D.H. Lammlein PhD Dissertation - Vanderbilt University

Figure 159: Average tool shank temperature obtained via thermal camera over the
steady state portion of welds made using the wide probe tool.
Figure 160 shows the typical temperature history of the tool shank surface during
welding. Temperature on the tool shank surface increases gradually as the probe is
plunged into the material and then more rapidly as the shoulder contact condition is
established. When the shoulder is at the desired position and the traverse is triggered, the
temperature increases less rapidly. The issue of secondary heating can be seen during the
weld proper in the presented temperature charts. The tool must pass over the weld
initiation site, which has been previously subjected to the weld thermal environment, to
complete a full circumferential weld. A steady state temperature is never reached and
temperature increases throughout the weld cycle. In the presented experiment, this climb
in temperature did not adversely affect weld quality. However, the temperature increase
over the circumference of the weld is significant in small diameter pipes and could affect
weld quality under other conditions. During welding of butted plates a similar problem
can be encountered when the tool nears the end of the plate and the edge of the plate
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