| 摘要 |
A radiant energy collecting/emitting element, including an absorber plate with a cylindrical bore through which a tool comprising a mandrel having lands is drawn to form helical grooves. A tube formed of a ductile metal dissimilar to the plate metal is placed within the bore and a second tool is then drawn through the tube. The second tool has an outer diameter greater than the inner diameter of the tube so that the tube is radially expanded outwardly into intimate surface contact with the bore. During expansion the material of the tube cold flows into the grooves to form lands which lock the tube against displacement relative to the plate.
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