bluuebunny/crossref_metadata_2025 huggingface dataset:
Similarity Considerations on Wall Heat Losses in Internal Combustion Engines
Authors: Eilts P
Published: February 2007

The drop in wall heat losses with increasing engine size is shown not to be due to the decreasing surface-volume ratio, because this influence is compensated by the engine speed, which also drops. Instead, the heat-transfer coefficient decreases as the cylinder bore becomes larger. The dependence of the heat-transfer coefficient on engine size is explained using Reynolds' analogy.

This dependence can be used to determine approximately changes in wall heat losses resulting from differences in engine size and the subsequent effects on indicated efficiency. It is found that only a minor part of the differences in efficiency between small and large engines is due to size-dependent changes in wall heat losses.
Overview of Condition Monitoring Methods with Emphasis on Industrial Fans
Authors: Cory W T W
Published: February 2007

In any industrial fan, the rotating elements are located within some form of bearing arrangement. Defects, such as unbalance, will lead to an increase in vibration which is transmitted via these elements to the fan supports. As the bearings wear or as impeller balance deteriorates due to the effects of erosion, corrosion or dust build-up, there will be a corresponding increase in vibration magnitude. The rate of change of amplitude is a useful indication of the fan's ‘health’. The paper considers the fundamental equation of vibration and the disturbing forces involved. It is shown that a baseline fan signature is necessary if maximum benefits are to be achieved by any fan health programme. Ultimately, well-designed and installed bearings will fail due to fatigue. The concept of L10 life is also introduced and some of the methods for predicting the onset of failure are described.
A Study on Prediction of Welding Current in Gas Metal arc Welding Part 2: Experimental Modelling of Relationship Between Welding Current and Tip-to-Workpiece Distance and its Application to Weld Seam Tracking System
Authors: Kim J W , Na S J
Published: February 2007

The weld joint tracking sensor is indispensable to improve the flexibility of the arc welding robot application. Recently, some sensing methods that utilize the electric arc signal, or more correctly the welding current in gas metal arc welding (GMAW), have been developed and are prevalently in use. The welding current, however, is directly affected not only by the tip-to-workpiece distance, but also by the welding voltage and wire feed speed.

Thus a model that is able to determine the welding current in response to the tip-to-workpiece distance was proposed for the gas metal arc welding process. The model was developed by using the factorial experiment and least-squares method to the variables of welding voltage and wire feed speed.

The relationship between welding current and tip-to-workpiece distance determined by the proposed model was compared with the experimental ones and it was revealed that both the results show good agreement within the considerably wide range of welding conditions.

The model was used for developing a weld seam tracking system which controls the moving speed of a welding torch in the height direction. It could be shown that there is a successful capability of seam tracking in flat welding of V-groove butt joins. Furthermore, the model can be used for the analysis of the weld pool formation and weld bead geometry, and also for the determination of appropriate process parameters.
A Three-Dimensional Rigid-Plastic Finite Element Analysis of Spur Gear Forging Using the Modular Remeshing Technique
Authors: Yang D Y , Lee N K , Yoon J H , Chenot J L , Soyris N
Published: February 2007

In the three-dimensional finite element simulation of forging processes, the design of meshes in initial billets, as well as in intermediate remeshing stages, plays the most important role because of the fast mesh degeneracy. In the present paper, a new systematic approach of three-dimensional remeshing, so called modular remeshing, is proposed for the finite element analysis of forging. In order to show the effectiveness of the method, forging of a spur gear is simulated by using several basic modules by the general rigid-plastic finite element code (1, 2, 3) developed for cold forging. The computational results show that the computation can be effectively carried out using the proposed concept of modular remeshing and it can be extended to other more complicated forging processes.
On the Applicability of Modal and Response Representations in the Dynamic Analysis of Machine Tool Spindle Bearing Systems
Authors: Brandon J A , Al-Shareef K J H
Published: February 2007

The study reinforces the generally held view that the stability of the cutting process in single-point cutting operations is dominated by the response characteristics of a single mode of the spindle-bearing systems. The common practice of evaluating frequency response functions at the cutting zone achieves the objective of ascertaining the machine's chatter stability. It does not, however, give any indication of the effect of resonance of higher modes on the long-term performance consistency. The results of the study suggest that this can be assessed by examination of the modal characteristics of higher frequency modes which have significant responses at the location of the bearings. The analysis is illustrated by consideration of two typical machine tool spindle-bearing systems.
Design or Decline—A National Emergency?
Authors: Wray G R
Published: February 2007

This paper draws attention to the demise of British manufacturing and stresses the importance of design. It makes clear that unless there is a change in attitude to the role of the professional engineer Britain's manufacturing base will continue to decline with markets steadily being lost to countries with a better motivated workforce.
A Study on Heat Flow in Circumferential Pipe Welding Using a Semi-Analytical Finite Element Method
Authors: Lee H-J , Na S-J
Published: February 2007

The heat flow during circumferential welding of a small-diameter aluminium pipe, which cannot be assumed to be in the quasi-stationary state because of heat accumulation, was analysed by employing a semi-analytical finite element method. The circumferential distribution of arc heat flux and temperature was simulated in the form of an expanded series to calculate the three-dimensional heat flow with a two-dimensional solution domain. The arc heat distribution, assumed as a Gaussian form, was expressed in several circumferential line heat sources by using the Fourier series expansion. The solution domain was divided into two sub-domains to apply the two types of series with two different numbers of the expanding term, which results in the reduction of the calculation time.

