Date on Master's Thesis/Doctoral Dissertation

5-2019

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, PhD

Committee Chair

Hsu, Keng

Committee Member

Atre, Sundar

Committee Member

Berfield, Thomas

Committee Member

Chou, Kevin

Author's Keywords

additive manufacturing; 3d-printing; ultrasonic energy; acoustic energy; microstructure; mechanical properties

Abstract

Additive manufacturing or 3d printing is the process of constructing a 3-dimensional object layer-by-layer. This additive approach to manufacturing has enabled fabrication of complex components directly from a computer model (or a CAD model). The process has now matured from its earlier version of being a rapid prototyping tool to a technology that can fabricate service-ready components. Development of low-cost polymer additive manufacturing printers enabled by open source Fused Deposition Modeling (FDM) printers and printers of other technologies like SLA and binder jetting has made polymer additive manufacturing accessible and affordable. But the metal additive manufacturing technologies are still expensive in terms of initial system cost and operating costs. With this motivation, this dissertation aims to develop and study a novel metal additive manufacturing approach called Acoustoplastic Metal Direct-Write (AMD) that promises to make metal additive manufacturing accessible and affordable. The process is a voxel based additive manufacturing approach which uses ultrasonic energy to manipulate and deposit material. This dissertation demonstrates that the process can fabricate near-net shape metal components in ambient conditions. This dissertation investigates two key phenomenon that govern the process. The first phenomenon investigated is ultrasonic/acoustic softening. It is the reduction in yield stress of the metals when being deformed under simultaneous application of ultrasonic energy. A detailed analysis of the stress and microstructure evolution during ultrasonic assisted deformation has been presented in this dissertation. Crystal plasticity model modified on the basis of microstructure analysis has been developed to predict the stress evolution. The 2nd phenomenon investigated is ultrasonic energy assisted diffusion that enables the bonding of voxels during the AMD process. High resolution Transmission Electron Microscopy (HRTEM) and Energy Dispersive Spectroscopy (EDS) analysis has been used to quantify this phenomenon and also distinguish the process mechanics from other foil or sheet based ultrasonic joining processes.

Available for download on Sunday, November 10, 2019

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