bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric variation of the maximum surface temperature during laser heating with convective boundary conditions
Authors: Yilbas B S , Kalyon M
Published: October 2002

Modelling of laser pulse heating of metallic substrates reduces the experimental cost and optimizes the laser heating parameters. In the present study, exponentially time-varying laser pulse heating with convective boundary conditions at the surface is considered. The closed-form solution for temperature distribution at the surface is presented. The effects of the heat transfer coefficient ( h∗) and pulse parameter (β∗) on the time corresponding to the maximum surface temperature ( t∗Tmax is significant for h∗≥0.02. Moreover, reducing the pulse parameter lowers t∗Tmax.
Improving kinematic and structural performance of Geneva mechanisms using the optimal control method
Authors: Lee J-J , Cho C-C
Published: October 2002

A method is proposed to improve the performance of the conventional Geneva mechanism. Rather than driving the input crank at a uniform speed, this method uses optimal control theory to synthesize the speed of the crank. In this paper, design criteria are first developed based upon the elimination of the impact loading at the beginning and end of the motion cycle. In addition, three approaches to program the crank speed are introduced. In the first approach, the crank speed is designed to be optimal so as to minimize the output acceleration. In the second approach, the crank speed is determined by minimizing the input motor torque. The third approach uses the degree of wear between the crank pin and wheel slot as the index to optimize the crank speed. All design objectives are formulated as a parameterized optimization problem and solved via an efficient numerical method. Furthermore, trade-offs among the desired characteristics are taken into account by formulating the problem as a multiobjective optimization problem. Two examples are given to illustrate the design procedure.
On the dynamics of a spring-type operating mechanism for a gas-insulated circuit breaker in open operation using the Lagrange equation
Authors: Chen F-C , Tzeng Y-F
Published: October 2002

This paper investigates the dynamics of a spring-type operating mechanism of a gas-insulated circuit breaker in open operation. The vector-loop method is first used to derive the position, velocity and acceleration functions of each member of the operating mechanism. The equations of motion of the mechanism are then formulated using the Lagrange equation and solved by the fourth-order Runge-Kutta method. It has been shown in the analytical results that the breaking time of the circuit breaker is 0.076 seconds, which compares well with the experimental results.
Three-dimensional elastoplastic finite element and elastohydrodynamic analyses of journal bearings
Authors: Bahai H , Xu H
Published: October 2002

It is generally believed that cracks initiating from the surface of bearings with their line perpendicular to the circumferential direction of the shell are predominantly induced by the presence of cyclic hoop stresses in the bearing. A method is proposed in this paper where an elastohydrodynamic (EHD) analysis is combined with a full elastoplastic finite element (FE) stress analysis using a particular Fourier type of element which enables the application of non-uniform, non-axisymmetric hydrodynamic pressure loading to an axisymmetric bearing geometry. The analysis accounts for the effect of the initial interference fit and the three-dimensional pressure distribution which is obtained from the EHD analysis. Plasticity is incorporated into the analysis using the von Mises yield surface hardening rule. The analysis predicts the variation of cyclic stress and strain values in the lining material across the bearing width. It is seen from the analysis that a hoop strain variation changing from tensile in the loaded condition to compressive in the unloaded condition is responsible for the initiation of cracks at the surface of the bearing lining material.
Preliminary design of the kinematic Stirling engine using dynamic similarity and quasi-static simulation
Authors: Prieto J I , Fano J , González C , González M A , Diaz R
Published: October 2002

This paper presents a preliminary design method based on dynamic similarity and quasistatic simulation. The proposal improves methods based on Beale and West correlations and provides the engine speeds corresponding to the maximum indicated powers and the achievement of indicated power maps. The dimensionless factor of indicated power losses provides a new viewpoint for engine analysis and design. In support of the method, experimental GPU-3 test results have been reanalysed, proving the accuracy of maximum indicated power predictions and providing values of the dimensionless factor of indicated power losses. Scaling factors corresponding to strict dynamic similarity are supplied for several typical cases. Similarity relaxation criteria are also recommended to be used when strict dynamic similarity leads to inadequate specifications for the derivative. Some numerical examples illustrate the method.
Dynamic analysis of a two-gyro Anschütz compass
Authors: Ge Z-M , Jen C-W , Ku F-N
Published: October 2002

In this paper, the dynamics of the two-gyro Anschütz compass in two cases, i.e. the earth spin velocity and zero vehicle velocity case, as well as the earth spin velocity and non-zero vehicle case, are studied. The detailed exact equations of motion of this compass are obtained by Lagrange's equations. The system is studied by the linear approximation method, and these equations are solved as eigenvalue problems. The stabilities of these motions are also discussed. The analytical stabilities for two cases from the linear approximation method are checked by the numerical solutions.
Effects of ‘road friendly’ suspensions on long-term flexible pavement performance
Authors: Collop A C , Cebon D
Published: October 2002

