bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gear Transmission Error Measurement Using Phase Demodulation
Authors: Sweeney P J , Randall R B 
Published: February 2007

Gear manufacturers in all fields of industry are under increasing pressure to deliver products of high accuracy and which generate ever lower levels of vibration and noise. Over the past decades, transmission error (TE) measurement has become more popular as a means of measurement for research and quality control. However, dedicated measurement systems have often proved incapable of measuring TE under operating conditions. This paper presents an overview of TE measurement techniques and their applications. In addition, an introduction to a versatile and portable method of measurement based on FFT analysis and demodulation is given. This method is easily implemented using current generation FFT analysers or signal analysis software, and is suitable for research, diagnostics, condition monitoring and quality control applications alike.
Polishing and Honing Processes: An Investigation of the Thermal Properties of Mixtures of Polyborosiloxane and Silicon Carbide Abrasive
Authors: Fletcher A J , Fioravanti A 
Published: February 2007

The passage of an ultrasonic wave through a mixture of polyborosiloxane and silicon carbide abrasive, when used in a honing process, causes heating due to the attenuation of the said wave. This is critical to the honing process since the temperature in the components being treated must be limited to about 70° C. A numerical model of the heat generation and transfer processes in the polishing medium is being formulated, which requires knowledge of the thermophysical properties of the mixture. This investigation concentrates on the experimental determination of thermal conductivity, specific heat capacity and surface heat transfer coefficient for various mixtures of polyborosiloxane and silicon carbide abrasive. Theoretical, semi-empirical and empirical models are derived for the variation of these thermal properties as functions of both material composition and temperature.
Measurements of Thermal Performance of the Regenerator of a Cryocooler with a high Number of Transfer Units Value
Authors: Chen P-H , Chang Z-C 
Published: February 2007

Hundreds of stacked wire screens are used in the regenerator matrix of a common cryocooler. The number of transfer units of such a matrix (denoted as NTUm) may well exceed 60. However, most of the earlier studies reported are limited to studies of regenerators with NTUm values less than 60, as the single-blow method was employed to measure the NTUm value of the regenerator matrix. Furthermore, in these earlier studies, the effect of heat transfer from the working fluid to the external tube and the Joule-Thomson effect were neglected. In the present study, three regenerators having high NTUm values have been constructed and a transient single-blow technique has been employed to measure the friction factor and the heat transfer performance of these regenerators. In addition, an improved model has been adopted to correct the shortcomings of the earlier studies. Empirical correlations have been provided for the relation between the friction factor and Reynolds number and between the Nusselt number and Reynolds number. The correlation with smaller NTUm values agreed well with those reported in earlier studies.
Dynamic Simulation of Road Vehicle Performance Under Transient Accelerating Conditions
Authors: Hong C-W 
Published: February 2007

A personal computer-based simulation package has been developed to design the powertrain system of passenger cars aiming to operate at optimal performance. This package is capable of dynamic simulation of road vehicle performance under transient accelerating conditions. Two methods are included: one is the traditional transient-reconstruction method using steady-state engine performance maps; the other is a dynamic simulation technique newly developed by the author. The latter is described in this paper. It is based on cyclic analysis of the engine thermofluid-combustion phenomena with additional considerations of flow inertia, thermal inertia and mechanical inertia effects. This transient engine model plus a dynamic powertrain model and a transient road-load simulation make it possible to predict the automobile performance under road-driving conditions. Two examples of transient performance prediction, including a sudden full-throttle acceleration at a fixed gear and a changing-gear starting acceleration from standstill, are demonstrated in this paper. These examples show that the relation between the engine speed and the road speed under accelerating conditions is very different to the steady-state relationships normally assumed.
The Magnitude of The Losses in the Steel Pushing V-Belt Continuously Variable Transmission
Authors: Micklem J D , Longmore D K , Burrows C R 
Published: February 2007

This paper investigates the reasons why in current passenger vehicles the steel pushing V-belt continuously variable transmission (CVT) has failed to achieve an improvement in fuel economy even though the CVT is correctly controlled and allows the engine to operate near to its region of maximum efficiency. It is shown that the overall efficiency of the transmission is low, especially at the lower vehicle speeds. The main losses are due to the belt torque loss, the hydraulic pump loss and the loss due to slip in the belt-pulley system. It is shown that a considerable improvement in vehicle economy is obtainable by controlling the transmission so that the sum of these losses is minimized as well as seeking to optimize the engine efficiency. This improved overall efficiency is achieved by operating the CVT with much lower pulley clamping pressures than have previously been considered desirable.
Spatial Repeatability of Measured Dynamic Tyre Forces
Authors: Cole D J , Collop A C , Potter T E C , Cebon D 
Published: February 2007

