Doctoral Dissertations


"The recent spike in energy costs has been a major contributor to propel the use of light weight alloys in the transportation industry. In particular, the automotive industry sees benefit in using light weight alloys to increase fuel efficiency and enhance performance. In this context, light weight design by replacing steel with Al and/or Mg alloys have been considered as promising initiatives. The joining of structures made of light weight alloys is therefore very important and calls for more attention. Friction Stir Spot Welding (FSSW) is an evolving technique that offers several advantages over conventional joining processes.

The fundamentals aspects of FSSW are systematically studied in this dissertation. The effects and influence of process inputs (weld parameters and tool geometry) on the process output (weld geometry and static strength) is studied. A Design of Experiments (DoE) is carried out to identify the effect of each process parameter on weld strength. It is found that the tool geometry, and in particular the pin profile has a significant role in determining the weld geometry (hook, stir zone size etc.) which in turn influences the failure mode and weld strength. A novel triangular pin tool geometry is proposed that suppresses the hook formation and produces welds with twice the static strength as those produced with conventional cylindrical pin tools. An experimental and numerical approach is undertaken to understand the effect of pin geometry on the material flow and failure mechanism of spot welds. In addition, key practical issues have been addressed such as quantification of tool life and a methodology to control tool plunge depth during welding. Finally, by implementing the findings of this dissertation, FSSW is successfully performed on a closure panel assembly for an automotive application"--Abstract, page iii.


Mishra, Rajiv S.
Krishnamurthy, K.

Committee Member(s)

Dharani, Lokeswarappa R.
Landers, Robert G.
Okamoto, Kazutaka


Mechanical and Aerospace Engineering

Degree Name

Ph. D. in Mechanical Engineering


Hitachi America


Missouri University of Science and Technology

Publication Date

Fall 2009


xvi, 182 pages

Note about bibliography

Includes bibliographical references (pages 175-181).


© 2009 Harsha Badarinarayan, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type




Subject Headings

Fracture mechanics
Friction stir welding
Welding -- Mathematical models

Thesis Number

T 9552

Print OCLC #


Electronic OCLC #


Link to Catalog Record

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