This paper examines the effects of ‘road friendly’ heavy goods vehicle suspensions on long-term flexible pavement performance. A deterministic ‘whole-life pavement performance model’ (WLPPM) is used to calculate pavement damage due to realistic traffic and environmental loading. The traffic is modelled first as a fleet of steel-sprung heavy goods vehicles and second as a fleet of ‘road friendly’ air-suspended vehicles. The pavement life predictions are compared for the two cases and with results from a simple road damage analysis based on the ‘fourth power law’. It is concluded that changing to a fleet of ‘road friendly’ vehicles would not significantly affect the life or maintenance costs of thicker asphalt pavements (motorways and trunk roads) where the mode of failure is permanent deformation (rutting). However, the life of thinner pavements (minor roads) that fail by fatigue damage and pot-holing would be increased significantly if the vehicle fleet changed to road friendly suspensions. Predictions from the simplified fourth power law approach tend to significantly overestimate the benefits of road friendly suspensions for major road conditions compared to the WLPPM predictions. It is concluded that the potential economic benefits in England and Wales of converting to air suspensions may be only 30 per cent of those predicted by the authors of the EC ‘road friendly suspensions’ regulations.
Optimal design of rib structures using the topology optimization technique
Authors: Chung J , Lee K
Published: October 2002

The objective of this work is to search the optimal shapes and locations of ribs in order to increase the stiffness of structures using the topology optimization technique. In this approach, an initial rib structure consisting of many discrete shell elements is added to the existing structure and the optimization procedure is applied to determine the density of each element for the minimal mean compliance of the whole system. The remaining shell elements determined to have higher densities by an optimization procedure will remain attached to the structure and become the rib structure. This is different from the existing approach which tries to derive the rib design from the optimized thickness distribution of the structure. A penalty term is also introduced in the objective function in addition to the mean compliance to prohibit the intermediate densities. The mean compliance is computed by the finite element method in which each element has a variable density. Young's modulus of each element is derived by assuming a quadratic relation between the density and Young's modulus. The optimization is performed by the feasible direction method using the densities of elements as the design variables. The total material usage is used as a constraint in the optimization to provide lightweight structures.
A general analytical solution to the problem of microelastohydrodynamic lubrication of low elastic modulus compliant bearing surfaces under line contact conditions
Authors: Jin Z M , Dowson D
Published: October 2002

A general governing equation for the pressure perturbation associated with the microelastohydrodynamic lubrication action generated by asperities superimposed upon compliant bearing surfaces of low elastic modulus has been derived in this study. It has been shown that the equation derived not only governs the lubrication of the asperities superimposed upon a macroelastohydrodyn-amic contact but also the asperity lubrication of a hydrodynamic lubrication conjunction such as a parallel face seal. Analytical solutions to the governing equation have been obtained under various conditions. The main characteristics associated with the microelastohydrodynamic lubrication mechanism predicted from the present analysis have been found to be in good agreement with the full numerical solutions presented by Dowson and Jin (1, 2) for the lubrication of normal human ankle joints. Furthermore, it is pointed out that the simple analytical method developed in this study can be applied not only to a layered surface on a rigid backing, as in the natural synovial joint, but also to the more general situation of semi-infinite solids with low elastic modulus.
A unified tensor approach to the analysis of mechanical systems
Authors: Fogarasy A A , Smith M R
Published: October 2002

It is shown in this paper that all methods of dynamic analysis of mechanisms used in practice can be derived from an invariant formed from the Lagrangian equation of motion. For the dynamic analysis of mechanisms subjected to kinematic constraint conditions, the Lagrangian equations of motion are far more suitable than the Newtonian approach. Since the Lagrangian equations are tensor equations, they are valid irrespective of what kind of generalized coordinates are used. This is not so, however, when the Newtonian approach is used. It is demonstrated by a simple example that a careless use of Newtonian mechanics can lead to erroneous results.
Implications of chaos theory for engineering science
Authors: Baker G , McRobie F A , Thompson J M T
Published: October 2002

A review is presented of the applications of non-linear dynamical systems theory (or chaos theory) in mechanical, civil, electrical and chemical engineering
Triangulation-based path planning for a mobile robot
Authors: Seneviratne L D , Ko W-S , Earles S W E
Published: October 2002

