bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of through-thickness residual stress by numerical and experimental techniques
Authors: Rasouli Yazdi S , Retraint D , Lu J 
Published: October 2002

The quenching process of aluminium alloys is modelled using the finite element method. The study of residual stress field induced by quenching is divided into two: the thermal and mechanical aspects. In the thermal problem, the general heat conduction equation is solved and the temperature field during quenching is calculated. In the mechanical problem, the calculated temperature field and mechanical properties are used to predict the residual stress field. In this paper, the two different boundary conditions used in the thermal problem are examined. The first is surface convection using the appropriate heat transfer coefficient. The second is the temperature variation measured at the surface of the part. These boundary conditions are compared, and the advantages and the drawbacks of each are shown. The influence of different quenching parameters on the level of residual stress is studied. To validate the quenching modelling, the incremental hole drilling and neutron diffraction methods are used to measure the residual stress field in the studied parts. The hole drilling technique has been adapted to measure the residual stress through a larger thickness of the part. The aim of this paper is the combination of numerical and experimental techniques for the investigation of the through-thickness residual stress field.
Overcut in pulsed electrochemical grinding
Authors: Tehrani A Fadaie , Atkinson J 
Published: October 2002

The electrochemical grinding (ECG) process offers a number of advantages over conventional grinding, such as low induced stresses, large depths of cut, increased wheel life and the ability to machine delicate workpieces. However, one disadvantage is the difficulty of controlling the dimensional accuracy of the workpiece. In the present work the use of pulsed voltage in ECG is investigated for two workpiece materials, AISI 01 tool and die steel and stainless steel 304. The effect on resulting workpiece dimensional accuracy is assessed in terms of repeatability of overcut. Under conditions where an overcut of 0.03 mm is expected in conventional ECG, a reduction to zero overcut has been obtained by appropriately pulsing the applied voltage. The ranges of such operating conditions have been quantified for the two materials. Further, it is seen that, under finishing conditions appropriate to obtaining mechanical abrasive contribution at the final workpiece surface, a repeatability within 0.010 mm is possible. Repeatability deteriorates to 0.018 mm when electrochemical dissolution is the dominant contributor to metal removal. Pulsed ECG is found to be a convenient means of adjusting operating conditions to control overcut and its repeatability.
Using stereolithography tools for injection moulding: Research into tensile tool failure and unexpected benefits of the process
Authors: Hopkinson N , Dickens P M 
Published: October 2002

The use of stereolithography (SL) parts as injection moulding tools offers many advantages over traditional tool making approaches. In particular, the time required to convert a computer aided design (CAD) file to the final tool is dramatically reduced as may be the costs in creating the tool. However, the process has been perceived to have a number of drawbacks which are, in the main, associated with the poor thermal and mechanical properties of the SL resins. Research was performed which involved the production and use of an SL tool to injection mould a series of parts in polypropylene. Measurements were made of the forces required to eject parts from the tool in order to assess the possibility of tensile tool failure during part ejection. The measured forces were compared with predicted values which had been calculated using previously devised equations. In addition, temperatures were recorded throughout the injection moulding cycle to assess the tool's strength at different times. Surface roughness measurements were also taken to characterize the ejection process more closely and observe any changes to surface roughness caused by moulding parts. A finite element analysis was made of the heat transfer in the tool to help with prediction of ejection forces. Measurements of ejection forces and heat transfer indicated that, contrary to existing recommendations, part ejection should be performed shortly after injection. Accurate predictions of ejection force were shown to be unattainable given the difficulty in finding accurate values for the variables used in the force prediction equations. Measurements of heat transfer coupled with surface roughness suggested that the low thermal properties of SL tools actually work in favour of the process rather than against it. This conceptual about-turn regarding the role of thermal properties in SL injection moulding tools indicates that further benefits may be derived from the new technology.
Selection of mould design variables in direct stereolithography injection mould tooling
Authors: Harris R A , Newlyn H A , Dickens P M 
Published: October 2002

