bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and application of the large-scale auto-centring machine jig
Authors: Zhao J-S , Dong F , Zhang Z-M , Zhang G-T
Published: July 2008

The purpose of this research is to investigate the structure, principle, and main design issues of a large-scale, high-accuracy auto-centring machine jig, as well as the practical application of finite element analysis in the design process of elastic sheaths. This kind of jig is suitable for machining parts with large, thin-walled, and complex shapes such as a sleeve barrel. The designed jig has been used in the manufacturing process of rocket engines.
Application of the hot isostatic pressing process on a thermally sprayed coating layer on copper dies
Authors: Kamara A M , Davey K
Published: July 2008

Recent research has shown that copper-alloy dies sprayed with a protective steel layer can potentially replace steel dies in the pressure die casting process for the purpose of rapid heat extraction. The deposited layer is required to withstand abrasion, thermal shock, and cyclic loading, and be resistant to debonding from the copper-die substrate. This paper is concerned with an experimental investigation into the application of the HIP process to ascertain its effectiveness towards enhancing the bond strength, hardness, and densification of chrome steel coatings on a copper substrate. A particular focus of the paper is on the use of partial encapsulation coupled with the use of ceramic paper whose purpose is to transfer the loading pressure and prevent bonding between the die and the encapsulation container. It is shown in the paper that partial encapsulation is effective and can be used to HIP localized regions of a die. The ceramic paper was shown to be effective in transmitting loading and has the added advantage of providing relatively good surface finish as compared with that obtained with ceramic powder. The results of the experimental trials show reduced porosity and increased bond strength with application of the HIP process. In addition hardness values are shown to be reduced to levels typically found in traditional die-tool steels.
Buoyancy-induced convection in differentially heated superposed two fluid layers in a rectangular cavity
Authors: Punjabi S , Muralidhar K , Panigrahi P K
Published: July 2008

Buoyancy-driven convection in a differentially heated rectangular cavity containing layers of air—water, air—silicone oil, and silicone oil—water has been experimentally studied using laser-interferometry. The cavity has dimensions 32 × 32 mm2 in the vertical plane and length 447 mm. The layer thicknesses were taken to be equal. Experiments are conducted with three cavity temperature differences of 10, 15, and 18 K. The flow field is mapped in the direction parallel to the cavity length using a Mach-Zehnder interferometer. The flow regimes (such as steady two-dimensional, time-dependent, etc.) established in the individual fluid layers were compared with the published regime diagrams of single fluid layer at different Rayleigh numbers. Quantities such as the interface temperature, average Nusselt number, and the temperature profiles were determined from the interferograms. The interface shapes are recorded in the form of shadowgraphs. These results were also looked upon in terms of the coupling mechanism established at the interface.

The major conclusions arrived in this study are as follows. In the experiments involving air, the layers were found to be thermally coupled. The unsteadiness in water could however be transmitted to air in the mechanical coupling mode. The presence of silicone oil over water led to mechanical coupling in the sense that the convective field in water was visibly retarded. The interface temperature determined from the experiments matched those from correlations for a single fluid whenever the coupling was thermal in origin. The differences were higher during mechanical coupling. The interface deformation correlated well with the roll movement visible in the fringes.
Opposing steady and transiently developing jets in relation to laser machining
Authors: Arshed G M , Shuja S Z , Yilbas B S , Budair M O
Published: July 2008

The opposing jet situation in relation to laser gas assisted drilling process is considered. In this case, impinging steady jet resembling the assisting gas jet and transiently developing jet resembling the vapour jet emanating from the solid surface due to laser ablation are employed in the analysis. A numerical method using a control volume approach is introduced for simulating the flow and temperature fields. Since the thermophysical properties of the transiently developing vapour jet are not known, helium jet at 1500 K is accommodated in the simulations. Helium is a chemically stable inert gas, which does not ionize at 1500 K. The inlet conditions of transiently developing jet are taken from the previous study. It is found that the enhancement of the radial flow, due to opposing situation, generates a circulation cell next to the steady jet boundary. The orientation and size of the circulation cell changes with time thereby modifying the streamline curvature of the steady jet. The transiently developing jet does not behave like a transiently self-developing one. Moreover, the radial jet resulted from the opposing jets behaves almost like a free jet.
Jet emerging from an annular nozzle and impinging onto cylindrical cavity: Effect of jet velocity on flow structure and heat transfer rates
Authors: Shuja S Z , Yilbas B S , Khan S M A
Published: July 2008