A triangulation-based path planning algorithm for a mobile robot is presented. A circular robot operating in a planar polygonal environment cluttered with polygonal obstacles is considered. The free space of the robot consists of a polygonal region with polygonal holes. A method called bridge building is presented for triangulating a simple polygon with polygonal holes. The free working space of the robot is thus triangulated, resulting in an exact cell decomposition. This enables a triangulation graph to be constructed, representing the topological connectivity of the free space, from which safe paths from the start to the goal can be found. The paths are contained within free channels bounded by the obstacles and the environmental boundaries. An important feature of the process is that many segments of a selected path are parallel to the environmental boundaries. This would enable relatively simple sensing devices, such as ultrasonic sensors, to be used for correcting navigation errors. The algorithm is computationally efficient, being of O( n2) complexity.
Integral formulation of balance equations for two-phase flow through a sudden enlargement Part 2: A new interlocked volumes semi-empirical model
Authors: Attou A , Bolle L
Published: October 2002

Using the basic model already developed in the first part of the study, two different ways to eliminate the questionable assumption related to the pressure value just downstream of the enlargement will be investigated. The method is semi-empirical because correlations are used to calculate the void fraction at different sections. An intermediate section is artificially introduced and the local void fraction is calculated as if the jet would discharge into an infinite medium. Good agreement with experimental data is obtained.
Dynamics of spreader motion in a gantry crane
Authors: Cartmell M P , Morrish L , Taylor A J
Published: October 2002

This paper illustrates the steps necessary to model the dynamics of a model rubber-tyred gantry (RTG) crane as used in container-handling operations. Various modelling criteria are discussed with the emphasis placed on the importance of non-linear coupling between the chosen system coordinates. The machine is treated as three rigid bodies, these being the gantry itself, the trolley (which is constrained to lateral motion across the top beam) and the spreader. Tyre deformations and structural deflections are not considered in this work.

The paper culminates in three non-linear ordinary differential equations, which are then solved numerically for a variety of different cases. An important feature of this work is that the dynamic simulations include complicated gantry motions, not currently designed for, such as combined translations and simultaneous rotations. Such motions are more commonly encountered in mobile robots. However, RTG design needs to move in this general direction in the future if significant and potential performance gains are actually to be realized in practise. The paper concludes with suggestions for implementation of the dynamic model within a fuzzy logic control system.
Modelling the pressure die casting process with the boundary element method: Die deformation model for flash prevention
Authors: Milroy J , Hinduja S , Davey K
Published: October 2002

In pressure die casting, the thermal loads, injection pressure and clamping forces cause the individual blocks of a die to deform. This deformation results in gaps between the interface surfaces which, if big enough and in the vicinity of the cavity, permit material to seep into the gaps, causing flash. This paper describes a thermoelastic model to predict the deformation of the die so that it can be machined to prevent flash. The model is based on the boundary element method and allows the use of linear isoparametric or quadratic subparametric elements. Each die block is analysed as a separate problem. To avoid the occurrence of flash, the model suggests the amounts that should be machined from each die block. The predicted deformation has been experimentally verified by measuring the profile of a test die using displacement transducers and die impressions. It is shown that there is good agreement between the predicted and experimental results for different operating conditions. By machining the amounts suggested by the model, the test die was run without flash at operating conditions that had previously resulted in flash.
A new isothermal theory for Stirling machine analysis and a volume optimization using the concept of ‘ancillary’ and ‘tidal’ domains
Authors: Finkelstein T
Published: October 2002

Theoretical studies of Stirling cycle machines have always utilized a topological system view that goes back to Schmidt's isothermal analysis, where the process is analysed by reference to the expansion space volume variations. Due to this idiosyncrasy in the formulation, it has been difficult to deduce meaningful design criteria from the results. In this paper an alternative visualization is presented, using the newly introduced concepts of a ‘tidal phase angle’ and overlapping ‘tidal’ and ‘ancillary’ domains. With vectorial parameters and a centralized reference basis, a non-dimensional parameter Rcaronfr;tcr, the ‘tidal compression ratio’, equal to the ratio of the average masses in the tidal and ancillary domains, is derived. This number uniquely characterizes the operation of equivalent machines and is therefore akin to the compression ratio in internal combustion engines. On the basis of this, a second new parametric grouping emerged to enhance the usefulness of the resultant integrated equations for use with dimensional analysis. It was defined as the ‘specific performance’ Rcaronfr;sp and is proportional to the output per unit mass, the gas constant and the operating temperature range. It is applicable to engines, heat pumps and refrigerators.