Stereolithography (SL) can be used rapidly to produce injection moulding tools. The disadvantage of the technique is that it is capable of producing only a small number of parts before failure. Stereolithography tools may break under the force exerted by part ejection when the friction between a moulding and a feature of the tool is greater than the tensile strength of the tool, resulting in tensile failure. Very few justified recommendations exist concerning the choice of mould design variables that can lower the part ejection force experienced and reduce the risk of SL tool failure. This research investigates the ejection forces resulting from the injection moulding of polypropylene (PP), acrylonitrile-butadiene-styrene (ABS) and polyamide 66 (PA66) parts from SL tools that are identical in all respects except for their build layer thickness (a process variable when generating the SL tooling cavities) and incorporated draft angles (a tooling design variable). This work attempts to identify appropriate evidence for recommendations with respect to these variables and SL injection moulding. The results show that linear adjustment of draft angle results in a fairly minor linear change in part ejection force according to the moulding material. A linear adjustment of the build layer thickness results in a greater change in part ejection force as a more non-linear relationship. In both cases the greatest ejection forces were experienced by PA66, then ABS and then the PP parts. The results also show that the surface roughness of all tools remains unchanged after moulding a number of parts in all polymers. A mathematical model was used in an attempt to predict ejection forces according to the moulding material used. This model did reflect the experimental results in terms of relative values but not in absolute values, which may be due to the limitations imposed by the development of the expressions and uncertainty about some specific values.
Implementing a model-based generic user interface for computer integrated manufacturing systems
Authors: Monfared R P , Hodgson A , Bowen B A , West A A 
Published: October 2002

Computer integrated manufacturing (CIM) systems are complex in terms of performing a variety of activities, maintaining a range of information and involving various classes of users with differing levels of knowledge and skills, and different levels and time spans of decision making. Much investment and effort has been made to formalize and automate the performance of the CIM elements in a manufacturing system. However, each CIM subsystem will typically have its own terminology, procedures and presentation formats. This places a heavy and unnecessary burden on users, resulting in frustration and reduced effectiveness. Research has been carried out by the Manufacturing Systems Integration Research Institute at Lough-borough University towards the generation of a user-oriented interface for CIM systems. This research has resulted in a conceptual approach, which incorporates a generic user—task model, which enables the generation of flexible and reusable software components to form a semigeneric user interface for CIM users. The CIM user interface provides presentation tools to monitor and control the performance of the CIM elements. Advanced modelling and integration technologies have been deployed to enable the system to cover a wide area of manufacturing domains. These technologies include modern manufacturing modelling architectures such as CIMOSA and GERAM, and advanced communication techniques such as those used by Web-based software applications in manufacturing environments. The implementation issues of the generic user interface concept, together with its application within an industrial case study are discussed in this paper.
The detrimental effect of non-metallic inclusions during metal forming processes
Authors: Riedel U T , Morgan J E , McMahon C A , Guild F J , Bleck W 
Published: October 2002

The presence of non-metallic inclusions can result in material failure during the metal forming process or lead to a serious deterioration in the quality of the final product. Understanding the effects of inclusions during metal forming is therefore an important step towards predicting the behaviour of inclusions and subsequently minimizing their consequences. To aid this understanding the authors have carried out a finite element (FE) analysis into the effect that metal inclusions have during metal forming, and specifically the effect of non-metallic inclusions in rod drawing [1, 2]. The FE analysis was verified using experiments that simulated the rod drawing process. It is part of the results of these experiments which is briefly described in this paper. An aluminium oxide (Al2O3) sphere was embedded into an axially split rod which was then drawn through a carbide die. The subsequent deformation of the rod around the Al2O3 inclusion was studied. In addition, fracture of the rod, initiated at the inclusion, was observed.
The borderline of elastohydrodynamic and boundary lubrication
Authors: Spikes H 
Published: October 2002

There is a growing trend for lubricated systems to operate for much of their operating life with very thin lubricating films. This paper reviews our current understanding of such films, at the borderline between elastohydrodynamic and boundary lubrication. The nature and properties of these films are very complex, since the proximity of the solid surfaces influences the structure and rheology of thin liquid layers, while boundary films can, themselves, possess rheological characteristics that vary with thickness. Novel experimental tools, such as atomic force microscopy and ultra-thin-film interferometry have greatly accelerated our understanding of this area in the last few years and it has recently become possible to map lubricant film thickness within rough surface contacts. These tools are beginning to provide the level of understanding of thin-film rough surface behaviour required to develop accurate numerical and simulation models. The next 5 years should see a very rapid progression of our understanding of this important regime.
Theoretical modelling of cavitation in piston ring lubrication
Authors: Priest M , Dowson D , Taylor C M 
Published: October 2002

Mathematical models of piston ring dynamics and lubrication are sensitive to the boundary conditions adopted to describe the cavitation occurring in the diverging outlet region of the lubricant film between the piston ring and cylinder wall. In this paper, such sensitivity is investigated by applying different models of gaseous cavitation, flow separation and fluid film reformation to the analysis of a single compression ring from a diesel engine. Significant differences are predicted in hydrodynamic pressure profiles, lubricant film boundaries, lubricant film thickness, oil flow and friction. Such indications of substantial differences in piston ring operating characteristics associated with the distinct cavitation boundary conditions considered highlights the need for further research in this field. However, the lack of detailed experimental data to validate the predictive models suggests that future progress must be based upon combined theoretical and experimental approaches to the problem. It is postulated that boundary conditions based upon Reynolds cavitation and fluid film reformation may be applicable at high loads, and fluid film separation of a form proposed by Coyne and Elrod at low loads.
Gear condition monitoring by a new application of the Kolmogorov—Smirnov test
Authors: Andrade F A , Esat I I , Badi M N M 
Published: October 2002

