Vol.2, No 10, 2000 pp. 1299-1317
UDC 620.17:669.14(045)

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VISCOPLASTIC BEHAVIOR OF DAMAGED AISI 316H
FROM DYNAMIC EXPERIMENTS
M. Mićunović ¹, M. Radosavljević ², C. Albertini ³, M. Montagnani ^3
1 Faculty of Mechanical Engineering, Kragujevac, Yugoslavia
E-mail: mmicun@knez.uis.kg.ac.yu
² Higher Technical School , Kragujevac, Yugoslavia
³ JRC CEC, I-21020 Ispra(VA), Italy

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Abstract. The group of specimens, previously subjected either to creep or low cycle fatigue, are examined by tension at 550⁰C in the strain-rate range [10^-3, 10³] s^-1. The specimens previously treated by creep suffered various levels of creep strains while the specimens predamaged by LCF had various LCF strain critical cycle numbers (as a measure of initial life time). Evolution equations are calibrated for as- received, creep-damaged and LCF-damaged specimens, covering stress-strain strain-rate relations and accounting for strain and strain-rate hardening. The material constants entering the equations are damage-dependent. Comparisons with some empirical and microstructural models are made.
Key words: creep and LCF predamage, viscoplastic experiments, inelastic history, Rabotnov's delay, constitutive modelling, material constants identification

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VISKOPLASTIČNO PONAŠANJE ZAMORENOG ČELIKA
AISI 316H IZ DINAMIČKIH EKSPERIMENATA Dve grupe uzoraka prethodno izloženih puzanju ili niskocikličnom zamoru su ispitane zatezanjem na temperaturi od 550⁰C u širokom opsegu brzina deformacije [10^-3, 10³] s^-1. Epruvete su prethodno izložene ili puzanju pri različitim vremenima puzanja ili niskocikličnom zamoru sa različitim deformacionim amplitudama i različitim brojevima deformacionih ciklusa. Evolucione jednačine su kalibrisane za devičanski, prethodno puzajući i prethodno niskociklično zamoren materijal. Materijalne konstante koje se u ovim jednačinama pojavljuju zavise od istorije i nivoa zamora. Uporedjenja sa nekim empiričkim i mikrostrukturnim modelima su izvedena.