bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensor-based performance monitoring of a control valve unit
Authors: Sharif M A , Grosvenor R I 
Published: October 2002

This is the second of a series of papers dedicated to the research and development work in the field of industrial control valve condition monitoring and fault diagnosis. This paper reports new results that were produced after conducting a series of tests to monitor the dynamic performance of a typical industrial control valve unit (which consisted of a control valve, an actuator and a digital valve controller) under various operating conditions. These included the gradual blockage of the actuator's vent hole, the build-up of deposits on the valve stem and the incorrectly replaced valve stem seals. These conditions were created by using a precision in-line flow regulator for the actuator's vent hole and a thin layer of a special type of adhesive film that crystallized and bonded to the valve stem and by replacing the polytetrafluorethylene valve stem seals with graphite-type seals under controlled conditions. The effects of these abnormalities on the pressure that was developed in the upper diaphragm casing of the actuator as well as the flowrate were carefully monitored using a range of sensors that were integrated into an intelligent data acquisition and processing system. It was evident that certain types of fault, including the fully blocked actuator's vent hole, could be identified with great accuracy using the responses of the flow transmitter and the pressure transducer. On the other hand, other types of fault, such as the simulated build-up of deposits on the valve stem, required a comparison of their statistical properties in addition to the transducers' responses to determine the condition reliably. The current-to-pressure converter is a vital element of any digital valve controller and its performance was, therefore, monitored under various conditions to establish the effects of the faults on its operation. The paper concludes by outlining the main results and the limitations of the diagnostic techniques utilized as well as the future work, which is to integrate the results into a user-friendly diagnostic system based on the Microsoft visual basic programming language.
Use of extended exergy analysis to evaluate the environmental performance of machining processes
Authors: Creyts J C , Carey V P 
Published: October 2002

Traditional applications of exergy analysis have focused upon the optimization of energy use in thermal and chemical processes. This paper introduces a form of exergy analysis in which the methodology is extended to consider the characteristics of material flows in a process as well. This new form of analysis, termed extended exergy analysis (EEA), is shown to be particularly useful in valuating the environmental performance of industrial processes. EEA differs from traditional theory in its requirement that all ground states be defined such that they are en6ironmentally acceptable. Environmental acceptability can be determined using a number of health, occupational and ecological criteria. By integrating biological considerations into the existing physical definition, EEA provides manufacturers and regulators alike with relevant information regarding the costs of achieving environmentally benign production. These costs are valued consistently for both raw material and energy inputs and product and residual outputs, affording degrees of transparency and objectivity not present in other valuation methodologies. Application of the technique to a case study involving the machining of aluminium is developed.
Equilibrium of crack growth and wear rates during unlubricated rolling-sliding contact of pearlitic rail steel
Authors: Fletcher D. I. , Beynon J. H. 
Published: October 2002

It is generally accepted that large rolling contact fatigue cracks in rails do not develop during unlubricated rolling-sliding contact, and damage under these conditions is restricted to wear of the rail steel. However, close examination of a worn rail steel surface reveals the presence of a multitude of wear flakes, the roots of which closely resemble shallow rolling contact fatigue cracks. Experiments have been conducted under unlubricated rolling-sliding conditions to examine the early development of flakes, or cracks, using a laboratory-based, twin-disc test machine to simulate the contact pressure and slip characteristic of the contact between a rail and a locomotive driving wheel. Small defects were found after as few as 125 unlubricated contact cycles. It was found that an equilibrium between crack growth rate and surface wear rate was established after approximately 10 000 cycles, leading to a shallow steady state crack depth. Initial crack growth by ratchetting (accumulation of unidirectional plastic strain until the critical failure strain of the material is reached), followed by shear stress-driven crack growth described by fracture mechanics, was found to be a sequence of mechanisms in qualitative agreement with the observed crack growth and steady state crack depth.
Network 21: Impact on rail freight traffic
Authors: Fricke E , Pohl M 
Published: October 2002

Following the rail reform in Germany, Deutsche Bahn remained in the ownership of the German State but the company was divided into a number of subsidiaries, including long-distance and regional operators and DB Netz AG, the infrastructure manager. This market-driven organization is obliged to recover completely the costs of infrastructure provision by levying utilization charges (principle of full cost coverage). Hence, the market conditions of railway undertakings, such as those providing rail freight services, are at least partially determined by the level of costs of providing the infrastructure. The current high level of costs at DB Netz AG must be significantly reduced if the railways are to hold their own against intense competitive pressure from road and waterways. It will not be possible to achieve this goal purely by continuing with on-going rationalization measures and additional investment in the track infrastructure (new and upgraded lines). Both the rail reform goal of switching more traffic to rail and the purely commercial interests of DB Netz AG necessitate a comprehensive increase in productivity and enhancement of product at realistic market prices. In order to achieve these objectives, DB Netz AG chose a novel form of network management which relies strongly on the separation of traffic flows of different types. This was defined as the Network 21 strategy. The Network 21 strategy will also enhance the ability of operators to deliver both passenger and freight services in a more timely manner.
Problems caused by the motorway/railway freight traffic share in the Tyrol
Authors: Knoflacher H 
Published: October 2002

