bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rotordynamics Standards: New Developments and the Need for Involvement
Authors: Parkinson A G , McGuire P M 
Published: February 2007

The paper reports recent developments in international standards which are particularly pertinent to manufacturers and operators of rotating machinery. In particular it discusses standards relating to balancing, especially flexible shafts, and acceptable vibration levels for rotating machinery. In the area of balancing the report is very opportune because, following an unanimous international ballot at the Draft International Standard (DIS) stage, a new standard ISO 11342, ‘Mechanical vibration—methods and criteria for the mechanical balancing of flexible rotors’, has just been published. Nevertheless, despite publication of this new standard, ISO 11342, work is already under way on a major revision in which the classification of rotors will be completely changed.
The Case for a General Method of Kinematic Analysis of Plane Mechanisms Based on Equations of Constraint
Authors: Fogarasy A A , Smith M R 
Published: February 2007

All but the simplest of single degree of freedom mechanisms have a relatively large number of component parts. To analyse the motion of such systems, therefore, one parameter is rarely sufficient. For an adequate description of the motion characteristics of all components, a number of additional coordinates are needed. This paper introduces a clear and logical notation which facilitates the setting up of the required number of constraint equations by simple inspection of clear line diagrams of the mechanism to be analysed. These constraint equations are eminently suitable for the calculation of velocities and accelerations by direct differentiation. The resulting equations are linear in the velocities and accelerations of all component parts. A method based on this approach is presented and applied to a selection of widely different examples.
Effect of Vortices on Liquid Outflow from Vessels
Authors: Harvey R , Kubie J 
Published: February 2007

This paper considers the effect of vortices on liquid outflow from open vessels. One of the simplest possible arrangements is investigated: an axisymmetric vertical cylindrical vessel with an outlet in its base. A simple spiral vortex is either introduced by supplying the liquid tangentially to the vessel and the outlet or suppressed by the installation of a vortex breaker. A new flow regime for well-developed vortex flow is identified. In this flow regime the variation of the liquid level in the vessel with the flowrate is relatively independent of the method of supply of the liquid to the vessel, and can be correlated by a simple equation.
A Model of Whole-Life Flexible Pavement Performance
Authors: Collop A C , Cebon D 
Published: February 2007

A new ‘whole-life’ pavement performance model (WLPPM), which is capable of making deterministic pavement damage predictions due to realistic traffic and environmental loading, has been developed. A vehicle simulation is used to generate dynamic tyre forces that are a function of distance along the road. These dynamic tyre forces are then combined with the appropriate pavement primary response influence functions (stress, strain and displacement) to give primary response histories at regularly spaced points along the pavement. The primary response histories are then transformed into pavement damage (fatigue and permanent deformation) using an appropriate damage model. The result is an increment of damage at each point along the pavement due to a single vehicle pass. The pavement surface profile is then updated to reflect permanent deformation damage and the layer material parameters are changed to reflect fatigue damage. The procedure is then repeated for the next vehicle pass. Particular attention is given to modelling strength variations in the pavement and dynamic tyre forces. The model is used to investigate the relationship between ‘hot spots’ (due to peak dynamic loads), ‘weak spots’ (due to initial pavement stiffness variations) and long-term pavement damage.
The Assessment of the Rheological Characteristics of Various Polyborosiloxane/Grit Mixtures as Utilized in the Abrasive Flow Machining Process
Authors: Davies P J , Fletcher A J 
Published: February 2007

Abrasive flow machining (AFM) is a non-traditional machining process used since the mid-1960s, which utilizes a mixture of polyborosiloxane and abrasive grit additions extruded across surfaces and edges and through component cavities. The machining mechanism of this process is still only partially understood due to its complex nature, and the present work undertook to investigate the relationship between the rheological characteristics of several mixtures and their associated machining parameters. This paper addresses those rheological characteristics of the various mixtures used in the present work. Experiments were conducted using low viscosity (LV), medium viscosity (MV) and high viscosity (HV) polyborosiloxane base media, in conjunction with silicon carbide abrasive grit of 60 and 100 mesh size, the ratios of the grit to base polymer used being 0, 1 and 2. The test pieces used were mild steel dies and the equipment used to conduct the experiments was an Extrude Hone mark 7 A machine. The results have shown that progression from low to high viscosity base medium produces a reduction in the temperature rise (for example from 32 to 10°C over 30 cycles) as well as an increase in both the average pressure drop across the die (for example from 1700 to 2674 kPa over 30 cycles) and the processing time (for example from 28 to 406 s over 30 cycles). In addition, the temperature of the medium is seen to be an important variable in the AFM process due to its effects on viscosity. Furthermore, as the usage of a medium increases the viscosity and pressure drop across the die increase.
Monitoring of the Mixture Strength in the Cylinders of a Port-Injected Gasoline Engine During Transient Operation
Authors: Ladommatos N , Rose D 
Published: February 2007