In laser gas assisting processes, nozzles are used to accelerate the impinging gas and attain a proper flow structure to improve the quality of the end product. In this study, the jet emerging from an annular nozzle and impinging onto a cylindrical cavity is considered. The effects of jet velocity at nozzle exit onto the flow structure in the region of the cavity and heat transfer rates from the cavity surface are examined. To resemble the laser-produced cavity, the cavity wall temperature is kept elevated (almost the melting temperature of the substrate material). Reynolds stress turbulence model is exploited to account for the turbulence. In the simulations, four jet velocities, two outer angles of the annular nozzle, and two depths of the cylindrical cavity are employed while air is used for the working fluid. It is found that jet velocity has a significant effect on the heat transfer rates and skin friction, which is more pronounced with increasing cavity depths.
An investigation of the effect of the gap values between the overlap portions of the spot-welded pieces on fatigue life
Authors: Ertas A H , Yilmaz Y , Baykara C
Published: July 2008

In this study, the effect of the space or gap values — between the overlap portions of the spot welded specimens — which is especially important for spot-welded joints subjected to uniaxial in-plane loads, on fatigue life are investigated. In order to do these investigations, a computer programme is developed using ANSYS (version-10) finite-element programme. Numerical results based on the developed computer programme are compared with the experimental results conducted by Sheppard for the validation of the programme and are found to be satisfactory. Fatigue life properties for different type of spot-welded specimens and different gap values are calculated numerically using this developed computer programme with different fatigue-life approaches to see the gap effect on the fatigue life of the spot-welded specimens. It is found that maximum stress and strain values increase, hence fatigue life decrease, with increasing gap values, and this situation is clearer for tensile shear (TS) specimens than modified tensile shear (MTS) ones because of the flanged pieces of the MTS specimens. It is also found that maximum stresses and strains, hence the fatigue-life values, do not change so much for gap values lower than 0.0025 mm.
Study on combined influence of inter-asperity cavitation and elastic deformation of non-Gaussian surfaces on flow factors
Authors: Meng F-M , Qin D-T , Chen H-B , Hu Y-Z , Wang H
Published: July 2008

The combined influence of inter-asperity cavitation and elastic deformation of non-Gaussian surfaces on flow factors is numerically investigated based on the equations for flow factor analyses, since some engineering surfaces are non-Gaussian. For this task, non-Gaussian surfaces are generated at first through a digital filter technique by using authors’ computer code whose validity is proven. The numerical results show that the pressure flow factor increases whereas the shear flow factor decreases with low film thickness-to-roughness ratio ( h/σ < 3 or so). This is due to the above-said combined influence, if the oblique flow of lubricant is not obvious. But for a high film thickness-to-roughness ratio (approximately h/σ ≥ 3), the combined influence becomes weaker, hence ignored. Therefore, the above-said combined effect similar to the one from Gaussian surface circumstances ought to be considered in flow factor analyses and their applications.
Non-linear adaptive control of a linear-motor-driven X—Y table via estimating friction and ripple forces
Authors: Huh K , Han S , Lee B
Published: July 2008

The linear motors are easily affected by load disturbance, ripple force, friction, and parameter variations because there is no mechanical transmission to reduce the effects of external disturbance. For high-speed/high-accuracy position control of a linear-motor-driven X—Y table, a non-linear adaptive controller including a cross-coupling algorithm is proposed in this paper. The non-linear effects such as friction and ripple force are estimated and compensated. The cross-coupling algorithm is adopted to reduce the contour error of the two-axial system. The performance of the proposed controller is evaluated through the computer simulations and experiments.
Static analysis of an anisotropic laminated cylindrical shell with piezoelectric layers using differential quadrature method
Authors: Alibeigloo A
Published: July 2008

A three-dimensional solution is presented for the static analysis of an anisotropic laminated cylindrical shell embedded in piezoelectric layers with arbitrary conditions at the ends, using the differential quadrature method (DQM). With the Soong assumption, governing equations are reduced to differential equations with constant coefficients. By applying the DQM to the obtained governing differential equations and to the boundary conditions along the longitudinal direction, new state equations for state variables are derived at discrete points. Stress, displacement, and electric potential distributions are obtained by solving these state equations. Both direct and inverse piezoelectric effects are investigated, and the influence of piezoelectric layers on the mechanical behaviour of the shell is studied. The method is validated by comparing the numerical results for the shell with the simply supported edges, which can be solved analytically.
Novel method for detecting the non-linear components in periodic structures
Authors: Peng Z K , Lang Z Q , Billings S A
Published: July 2008

Many real-life systems can be modelled as a periodic structure which is constituted by repeating identical systems which are called elements. The periodic structures have drawn extensive attentions from researchers and engineers. In this study, based on the concept non-linear output frequency response function, a novel method is developed to detect the position of non-linear components in periodic structures. The validity of this method is demonstrated by numerical studies. Although the method assumes that the linear stiffness and damping for multi-degree-of-freedom (MDOF) systems under study are known a priori, the results of the numerical studies indicate that, even if only approximate values of the linear stiffness and damping parameters are used, the method can still correctly detect the position of the non-linear component. Since the position of a non-linear component often corresponds to the location of a defect in a periodic structure, this new method is of great practical significance for fault diagnosis in mechanical and structural systems. Moreover, the method does not involve complicated procedure and can be readily applied in practice.
Air jet cooling of brake discs
Authors: Lyons O F P , Murray D B , Torrance A A
Published: July 2008