The thermal cycles and isotherms in the rz plane calculated by using the proposed semi-analytical finite element method agreed fairly well with the experimental results adopted from a reference. Due to the heat buildup the fusion zone increases in its size as the welding proceeds. The temperature near the heat source rises also as the welding proceeds, but the shape of the circumferential temperature distribution of a ring element was maintained almost unchanged during the entire welding process except the welding start. The proposed semi-analytical finite element method could be considered as very useful for analysing the heat flow in circumferential welding of small-diameter pipes because of its simple formulation and short computing time.
Statistical Theory of Machine Tool Stability
Authors: Baradie M A El
Published: February 2007

Machine tool chatter is essentially a statistical phenomenon. The dynamic characteristics of the machine tool structure as well as the dynamic coefficients of the cutting process are statistical quantities that show scatter when determined in repeated tests. In this paper a generalized statistical theory of chatter has been developed. This takes into consideration the scatter of the dynamic data of the machine structure and/or that of the dynamic cutting coefficients.

The dynamics of the cutting process has been presented by a mathematical model, based on deriving the cutting coefficients from steady state cutting data. The dynamics of the machine tool structure and the cutting process, being input to the theory, were determined experimentally.

At the thresholds of stability, the statistical variations due to the dynamic cutting coefficients amount to ±17 per cent at the 99 per cent confidence level, while the statistical variations due to the structure dynamics amount to ±5.2 per cent only, at the same confidence levels.

Therefore the predicted thresholds of stability can be specified only in terms of mean values with confidence limits.
Intelligent CNC for Grinding
Authors: Rowe W B , Allanson D R , Pettit J A , Moruzzi J L , Kelly S
Published: February 2007

The aim of this research was to improve productivity in grinding by bringing together process technology and microprocessor technology in an adaptive CNC system. The main objective was to produce parts satisfying specified geometrical, metallurgical and surface finish requirements. A secondary objective was to perform grinding under optimal conditions at a maximum production rate. In order to facilitate the application of a flexible range of strategies for control of the grinding process it was decided to formulate a modular conceptual framework. A variety of strategies and process models were incorporated within the framework according to the requirements of the process in question. This philosophy can be extended to a range of processes. The system was implemented using an OSAI A-B 8600 controller to control a Cincinnati centreless grinding machine. Initial production trials proved satisfactory in that the system ‘learned’ the properties of the parts produced, produced parts within specification and reduced the floor-to-floor time.
A Study on Arc Sensor Algorithm for Weld Seam Tracking in Gas Metal Arc Welding of Butt Joints
Authors: Kim J-W , Na S-J
Published: February 2007

The positional accuracy requirement of the welding torch with respect to the weld seam is the major impediment in arc welding robot applications. The weld seam tracking sensor is essential to improve the flexibility of arc welding robot applications.

In this study, an arc sensor which utilizes the electrical signal obtained from the welding arc itself was developed for gas metal arc welding of butt joints. In order to overcome the fluctuation in the welding current signal, the current signal was fitted to a curve which is inversely proportional to the trace of the tip-to-workpiece distance by using the quadratic curve-fitting method. The availability of the curve-fitted welding current signal was investigated and the seam tracking results of the system that uses the curve-fitting method were compared with the ones of another system that controls the moving speed of the welding torch in the height direction.
A Study on Three-Dimensional Transient Heat Flow in Circumferential GTA Welding of Pipes Using Periodicity Conditions
Authors: Lho T-J , Na S-J
Published: February 2007

A transient three-dimensional finite difference mode (FDM) of the heat flow in the circumferential GTA welding of pipes was developed and applied to calculate the temperature distribution in the workpiece. In order to minimize the computing time required for solving the FDM equations as much as possible, the alternating direction implicit (ADI) scheme which makes use of the tridiagonal matrix algorithm efficiently was adopted.