A method has been developed which allows monitoring of the air—fuel ratio within the cylinders of a running gasoline engine. The method, which uses a fast-response flame ionization detector (FID), is capable of resolving the air—fuel ratio of individual consecutive engine cycles This method was used to monitor the air—fuel ratio in a port-injected gasoline engine during fast throttle opening. The results obtained show that for a handful of engine cycles the air—fuel ratio departs from the stoichiometric Value. Using additional measurements of the air and fuel supplied to the engine, it was possible to investigate the accumulation of fuel on the inlet port walls of the engine during the throttle opening. The results presented in this paper suggest that the departure of the air—fuel ratio from the stoichiometric value is shorter lived than that recorded by other investigators who used exhaust oxygen sensors for their tests.
Optimal Design of Conventional In-Line Fuel Injection Equipment
Authors: Kegl B 
Published: February 2007

The paper describes an application of optimal design procedure employed on conventional in-line fuel injection equipment for a diesel engine. The procedure is applied to a set of design parameters concerning the design of the cam, high-pressure pump, delivery valve, snubber valve, high-pressure tube and injector respectively. The values of these design parameters are optimized simultaneously within specified maximum and minimum values in order to approach a target injection rate history. The proposed optimal design procedure is defined as a solution process of a non-linear mathematical programming problem defined by the objective and constraint functions. The objective function measures the difference between the target and actual injection rate histories while the constraints concern the response of the system as well as several technological limitations. The form of the objective function is such that it requires special treatment similar to those employed in optimal design of dynamic multi-body systems. However, the complexity of the fuel injection equipment causes specific numerical difficulties when the ideas employed for dynamic systems are adopted. The paper describes how to modify the usual approach in order to circumvent these difficulties. The theory is illustrated with a numerical example comparing the usual versus the modified approach.
Optical Research Engines—Tools in Gasoline Engine Development?
Authors: Winklhofer Dr E , Fuchs Dr H , Fraidl Dr G K 
Published: February 2007

The paper describes the design of a single cylinder base engine which provides optical access to the combustion chamber via glass cylinders and a piston with a glass crown. The application of this engine to the visual analysis of gasoline mixture formation and combustion is demonstrated with examples given for two- and four-valve cylinder heads. The optical methods used in this study comprise laser-induced fluorescence (LIF) to image the unburned mixture within the laser light sheet illuminating a plane of the combustion chamber and flame photography to visualize flame propagation. Simultaneous recording of engine thermodynamic data allows the comparison of conventional engine diagnostics with the results gained from the optical techniques.
Analysis of the Mechanics of Die Drawing Polypropylene Through Strain Rate Controlled Dies
Authors: Ulas I , Craggs G 
Published: February 2007

The die drawing of polymers in the solid state is now an established process for achieving molecular orientation in drawn products and an enhancement of their mechanical properties. A mechanics analysis is presented of the drawing of polypropylene through strain rate controlled dies, where the strain rate is either constant, increasing at a uniform rate or decreasing through the die. The stress in an element of material being drawn is determined from equilibrium considerations and application of the Tresca yield criterion. Flow stress data are deduced from uniaxial stress-strain-strain rate tests and applied to the problem using equivalent stress-strain concepts. Results are presented of axial stress, flow stress and die wall pressure throughout the dies and show that polypropylene can prematurely leave contact with the die wall, particularly in decreasing strain rate dies at high drawing speeds. Increased friction of the die wall and increased drawing speed cause this ‘loss of contact’ point to move progressively downstream in all die cases. Theoretically predicted drawing loads show acceptable agreement with experimental test results when low values of friction coefficient are assumed.
Design for the Alleviation of Transportation Fatality Risk by the Implementation of New Light Rail Transit
Authors: Huston R , Cardimen P , Halperin K 
Published: February 2007

There is a tendency for each engineering community to think of safety only in the context of its own system. Rail engineers think of the safety of the existing rail system and road engineers of the existing road systems. The important safety, however, is that of the entire population. And that safety is considerably higher on rails than on roads. The research question then arises as to whether it is possible to correct an existing road safety problem by design of a rail system. Given the human lives at stake, it is a question worth answering.A design is presented for correction of the highest death rate road in a particular urban area by installation of a light rail system. The road is a 2.6-mile (4.2-km) stretch of urban arterial that has had 18 fatalities in the past thirteen years. The light rail system is shown to be a possible solution to the problem, both from the standpoint of design and from that of economics. It is predicted that the new design should prevent 1.25 fatalities per year.
Evolution of Aviation and Propulsion Systems: The Next Fifty Years
Authors: Allen J E , Armstrong F W , Denning R M 
Published: February 2007