Prior attempts at optimizing the proportions of a Stirling engine have not yielded usable results and consequently nearly all Stirling cycle machines built up to the present time have expansion and compression spaces of equal size. The new analysis shows that this is not the most appropriate configuration and it readily yields an optimization of the component volumes. One single analytical conditional equation for the optimum relative sizes of the constituent spaces was obtained from the new formulation for performance that quantifies the condition for an optimized proportioning of any Stirling cycle machine. It has three distinct usable solutions, one of which is an analytical confirmation of a postulate that has previously been published by the author without proof, equating VE/ VC and also Vh/ Vk to the temperature ratio TE/ TC.

A numerical verification of this rule based on the proportions of the United Stirling V-160 engine compares it with 12 equivalent re-proportioned derivative engines, all with equal charge masses and operating at precisely the same conditions. This shows a substantial increase in the ideal performance through the use of the derived criteria. The main conclusion is that this theory may lead to a re-examination of the overall layout of Stirling cycle machines and the emergence of a new class of machines with superior performance.
Encoder error analysis in gear transmission error measurement
Authors: Du S , Randall R B
Published: October 2002

This paper investigates encoder measurement error and introduces a method of reducing or cancelling the encoder error from gear transmission error signals. The time domain and frequency domain analysis of the combined encoder error signals has been carried out to show the validity of the method. This method could be useful where the error of lower cost encoders is larger and undocumented and where there is limited space and only a smaller and less accurate encoder will fit.
Experimental and finite element studies of the running of V-ribbed belts in pulley grooves
Authors: Yu D , Childs T H C , Dalgarno K W
Published: October 2002

A finite element model of a complete loop of V-ribbed belt running between two torque transmitting pulleys has been created to study the mechanics of contact between a belt rib and pulley groove. It has been validated against experimental measurements of radial movement of a K-section belt running on 80 mm diameter pulleys. Patterns of sticking and slip between the belt and pulley are predicted. Of particular interest are the patterns of traction in entry and exit regions and, in fully seated regions, the variations with distance from the cord line. Both steady state and transient behaviours are modelled. Successful computations have only been achieved after developing a simplified description of the belt rubber's incompressible hyperelasticity, based on subsidiary experimental and finite element testing. Of major interest is the severe contact conditions predicted on driving pulleys compared to driven pulleys at the same loading.
The twin helical screw compressor Part 2: A mathematical model of the working process
Authors: Fleming J S , Tang Y , Cook G
Published: October 2002

Part 1 of this paper describes the physical characteristics, applications and analytical procedures currently relevant to the twin helical screw compressor. Part 2, presented here, describes a mathematical model of the working process of the machine. Use is made of a geometric model developed by Tang [2] which describes all the essential features as functions of the male rotor angle of rotation. The following effects are taken into account: internal leakage through six paths, gas—oil heat transfer, injected liquid refrigerant flashing in the compression cavity, dissolved refrigerant flashing from the oil injected into the compression cavity, dissolved refrigerant flashing in the end casings from oil supplied to the bearings and the draining of flashed refrigerant gas from the end casings to the low-pressure regions of the main casing. Internal friction at the principal rubbing surfaces is taken to cause heating of the oil and is modelled by making use of extensive measured data and manufacturers’ information. The hotter oil influences the compression process via a changed gas—oil heat transfer rate. The gas-oil heat transfer coefficient and the internal leakage coefficients are determined from measured data for mid-range conditions and applied over a range of conditions. The model output is compared with measured data; its current accuracy and possible improvement are commented upon.
Size optimization of cam mechanisms with translating roller followers
Authors: Yu Q , Lee H P
Published: October 2002

The problem of size optimization of a cam mechanism with a translating roller follower is analysed in this paper using non-linear programming techniques and a family of parametric polynomials for describing the motion curve. The present method can include many factors, such as the kinematic features, including the acceleration, the velocity, the boundary conditions and the symmetry of the motion curve, the curvature of the cam profile and the amount of offset of the follower, in the process of optimization and can provide many choices for meeting various design requirements. Examples are presented to illustrate the proposed design method.
Fretting fatigue conditions for two types of turboalternator rotor
Authors: Belloni G , Gorla C , Lo Conte A , Miccoli S
Published: October 2002

By means of a finite element model, the mating conditions between the end thread, located on the body of a shaft, and the thread of a ring, which supports the stud bolt that connects the internal and external conductors of a turboalternator in use at the ENEL (the Italian State Energy Corporation), are simulated. The contact pressures are calculated between the threads and their relative displacement, taking friction also into account, and conditions are identified that are characteristic of the phenomenon of fretting fatigue. Some considerations on the local risk situation allow the conclusion to be made that, in all probability, the structure is not in danger, even if the safety margin cannot be assessed precisely enough. The same analysis has been carried out for Darlington-type turboalternators that, as is known from the literature, have fractured. The two situations are compared and the safety coefficients for both types of rotor are deemed to be reliable.
Power transmission system modelling
Authors: Bartlett H , Whalley R
Published: October 2002