This paper reports on an investigation of a novel approach to the cooling of brake discs, based on the application of impinging air jets. This has the capacity to enhance the heat transfer coefficients at the disc surface quite considerably without affecting the disc design, so that the disc construction may then be optimized without reference to heat transfer. Using a purpose built test-rig, disc temperature histories were recorded using infrared thermography for varying jet air flowrates, angle of impingement, dimensionless distance from the brake disc, and rotational speed. As well as comparing cooling effectiveness for different test parameters, convective heat transfer coefficients were calculated from the transient temperature data and were used as boundary conditions for a finite-element model of the process. The results obtained from this investigation suggest that the higher convection coefficients achieved with jet cooling will not only reduce the maximum temperature in the braking cycle but will reduce thermal gradients, since heat will be removed faster from hotter parts of the disc. Jet cooling should, therefore, be effective to reduce the risk of hot spot formation and associated disc distortion.
Dynamic analysis using finite elements to calculate the critical wear section of the contact wire in suburban railway overhead conductor rails
Authors: Gonzalez F J , Chover J A , Suarez B , Vazquez M
Published: July 2008

The purpose of this study is to determine the critical wear levels of the contact wire of the catenary on metropolitan lines. The study has focussed on the zones of contact wire where localized wear is produced, normally associated with the appearance of electric arcs. To this end, a finite element model has been developed to study the dynamics of pantograph—catenary interaction. The model includes a zone of localized wear and a singularity in the contact wire in order to simulate the worst case scenario from the point of view of stresses.

In order to consider the different stages in the wire wear process, different depths and widths of the localized wear zone were defined. The results of the dynamic simulations performed for each stage of wear let the area of the minimum resistant section of the contact wire be determined for which stresses are greater than the allowable stress.

The maximum tensile stress reached in the contact wire shows a clear sensitivity to the size of the local wear zone, defined by its width and depth. In this way, if the wear measurements taken with an overhead line-recording vehicle are analysed, it will be possible to calculate the potential breakage risk of the wire. A strong dependence of the tensile forces of the contact wire has also been observed. These results will allow priorities to be set for replacing the most critical sections of wire, thereby making maintenance much more efficient.

The results obtained show that the wire replacement criteria currently borne in mind have turned out to be appropriate, although in some wear scenarios these criteria could be adjusted even more, and so prolong the life cycle of the contact wire.
Wear of pantograph collector strips
Authors: Shing A W C , Wong P P L
Published: July 2008

The overhead conductor system (OCS) could be one of the most economical and feasible engineering solutions to the problem of how to transmit electrical energy to intercity trains (typically at 25 kV AC) or urban/suburban trains (typically at 1.5 kV DC) along open or tunnel routes. However, the consumption of contact wire and collector strips due to wear and tear could impose a severe cost on the railway operator should the interaction between the wear couple formed by the OCS and the pantograph be poor. Following the completion of several OCS improvement projects, this paper examines the factors that might have led to higher than expected consumption of collector strips by analysing statistical data from an operational railway. The observations so far are that irregular contact wire height relative to the rails and high ambient humidity have been identified as two of the many factors that led to the abnormal consumption of collector strips.
Experimental identification and characterization of the effects of contaminants in the wheel—rail contact
Authors: Descartes S , Desrayaud C , Berthier Y
Published: July 2008

Previous results have highlighted the presence of a natural third body ranging in thickness from a few micrometres to several dozen micrometres on the rail and wheel. The third body layer, initially composed of particles stemming from the wheels and rails, flows into the contact to accommodate local sliding inside it. The work presented in this paper focuses on the identification of contaminants whose influence on the wheel—rail contact is significant. This influence can be considered as significant if it enters the contact, affects surface properties, modifies the third body layer, and possibly damages or protects the rail. The third body layer can progressively absorb and assimilate solid (ballast stone, sand) and fluid (oil) contaminants existing on rails, and thus reduce their negative consequences on rail lifetime. These phenomena are the result of the exchange of third body flows between the wheel and rail.

