Hydro-formed Ti bellows with the same flexibility as the welded ones

Matsue, Masaki*; Arakawa, Satoru*; Tanaka, Toshihiro*; Sawa, Soji*; Ogiwara, Norio; Suganuma, Kazuaki 

At the 3 GeV-RCS in J-PARC project, pure Ti is adopted as a material for bellows. The space available for the bellows is so narrow that the requirements are hard. To make the hydro-formed bellows like the welded ones, it is essential to bend and press the Ti plates and to keep the 2 sides facing each other in close contact. The repetition of the combination of bending (pressing) with annealing enables us to realize the close contact of Ti plates. We produced the experimental bellows with the inner diameter of 50 mm. It shows suitable performance: (1) spring rates are 1.5 N/mm (axial) and 4.0 N/mm (lateral), respectively; (2) endurance test shows the fatigue life of over than 1 million cycles with the displacement of 20 mm. Thus we have succeeded in developing the hydro-formed bellows with the same flexibility as the welded ones. Now we have completed the performance tests about the prototype of the large bellows (400 mm in a diameter), and mass production has been performed.