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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. Source


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. Source


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. Source


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. Source


White J.P.,University of Birmingham | Read N.,University of Birmingham | Ward R.M.,University of Birmingham | Mellor R.,Aerospace Engine Controls | Attallah M.M.,University of Birmingham
Materials Science and Technology Conference and Exhibition 2014, MS and T 2014 | Year: 2014

Experiments have been carried out to find the best processing parameters based on their impact on the microstructural and structural integrity development. To support these studies, measurements of the melt pool geometry normal to the scanning direction have been taken. Several melt pool phenomena are presented, including power-melt pool interactions and the degree of re-melting. It is shown through statistical modelling and validation that different combinations of processing parameters can be utilised to produce the same melt pool profiles. This work is compared to an analytical model. By understanding and predicting the melt pool profile and behaviour, it is hoped that this can be linked to the micro structural development of the alloy, and the resultant mechanical properties of the material. Copyright © 2014 MS&T14®. Source

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