Morgridge D.,Rolls-Royce |
Evans H.P.,University of Cardiff |
Snidle R.W.,University of Cardiff |
Yates M.K.,Aerospace Engine Controls
Tribology Transactions | Year: 2011
This article describes a hydrodynamic and elastohydrody-namic lubrication analysis of film generation at the rotating contact between the gear tooth end faces and bearing block thrust face seal in a high-pressure aerospace fuel pump. The analysis includes the effect of tilt of the face seal together with elastic deformation and surface roughness of the contacting components. The results of the analysis show that relatively thin hydrodynamic films are generated and that the most likely mode of lubrication is that of mixed lubrication in which part of the load is carried by direct contact at asperity junctions. It is shown that a small improvement in film formation might be obtained by careful profiling or crowning of the end faces of the gears. © Society of Tribologists and Lubrication Engineers.
Collins S.T.,Aerospace Engine Controls |
Bradley J.A.,Applied Research Associates Transportation Sector |
Yassine A.A.,University of Illinois at Urbana - Champaign
IEEE Transactions on Engineering Management | Year: 2010
This paper uses network analysis (NA) to study task interactions in the product development process (PDP) at a small engineering company (Smallcomp). We examine Smallcomps organizational changes by comparing its PDP network properties at two points in time. The analysis identifies patterns of centralization, role specialization, and formalized control. This validates themes from organizational behavior and quality management literature regarding how organizations learn from experience, grow in size, and control their process variation. It demonstrates several insights to manage the PDP as both a second (i.e., effectively executing) and third order (i.e., highlighting underlying premises and assumptions) form of organizational control. First, reducing variation in task outputs is an understandable approach to controlling a PDP. However, it is important to reduce variation in task inputs as well. Second, tasks have varying roles and burdens in terms of how they share information with other tasks in the PDP. Companies seeking to support multiple concurrent projects must align their organizational resources to the distribution of labor created by the information flow among PDP tasks. Finally, an NA metric called Simmelian ties can measure effective concurrency in a PDP by identifying both valuable and ineffective iteration among groups of tasks. © 2006 IEEE.
Agency: GTR | Branch: EPSRC | Program: | Phase: Research Grant | Award Amount: 5.87M | Year: 2011
Manufacturing automation is an expanding field concerned with the delivery of high-value engineering technologies and services globally. The highest value areas of automation relate to the more difficult to automation applications, for example many occurring in aerospace and precision automotive applications. Industry sources estimate that in a typical aerospace manufacturing plant the costs associated with manual operations and the inspect-adjust-rework activity could cost millions of pounds across the UK. Automation in various forms has the potential to reduce this inefficiency but also has the potential to do great damage to quality if applied incorrectly. Whilst automation has been applied across many sectors of industry, the spectrum of applications has rarely pushed the boundaries of research. Safe and limited solutions are often the norm. The high value manufacturing industries have applied limited automation because of the highly skilled nature of the finishing, inspection and assembly work inherent in the manufacturing processes. These processes are difficult to automate because of minor variation in components that influence interaction between processing equipment and component being processed. In addition, parts are often made from expensive materials, with many parts requiring careful handling in a high added value state (e.g. fan blades). Whilst humans can accommodate variation at certain levels they often introduce variation by virtue of being human (e.g. through lack of concentration). These high value industries need an advanced kind of automation that delivers the precision of computer controlled machinery with the adaptability of a human operator, but with 24/7 capability and 100% quality performance and at reasonable cost and operational speed. When the variation in the product caused by variation in human performance has been removed by deployment of intelligent automated systems, it will be possible to gather better data about design for manufacture and feed this back into product development in a systematic manner.Intelligent Automation is a convergence of human-machine modelling, digital manufacturing, knowledge generation and learning with intelligent devices. The aim is to develop a generic process and product modelling and deployment capability that can radically impact on current limitations experienced within industries that rely on substantial input from human skill, expertise and adaptability.This EPSRC Centre for Innovative Manufacturing in Intelligent Automation will have a platform activity and two closely related and integrated research themes. The platform activity will emphasise Fast Track projects for Early Win outcomes closely linked to the Tier 1 industrial partner expectations. Adventure projects will also be undertaken, aimed at more speculative high risk research. A small amount of Policy and Standards influencing work will be carried out. The first flagship research theme is: Modelling and Deployment for Right First Time Manufacturing, where extensive computer based modelling of intelligent automation systems will be undertaken to establish greater confidence during the design phase through to digital deployment and on to real deployment and operation. The second flagship theme is: Humans and Intelligent Automation Systems, where human skill is examined and how this influences difficult to automate industrial processes/tasks. The area of humans and robots sharing the same work space will also be investigated.
