Degree Type

Dissertation

Date of Award

2002

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

First Advisor

Palaniappa A. Molian

Abstract

Laser-based flexible fabrication (LBFF), a solid freeform fabrication (SFF) method based on laser-cladding process, was developed as an alternative to conventional machining methods for producing dies and molds. LBFF is similar to processes such as LENS with additional features including shaped beam profile, quasi-coaxial powder delivery, and functionally graded materials. It uses a high-power continuous wave (CW) CO2 laser to fabricate functional tooling, dies and molds, of low surface roughness and high dimensional uniformity. It offers flexibility in designing parts with tailored materials, and in producing parts of complicated geometry.;Functionally graded molds of TiC/Ni-alloy and TiC/Ni-alloy/H13, and functional dies of H13 steel were built up by use of LBFF. Test studies on mold relief ability, strength, and dimensional stability at elevated temperatures were conducted and compared with bench mark H13 mold in gravity casting, in injection molding, and in thermal fatigue environment, respectively. Dies were also tested in aluminum extrusion under laboratory conditions. Results showed that dies and molds fabricated by LBFF had nearly full density, smooth surface (Ra < 25 mum), and improved performance; the functionally graded molds had gradual change in elemental compositions in the transitional regions between distinct layers. In addition to experiments, analytical and finite element modeling of temperature distributions was performed to justify the use of shaped beam profiles in LBFF.

DOI

https://doi.org/10.31274/rtd-180813-13194

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Wenping Jiang

Language

en

Proquest ID

AAI3061838

File Format

application/pdf

File Size

140 pages

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