Based on the characteristics of the pipe welding process, the periodic boundary condition was applied to calculate the temperature distribution in the 8 direction. For treating the moving heat source effectively, the grid meshes with variable spacings were regenerated at each time step. In order to decrease the interpolating error by grid remeshing, the temperature values at new meshes were interpolated from those at old meshes by using the periodic spline function. The temperature-dependent thermal properties, the latent heat and the convective and radiative boundary conditions were included in the model. The calculated sizes of the fusion and heat-affected zone were compared with the observed values after experiments.
Balancing of Rotating Machinery
Authors: Parkinson A G
Published: February 2007

An important form of vibration experienced by rotating machinery in a wide range of applications is that due to inherent unbalance. Rotating machinery may incorporate either rigid or flexible shafts and balancing procedures for both cases are discussed, but emphasis is given to a review of techniques for the high-speed balancing of flexible shafts. Reference is also made to the main International Standards in the field.
Elastohydrodynamie Lubrication of Big-End Bearings Part 2: Ratification
Authors: Aitken M B , McCallion H
Published: February 2007

The elastohydrodynamic analysis developed in Part 1 of this work is ratified against previous Ruston and Hornsby big-end studies. Sufficiently close correlation with published in situ film-thickness measurements allows big-end bearing performance to be determined with some confidence; significant new insight was obtained.

Elasticity body forces from connecting-rod motion were found to be an integral component of the big-end representation; it is a prevalent misconception that these forces can be neglected from theoretical as well as experimental test-rig works.

Film collapse mechanisms, likened to vapour cavitation, were observed in the dynamically loaded elastic bearing; these were not detected in equivalent rigid bearing simulations.

Cyclic minimum film thickness was observed during inertial loading, irrespective of gas force loading. Two separate minimum-film conditions were identified: one in the connecting-rod's neck and a second, at higher load, in the rod's cap. The second condition is critical from a design standpoint; significantly thinner films are predicted than by rigid bearing theory.
Damping in Structural Joints Subjected to Tangential Loads
Authors: Padmanabhan K K , Murty A S R
Published: February 2007

Metallic mating surfaces in machine joints offer an excellent source of energy dissipation, resulting in damped dynamic structural response, for example in machine tools. This paper describes the results of a series of experiments where the energy loss per cycle occurring at preloaded flat metallic interfaces subjected to cyclic tangential forces are measured. The effects of certain pertinent joint variables on the joint damping effectiveness are investigated. The results should be useful to the designers of machine tool structures, where damping occurring in joints is important.
On the Natural Frequencies of High-Speed Spindles with Angular Contact Bearings
Authors: Wang K W , Shin Y C , Chen C H
Published: February 2007

Experimental evidence has shown that the natural frequencies of a high-speed spindle decrease with increasing rotational speeds. While this phenomenon is important to the design and operation of high-speed machine tools, it has not been thoroughly analysed. This paper presents a spindle model that can be used to analyse the changes in bearing stiffness and the natural frequencies of the system. It is shown that the system dynamics can vary substantially due to bearing centrifugal force and shaft gyroscopic effects. The findings can be utilized in optimizing the design and control of high-speed spindle systems.
Calculation of the Unsteady Flow in Exhaust Pipe Systems: New Algorithm to Fulfil the Conservation Law in Pipes with Gradual Area Changes
Authors: Van Hove W , Sierens R
Published: February 2007

In this paper a new calculation method is proposed for the gas flow in tapered pipes. The model is adapted to the hybrid method of characteristics. The key idea of the model is to concentrate any area change over one mesh length in the mesh points instead of using an area gradient along the characteristic lines.

The model has the disadvantage that the computing time increases, but it has the great advantage that the law of conservation of mass is fulfilled for the whole pipe length, even for important area changes. This allows the other advantages of the method of characteristics to be retained, for example the treatment of discontinuities in temperature or gas composition, without compromising the mass balance of the engine.

In a test case it is shown that the new model correctly predicts the mass flowrate at all mesh points, which is not the case for the original hybrid method or other adapted versions. Tests for a real engine situation give results for the conservation of mass that are comparable with the best results of the Lax-Wendroff method.
Geometric Analysis and Optimization of a Symmetrical Watt Six-Bar Mechanism
Authors: Dai J S , Kerr D R
Published: February 2007

This paper describes the synthesis of a mechanism, with the aim of producing a virtual hinge device whose instantaneous centre varies in position as little as possible, and gives an analysis of the relative instantaneous centres of six bars that form a Watt six-bar linkage mechanism. A new expression of the three-centre theorem is successfully applied to the six-bar linkage mechanism by combining geometric representation with vector analysis. Based on this analysis, a formulation for optimization has been established, and the mechanism has been optimized to minimize the movement of the instantaneous centre of one of the bars. A dimensionless example is given.
On the Localization of the Vibration Mode of a Sub-Structural Chain-Type Structure
Authors: Zhong W X , Williams F W
Published: February 2007