Managing transit freight traffic across the Alps was an important source of income for the regional population for several hundred years. The introduction of technical transport systems, first railway followed by car and truck, changed the situation radically. No more stops were necessary and therefore the positive economic effects from transit traffic for the local alpine population were lost. The benefits moved to big economic structures outside the alpine regions. Noise and air pollution from uncontrolled growth of truck traffic in narrow alpine valleys had negative effects on quality of life as well as on tourism. Resistance against transit freight traffic through the Alps therefore has an economic background too. To shift goods from road to rail, a toll on haulage charge over the Brenner route was introduced. Harmonization with European rules removed this financial barrier by about 90 per cent. Improvements of rail infrastructure, like the bypass of Innsbruck, have no effect on the modal split. Also, the eco-point system is not an effective instrument as it is not obeyed by the relevant neighbours in the European Union (EU). Road transport is therefore not only faster and simpler but also much cheaper than rail. Effective measures must be introduced to reach the desired goals, especially as these are also officially declared goals of the EU commission. A night-time ban for trucks, a better management on the rail network (not only in the Alps, but in the whole of Europe) and a substantial increase in costs for road freight transport will be necessary. If the alpine freight transit problem is not reduced by politicians, it is very likely that the local population will increasingly block the north-south traffic on the road.
Investigation of the separation bubble formed behind the sharp leading edge of a flat plate at incidence
Authors: Crompton M J , Barrett R V 
Published: October 2002

Detailed measurements of the separation bubble formed behind the sharp leading edge of a flat plate at low speeds and incidence are reported. The Reynolds number based on chord length ranged from 0.1 × 105 to 5.5 × 105. Extensive use of laser Doppler anemometry allowed detailed velocity measurements throughout the bubble. The particular advantages of laser Doppler anemometry in this application were its ability to define flow direction without ambiguity and its non-intrusiveness. It allowed the mean reattachment point to be accurately determined. The static pressure distribution along the plate was also measured. The length of the separation bubble was primarily determined by the plate incidence, although small variations occurred with Reynolds number because of its influence on the rate of entrainment and growth of the shear layer. Above about 105, the Reynolds number effect was no longer evident. The reverse flow boundary layer in the bubble exhibited signs of periodic stabilization before separating close to the leading edge, forming a small secondary bubble rotating in the opposite sense to the main bubble.
Riveted single lap joints. Part 1: A numerical parametric study
Authors: Fung C-P , Smart J 
Published: October 2002

Snap and countersunk riveted single lap joints with either one or two-rows of rivets have been analysed using finite elements and fatigue tests have been performed. In this first paper, a numerical parametric study, the joints are subjected to an alternating cyclic load and plasticity and non-linear geometry are considered. The stresses around the rivet hole and the deformed shapes of the joints are presented together with the effects of varying the clamping force, the interference fit of the rivet, the coefficient of friction and the geometry of the joints when the joints are subjected to various loading histories. The effect of changing the variables is shown to be in agreement with other published data
Practical issues relating to statistical failure analysis of aero gas turbines
Authors: Cole G K 
Published: October 2002

Statistical failure analysis of aero gas turbines presents many special problems. Various difficulties must be overcome, including the paucity and form of available data with its heavily censored nature, selecting the right analysis method, the validity of the underlying modelling assumptions and the correct interpretation of the results. This paper outlines the formal Rolls-Royce approach to quantifying numerical risk for safety and reliability, and the pivotal role played by the Weibull distribution. It reviews the generic forms of the censored failure data obtained from test and service environments. The limitations of the current analysis techniques are reviewed.
A novel shearography system for aerospace non-destructive testing
Authors: Parker S C J , Salter P L 
Published: October 2002

Non-destructive testing (NDT) is a vital process in aerospace engineering to ensure the structural integrity of components. Shearography offers numerous advantages over established inspection techniques. In particular, it has the potential to reduce inspection times by an order of magnitude, can be applied to complex geometries and does not require immersion of the component. These advantages are likely to become increasingly important for next-generation aircraft designs, which necessitate the use of highly complex structures and materials. Despite the inherent advantages of optical inspection, commercial systems have failed to address many of the practical limitations. This paper identifies the problems that have inhibited technology transfer of shearography from the laboratory to the harsh production environment. Innovative solutions are presented and a production demonstrator is described which has been built at British Aerospace to evaluate these concepts. The system is currently under evaluation by both optical experts and NDT specialists. Early results, validated by destructive testing, have already been valuable in inspecting components that have been notoriously difficult to examine using existing techniques.
Biological reactions to wear debris in total joint replacement
Authors: Ingham E , Fisher J 
Published: October 2002