A high-speed camera was used for this experimental study performed on a real site. The analyses of the dynamic images are coupled with tribological analyses of the surfaces by scanning electron microscopy and X-ray energy dispersive analysis.
Overview of coupling noise prediction for turbofans with engine and aircraft performance
Authors: Pascovici D S , Sorato S , Ogaji S O T , Pilidis P
Published: July 2008

In this work, a comparison of the noise levels of different aero-engines is presented. The coupling is based on integrating a gas turbine design and performance model with an aircraft model for long and short hauls and a noise model made of established empirical methods available in the open literature for turbofan noise prediction at design and off-design points. After joining together the performance models with the noise methods, the authors have studied three ultra high bypass ratio engine configurations vis-à-vis their baseline counterpart of equivalent thrust rating. Also, the effect of application of passive noise attenuators (liners) to reduce the noise is explored. The results obtained showed that though there are derivable benefits from the ultra high bypass ratio turbofans, such as reduction in fuel consumption, in jet noise and reduction of broadband noise for the fan, the new engines generate higher noise at lower frequencies in the fan.
Preliminary design analysis of a lightweight combat aircraft
Authors: Saha U K , Mitra M , Menon S J , John N T , Gajapathi S S , Behera P
Published: July 2008

This paper presents a thermodynamical and aerodynamical analyses of the behaviour of a hypothetical lightweight combat aircraft operating on a single engine afterburning turbojet. An airframe was selected for the aircraft thus specifying the aerodynamical characteristics. Then an engine was developed to achieve the basic criteria for the fulfillment of certain predefined mission requirements such as taking off from a runway of specified length, supercruising at particular Mach number, performing high g combat turns, etc. The engine and the airframe were coupled to form a basic aircraft. The capabilities of this aircraft were reviewed thereafter at distinct stages of flight and its capability as an interceptor aircraft was analysed. After careful consideration of all the aspects of the theoretical aircraft, it was concluded that it fulfilled the numerous mandatory requirements demanded for an interceptor aircraft.
Blade tip timing and strain gauge correlation on compressor blades
Authors: Knappett D , Garcia J
Published: July 2008

Traditionally, rotor blade vibration response measurements have been made using strain gauges. Rolls-Royce has a long experience of using strain gauge measurements to certify blades. In recent years, however, much effort has been invested in developing blade tip timing (BTT). The Rolls-Royce BTT system uses casing-mounted laser spot probes to measure the arrival times of the blade set. The vibration amplitudes of the blades are then inferred from these arrival times. BTT offers operational advantages over strain gauges and can measure every blade in the set. Previous back-to-back comparisons of strain gauges and tip timing have shown that both measurement systems measure the same trends in the data. However, initial analysis on a compressor rig showed that the two systems measured different response levels on the blades. This paper shows that both systems can be used with the finite-element model (FEM) to calculate the same amplitude-frequency level on the blade. This is provided that certain assumptions about the behaviour of the blades are true and that the uncertainties within both measurement systems are considered. The paper also presents a novel way of reporting the data to give a visual display of the quality of the data.
Morphology of subsonic rectangular slot jets
Authors: Srinivasan K , Rathakrishnan E
Published: July 2008

This study is motivated by the fact that studies on compressible subsonic rectangular jets are scarce in the literature. Therefore, experiments have been conducted on rectangular jets of aspect ratios 1, 2, 4, and 6, at Mach 0.4 and 1.0. Another highlight of this study is that slots have been used as jet devices rather than nozzles in order to eliminate azimuthal variations of boundary layer growth in the jet device. The flow is characterized in terms of centreline velocity, jet spread, cross-sectional structure, and entrainment behaviour. Results favour the use of low aspect ratio rectangular jets for mixing enhancement.
Analytical solution of short guided orthotropic composite columns under eccentric loading using displacement potential formulation
Authors: Deb Nath S K , Reaz Ahmed S
Published: July 2008

In this paper, short guided columns of orthotropic composite materials are considered in order to analyse their elastic field due to an eccentric compressive loading. The supporting edge of the column is rigidly fixed and fibres are directed along the axis of the column. By a new approach of displacement potential formulation, the present mixed boundary value elastic problem is expressed in terms of a single potential function. Displacement and stress components are derived into infinite series using Fourier integral with the coincided boundary conditions along with the physical boundary conditions. Some numerical results of different stress and displacement components at different sections of the column are presented in the form of graphs. The effect of column aspect ratio and material orthotropy on the solution of stresses and displacements at a particular section is also analysed. Finally, analytical results obtained by the present formulation are compared to those of finite-element and finite-difference methods.
Mechanical and electrical engineering aspects of long-distance underground power transmission
Authors: Kotsikos G , Hale J , Jack A , Gibson A G
Published: July 2008

The delivery of the power from remote power generation sites to urban centres is increasingly becoming a challenge for the power industry since the use of traditional power transmission technology, such as overhead cables, is a politically sensitive issue and alternative approaches are sought. This paper reports the findings of a feasibility study into long distance power transmission via small diameter underground tunnels, constructed using trenchless technologies such as horizontal directional drilling or microtunnelling. The study examines the suitability of AC or DC transmission for such underground tunnels, various cooling methods to remove the heat generated in the conductors from electrical losses, type of conductor to be used, and issues concerning conductor installation. As a result of this study a number of technical challenges have been identified that need to be overcome in order to make the method an economically and technically viable option.
Real-time reliability index of a steam power plant: A systems approach
Authors: Mohan M , Gandhi O P , Agrawal V P
Published: July 2008

