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(1 - 3 of 3)
- Title
- COMPENDIUM OF THERMOVISCOPLASTICITY MODELING PARAMETERS FOR MATERIALS UNDER NON-ISOTHERMAL FATIGUE.
- Creator
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O'Nora, Nathan, Gordon, Ali, University of Central Florida
- Abstract / Description
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Viscoplasticity models allow for the prediction of the inelastic behavior of materials, taking into account the rate-dependence. In order to model the response under non-isothermal conditions experienced by many components, such as those in turbomachinery, however, it is necessary to incorporate temperature-dependence. Additionally, for materials subjected to thermal shock, temperature rate-dependence is also important. The purpose of this research is to develop a method of determining...
Show moreViscoplasticity models allow for the prediction of the inelastic behavior of materials, taking into account the rate-dependence. In order to model the response under non-isothermal conditions experienced by many components, such as those in turbomachinery, however, it is necessary to incorporate temperature-dependence. Additionally, for materials subjected to thermal shock, temperature rate-dependence is also important. The purpose of this research is to develop a method of determining Chaboche viscoplasticity parameters that allows for consistent behavior with changing temperature. A quartet of candidate materials, 304 stainless steel, IN617, DS GTD-111, and Ti6242S, were chosen for their applications in turbomachinery, such as gas turbines, nuclear, and aerospace applications. The focus of this research is geared towards establishing the temperature-dependence of the constants used in the model in order to obtain more accurate modeling of non-isothermal fatigue loadings than those achieved through linear interpolation of constants at several temperatures. The goal is to be able to more accurately predict the deformation behavior of components subjected to cyclic temperature and mechanical loadings which will ultimately allow for more accurate life prediction. The effects of orientation in directionally solidified (DS) materials is also examined in order to gain insight as to the expected behavior of parameters with changing orientation.
Show less - Date Issued
- 2015
- Identifier
- CFH0004760, ucf:45383
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004760
- Title
- Application of Multiaxial Cyclic Loading for Constitutive Model and Parameter Determination of Steels.
- Creator
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Felemban, Bassem, Gordon, Ali, Moslehy, Faissal, Bai, Yuanli, Nam, Boo Hyun, University of Central Florida
- Abstract / Description
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For many candidate materials, constitutive models and their parameters are identified using uniaxial test data. Real components, however, generally operate in a multi-axial loading environments. Consequently, constitutive models deployed by uniaxial conditions may carry over to service conditions with inherit limitations. Research is proposed to determine the constitutive model constants for the creep and plasticity responses of a material via multi-axial fatigue testing which may contain...
Show moreFor many candidate materials, constitutive models and their parameters are identified using uniaxial test data. Real components, however, generally operate in a multi-axial loading environments. Consequently, constitutive models deployed by uniaxial conditions may carry over to service conditions with inherit limitations. Research is proposed to determine the constitutive model constants for the creep and plasticity responses of a material via multi-axial fatigue testing which may contain ratcheting. It is conjectured that directly regressing data under conditions that favor those of actual service use will lead to more accurate modeling under these conditions, as well as a reduced consumption of model development resources. Application of observations of multiaxial loading in the determination of constitutive modeling constants and model selection represents a paradigm shift for material characterization. Numerical simulation and experimentation are necessary for material selection for application at high temperature. The candidate material used in this study is primarily applied for structural components in high-temperature environments for steam generating systems (-) 304 stainless steel. It confers an excellent balance of ductility, corrosion resistance, and creep resistance at moderate temperatures (i.e., up to 550?C). Under service conditions, both creep and cyclic plasticity can occur under either isothermal or non-isothermal conditions. Accurate deformation modeling and life prediction of these structures only achieved with an accurate understanding of how this and other key alloys behave under complex conditions. This research conveys a proposed methodology that can be used to apply creep and plasticity constitutive models that correlate with experimental data. Several creep and plasticity models are examined to augment the accuracy of the models. These results are presented to illustrate modeling performance. Based on this idea has been determined that novel methods of measuring the accuracy of modeling be needed, as well as methods for optimizing material response under multiaxial conditions. The models are applied under service-like conditions to gain an understanding of how this and other key alloys behave under complex conditions. This research will study the complex tensile-torsion loading to determine the constitutive constants for material, and thus will decrease the number of uniaxial experiments. Additionally, combined analytical and experimental methods will be used to establish the Bree diagram for elevated temperature tensile-torsion responses. This deformation mechanism map has been useful as a design tool for materials undergoing ratcheting.
Show less - Date Issued
- 2017
- Identifier
- CFE0006875, ucf:51760
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006875
- Title
- Characterization of Anisotropic Mechanical Performance of As-Built Additively Manufactured Metals.
- Creator
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Siddiqui, Sanna, Gordon, Ali, Raghavan, Seetha, Bai, Yuanli, Sohn, Yongho, University of Central Florida
- Abstract / Description
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Additive manufacturing (AM) technologies use a 3D Computer Aided Design (CAD) model to develop a component through a deposition and fusion layer process, allowing for rapid design and geometric flexibility of metal components, for use in the aerospace, energy and biomedical industries. Challenges exist with additive manufacturing that limits its replacement of conventional manufacturing techniques, most especially a comprehensive understanding of the anisotropic behavior of these materials...
Show moreAdditive manufacturing (AM) technologies use a 3D Computer Aided Design (CAD) model to develop a component through a deposition and fusion layer process, allowing for rapid design and geometric flexibility of metal components, for use in the aerospace, energy and biomedical industries. Challenges exist with additive manufacturing that limits its replacement of conventional manufacturing techniques, most especially a comprehensive understanding of the anisotropic behavior of these materials and how it is reflected in observed tensile, torsional and fatigue mechanical responses. As such, there is a need to understand how the build orientation of as-built additively manufactured metals, affects mechanical performance (e.g. monotonic and cyclic behavior, cyclically hardening/softening behavior, plasticity effects on fatigue life etc.); and to use constitutive modeling to both support experimental findings, and provide approximations of expected behavior (e.g. failure surfaces, monotonic and cyclic response, correlations between tensile and fatigue properties), for orientations and experiments not tested, due to the expensive cost associated with AM. A comprehensive framework has been developed to characterize the anisotropic behavior of as-built additively manufactured metals (i.e. Stainless Steel GP1 (SS GP1), similar in chemical composition to Stainless Steel 17-4PH), through a series of mechanical testing, microscopic evaluation and constitutive modeling, which were used to identify a reduced specimen size for characterizing these materials. An analysis of the torsional response of additively manufactured Inconel 718 has been performed to assess the impact of build orientation and as-built conditions on the shearing behavior of this material. Experimental results from DMLS SS GP1 and AM Inconel 718 from literature were used to constitutively model the material responses of these additively manufactured metals. Overall, this framework has been designed to serve as standard, from which build orientation selection can be used to meet specific desired industry requirements.
Show less - Date Issued
- 2018
- Identifier
- CFE0007097, ucf:52883
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007097