This paper employs hybrid modelling techniques in the investigation of the dynamic performance of ‘long’ driveshafts, which include a clutch and load, for power transmission purposes. The power transmission system considered is suitable for a wide variety of applications in which the load is coupled directly to the clutch and hence to the ‘long’ driveshaft. Owing to the length of the shaft and relatively pointwise location of the clutch and load, a distributed—lumped (D—L) description of the arrangement is investigated. This enables the behaviour of the dispersed driveline shaft to be ‘adequately’ replicated along with the connecting elements. A discrete modelling approach is adopted and analysis and simulated response characteristics are presented, thereby validating the technique. Existing results on clutch judder are referred to and the interaction between judder and the driveshaft torsional oscillation is commented upon.
Temperature stresses in thick circular cylindrical shells used in nuclear reactors with exponential heat generation within the shell wall thickness
Authors: Guerreri G , Cossa L M
Published: October 2002

In the preceding paper, formulae and graphs were given which enabled estimates to be made of heat flow, temperature and stresses through the thickness of the circular cylindrical shell, when heat was not generated inside the thickness and when it was generated according to a uniform path. Situations of heat generation in shell thickness are commonly encountered in the shields of nuclear reactors. All the expressions given for stress in the preceding paper may be reduced to the following form: σ{ Eα qa2/[(1 - ν) k]}η, where η is a factor associated with the stress which depends upon heat generation profiles, internal and external temperatures T a and T b of the shell and its thermal conductivity k, for each radius r.

Another common heat generation which occurs in these shells has an exponential path. For these cases, the circumferential thermal stress σϑ may be given in the following form: σϑ = { Eα q(β−1)2/[(1 - ν) k]}ηϑ, where β is the exponential absorption factor which is related to the quantitative measure of the generated heat and ηϑ is the non-dimensional circumferential stress. In the present paper graphs are furnished to estimate the parameter ηϑ in order to foresee the values of stresses in the circumferential directions at the internal and external radii of the shell for the case of exponential heat generation through the wall thickness. They apply only when: (a) all generated heat flows inside the vessel or (b) all heat flows outside the vessel or ( c) T a = T b.

Application of the principle of superposition shows how to evaluate the stresses where the generated heat paths are not uniform, triangular or exponential.
Synthesis of the internal parallel cam mechanism
Authors: Nishioka M , Nishimura T
Published: October 2002

Parallel cam mechanisms have been studied in different ways. In this paper, a parametric formulation which can cover every configuration of the parallel cam mechanism is derived. As a result of parametric analysis, a new, last mechanism was found. This cam is essentially an internal cam mechanism. Based on the assumption of an equally distributed roller follower, the basic configurations of the mechanism are derived from both the pressure angle and the undercutting constraints. As a result, the possible number of rollers per spider plate is two. Thus the feasible area of the design parameters of the mechanisms are obtained. The advantages of the mechanism over the conventional parallel mechanism are the saving of space and a larger angular stroke of output.
On the shaft locations of two contra-rotating counterweights for balancing spatial mechanisms
Authors: Chiou S-T , Tzou J-C
Published: October 2002

It has been shown in a previous work that a frequency term of the shaking force of spatial mechanisms, whose hodograph is proved to be an ellipse, can be eliminated by a pair of contrarotating counterweights. In this work, it is found that the relevant frequency term of the shaking moment is minimized if the balancing shafts are coaxial at the centre of a family of ellipsoids, called isomomental ellipsoids, with respect to (w.r.t.) any point on an ellipsoid, as is also the root mean square (r.m.s.) of the relevant frequency term of the shaking moment. It can also be minimized even though the location of either shaft, but not both, is chosen arbitrarily on a plane. The location of the second shaft is then determinate. In order to locate the centre, a derivation for the theory of isomomental ellipsoids of a frequency term of the shaking moment of spatial mechanisms is given. It is shown that the r.m.s. of a frequency term shaking moment of a spatial mechanism w.r.t. the concentric centre of the isomomental ellipsoids is the minimum. Examples of a seven-link 7-R spatial linkage and a spatial slider-crank mechanism are included.
Turbocharger aerodynamic design
Authors: Flaxington D , Swain E
Published: October 2002

The aerodynamic design of turbochargers is described, covering radial compressors and turbines and also axial turbines. The paper concentrates upon those aspects that are peculiar to turbocharger design, including the approach adopted, and highlights the importance of company-specific empirical data. Turbochargers have to be physically adaptable to suit many different sizes of engine, with a great variety of operating duties. The need for turbochargers to achieve the highest obtainable performance at the lowest cost while maintaining durability levels comparable with the engine contributes to the design challenges that are discussed.
Impact of three-dimensional phenomena on the design of rotodynamic pumps
Authors: Gülich J. F.
Published: October 2002

