parameter.
98 citations
TL;DR: In this paper, the influence of tool geometry on friction stir welding (FSW) of an aluminum alloy with specific reference to microstructural development, defect formation, and mechanical response was highlighted.
Abstract: In this article we highlight the results of a recent study undertaken to understand the influence of tool geometry on friction stir welding (FSW) of an aluminum alloy with specific reference to microstructural development, defect formation, and mechanical response. The welding trials were made on 4.4 mm thick sheets using tools made of die steel and having different diameters of the shoulder and the pin, and the profile of the pin. Throughout the welding operation, the rotational speed, traverse speed, and tool axial tilt were held constant at 1400 rpm, 80 mm/minute, and 0 degrees, respectively. For a shoulder diameter of 20 mm and a pin diameter of 6 mm, the severity of defects in the weld was found to be the least and the resultant tensile strength of the weld was high. For the welds that were made using a tool having a shoulder diameter of 10 mm and a pin diameter of 3 mm the tensile strength of the weld was the least since the degree of defects observed were higher.
85 citations
Cited by
More filters
TL;DR: Friction stir welding (FSW) is a widely used solid state joining process for soft materials such as aluminium alloys because it avoids many of the common problems of fusion welding as mentioned in this paper.
Abstract: Friction stir welding (FSW) is a widely used solid state joining process for soft materials such as aluminium alloys because it avoids many of the common problems of fusion welding. Commercial feasibility of the FSW process for harder alloys such as steels and titanium alloys awaits the development of cost effective and durable tools which lead to structurally sound welds consistently. Material selection and design profoundly affect the performance of tools, weld quality and cost. Here we review and critically examine several important aspects of FSW tools such as tool material selection, geometry and load bearing ability, mechanisms of tool degradation and process economics.
624 citations
25 Jun 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an attempt has been made to understand the mechanism of friction stir weld formation and the role of the friction stir welding tool in it by understanding the material flow pattern in the weld produced in a special experiment.
Abstract: In this investigation an attempt has been made to understand the mechanism of friction stir weld formation and the role of friction stir welding tool in it. This has been done by understanding the material flow pattern in the weld produced in a special experiment, where the interaction of the friction stir welding tool with the base material is continuously increased. The results show that there are two different modes of material flow regimes involved in the friction stir weld formation; namely “pin-driven flow” and “shoulder-driven flow”. These material flow regimes merge together to form a defect-free weld. The etching contrast in these regimes gives rise to onion ring pattern in friction stir welds. In addition to that based on the material flow characteristics a mechanism of weld formation is proposed.
418 citations
TL;DR: In this article, a comprehensive understanding of the fundamentals of the microstructural evolution during FSW/P has been developed, including the mechanisms underlying the development of grain structures and textures, phases, phase transformations and precipitation.
390 citations
TL;DR: In this paper, the microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature are discussed in detail in order to highlight the correlations between weld parameters used during FSW and the micro-structures evolved in the weld region and thus mechanical properties.
Abstract: The diversity and never-ending desire for a better life standard result in a continuous development of the existing manufacturing technologies. In line with these developments in the existing production technologies the demand for more complex products increases, which also stimulates new approaches in production routes of such products, e.g., novel welding procedures. For instance, the friction stir welding (FSW) technology, developed for joining difficult-to-weld Al-alloys, has been implemented by industry in manufacturing of several products. There are also numerous attempts to apply this method to other materials beyond Al-alloys. However, the process has not yet been implemented by industry for joining these materials with the exception of some limited applications. The microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature will be discussed in detail in this review. The correlations between weld parameters used during FSW and the microstructures evolved in the weld region and thus mechanical properties of the joints produced will be highlighted. However, the modeling studies, material flow, texture formation and developments in tool design are out of the scope of this work as well as the other variants of this technology, such as friction stir spot welding (FSSW).
325 citations
TL;DR: Chalmers as discussed by the authors presents a review of progress in metal physics, including the first publication of the progress in materials science journal Progress in Materials Science Vol. 9, No. 9.
Abstract: Progress in Materials Science Vol. 9. Edited by Dr. Bruce Chalmers. (Incorporating “Progress in Metal Physics”, Volumes 1–8.) Pp. 389. (London and New York: Pergamon Press, 1961.) 120s. net; 20 dollars.
295 citations