The localization phenomenon for high-frequency vibration modes of imperfectly repetitive structures is considered by using an analogy between computational structural mechanics theory and optimal control theory. In particular, the simplectic matrix method of control theory is applied to the dynamic external stiffness matrix of a typical repeating sub-structure. The eigensolution of the simplectic matrix for the case where the sub-structures are connected by a single line of springs is solved analytically. This gives the passband for the frequency of the travelling waves along the sub-structural chain and the corresponding eigenmode. Hence it is shown how the influence of local disturbances of the sub-structural chain on the behaviour of the whole chain can be considered analytically, thus explaining the mechanism of the localization of high-frequency vibration modes. Numerical examples are therefore not needed, although a few are introduced solely to confirm the correctness of conclusions already drawn from the analytical method.
Metal Fatigue—Past, Current and Future
Authors: Miller K J
Published: February 2007

Metal fatigue has been a problem for more than 150 years, but because of rapid developments in fracture mechanics analyses, possibly at the expense of the traditional approach based on cyclic deformation processes, afar better understanding of fatigue failure behaviour has recently been achieved. Consequently the engineer now has the basic tools at his/her disposal to make good assessments of the numerous factors that control the fatigue lifetime of engineering materials, components and structures.

Additionally, more intensive interdisciplinary research studies involving chemists, materials scientists, mathematicians and physicists—but engineering led—have generated both greater insights into long-known industrial problems and routes to required solutions. This paper traces the growth of recent developments in understanding metal fatigue from the days of our mentors to the present day, and concludes with a brief review of some future research areas that are now available for exploitation.
An Improved Correlation for Two-Phase Frictional Pressure Drop in Boiling and Adiabatic Downflow in the Annular Flow Regime
Authors: Klausner J F , Chao B T , Soo S L
Published: February 2007

An improved correlation is presented for annular two-phase frictional pressure drop data for vertical downflow. An ideal dimensionless film thickness based on the vapour volume fraction, a characteristic friction factor based on the two-phase frictional pressure gradient and a Weber number relevant for the interfacial capillary wave structure are the correlating parameters. The proposed new correlating scheme is tested against a wide range of data obtained in this investigation for refrigerant R11 in forced convection boiling and in adiabatic test sections of 19 mm cylindrical cross-section as well as published data for air-water and air-glycerine solution mixtures in the annular flow regime. Over 80 per cent of the measured values fall within ±30 per cent of those predicted from the correlation. Due to the wide range of liquid film thickness covered, 0.05–2.9 mm, its validity extends past the range where previously reported downflow pressure drop correlations fail. A paradox connected with previously reported annular downflow pressure drop correlations based on the liquid-vapour interfacial shear stress is pointed out. Upflow frictional pressure drop data in the annular flow regime can also be correlated by the proposed scheme.
Practical Rotary Encoder Accuracy Limits for Transmission Error Measurement
Authors: Smith J D
Published: February 2007

Errors of angular position on encoders used for transmission error measurement were investigated to determine the practical limits of accuracy. Computer correction can be used to eliminate consistent errors on the encoders but errors remain, attributable to electrical noise, bearing errors and friction effects. Practical limits on the calibration and usage of the encoders for individual harmonics of once per revolution frequency and for a given angular position were established.
Testing and Technology
Authors: Ashley C
Published: February 2007

Each year the new Chairman of the Automobile Division is given the opportunity to give a review. This can cover a wide variety of subjects including the history of his company's products, some new technology developed by his organization, but frequently it is a reflection on his own experience in the engineering scene. This is not intended as a narcissistic exercise but one from which other people can benefit, particularly young engineers, in giving an insider's view of life as a professional engineer and some of the reasons and background to decisions and activities that have taken place in the profession.
Practical Tools for Vehicle Impact Simulation Part 1: Vehicle Impact Simulation in Rover Group
Authors: Leach J H
Published: February 2007

Rover Group has seen rapid growth in vehicle impact simulation techniques in recent years. This has been brought about partly by the increasing power of computer hardware and software, and partly because of increasing legislative and consumer pressure. This paper describes the development of impact simulation within Rover Group, from simple discrete element mass and spring models to complex component non-linear finite element models. It subsequently describes how all of these approaches were combined to provide an integrated modelling capability which allows the complexity of models to evolve as design and development progresses, and concludes with a description of how these modelling methods are being applied to the design of new vehicles within Rover Group.
Power Flow and Ratio Sensitivity in Differential Systems
Authors: Lloyd R A
Published: February 2007

It has been known for some time that, in single-degree-of-freedom differential systems, the sensitivity of the overall transmission ratio to a change in ratio of one of the differentials is proportional to the fraction of the input power flowing in the relevant differential. A complete and general proof of this theorem is presented, using matrix algebra, determinants and a coherent subscript notation.

The theorem provides a direct method for calculating the internal power flows during the synthesis of multi-epicyclic systems, and defines a theoretical limit to the ratio range and efficiency of a split-path continuously variable transmission.

