Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Matthew W. Priddy

Committee Member

Linkan Bian

Committee Member

Haley Doude

Committee Member

Youssef Hammi

Committee Member

Alta Knizley

Date of Degree

8-6-2021

Original embargo terms

Complete embargo for 2 years

Document Type

Graduate Thesis - Open Access

Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Mechanical Engineering

Abstract

The overall goal of this work is to predict the mechanical response of an as-built Ti-6Al-4V directed energy deposition component by a dislocation mechanics-based internal state variable model based on the component's geometry and processing parameters. Previous research has been performed to connect additive manufacturing (AM) process parameters including laser power and scanning strategy to different aspects of part quality, such as porosity, mechanical properties, fatigue life, microstructure, residual stresses, and distortion. The lack of predictive capabilities to fully estimate residual stresses and distortion within parts produced via AM have hindered part qualification; however, modeling the AM process can aide in process and geometry optimization compared to traditional trial-and-error methods. The presence of unwanted thermally induced residual stresses and distortion can lead to tolerancing issues, reduced fatigue life, and decreased mechanical performance compared to similar components fabricated with traditional manufacturing methods such as casting and machining. A three-dimensional thermomechanical finite element model calibrated using dual-wave pyrometer thermal image datasets along with temperature- and strain rate-dependent mechanical data is utilized for this work. The purpose of this work is to understand the relationship between a component's temperature history and its resultant distortion and residual stresses.

Sponsorship

Army Research Laboratory

Available for download on Tuesday, August 15, 2023

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