The prospects for the longer-term evolution of aircraft and their propulsion systems are explored, taking a fifty year time-frame. It is considered that the most likely global scenario features continued economic development, aided by the introduction of fuel from alternative sources to offset a progressive shortfall in the availability of oil from relatively accessible fields. Pollution and other environmental problems are foreseen as exerting an increasing influence on decision making. Assuming such a scenario, the aviation fuel prospect is considered. It is concluded that the most likely alternative fuel for aviation in the next fifty years is some form of manufactured liquid hydrocarbon resembling current aviation kerosine, rather than liquid hydrogen, which is a candidate for later introduction. An assessment is offered of the classes of flight vehicle that will be required for civil and military purposes in the time-frame under review. The implications with regard to propulsion systems are then considered, with a discussion of design objectives, technological challenges and research requirements.
A New Approach to the Design of the Large Turbofan Power Plant
Authors: Wilde G L 
Published: February 2007

The lower direct operating costs of the Big Twin subsonic transports encourage the building of ever larger turbofan engines installed on the wings. The steadily improving reliability of the turbofans and the good safety statistics of twin-engined aircraft over many years encourages this trend. Fuel economy is still the dominant factor in determining the design layout of turbofan engines. It requires the combination of the highest possible thermal efficiency of the gas generator core of the engine with optimum propulsion efficiency of the power plant as a whole in cruise flight, allowing for engine nacelle drag and nacelle to wing interference drag. High thermal efficiency and high propulsion efficiency together, lead to relatively small volume flow rate gas generators and high volume flow rate propulsion fans. The resulting geometrical mismatch between the compressors and turbines of the principal turbomachinery components within the engine, introduces losses that penalize the performance gains expected from theoretical considerations of thermodynamics cycle and component efficiencies alone. The paper presents two possible turbofan design layouts intended to overcome the limitation of current turbofan power plant designs. The aim is to design a power plant with the highest thrust per unit frontal area combined with the highest air miles per gallon in cruise flight.
Roentgen Stereophotogrammetric Analysis for Assessing Migration of Total Hip Replacement Femoral Components
Authors: Kiss J , Murray D W , Turner-Smith A R , Bulstrode C J 
Published: February 2007

A new Roentgen stereophotogrammetric analysis system, using a biplane technique, has been developed to determine the migration and rotation of total hip replacement (THR) femoral components in three dimensions. Stainless steel marker balls were injected into the femur during the operation. The patients stood within a calibration frame during the X-ray. The two exposures were taken consecutively allowing radio-opaque shutters to be moved in front of the films to prevent fogging. Studies with a model demonstrated that the system was capable of measuring the position of an implant to better than 0.11 mm (2 SD)w. In vivo measurements demonstrated that the migration rate of the different parts of the femoral component could be determined with an accuracy of 0.25 to 0.50 mm/year. By considering the accuracy determined in different ways, methods for improving the system have been identified. The migration and rotation rate of 58 Hinek cemented femoral components was studied for four years. Migration was three to five times greater (p < 0.001) during the first year than subsequently. The prosthesis head moved the most during the first year (0.94 mm). A better understanding of the cause of implant failure could be obtained by studying the early migration of different types of prosthesis and comparing this with their clinical results and design features.
Experimental and Theoretical Study of the Contact Mechanics of Five Total Knee Joint Replacements
Authors: Stewart T , Jin Z M , Shaw D , Auger D D , Stone M , Fisher J 
Published: February 2007

The tibio-femoral contact area in five current popular total knee joint replacements has been measured using pressure-sensitive film under a normal load of 2.5 kN and at several angles of flexion The corresponding maximum contact pressure has been estimated from the measured contact areas and found to exceed the point at which plastic deformation is expected in the ultra-high molecular weight polyethylene (UHMWPE) component particularly at flexion angles near 90°. The measured contact area and the estimated maximum contact stress have been found to be similar in magnitude for all of the five knee joint replacements tested. A significant difference, however, has been found in maximum contact pressure predicted from linear elasticity analysis for the different knee joints. This indicates that varying amounts of plastic deformation occurred in the polyethylene component in the different knee designs. It is important to know the extent of damage as knees with large amounts of plastic deformation are more likely to suffer low cycle fatigue failure. It is therefore concluded that the measurement of contact areas alone can be misleading in the design of and deformation in total knee joint replacements. It is important to modify geometries to reduce the maximum contact stress as predicted from the linear elasticity analysis, to below the linear elastic limit of the plastic component.
Influence of Surface Roughness and Oil Ageing on Various Ceramic-Steel Contacts under Boundary Lubrication
Authors: Denape J , Masri T , Petit J-A 
Published: February 2007

