an investigation in to tool wear detection in friction stir welding paul fleming thomas bloodworth...
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An Investigation in to Tool Wear Detection in Friction Stir Welding
Paul FlemingThomas Bloodworth
David LammleinTracie Prater
George E. CookAlvin StraussD. M. Wilkes
David DeLappThomas Lienert
Matt Bement
Friction Stir Welding
Recently (1991) developed solid state welding technique
Uses mechanical stirring to join metals
Yields high weld strength
Can be used to join aluminum
The FSW Tool
Numerous tool designs exist Smooth Threaded Fluted
(Khaled)
FSW Tool Wear
There is extensive study of tool wear in related fields such as cutting tool wear and milling tool wear, but little for FSW
This is because of both FSW's newness and also because FSW is currently typically used on soft metals and wear is often neglible.
However this may not always be the case
FSW Tool Wear
The paper “Tool wear in the friction-stir welding of aluminum alloy 6061 20% Al2O3: a preliminary study“ investigates FSW tool wear for a threaded tool When welding the above metal, an FSW tool of 01
steel hardened to a Rockwell C hardness of 62 showed the following wear patterns
FSW Tool Wear
(Prado)
Detecting Tool Wear
This research focuses on means of discovering tool wear in FSW automatically to prevent the use of a worn tool to be allowed to proceed unnoticed.
Experimental Design
An FSW tool was constructed out of a mild tool steel to increase the wear rate
Bead on plate welds were run repeatedly and the forces incurred were recorded
Experimental Design
Show Movie
Results
After 20 welds the tool had worn to the point shown (compared with unused tool)
Worn tool on left Threads have been
worn down
Analysis
Dynamometer collects data at 1000Hz: Fx, Fy, Fz, Mz
The average force for each direction was calculated and plotted across runs
AnalysisFx
Analysis
The progression appears to be a decrease in the force experienced by the dynamometer
This trend is demonstrated in each direction
AnalysisFz
AnalysisTorque
Analysis
This decreasing force and torque can probably be directly related to the loss of threads
This decrease would then serve as a good indicator of tool wear
However, it is also shown that the forces involved vary for other reasons and make a precise estimator based on this alone impractical
Frequency Based Analysis
The frequencies in the recorded force signals could also serve as indicators of tool wear
The following shows the recorded forces for the recorded wear runs
Frequency Based Analysis
Other Possibilities
Acoustic Emissions Computer Vision
Detection of Tool Wear in FSW
This automatic detection is important for the increased industrial application of FSW, as joining of more difficult materials will become more common
Forces recorded during the weld can serve as indicators of tool wear when forces involved in welding have dropped below a certain threshold
References George E. Cook, Reginald Crawford, Denis E. Clark, and Alvin M. Strauss. Robotic friction stir welding.
Industrial Robot, 31(1):55–63, November 2004.
Terry Khaled. An outsider looks at friction stir welding. Technical report, Federal Aviation Administration, 2005.
R. A. Prado, L. E. Murr, D.J. Shindo and K.F. Soto. Tool wear in the friction stir welding of aluminum alloy 6061 + 20% Al2O3: a preliminary study. Scripta Materialia. 2001