bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparison of Two-Dimensional and Three-Dimensional Hydroelasticity Theories Including the Effect of Slamming
Authors: Aksu S , Price W G , Temarel P 
Published: February 2007

The behaviour of slender and non-slender flexible bodies travelling in irregular seaways is examined. This is achieved by using a two-dimensional (2D) and a three-dimensional (3D) theory. These theories are based on different assumptions and mathematical models, though both are capable of assessing the influence of transient loadings caused by slamming. The two-dimensional theory is restricted to steady state and transient vertical responses (motion, distortion, bending moment, shear force) in irregular head waves, whereas the three-dimensional theory allows calculations of both vertical responses and transverse responses (motion, distortion, bending moment, shear force, twist) in head and oblique waves. Time-domain simulations of the responses (steady state and transient) are generated from which statistical data are determined. For a slender uniform barge structure travelling in head seas, the response simulations and statistical data evaluated by the two theories show favourable agreement. However, for a non-slender uniform barge differences between predictions arise with the two-dimensional strip theory eventually failing, while the three-dimensional approach remains effective and its versatility is further demonstrated by predicting the slamming behaviour of a flexible barge structure travelling at arbitrary heading in an irregular seaway.
Non-Linear Sensitivity Analysis of Mechanical Structures Using Modal Data
Authors: To W M , Ewins D J 
Published: February 2007

This paper presents a new procedure for determining the revised modal properties (eigenvalues and mass-normalized eigenvectors) in a structural modification analysis. The procedure is based on expressing the eigenvectors of the modified structure as a linear combination of the eigenvectors of the original structure and employs the stationary property of the Rayleigh quotient to determine the modified structure's eigenvalues. It has the same theoretical basis as first- and second-order sensitivity analysis, but here the non-linear effects contributed by all high-order terms [generally assumed to be small relative to the effect contributed by first- and second-order terms (1–6)] are preserved in full. Hence, the usual shortcoming of sensitivity analysis—that it is limited to small modifications—is overcome. A special feature of this procedure is that the exact modal properties of the modified structure are determined without solving the generalized eigenvalue problem for the modified structure. Thus, this procedure can greatly reduce the computation cost and increase the efficiency of structural modification analysis (or reanalysis) during a structural optimization process. Numerical examples demonstrate the superconvergence characteristic of the technique. The limitations caused by modal and coordinate incompleteness, and the sensitivity of this technique with respect to simulated measurement errors, are investigated by using a finite element model of a steel frame structure and a ten-degrees-of-freedom mass-spring model.
Elastohydrodynamic Lubrication of Big-End Bearings Part 1: Theory
Authors: Aitken M B , McCallion H 
Published: February 2007

Lubrication of a dynamically loaded big-end bearing is re-examined under elastohydrodynamic assumptions. All current models are found to be in some way deficient; reference frame anomalies and erroneous connecting-rod kinetics proliferate. Part 1 of this work presents a consistent schema correcting deficiencies identified in previous big-end studies. Newton-Raphson and continuation techniques are developed for the solution of a Galerkin system formulation. This formulation additionally features a simple ‘vapour’ cavitation model. Part 2 presents verifications of the developed theory: comparisons with previous theoretical works along with an overdue comparison with previously published experimental results.
A Hybrid Method for the Vibration Analysis of Rotor-Bearing Systems
Authors: Firoozian R , Zhu H 
Published: February 2007

The transfer matrix method together with a digital computer form the foundation of the dynamic analysis of rotor-bearing systems. The properties of each segment of the rotating shaft are expressed in simple matrix form and the overall dynamic behaviour is then obtained by successive multiplication of the element matrices. The main drawback associated with this method is the numerical instability in calculating natural frequencies for complex systems. The finite element method, on the other hand, uses the element stiffness and mass matrices to form the global equation of motion for the complete system. This avoids the numerical problems of the transfer matrix method at the expense of the computer memory requirements. The new method described in this paper combines the transfer matrix and finite element techniques to form a powerful algorithm for vibration analysis of rotor-bearing systems. It is shown that the accuracy improves significantly when the transfer matrix for each shaft segment is obtained from finite element techniques. The accuracy and efficiency of the hybrid method are compared with the transfer matrix method for a simply supported uniform rotating shaft where an analytical solution for the critical speeds and mode shapes is available. The method is then applied to a flexibly supported uniform shaft and a non-uniform shaft with a large disc to show the capability of the method for finding the critical speeds of complex rotor-bearing systems.
Elastohydrodynamic Lubrication of Elliptical Contacts with Spin and Rolling
Authors: Dowson D , Taylor C M , Xu H 
Published: February 2007

