Robin Patrick Mooney

• Doctor of Engineering
• Manager at Trinity College Dublin

Direct measurement of heat flux and heat transfer coefficients in a Bridgman furnace is not always possible using traditional methods. This study characterised a vertical tubular Bridgman furnace using experimental data so that the estimated heat flux and heat transfer coefficients may be used in simulations of future experiments using the same fur...

Numerical model verification is a prerequisite to model validation. However, verification can be difficult if an analytical solution is not available for the normally complex problem that the numerical model is setting out to address. This article aims to formally verify a Bridgman furnace solidification front tracking model code in a steady state...

TiAl alloys are of interest to the aerospace and automotive industries (particularly for engine components) on account of their relatively low density and good mechanical properties at high temperatures. Processing routes involve melting and solidification of the alloy and require knowledge about the solidification morphology and microstructural te...

A directional solidification experiment of a Ti-Al-Nb-B-C alloy by power down method is simulated using a Bridgman furnace front tracking model. The effect of varying the dendritic growth parameters; C, the columnar dendrite growth coefficient, and n, the undercooling exponent, is investigated. A matrix of growth coefficients and undercooling expon...

The solidification of gamma TiAl alloys is of interest to the aerospace and automotive industries. A gamma TiAl multicomponent alloy: Ti-45.5Al-4.7Nb-0.2C-0.2B (at. %) has been the focus of a study to investigate the solidification conditions that led to a Columnar to Equiaxed Transition (CET) in a directional solidification experiment where tradit...

Columnar and equiaxed structures, which occur during solidification of metallic alloys, influence the texture and properties of castings, welded joints and additively manufactured components. During transient solidification, where grain refiner particles provide the predominant nucleation mechanism, a Columnar to Equiaxed Transition (CET) occurs wh...

To improve our understanding of the physical phenomena that govern the columnar-to-equiaxed transition (CET) in alloy solidification and its consequences for casting processes, experiments under microgravity condition were performed within the framework of the ESA MAP project CETSOL (Columnar-to-Equiaxed Transition in SOLidification processing). Th...

A Nucleation Progenitor Function (NPF) approach that accounts for the interdependence between nucleation and growth during equiaxed solidification is proposed. An athermal nucleation density distribution, based on undercooling, is identified as a progenitor function. A Kolmogorov statistical approach is applied assuming continuous nucleation and gr...

The Multiple Equiaxed Dendrite Interaction (MEDI) experiment was launched on the MASER-13 sounding rocket campaign to investigate polycrystalline equiaxed solidification in the transparent phase change material Neopentylgycol-30wt.%(d)Camphor. This material is of interest as an energy-storage material and as a transparent analogue system of solidif...

In-situ observation of crystal growth in transparent media allows us to observe solidification phase change in real-time. These systems are analogous to opaque systems such as metals. The interpretation of transient 2-dimensional area projections from 3-dimensional phase change phenomena occurring in a bulky sample is problematic due to uncertainty...

During casting, often a dendritic microstructure is formed, resulting in a columnar or an equiaxed grain structure, or leading to a transition from columnar to equiaxed growth (CET). The detailed knowledge of the critical parameters for the CET is important because the microstructure affects materials properties. To provide unique data for testing...

The formation of the microstructure and the grain structure during solidification is affected by buoyancy-driven flow and movement of crystals growing in the melt. To allow for pure diffusive solidification conditions, i.e., suppressing melt flow and sedimentation and floatation effects, experiments in microgravity environment were performed in the...

Unlearning is the deliberate undoing or reversal of what has been previously learned. This skill has been acknowledged in business and academia as being increasingly important for engineers in a highly changeable 21st century environment; additionally, industry have recently flagged a real-world skill deficit in graduates that can be remedied using...

Numerical models of manufacturing processes are useful and provide insight for the practitioner, however, model verification and validation are a prerequisite for expedient application. This paper details the code-to-code verification of a thermal numerical model for the Bridgman solidification process of alloys in a 2-dimensional axisymmetric doma...

Computer modelling is an important tool for investigating manufacturing processes. This paper focuses on a numerical model of the Bridgman solidification casting process, used in applications where the solidification rate and temperature gradient require careful control. A 2D axisymmetric model for transient Bridgman solidification is presented. Th...

The Bridgman furnace is widely used in industry and research, mainly because it provides a means to directionally solidify materials in a controlled manner, so that the resulting microstructure, and hence material properties, can be manipulated. This thesis details, firstly, the development and partial verification of a novel numerical Front Tracki...

Computer modelling has become an important aspect of engineering science and technology. Bespoke computer models are routinely under development and are often applied to specific manufacturing and materials processes. Solidification processes (casting, for example) is no exception and significant numbers of modelling approaches for solidification a...

Columnar to equiaxed transition (CET) was studied in a peritectic TiAl-based alloy with chemical composition Ti-45.1Al-4.9Nb-0.25C-0.2B (at.%). Solidification experiments were conducted in a Bridgman-type apparatus using cylindrical moulds made of high-purity Y2O3. The methodology containing appropriate etching and observations under flat light in...

Titanium alloys are emerging as a candidate to replace nickel superalloys in the aerospace industry due to their very low density and exceptional mechanical properties at high temperatures. Casting these materials can be difficult due to the tendency of molten titanium to react with other elements, and due to a lack of understanding of the material...

The Bridgman furnace is widely used in industry and research. This paper outlines a working onedimensional model for tracking the columnar solidification front in a Bridgman furnace where the pulling velocity, and hence front position, change as a function of time. The front tracking model is applied to a fixed grid of control volumes using an expl...

On 26th March 2010 the MAXUS-8 sounding rocket was launched from the Esrange Space Center in Sweden. As part of the Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS) project, a solidification experiment was conducted on a Ti-45.5at.%Al-8at.%Nb intermetallic alloy in a module on this rocket. The experiment wa...

A review of the MAXUS 8 sounding rocket microgravity experiment to investigate solidification structures in a Ti-Al-Nb intermetallic alloy is presented. The experiment was part of the Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS) EU FP6 project. Key objectives were to investigate columnar and equiaxed so...

This paper details the control of a pilot scale laboratory heating and ventilation system. The system is represented in 2x2 multi-input, multi-output (MIMO) form. A process reaction curve identification technique was used to model (in first order lag plus delay - FOLPD - form) the flow process and temperature process portions of the system, over a...

This paper details the control of a pilot scale laboratory heating and ventilation system (VVS-400 product, Instrutek Ltd., Norway). The system is represented in 2×2 multi-input, multi-output (MIMO) form. A process reaction curve identification technique was used to model (in first order lag plus delay - FOLPD - form) the flow process and temperatu...

This dissertation is concerned with the estimation and control of a laboratory heating and ventilation system (Instrutek VVS-400). The system is a 2x2 multi-input multi-output process (MIMO). It has been shown that simple techniques such as the ultimate cycle method do not provide adequate control of the process. The system was interfaced with a PC...