bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analytical formulae for the design of a railway vehicle suspension system
Authors: Mastinu G R M , Gobbi M , Pace G D 
Published: October 2002

A simple two-degree-of-freedom (2DOF) model is used to derive a number of analytical formulae describing the dynamic response of railway vehicles to random excitations generated by vertical track irregularities. The dynamic response is given in terms of standard deviations of a number of relevant performance indices such as body-bogie suspension stroke and body acceleration. The derived analytical formulae can be used either during preliminary design or for other special purposes, especially when approximated results are acceptable. An estimation of the degree of approximation offered by analytical formulae is attempted and the results seem satisfactory. By inspection of the analytical formulae a parameter sensitivity analysis may be readily performed. In the second part of the paper, an optimization method for the improvement of the dynamic behaviour of railway vehicles is introduced. The method, based on multiobjective programming (MOP), is a general one and can be exploited for many engineering purposes. In the paper the method has been applied with the aim of achieving the desired trade-off among conflicting performances such as standard deviation of the body acceleration versus standard deviation of the secondary suspension stroke. As a result, new analytical formulae defining the settings of some relevant vehicle suspension parameters have been derived.
Control of diffusing flow at low Reynolds numbers with annular wall jets
Authors: Burgess C P , Lawn C J 
Published: October 2002

During the course of experiments to determine the influence of coflowing streams of air on the lift-off height of a methane jet flame, it was necessary to achieve a smooth axial decay of the velocity field in a conical diffuser. It was also crucial that the mean axial velocity profile was flat in the central region of the flow. These criteria proved to be quite difficult to meet, even with diffuser half-angles limited to 12.6°, partly because of the low Reynolds numbers involved, which were in the range 780-3500 based on the inlet pipe diameter. A satisfactory solution, following Duggins, proved to be the injection of high-velocity air along the wall from a narrow annulus around the inlet. For diffusers with half-angles of 3.5, 7.5 and 12.6°, the optimum rates of injection were found to be independent of the half-angle but dependent on the Reynolds number and on whether a gauze mesh was present at the inlet. The efficiency of diffusion reached an optimum value of 60 per cent at the highest Reynolds numbers, and this was achieved both with and without the mesh.
An application of thermal exermal analysis to the development of mine cooling systems
Authors: Twort C T , Lowndes I S , Pickering S J 
Published: October 2002

The extraction of minerals and coal at greater depth, employing higher-powered machinery to improve production levels, imposes an increased burden on the ability of a ventilation system to maintain an acceptable mine climate. Hence, mechanical mine cooling systems are often adopted, which can be expensive both in terms of their associated capital and operating costs. Consequently, in order to optimize the costs it is essential to provide the mine operator with a method with which to determine the most cost effective and efficient mine cooling system. The following paper overviews the development of a novel approach to the energy analysis of mine cooling systems using the concepts of thermal exergy analysis. Generic model mine ventilation networks are constructed and the subsurface environments of these mine networks predicted. Models of various cooling system methods are developed and applied to control the underground climate within these mine networks to within pre-set climatic limits. The exergy transfers that are produced by the application of the different cooling methods are compared using performance indices. Models to represent chilled water distribution networks, used to supply the air coolers within the various cooling systems, are designed and balanced. The results of the exergy analyses applied to the operation of the various chilled water pipe networks are discussed and used to assess the exergetic performance of the application of each cooling system to the mine ventilation network.
Surface behaviour testing of phosphate—stearate coated steel parts
Authors: Dubois A , Oudin J , Rigaut J M 
Published: October 2002

Two recently developed tests are used in this work in order to simulate contact and friction conditions in metal working processes. The upsetting—sliding test and the indentation—rotation test are able to measure the frictional properties induced by various lubricants or steel surface treatments during the actual forming operation. In this paper, the interest is focused on friction measurement and seizure performance of steel phosphate coatings strengthened by localized high contact pressures. In the upsetting—sliding test, the indenter slides along the workpiece surface with a given penetration. Depending on the penetration and on the indenter geometry, a more or less strengthened plastic zone appears in the contact surface vicinity. Indenter normal load and tangential force values are related to mean contact pressure and mean friction stress at the contact surface. The experimental surface behaviour is then identified using friction stress—contact pressure curves. In the indentation—rotation test, the workpiece rotates while in contact with a fixed semi-cylindrical slider. Curves of friction force versus workpiece revolutions are related to an increase in coating damage and to seizure. The sensitivity of the upsetting—sliding test is illustrated by friction stress—contact pressure curves obtained for different phosphate—stearate coatings, indenter velocities and workpiece initial roughness. Phosphate—stearate coating performance until seizure is finally obtained from the indentation—rotation test and results from both tests are compared and discussed.
The influence of rounded edges on indentation by a flat punch
Authors: Ciavarella M , Hills D A , Monno G 
Published: October 2002

