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Mechanistic Modeling of Heat Transfer and Fluid Flow During Fusion-Based Additive Manufacturing of Structural Alloys.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Mechanistic Modeling of Heat Transfer and Fluid Flow During Fusion-Based Additive Manufacturing of Structural Alloys./
作者:	Knapp, Gerald L.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2021,
面頁冊數:	254 p.
附註:	Source: Dissertations Abstracts International, Volume: 83-03, Section: B.
Contained By:	Dissertations Abstracts International83-03B.
標題:	Heat transfer. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28841700
ISBN:	9798460448425

Mechanistic Modeling of Heat Transfer and Fluid Flow During Fusion-Based Additive Manufacturing of Structural Alloys.
Knapp, Gerald L.

Mechanistic Modeling of Heat Transfer and Fluid Flow During Fusion-Based Additive Manufacturing of Structural Alloys. - Ann Arbor : ProQuest Dissertations & Theses, 2021 - 254 p.

Source: Dissertations Abstracts International, Volume: 83-03, Section: B.

Thesis (Ph.D.)--The Pennsylvania State University, 2021.

This item must not be sold to any third party vendors.

During fusion-based additive manufacturing (AM) of metals and alloys, a part is built up layer-by-layer by melting the feedstock to add material only where it is needed selectively. The small volumes of material that solidify at any given time lead to significantly different material processing routes than traditional manufacturing, such as casting, forging, and welding. Additionally, differences in AM processes from more conventional metallurgical processes arise from the heat sources' size and intensity, feedstock characteristics, complex scanning strategies, and repeated heating and cooling due to layer-by-layer deposition. These differences culminate in novel and largely unquantified heat and mass transfer phenomena in the molten pool underneath the focused heat source. The molten pool's characteristics directly relate to the part microstructure and defect formation, so understanding the heat and mass transfer within the pool is key to controlling process-property relationships.While AM processes have numerous input parameters, such as heat source power, scanning speed, and hatch spacing, these do not directly correlate with the output variables of interest to the process-property relationship. Instead, heat and mass transfer within the molten pool determines the resultant solidification microstructure, fusion zone, and defects like lack-of-fusion porosity. However, test matrix or statistical approaches for investigating process parameters' effects on process outcomes obfuscates the physical mechanisms that operate inside the molten pool. It is, therefore, necessary to gain direct insight into the mechanisms at play within the molten pool under the variety of conditions that occur during the different types of AM processing.This dissertation investigates the overarching role of heat and mass transfer mechanisms in the molten pool by examining a broad range of alloys and processing conditions that fall under the umbrella of AM. Four prominent AM processes are studied; namely, laser directed energy deposition (DED-L), wire and arc additive manufacturing (WAAM), and laser and electron beam powder bed fusion (PBF-L and PBF-EB). Mechanistic models were developed to conduct virtual experiments that provided insight into the molten pool for various AM alloys in collaboration with physical experiments for model validation. Specifically, the roles of alloy composition, alloy properties, and process-specific parameters were investigated with a focus on the molten pool geometry, solidification, and solidification microstructure. Whereas physical experiments are limited in their ability to interrogate the molten pool due to the molten pool's extreme conditions and optical opacity, virtual experiments can thoroughly interrogate the spatially and temporally varying conditions within the molten pool. Furthermore, the developed mechanistic models allowed the roles of unique heat and mass transfer mechanisms in each AM process to be quantified.By quantifying the mechanisms of heat and mass transfer in the molten pool, this dissertation provides a new understanding of molten pool phenomena and where they deviate from conventional welding and joining processes. In particular, the driving forces and impact of fluid flow in the molten pool were quantified for PBF, DED, and WAAM processes, and the results highlight the importance of capturing accurate model pool geometries and temperature distributions during modeling. This understanding further enables using mechanistic modeling as an exploratory and predictive tool for AM and provides insights into the molten pool that could not have been observed experimentally. The crucial roles of surface-active elements, substrate heating, and surface deformation on the resultant molten pool geometry and solidification metallurgy indicate several areas of future research by including these variables in machine learning and statistical control models for AM. Furthermore, as numerical models are integrated into AM process, and part design workflows, this physical understanding of the impact of the underlying physics on part characteristics will allow for the informed balancing of accuracy, cost, and speed of mechanistic models.

ISBN: 9798460448425Subjects--Topical Terms:

3391367
Heat transfer.
Subjects--Index Terms:

Metallurgy

Mechanistic Modeling of Heat Transfer and Fluid Flow During Fusion-Based Additive Manufacturing of Structural Alloys.
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520 $a During fusion-based additive manufacturing (AM) of metals and alloys, a part is built up layer-by-layer by melting the feedstock to add material only where it is needed selectively. The small volumes of material that solidify at any given time lead to significantly different material processing routes than traditional manufacturing, such as casting, forging, and welding. Additionally, differences in AM processes from more conventional metallurgical processes arise from the heat sources' size and intensity, feedstock characteristics, complex scanning strategies, and repeated heating and cooling due to layer-by-layer deposition. These differences culminate in novel and largely unquantified heat and mass transfer phenomena in the molten pool underneath the focused heat source. The molten pool's characteristics directly relate to the part microstructure and defect formation, so understanding the heat and mass transfer within the pool is key to controlling process-property relationships.While AM processes have numerous input parameters, such as heat source power, scanning speed, and hatch spacing, these do not directly correlate with the output variables of interest to the process-property relationship. Instead, heat and mass transfer within the molten pool determines the resultant solidification microstructure, fusion zone, and defects like lack-of-fusion porosity. However, test matrix or statistical approaches for investigating process parameters' effects on process outcomes obfuscates the physical mechanisms that operate inside the molten pool. It is, therefore, necessary to gain direct insight into the mechanisms at play within the molten pool under the variety of conditions that occur during the different types of AM processing.This dissertation investigates the overarching role of heat and mass transfer mechanisms in the molten pool by examining a broad range of alloys and processing conditions that fall under the umbrella of AM. Four prominent AM processes are studied; namely, laser directed energy deposition (DED-L), wire and arc additive manufacturing (WAAM), and laser and electron beam powder bed fusion (PBF-L and PBF-EB). Mechanistic models were developed to conduct virtual experiments that provided insight into the molten pool for various AM alloys in collaboration with physical experiments for model validation. Specifically, the roles of alloy composition, alloy properties, and process-specific parameters were investigated with a focus on the molten pool geometry, solidification, and solidification microstructure. Whereas physical experiments are limited in their ability to interrogate the molten pool due to the molten pool's extreme conditions and optical opacity, virtual experiments can thoroughly interrogate the spatially and temporally varying conditions within the molten pool. Furthermore, the developed mechanistic models allowed the roles of unique heat and mass transfer mechanisms in each AM process to be quantified.By quantifying the mechanisms of heat and mass transfer in the molten pool, this dissertation provides a new understanding of molten pool phenomena and where they deviate from conventional welding and joining processes. In particular, the driving forces and impact of fluid flow in the molten pool were quantified for PBF, DED, and WAAM processes, and the results highlight the importance of capturing accurate model pool geometries and temperature distributions during modeling. This understanding further enables using mechanistic modeling as an exploratory and predictive tool for AM and provides insights into the molten pool that could not have been observed experimentally. The crucial roles of surface-active elements, substrate heating, and surface deformation on the resultant molten pool geometry and solidification metallurgy indicate several areas of future research by including these variables in machine learning and statistical control models for AM. Furthermore, as numerical models are integrated into AM process, and part design workflows, this physical understanding of the impact of the underlying physics on part characteristics will allow for the informed balancing of accuracy, cost, and speed of mechanistic models.
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