bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sliding Friction Analysis of Phosphatidylcholine as a Boundary Lubricant for Articular Cartilage
Authors: Williams P F , Powell G L , LaBerge M 
Published: February 2007

Dipalmitoyl phosphatidylcholine (DPPC), the major lipidic component of the synovial fluid (45 per cent), has been implicated in previous studies in synovial joint lubrication as a potential boundary lubricant for articular cartilage. The purpose of this study was to evaluate the effectiveness of DPPC as a boundary lubricant at physiological stresses experienced by weight-bearing joints (up to 7.5 MPa). The sliding coefficients of static and kinetic friction for glass surfaces coated with DPPC layers of physiological thickness (70 nm) were measured as a function of average contact stress, contact geometry (point and line), applied load and relative velocity (from 25 to 0 mm/s) and compared to the coefficient of friction for clean glass in the same conditions. The coefficient of friction for DPPC-lubricated surfaces was dependent on contact geometry, obeyed Amonton's law (not dependent on axial load or contact area), was dependent on relative velocity within the range stated and was an effective lubricant at physiological stresses. This study showed that dipalmitoyl phosphatidylcholine can be an effective boundary lubricant at stresses observed in load-bearing joints. Because of their surface-active nature, these adsorbed molecules might also act as a protective layer for the articular surfaces.
Examination of Alumina Ceramic Components from Total Hip Arthroplasties
Authors: Nevelös A B , Evans P A , Harrison P , Rainforth M 
Published: February 2007

Materials analysis has been conducted on retrieved Mittelmeier-Autophor ceramic components from total hip arthroplasties, correlating articulating surface wear morphology with clinical reasons for failure. Plastically deformed, agglomerated wear debris (30–60 μm) has been identified on femoral head articulation wear surfaces, displaying exaggerated wear, especially during the initiation stage. Such surfaces were associated with clinical failures involving displacement of the acetabular cup and perforation of the cortex by the femoral stem, It is thought that this wear debris may play an important role in the promotion of the ‘avalanche’ wear mechanism, as it is adherent and thus difficult to remove from the wear interface
Finite Element Analysis of Poor Distal Contact of the Femoral Component of a Cementless Hip Endoprosthesis
Authors: Taylor M , Abel E W 
Published: February 2007

The difficulty of achieving good distal contact between a cementless hip endoprosthesis and the femur is well established. This finite element study investigates the effect on the stress distribution within the femur due to varying lengths of distal gap. Three-dimensional anatomical models of two different sized femurs were generated, based upon computer tomograph scans of two cadaveric specimens. A further six models were derived from each original model, with distal gaps varying from 10 to 60 mm in length. The resulting stress distributions within these were compared to the uniform contact models. The extent to which femoral geometry was an influencing factor on the stress distribution within the bone was also studied. Lack of distal contact with the prosthesis was found not to affect the proximal stress distribution within the femur, for distal gap lengths of up to 60 mm. In the region of no distal contact, the stress within the femur was at normal physiological levels associated with the applied loading and boundary conditions. The femoral geometry was found to have little influence on the stress distribution within the cortical bone. Although localized variations were noted, both femurs exhibited the same general stress distribution pattern.
The Implementation of a Feature-Based Component Representation for CAD/CAM Integration
Authors: Case K , Gao J X , Gindy N N Z 
Published: February 2007

Recent research and development has the objective of increasing productivity and cost effectiveness by integrating many activities such as design, analysis, process planning, assembly planning and production planning which encompass the entire manufacturing planning and operational control aspects of a manufacturing enterprise. It has been recognized that a key to the integration lies in the determination of a representation scheme for products that can be interpreted for the various needs of these different applications. Geometric (solid) modellers were regarded by many researchers as the appropriate representation, but more recently a features approach has been proposed to enhance the capabilities of solid modellers. This paper introduces ongoing research which is aimed at the development of a feature-based design system for process planning. The system is fully integrated with a conventional boundary representation (Brep) modeller which enhances its modelling capabilities in representing, editing and validating features of components. The main aspects of the feature-based design system are described in detail, such as the feature library, feature taxonomy, feature operations, feature relationships and tolerances. The generation of a detailed data model for transmission to manufacturing planning activities is also described and demonstrated by reference to an example component. A brief indication is given of our parallel research work in using such models as the basis of process planning and process capability modelling.
Self-Tuning Control of Cutting Force for Rough Turning Operations
Authors: Allen R , Huang K 
Published: February 2007