Analysis of the Allison WT is used to illustrate application of the theory to a change-speed transmission.
A Numerical Study of Fuel Evaporation and Transportation in the Intake Manifold of a Port-Injected Spark-Ignition Engine
Authors: Brown C N , Ladommatos N
Published: February 2007

The paper presents a computer simulation of mixture preparation in the inlet port of a port-injected spark-ignition engine operating at low load and low speed. The solution of the models at successive crank angles allows mixture preparation in the port to be investigated under steady engine operation. The main features of the simulation are: monosize spray of a single-component fuel, evaporation of the spray droplets during flight, evaporation of the fuel film, fuel film flow along the manifold walls and unsteady air flow during the induction period. Use of the simulation allowed investigation of the effects of: manifold wall and air temperatures, spray-droplet size, injection timing, injector aim, fuel voltatility and the use of methanol as the fuel.
High-Integrity Software for Automotive Applications
Authors: Cullyer W J
Published: February 2007

This paper reviews some possible techniques for the future development of high-integrity, high-reliability software for use in critical applications in road vehicles. The customer is concerned with the overall reliability of electronic equipment in a vehicle. High reliability requires designers both to minimize the possibilities of random failures and to reduce or eliminate systematic design errors. Following a discussion of some ways in which microprocessor-based equipment can fail, formal techniques of specification and analysis are identified as possible methods for the automotive industries in the next decade. Combined with exhaustive dynamic testing and static analysis of programs, it should be possible to reduce the probability of failure in equipment based on the use of programmable microcontrollers.
‘Interlinking’—a Post-Team-Working Automotive Deployment Strategy?
Authors: Bertodo R G
Published: February 2007

Throughout the past decade, competitiveness in the automotive industry has been judged against criteria set by Japanese automakers. The evolving scenario offers little promise of relief. Indeed, only supreme mastery of time-scales, complexity and costs would seem likely to ensure survival. Against this backdrop, it would seem essential for Western companies to devise new winning formulae capable of out-performing Japanese-inspired ‘team-worked’ organizations. One company's past and planned efforts in this direction and the likely impacts on the business organization are described.
Assessing the Road-Damaging Potential of Heavy Vehicles
Authors: Cole D J , Cebon D
Published: February 2007

The relative influence of various heavy vehicle design features on road-damaging potential is discussed. Testing procedures that could be used to measure the road-damaging potential of heavy vehicles are examined. A validated vehicle simulation is used to examine some of the characteristics of dynamic tyre forces generated by typical leaf sprung and air sprung articulated heavy vehicles for typical highway conditions. The proposed EC suspension test is simulated and the results compared with dynamic tyre forces generated under highway conditions. It is concluded that the road-damaging potential of a vehicle cannot be assessed by the simplistic parametric measurement of the proposed EC test. It is questionable whether a vehicle that passes the test will be any more ‘road friendly’ than one that fails.
A Technique for the Investigation of Transient Aerodynamic Forces on Road Vehicles in Cross Winds
Authors: Dominy R G
Published: February 2007

A technique is described which allows the aerodynamic characteristics of the cross wind gusts that are commonly experienced by passenger vehicles to be correctly represented in wind tunnels. This characterization includes the modelling of wind strength and direction, gust duration and the cross wind boundary layer. The technique uses conventional wind tunnel model and instrumentation configurations and relies upon a second nozzle and shutter arrangement to give complete control over the profile and duration of the cross wind gust. Data from some initial proving tests are presented to demonstrate the potential of the method.
Tribochemistry and EP Activity Assessment of Mo—S Complexes on Steel Balls of Different Compositions
Authors: Singh T , Verma V K
Published: February 2007

The paraffin oil admixtures with some Mo-S complexes were evaluated as potential EP lubricant additives in the ‘four-ball test’ using 12.7 mm diameter steel balls of different compositions. The oil-soluble additive, bis(oxinato)-μ-oxo-μ-sulphido-dioxomolybdenum (V), was found to be quite effective against the steel balls of different compositions. The tribochemistry and topography of the used ball specimens were examined by means of scanning auger electron spectroscopy and scanning electron microscopy respectively.
Failures of Liquefied Gas Storage Vessels
Authors: Lihou D A
Published: February 2007

Pressurized storage tanks are robust structures and catastrophic failures are very rare events. Nevertheless, owing to the rapid rate at which the liquid contents will be released from an open valve or a fractured pipe and the subsequent flashing of the liquefied gas, these types of storage are often the criteria by which a site is classed as a major hazard under the Control of Industrial Major Accident Hazards (CIMAH) Regulations. The listed materials include ammonia, chlorine, ethylene oxide and flammable gases (boiling point <20°C).