The vast majority of total hip prostheses currently implanted consist of a hard metal or ceramic femoral head articulating against an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. Over the last 10 years, evidence has accumulated to show that these prostheses are prone to failure due to late aseptic loosening and few survive beyond 25 years. With an increasing need to implant hip prostheses in the younger, more active patient the need to understand the mechanisms of failure and to develop artificial hip joints using alternative materials have become major issues in the orthopaedic community. This review focuses initially on our current understanding of the biological reactions to UHMWPE prosthetic wear debris in vivo and in vitro since this is believed to be the main cause of late aseptic loosening. While the precise mechanisms of osteolysis induced by UHMWPE wear debris have not been elucidated, the major message to emerge is that it is not the wear volume that determines the biological response to the debris, but the concentration of the wear volume that is within the critical size range (0.2-0.8 μm) for macrophage activation. The review then considers whether the problem of wear-debris-induced osteolysis may be overcome with the use of new generation metal-on-metal or ceramic-on-ceramic prostheses. For metal-on-metal prostheses, the prospects for increasing the osteolysis free life of the implant are good but additional biological problems associated with the nanometre size and reactivity of the wear particles in vivo may emerge. For the ceramic-on-ceramic prostheses, although initial prospects are encouraging, more data are needed on the characteristics of the wear particles generated in vivo before predictions can be made. It is concluded that the pre-clinical testing of any new materials for joint replacement must include an analysis of the wear particle characteristics and their biological reactivity in addition to the usual assessment of wear.
A new method for quantitative evaluation of perceived sounds from mechanical heart valve prostheses
Authors: Johansen P , Riis C , Hasenkam J M , Paulse P K , Nygaard H 
Published: October 2002

Closing clicks from mechanical heart valve prostheses are transmitted to the patient's inner ear mainly in two different ways: as acoustically transmitted sound waves, and as vibrations transmitted through bones and vessels. The purpose of this study was to develop a method for quantifying what patients perceive as sound from their mechanical heart valve prostheses via these two routes. In this study, 34 patients with implanted mechanical bileaflet aortic and mitral valves (St Jude Medical and On-X) were included. Measurements were performed in a specially designed sound insulated chamber equipped with microphones, accelerometers, preamplifiers and a loudspeaker. The closing sounds measured with an accelerometer on the patient's chest were delayed 400 ms, amplified and played back to the patient through the loudspeaker. The patient adjusted the feedback sound to the same level as the ‘real-time’ clicks he or she perceived directly from his or her valve. In this way the feedback sound energy includes both the air- and the bone-transmitted energies. Sound pressure levels (SPLs) were quantified both in dB(A) and in the loudness unit sone according to ISO 532B (the Zwicker method). The mean air-transmitted SPL measured close to the patient's ear was 23 ± 4dB(A). The mean air- and bone-transmitted sounds and vibrations were perceived by the patients as an SPL of 34 ± 5dB(A). There was no statistically significant difference in the perceived sound from the two investigated bileaflet valves, and no difference between aortic and mitral valves. The study showed that the presented feedback method is capable of quantifying the perceived sounds and vibrations from mechanical heart valves, if the patient's hearing is not too impaired. Patients with implanted mechanical heart valve prostheses seem to perceive the sound from their valve two to three times higher than nearby persons, because of the additional bone-transmitted vibrations.
Parametric optimization for tumour identification: Bioheat equation using ANOVA and the Taguchi method
Authors: Sudharsan N M , Ng E Y K 
Published: October 2002

Breast cancer is the number one killer disease among women. It is known that early detection of a tumour ensures better prognosis and higher survival rate. In this paper an intelligent, inexpensive and non-invasive diagnostic tool is developed for aiding breast cancer detection objectively. This tool is based on thermographic scanning of the breast surface in conjunction with numerical simulation of the breast using the bioheat equation. The medical applications of thermographic scanning make use of the skin temperature as an indication of an underlying pathological process. The thermal pattern over a breast tumour reflects the vascular reaction to the abnormality. Hence an abnormal temperature pattern may be an indicator of an underlying tumour. Seven important parameters are identified and analysis of variance (ANOVA) is performed using a 2n design (n = number of parameters, 7). The effect and importance of the various parameters are analysed. Based on the above 27 design, the Taguchi method is used to optimize the parameters in order to ensure the signal from the tumour maximized compared with the noise from the other factors. The model predicts that the ideal setting for capturing the signal from the tumour is when the patient is at basal metabolic activity with a correspondingly lower subcutaneous perfusion in a low temperature environment.
Comparison of gas plasma and gamma irradiation in air sterilization on the delamination wear of the ultra-high molecular weight polyethylene used in knee replacements
Authors: Reeves E A , Barton D C , FitzPatrick D P , Fisher J 
Published: October 2002

