Mechanical Engineering Commons^™

Technical Note: Friction Factor Diagrams For Pipe Flow, Jim Mcgovern

Articles

This technical note describes diagrams of friction factor for pipe flow that have been prepared using, mainly, the equations that Lewis Moody used to prepare his famous diagram in 1944. The preparation of the new diagrams was prompted by the need for vector graphics versions that could be used for teaching purposes and that could be distributed freely to students and others under a Creative Commons Attribution-Share-Alike license. Using a structure very similar to that of Moody's diagram, variants with the Darcy friction factor and the Fanning friction factor have been prepared. In addition, variants have been prepared that include …

Rational Efficiency Of A Heat Exchanger, Jim Mcgovern, Brian P. Smyth

Articles

The authors propose a new and unique definition for the rational efficiency of a heat exchanger. This new rational efficiency is defined in terms of its sub-rational efficiencies: a heat transfer rational efficiency and a friction rational efficiency for each of the fluid systems comprising the heat exchanger. The heat transfer rational efficiency is based on the definition of a mean temperature for the heat source and a mean temperature for the heat sink and reflects the exergy supplied and the exergy received, due to heat transfer only. The friction rational efficiency for each fluid system of the heat exchanger …

Investigating Polymer-Tool Steel Interfaces To Predict The Work Of Adhesion For Demoulding Force Optimisation, Kevin Delaney, David Kennedy, Giuliano Bissacco

Conference Papers

Demoulding parts from replication tools is a critical stage of replication processes such as injection moulding and hot embossing. This challenge increases as part size decreases since components and associated replication cores become more fragile and liable to damage. Understanding interfacial characteristics between a polymer and the tool surface is critical to optimise the demoulding of such parts from replication tools. The strength of the polymer-tool interaction is characterised by the adhesion energy and is specific for a particular polymer-tool pair. It’s magnitude depends upon the tool material, the chemical structure of the polymer, the processing conditions and the surface …

Inverted Pendulum Swing Up Controller, David Kennedy, James Conlon

Conference Papers

The inverted pendulum is a classic control problem. The system is open – loop unstable and continuously wants to reach equilibrium by falling over. The system must be stabilised by means of feedback. The developed inverted pendulum system is shown in Figure 1.

In order to balance the pendulum in the inverted position the pivot must be moved continuously to correct the falling pendulum. This is similar to trying to vertically balance a broom on your hand. This interesting control problem is fundamentally the same as those involved in rocket or missile propulsion. The rocket has to balance on its …

Novel Approaches To The Analysis Of Localised Stress Concentrations In Deformed Elastomers, John Mcnamara

Doctoral

The research described here is concerned with improving finite element analysis (FEA) of rubber components subjected to dynamic loading, particularly in respect of accurate modelling of stress softening using standard software codes and phenomenological material models. The research required the design and implementation of a user subroutine capable of inclusion in standard highly nonlinear codes. Experimental methods were employed to corroborate the FEA simulations and so validate the subroutine. This was also achieved using 3D image correlation photogrammetry (ICP) and other novel experimental procedures. From this experimentation and modelling, the results for different rubber specimens and load cases were presented. …

Analyse Du Comportement Réel Et De L'Optimisation Structurelle Des Cycles De Turbines À Gaz, Alexandru Dobrovicescu, Michel Feidt, Lavinia Grosu, Jim Mcgovern, Georgiana Tirca-Dragomirescu

Conference Papers

L’article présente une étude comparative, basée sur l’analyse exégétique, de l’effet de non prise en considération du comportement réel de l’agent thermique et de l’utilisation des modèles simplifiés pour calculer les performances des cycles de turbines à gaz avec et sans récupération de chaleur. Un intérêt spécial a été réservé au processus de combustion et au transfert de chaleur dans le préchauffeur d’air. La variation des destructions et des pertes d’exergie par rapport à la variation des paramètres fonctionnels est présentée.