The present system of reporting reliability (also known as product performance) of a power generating plant on annualized basis has failed to serve the plant managers to take technocommercial decisions. Moreover, these indices show a wide variance depending upon the method of selection by the peer group for indexing purposes. For assessing reliability, a model has been developed for a steam power plant (SPP) in this paper using a systems approach of graph theory in conjunction with matrix method. A concept of real-time reliability index (RTRI) of the SPP has also been proposed, which overcomes the problems associated with the selection of a peer group for comparison. The value of RTRI indicates the probability of complete shut down or operation of the SPP at partial load.

For finding the reliability of a SPP in real-time, its system structure graph (SSG), variable permanent system structure matrix and variable permanent function (VPF-s) have been converted into the corresponding reliability graph, matrix, and variable permanent function (VPF-r), respectively by associating reliability attribute to the nodes (S i) and the edges (c ij) of the SSG. When all the equipment, subsystems in different systems (S i) of a SPP are performing as per design specifications, the corresponding value of the VPF-r is termed as VPF-r design. Under real-time operation when, some of the equipment/subsystem of a particular system(s) may not be available or not performing at the designed level; the corresponding value of VPF-r is different from its design value and is termed as VPF-r real-time and the ratio of the real-time-value to the design value is the RTRI value. The proposed model is capable of taking real-time situations of various systems of the SPP simultaneously. A step-by-step procedure for calculation of RTRI has been suggested and also been illustrated by means of an example.
Investigation of the oil—gas separation in a horizontal separator for oil-injected compressor units
Authors: Feng J , Chang Y , Peng X , Qu Z
Published: July 2008

This article presents an investigation of the separation process as well as the separation efficiency for a horizontal oil—gas separator, which is widely used in the oil-injected compressor units. The trajectories of oil droplets with different diameters in the separator were simulated by using the discrete phase model in combination with the gas flow model. The laser diffraction technique (Malvern) was applied to measure the oil concentration and thereby the separation efficiency. By varying the parameters such as the oil injection flowrate, compressor discharge pressure, and oil—gas mixture inlet velocity, the main factors influencing the separation efficiency were identified. The results indicate that the trajectories together with the residence time of the oil droplets in the separator vary significantly with the droplet sizes. The separation efficiency increases from 99.81 to 99.93 per cent as the oil injection flowrate rises from 567 to 1182 l/h. An optimal discharge pressure exists for the separation efficiency, and the highest separation efficiency was obtained at a discharge pressure of 0.65 MPa. The simulated minimum oil droplet that can be separated completely during the first step separation is ∼17 μ m, which has a good agreement with the measured data of 17.7–20.5 μ m.
Particle image velocimetry investigation of the flow field in a centrifugal impeller with unequally spaced blades
Authors: Wu Y-D , Ouyang H , Tian J , Du Z-H
Published: July 2008

The characteristics of flow in a centrifugal impeller with different stagger angle along the blade span and unequally spaced blades were investigated using particle image velocimetry (PIV). Instantaneous and averaged velocity measurements were carried out at the inlet, outlet, inside blade passage, around blade, and around scroll of the centrifugal impeller by synchronizing the passage of the blade with laser and camera system. These measurements revealed detailed flow features at the operating point of the centrifugal impeller with and without scroll. The data from the PIV measurements were used to analyse the performance of the centrifugal impeller.
A low-speed generator for energy conversion from marine currents — experimental validation of simulations
Authors: Thomas K , Grabbe M , Yuen K , Leijon M
Published: July 2008

A low-speed permanent magnet (PM) cable wound generator for electrical energy conversion from marine or tidal currents has been designed and constructed. A key feature of this variable speed direct drive generator is its capability to efficiently generate electricity from tidal currents with very low velocities, in the order of 1 m/s. In arriving at an appropriate design for the generator typical characteristics of tidal currents were considered. Using these characteristics as input, and accounting for the electromagnetic losses, detailed computer simulations using a finite-element method software were carried out to come up with the final design. Various parameters that can influence the generator design are presented. An experimental set-up has been constructed based on the above-mentioned design in order to study the electrical and mechanical performance of the generator through a variety of experiments. The power input for this set-up is a variable speed motor, capable of operating the generator at rotational speeds of 0–16 r/min, representing tidal currents with very low velocities. The generator presented in this paper may be beneficial for a better understanding of an appropriate design and layout of tidal energy conversion systems.
Effects of Fe powder on sliding wear processes under lubricants with different viscosities
Authors: Yuan C Q , Yan X P , Zhou X C
Published: July 2008