Three-dimensional Navier—Stokes calculations are expected to be increasingly applied in the future for performance improvement of rotodynamic pumps. Frequently such an optimization process involves a preliminary design—based on one-dimensional methods and empirical data—which is subsequently optimized by computational fluid dynamics (CFD). Employing an empirical database is not only necessary in order to provide a good starting point for the CFD analysis but also to ensure that the design has a good chance of fulfilling part load requirements, since recirculating flows at the impeller inlet and outlet are not easily handled by CFD programs. CFD calculations provide the specific work input to the fluid and information on losses and reveal the complex three-dimensional flow patterns. The designer is faced with the task of interpreting such data and drawing conclusions for the optimization of the impeller. It is the purpose of the present contribution to analyse and describe the impact of various geometric parameters and flow features on the velocity distribution in the impeller and their influence on performance and part load characteristics. Criteria are also provided to select the parameters for the preliminary design. Hydraulic impeller losses calculated by CFD programs may often be misleading if the non-uniformity of the flow distribution at the impeller outlet is ignored. Procedures to quantify such mixing losses in the diffuser or volute downstream of the impeller are discussed.
Design of low-reaction steam turbine blades
Authors: Walker P. J. , Hesketh J. A.
Published: October 2002

Optimizing the aerodynamic design of turbine blades is a compromise between a large number of issues. These can be grouped into three areas:

(a) aerodynamic compromises; e.g. increasing the pitch—chord ratio improves profile loss but worsens secondary loss,

(b) mechanical constraints; e.g. the pitch-chord ratio affects the strength of a profile, which for a given unsteady stress level determines the width and hence strongly influences the secondary loss,

(c) costs; e.g. increasing the number of stages improves performance but also increases the cost of the turbine. It can also affect rotor stability and even the size of the turbine hall.

Some of the issues are difficult to quantify and may vary from day to day. For example, the marginal manufacturing cost of a given design will depend on the load on particular machine tools. Therefore the approach of a manufacturer evolves from experience. However, many other issues can be addressed systematically to achieve near optimum designs. This paper explores the aerodynamic design of low-reaction steam turbine blades and describes the technical arguments that lead to design decisions. Where the decision depends on cost and mechanical constraints these are also explored. A typical low-reaction stage is shown schematically in Fig. 1. The paper will concentrate on the design of short and intermediate height blades typically used in HP and IP cylinders and in the early stages of LP cylinders. In practice, long blades typically used in the later stages of LP cylinders are fairly similar for both ‘reaction’ and ‘impulse’ design manufacturers.
Gear transmission error outside the normal path of contact due to corner and top contact
Authors: Munro R. G. , Morrish L , Palmer D
Published: October 2002

This paper is devoted to a phenomenon known as corner contact, or contact outside the normal path of contact, which can occur in spur and helical gear transmission systems under certain conditions. In this case, a change in position of the driven gear with respect to its theoretical position takes place, thus inducing a transmission error referred to here as the transmission error outside the normal path of contact (TEo.p.c).

The paper deals with spur gears only, but the results are directly applicable to helical gears. It systematizes previous knowledge on this subject, suggests some further developments of the theory and introduces the novel phenomenon of top contact. The theoretical results are compared with experimental measurements using a single flank tester and a back-to-back dynamic test rig for spur and helical gears, and they are in good agreement.

Convenient approximate equations for calculation of TEo.p.c suggested here are important for analysis of experimental data collected in the form of Harris maps. This will make possible the calculation of tooth stiffness values needed for use in theoretical models for spur and helical gear transmission systems.
Design considerations for the volutes of centrifugal fans and compressors
Authors: Pan D , Whitfield A , Wilson M
Published: October 2002

The initial conceptual design of centrifugal fan and compressor volutes is considered and extended to accommodate overhung volute designs often used in process and turbocharger compressors. The initial passage design is then developed through the application of a commercial computational fluid dynamics (CFD) code.’ Based on the experimental data of a turbocharger compressor volute, three-dimensional, compressible, steady flow computations were carried out for alternative volute designs. Detailed internal flow data in both a conventional and a modified volute design, at both design and off-design flow conditions, are presented. The design investigation showed that enlarging the flow passage area near the tongue region, but without changing the exit-inlet area ratio of the volute, led to an improvement in the internal flow distribution at off-design flow conditions.
A parallel parking system for a car-like robot with sensor guidance
Authors: Jiang K , Zhang D Z , Seneviratne L D
Published: October 2002