Studies of elastohydrodynamic lubrication of point contacts have been undertaken since the early 1970s. Nearly all the investigations reported have been concerned with surface motions of rolling and/or sliding and little work has been reported on the common engineering problem of elastohydrodynamic lubrication with spin and rolling. This kinematic condition is found in angular contact bearings and variable-speed traction drive systems. The theoretical investigation described in this paper is therefore concerned with the elastohydrodynamic lubrication of non-conformal point contacts with both rolling/sliding (potentially) and spin. The study provides an indication of the importance of the superimposed spinning motion upon the rolling and sliding motions in the lubricated conjunctions. The results presented cover not only typical ratios of spin/rolling velocities but much higher values not encountered in the machine elements mentioned.
Buckling Design of Imperfect Welded Hemispherical Shells Subjected to External Pressure
Authors: Galletly G D , Blachut J 
Published: February 2007

Welded hemispherical or spherical shells in practice have initial geometric imperfections in them that are random in nature. These imperfections determine the buckling resistance of a shell to external pressure but their magnitudes will not be known until after the shell has been built. If suitable simplified, but realistic, imperfection shapes can be found, then a reasonably accurate theoretical prediction of a spherical shell's buckling/collapse pressure should be possible at the design stage. The main aim of the present paper is to show that the test results obtained at the David Taylor Model Basin (DTMB) on 28 welded hemispherical shells (having diameters of 0.75 and 1.68 m) can be predicted quite well using such simplified shape imperfections. This was done in two ways. In the first, equations for determining the theoretical collapse pressures of externally pressurized imperfect spherical shells were utilized. The only imperfection parameter used in these equations is δ0, the amplitude of the inward radial deviation of the pole of the shell. Two values for δ0 were studied but the best overall agreement between test and theory was found using δ0 = 0.05 ✓ (Rt). This produced ratios of experimental to numerical collapse pressures in the range 0.98–1.30 (in most cases the test result was the higher). The second approach also used simplified imperfection shapes, but in conjunction with the shell buckling program BOSOR 5. The arc length of the imperfection was taken as simp = k ✓ (Rt) (with k = 3.0 or 3.5) and its amplitude as δ0 = 0.05√(Rt). Using this procedure on the 28 DTMB shells gave satisfactory agreement between the experimental and the computer predictions (in the range 0.92–1.20). These results are very encouraging. The foregoing method is, however, only a first step in the computerized buckling design of welded spherical shells and it needs to be checked against spherical shells having other values of R/t. In addition, more experimental information on the initial geometric imperfections in welded spherical shells (and how they vary with R/t) is desirable. A comparison is also given in the paper of the collapse pressures of spherical shells, as obtained from codes, with those predicted by computer analyses when the maximum shape deviations allowed by the codes are employed in the computer programs. The computed collapse pressures are frequently higher than the values given by the buckling strength curves in the codes. On the other hand, some amplitudes of imperfections studied in the paper give acceptable results. It would be helpful to designers if agreement could be reached on an imperfection shape (amplitude and arc length) that was generally acceptable. Residual stresses are not considered in this paper. They might be expected to decrease a spherical shell's buckling resistance to external pressure. However, experimentally, this does not always happen.
Towards Optimum Carbon-Fibre-Reinforced Plastic End Closures
Authors: Błachut J , Galletly G D , Levy-Neto F 
Published: February 2007

Two series of external pressure tests on six-layer CFRP (carbon-fibre-reinforced plastic) torispherical domes are discussed in the paper. One series had a diameter-average thickness ratio of 80 and the other 120. The ratio Rs/D was the same for all the models and equalled 0.55 (Rs = spherical radius of a dome). The ratio r/D (r = toroidal or knuckle radius) varied from 0.2 to 0.5, the latter being a hemisphere. All the models were made by the hand lay-up/vacuum bag technique using male moulds. The failure modes considered were bifurcation buckling and first-ply failure (FPF). The BOSOR 4 program was used to evaluate the theoretical stresses in the shells and various failure criteria (Owen, Tsai-Wu etc.) were employed to determine the FPF pressures. In the tests, all the models failed by material failure rather than shell buckling and the ratios of the experimental collapse pressures to the FPF predictions were in the range 0.85–1.30. The tests also confirm a recent theoretical prediction that there is an optimum value of the r/D ratio insofar as dome strength is concerned. These CFRP torispherical domes are lighter and stronger than the comparable CFRP hemispheres. The BOSOR 4 predictions of FPF pressures and failure locations were confirmed by the NISA finite element code. The calculations also showed that it is necessary to use finite deflection shell theory when analysing these composite domes.
Simulation of Side Impact on Cars
Authors: Langdon M G 
Published: February 2007

