In continuum mechanics, ratcheting, or ratchetting, also known as cyclic creep, is a behavior in which plastic deformation accumulates due to cyclic mechanical or thermal stress.[1][2]
In an article written by J. Bree in 1967,[3] the phenomenon of ratcheting is described as "Unsymmetric cycles of stress between prescribed limits will cause progressive ‘creep’ or ‘ratchet(t)ing’ in the direction of the mean stress". Ratcheting is a progressive, incremental inelastic deformation characterized by a shift of the stress-strain hysteresis loop along the strain axis.[4] When the amplitude of cyclic stresses exceed the elastic limit, the plastic deformation that occurs keep accumulating paving way for a catastrophic failure of the structure. Nonlinear kinematic hardening, which occurs when the stress state reaches the yield surface, is considered as the main mechanism behind ratcheting.[5] Several factors influences the extent of ratcheting including the load condition, mean stress, stress amplitude, stress ratio, load history, plastic slip, dislocation movement, and cells deformations.[6]
The effect of structural ratcheting can sometimes be represented in terms of the Bree diagram.[7] Alternative material models have been proposed to simulate ratcheting, such as Chaboche, Ohno-Wang, Armstrong–Frederick, etc.[6]
Ratcheting is a significant effect to be considered to check permanent deformation in systems which undergoes a cyclic loading. Common examples of such repetitive stresses include sea waves, road traffic, and earthquakes.[8] Initially it was studied to inspect the permanent deformation of thin, nuclear fuel cans with an internal pressure and temperature gradient while undergoing repetitive non-zero mean stresses.[3]
References
edit- ^ Fitness-For-Service. API 579-1/ASME FFS-1, June 2016. Section 1A.83.
- ^ Suresh, S. (2004). Fatigue of Materials. Cambridge University Press. ISBN 978-0-521-57046-6.
- ^ a b Bree, J. "Elastic-plastic behaviour of thin tubes subjected to internal pressure and intermittent high-heat fluxes with application to fast-nuclear-reactor fuel elements." Journal of strain analysis 2.3 (1967): 226-238.
- ^ Roesler, J. Harders, H. Baeker, M. Mechanical Behavior of Engineering Materials: Metals, Ceramics, Polymers, and Composites, Springer (2007). ISBN 978-3-8351-0008-4.
- ^ "A Brief Discussion of Ratcheting | CAE Associates". caeai.com. Retrieved 2018-05-19.
- ^ a b Abdollahi, E.; Chakherlou, T. N. (2017-06-13). "Numerical and experimental study of ratcheting in cold expanded plate of Al-alloy 2024-T3 in double shear lap joints". Fatigue & Fracture of Engineering Materials & Structures. 41 (1): 41–56. doi:10.1111/ffe.12643. ISSN 8756-758X.
- ^ Ratcheting and Cyclic Plasticity Considerations for Code Analysis https://www.lehigh.edu/~ak01/ratcheting/ratcheting.pdf
- ^ Alonso-Marroquin, F.; Herrmann, H. J. (2004-02-06). "Ratcheting of granular materials". Physical Review Letters. 92 (5): 054301. arXiv:cond-mat/0305043. Bibcode:2004PhRvL..92e4301A. doi:10.1103/PhysRevLett.92.054301. ISSN 0031-9007. PMID 14995307. S2CID 8277773.