Considerable developments have taken place in recent years in the versatility and sophistication of computer numerical control (CNC) controllers. Machine tool control schemes have not, however, advanced to the same extent. Control of the metal cutting process has long been advocated as a goal to pursue to improve productivity, but progress has been slow. This paper introduces a simplified generalized minimum variance approach to self-tuning which shows promise for the adaptive control of metal cutting. An experimental rig is described and the results of tests to adaptively control the vertical component of cutting force during rough turning operations by manipulating the feedrate are presented. A simulation of the rig was also developed and used as an initial testbed for adaptive control techniques.
A Study of Mechanical Stress Relief (MSR) Treatment of Residual Stresses for One-Pass Submerged Arc Welding of V-Grooved Mild Steel Plate
Authors: Bae K-Y , Na S-J , Park D-H 
Published: February 2007

The heat-transfer and thermal stress distributions in one-pass submerged arc welding (SAW) were numerically determined using the finite element method (FEM) for a V-grooved rectangular steel plate in which the weld preparation was filled during welding. A two-dimensional non-linear heat-transfer analysis was performed for a transverse section of the plate. This was followed by a thermo-elasto-plastic transient thermal stress analysis, assuming plane strain to be constant for the same model section. The same stress model was used to simulate a mechanical stress relief (MSR) treatment of the plate. This has frequently been used in the fabrication of large pressure vessels instead of post-weld heat treatment (PWHT). In this way its effect in reducing the residual stress in the welded plate was investigated. MSR was simulated by enforcing a constant displacement loading in the welding direction. The solution of the thermal stress analysis showed that it was possible for the residual stress around the weld centre to be accurately estimated by accurate modelling of the dilution of the filler metal in the fused zone of the base metal. The conclusion derived from the MSR simulation was that it could quantitatively predict the effect of reducing the residual stress in the welded plate. Only limited experimental data were available. The mechanism of stress reduction was plastic straining in regions of high residual stress. The amount of stress reduction at the weld centre had a linear relationship to the magnitude of the external stress relieving load. The numerical results for the MSR simulation agreed fairly well with experimental ones obtained from the MSR test performed on a welded plate.
The Ideal Locations for the Contra-Rotating Shafts of Generalized Lanchester Balancers
Authors: Chiou S-T , Davies T H 
Published: February 2007

The inertia of the moving parts of high-speed planar mechanisms creates a shaking force that is variable in magnitude, direction and line of action throughout a cycle. Alternatively, the instantaneous shaking force vector can be represented by an equal parallel force acting through an arbitrarily chosen origin, together with a moment about that origin. The two components of the force and the moment can be computed by kinetostatic analysis at discrete intervals of a cycle to create three arrays. The discrete Fourier transform converts these arrays from the time to the frequency domain. The lowest frequency term of order k = 1 is of cycle frequency. Terms of higher order k > 1 have frequencies that are k times cycle frequency. The shaking force frequency term of order k can be represented by two contra-rotating force vectors of constant, but generally unequal, magnitude rotating at k times cycle frequency. The forces can be eliminated by equal and opposite forces exerted by counterweights mounted on contra-rotating shafts rotating at the same speed. However, if the locations of these shafts are both arbitrarily chosen, a shaking couple of order k will generally remain unbalanced. Fast Fourier transform (FFT) analysis of the array of moments as well as the force components enables suitable shaft locations to be determined in such a way that this couple vanishes. The couple vanishes if the balancing shafts are coaxial with a centre at an invariant location in the plane. The couple can also be eliminated even though the location of either shaft, but not both, is chosen arbitrarily. The location of the second shaft is then determinate and two procedures are explained to determine that location.
Two-Dimensional Temperature Distributions of Combustion Chamber Surfaces in a Firing Spark Ignition Engine
Authors: Zhao H , Codings N , Ma T 
Published: February 2007

This paper summarizes the development and application of advanced thermal imaging techniques to a spark ignition engine at the University of Cambridge Department of Engineering. A thermal imaging system is described which is capable of viewing and recording the cylinder head surface temperature and piston surface temperature in a firing spark ignition engine. Two-dimensional temperature distributions of these surfaces were measured both during the engine's warm-up period and steady state operations. The influence of the engine's operating conditions was examined upon the temperature distributions of combustion chamber surfaces during the engine's warm-up period. The effect of spark timings, particularly the onset of knocking combustion on the surface temperatures, has been studied.
Numerical Simulation Method Applied to the Multi-Expansion Exhaust System of a Two-Stroke Engine
Authors: Chiou J-S , Chiang M-S , Chen C-K 
Published: February 2007

A numerical method is presented to simulate the pressure wave in the multi-expansion exhaust system of a two-stroke engine. In the simulated processes, the inlet pipe, scavenge pipe and exhaust pipe of the two-stroke engine are simplifed by the pipe model, while the engine cylinder, crankcase and the expansion chamber are treated as the vessel model. The cubic-interpolated pseudo-particle (CIP) method combined with the method of characteristics (MOC) is used to solve the hyperbolic equations. The results from simulation compare reasonably well with the experimental data.
Photoelastic Determination of Elastic and Plastic—Elastic Strain Distributions in Tube Plates
Authors: Fessler H , Hyde T H , Musson J K 
Published: February 2007