Early failure of knee replacements is thought to be due to the combination of sterilization by gamma irradiation in air and the high cyclic stresses that they endure during use. Such failures are shown through delamination and permanent deformation of the ultra-high molecular weight polyethylene (UHMWPE) component. This study investigated whether gas plasma sterilization, as an alternative to gamma irradiation in air, would give better performance after ageing in a knee replacement using a metal pin on polymer plate wear test. Fourier transform infrared (FTIR) analysis was performed on the components to assess oxidation levels and a finite element stress analysis model is presented to estimate strain at failure in the UHMWPE. Delamination occurred in the majority of the gamma-irradiated plates but did not occur in any of the gas-plasma-sterilized plates. The FTIR analysis showed that the plates gamma irradiated in air were highly oxidized when compared with the gas-plasma-sterilized plates. Plastic strain at failure was determined for the gamma-irradiated plates and found to be less than 2.4-14 per cent.
In vitro comparison of the two hard-hard articulations for total hip replacements
Authors: Rieker C , Konrad R , Schoun R 
Published: October 2002

Polyethylene particle disease is one of the major causes of late aseptic loosening of total hip replacement. Two hard-hard articulations (alumina-on-alumina and metal-on-metal) have been developed in Europe as an alternative to the ultra-high molecular weight polyethylene (UHMWPE) articulations. Even though these hard-hard articulations are on the market and numerous reports have been published about them, only a very limited number of studies allowing a direct in vitro comparison of the two articulations have been published so far. This paper compares in vitro these two types of articulation (alumina-on-alumina and metal-on-metal), which have been tested with a hip simulator for their tribological behaviour using exactly the same experimental methodology. This comparison shows that these two types of hard-hard articulation have very similar abrasive wear behaviour with four main features: 1. A running-in wear period (1 × 106 cycles) gives a cumulative wear of about 20 μm with head diameters of 28 mm. 2. After the running-in wear, there is a stabilization of the linear wear behaviour with a low linear wear rate/106 cycles for both types of articulation. 3. The volumetric wear rate of both articulations (<2.0 mm3/year for head diameters of 28mm) is significantly lower than that observed for metal-on-polyethylene or ceramic-on-polyethylene articulations having the same head diameter. 4. Abrasive wear is readily apparent (indicating a mixed lubrication regime) with both types of articulation. The extremely low wear performance of these articulations is confirmed and they constitute a lowwear alternative to the UHMWPE articulations currently used.
Friction of composite cushion bearings for total knee joint replacements under adverse lubrication conditions
Authors: Stewart T , Jin Z M , Fisher J 
Published: October 2002

Conventional joint replacements consist of a polished metallic or ceramic component articulating against a layer of polyethylene. Although the friction in the contact between these articulating surfaces is low, polyethylene wear is produced as a result of a boundary/mixed lubrication regime. Wear debris is generated by direct asperity contact, abrasion, adhesion and fatigue, and has been shown to cause adverse tissue reactions which can lead to joint failure. The introduction of soft compliant materials, similar in stiffness to articular cartilage, has shown that with cyclic loading and relative motion between the articulating surfaces typical of normal walking, a fluid film can be maintained through combined entraining and squeeze-film actions, and hence wear can be minimized. For 95 per cent of the time, however, we are not walking but standing still or moving slowly. A pendulum simulator has been used in the present study to investigate the effect of adverse tribological conditions which may lead to fluid film breakdown, such as severe cyclic loading, particularly in the swing phase, reduced sliding velocity, reduced stroke length and start-up after a period of constant loading. Friction of a model composite cushion knee bearing, manufactured from a graded modulus (20–1000 MPa) layer of polyurethane, sliding against a polished metal cylinder has been measured for various lubricants and the results have been analysed using a Stribeck assessment. Severe cyclic loading, decreased sliding velocity and decreased stroke length have been found to limit the degree of fluid entrainment previously allowed during the swing phase of normal walking, thus allowing breakdown of fluid films and elevated levels of friction and surface damage. Soft layer joint replacements must therefore be designed to operate with thick elastohydrodynamic fluid films to provide some degree of protection when tribological conditions become severe, or alternatively incorporate alternative boundary or mixed lubrication mechanisms. This study quantifies a potential limitation of the cushion bearing concept.