Four sliding wear tests were conducted using a ball-on-disc tester at room temperature to investigate sliding wear processes in which Fe powders were added to the lubricant. The ball sample was a standard E52100 ball of 8 mm in diameter. The disc samples were made of 5140 steel and heat-treated to a hardness of 52 HRC. Wear debris analysis and surface analysis of the tested samples were carried out to investigate the wear particles generated from the wear process and to study the effects of the soft Fe powder. It was proved that Fe powders in the lubricant played an important role in the wear process and had a significant effect on the main wear mechanisms, resulting in wear-out failure.
Sliding wear performance of high-velocity oxy-fuel spray Al2O3/TiO2 and Cr2O3 coatings
Authors: Singh H , Grewal M S , Sekhon H S , Rao R G
Published: July 2008

High-velocity oxy-fuel (HVOF) spray ceramic oxide coatings have immense potential in industrial applications. However, they are not widely used yet due to the lack of an adequate scientific database created after testing these coatings for specific industrial applications. Two such ceramic coating powders, Al2O3+(40%)TiO2 and Cr2O3, were deposited on AISI 309 SS stainless steel by the HVOF spray technique, in order to enhance its wear resistance. This stainless steel is used in many components of thermal power plants in India, where it suffers one or more types of wear. The as-sprayed coatings were characterized by XRD and SEM analyses. Subsequently, the sliding wear behaviours of the uncoated, HVOF spray Al2O3+(40%)TiO2 and Cr2O3 coated AISI 309 SS were investigated according to ASTM standard G99-03 on a pin-on-disc wear test rig. Cumulative wear rate and coefficient of friction (μ) were calculated for the coated as well as the uncoated specimens for 30, 50, and 70 N normal loads at a constant sliding velocity of 1 m/s. Some of the worn-out surfaces were characterized by SEM analysis. Both the as-sprayed coatings exhibited typical splat morphology of a thermal spray process. The XRD analysis indicated the formation of Al2O3 and TiO2 phases for the Al2O3+(40%)TiO2 coating, and Cr2O3 phase for the Cr2O3 coating. It has been concluded that HVOF spray Al2O3+(40%)TiO2 and Cr2O3 coatings can be useful in minimizing the wear problem of AISI 309 SS. These coatings were found to be successful in retaining their surface contact with the substrate after the wear tests. The HVOF spray Cr2O3 coating can be recommended as a slightly better choice to reduce the wear of AISI 309 SS in comparison with the Al2O3+(40%)TiO2 coating.
Oil consumption studies in a single-cylinder diesel engine using solid-film lubricants
Authors: Perez P L , Boehman A L , Perez J M
Published: July 2008

Solid-film additives (tungsten disulfide, lead sulfide, and graphite fluoride) were dispersed in a high temperature liquid lubricant, and their performance was evaluated in a single-cylinder diesel engine. Oil consumption and wear of the piston and rings were determined during the tests, and changes in oil properties such as viscosity and total acid number (TAN) were monitored as well. Tungsten disulfide and lead sulfide proved to be effective additives to reduce friction and wear under the operational conditions encountered in the diesel engine. This contrasted with the behaviour of graphite fluoride, which produced high friction and wear. The observed oil consumption correlated with degradation rates of the solid-film additive dispersions as indicated by the TAN, although high abrasion was also observed in the case of graphite fluoride. The use of solid-film additives had no effect on the brake-specific fuel consumption with respect to the reference baseline oil.
Combined effects of non-Newtonian rheology and rotational inertia on the squeeze film characteristics of parallel circular discs
Authors: Lin J-R , Hung C R
Published: July 2008

The combined effects of non-Newtonian couple stresses and rotational inertia on the squeeze film behaviours between parallel rotating circular discs have been analysed in this paper. On the basis of Stokes micro-continuum theory, the non-Newtonian Reynolds-type equation including the rotational inertial effects is derived, and applied to predict the squeeze film performance. According to the results obtained and discussed, the effects of rotational inertia yield a lower squeeze-film load-carrying capacity; however, the presence of non-Newtonian couple stresses provides an increase in the load-carrying capacity and the approaching time. Better squeeze film characteristics of rotating circular discs are achieved by the use of a non-Newtonian couple stress fluid.
Passive non-linear targeted energy transfer and its applications to vibration absorption: A review
Authors: Lee Y S , Vakakis A F , Bergman L A , McFarland D M , Kerschen G , Nucera F , Tsakirtzis S , Panagopoulos P N
Published: July 2008