These tube plates are the parts of boiler drums that contain triangular arrays of holes for the water (or steam) tubes. These drums are thin enough to be treated as flat plates in biaxial tension. Photoelastic coatings were bonded to eight models made of two boiler steels and the strain distributions around the holes and in the ligaments between the holes were determined for several loads. The results showed confined yielding around the holes before failure of the diagonal or axial ligaments under the 2:1 load ratio, which occurs due to pressure without ‘beam’ bending of the boiler drum. A frozen stress test was also carried out to determine the elastic principal stresses in the ligaments of one geometry. The results showed that, in this diagonal ligament, along the straight line joining points of greatest elastic stress at the holes, the smaller principal stresses in the plane of the plate were also tensile, but only about 10 per cent of the greater principal stresses. This shows that, along these lines of likely failure, the photoelastic coatings underpredict the onset of yielding slightly.
A Robotic System for Minimal Access Surgery
Authors: Potamianos P , Davies B L , Hibberd R D 
Published: February 2007

A computerized manipulator-assisted method is presented to facilitate the execution of minimal access surgical procedures. The proposed method employs a passive manipulator to assist the surgeon in the three-dimensional spatial location of anatomical features, using general purpose X-ray fluoroscopy or ultrasound imaging equipment with video input/output facilities. The method enables the three-dimensional navigation of surgical tools in correlation with two-dimensional medical images. A system is under development at Imperial College, London, for the application of this method to minimally invasive renal procedures. The system will enable the spatial location of renal calculi and the establishment of percutaneous renal track central axes. The proposed method is compatible with existing urological procedures and imaging equipment and enables the correlation of X-ray and ultrasound imaging modalities.
Contact Mechanics of Soft Layer Artificial Hip Joints: Part 2: Application to Joint Design
Authors: Yao J Q , Parry T V , Unsworth A , Cunningham J L 
Published: February 2007

In this paper, the general solutions previously obtained for the contact mechanics of a soft layer artificial hip joint have been applied to the design of such joints. In particular, simple power-law design formulae have been generated for the prediction of the contact radius and the maximum Tresca shear stress within the elastomeric layer, when the aspect ratio varied from 1 to 20 (which covered the entire range of the aspect ratio for soft layer artificial hip joints). The effects of the layer thickness, Young's modulus of the layer and the equivalent radius of the joint upon the contact area and the maximum Tresca shear stress have all been examined for physiological loading conditions which would be experienced by hip joint prostheses in the body. Furthermore, the shear strain field was calculated so that the level of strain expected for such joints under physiological loading conditions can be estimated. With these data, relevant fatigue tests can be devised to assess the long-term performance of any particular design of soft layer hip joint. Finally, the effect of the friction between articular surfaces upon the stress field within soft layers has been examined using a newly developed asymptotic analytical theory. It was shown that, for a low coefficient of friction, the maximum Tresca shear stress occurred at layer-substrate bonding interface. With an increase in the coefficient of friction, however, the maximum Tresca shear stress increased its magnitude and moved towards the centre of the contact area along the articular surface.
Soap-Thickener Induced Local Pressure Fluctuations in a Grease-Lubricated Elastohydrodynamic Point Contact
Authors: Åström H , Venner C H 
Published: February 2007

In several experimental investigations of grease-lubricated elastohydrodynamic (EHD) contacts indications of soap-thickener formations that enter the contact area have been reported, for example by Kageyama et al. (1), Cann and co-workers (2-4) and Åström and co-workers (5, 6). While passing through a contact such soap-thickener lumps significantly disturb the film thickness by locally increasing the surface deformation. These film-thickness fluctuations must be accompanied by pressure fluctuations, knowledge of which is essential to increase insight in the phenomena determining service life and emitted noise of grease-lubricated contacts. In this paper the authors present a combined experimental/numerical approach to generate insight into such pressure fluctuations. From a fringe pattern obtained with optical interferometry (ball-on-disc apparatus) a film-thickness map is created employing image analysis. This map serves as input to a numerical algorithm for the calculation of the pressure from force balance and elastic deformation theory. Consequently, no assumptions about the rheological behaviour of grease can be made. The method was first tested out on an oil-lubricated contact. This test gave essential insight into the accuracy of the method proposed here and in the magnitude of surface texture induced pressure fluctuations. Subsequently the approach was successfully used to estimate the pressure variations resulting from soap-thickener formations in a grease-lubricated contact (between the same ball and disc).
Effects of Speed on Scuffing in Mixed Lubrication
Authors: Kelly D A , Barnes C G 
Published: February 2007