The contact problem and stress state for indentation by a flat punch with rounded edges is studied. For the contact problem itself analytical solutions are obtained for both surface pressure and interior stress fields. Cases of normal indentation and frictional contact, the latter in both sliding or partial slip conditions, are all treated. The transition from the Hertzian configuration to the contact between a nominally flat pad and contacting flat surface is discussed, and it is found that the strength of the contact decays surprisingly slowly. Regarding the von Mises yield parameter, there is a range of configurations for which the strength is actually higher than the Hertzian one, and the strength decays only when the corner radii are very small. The present solution is therefore a realistic alternative to the classical rigid-flat punch idealization, and has particular application to fretting fatigue tests.
A feature complexity index
Authors: Little G , Tuttle R , Clark D E R , Corney J 
Published: October 2002

An index is presented for quantifying the geometric complexity of a three-dimensional solid model. This provides a measure by which components may be compared one with another in relation to their relative complexity. The index is alphanumeric and readily computable. Such an index can be of use in the field of feature recognition as a means to determine how efficiently one algorithm handles components of varying complexity compared to another such algorithm. The performance of the authors’ own feature recognition algorithm is tested against components of differing complexity as determined by the index.
The effect of swirl on the annular flow past an axisymmetric poppet valve
Authors: Nadarajah S , Balabani S , Tindal M J , Yianneskis M 
Published: October 2002

This paper describes an experimental investigation of the swirling flow through an axisymmetric port and poppet valve assembly under steady flow conditions. This work is an extension of the preceding paper, which is a study of the non-swirling flow in the same flow configuration [1]. Three different swirl rates were investigated with the aim to study the effects of swirl on the mean flow and turbulence characteristics of the flow field. The flow structure was studied by means of laser sheet flow visualization and the three velocity components and the associated Reynolds stresses were measured by ensemble-averaged laser Doppler anemometry techniques. The results are compared with those obtained with the non-swirling flow. The addition of the swirl was found to alter the flow structure, particularly below the valve where a new counter-rotating vortex is formed. A toroidal recirculation zone is also formed in the valve passage. The growth and entrainment of the jet emanating from the valve gap increase and its trajectory angle changes. The flow visualization studies showed evidence of precession of the swirl centre and jet flapping. Swirl increases the Reynolds stresses and the turbulence production rate in most regions of the flow.
A full numerical analysis of hydrodynamic lubrication in artificial hip joint replacements constructed from hard materials
Authors: Jin Z. M. , Dowson D 
Published: October 2002

A full numerical analysis of the hydrodynamic lubrication problem of artificial hip joint replacements with surfaces of high elastic modulus materials, such as metal-on-metal or ceramic-on-ceramic, under cyclic walking conditions is reported in this paper. The Reynolds equation in spherical coordinates has been solved for both entraining and combined entraining and squeeze film motions under a three-dimensional variation in both the load and the speed experienced in hip joints during walking. It has been shown that a finite lubricating film thickness can be developed during the walking cycle owing to the combined action of the squeeze film and entraining motions under some conditions. It has been found that the design parameters for plain spherical bearings, such as the femoral head radius and the radial clearance between the femoral head and the acetabular cup, have a large effect on the magnitude of the predicted lubricating film thickness. Some interest has been shown in recent years in the performance of metal-on-metal bearings in which a dimple has been machined at the pole of the acetabular cup. It is shown that a dimple on the acetabular cup can significantly increase the film thickness throughout the walking cycle, particularly for relatively large depths and if the location of the dimple coincides with the direction of the resultant force acting on the joints. It is concluded that there is a good possibility that a full continuous hydrodynamic lubricating film can be developed in ceramic-on-ceramic hip joint replacements, and perhaps for some well-finished metal-on-metal implants with a relatively small radial clearance. For some metal-on-metal configurations, the effect of elastic deformation of the bearing surfaces must be taken into account in the lubrication analysis, particularly for a relatively large radial clearance.
Dynamic analysis of rotationally flexible cam mechanisms
Authors: Balkwill J D G , Morrey D 
Published: October 2002