This review paper discusses recent efforts to passively move unwanted energy from a primary structure to a local essentially non-linear attachment (termed a non-linear energy sink) by utilizing targeted energy transfer (TET) (or non-linear energy pumping). First, fundamental theoretical aspects of TET will be discussed, including the essentially non-linear governing dynamical mechanisms for TET. Then, results of experimental studies that validate the TET phenomenon will be presented. Finally, some current engineering applications of TET will be discussed. The concept of TET may be regarded as contrary to current common engineering practise, which generally views non-linearities in engineering systems as either unwanted or, at most, as small perturbations of linear behaviour. Essentially non-linear stiffness elements are intentionally introduced in the design that give rise to new dynamical phenomena that are very beneficial to the design objectives and have no counterparts in linear theory. Care, of course, is taken to avoid some of the unwanted dynamic effects that such elements may introduce, such as chaotic responses or other responses that are contrary to the design objectives.
Automatic path control based on integrated steering and external yaw-moment control
Authors: Goodarzi A , Sabooteh A , Esmailzadeh E
Published: July 2008

Nowadays improving safety is an indispensable part of research issues in the automotive industry. Due to increased travelling time, accident potentials and also traffic congestions, automated vehicles are seen as a way to increase freeway capacity and vehicle speed while reducing accidents resulted from human errors. In order to guide a vehicle automatically, vehicle lateral motion should be controlled, active steering control (ASC) and direct yaw-moment control (DYC) are two common methods to control the vehicle lateral dynamic, automatically. For higher vehicle lateral acceleration, where the tyres will not be capable of producing enough lateral forces (yaw-moment), ASC could not be useful. In such situation, the advantages of DYC can be clearly observed.

Indent In this paper, a novel optimal control law is proposed to control the vehicle path, automatically. The control law uses the vehicle dynamic variables such as the yaw and lateral velocities, lateral offset, and the heading error as well as the road-related variables. These are the road curvature and the lateral offset between the desired path and the vehicle as the feedback/feed-forward signals to produce both the front steering angle and the external yaw-moment signals as the control efforts. Simulation results illustrate the dominant power of the front steering/DYC in the control of the vehicle lateral motion.
Analysis of torsional vibration in internal combustion engines: Modelling and experimental validation
Authors: Mendes A S , Meirelles P S , Zampieri D E
Published: July 2008

This paper reports on a study of the crankshaft torsional vibration phenomenon in internal combustion engines. The steady state of the state equation is solved by the transition state matrix and the convolution integral. This formulation is applied to the model of a six-cylinder diesel engine manufactured by MWM International Motores®. The analyses consider a rubber and viscous damper assembled to the crankshaft front-end. An analysis of the torsional vibrations indicates the dynamic loading on each crankshaft section, and these loads can be applied as boundary conditions in a finite element model to predict the safety factor of the component and to compare the system's behaviour with rubber and viscous damper options. This study highlights the importance of torsional vibration analyses in the structural dimensioning of crankshafts. The results of the torsional vibration amplitude are compared with measured values to experimentally validate the proposed mathematical model.
Kinematic design and multi-body analysis of Rzeppa pilot-lever joint
Authors: Pennestrì E , Valentini P P
Published: July 2008

Rzeppa pilot-lever joint represents a classical solution to the problem of transmitting torque between angularly misaligned shafts. Homokineticity is one of the most important requirement in industrial applications. The Myard's theorem gives the geometrical conditions which ensure the satisfaction of such requirement. In this paper, two different original proofs of this theorem are offered.

An algorithm for the optimal kinematic synthesis of the pilot-lever mechanism is then proposed. The pilot-lever mechanism is designed to minimize the maximum angle between the transmission and the homokinetic plane.

Finally, a multi-body dynamic analysis of the Rzeppa pilot-lever joint is made by means of a commercial software. The modelling of contact conditions between the balls and the guides is discussed in particular. Finally, the contact forces between spheres and guides for different angles between input and output shafts are computed.
Reconfiguring the Pre-Trial and Trial Processes in Ireland in the Fight against Organised Crime
Authors: Campbell Liz
Published: July 2008

This article describes and analyses the changes which have occurred to pre-trial detention and interrogation and to the trial process in Ireland as a result of the apparent threat posed by organised criminality. The templates for these measures often derive from extraordinary tactics first used against subversive paramilitary groups. However, while incursions have been made on protective procedural rights and rules, important safeguards remain which counterbalance such trends.
Characterisation of fines from unbleached kraft pulps and their impact on sheet properties
Authors: Bäckström Marie , Kolar Marie-Claude , Htun Myat
Published: July 2008

Fines are an essential component in the papermaking process because they have a profound influence on the behaviour of the wet web and on the mechanical properties of the final sheet. Primary fines are present in the pulp prior to refining, and secondary fines are produced during refining. In the present investigation, two commercially manufactured unbleached pulps with kappa numbers of 45 and 90 were studied in terms of how they responded to refining with respect to the quality of fibre and fines. Primary and secondary fines were collected and characterised and their impact on sheet strength was evaluated by addition of known amounts to a refined and decrilled pulp. All the measured paper strength properties improved when primary and secondary fines were added. The strength improvement was generally somewhat higher in the second case. The effect was more pronounced at a higher level of addition. We attribute the main strength improvements associated with fines to improved consolidation by the creation of capillary forces between the surfaces.
Fiberboard bending properties as a function of density, thickness, resin, and moisture content
Authors: Hunt John F. , O'Dell Jane , Turk Chris
Published: July 2008

