Methods and systems for reducing tensile residual stresses in compressed tubing and metal tubing products produced from same
View Patent ↗Methods and systems for reducing the stress state of compressed ends of compressed tubes are disclosed. The methods and systems may provide a reduced tensile residual stress state, or even a compressive residual stress state. Tube products produced from the same are also provided.
1. A method comprising:
providing an expander comprising a head and a rod rigidly interconnected with the head;
inserting the head of the expander into a tube, the tube having a first end portion;
compressing the first end portion of the tube via a swaging die after the inserting step, thereby producing a compressed end of the tube;
removing the swaging die from the first end portion;
extracting the expander from the tube through the compressed end, after the removing step; and
moving, concomitant to the extracting step, internal surfaces of the compressed end via the expander, thereby creating a stress-relieved end of the tube.
2. The method of claim 1 , wherein, after the compressing step, the compressed end comprises a first residual stress, and wherein, after the extracting step, the stress-relieved end portion comprises a second residual stress, wherein the second residual stress is less than the first residual stress.
3. The method of claim 1 , wherein, after the compressing step, the stress-relieved end comprises a residual hoop stress of less than 0 ksi.
4. The method of claim 3 , wherein the stress-relieved end has a residual hoop stress of less than about −1.75 ksi.
5. The method of claim 1 , wherein the extracting step comprises:
applying force to the rod of the expander, wherein at least a portion of the rod of the expander is accessible after the compressing step;
wherein, prior to the applying force step, at least a portion of the rod is located outside the tube;
wherein the head is adapted to complete the moving internal surfaces step; and
wherein the inserting the head of the expander step is completed without restrictively engaging the internal surfaces of the first end portion of the tube.