bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of Heat Generation and Resultant Temperature Distribution Due to the Passage of an Ultrasonic Wave Through a Mixture of Polyborosiloxane and Silicon Carbide
Authors: Fletcher A J , Fioravanti A 
Published: February 2007

A mixture of polyborosiloxane and silicon carbide abrasive has been agitated using an ultrasonic system. The passage of the ultrasonic wave through this mixture resulted in an increase in temperature due to conversion of energy from the ultrasonic wave into heat. This investigation was initially concerned with the calculation of the heat-generation term, from a knowledge of the attenuation of the acoustic wave. The second stage of the analysis involved the solution of the relevant transient heat-transfer equations for conduction and convection with internal heat generation. The solution to these equations was obtained using a numerical technique. Temperatures at various positions within the system were measured using suitable equipment. These experimental data were compared against the results of the calculation and it was found that significant discrepancies existed between the two sets of results when the analysis considered heat generation as a sole function of wave attenuation. In an attempt to improve the correlation between calculated and measured temperatures the analysis was developed to include a heat-generation term acting at the interface between the sonotrode and the transmission medium. Such heat generation would be produced by frictional heating at the interface, and this would be associated with poor coupling between the acoustic source and the medium. It was found that the correlation between calculated and measured temperatures improved greatly on adoption of the frictional heating analysis, which leads to the suggestion that heating within the medium is a function of both ultrasonic attenuation and frictional heating. For the conditions specified the latter appears to have a dominant role.
An Experimental Study on the Dynamic Response of a Beam Structure Containing a Pseudo Joint
Authors: Ren Y , Beards C F 
Published: February 2007

The effects of frictional damping on the dynamic response of a beam structure have been investigated. The frictional damping was contributed from the slip mechanisms in a ‘pseudo’ joint, that is a joint that did not take any static load. Using pseudo joints for vibration control has significant advantages over using joints that are designed both to take static load and to introduce frictional damping; because there is almost no restriction on the configuration of the pseudo joint, the undesirable side effects related to the frictional damping such as fretting corrosion of contact surfaces and loss of static stiffness are zero if the frictional damping from a pseudo joint is utilized. An ‘optimum’ clamping force was found which minimized the magnitude of the frequency response function (FRF) of the structure under excitation. A reduction of about 20 dB in the amplitudes of the FRFs was achieved by adjusting the clamping force at the joint. Frictional damping was found to be significant over the measured frequency range of 20-2000 Hz, and it was particularly effective over the range of 20-1000 Hz. The magnitudes of the FRFs of the structure were determined by the ratio of clamping force to excitation force. They were insensitive to the change of clamping force near its optimum value; also the optimum clamping force was not sensitive to small modifications to the structure. Therefore, utilizing frictional damping in pseudo joints is an effective technique for vibration control.
A New Wobble Drive with Particular Application in a Stirling Engine
Authors: Clucas D M , Raine J K 
Published: February 2007

Swash plate or wobble mechanisms used in engine drives commonly require gearing, slides and/or spherical bearings to connect the piston rods to the transfer mechanism and react to the torque produced. This paper briefly reviews the literature on this class of engine mechanism and presents the theory and form design of a new wobble yoke mechanism which achieves single degree of freedom rotational motion for all bearings, enabling the use of sealed rolling element bearings and eliminating the need for sliding surfaces or gears. The mechanism has been first applied in a liquefied petroleum gas-fuelled integrated Stirling engine electric generator system for battery charging. The hermetically sealed system gives 200 watt d.c. electrical output and is configured for charging 12 volt batteries. A square four-cylinder double-acting configuration is used, with pistons equispaced and parallel to the output shaft. The mechanism is easily parametrically scaled to different engine sizes. It also has potential application in compressors, pumps, other Stirling cycle machines or Otto cycle engines. Development of mechanical design features and thermodynamic and electrical development of the Stirling engine generator are to be described in a subsequent paper, to be published in the next Part C issue.
The Mechanics of Parallel Mechanisms and Walking Machines
Authors: Zhang S J , Sanger D J , Howard D 
Published: February 2007