Greve H.,University of Maryland University College |
Chen L.-Y.,Ohio Aerospace Institute |
Fox I.,Aerospace Engine Controls |
McCluskey F.P.,University of Maryland University College
Proceedings - Electronic Components and Technology Conference | Year: 2013
Low temperature transient liquid phase sintering (LT-TLPS) pastes, based on copper-tin, have been developed for high temperature attachment of wide band gap semiconductor dice to substrates for power electronics. The LT-TLPS attach process enables pressure-less joining at low temperatures in air. An organic binder has been used to form a stencil-printable paste that prevents oxidation of the copper and tin particles, before and during sintering. Shear samples have been manufactured consisting of copper dummy dice and copper substrates joined with a stencil printed layer of one of three copper-tin sinter pastes (viz. Cu60Sn, Cu50Sn, and Cu40Sn) having copper concentrations of 40%, 50%, and 60% by weight respectively. A high-temperature shear test setup has been designed to determine the shear strength of the three pastes at temperatures of 25°C, 125°C, 250°C, 400°C, and 600°C. It has been shown that the joints remain strong up to the melting point of the dominant intermetallic phase of the joint. Cu50Sn joints showed no reduction in shear strength up to 400°C, while Cu40Sn pastes showed no reduction in shear strength up to 600°C. This demonstrates that pressure-less LT-TLPS pastes can be used to form high-temperature resilient joints at low process temperatures in reasonably short process times. © 2013 IEEE.
Yates M.K.,Aerospace Engine Controls
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2015
Twin pinion gear pumps are used widely in industrial hydraulics and as fuel-delivery pumps for aero engines. The kinematics of the pumping action leads to high-flow rates into and out of the meshing gears, and at the high speeds used with aerospace fuel pumps cavitation can occur. One-dimensional 'lumped parameter' models are often used to analyse this type of pump. These methods rely on an accurate description of the volume trapped by the meshing teeth and the flow areas during the meshing cycle. Typically, multiple computer-aided design models have to be created to calculate these values during the meshing cycle. This paper presents a mathematical method for calculating these parameters based on a parametric definition of the gear and inlet and outlet porting. Green's theorem is used to allow line integrals around the periphery of the tooth spaces to be used to calculate the volumes and flow areas. Winding numbers are used to calculate the inflow and outflow areas that are formed by the intersection of the trapped volume and the side area porting. The method is validated against computer-aided design model data. This method is well suited for incorporation in an optimisation algorithm since the geometry is defined parametrically. © IMechE 2014.
Cree A.M.,University of Plymouth |
Devlin M.,Loughborough University |
Critchlow G.,Loughborough University |
Hirst T.,Aerospace Engine Controls
Transactions of the Institute of Metal Finishing | Year: 2010
The use of corrosion resistant and adhesion promoting films and coatings is established industrial practice for many fatigue sensitive components and structures. However, recent environmental legislation restricting the use of a range of toxic heavy metals and their derivative processes, such as chromic acid anodising (CAA), has meant that a number of new coatings systems and pretreatments are currently being developed to replace the traditional processes still in use. Typical of these new systems are the boric-sulphuric acid anodising (BSAA) process, which can be modified to provide excellent adhesive bonding properties, the sulphuric acid anodising process, which includes an additional electrolytic phosphoric acid deoxidising stage (EPAD) to produce a duplex oxide layer, and the recently patented ACDC sulphuric acid anodising process which produces a two layered oxide film which can be tailored to produce different porosity volume fractions within each layer. This communication reports the preliminary findings of a study carried out to assess the fatigue response of Al2618:T6 aluminium alloys to these new processes. In contrast to CAA anodising, the initial results indicate that the EPAD and ACDC processes do not appear to have a significant effect on fatigue. © 2010 Maney Publishing.
