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Computational Analysis of Self-React...

Zhao, Chenyu.

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Computational Analysis of Self-Reacting Friction Stir Welding.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Computational Analysis of Self-Reacting Friction Stir Welding./
作者:	Zhao, Chenyu.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
面頁冊數:	146 p.
附註:	Source: Dissertations Abstracts International, Volume: 85-04, Section: B.
Contained By:	Dissertations Abstracts International85-04B.
標題:	Materials science. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30788414
ISBN:	9798380596961

Computational Analysis of Self-Reacting Friction Stir Welding.
Zhao, Chenyu.

Computational Analysis of Self-Reacting Friction Stir Welding. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 146 p.

Source: Dissertations Abstracts International, Volume: 85-04, Section: B.

Thesis (Ph.D.)--The Ohio State University, 2023.

Compared to conventional friction stir welding (FSW) process, self-reacting friction stir welding (SRFSW) utilizes an additional bottom shoulder that provides with significant process flexibility and capability in removing incomplete root penetration defects. However, the fundamental understanding of the weld formation mechanism during FSW/SRFSW and computational analysis method in revealing the material movement during FSW/SRFSW process is limited.In this dissertation, an integrated thermo-mechanical computational fluid dynamics (CFD) process model is presented to investigate the plasticized material flow field under thermo-mechanical effects from the perspective of the weld formation mechanism during FSW/SRFSW. Particle tracing methodology is adopted to reveal the equivalent plastic strain distribution in the wake of the tool, after the stirring effects diminished, to interpret the CFD modeling results. Different boundary conditions including shear stress boundary condition based on Coulomb-Trasca friction and velocity boundary condition are compared and evaluated form the perspective of the capability in capturing the effects of movement of shear layer on equivalent material flow field in CFD model. The significance of shear layer generation, transportation, and its timescale sticking-sliding transition state in weld formation mechanism is stressed based upon the computational analysis.A novel pressure-dependent velocity boundary condition based on Archard's wear theory is derived and put forward by treating the formation of shear layer as the wear of the workpiece. The effects of geometrical restrictions on plasticized material during the formation and transport of shear layer is emphasized in this work. Based on the understanding of the computational approach in modeling FSW/SRFSW process, the CFD model with the pressure-dependent velocity boundary condition is compared with the shear localization model for the rational and credibility in the quality weld/void defects formation mechanism, periodic tool-workpiece sliding-sticking transition state and geometrical restrictions during FSW/SRFSW process. Then a sequential precipitates microstructure evolution and yield strength prediction numerical model is developed adopting the non-isothermal histories extracted from the CFD process model as heat treatments input. The yield strength at the weld cross-sections under various welding speeds are modeled and investigated comparing to the experimental results from the literature.

ISBN: 9798380596961Subjects--Topical Terms:

543314
Materials science.
Subjects--Index Terms:

Friction stir welding

Computational Analysis of Self-Reacting Friction Stir Welding.
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520 $a Compared to conventional friction stir welding (FSW) process, self-reacting friction stir welding (SRFSW) utilizes an additional bottom shoulder that provides with significant process flexibility and capability in removing incomplete root penetration defects. However, the fundamental understanding of the weld formation mechanism during FSW/SRFSW and computational analysis method in revealing the material movement during FSW/SRFSW process is limited.In this dissertation, an integrated thermo-mechanical computational fluid dynamics (CFD) process model is presented to investigate the plasticized material flow field under thermo-mechanical effects from the perspective of the weld formation mechanism during FSW/SRFSW. Particle tracing methodology is adopted to reveal the equivalent plastic strain distribution in the wake of the tool, after the stirring effects diminished, to interpret the CFD modeling results. Different boundary conditions including shear stress boundary condition based on Coulomb-Trasca friction and velocity boundary condition are compared and evaluated form the perspective of the capability in capturing the effects of movement of shear layer on equivalent material flow field in CFD model. The significance of shear layer generation, transportation, and its timescale sticking-sliding transition state in weld formation mechanism is stressed based upon the computational analysis.A novel pressure-dependent velocity boundary condition based on Archard's wear theory is derived and put forward by treating the formation of shear layer as the wear of the workpiece. The effects of geometrical restrictions on plasticized material during the formation and transport of shear layer is emphasized in this work. Based on the understanding of the computational approach in modeling FSW/SRFSW process, the CFD model with the pressure-dependent velocity boundary condition is compared with the shear localization model for the rational and credibility in the quality weld/void defects formation mechanism, periodic tool-workpiece sliding-sticking transition state and geometrical restrictions during FSW/SRFSW process. Then a sequential precipitates microstructure evolution and yield strength prediction numerical model is developed adopting the non-isothermal histories extracted from the CFD process model as heat treatments input. The yield strength at the weld cross-sections under various welding speeds are modeled and investigated comparing to the experimental results from the literature.
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