An automated parallel parking strategy for a car-like mobile robot is presented. The study considers general cases of parallel parking for a rectangular robot within a rectangular space. The system works in three phases. In scanning phase the parking environment is detected by ultrasonic sensors mounted on the robot and a parking position and manoeuvring path is produced if the space is sufficient. Then in the positioning phase the robot reverses to the edge of the parking space, avoiding potential collisions. Finally, in manoeuvring phase the robot moves to the parking position in the parking space in a unified pattern, which may require backward and forward manoeuvres depending on the dimensions of the parking space. Motion characteristics of this kind of robot are modelled, taking into account the non-holonomic constraints acting on the car-like robot. On the basis of the characteristics, a collision-free path is planned in reference to the surroundings. The strategy has been integrated into an automated parking system and implemented in a modified B12 mobile robot capable of safe parking in tight situations. The system is developed for an automated parking device to help vehicle drivers. It also shows the potential to be integrated into automobiles.
Axial flow compressor design†
Authors: Gallimore S. J.
Published: October 2002

The purpose of this paper is to set out some of the basic principles and rules associated with the design of axial flow compressors, principally for aero-engines, as well as the practical constraints that are inevitably present. The thrust is primarily on the aerodynamic design but this cannot be divorced from the mechanical aspects and so some of these are touched upon but are not gone into so deeply. The paper has been written from the point of view of the designer and tries to cover most of the points that need to be considered in order to produce a successful compressor. The emphasis has been on the theory behind the design process and on minimizing the reliance on empirical rules. However, because of the complexity of the flow, some empiricism still remains.
Three-dimensional kinetic theory approach for laser pulse heating
Authors: Yilbas B. S. , Sami M
Published: October 2002

Lasers are widely used as a machine tool in the metal industry. One of the important areas of laser application is surface treatment of engineering metals. To improve the process parameters in the laser heating process, an exploration of the heating mechanism is fruitful. The present study is carried out to develop a three-dimensional model for a laser pulsed heating process using the electron kinetic theory approach. The heating model introduced relies on successive electronphonon collisions; therefore, it is this process that describes the heat conduction mechanism. This study is limited to heat conduction only. Consequently, the phase change process is not taken into account. To validate the theoretical predictions, an experiment is conducted to measure the surface temperature using an optical method. Moreover, a one-dimensional heating model developed previously is also considered and the predictions of three- and one-dimensional heating models as well as experimental results are compared. It is found that the three-dimensional model gives lower surface temperatures compared with the one-dimensional model considered. However, experimental results agree well with the results obtained from the three-dimensional model. In addition, an equilibrium time is introduced. In that case, energy gain of electrons via incident beam absorption balances the energy losses due to conduction through successive electron-phonon collisions.
Non-reversible dry friction oscillator: Design and measurements
Authors: Wiercigroch M , Sin V. W. T. , Liew Z. F. K.
Published: October 2002

A Coulomb oscillator with a variable normal force has been designed and manufactured to carry out a wide range of experimental dynamic analysis, especially the study of the non-reversibility of dry friction characteristics. The design choice was based on the criteria of accuracy of the mathematical model and flexibility in terms of parameter changes such as the natural frequency of the system, coefficient of friction and normal force. The system consists of a block mass attached to two coil springs and a dry frictional damper in which the friction force is varied by a pneumatic actuator. This allows a constant pressure between sliding surfaces to be maintained. The experimental set-up, the calibration procedure for the clamping device and typical results are presented. Experimental non-reversible dry friction characteristics are discussed.
Technical Note: Rolling dynamic stiffness and damping characteristics of small-sized pneumatic tyres
Authors: Saran V. H. , Goel V. K.
Published: October 2002

In this paper, a laboratory technique for determination of rolling dynamic stiffness and damping coefficients of small-sized, bias-ply tyres has been discussed. The effect of normal load, inflation pressure and speed on four different tyres has been reported. The results show similar trends to those reported by other investigators.
Technical Note: Combustion characteristics and hydrocarbon emissions of a spark ignition engine fuelled with gasoline-oxygenate blends
Authors: Huang Z , Miao H , Zhou L , Jiang D
Published: October 2002

Combustion characteristics and hydrocarbon emissions in a spark ignition engine operating on oxygenated fuel blends are studied, and the mass fraction burned and engine hydrocarbon emissions are analysed. Calculation results, based on the recorded pressure diagram, show that the flame development and rapid burn angles of gasoline-ether blends generally decrease and the maximum cylinder pressure increases as compared with those of gasoline. The flame development angle and rapid burn angle decrease when the fraction of alcohol fuels in gasoline is small, whereas they increase when the fraction of alcohol fuels is large. The experimental results show that engine exhaust hydrocarbon emissions can be reduced by blending oxygenated fuels in gasoline rather than operating on neat gasoline. Operating on gasoline-ether blends rather than on gasoline-alcohol fuel blends and neat gasoline greatly reduces hydrocarbon emissions.
The automotive connector: The influence of powering and lubricating a fretting contact interface
Authors: Swingler J
Published: October 2002

The increasing amount of telematic and other electronic systems in the modern motor vehicle demands higher performance and reliability in ever decreasing space. Over many years, connector technology has advanced but is still regarded as the weak link in the reliability chain. Fretting corrosion is thought to be the main failure mechanism causing intermittent high contact resistance.