Fibers from treetop residues of lodgepole pine (Pinus contorta) and recycled old corrugated containers were used to fabricate wet-formed fiberboard panels over a range of densities from 300 to 1100 kg m-3, a thickness range from 1.3 to 4.8 mm, and phenolic resin contents from 0% to 4.5%. The panels were then tested after conditioning in 50% and 90% relative humidity (RH) environments. Density, thickness, equilibrium moisture content, bending modulus of elasticity (MOE), and modulus of rupture (MOR) were measured for each panel. Panel apparent-density increased with thickness, but this may be due to surface effects rather than true density values. The equilibrium moisture content approximately doubled for the panels in the 90% RH environment, compared to 50% RH. At 50% and 90% RH conditions, equilibrium moisture contents decreased significantly when only 0.5% resin was added and remained essentially the same with increasing resin levels. In this study, both MOE and MOR increased with approximately the square of density. MOE increased, whereas MOR showed no clear effects as thickness and resin amount increased. This research is part of a larger program for developing an understanding of panel properties for engineered three-dimensional fiberboard products.
Significance of the heating rate on the physical properties of carbonized maple wood
Authors: Xie Xinfeng , Goodell Barry , Qian Yuhui , Peterson Michael , Jellison Jody
Published: July 2008

Effects of the heating rate on the physical properties of carbonized wood were investigated by comparing the dimensional shrinkage, electrical resistivity, Young's modulus, and the evolution of turbostratic crystallites in maple hardwood samples carbonized at 600°C, 800°C, and 1000°C under heating regimes of 3°C h-1 and 60°C h-1. Important carbonized wood properties that developed at high temperature and high heating rates could also be produced at slow heating rates and lower temperatures. Furthermore, slow heating rates promoted the formation and growth of graphene sheets in turbostratic crystallites, which had a significant influence on the electrical resistivity and Young's modulus of the carbonized wood. The results indicate that the graphene sheets of turbostratic crystallites formed during wood carbonization were arranged parallel to the axial direction of wood cells and at an angle to the circumference of wood cells in the cross-sectional plane. With regard to the production of carbon products, a decrease in the heating rate may be beneficial for char properties and the prevention of crack production during manufacture of large monolithic carbon specimens from wood and wood-based materials.
Studies on the dehydrogenative polymerizations (DHPs) of monolignol β-glycosides: Part 4. Horseradish peroxidase-catalyzed copolymerization of isoconiferin and isosyringin
Authors: Tobimatsu Yuki , Takano Toshiyuki , Kamitakahara Hiroshi , Nakatsubo Fumiaki
Published: July 2008

Horseradish peroxidase (HRP)-catalyzed dehydrogenative copolymerization of guaiacyl (G)-type monolignol glycoside (isoconiferin, coniferyl alcohol γ-O-β-d-glucopyranoside, iso-G) and syringyl (S)-type monolignol glycoside (isosyringin, sinapyl alcohol γ-O-β-d-glucopyranoside, iso-S) were performed in continuous dehydrogenation mode (end-wise polymerization) to result in the formation of water-soluble lignin-like copolymers (iso-G/S-DHPs) in a homogeneous phase. The yield of iso-G/S-DHP increased with increasing iso-G content in the mixture of monomers from 23% (iso-G/iso-S 0:100) to 81% (iso-G/iso-S 50:50). The degree of polymerization (DP) of the resulting iso-G/S-DHP also increased proportionally from 7 (iso-G/iso-S 0:100) to 27 (iso-G/iso-S 50:50) as the iso-G content increased. It is obvious that iso-G plays an important role in the polymerization of iso-S. A similar tendency was also observed in conventional copolymerization of coniferyl alcohol (G-alc) and sinapyl alcohol (S-alc). The highest DP for DHP obtained in the conventional system was only ∼10 due to the heterogeneous reaction system. As the HRP-catalyzed monomer consumption rate of iso-S was greatly enhanced by addition of iso-G as a co-monomer, radical transfer from iso-G to iso-S seems to be plausible. Conventional copolymerization of G-alc and S-alc also supports this view. Spectroscopic studies and alkaline nitrobenzene oxidation analyses indicated that iso-G/S-DHPs had typical lignin structures composed of both G and S units. It was confirmed that the copolymerization behavior of the glycosides iso-G and iso-S in a homogeneous phase are well reflected by that of the monolignols G-alc and S-alc in a heterogeneous phase. Results also indicated that the presence of G-type co-monomers sensitively affects the polymerization of S-type monomers.