Some Experiences, Thoughts, Ideas And Open Questions Relating To Applied Thermodynamics, Jim Mcgovern

Articles

In this paper I present some of my thoughts and experiences relating to 'applied thermodynamics' over my career so far. I explain my interest in thermodynamics, describe some topics I have worked on, point out some questions that appear still to be open and outline some ideas for work that could be done. I describe how I was inspired to pursue the area of applied thermodynamics, with reference to a glass, opposed-piston internal combustion engine. I put my heat pump research in the late 1970s briefly into today's context. Some of my research has been in relation to compressors, which …

Characterising 3d Soft Tissue Features On Joint Surfaces, Colm O'Kane

Conference Papers

A crucial aspect of orthopaedic implant design is the prediction of surgical outcomes when the shape of a bone is necessarily altered by the addition of the implant. Matching native kinematics as closely as possible is generally considered a core aim of joint replacement surgery. The overall hypothesis behind this research is that soft tissue geometry, including cartilage thickness distribution and ligament attachment sites, influences kinematics in the knee joint. In order to enable investigation of possible links between geometry and kinematics, the ability to characterise the shape variation of the soft tissue relative to the underlying bony geometry must …

Intelligibility Of Electrolarynx Speech Using A Novel Hands-Free Actuator, Brian Madden, Mark Nolan, Ted Burke, James Condron, Eugene Coyle

Conference Papers

During voiced speech, the larynx provides quasi-periodic acoustic excitation of the vocal tract. In most electrolarynxes, mechanical vibrations are produced by a linear electromechanical actuator, the armature of which percusses against a metal or plastic plate at a frequency within the range of glottal excitation. In this paper, the intelligibility of speech produced using a novel hands-free actuator is compared to speech produced using a conventional electrolarynx. Two able-bodied speakers (one male, one female) performed a closed response test containing 28 monosyllabic words, once using a conventional electrolarynx and a second time using the novel design. The resulting audio recordings …

A Methodology Towards Comprehensive Evaluation Of Shape Memory Alloy Actuators For Prosthetic Finger Design, Kevin O'Toole

Doctoral

Presently, DC motors are the actuator of choice within intelligent upper limb prostheses. However, the weight and dimensions associated with suitable DC motors are not always compatible with the geometric restrictions of a prosthetic hand; reducing available degrees of freedom and ultimately rendering the prosthesis uncomfortable for the end-user. As a result, the search is on-going to find a more appropriate actuation solution that is lightweight, noiseless, strong and cheap. Shape memory alloy (SMA) actuators offer the potential to meet these requirements. To date, no viable upper limb prosthesis using SMA actuators has been developed. The primary reasons lie in …

Use Of Collaborative Learning Technology To Support Cross-Faculty Group Learning, Colm O'Kane, Jennifer Mcdonnell

Conference Papers

The scope of applications of computer supported collaborative learning (CSCL) has grown exponentially in recent years. This group of techniques has been found to be extremely effective as a collaborative tool to inspire scaffolding between students. It is also useful when several academic supervisors wish to view the same project work.

This paper describes the process and the motivation behind the first implementation of a campus pack-based project in Year 3 of Technological University Dublin's (DIT) BSc. in Product Design programme. Issues have been encountered in previous years with this cross-faculty managed project, but this work shows the potential that …

Development Of A Friction Testing Apparatus For Demoulding Force Prediction, Kevin Delaney, David Kennedy, G. Bissacco

Conference Papers

Friction between replication tools and replicated parts determines the force required to demould the part and also the stresses which develop in both the tool and the part during the demoulding process. Standardized equipment and procedures have been developed which strive to improve the repeatability and reproducibility of friction tests. Specific test standards, describing sled-type tests, include JIS K 7125, ISO 8295 and ASTM D1894. However these tests do not produce results which are representative of the conditions typically found within replication tools such as injection moulds or embossing tools. This paper reviews how this challenge has been addressed by …