Methods of predicting leakage rates from various types of breach are presented with tables of physical property parameters for the more common materials, which simplifies the calculation of leakage rates. Brief details are given of some notable accidents involving liquefied gas storage failures to illustrate the following lessons for designers:

1. Continually review the field data concerning chemical attack from contaminants, particularly of the stress corrosion type. 2. Ensure that materials will retain adequate strength at the temperature extremes that may be encountered during abnormal conditions. 3. Design and locate fixtures and fittings so that they are operable and maintainable, paying particular regard to draining facilities. 4. Continually update the codes for passive and active protection against fire and impact, in the light of losses occurring worldwide; for example by abstracting reports from Lloyd's Register. 5. Be alert during hazard and operability study reviews to chance contamination of the tank contents with other process fluids which can cause the tank to become a ‘eactor vessel’ with rapid evolution of heat and pressurized gas.
Energy Absorption on the Sea Bed
Authors: Smith J D
Published: February 2007

The problems of pipeline protection on the sea bed are discussed and a particular practical solution for energy absorption is described. Laboratory tests confirm the design predictions.
Transverse Taper and Instability in Four-High Rolling
Authors: Saxl K
Published: February 2007

Transverse instability in four-high mills is controlled by the usual guiding methods which on occasions are inapplicable. Its main cause is tilting of the work rolls on their backing rolls. A simplified conception of the strain distribution yields a manageable relationship between asymmetry of load and the roll gap taper. The proximity change between the work and backing roll chocks due to tilting is large compared with the change by symmetrical load and is thus potentially suitable for a signal to control guiding. Transverse rigidity is considered.
An Analysis of the Body-Bending Vibration of a Bogie Vehicle for an Evaluation of the Ride Quality with Deflated Airsprings
Authors: Tanifuji K
Published: February 2007

This paper describes an analytical study on the effects of secondary airspring deflation on the ride quality of a bogie vehicle. The vertical vibration characteristics, containing body-bending modes, are investigated for the situation where the body is excited by running over vertical track irregularities. The vibrations caused by the track irregularity are evaluated with the value of the ride quality level, LT, calculated from the vehicle body acceleration, for conditions with the airsprings normal or deflated. In the evaluation, the running speed is varied and a suitable speed reduction is calculated for the train operating with the airsprings deflated.
Reanalysis by Modal Synthesis of Railway Vehicle Structures
Authors: Coutellier D , Ravalard Y , Oudin J
Published: February 2007

The development of validation criteria for the dynamic conception of complex structures has resulted increasingly in the use of iterative intensive analysis procedures, the cost of which can be restrictive in terms of calculation times when using the established direct analysis methods. Modal synthesis, as outlined in the following article, has proved itself to be very effective as a method of reanalysis, particularly related to the dynamic behaviour of railway vehicle structures.
Steering and Stability of the Bogie: Vehicle Dynamics and Suspension Design
Authors: Wickens A H
Published: February 2007

Recent progress in the development of railway vehicle bogies and other forms of running gear is reviewed, with particular reference to the conflict between stability and curving. It is shown how the demand for much greater performance in terms of speed, ride quality and cost of ownership generated by the renaissance of the railways which has occurred in the last quarter century has been matched by a much more scientific and innovative approach to vehicle dynamics. In this approach, a correct physical understanding of the mechanics of the railway bogie has been converted via mathematical modelling and advanced computer techniques into a tool for innovation which has generated practical improvements in suspension technology.
Netherlands Railways New Generation Multiple Units, Sm'90; Concept Definition for Minimum Life-Cycle Costs
Authors: Blair I F
Published: February 2007

This paper summarizes the work of Netherlands Railways to specify systems and components with a view to achieving low life-cycle costs for new rolling stock. SM'90 is a prototype for a new generation of multiple units.
Theoretical Modelling of Wheel-Rail Noise Generation
Authors: Thompson D J
Published: February 2007

The major source of noise from railways, particularly at high speeds, emanates from the wheel-rail region. This wheel-rail rolling noise is generally attributed to structural vibrations of the wheels and rails, excited from the contact patch area. The main excitation is caused by the wheel and rail surface roughness (undulations), which introduce a relative vibration between the wheel and rail.

A linear mathematical model of wheel-rail interaction has been developed which incorporates detailed predictions of the vibration properties of the wheel, the rail and the contact area. Results of this model give good agreement with experimental results as long as the roughness levels are not too severe.