A novel mechanism for the actuation of valves in an internal combustion (IC) engine is described. Previous publications are reviewed and it is shown that the mechanism has received very little attention, in particular no dynamic analysis of it has been published. The mechanism features a shaft driving a cam through a coupling of sufficient rotational flexibility to permit significant angular offsets to develop during the cycle. A differential equation of motion of a simplified system is derived and solved using two methods. The theory requires a knowledge of twelve fundamental system dynamic parameters from which a prediction of angular offset of the camlobe throughout the cycle is produced. A dataset was obtained from a purpose built apparatus which recorded the angular offset of the camlobe with respect to the camshaft for a range of rotational speed values. Results graphs are presented and the level of agreement between theory and experiment is discussed. The work demonstrates for the first time that useful predictions of simplified mechanism performance can be obtained from the model developed. Recommendations for further work in this area are made.
A study of exhaust noise in a motor vehicle using statistical energy analysis
Authors: Steel J. A. , Fraser G , Sendall P 
Published: October 2002

This work uses statistical energy analysis (SEA) to study noise transmission through a commercial motor vehicle and in order to do this various sound and vibration power inputs associated with flanking transmission via the exhaust and engine noise are calculated. A modern commercial motor vehicle that has an exhaust noise sensitivity problem is studied in this work. The aim of this work is to demonstrate the application of SEA and to study the effects on noise transmission when the exhaust is incorrectly fitted (misaligned). Airborne and structural paths for sound and vibration transmission to a vehicle saloon are considered. Also, the SEA framework is used to identify the relative importance of each structural and airborne power input in relation to the sound power that is transmitted to the vehicle saloon. It is shown that the importance of each sound power input varies with frequency. At low frequencies, sound transmission through the vehicle structure is most important. At high frequencies, airborne flanking noise transmission to the floor is important. In this case, exhaust vibration transmission is most important at frequencies between 250 Hz and 1 kHz when the engine is running at 5700 r/min, and the SEA model predicts the change in performance associated with exhaust misalignment.
Recent advances in antilock braking systems and traction control systems
Authors: Austin L , Morrey D 
Published: October 2002

Antilock braking systems (ABS) are closed-loop devices designed to prevent locking and skidding during braking. Traction control systems (TCS) limit the amount of traction force generated at the wheels to prevent loss of traction. Both systems contain an electronic control unit (ECU), which compares signals from each wheel sensor. In ABS systems, the pressure to one or more of the wheels is regulated, whereas in TCS systems, the drive torque to the wheels is reduced. Recent advances include the use of wireless accelerometers, developments in the control software that take into account the dynamics of the tyres and suspension, the estimation of parameters such as lateral acceleration and wheel slip and the use of adaptive control and fuzzy logic. More recently, these systems have been integrated into other vehicle systems, such as four-wheel steering and active suspension. Future improvements might include the use of smart materials for sensor development, and the use of roadside-to-vehicle control.
The dimensional quality of sheet metal assembly with welding-induced internal stress
Authors: Shiu B. W. , Shi J , Tse K. H. 
Published: October 2002

The present paper is the first to propose a minimum stress criterion for the minimum dimensional variation during sheet metal assembly. The weld sequence affects the dimensional variation owing to the welding process. A case study illustrates the minimum stress criterion on dimensional variation. This paper proposes a generic design criterion for sheet metal products and processes that would produce minimal stress-induced dimensional variation for spot-welded sheet metal assemblies. The process design proposes a minimum strees build-up by using the ‘sheet metal ironing welding technique’ in the weld sequencing design. The product design proposes a minimum stress build-up design criterion to manage the accumulation of stress. The proposed product and process design methods enable automotive body design engineers to create a quality product with minimum dimensional variation caused by the manufacturing stress within the body-in-white structure. Moreover, this facilitates the industry's objective of building a high quality automotive body with minimum stress. This is an important factor in contributing to the superior quality of the body panel fits. It also helps to reduce the quality-related warranty costs. This paper primarily focuses on the development of a joint design guideline by exploring the relationship between the dimensional variation and the stress build-up. First, the automotive assembly process design will be introduced. A simple analysis of a one-dimensional assembly is produced. A three-dimensional structural analysis of a box assembly is investigated for the effect of stress build-up within a structure on the dimensional instability or variation. Then a three-dimensional finite element analysis of an assembly with weld sequencing of two imaginary parts is produced. An experimental industrial trial has confirmed the validity of the simulation methodology. Then a welding sequence design guideline is produced based on the previous simulation result, followed by a joint design guideline to help improve the design of dimensionally robust design.
Prediction of knock onset and the autoignition site in spark-ignition engines
Authors: Lee Y , Pae S , Min K , Kim E. S. 
Published: October 2002

