Degree Type

Dissertation

Date of Award

2019

Degree Name

Doctor of Philosophy

Department

Materials Science and Engineering

Major

Materials Science and Engineering

First Advisor

Peter C. Collins

Abstract

Linear friction welding (LFW) is a solid state joining process that offers the advantage of producing aircraft components with less initial raw material. Usually, aircraft components are machined from oversized ingots to obtain the final product. This process allows the use of not-oversized ingots for welding them together to form the same final component. In addition, the inherent solid state nature of the process, eliminates all problems associated to solidification.

Various efforts have been made to evaluate such microstructure development and tensile properties associated on Ti-6Al-4V, but they have been focused on the general microstructure and not on the individual developed zones. In this study, tensile test evaluation on individual LFW zones determined yield strength of the Welded Zone (WZ) and the Thermo-mechanical Affected Zone (TMAZ) of 20 and 13% respectively greater than the Parent Material (PM) zone. Qualitative description of unindexed fraction on electron backscatter diffraction (EBSD) maps and kernel average misorientations maps (KAM) suggested a strain hardening mechanism acting. Fatigue properties are also important for aircraft components, but due to the small size of the LFW zones a conventional fatigue test was not possible. Therefore, a new ultrasonic fatigue bending test was designed using the finite element commercial package COMSOL Multiphysics®. Specific predictions on resonant frequency, shape and dimensions of specimens to evaluate individual features of a larger size than LFW such as electron beam additive manufacturing (EBAM-Ti-6Al-4V) were given. Finally, conventional fatigue tests on EBAM-Ti-6Al-4V specimens, showed the better performance of microstructure A compared with B under the perspectives of crack initiation and propagation. The final idea is to use the ultrasonic approach to evaluate the small LFW zones.

Copyright Owner

Michael Yesid Mendoza Londono

Language

en

File Format

application/pdf

File Size

124 pages

Included in

Engineering Commons

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