Ratcheting Behavior of a Titanium-Stabilized Interstitial Free Steel
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CYCLIC stressing in the elastic–plastic domain with non-zero mean stress results in the evolution of inelastic strain in structural components or in laboratory specimens. Such progressive evolution of inelastic strain is called Ratcheting or Ratcheting Effect. Ratcheting not only produces undesirable deformation but also causes additional damage in the material and thereby lowers the fatigue life of the components.[1–4] The ratcheting deformation accumulates incrementally with the applied number of cycles, and it may not cease until fracture.[5] Since many engineering components very often experience asymmetric stress cycling during service, an understanding of the response of a material under asymmetric loading condition is very important and should be addressed to accordingly for the safety assessment and fatigue life estimation of components. Recognizing the importance of mean stress effect on the performance of structural components subjected to cyclic stressing, many investigations have been carried P.S. DE, Senior Research Fellow, and P.C. CHAKRABORTI, Professor, are with the Metallurgical and Material Engineering Department, Jadavpur University, Kolkata 700032, India Contact e-mail: [email protected]. B. BHATTACHARYA, Principal Scientist, is with the Product Research Group, R&D and Scientific Services, Tata Steel Limited, Jamshedpur 831001, India. M. SHOME, Head, is with the Materials Characterisation and Joining Research Group, R&D and Scientific Services, Tata Steel Limited. D. BHATTACHARJEE, Director, is with Research Development & Technology, Tata Steel Group, 1970 CA, IJmuiden, The Netherlands. Manuscript submitted January 11, 2012. Article published online December 11, 2012 2106—VOLUME 44A, MAY 2013
out for the last three decades to understand the uniaxial and multiaxial ratcheting behaviors of different materials. In general, all these studies can be grouped into two broad categories: (1) experimental investigations on the effect of stress parameters on the ratcheting response of different materials, e.g., carbon steel,[5,6] C-Mn steel,[7,8] HSLA steel,[9,10] austenitic stainless steel,[11–18] Cr-Mo steel,[19–22] etc.; and (2) phenomenological modeling of the ratcheting behavior through modifications of the original kinematic hardening model of Armstrong and Frederick[23] developed on the basis of strain hardening and dynamic recovery of back stress. A number of such models for simulating ratcheting deformation are now available in the literature.[24–39] Investigations on the effect of mean stress on the ratcheting strain evolution are carried out in two different ways: (1) interaction between stress amplitude and mean stress, and (2) interaction between maximum stress and stress ratio. In a majority of studies, it has been reported that at constant stress amplitude, ratcheting strain evolution increases with the increasing mean stress level. This type of dependence of ratcheting strain evolution on the mean stress has been found to be true for almost all materials with different hardening–softenin
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