Theories of failure of elastohydrodynamic lubrication are briefly reviewed, but none that relate to scuffing per se and no general criterion that accounts for the sensitivity of scuffing to rolling as well as sliding speed are found. A theoretical investigation of micro-EHL by Baglin, for surface finishes with a lay parallel to the sliding direction, predicts boundaries in the operating condition domain to a regime of mixed lubrication in which little elastic deformation of asperities by micro-EHL is expected. A new thermal model incorporating salient features of scuffing in mixed lubrication conditions is described. It is shown to give the form of a boundary in the sliding/rolling speed domain above which localized temperatures close to melting may be expected and below which lower temperatures suggest running-in without scuffing may be expected. Results of scuffing tests on circumferentially ground discs, at sliding and rolling speeds in the range 3-10 m/s, are reported and shown for surfaces with a distinguishable mainscale wavelength in their topography, (a) to provide further support for the location of the boundaries to the mixed lubrication regime in the operating domain predicted by Baglin and (b) to match the form of the thermal model in the speed domain. Implications for engineering practice are briefly discussed.
An Expert System for the Integrated Design of Heat Exchangers
Authors: Abou-Ali M G , Beltagui S A 
Published: February 2007

The selection of a shell-and-tube heat exchanger type and geometry is one of many engineering applications, where a wide range of specialized knowledge is available as qualitative rules that can be incorporated in an expert system. This paper presents a technique used for building a knowledge-base system utilizing object-oriented expert system shells. The described steps of system development are: identifying the sources of information, building the knowledge base and finally the production of the runtime program. The constructed prototype system assists the designer in making decisions about fluid allocation, selection of TEMA (Tubular Exchanger Manufacturers Association) shell type, bundle, heads and various geometrical details. The ultimate aim of developing an expert system of this type is to achieve an integrated design procedure covering all considerations from initial selection to the final thermohydraulic and mechanical design.
Structural Failures of Bulk Carriers
Authors: Jubb J 
Published: February 2007

Structural failures of bulk carriers continue at a steady and unacceptable rate, claiming some 150 lives per year. This paper explains why bulk carriers are vulnerable to structural failure either because side shell plating falls out allowing ingress of seawater or the deck cracks open. Inadequate detail design, material without guaranteed fracture toughness and limitations of current inspection programmes are identified as fundamental weaknesses. The paper includes important information from a case study of six oil bulk ore carriers prone to deck cracking. One of the group of six which sank in 1980 was traced 4200 metres down on the floor of the Pacific Ocean in June 1994 and the results of this initial search are reviewed. There is a genuine need to go back to basics. Designing from first principles to determine local stresses is an important first step rather than the current use of prescriptive rules. All subsequent steps in bulk carrier construction and maintenance should be subject to a penetrating review.
The Analysis of Leakage in a Twin Screw Compressor and its Application to Performance Improvement
Authors: Fleming J S , Tang Y 
Published: February 2007

The performance of a helical screw compressor is influenced more by the internal gas leakages than by any other thermo-fluid aspect of its behaviour. Six separate types of leakage path can be identified. Only the cusp blow holes have a constant geometry; every other path has a geometry and resistance to flow which varies (periodically) in a manner unique to it. The pressure difference driving the gas along a leakage path also varies (periodically) and does so in a manner that is not the same for every leakage path. This is quite obviously a complex problem requiring insight in modelling the thermo-fluid behaviour and the solution of a large number of simultaneous equations. The distribution of leakage through the various leakage paths within the machine is important for the improvement of the compressor performance. A method of determining the aggregate leakage through each path individually over a complete compression cycle is required to enable this study to be conducted. The authors have constructed a mathematical model of the complete compressor thermofluid process which is suitable for this purpose, its macropredictions having been verified against measured data derived from a test compressor. The nature of its micropredictions and their verification, that is for each leakage path, are the subject of the paper proposed here. Analytical techniques are proposed and experimental methods are discussed. The influence of different rotational speeds on the leakage is considered. Also discussed is the manner in which the leakage distribution prediction could be used to optimize a compressor design.
Diesel Locomotive Reliability Improvement by System Monitoring
Authors: Fry K N 
Published: February 2007

System monitoring for reliability (SMR) involves monitoring critical parts of a vehicle and informing the owning business of an impending fault. Diesel locomotives offer the largest opportunity for such systems and British Rail Research has developed a system designed to improve Class 47 locomotive reliability. The vehicle-mounted equipment comprises a computer that continuously monitors the condition of the vehicle through sensors at key points. The computer is connected to a radio telephone and modem and a GPS satellite navigator. The key elements in the success of the system are the automated analysis of data on-board the vehicle and its ability to call for help ahead of the occurrence of service failures. The business interface is through a Windows based information display which runs on a personal computer connected to the public telephone network. This controls the display of messages from monitored vehicles and allows vehicles to be interrogated to check on current condition. When fully implemented, a reduction in technical casualties of 40 per cent is anticipated. There are additional financial benefits from efficiency improvements and vehicle maintenance cost savings.