The dynamic tyre forces generated by heavy goods vehicles are measured with a portable load measuring mat and used to investigate ‘spatial repeatability’. The mat is 56 m long, 13 mm thick and has 141 capacitative strip sensors, spaced at 0.4 m intervals. Two sets of experiments are described. In the phase 1 experiments the measured dynamic tyre forces generated by fourteen articulated vehicle combinations (three tractors and five trailers) are used to confirm previous theoretical predictions of spatial repeatability. In the phase 2 experiments the dynamic tyre forces generated by over 1500 heavy goods vehicles travelling on a British trunk road are used to estimate the degree of repeatability exhibited by a typical highway fleet. Spatial repeatability is assessed using the ‘spatial repeatability index’ (SRI), and a method is developed to correct the SRI for sensor noise. Approximately half the vehicles tested were found to contribute to a spatially repeatable pattern of road loading.
Diesel Injector Dynamic Modelling and Estimation of Injection Parameters from Impact Response Part 2: Prediction of Injection Parameters from Monitored Vibration
Authors: Gu F , Ball A D , Rao K K 
Published: February 2007

Part 2 of this paper presents the experimental and analytical procedures used in the estimation of injection parameters from monitored vibration. The mechanical and flow-induced sources of vibration in a fuel injector are detailed and the features of the resulting vibration response of the injector body are discussed. Experimental engine test and data acquisition procedures are described, and the use of an out-of-the-engine test facility to confirm injection dependent vibration response is outlined. Wigner–Ville distribution (WVD) analysis of non-stationary vibration signals monitored on the injector body is used to locate regions of vibration in the time–frequency plane which are responsive to injection parameters. From the data in these regions, estimates of injection timing and fuel pressure are obtained. Accurate estimation of injection parameters from externally monitored vibration is shown to pave the way for the detection and diagnosis of injection system faults. Moreover, it is demonstrated that the technique provides an alternative method for the set-up, checking and adjustment of fuel injection timing.
Burst Pressures of Pipes Containing Dents and Gouges
Authors: Lancaster E R , Palmer S C 
Published: February 2007

Mechanical damage to pipelines may take the form of dents and gouges, which may also incorporate cracks. The combination of a gouge within a dent has long been recognized as the most severe form of damage, and can result in failure at very low internal pressures. Yet despite much expensive full-scale testing, predictions of subsequent burst pressures of such damaged pipes are unreliable, and assessment procedures are very conservative. This paper describes a series of burst tests on model aluminium pipes containing dents and smooth gouges, specifically excluding cracks. The results show that gouges located near the axial extremity of a dent cause low-pressure failure, and indicate the presence of two regions of high strain at the axial extremities of the initial dent. For gouges in other areas of the dent, the Battelle flow stress dependent model for ductile failure of plain gouges in undented pipes is shown to give reasonable predictions of burst pressures, which are independent of the dent depth. In all of the pipes tested, failure was ductile, and this is attributable to the absence of cracks. Pipes withstood pressures in excess of the corresponding normal operating pressures, except where gouges were located near the axial extremity of the dent. The results throw much light on the published results from tests on full-size steel pipes, and support earlier hypotheses that removal of cracks from a damaged pipe by light grinding may significantly increase the pipe burst pressure.
Strain Concentrations in Pressurized Dented Pipes
Authors: Lancaster E R , Palmer S C 
Published: February 2007

Knowledge of the strain distribution in a dent is crucial in assessing the severity of damage to pipes. Accordingly this paper presents the results of a series of tests to measure strains and displacements in previously dented aluminium pipes subject to increasing internal pressure. Indentation of unpressurized and pressurized pipes was caused by a rigid sphere and resulted in short smooth dents of depths up to 16 per cent of pipe diameter. Strain changes on the external pipe surface were monitored by strain gauges and a photoelastic coating. The results identify two stationary crescent-shaped regions of high external strain at the axial extremities of the initial dent, where strain concentration factors of 10 were recorded in the early (elastic) stages of pressurization, increasing to a maximum of 28 in one particular dent. The results have immediate application to the assessment of a gouge within a dent, which has long been recognized as the most severe form of mechanical damage to pipelines and can result in failures at very low internal pressures. A parallel series of burst tests by the authors revealed that gouges located near the axial extremities of the initial dent may cause premature failure. The strain concentration results presented here help to explain this behaviour, and indicate the size, shape and location of the regions of high external strain.
Analysis of the Mechanics for Drawing Polyvinyl Chloride Tubes over an Expanding Mandrel
Authors: Kakadjian S , Craggs G , Ward I M 
Published: February 2007