A low-frequency fretting apparatus is used in this study to induce fretting corrosion on contact samples. Low frequency is used to simulate the effect caused by different thermal expansion of connector components. Powering the contact interface under these fretting conditions delays the onset of high contact resistance. Joule heating is expected to accelerate surface oxidation, but electrical breakdown of films dominated at the levels studied (2 A, 12 V open circuit). Lubricating the interface also improves performance which is shown to be due to at least three contact enhancement mechanisms: wear reduction, oxidation retardation and improved debris dispersal.
The UK road user charging technology trials: A review
Authors: Stoneman B
Published: October 2002

The department of the Environment, Transport and the Regions (DETR) has embarked on a programme of research into road user charging. The first phase of the programme took place at the research track facility of the Transport Research Laboratory (TRL) between November 1996 and June 1997. Technology trials were undertaken with two electronic fee collection (EFC) systems supplied by Bosch Telecom Gmbh and GEC-Marconi Communications. The trials investigated the ‘front end’ of tolling systems, namely the tolling transaction, violator detection and vehicle classification components.

This paper describes the trials design and the preparation of an infrastructure at the test track suitable for trials of both motorway and urban road charging systems. A dedicated trials support system was configured and comprised a trials computer system a video monitoring system, a vehicle location system and an environmental monitoring station. Trials scripts were developed for a range of trials scenarios and used as the basis for testing the EFC systems with a range of vehicle manoeuvres, including manoeuvres not possible on a live motorway. The trial programme provided the opportunity to investigate the technologies and the potential of EFC systems for application on the UK motorway network. In parallel with the test track trials programme, a separate and wide-ranging programme researched specific tolling-related issues which were reported to the DETR to provide additional information on the tolling technologies and to support policy development. The next phase of the UK charging programme is also discussed following the Government's White Paper on the future of transport.
A novel approach to optimizing and stabilizing interior noise quality in vehicles
Authors: Cornish R
Published: October 2002

Interior noise quality, as defined by the relative amounts of noise components and time-based metrics, is known to depend critically on structural noise paths. Manufactured vehicles are found in reality to have very variable structural noise paths and hence interior noise quality. This paper describes a new experimental and theoretical methodology to improve quality consistently by taking full account of manufacturing realities at an early stage. A case study is described involving a light commercial vehicle to illustrate the approach. The approach requires the availability of noise path measurement of a body shell similar to the vehicle under development.
Spur bevel gear differentials: Designing involute tooth numbers for the pinion and side gear
Authors: Vantsevich V. V.
Published: October 2002

It has been theoretically proven that both friction in two mating gears and the drawing of mating involute tooth profiles along the pressure line (the line of action) generate oscillation of axial force components of the resultant force acting in a single pair of mating spur bevel gears. The law of summing the axial force components acting on the side gear from all the differential satellites (pinions), as well as on the pinion from the two side gears, depends on combinations of numbers of teeth on the side gear and pinion. A classification of bevel gear differentials into four groups depending on these combinations has been carried out in the present work. A designer should ensure that a differential under development be in accordance with group III to decrease oscillation of the total axial forces acting inside the mechanism itself. Testing has corroborated the theoretical solutions.
Automotive box section design under torsion: Part 1: Finite element modelling strategy
Authors: Lee M. M. K. , Pine T , Jones T. B.
Published: October 2002

Behaviour under torsion is an important performance-related property of automotive box sections. A previous experimental study has identified joining technique, section thickness and section area as the major influencing factors on the torsional behaviour of box hat sections. Using these test results as the basis, a finite element modelling strategy that can simulate the behaviour of adhesively bonded and spot-welded automotive box sections subjected to torsion is presented. The numerical study investigated the effects of material representation, mesh density and layout, and joining technique representation on the stiffness, elastic limit and ultimate strength of the box sections. The final model, calibrated and validated against test results obtained from previous work, was used in an extensive study, presented in the companion paper (Part 2), to further the understanding of the behaviour of torsionally loaded box sections and its implications on weight reduction of automotive structures.