The friction and wear behaviour of four structural ceramics (two aluminium oxides of different purity, a silicon nitride and a tetragonal zirconia polycrystal) have been investigated under boundary lubrication against a 100C6 hard steel (52100 steel). The effect of three initial surface roughnesses of the ceramics is studied. Lubrication is by a commercial oil used ‘as received’ (new oil) and ‘aged’ (used oil). Tests are performed on an alternating ‘pin-on-plate’ tribometer. The friction and wear responses are analysed in terms of three main parameters depending on the mechanical preparation mode of the ceramics surface: the roughness magnitude, the morphology of the asperities (sharps or blunts) and the mechanical strength of the asperities. The evolution of these parameters during sliding leads to significant changes of tribological behaviour and contact pressure. The friction and wear transitions result from changes of the lubrication mode where roughness and oil have a competitive action. The wear processes of the ceramic surfaces include fracture mechanisms of the asperities and/or polishing by the mechanochemical action of the lubricant and submicronic ceramic wear debris. The worn surfaces of steel exhibit either abrasion grooves or a continuous metallic layer covering the steel. A running-in effect is observed on both silicon nitride and zirconia but does not occur on aluminas. The stronger running-in effect is observed with used oil. The used oil can lead to a very smooth sliding surface on the ceramic and allows particularly low friction coefficients and steel wear, but only after a more severe initial degradation process ESCA analyses on steel reveal the occurrence of a reaction film generated through chemical reactions with the oil.
Analysis of a Grease-Lubricated Roller Bearing under Arctic Conditions
Authors: Östensen J O , Åström H , Höglund E 
Published: February 2007

This paper summarizes measurements of starting torque and motion of the rollers in a roller bearing during start-up at a temperature of − 30°C. The bearing was lubricated with three different greases and the tests were carried out after a running-in procedure at + 20 °C. The results were compared with measurements obtained at +20°C and with results from one base oil at +20°C. A model for the roller motion was also built and simulations of the roller motion were compared with the measurements. Independent of temperature and lubricant the rollers rolled in the loaded zone and slipped, more or less, in the unloaded zone. The degree of sliding in the unloaded zone was found to be governed mainly by the local lubricant distribution and the position of the roller in the cage pocket. Some differences are also seen in the slide-roll ratio between the lubricants. A roller diameter difference of 1.3 pm gave a significant difference in roller motion, with the slightly thinner roller slides more in the unloaded zone of the bearing.
The Elastohydrodynamic Lubrication of Elliptical Point Contacts Operating in the Isoviscous Region
Authors: Hooke C J 
Published: February 2007

The elastohydrodynamic lubrication of point contacts is examined and results for the minimum film thickness are presented for a wide range of radius ratios and operating conditions. The results are compared with the predictions of the appropriate regime formulae. Although these formulae give a reasonable estimate of the contact's behaviour, the actual clearances are often substantially different, particularly close to the regime boundaries. Interpolation equations for seven values of radius ratio are given and these should be sufficient to allow the minimum clearance to be estimated for most isoviscous point contacts.
Prediction of Film Thickness in an Elastohydrodynamic Point Contact Lubricated with a Viscosity Index Improved Base Oil
Authors: Östensen J O 
Published: February 2007

A simple iterative method is used for the computation of the central film thickness in a fully flooded elastohydrodynamic (EHD) point contact lubricated with a polymeric viscosity index (V1)-improved base oil. The shear stress dependence of the Vl-improved base oil is included in the iterative method. Experimental data are presented on temporary viscosity loss and central film thickness at different temperatures from —8 to 40° C. A good approximation of the central film thickness in an EHD point contact lubricated with V1-improved oil is given by using an iterative method involving the temporary viscosity loss of the Vl-improved base oil. The central film thickness depends on the mean shear stress at the inlet of the contact, and this shear-thinning effect has been accounted for in the calculations.
Dynamic Behaviour of Tilting-Pad Journal Bearings
Authors: Pagano S , Rocca E , Russo M , Russo R 
Published: February 2007

The dynamic behaviour of a rigid rotor on tilting-pad journal bearings system is analysed for balanced and unbalanced rotors. The study mainly regards a two-pad journal bearing symmetric with respect to the external static load. Both linear and non-linear behaviours have been analysed, with particular reference to the stability of the journal and pads equilibrium positions in the case of balanced or slightly unbalanced rotors, and to the stability of their synchronous motions in the case of considerable unbalance.