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A Flexible Physics-Based Lifing Method for Metals Under Creep and Thermomechanical Fatigue

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Date Issued:
2017
Abstract/Description:
This thesis focuses on the development of a flexible, physics-based life prediction approach for steels under complex conditions. Low alloy steels continue to be the materials of choice for large turbomachinery structures experiencing high temperatures for long durations. There has been significant advancement in the research of modern alloys; furthermore, these materials are continue to be utilized in boilers, heat exchanger tubes, and throttle valve bodies in both turbomachinery and pressure-vessel/piping applications. The material 2.25Cr-1Mo is studied in the present work. The resistance of this alloy to deformation and damage under creep and/or fatigue at elevated temperatures make it appropriate for structures required to endure decades of service. Also, this material displays an excellent balance of ductility, corrosion resistance, and creep strength under aggressive operating conditions. Both creep-fatigue (CF) and thermomechanical fatigue (TMF) have been the limiting factor for most turbine components fabricated from various alloys; therefore, a life prediction approach is constructed for simulating fatigue life for cases where the material is experiencing mechanical loading with thermal cycling. Flexibility is imparted to the model through its ability to emphasize the dominant damage mechanism which may vary among alloys. A material database is developed to improve and compare the model with experimental data. This database contains low cycle fatigue (LCF), creep fatigue (CF), and thermomechanical fatigue (TMF) experiments. Parameters for the model are obtained with regression fits with the support of a broad experimental database. Additionally, the cumulative damage approach, better known as Miner's rule, is used in this study as the fundamental method to combine damage mechanisms. Life predictions are obtained by the usage of a non-interacting creep-plasticity constitutive model capable of simulating not only the temperature- and rate-dependence.
Title: A Flexible Physics-Based Lifing Method for Metals Under Creep and Thermomechanical Fatigue.
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Name(s): Irmak, Firat, Author
Gordon, Ali, Committee Chair
Catbas, Necati, Committee Member
Raghavan, Seetha, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2017
Publisher: University of Central Florida
Language(s): English
Abstract/Description: This thesis focuses on the development of a flexible, physics-based life prediction approach for steels under complex conditions. Low alloy steels continue to be the materials of choice for large turbomachinery structures experiencing high temperatures for long durations. There has been significant advancement in the research of modern alloys; furthermore, these materials are continue to be utilized in boilers, heat exchanger tubes, and throttle valve bodies in both turbomachinery and pressure-vessel/piping applications. The material 2.25Cr-1Mo is studied in the present work. The resistance of this alloy to deformation and damage under creep and/or fatigue at elevated temperatures make it appropriate for structures required to endure decades of service. Also, this material displays an excellent balance of ductility, corrosion resistance, and creep strength under aggressive operating conditions. Both creep-fatigue (CF) and thermomechanical fatigue (TMF) have been the limiting factor for most turbine components fabricated from various alloys; therefore, a life prediction approach is constructed for simulating fatigue life for cases where the material is experiencing mechanical loading with thermal cycling. Flexibility is imparted to the model through its ability to emphasize the dominant damage mechanism which may vary among alloys. A material database is developed to improve and compare the model with experimental data. This database contains low cycle fatigue (LCF), creep fatigue (CF), and thermomechanical fatigue (TMF) experiments. Parameters for the model are obtained with regression fits with the support of a broad experimental database. Additionally, the cumulative damage approach, better known as Miner's rule, is used in this study as the fundamental method to combine damage mechanisms. Life predictions are obtained by the usage of a non-interacting creep-plasticity constitutive model capable of simulating not only the temperature- and rate-dependence.
Identifier: CFE0006885 (IID), ucf:51731 (fedora)
Note(s): 2017-12-01
M.S.A.E.
Engineering and Computer Science, Mechanical and Aerospace Engineering
Masters
This record was generated from author submitted information.
Subject(s): fatigue -- lifing -- creep-fatigue -- environmental-fatigue -- non-linear hardening -- MATLAB -- ANSYS
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0006885
Restrictions on Access: public 2017-12-15
Host Institution: UCF

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