Hutchesson S.,Aerospace Engine Controls |
Hutchesson S.,University of York |
McDermid J.,University of York
Information and Software Technology | Year: 2013
Context: The paper addresses the use of a Software Product Line approach in the context of developing software for a high-integrity, regulated domain such as civil aerospace. The success of a Software Product Line approach must be judged on whether useful products can be developed more effectively (lower cost, reduced schedule) than with traditional single-system approaches. When developing products for regulated domains, the usefulness of the product is critically dependent on the ability of the development process to provide approval evidence for scrutiny by the regulating authority. Objective: The objective of the work described is to propose a framework for arguing that a product instantiated using a Software Product Line approach can be approved and used within a regulated domain, such that the development cost of that product would be less than if it had been developed in isolation. Method: The paper identifies and surveys the issues relating the adoption of Software Product Lines as currently understood (including related technologies such as feature modelling, component-based development and model transformation) when applied to high-integrity software development. We develop an argument framework using Goal Structuring Notation to structure the claims made and the evidence required to support the approval of an instantiated product in such domains. Any unsubstantiated claims or missing/sub-standard evidence is identified, and we propose potential approaches or pose research questions to help address this. Results: The paper provides an argument framework supporting the use of a Software Product Line approach within a high-integrity regulated domain. It shows how lifecycle evidence can be collected, managed and used to credibly support a regulatory approval process, and provides a detailed example showing how claims regarding model transformation may be supported. Any attempt to use a Software Product Line approach in a regulated domain will need to provide evidence to support their approach in accordance with the argument outlined in the paper. Conclusion: Product Line practices may complicate the generation of convincing evidence for approval of instantiated products, but it is possible to define a credible Trusted Product Line approach. © 2012 Elsevier B.V. All rights reserved.
Collins T.,University of Birmingham |
Woolley S.I.,University of Birmingham |
Rawson N.C.,Aerospace Engine Controls |
Computer Applications in Engineering Education | Year: 2016
Electronic Engineering undergraduates are increasingly interested in final-year individual projects that involve brain-computer interfacing. This paper outlines the challenges of resourcing these types of medical instrumentation projects and describes the adoption of the open source OpenEEG electroencephalography platform in final-year undergraduate projects. The OpenEEG projects applied a broad range of curriculum components including computer interfacing, signal processing, and software development. The applications were wide-ranging and provided good opportunities to explore relevant research. The paper describes the initial investment in support required to resource the projects, in particular, the provision of supporting code examples. The projects were particularly popular with students. In total, twelve final-year project students used the OpenEEG platform. Student engagement was good and the project outcomes were slightly above cohort average. © 2015 Wiley Periodicals, Inc.
Baker R.,Aerospace Engine Controls |
Habli I.,University of York
IEEE Transactions on Software Engineering | Year: 2013
Testing provides a primary means for assuring software in safety-critical systems. To demonstrate, particularly to a certification authority, that sufficient testing has been performed, it is necessary to achieve the test coverage levels recommended or mandated by safety standards and industry guidelines. Mutation testing provides an alternative or complementary method of measuring test sufficiency, but has not been widely adopted in the safety-critical industry. In this study, we provide an empirical evaluation of the application of mutation testing to airborne software systems which have already satisfied the coverage requirements for certification. Specifically, we apply mutation testing to safety-critical software developed using high-integrity subsets of C and Ada, identify the most effective mutant types, and analyze the root causes of failures in test cases. Our findings show how mutation testing could be effective where traditional structural coverage analysis and manual peer review have failed. They also show that several testing issues have origins beyond the test activity, and this suggests improvements to the requirements definition and coding process. Our study also examines the relationship between program characteristics and mutation survival and considers how program size can provide a means for targeting test areas most likely to have dormant faults. Industry feedback is also provided, particularly on how mutation testing can be integrated into a typical verification life cycle of airborne software. © 1976-2012 IEEE.
Yates M.K.,Aerospace Engine Controls
Institution of Mechanical Engineers - 11th European Fluid Machinery Congress | Year: 2010
The oil system on a modern aero-engine is not only required to lubricate vital parts but also to cool them (1). Thus the oil also needs to be cooled to prevent thermal degradation. The preferred way of doing this is with the fuel, since oil-to-fuel heat exchangers are compact and their impact on the efficiency of the engine is minimal. Positive displacement pumps are used to feed pressurised fuel to the engine. At low flow conditions, e.g. idle, considerable flow is re-circulated around the pump and a large temperature rise (60°C+) can occur. This temperature rise limits the amount of heat that can be dissipated in the fuel for cooling the oil. This paper describes the design and certification of a novel fuel pumping system comprising a centrifugal stage and two twin pinion gear stages. This novel system halves the temperature rise across the pump compared with a conventional system. © Rolls-Royce Goodrich Engine Control Systems Ltd, 2010.