期刊名称：International Journal of Innovative Research in Science, Engineering and Technology
印刷版ISSN：2347-6710
电子版ISSN：2319-8753
出版年度：2015
期号：MULTICON
页码：1727
出版社：S&S Publications
摘要：Ratcheting is defined as cycle by cycle accumulation of plastic strain on application of cyclic load withconstant stress amplitude and nonzero mean stress. Ratcheting occurs when a structure is subjected to cyclic loading, ifthe mean strain changes during any one loading cycle at one or more points of the structure with respect to the meanstrain induced during the preceding cycle due to inelastic material behaviour. Pressurised piping components mayencounter ratcheting when they are subjected to cyclic bending leading to a reduction in fatigue life by loss of ductility.In order to simulate ratcheting behaviour in SA 312 Type 304 LN stainless steel straight pipes of 168 mm nominalouter diameter, finite element studies were carried out under combined internal pressure and cyclic bending load.Finite element analysis were carried out using ABAQUS software by direct cyclic method. The length and averagethickness of the pipes were 2700 mm and 14.5 mm respectively. The thickness was reduced to 12 mm in the gaugelength portion of 200 mm at the centre of the pipe. The ratcheting simulation studies were carried out under threedifferent combinations of internal pressure and cyclic bending load. The internal pressure was varied in the range of 25MPa to 45 MPa. The bending load was applied in the form of cyclic displacement which was varied in the range of±25 mm to ±45 mm. The elastic-plastic response of the pipes under combined internal pressure and cyclic bendingload was simulated by using the Chaboche hardening parameters. Ratcheting strain values were obtained at differentlocations in the gauge length portion of the pipes and significant ratcheting strain was observed in the circumferentialdirection when compared to longitudinal direction. Details of the studies carried out and the results of theinvestigations are discussed in the paper.
关键词：Ratcheting; SA 312 Type 304LN stainless steel; Straight pipe; Internal pressure; Cyclic bending; Finite;element studies; Ratcheting strain