A parallel mechanism is one whose links and joints form two or more serially connected chains which join the fixed base and the end effector The mechanism of a multi-legged walking machine can be considered as a parallel mechanism whose base is not fixed and whose configuration changes during different phases of its gait. This paper presents methods for analysing the mechanics of parallel mechanisms and walking machines using vector and screw algebra Firstly, displacement analysis is covered; this includes general methods for deriving the position vector of any joint in any leg and for calculating the active joint displacements in any leg. Secondly, velocity analysis is covered which tackles the problem of calculating active joint velocities given the velocity, position and the orientation of the body and the positions of the feet. Thirdly, the static analysis of these classes of mechanisms using the principle of virtual work and screw algebra is given. Expressions are derived for the actuator forces and torques required to balance a given end effector (or body) wrench and, in the case of a walking machine, the ground reactions at the feet. Numerical examples are given to demonstrate the application of these methods.
Using CFRP for the Design of a Connecting Rod for Automobile Applications
Authors: Gunyaev G M , Borovskaya S M , Panin V I 
Published: February 2007

Composite materials may be used for selective improvements to automobile engines. For example, using a composite connecting rod offers some advantages such as weight saving, inertial forces reductions, increasing automobile speeds and reducing noise emission from engines. Two technological approaches were chosen for connecting rod production. The first type of connecting rod consists of a compression-stressed shank made of laminated plastic and the tension loop made of carbon fibre reinforced plastic (CFRP). The second type of connecting rod is made of multi-directional laminated CFRP. Due to these approaches split and unsplit versions were made. Moreover, the titanium-CFRP concept of the split connecting rod was assessed. Several studies have shown the possibility of manufacturing composite connecting rods satisfying load requirements for engine components.
Investigations into the Precessing Vortex Core Phenomenon in Cyclone Dust Separators
Authors: Yazdabadi P , Griffiths A J , Syred N 
Published: February 2007

Experimental investigations have been carried out to examine the effect of downstream pipework configurations on the precessing vortex core (PVC) generated within the exhaust region of a cyclone dust separator. Characterization of the PVC using a non-dimensionalized frequency parameter (NDFP) was used to determine the relationship between Reynolds number and geometrical swirl number of the cyclone. The results show that the NDFP tends towards an asymptotic value for Reynolds numbers of about 50 000 and high swirl numbers (> 3.043). This value is reached earlier with lower swirl numbers. It was concluded that any exhaust pipework configuration produced a significant drop in the PVC frequency, and certain configurations either delayed or promoted the development of the PVC.
Clearances between the Rotors of Helical Screw Compressors: Their Determination, Optimization and Thermodynamic Consequences
Authors: Tang Y , Fleming J S 
Published: February 2007

Although helical screw compressors contain only two moving parts, their shapes are very complicated and must mesh to very fine clearances. The process of determining lobe geometry requires that parts of the male generate parts of the female and vice versa. Once the nominally perfect (zero clearance) profile geometry has been generated, a method for determining clearances is needed which gives an attainable result from the manufacturing and operational viewpoints and gives a thermodynamic efficiency which is at least equal to that of competing machines of the same class. The thermodynamic performance depends principally on the internal leakage rates in the compressor, in particular, the leakage across the contact (sealing) line. This paper presents two ways of setting clearances. They result in different patterns of clearance distribution along the sealing line and have different effects of the thermodynamic performance of the compressor due to the different leakage mass flowrates that they permit. A design technique for obtaining an optimum clearance distribution is discussed. Finally, a thermodynamic model of compressor behaviour is used to predict the performance as influenced by the different clearance distributions, and the predictions are compared with measured values taken from a test compressor. The predictions are shown to be good.
Energy Conservation via Optimal Control of Cone Crushers
Authors: Parkin R M , Bearman R A 
Published: February 2007

The quarrying industry has a major impact on the environment. The impact arises from direct sources (that is the quarrying operation with attendant noise and dust) and indirect sources (that is electricity usage). To quantify these usages, the quarrying industry in the United Kingdom consumes some 4.8 TW h/year, representing 3 per cent of installed generating capacity. A significant proportion of this usage is attributable to machines known as cone crushers. Cone crushers are large items of plant (up to 3 m diameter) producing, mainly, aggregates for the road-making industry. The British output is currently 230M tonnes per annum, due to rise to 400M tonnes by 2011. The energy costs are currently £240M per annum. Further environmental issues are raised by the use of manganese steels. A crusher uses, components that can wear away at a rate of 1 mm per hour. If the parts are not renewed at regular intervals machine performance can be dramatically affected and, in the worst case, mechanical damage may occur. The parts are replaced early to avoid damage with a concomitant poor energy utilization. The paper describes a programme of work intended to address some of these problems. Pegson Limited, a leading manufacturer of crushing plant, in association with Transfer Technology plc and De Montfort University, are co-operating in a project funded by SERC/DTI under the design of high-speed machinery LINK programme, Treatment is theoretical, demonstrating the justification of the funding. A follow-up paper will detail actual savings and contrast them with the theoretical model. The next generation of crushers will be instrumented with a range of sensors to monitor machine performance. Of especial interest is a novel sensor which monitors the wear of the crushing components The sensors are connected to a knowledge-based system (KBS) to monitor and control performance. The sensors are not reported in any detail due to the pursuance of Intellectual Property Rights. The ideal performance parameters are obtained from another KBS based on rock mechanics and models of wear mechanisms. The advanced crushers incorporate a simple man/machine interface and make much use of distributed control based on NEC 78K series microcontrollers. Preliminary studies indicate that energy savings of £15M in the United Kingdom (over £400M worldwide) per year are realizable. Further savings of £5M in the United Kingdom (nearly £150M worldwide) per year arise from the optimal use of the manganese crushing components.
The Study of Transonic Flows by Quantitative Holographic Interferometry
Authors: Parker S C J , Holden C M E , Bryanston-Cross P J 
Published: February 2007