A three-dimensional model of knock is developed to predict knock occurrence and the autoignition site in spark-ignition engines. A premixed turbulent combustion model, which falls within the flame area evolution category, and a flame wall quenching model are applied to simulate flame propagation. A reduced kinetic model is used to simulate autoignition in the unburned gas region. Engine experiments are performed to calibrate the reduced kinetic model and to verify the results of this modelling. A spark plug integrated pressure transducer and 11 ion probes are installed in the cylinder head to detect knock occurrences, flame arrival angles and autoignition sites. The model predictions show good agreement with the cylinder pressures, flame arrival angles, knock occurrences and autoignition site of the engine experiments with the variations in spark timing.
A comparison of the relative effects of fuel composition and ignition energy on the early stages of combustion in a natural gas spark ignition engine using simulation
Authors: Yossefi D , Belmont M. R. , Ashcroft S. J. , Maskell S. J. 
Published: October 2002

Spark ignition engines operating on natural gas (NG) show advantages over petrol and diesel alternatives in terms of precatalyst emissions. However, such engines are affected much more than their petrol counterparts by the long combustion delay of the main fuel component, methane. The sensitivity of combustion delay to fuel/diluent chemistry means that this issue is exaggerated by the presence in the NG of variable concentrations of higher hydrocarbons and of inorganic components, arising from the worldwide variability of NG or from the use of exhaust gas recirculation. The present article reports on a study using a large-scale three-dimensional simulation, incorporating computational fluid dynamics (CFD) and fully detailed chemical kinetics, of the early stages of NG combustion in a spark ignition engine. The focus is on comparing the relative influences of gas composition (i.e. the ethane content of the NG, and carbon dioxide in the oxidant/diluent) with the effects of ignition source location and energy on the early progress of the combustion. The results of the studies show that, although the presence of ethane enhances the combustion propagation rate and reduces delay time, and carbon dioxide has the reverse effect, the influences of the characteristics (energy and location) of the ignition source dominate over quite large changes in mixture composition. These findings have practical ramifications for the development of strategies for reducing combustion delay time in NG-fuelled engines.
Importance of inter-ring crevice volume as a source of unburned hydrocarbon emissions-numerical considerations
Authors: Kim C. G. , Bae C. S. , Choi S. M. 
Published: October 2002

The influence of the inter-ring crevice, the volume between the top and the second piston rings, on unburned hydrocarbon (UHC) emissions has been numerically investigated with the aid of experimental results. The main goal of this study was to estimate the level of UHC emissions induced by the blow-up of the unburned gas trapped in the inter-ring crevice (inter-ring mixture). For this purpose, the relationship between the inter-ring mixture and UHC emissions was established from the experimental results. A physical flow model integrated with a ring dynamics model was constructed to predict the gas flows through the inter-ring crevice. Calculated results showed that some of the inter-ring mixture returned to the combustion chamber, while the cylinder pressure fell below the inter-ring pressure late in the expansion stroke. The amount of inter-ring mixture returning to the combustion chamber after exhaust valve open was calculated and converted to the corresponding UHC emissions using the relationship between the inter-ring mixture and UHC emissions obtained from the experiments. The calculated level of UHC emissions caused by the inter-ring mixtures was 10-30 per cent of the entire UHC emissions over a range of speeds (1250—3500 r/min) and loads [185—556 kPa brake mean effective pressure (b.m.e.p.)]. The contribution was highest at the medium speed and medium load (2500 r/min and 432 kPa b.m.e.p.) for the test condition, which corresponds to the engine condition frequently required for normal running. These findings confirm the importance of inter-ring crevice volume in the UHC emissions in spark ignition engines.
Simulation of a transient torque response for engine performance in a spark ignition engine
Authors: Cho H. , Song H. , Lee J. , Kauh S. 
Published: October 2002

In the present study, a mean torque predictive model has been proposed and experimentally validated. It includes an inducted air mass model, a fuel delivery model and a mean torque production model. The inducted air mass model and fuel delivery model, considering the dynamic behaviours of air induction and fuel delivery, were proposed to predict the air-fuel ratio excursions under transient conditions. The mean torque production model reflects thermal efficiency, volumetric efficiency, friction and the effect of spark timing. In the spark timing model, knock limit and acceleration retardation are considered. Experiments were carried out to validate the simulation model for step changes of the throttle at constant engine speed. The results show reasonable agreements between simulation and experiment at fully warmed conditions. Using this model, fuelling strategies were varied with open fast throttle while air-fuel ratio excursion and indicated mean effective pressure were predicted.