超高圧厚肉円筒の内圧疲労挙動

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Recently, very high fluid pressure is being used in. some chemical and metal working processes. The fatigue design of a very high pressure container is one of the most important works for applying these processes to industrial fields;. The object of the present work is to study experimentally the effects of cylinder material, diameter ratio, inner bore protection and mean hoop stress on the fatigue behaviour of elastic open-ended thick wall cylinders subjected to very high internal pressures. Cylinders with the diameter ratio from 1.4 to 1.8 made from 0.4%C-Ni-Cr-Mo steel (SNCM8), 18 Ni maraging steel (KMS18-17) and 1.5%C-12%Cr tool steel (SKD11) were tested. The inner bores of some monobloc cylinders were protected by an elastmer film. The compressive mean hoop stress was applied by autofrettaging and static fluid supporting. From the viewpoint of hoop stress at inner bore, the fatigue strength of the monobloc cylinders decreases with the diameter ratio. Thc protection of the bore surface with the elastmer film is effective to improve the fatigue life of the cylinders because the elastmer prevents the penetration of high pressure liquid into the fatigue crack. It seems, however, that long fatigue lives cannot be achieved with simple monobloc cylinders made from any kind of high strength material under very high cyclic internal pressure. On this point of view, prestressing is a powerful means for obtaining long life. The test results show that the fatigue life of the cylinder is significantly improved with the compressive mean hoop stress. The effect of the mean hoop stress on fatigue life becomes larger as the static strength of the cylinder materials increases. The autofrettaged cylinder has long fatigue life in comparison with nonautofrettaged one, but the effect of autofrettage is far less than that of fluid supporting. This trend may be caused by the redistribution of residual stress of the autofrettaged cylinder during pressure cycling. When the cylinders made from the hard tool steel are sufficiently strengthened in hoop direction, axial tensile stress at sealing position of inner bore causes a circumferential cracking of the cylinders.
社団法人日本材料学会の論文
1974-09-15

超高圧厚肉円筒の内圧疲労挙動

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