Optical flow diagnostics are non-intrusive and therefore suitable for investigating perturbation sensitive transonic flows. Unfortunately, most of these techniques depend on particle seeding and are confined to point measurements. In contrast, holographic interferometry is whole field, does not require seeding, and is an appropriate tool for the study of temporal and spatial properties of unsteady flows. At present, however, holographic interferometry is mainly used qualitatively due to the practical restrictions of data recording, acquisition and processing. This paper addresses some of the limitations that have prevented routine use of holographic interferometry in production wind tunnel testing. Vibration is a frequent problem when capturing interferometric data; however, this paper shows that the associated rigid body movements are easily removed during Fourier transform fringe analysis. A second major limitation arises when attempting to interpret and analyse interferograms from three-dimensional flows. To overcome this problem, a prototype optical system is described which can record multiple interferometric views around the working section. The information extracted from these images may then be used to tomographically reconstruct the three-dimensional density field. Holographic measurements for two-dimensional and three-dimensional axisymmetric flows are presented and compared quantitatively to computational fluid dynamics (CFD) predictions. The experimental and computational results are in general agreement and demonstrate the feasibility of automating the extraction of three-dimensional density data from holographic interferograms.
The Life And (Maintenance) Times of an A300 Tailplane Trim Actuator—A Systems Perspective
Authors: Badger M 
Published: February 2007

In order to achieve the required level of system safety, it is often necessary to specify scheduled single system check periods for duplicated or triplicated systems, where failure of one system is neither indicated nor evident to the pilot or ground crew. This paper presents the techniques used in the analysis of the A300 tailplane trim actuator service data, for the purpose of identifying a check period and overhaul life, consistent with continued safe economic operation.
The Behaviour of Lubricants in Contacts: Current Understanding and Future Possibilities
Authors: Spikes H A 
Published: February 2007

The main role of a lubricant is to form a protective, low shear strength film between rubbing surfaces and thereby reduce friction and surface damage. The science, or art, of both the lubricant and the mechanical designer is to develop combinations of lubricant and mechanical system best able to form such films. This task is not straightforward since modern technology is continually demanding lower friction and better protection over an ever-widening range of operating conditions. Furthermore, environmental concerns are also producing both design constraints and the need for rapid change. The aim of this paper is to show how progress is being made by experimental research which looks inside rubbing contacts to see how lubricants behave therein. The paper focuses on concentrated contacts, as found in gears, cams and rolling element bearings, and describes a number of techniques for probing such contacts to observe just how a range of lubricant types, from greases to emulsions, behave in such contacts to reduce friction and form films.
Elastohydrodynamic Lubrication of Soft-Layered Solids at Elliptical Contacts: Part 1: Elasticity Analysis
Authors: Yao J Q , Dowson D 
Published: February 2007

In this two-part paper we consider the elastohydrodynamic lubrication (EHL) of soft-layered solids representing elliptical contacts. The problem has not previously attracted much attention, partly due to the lack of an effective numerical procedure to solve the coupled non-linear system of equations, but it is essential to the proper design of bearings with soft elastomeric liners and the full understanding of synovial joint lubrication. In Part 1, the elasticity analysis for the surface deformation of a low elastic modulus layer on a hard-backing half-space under various forms of normal loadings is considered, by means of both the rigorous Hankel transform method and various simplifications. For layers of compressible materials (v ≤ 0.4), a generalized foundation model described by a second-order differential equation is proposed to represent the relationship between the surface deformation and the applied pressure. The empirical equation developed in this study is valid for a very wide range of the aspect ratio of the contact and provides an alternative way of modelling the elastic deformation without recourse to the often tedious integration in the numerical analysis of the EHL problem. The simplest form (constrained column model) of the equation, where the surface deformation is directly proportional to the local applied pressure, was found to be reasonably accurate for compressible thin layers (the aspect ratio 2b/ht ≥ 5 and Poisson's ratio v ≤ 0.4).
Damping the Vibrations of a Rigid Shaft Supported by Ball Bearings by Means of External Elastomeric O-ring Dampers
Authors: Aktürk N , Gohar R 
Published: February 2007