An analysis is presented of the mandrel drawing process in which a tubular polyvinyl chloride (PVC) billet is drawn over an expanding mandrel so as to achieve a tubular product having a high degree of molecular orientation in the hoop and axial directions and enhanced mechanical properties. The stress and deformation behaviour of material moving over the mandrel are determined from equilibrium considerations and modelling of the material using the Ogden representation. Experimental results from drawing tests carried out on a large-scale test facility are presented and the effects of mandrel semi-angle, mandrel exit diameter and processing temperature on drawing behaviour are evaluated. Good agreement is shown between the experimental results and theoretical predictions of final product thickness, die exit stress and drawing load.
Developments in Warship Design and Engineering
Authors: Betts C V 
Published: February 2007

Warships, together with their weapons and major sub-systems, take ten to fifteen years to design and build and then spend twenty-five years or more in service. The Royal Navy fleet of today was designed during the Cold War for conditions rather different from those now pertaining. Designs now on the drawing board (or, more correctly, on the computer screen) and the research and development required to underpin them are aimed at requirements where the enemy threat is uncertain, warfare technology proceeds apace and the need for maximum value for money in reduced defence budgets is paramount. Developments in weapon systems and command, control and communication systems are impressive and far reaching. However, developments in surface warship and submarine naval architecture and marine engineering are potentially as important to the long-term effectiveness and affordability of the Fleet. This paper looks at the technologies being considered for future designs with emphasis on hull and marine engineering developments. These include novel hull forms such as the trimaran and possibly the next major step in surface warship propulsion—the all-electric ship with electric transmission and low fuel consumption gas turbines as prime movers for electricity generation. The paper also discusses the importance of ‘human factors’ in the design process, the increasing use of commercial standards to control costs of both hardware and software, and improvements in naval ship and submarine design tools for use in the crucial concept design phase.
Civil Airframe Structural Integrity—Some Probabilistic Aspects of Risk Assessment
Authors: Jones M R 
Published: February 2007

Fatigue is the mechanism of progressive damage which may ultimately limit the economic life of an airframe. However, there is an intrinsic variability in the life of nominally identical structures subjected to alternating loads. Currently, the uncertainty in the estimated fatigue lives is accounted for in design by applying ‘scatter factors’ to the results of full-scale fatigue tests or to deterministically calculated lives. An alternative approach is to perform a reliability analysis to ensure that the weaker members of an aircraft fleet will meet the design aims with a pre-defined level of reliability. This paper aims to develop and apply analytical models required to: determine the safe-life or inspection threshold for a given fleet size with a prescribed reliability and review and revise the inspection programme based on the results of in-service inspections.
Impact of Second Generation Single Crystal Superalloys on Foundry Technology
Authors: Ford D A 
Published: February 2007

Superalloys developed after the Second World War to meet the demands of the jet engine reached the limit of known alloying in the late 1960s. The continuing requirement for materials with higher temperature capabilities was met by developments in solidification and processing technologies leading to directional solidification and single crystals. By the mid 1980s it was apparent that further improvements in material temperature capability could be achieved by alloying with such exotic elements as rhenium and yttrium. The success of these alloys is due to the retarding of diffusion rates and greatly increased oxidation resistance at high temperatures. Superalloys containing these elements are generally known as second generation materials and are by virtue of their unique advantages very difficult to process. In particular the slow diffusion rates give significant difficulties with heat treatment and the retention of yttrium presents a foundry challenge of the highest order. This paper will review the advantages of second generation material and address the process problems associated with their successful introduction into service.
Stresses in a Splineless Drive for Aero-Engines
Authors: Fessler H , Moore C J 
Published: February 2007

This paper describes an alternative to splines for connecting turbine discs to shafts. The trilobe shape consists of six smoothly blending 60° circular arcs of two alternating radii; it is between a circle (both radii equal) and a triangle (smaller radius zero, larger radius infinite). Frozen-stress, photoelastic models of a realistic disc and a tubular shaft have been designed, made and loaded centrifugally, under static torsion and under combined torsion and rotation. The results show that the greatest centrifugal stresses in the disc occur in the bore at the tips of the trilobe and the greatest contact stresses occur near the transition from the larger to the smaller radius. The centrifugal stress concentrations due to the trilobe were small. Bore deformation and backlash due to differential centrifugal expansion were measured and found to be acceptable for a similar ceramic or nickel alloy disc.
The Wear of Cross-Linked Polyethylene against Itself
Authors: Joyce T J , Ash H E , Unsworth A 
Published: February 2007