Simulation models of side impact are used to improve understanding of the dynamic events which can only partially be observed and measured in full-scale impact tests, and to explore the effects of modifying structural design without the expense of building and impacting large numbers of experimental vehicles. It has also been suggested that they could be used for legislative testing. Simulation models for frontal impact into a rigid block were first developed about fifteen years ago. Subsequently side impact models were developed along similar lines, to represent impact by a rigid impactor, in accord with the then current methods of full-scale testing. The car structure was represented by a small number of discrete masses, connected by (non-linear) springs and dampers. The dummy occupant was initially represented by a single rigid mass. When a deformable barrier front was first used to replace the rigid barrier, this was merely represented by an additional spring in the model, and an attempt was made to introduce a more representative model of the dummy thorax. Comparison with full-scale test results has shown that this was an oversimplification and that relative motion between different parts of the car structure, and between different parts of the dummy, is an important factor in determining the likely level of injury. Currently work is proceeding on developing more realistic lumped parameter models which can reproduce these effects and which can take some account of the effect of dynamic impact (compared with quasi-static loading) on the spring elements. In many ways the ideal solution would be to use a dynamic finite element model, but these are complicated to set up and very expensive in computer running time. An exciting possibility for the future is the development of hybrid models, in which critical elements can be modelled by finite elements, but in which the bulk of the model still consists of lumped parameter elements.
Disc Brake Interface Pressure Distributions
Authors: Tirovic M , Day A J 
Published: February 2007

The nature of the contact and pressure at the interface between the friction material pad and the disc rotor of a ‘spot’-type disc brake affects the performance of a brake in terms of torque, temperature distributions and wear. Interface contact and pressure distributions have been predicted for a particular design of floating caliper passenger car disc brake, using three-dimensional finite element analysis under static and dynamic brake actuation conditions. The influence of friction material compressibility, pad backplate thickness, coefficient of friction, caliper flexure, disc stiffness and actuating piston contact with the piston bore on the interface pressure distribution is examined. The effect upon brake performance is discussed in terms of ‘centre of pressure’ and corresponding braking torque, and in terms of observed effects such as temperature and wear distribution. The results confirm that in order to ensure consistent disc brake performance the interface pressure distribution should be carefully controlled by designing in mechanical rigidity, compliant friction materials and minimum compliance during brake operation.
An Investigation of Thermal Insulation of IDI Diesel Engine Swirl Chambers
Authors: Charlton S J , Campbell N A F , Shephard W J J , Cook G , Watts M J 
Published: February 2007

The paper describes a computational and experimental study of the application of advanced ceramic materials for thermal insulation of the swirl chamber of the passenger car IDI diesel engine. Four ceramic materials, having a wide range of physical properties, were evaluated. These were syalon 101, aluminium titanate, reaction bonded silicon nitride (RBSN) and tetragonal zirconia polycrystals (TZP). A detailed finite element study was carried out in support of component design which examined parameters such as heat flux, operating temperature, thermal and assembly stresses and evaluated the requirements for interference fits between metallic and ceramic components. Experimental work was initially carried out on a steady state dynamometer test stand and later supported by vehicle tests on a chassis dynamometer and test track. The investigation has shown that current engineering ceramic materials have the potential for application in engine combustion chambers. A total of 254 hours of engine testing with ceramic chambers was achieved without catastrophic engine failure. Engine performance was unchanged by the adoption of a thermally insulated swirl chamber, probably because the increase in swirl chamber surface temperature obtained (increased from 660 to about 850°C at full load) was insufficient to modify the thermodynamic cycle. Hydrocarbon emissions were generally increased, however; this was due in part to the difficulty of sealing the air gap behind the ceramic chamber at the fuel injector and glow plug interfaces.
Process Safety—An Engineering Achievement
Authors: Kletz T A 
Published: February 2007

Up to the late 1960s the chemical industry looked upon safety as a non-technical subject but after a number of serious accidents technical people with production experience began to be appointed as safety advisers. There had been so little systematic thinking that it was not difficult for them to make improvements such as: the development of systematic methods, now widely used, for identifying and assessing hazards, the development of inherently safer designs (in contrast, the industry has been slower to adopt this change), the development of a new attitude towards human error. These, and other, changes produced a dramatic improvement in the industry's accident rate and raised the reputation of the subject to today's level. The 1980s were a period of consolidation rather than innovation. Finally, we look ahead to the 1990s.
An Analytical Approach to the Effects of Production Tolerances in Product Evaluation and Routine Quality Control
Authors: Lawrence C C 
Published: February 2007