In this paper the radial and axial vibration behaviour of a rigid shaft supported by a pair of back-to-back angular contact ball bearings, mounted on elastomeric O-ring dampers, is studied. The use of elastomeric dampers for reducing the untoward effects of vibrations, due to unbalance of the shaft centre, is investigated. A computer program was developed to simulate such situations with the results presented in the form of frequency response curves and shaft centre orbits. All results showed that elastomeric O-ring dampers can successfully be used for shaft-ball bearing systems as long as the dynamic characteristics of both the system and the elastomeric O-rings are known very well.
Measuring Lubricant Film Thickness with Image Analysis
Authors: Gustafsson L , Höglund E , Marklund O 
Published: February 2007

Determining lubricant film thickness between contacting bodies under elastohydrodynamic (EHD) conditions is often simulated by using a ball/cylinder and transparent disc apparatus together with an interferometry technique. The simulated contact will have a point or elliptic shape and the light used can be white or monochromatic. The interference pattern is normally photographed with a regular camera or a video camera and the pictures are then evaluated by the naked eye of the observer. In most cases, only central or minimum thicknesses are evaluated. In this paper an image processing method for the analysis of film thickness is presented. This method makes it possible to extract considerably more information about film thickness fluctuations than is achievable by the naked eye. The method primarily matches hue (but also saturation and intensity values) from digitized colour interferometric images of the unknown film shapes with calibration values obtained with known geometric shapes. The method is shown to work well in the range from 95 up to 700 nm with white light and makes the results unbiased by the observer. Furthermore, absolute film thickness can be evaluated without prior knowledge about the fringe order in the interferogram.
The Optimum Pressure Ratio for a Combined Cycle Gas Turbine Plant
Authors: Horlock J H 
Published: February 2007

A graphical method of calculating the performance of gas turbine cycles, developed by Hawthorne and Davis (1), is adapted to determine the pressure ratio of a combined cycle gas turbine (CCGT) plant which will give maximum overall efficiency. The results of this approximate analysis show that the optimum pressure ratio is less than that for maximum efficiency in the higher level (gas turbine) cycle but greater than that for maximum specific work in that cycle. Introduction of reheat into the higher cycle increases the pressure ratio required for maximum overall efficiency.
Knowledge Elicitation and the Development of a Knowledge-Based System for Production Scheduling
Authors: Price G , Dunne F P E , Teoh K S , Walters D G 
Published: February 2007

A prototype knowledge-based system for automated production scheduling has been developed for a press shop, which manufactures laminations for stator and rotor packs and cores for electric motor production. The system is PC (personal computer) based, user friendly, and may be interfaced to the existing computer-based MRP (material requirements planning) system, making the transfer of production data quick and easy. The knowledge-based system has been tested and validated over a range of production circumstances and the predicted production schedules show close agreement with those manually produced, over longer time-scales, by the human scheduler. The knowledge elicitation procedures developed are described and, in particular, the use of a large flow diagram to describe the decision-making process during scheduling is discussed. The visual representation of the structure of the decision-making process is of particular benefit in aiding clarity of communication between the knowledge engineer and the domain expert. The techniques for knowledge acquisition within the production scheduling environment have been formalized and their use is advocated for use in the development of scheduling systems. For the prototype system to be of practical benefit within the press shop, further development of the system is necessary to enable all the presses and lamination combinations to be scheduled. This is currently being carried out within the company.
Repair Learning for a Working Knowledge-Based System
Authors: Olley P , Kochhar A K 
Published: February 2007

This paper addresses the issues of using a learning mechanism for closed-loop updating of the repair knowledge base of a working knowledge-based system (KBS). Issues addressed are stability under noisy data and errors arising from learning from cases in which several repairs are attempted. Simulated data are used to investigate the effects of the latter feature. It is shown that the learning method can cause a significant systematic error in learnt knowledge. A knowledge-based method, which aims to intelligently compensate for the systematic error using diagnostic domain knowledge, is investigated. It is shown that the method greatly reduces the systematic error in learnt repair knowledge.