Studies on the experimental and simulated cyclic-plastic response of structural mild steels. (July 2021)

• Record Type: Journal Article
• Authors: Nath, Atri; Barai, Sudhirkumar V.; Ray, Kalyan Kumar
• Is Part Of: Journal of constructional steel research. Volume 182(2021)
• Publication Date: 2021-07
• Subjects: Chaboche model -- Genetic algorithm -- Mild steel -- Cyclic-plastic response; b Material constant related to isotropic hardening -- Ci, γi Material constants related to kinematic hardening evolution -- D Gage section diameter of specimens -- E Young' modulus -- f Yield function -- Ferror Error function -- J Second invariant deviatoric operator -- LG Gage length of specimens -- LT Total length of specimens -- n Number of data points -- N Number of cycles -- p Accumulated plastic strain -- ṗ Accumulated plastic strain rate -- R, R Material constants related to isotropic hardening -- Q Saturated value of the radius of the yield surface -- s Deviatoric part of the stress tensor -- t Thickness of specimens -- WG Width at gauge length for specimens -- α Deviatoric backstress tensor -- αi ith component of backstress tensor -- αi Rate of evolution of ith component of backstress tensor -- αsat Backstress for stabilized hysteresis loop -- εpL Limiting axial plastic strain in X-direction -- εmax Maximum strain in X-direction -- εmin Minimum strain in X-direction -- εa Strain amplitude -- εp Plastic strain tensor -- ε̇ Strain rate -- ε̇p Plastic strain rate tensor -- σmax Peak stress in tension to compression half cycle -- σa Stress amplitude -- σa1 Stress amplitude for the first cycle -- σasat Stress amplitude for the saturated cycle -- σemin Yield stress during load reversal for the half-cycle -- σiexp ith experimental stress data -- σimodel ith predicted stress data from the model -- σsatmax Maximum axial stress for stabilized hysteresis loops -- σult Ultimate stress -- σy0 Initial yield value -- σysat Stabilized yield stress due to isotropic hardening -- CIKH Chaboche's isotropic-kinematic hardening model -- GA Genetic algorithm -- IH Isotropic hardening -- KH Kinematic hardening -- SF Softening factor -- RO Ramberg-Osgood model; Steel, Structural -- Periodicals; Building, Iron and steel -- Periodicals; Acier de construction -- Périodiques; Construction métallique -- Périodiques; 624.1821
• DOI: 10.1016/j.jcsr.2021.106652
• Languages: English
• ISSNs: 0143-974X

Abstract

Abstract: Experimental investigations have been conducted on the cyclic-plastic response of a structural mild steel (Grade YST210) under varying strain amplitudes ( ε a ) under symmetric strain-controlled cycling. The results on the investigated YST210 steel and the reported results on four similar grades of steels (E250A, Q235, SS400, and GR345 steel) under symmetric strain-controlled cyclic loading are analyzed using a suggested approach based on Chaboche isotopic-kinematic hardening (CIKH) model. The parameters of the CIKH model are estimated from the stabilized hysteresis loops, and the obtained parameters are subsequently optimized using genetic algorithm to obtain closer predictions for the experimental cyclic-plastic response. The experimental fatigue response of YST210 steel reveals cyclic softening, and the estimated softening factor ( SF ) varies from 10% to 22% when ε a alters from 0.25% to 2%; the magnitude of SF at ε a = 2% decreases from 22% to 17.5% as the strain rate increases from 5 × 10 −4 s −1 to 5 × 10 −2 s −1 . The efficacy of the suggested approach was estimated using the maximum root mean square error ( F error ) between predictions and experimental results. For the YST210 steel at different ε a, the magnitude of F error is <4.5%, while for the other steels it is <3%. The suggested approach inherits the merit that it considers only a single set of parameters for different test conditions unlike multiple set of parameters often being used in the reported simulations. But still the results of simulations for E250A and SS400 steels depict an improvement of more than 40% over the available reports of simulations for the same steels. Graphical abstract: Unlabelled Image Highlights: Cyclic-plastic response of YST210 grade steel is presented for the first time. The steel exhibits cyclic-softening under symmetric strain-controlled loading. The results are well predicted using a proposed approach based on Chaboche model. A single set of model parameters is used to predict multiple fatigue results. Adoptability of the approach is verified for reported results on three other steels.