LE-7ロケットエンジン主噴射器におけるINCONEL718溶接継手の破壊靱性値および低サイクル疲労寿命向上対策

概要

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Welded joint structural failure has been observed in the LE-7 engine main injector, which is subjected to high thermal stress during an engine start and stop sequence. Failure analysis showed that these failures were caused by extremely-low-cycle fatigue due to a low number of hot-fire tests in a very high-strain condition. It was revealed that the welded joint has a considerably short low-cycle fatigue life and low fracture toughness, contrary to expectation. Based on several kinds of material tests, countermeasures such as design change of the welded structure, modification of the welding process, strengthening during non-destructive inspection and application of solution heat treatment were taken to improve welded joint strength characteristics. Using the modified main injector, a complete qualification test of LE-7 engine was performed without occurrence of failure and the first H-II rocket was launched successfully.
社団法人日本機械学会の論文
1995-08-25