This paper introduces a new technique for the vibration condition monitoring of a set of spur gears. This technique, the Kolmogorov—Smirnov (KS) test, is based on a statistical comparison of two vibration signatures, which tests the ‘null hypotheses that the cumulative density function (CDF) of a target distribution is statistically similar to the CDF of a reference distribution’. In practice, the KS test is a time-domain signal processing technique that compares two signals and returns the likelihood that the two signals are statistically similar (i.e. have the same probability distribution function). Consequently, by comparing a given vibration signature with a number of template signatures for known gear conditions, it is possible to state which is the most likely condition of the gear under analysis. It must be emphasized that this is not a moment technique as it uses the whole CDF instead of sections of the CDF. In this work, the KS test is applied to the specific problem of direct spur gear condition monitoring. It is shown that this test not only successfully identifies the condition of the gear under analysis (brand new, normal, faulty and worn out), but also gives an indication of the advancement of the crack. Furthermore, this technique identifies cracks that are not identified by popular methods based on the statistical moment and/or time-frequency (TF) analysis and the vibration signature. This shows that, despite its simplicity, the KS test is an extremely powerful method that effectively classifies different vibration signatures, allowing for its safe use as another condition monitoring technique.
Spring damper model of an impact between a tennis ball and racket
Authors: Goodwill S R , Haake S J 
Published: October 2002

A model has been derived that determines the ball, stringbed and racket frame motion for an impact between a tennis ball and racket. This paper describes the model and methods used to verify it experimentally. The model incorporated parameters such as racket mass, moment of inertia and ball stiffness. The work was conducted to produce a tool that could be used to identify the importance of each of the parameters on the impact. The ball was modelled as simple spring and damper in parallel while the stringbed was modelled as a spring in series with the ball. The values of these spring and damper parameters were determined experimentally. It was assumed that the racket frame was a rigid body to simplify the analysis. Two different methods of supporting the racket were modelled, and the balls were always projected perpendicular to the string plane. Firstly, the racket was head-clamped and all the balls impacted at the geometric string centre of the racket. Good agreement was found between the experiment and model data for both ball rebound velocity and maximum stringbed deflection during impact. The second method of support involved freely suspending the racket at the tip on a small pin. Three different impact positions along the longitudinal axis of the racket were tested. Good agreement between the experiment and model data was found for the ball rebound velocity for impacts at the geometric string centre of the racket. The model over-predicted the experimental racket rebound velocity (generally by less than 5 per cent) for all impact positions. A qualitative analysis assigned this small difference to the assumption that the frame was a rigid body and therefore vibration losses were not accounted for.
Application of linear biphasic theory to finite element analysis of head impulse loading
Authors: Park H S , Yoon Y S 
Published: October 2002

A finite element model of the human head by linear biphasic theory is developed to study the dynamic response of the human head to impact. Intracranial tissues are modelled as a binary mixture, i.e. the fluid and solid phases. To validate the biphasic finite element formulation, the result of the numerical analysis of a one-dimensional wave propagation problem is compared with that of analytic solution. The permeabilities of the subarachnoid space and brain which may reproduce the same coup and contre-coup CSF (cerebral spinal fluid) pressures from the monophasic model are searched in the specified range of skull permeability. Then the intracranial pressure distributions from the biphasic model for the frontal impact are compared with those from the monophasic model. In general, the biphasic model produces a more injurious intracranial pressure distribution than the monophasic model. The pressure distribution from the biphasic model shows a little higher contre-coup pressure in the frontal lobe than in the occipital region. This finding is in agreement with those clinical findings that contre-coup injuries are more frequently found in the frontal lobe. Another numerical simulation is conducted to characterize the effect of the volume ratios between two phases in the skull and subarachnoid space. From the results, it can be seen that the variation of the volume ratio in the subarachnoid space affects the intracranial pressure distribution of the lateral part while the variation in the skull does not.
Geometry and kinematics of multicable spreader lifting gear
Authors: Morrish L , Cartmell M P , Taylor A J 
Published: October 2002