Models of the noise radiation from the wheel and rail vibrations have also been developed, from which it is apparent that the vibrations of both the wheel and rail are significant sources of noise and that the vibrations of both components need to be reduced if a significant reduction in noise is to be achieved.
Some Experiences of Advanced Manufacturing Cells at British Aerospace Warton Unit
Authors: Duxbury J M
Published: February 2007

British Aerospace Warton Unit is using several methods to reduce the makespan of aircraft manufacture. To illustrate the principles three production facilities, which use different approaches to achieve significant makespan reductions, are described.
Vibration Analysis of Gas Turbines by an Intelligent Knowledge-Based System
Authors: Allwood R J , Christie P I
Published: February 2007

Monitoring the vibrations of a gas turbine during its development tests requires manual inspection and interpretation of thousands of diagrams displaying measurements made by hundreds of strain gauges and other transducers. This paper describes a prototype knowledge-based computer system to assist in this task. The features on each diagram are located by image processing methods and interpreted by stored knowledge which represents the experience of vibration engineers. The objective of the system is to distinguish the relatively few diagrams which have unusual features from the majority which have only expected features, leaving the interpretation of the unusual diagrams to real experts.

The paper gives an overall description of the problem of vibration in gas turbines and some details of the image processing and knowledge processing methods used, and shows some examples of typical diagrams handled by the system.
The Development of a Surgeon Robot for Prostatectomies
Authors: Davies B L , Hibberd R D , Ng W S , Timoney A G , Wickham J E A
Published: February 2007

The removal of prostatic tissue through transurethral resection of the prostate (TURP) is an operation that can require considerable skill from a surgeon as well as being a lengthy procedure. The potential for using robotic techniques was investigated in a preliminary feasibility study using a standard six axis ‘Puma’ robot. This led to the construction of a manually operated ‘safety frame’ which has been shown to be effective through clinical trials on 30 patients. A special-purpose robot, based on the design of the manual frame, has now been constructed. Some of the safety issues are discussed which make this procedure an ideal candidate for a robotic device.
A Quantitative Assessment of Orthoses for Stabilization of the Anterior Cruciate Ligament Deficient Knee
Authors: Liggins A B , Bowker P
Published: February 2007

Knee braces are used to restore functional stability to joints which have become unstable as a result of the traumatic disruption of the anterior cruciate ligament. A number of quite different designs of knee brace have evolved and are used clinically in the management of these injuries although to the authors' knowledge little quantitative data are available on their relative mechanical characteristics. This paper reports the results of static testing carried out to determine the stiffness characteristics of 24 commonly used braces. The data obtained indicated clear differences between different brace designs with the stiffest having values closely approaching that achieved physiologically in uninjured joints, and the least effective having minimal stiffnesses. It was found that the mechanical performance of any individual brace was determined by three factors: the mechanical characteristics of the individual components from which it was constructed, the structural integrity of its design, and the interaction of the brace with the limb during loading.
Vibration Analysis of a Blood Processor Centrifuge with Anti-Twister Mechanism
Authors: Herman H , Dastane A , Sofer S
Published: February 2007

This paper deals with the vibration analysis of a blood processor centrifuge with an anti-twister mechanism. Blood processors that employ anti-twister mechanisms are becoming increasingly popular because they cause relatively less damage to the blood than the conventional ones, which employ rotating seals. Knowledge of the vibration response of the device in its operating regime is important for trouble-free operation.

A simple, three-degree-of-freedom, lumped-parameter, torsional-mode model is presented here. This model was used to analyse an existing blood processor. On comparing experimental and analytical values, it was found that the fundamental frequency as predicted analytically is within 19 per cent of the experimental value; the predicted second harmonic is about 28 per cent higher than the experimental one. Thus the proposed model predicts the fundamental frequency with reasonable accuracy. In design, the goal is to keep the operating frequency of the device sufficiently above the fundamental frequency to avoid resonance problems.
An Investigation into the Fixation of Hip Replacements
Authors: Humphreys P K , Orr J F , Bahrani A S
Published: February 2007

This paper describes an experimental study of hip prosthesis stems fixed with bone cement in model femora and subjected to cyclic loading. Loosening of the stems did not occur due to fatigue of the bone cement, even when reduction of medial support from the calcar had been simulated. Measurement of stresses in the cement layer and comparison with published properties of bone cement indicated that fatigue failure was not likely under the experimental conditions. Fatigue failure of cement could not be solely regarded as initiating loosening. It is concluded that the results uphold theories that biological factors must also contribute to the initiation of loosening, rather than being a response to mechanical failure.
Tribology of Human and Artificial Joints
Authors: Unsworth A
Published: February 2007

Studies of human joint lubrication mechanisms have led to the conclusion that under normal healthy conditions they are fluid film lubricated. The main features responsible for allowing this mechanism to operate are the dynamic nature of the loading and the compliance of the bearing surfaces (articular cartilage).

In contrast, artificial joints, being made of much more rigid materials, have been demonstrated to be lubricated by a mixed regime, where some load is carried by the fluid film and some by solid to solid contact. Since some surface contact takes place then wear remains a problem and friction is much higher than in human joints.

