Dissertation submitted in fulfilment of the requirements for the degree
Master of Technology: Mechanical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2014 / The research described in this dissertation investigates the feasibility of casting inlet valves for
an internal combustion engine using Ti6Al4V alloy. The engine valves operate in an extreme
environment under high thermal cycles – this requires a material that can withstand such
exposures. Ti6Al4V is the most common titanium alloy with high temperature creep and fatigue
resistant behaviour, however, it is not all positive. Ti6Al4V alloy also yields many difficulties
with respect to processing especially when the material is cast. It is therefore important to gain
a thorough understanding of the pouring and solidification characteristics of this material.
The main focus of this work was to investigate and optimise feeding and geometrical
parameters to produce valves that are free from defects, especially porosity.
An in depth analyses of the parameters that influenced the casting quality was performed, and
it was found that casting orientation, inlet feeder geometry, initial and boundary conditions all
played a vital role in the final results. These parameters were individually investigated by
performing detailed numerical simulations using leading simulation software for each of these
cases. For each case, a minimum of ten simulations was performed to accurately determine
the effect of the alteration on casting soundness and quality. Furthermore, the relationships (if
any) were observed and used in subsequent optimised simulations of an entire investment
casting tree.
The change of geometric orientation and inlet feeder diameter and angle showed distinct
relationships with occurrence of porosity. On the other hand, alteration in the pouring
parameters, such as temperature and time, had negligible effect on occurrence or position of
porosity in the valve.
It was found that investigating individual parameters of simple geometry and then utilising
these best-fit results in complex geometry yielded beneficial results that would otherwise not
be attainable.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/1290 |
| Date | January 2014 |
| Creators | Fourie, Jecois |
| Publisher | Cape Peninsula University of Technology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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