This paper presents a novel theoretical study of the geometry and derived kinematics of a typical multicable suspension system as encountered on a rubber tyred gantry (RTG) crane. Machines of this sort are used extensively in the international container handling business but, to date, little has been known about the precise motions of cable suspended spreaders other than general intuitions about fore—aft, lateral and rotational oscillations. Such motions are initiated by driver-controlled motion of the gantry itself (by torques applied to the driving wheels) and by across-the-vehicle motions of the trolley from which the spreader and container payload are suspended. The work reported here shows the complete derivation for spreader coordinates, relative to the trolley, for any translational and/or rotational displacement. Conventional geometrical and trigonometrical principles are used throughout the development. This research forms an integral part of a larger programme of work to propose strategies for accurate spreader motion control based on non-linear dynamic models.
Buckling of curved panels under combined shear and compression
Authors: Featherston C A , Ruiz C 
Published: October 2002

The analytical work which has been carried out to determine the buckling load and post-buckling behaviour of curved panels under various types of loading and different boundary conditions is not as comprehensive as that for flat plates. Only elementary loading and boundary conditions have been analysed. In addition to this, many of the theories developed have not been tested experimentally. This paper outlines a series of tests carried out to determine the accuracy of the theoretical buckling loads. The experimental results are then used to examine whether or not finite element analysis can be used as an alternative to determine collapse loads and post-buckling behaviour, especially in cases where no theoretical solutions exist.
Theoretical investigation into the use of controllable suspensions to minimize road damage
Authors: Kitching K. J. , Cole D. J. , Cebon D 
Published: October 2002

This paper describes a theoretical investigation into the reduction of road damage through use of active and semi-active suspensions. Two new linear state feedback control strategies are described. These regulate aspects of the vehicle response that are believed to be closely related to road damage. Comparisons are made with two established control strategies. The relative performance of the four controllers is examined using a two-axle planar heavy vehicle model, with both active and semi-active suspensions. Significant improvements are predicted for the three control strategies which account for correlation between the road roughness inputs at the front and rear of the vehicle, both for the active and semi-active suspensions. The state feedback preview control strategy previously developed by Sharp and Wilson [1] is found to give the best all-round performance for a suspension with semi-active suspension dampers.
Safety of driver interaction with in-vehicle information systems
Authors: Stevens A 
Published: October 2002

Advances in vehicle instrumentation are driven by customer demand, by the desire of manufacturers to add value and by technology that offers increasingly sophisticated and cost effective options. The range of information and communications equipment available to the driver has grown considerably over the past 5 years. Trip computers and radio data systems (RDS) are now standard on many vehicles, and the use of in-vehicle telephones has also increased. Other driver information products, such as congestion warning and route guidance systems, are becoming increasingly common. Much development of in-vehicle information has, necessarily, focused on getting the technology to work. Now, as products are emerging, the real needs of drivers and their interaction with new systems is receiving much greater attention. The human-machine interface (HMI) is emerging as a key area that has a significant impact on the overall usability and safety of in-vehicle systems. This paper discusses HMI safety and how it is being addressed through standards, codes of practice and design guidelines.
Speciated hydrocarbon emissions from a gas-fuelled spark-ignition engine with various operating parameters
Authors: Kim C. U. , Bae C. S. 
Published: October 2002

For natural gas and liquefied petroleum gas (LPG), measurements of the concentrations of individual exhaust hydrocarbon (HC) species have been made under various engine operating conditions in a 2 litre four-cylinder engine using gas chromatography. Non-methane hydrocarbon (NMHC) in addition to the species of HC and other emissions such as CO2, CO and NOx were examined for natural gas and LPG at 1800 r/min for two compression ratios (8.6 and 10.6), various brake mean effective pressure (b.m.e.p.) values (250-800 kPa), spark timings (before top dead centre 10°-55°) and exhaust gas recirculation ratios up to 7 per cent. Fuel conversion efficiencies were also investigated together with emissions to study the effect of engine parameters on the combustion performance in gas engines, especially under the lean burn conditions. It was found that CO2 emission decreased with smaller C value of fuel, leaner mixture strength, higher compression ratio, higher b.m.e.p. and the ignition near the maximum brake torque spark timing. HC emissions from the LPG engine consisted primarily of propane (C3 H8) (more than 60 per cent), ethylene and propylene (C3 H6), while the main emissions from natural gas were methane (more than 60 per cent), ethane, ethylene and propane. Natural gas was shown to have less of a tendency to form ozone than LPG. This was accomplished by reducing the emissions of propylene, which has a relatively high maximum incremental reactivity factor, and propane, which forms a large portion of LPG. In addition, natural gas shows a benefit in the other emissions (i.e. NMHC, NOx and CO2), specific reactivity and brake specific reactivity values except fuel conversion efficiency.