The use of compliant surface bearings for artificial joints has been explored and shown to be of great advantage, reproducing the effects of natural joints. However, elastomeric materials are known to degrade in aqueous solutions so this aspect has been examined to ensure a reasonable life in the human body.

Joints of the lower limb—hip, knee and ankle—have similar load and motion patterns and behave in a similar way in terms of lubrication. Joints of the hand are not in any way similar in their behaviour and so a typical upper limb joint, the finger, has been studied to see if improvements can be made to the design of replacement artificial joints. Novel suggestions like plastic on plastic joints have been shown to be an alternative which is worthy of further consideration.
Wear Resistance and Microhardness of Human Teeth
Authors: Remizov S M , Prujansky L Y , Matveevsky R M
Published: February 2007

The dependence between the wear resistance and microhardness of the different tissues of human teeth has been studied. During these experiments the proportionality between the wear volume of the tissues under study and their microhardness (by indentation and scratching methods) has been observed.
Axial Rotation of Lumbar Intervertebral Joints in Forward Flexion
Authors: Pearcy M J , Hindle R J
Published: February 2007

This paper examined the mobility of intervertebral joints in axial rotation in a neutral and in two flexed positions. Torsion tests were conducted in vitro on specimens of isolated intervertebral joints in a rig specifically designed to apply torsion without imposing a fixed axis. This permitted the specimens to rotate about their own mobile axis of axial rotation. In addition the specimens were flexed about previously defined physiological axes of sagittal flexion in order to simulate movements as close as possible to those seen in life. It was shown that some intervertebral joints do exhibit an increased ability to rotate when in some degree of sub-maximal flexion dependent on the morphology of the zygapophysial joints. In full flexion axial rotation is limited, most probably by tightening of the posterior ligaments and zygapophysial joint capsules. This study lends evidence to the argument that torsion alone is insufficient to damage the intervertebral disc but a combination of flexion and torsion will increase its vulnerability to injury.
Stress Analysis of Cushion form Bearings for Total Hip Replacements
Authors: Jin Z M , Dowson D , Fisher J
Published: February 2007

Cushion form bearings comprise a thin layer of low elastic modulus material on the articulating surface of the bearing, which can deform to help preserve a film of lubricant between the bearing surfaces and therefore reduce friction and wear. The long-term function of this type of bearing is dependent on the strength and durability of this compliant layer. Finite difference and finite element methods have been used to analyse the stress distribution in the compliant layer of cushion form bearing for artificial hip joints under physiological loading conditions. A good agreement between finite difference and finite element methods was found. Under normal loading, the highest value of the maximum shear stress was found to be at the interface between the compliant layer and the more rigid substrate close to the edge of the contact. The values of maximum shear stress in the centre of the contact close to the articulating surface were lower than in the equivalent Hertzian contact. A friction force acting at the surface had little effect on the stress distribution for coefficients of friction less than 0.05. However, for higher values of friction coefficient (larger than 0.2), corresponding to inadequate lubrication, the maximum shear stress increased by a factor of four and was found to be located at the surface. The analysis predicts that the mode of failure will be at the interface with the substrate under fluid film or mixed lubrication conditions and at the articulating surface when the bearing runs dry with higher levels of friction. Both failure modes have been observed experimentally under the conditions specified.
Morpho-Tribo-Mechanical Characteristics of the Articular Cartilage in Animals under Conditions of Hypokinesis
Authors: Slesarenko N A , El-Mahdy T O , Gavrjushenko N S
Published: February 2007

The influence of activity upon the structure and properties of articular cartilage has been examined in two populations of fur-bearing animals. Morphological changes in cartilage of the caged animals were noted. Friction was mentioned in a vibrotribometer and it was noted that the caged animals exhibited a lower friction coefficient than the free-moving animals. In both cases the friction initially increased with age, reaching a maximum after about three years. It is concluded that prolonged hypokinesis associated with a cage-breeding regime acts like a mechanical stress factor which stimulates the development of degenerative changes in cartilage.
The Impedance Characteristics of Fluid Power Components: Relief Valves and Accumulators
Authors: Edge K A , Johnston D N
Published: February 2007

This paper describes an experimental and theoretical investigation of the impedance characteristics of various relief valves and an accumulator. The test programme involved the measurement of pressure ripples at three locations in a specially designed test circuit. From these measurements, the impedance of a component was evaluated as a function of frequency.

The experimental results are compared with mathematical models. For a single-stage relief valve, a simple orifice model has been found to be adequate. For two-stage valves, a much more complex model was considered. This was found to predict the basic trends but was not accurate.

Tests on an accumulator yielded results which correlated well with a relatively simple mathematical model. However, it is difficult to quantify the model parameters. It is concluded that for the more complex components used in hydraulic systems it is necessary to measure the impedance characteristics rather than predict them. There is a need to adopt a standard test procedure for this purpose.