Akademik Veri Yönetim Sistemi
Tezin Türü: Doktora
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Fen Bilimleri Enstitüsü, Türkiye
Tezin Onay Tarihi: 2023
Tezin Dili: İngilizce
Öğrenci: MUHAMMAD JUNAID ASLAM
Asıl Danışman (Eş Danışmanlı Tezler İçin): Cemil Hakan Gür
Eş Danışman: Caner Batıgün
Özet:
P91 (9Cr-1Mo) steels have received significant research attention because of their increased use at elevated temperatures, usually between 390°C and 650°C. Creep is one of the serious damage problems for high-temperature applications, thus various experimental and computational approaches are required to assist in safe operation. Since creep tests are costly and challenging to perform, it is important to establish mathematical methodologies verified by the experimental findings. It may help to better understand the creep behavior and can be merged into computational models for precise creep life predictions.
In this study, P91 steels, in as-received and welded conditions, have been subjected to several creep rupture tests at 200 MPa for the temperature range of 620oC (893K) to 650oC (923K). Welded specimens were prepared via shielded metal arc welding by using E9051-B91 electrode. The microstructure, hardness, and fracture surfaces of all specimens have been investigated by conventional characterization methods. To investigate the creep rupture behavior at a macro level, empirical correlations between various creep parameters such as strain, strain rate, time-to-rupture,
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Monkman-Grant relation, creep damage tolerance factor, etc. have been investigated. A significant contribution of this study is relating creep behavior to the creep strain energy by deriving the empirical correlations of the creep strain energy density and creep-work per unit volume. Other contributions include the modification of steady-state life correlation, steady-state creep rate and service life correlation, intermittent strain rate concept, and creep design criteria. These empirical correlations may contribute to scientific attempts to improve the creep models estimation ability.
Keywords: P91 steel, Creep Life, Creep Damage, Creep-Work per unit Volume, Creep-Energy Density