Shell hoop prestress generated by welding

For some magnet designs it is desirable to generate a prestress, approaching the yield strength, in the shell surrounding the yoke. If that prestress can be generated by weld shrinkage, then more expensive methods of prestressing can be avoided. Shell-to-yoke friction can reduce the prestress, so it is desirable to minimize it. A quick-and-dirty test was performed to address these matters. While the scatter of the data was large, it appears that weld shrinkage can indeed generate the required prestress. The scatter was too large to give any information about the friction, however. The experiment raised more questions than it answered. 1 fig., 4 tabs