Visco-Plastic Ratcheting Evaluation of Steel Alloys undergoing various Step-Loading Conditions by means of Isotropic-Kinematic Hardening Rules
Notice bibliographique
Résumé
<p>The present thesis develops visco-plastic constitutive equations to assess ratcheting response of several steel alloys of 304, austenitic Z2CND18.12N, U71Mn, and 316 examined under various step-loading conditions through use of the Ohno-Wang (O-W) and Ahmadzadeh- Varvani (A-V) kinematic hardening rules. The framework of hardening rules was incorporated isotropic hardening rules of Lee and Zavrel (Iso-LZ), Chaboche (Iso-C), and Kang (Iso-K) to emulate expansion of yield surfaces. The unified visco-plastic flow rule was adapted to account for the effects of stress rate and time-dependency in ratcheting assessment of steel samples. Kang's function on dynamic strain aging was employed to further evaluate time-dependent ratcheting response at operating room and elevated temperatures. This function was integrated to the dynamic recovery terms leading to drop in ratcheting magnitude and rate resulting in plastic shakedown shortly after a few stress cycles over Low-High loading sequence. The effect of the presence of peak/valley holding time resulting in static recovery was introduced into the kinematic hardening rules through inclusion of a backstress-dependent function proposed earlier by Ding. This integration enabled hardening rules to predict the excess of ratcheting strain values generated by static loading at maximum and minimum stresses over each loading cycle. Visco-plastic ratcheting evaluation of various stainless steel samples were evaluated at various stress rate, stress levels, loading steps and sequences, operating temperatures and holding times through use of the O-W and A-V hardening rules. The predicted ratcheting curves and hysteresis loops by the O-W and A-V frameworks were compared with those obtained experimentally. The predicted ratcheting curves of steel samples tested at Low-High-Low and High-Low-High loading sequences and at room and elevated temperatures revealed that both frameworks elevated ratcheting strains over Low-High loading sequence and dropped them over High-Low loading sequence. Choices of material constants and number of segments taken from stress-strain curve based on the O-W model noticeably influenced ratcheting response of steel samples. The O-W model held more backstress components, and consequently more coefficients, requiring longer Central Processing Unit (CPU) time for ratcheting evaluation than the A-V model which possessed a less complex framework with a fewer number of coefficients.</p>
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».