Cross-linked polyethylene (XLPE) may have an application as a material for an all-plastic surface replacement finger joint. It is inexpensive, biocompatible and can be injection-moulded into the complex shapes that are found on the ends of the finger bones. Further, the cross-linking of polyethylene has significantly improved its mechanical properties. Therefore, the opportunity exists for an all-XLPE joint, and so the wear characteristics of XLPE sliding against itself have been investigated. Wear tests were carried out on both reciprocating pin-on-plate machines and a finger function simulator. The reciprocating pin-on-plate machines had pins loaded at 10 N and 40 N. All pin-on-plate tests show wear factors from the plates very much greater than those of the pins. After 349 km of sliding, a mean wear factor of 0.46 × 10−6 mm3/N m was found for the plates compared with 0.021 × 10−6 mm3/N m for the pins. A fatigue mechanism may be causing this phenomenon of greater plate wear. Tests using the finger function simulator give an average wear rate of 0.22 ×10−6 mm3/N m after 368 km. This sliding distance is equivalent to 12.5 years of use in vivo. The wear factors found were comparable with those of ultra-high molecular weight polyethylene (UHMWPE) against a metallic counterface and, therefore, as the loads across the finger joint are much less than those across the knee or the hip, it is probable that an all-XLPE finger joint will be viable from a wear point of view.
Proximal Interphalangeal Joint Dimensions for the Design of a Surface Replacement Prosthesis
Authors: Ash H E , Unsworth A 
Published: February 2007

The bones from 83 proximal interphalangeal joints (PIPJs) were dissected in order to determine the shape and size of the articular surfaces. The bones were modelled in acrylic dental bone cement and the original bones and replicas were then sectioned and shadow-graphed. Dimensions were taken from these shadowgraphs to be used in the design of a surface replacement prosthesis for the PIPJ. It was found that the bi-condylar heads of the proximal and middle phalanges were circular in the sagittal plane as was the base of the middle phalanx. However, the radius of curvature of the middle phalangeal base was greater than that of the proximal phalangeal head indicating that the PIPJ is not a conforming joint. The alignment of the radial and ulnar condyles of the proximal phalangeal bones was investigated and it was found that the index and middle finger bones tended to have a more prominent ulnar condyle while the ring and little finger bones tended to have a more prominent radial condyle. This was due to a slight difference in diameters of the two condyles. The proximal phalangeal bone lengths L ranged from 29–52 mm, maximum head widths W from 8.5–15.5 mm and maximum diameters D of the best-fit circles to the sagittal profile of the bone head from 6–11 mm. The middle phalangeal bone lengths ranged from 16–35 mm, maximum head widths from 8.5–12 mm and maximum diameters from 5–7.5 mm. The relationships and ratios between these dimensions for the proximal and middle phalanges have been calculated.
Estimation of Wear in Total Hip Replacement Using a Ten Station Hip Simulator
Authors: Brummitt K , Hardaker C S 
Published: February 2007

The results of hip simulator tests on a total of 16 total hip joints, all of them 22.25 mm Charnley designs, are presented. Wear at up to 6.75 million cycles was assessed by using a coordinate measuring machine. The results gave good agreement with clinical estimates of wear rate on the same design of joint replacement from a number of sources. Good agreement was also obtained when comparison was made with the published results from more sophisticated simulators. The major source of variation in the results was found to occur in the first million cycles where creep predominates. The results of this study support the use of this type of simplified simulator for estimating wear in a total hip prosthesis. The capability to test a significant number of joints simultaneously may make this mechanism preferable to more complex machines in many cases.
Effect of Counterface Material on the Characteristics of Retrieved Uncemented Cobalt-Chromium and Titanium Alloy Total Hip Replacements
Authors: Brummitt K , Hardaker C S , McCullagh P J J , Drabu K J , Smith R A 
Published: February 2007

A number of total hip components explanted at revision with bearing surfaces in either cobalt-chromium-molybdenum alloy or titanium-6% aluminium-4% vanadium alloy were examined and compared to contemporaneously manufactured but unused items; particular attention was paid to the bearing surfaces which were examined visually, by low-power microscopy, scanning electron microscopy (SEM), confocal microscopy, white light interferometry, laser profilometry and conventional stylus profilometry. The cobalt alloy heads maintained their surface finish well over periods up to 12 years. The titanium implants became badly damaged over much shorter periods although even badly scratched heads continued to meet the current standards for titanium alloy heads. Analysis showed that the damage to the titanium alloy heads was not a random but a well-defined process of scarring of a consistent size created by abrasion with small particles of bone. These damaged heads had the potential to wear the matching UHMWPE components rapidly creating large amounts of polymer debris. The finding that measurement of these damaged heads is within current standards raises concerns as to whether current standards incorporate fully the requirements for clinical performance.