Concurrent ratcheting and stress relaxation at the notch root of steel samples undergoing asymmetric tensile loading cycles

Shekarian, A.; Varvani‐Farahani, A.

doi:10.1111/ffe.12996

Cited by 11 publications

(9 citation statements)

References 26 publications

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“…These measurements closely agreed with the local strains predicted by the Chen-Jiao-Kim (CJK) model [11]. More studies [12][13][14][15][16] have been conducted to evaluate local ratcheting progress at the root of circular notches in steel samples at different stress levels. Kolasangiani et al [12] employed the Armstrong-Fredick (A-F) hardening framework [17] along with Neuber's rule to study local ratcheting and stress relaxation in the notched region.…”

Section: Introductionsupporting

confidence: 75%

Ratcheting Response of Heat-Treated Notched 1045 Steel Samples Undergoing Asymmetric Uniaxial Loading Cycles

Hatami,

Varvani-Farahani

2024

Applied Mechanics

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The present study evaluates the ratcheting response of notched cylindrical samples made of 1045 steel alloy subjected to asymmetric loading cycles using the kinematic hardening framework, coupled with Neuber’s rule. Test samples with V-shaped and semi-circular edge notches were first heat-treated under different conditions, resulting in various material hardness values at the notch root region. Local ratcheting at the notch root of samples was found to be highly dependent on the notch shape and the heat treatment conditions. HT1 samples with a lower hardness of 12 RC at the notch region possessed higher values of ratcheting, while ratcheting at the notched region for HT2 samples with 40 RC dropped to half of that in HT1 samples. The higher hardness of 50 RC at the notch edge of HT3 samples promoted the initial yield strength and the yield surface through the kinematic hardening rule with a larger translation into the deviatoric stress space as compared with samples HT1 and HT2 with 12 and 40 RC, respectively. The local ratcheting strain in sample HT1, with semi-circular notches (Kt=1.65) at a stress ratio (Smax/Sult) of 0.965, remained below 1.80% during the first hundred loading cycles. The local ratcheting decreased to 1.2% for sample HT2 and further dropped to 0.9% for sample HT3. The yield surfaces were translated consistent with the magnitude and direction of the backstress increments, as the applied loading excursion exceeded the elastic limit. Through the use of the Ahmadzadeh–Varvani (A–V) hardening rule, the predicted ratcheting values at notch roots were found to be larger in magnitudes as compared with those of experimental data, while the predicted local ratcheting through the Chaboche (CH) hardening rule fell below the experimental data. Results consistently showed that as sample hardness increased, the local ratcheting at notch roots decreased.

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Section: Introductionsupporting

confidence: 75%

Ratcheting Response of Heat-Treated Notched 1045 Steel Samples Undergoing Asymmetric Uniaxial Loading Cycles

Hatami,

Varvani-Farahani

2024

Applied Mechanics

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“…For the cyclic stress and strain ranges, Equation (11) is rewritten as:

where S is the nominal stress, e is the nominal strain, E is the modulus of elasticity,

, and

are the local stress and strain at the notch root, respectively. To predict the local stress and strain at the notch root, Neuber’s rule [ 11 ] was developed for plane stress conditions as [ 9 , 10 , 12 , 15 , 16 , 18 ]:

where subscripts A, B, C correspond to the loading turning points starting from zero to the maximum load (point A ), minimum load (point B ), and maximum load (point C ), and

is the stress concentration factor. The uniaxial nominal strain and stress range are related through the Ramberg-Osgood equation as:

where

and

correspond to the cyclic hardening coefficient and exponent, respectively.…”

Section: Modeling and Formulationmentioning

confidence: 99%

“…Substituting Equation (15) into Equations (13) and (14) resulted in Equations (16) and (17) being related to the local strain and stress components as [ 9 , 10 , 12 , 15 , 16 , 18 ]:

…”

Section: Modeling and Formulationmentioning

confidence: 99%

“…They discussed the influence of the notch size and stress levels on the local ratcheting magnitude and rate as the stress cycles increased. The coupled A-V hardening model [ 1 ] with the Neuber rule [ 11 ] was utilized to study the local ratcheting and stress relaxation at the notch vicinity of 1045 steel specimens [ 12 ]. The coupled framework governed the progressive plastic strain and stress relaxation at the notch root concurrently.…”

Section: Introductionmentioning

confidence: 99%

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Accumulation of Plastic Strain at Notch Root of Steel Specimens Undergoing Asymmetric Fatigue Cycles: Analysis and Simulation

Hatami

Varvani‐Farahani

2023

Materials

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The present study evaluates the ratcheting response at notch roots of 1045 steel specimens experiencing uniaxial asymmetric fatigue cycles. Local stress and strain components at the notch root were analytically evaluated through the use of Neuber, Glinka, and Hoffman-Seeger (H-S) rules coupled with the Ahmadzadeh-Varvani (A-V) kinematic hardening model. Backstress promotion through coupled kinematic hardening model with the Hoffman-Seeger, Neuber, and Glinka rules was studied. Relaxation in local stresses on the notched samples as hysteresis loops moved forward with plastic strain accumulation during asymmetric loading cycles was observed. Local ratcheting results were simulated through FE analysis, where the Chaboche model was employed as the materials hardening rule. A consistent response of the ratcheting values was evidenced as predicted, and simulated results were compared with the measured ratcheting data.

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“…Gallo et al 41,42 extend the SED method to simulate the creep stress/strain evolution at the notch tip as a function of time. Ratcheting and stress relaxation at the notch root of steel samples undergoing asymmetric tensile loading cycles was studied recently by Ahmadzadeh–Varvani (A‐V) 43,44 . Here, A‐V kinematic hardening rule coupled with Neuber rule is used to accommodate for local stress and strain components at the vicinity of notch root.…”

Section: Introductionmentioning

confidence: 99%

Validation of notch stress estimation schemes for low C–Mn steel

Jena

Arora

Gupta

et al. 2022

Fatigue Fract Eng Mat Struct

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The present study is aimed at validation of notch stress/strain estimation schemes such as classical Neuber, Hoffmann–Seeger, and recently developed Ince–Glinka method for nuclear piping material (low C–Mn steel). The study has considered different constraints, loading conditions, and various hole sizes to accommodate strain gradient variations and equivalent peak strains. The notch stress field evaluated using these schemes is compared with corresponding stress using elastic–plastic finite element (FE) analyses. The comparisons have brought out that the Hoffmann–Seeger scheme results in reasonably accurate assessment of stress localization nearly for all constraint geometries, loadings, and strain gradients. However, the classical Neuber scheme is more suitable for low constraint geometries and intermediate constraint geometries, whereas it results in underestimation of maximum principal stress for high constraint geometries, thereby leading to overprediction of fatigue life. Further, the suitability of energy equivalence equations of Ince–Glinka model for individual stress components has been reviewed.

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Concurrent ratcheting and stress relaxation at the notch root of steel samples undergoing asymmetric tensile loading cycles

Cited by 11 publications

References 26 publications

Ratcheting Response of Heat-Treated Notched 1045 Steel Samples Undergoing Asymmetric Uniaxial Loading Cycles

Ratcheting Response of Heat-Treated Notched 1045 Steel Samples Undergoing Asymmetric Uniaxial Loading Cycles

Accumulation of Plastic Strain at Notch Root of Steel Specimens Undergoing Asymmetric Fatigue Cycles: Analysis and Simulation

Validation of notch stress estimation schemes for low C–Mn steel

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