Quality control procedures check either for dimensional accuracy or for particular performance characteristics of a product, but rarely for an integration of both. Dimensional accuracy is almost exclusively concerned with tolerance allowance, but functional characteristics are concerned with the nominal performance or state values. The consequence of such an approach is that the tolerance is not linked directly with the functional performance and, as such, is likely to convey the impression, if large variations are observed, that they are due to some intrinsic deviation in the product's performance or that there is an inconsistency within the material that is at fault. This paper uses the production of plastic fuel and water pipe to illustrate the cumulative effects that quite sensible and economic tolerance allowances may have upon performance data.
A Computational Modelling Approach to the Design of Stable Ventilation Systems
Authors: Boucher R F , Kissane M P 
Published: February 2007

The well-known glove box arrangement used in the nuclear industry maintains a pressure depression within a contaminated volume while allowing passage of a small purge flow to the filtration plant. Conventionally, if a glove tears for example, an electromechanical control system restores the depression by opening and regulating an extra connection to the filtration duct. However, faster response and lower maintenance overheads result from replacing the conventional system with the fluidic vortex amplifier (VA) but coupled ventilation system and VA dynamics can be unstable. Designers needed a tool to predict oscillatory performance and, ideally, to advise on the strengths of influence of network parameters on stability. A system modelling approach is presented in which pipework dynamics, including steady state friction, are presented by transmission line modelling (TLM). A semi-empirical feedback model of linearized VA dynamics has been developed and shown to be substantially correct. The model's restriction to small signals does not adversely affect investigation of perturbation growth or decay. Partial transmission line representation of the VA model with special measures for feedback allowed time-domain simulations of network perturbations. However, this approach is indirect and it was possible to convert the whole VA model to transmission lines and then reformulate the TLM scheme into a direct, quantitative stability analysis. Extension of the technique provided a means of assessing the sensitivity of the stability to simple network alterations. The method has been programmed on an 80386 PC and successfully used on a large ventilation system. Success in the present context of dynamic stability for fluidic nuclear ventilation networks should be repeatable in other areas since the approach is applicable to any TLM-amenable system, be it fluid, mechanical, electrical or mixed.
A Study of the Metering of Free Flowing Particulate Solids Using Multi-Flight Screws
Authors: Jafari J F 
Published: February 2007

Reports on multi-flight screw metering of free flowing solid particles, with side entry feed, could not be found in the available literature. But since the author worked to investigate its applicability as a seed metering mechanism for grain drills, the present work was considered essential as the first step. For this purpose, samples of 15 different free flowing particulate materials were closely sized and a test rig designed and constructed. Nine rotors of three, four, and five slots or flights were considered at speeds of 20, 40, 60, 80, and 100 r/min as desired. All experimental runs were replicated three times and the average values of the volumetric flowrates for each material, speed, and rotor were found. At the end a total of 410 data points were considered for analysis of the data based on dimensional analysis. The variable dimensionless groups were selected and analysed in such an order to produce linear relations. The overall results can be represented by the following equation: It was concluded that metering, as described by the above equation, was predictable within the limits considered for each dimensional group studied.
The Use of Structural Adhesives in the Construction of Rail Vehicles
Authors: Fowler J R 
Published: February 2007

Conventional railway vehicles are generally fabricated using traditional welding techniques. An extensive investigation of adhesive bonding technology as an alternative is reported. A description of how an optimum adhesive was selected and the characterization of its important properties—lap shear, fatigue, shear modulus, durability and impact—is given. The crashworthiness of large bonded details is compared with similar welded constructions. The manufacturing procedure used to produce large bonded bodysides (5.8 times 2.2 m) is described. The structural testing of bonded bodyside modules is reported and compared with a traditional welded structure. Bonded bodyside modules were incorporated into a production multiple unit. The modules had excellent finish and the unit has performed satisfactorily in passenger carrying service. Non-destructive techniques which allow disbonds to be detected during manufacture/assembly and at major service inspections are also discussed.
Landing Gear—the Aircraft Requirement
Authors: Greenbank S J 
Published: February 2007

The trends of major landing gear design parameters are presented reflecting the developments in aircraft performance over the last two decades. These trends illustrate the likely requirements for the future and identify the differences between civil and military landing gears. The aircraft manufacturer will inevitably demand a lower mass landing gear, increased service life and lower support costs of the product, the latter now becoming increasingly important. The method of achieving lower support costs, known as integrated logistic support, is summarized, highlighting the relevance to landing gear design. A number of likely changes required to meet future aircraft demands are discussed and how they will test the innovation and ingenuity of the landing gear designer. Key areas include, (a) stringent turn-round requirements demanded by aircraft operators, (b) computer control of actuation, nose wheel steering and wheel brake control systems and (c) the advent of advanced suspension systems, particularly for military STOVL and repaired runway operations.