bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of Tubular Cantilevers Conveying Fluid
Authors: Paidoussis M. P. 
Published: February 2007

In Part 1 a general theory is presented to account for the small, free, lateral motions of a vertical, uniform, tubular cantilever conveying fluid, with the free end being either below the clamped one (‘hanging’ cantilever) or above it (‘standing’ cantilever). Gravity forces are not considered to be negligible. It is shown that, when the velocity of the fluid exceeds a certain value, the cantilever in all cases becomes subject to oscillatory instability. In the case of hanging cantilevers buckling instability does not occur. Standing cantilevers, on the other hand, may buckle under their own weight; it is shown that in some cases flow (within a certain range of flow velocities) may render stable a system which would buckle in the absence of flow. Extensive complex frequency calculations were conducted to illuminate the dynamical behaviour of the system with increasing flow. The conditions of stability have also been extensively calculated and stability maps constructed. It is shown that dissipative forces may have either a stabilizing or a destabilizing effect on the system, partly depending on the magnitude of these forces themselves. The experiments described in Part 2 were designed to illustrate the dynamical behaviour of vertical tubular cantilevers conveying fluid. The experiments were conducted with rubber tubes conveying either water or air. The tubes were either hanging down or standing upright. It was observed that for sufficiently high flow velocities both hanging and standing cantilevers become subject to oscillatory instability. It was also observed that standing cantilevers which would buckle under their own weight in the absence of flow, in some cases are rendered stable by flow within a certain range of flow velocities. Qualitative and quantitative agreement between theory and experiment was satisfactorily good.
Absolute Viscosity of CCl2F2 and CHCl2F
Authors: Latto B. , Al-Saloum A. J. 
Published: February 2007

The absolute viscosity at atmospheric pressure was determined experimentally for the vapour phase of two halogenated hydrocarbon compounds, refrigerants R12 (CCl2F2) and R22 (CHCl2F) in the general temperature range −39·7° to 91·8°C. The maximum error of the data is believed to be ±3 per cent. Comparison with previous secondary measurements on the same compounds reveals that the maximum deviation of previous measurements are +5 per cent and −6 per cent for R12 and R22, respectively, over the common temperature range. The data obtained in this work and by others were correlated using third and fourth degree polynomials, a power function of the absolute temperature, and a collision theory approach, which yielded values for the reduced dipole energy, the velocity collision diameter, and the maximum energy of attraction for the molecules. Comparison of the data with that predicted by simple kinetic theory has been made.
An Elasto-Plasto-Hydrodynamic Lubrication Analysis of the Plane Strain Drawing Process
Authors: Bloor Susan M. , Dowson D. , Parsons B. 
Published: February 2007

In recent years there has been an accumulation of evidence of hydrodynamic lubrication in various metal forming processes. In the present paper the possibility of hydrodynamic action in the plane strain drawing process is explored in a theoretical analysis which takes account of the variation of lubricant viscosity with pressure and temperature and elastic and plastic deformation of the strip. The generation of heat within the lubricant is considered and linear heat flow in the rigid die is considered in the thermal analysis. In previous theoretical studies a rigid-plastic model has been adopted for the worked material, but in this analysis the influence of elastic deformation in the entry zone and elastic recovery at outlet is examined. The procedure applies the methods of elastohydrodynamic lubrication analysis to a situation in which the elastic distortion is followed by plastic flow. The term elasto-plasto-hydrodynamic lubrication is introduced to describe this situation. Results of the analysis are presented in the form of pressure and temperature distributions and film profiles. It is shown that hydrodynamic films of significant proportions can be developed under some conditions.
Effect of Gravity on the Performance of an Impact Damper: Part 1. Steady-State Motion
Authors: Sadek M. M. , Mills B. 
Published: February 2007

This paper, which examines the effect of gravity on the performance of an impact der, extends a previous paper (I)‡ concerned with the horizontal system. The analysis is in two parts: Part 1 which concerns itself with the calculation of all the theoretically possible steady-state motions with two impacts of the free mass, one at each end of its container, per cycle of the main mass; and Part 2§ which examines the dynamic stability and kinematic viability of the various steady-state solutions obtained in Part 1. The impact damper consists of a small mass free to move within a rigid container attached to the main vibrating system. Vibration suppression is achieved through energy dissipation during impacts and through cancellation of the effect of the external exciting force by the cyclical reaction of the free mass on the main system. The analysis shows that, in general, several different steady-state motions are theoretically possible for a given exciting frequency and that the effect of gravity on the motion of the system is to reduce the frequency range of two-impact-per-cycle motion. It is also shown that under the practically important condition of resonance the motion consists of two impacts of the free mass per cycle of the main mass. Outside the resonant condition, where the motion of the main mass is weak, the free mass may impact more or less than twice per cycle. This condition is not studied.
Some Non-Linear Effects in the Vibration of a Four-Bar Linkage
Authors: Gayfer J. R. , Mills B. 
Published: February 2007

The non-linear effects which are examined are those arising from the changes of linkage geometry during the course of the motion. The fundamental frequency of a linkage with rigid members controlled by discrete, linear torsion springs is analysed and solutions offered in terms of phase plane and energy methods, together with an approximate closed solution in the form of a harmonic series with terms in sin (2 n + 1)ω t and cos 2 nω t. Experimental results are presented for free and forced motions which, with one exception, agree well with the theoretical predictions of the energy and series solutions. In Appendix 1 a (velocity)2 term appearing in the series solution is shown to be a conservative, soft spring effect arising from apparently variable inertia.
Experimental Investigation into the Effects of Indenting a Cylindrical Shell by a Load Applied through a Rigid Boss
Authors: Morris A. J. 
Published: February 2007

A series of tests has been performed on thin unpressurized cylinders loaded by two equal and opposite forces applied across a diameter. Special emphasis was laid on elucidating the response of the specimens to large displacements in order to check the possible appearance of any snapping action. Tests were performed on cylinders both with and without edge constraints and the experimental procedure was devised in order to isolate, as far as possible, the effects of plastic strains. No actual strains were measured and the results presented all correlate the variation of displacements with variations in the applied loads.
Fatigue Crack Propagation in Polymethylmethacrylate; the Effect of the Mean Value of Stress Intensity Factor
Authors: Arad S. , Radon J. C. , Culver L. E. 
Published: February 2007

Polymeric components often contain structural defects which give rise to regions of internal stress concentration. As the engineering application of these materials expands, the need to understand their behaviour under various loading conditions becomes more necessary. This paper reports the results of part of a programme of research undertaken to study fatigue crack propagation phenomena in thermoplastics. A fracture mechanics approach is used and the effects of the mean stress intensity factor, Km, and the range of stress intensity factor, ΔK, on crack propagation phenomena in polymethylmethacrylate are studied. Based on the experimental data available, a relationship of the following form, between the cyclic crack growth rate d(2 a)/d N and the tensile loading levels, has been proposed d(2 a)/d N = β( Kmax2 – Kmin2) n where Kmax and Kmin are the maximum and minimum values of the stress intensity factor in each loading cycle. In tests at room temperature (21°C), in air, at a loading frequency of 5 Hz, n was found to be equal to 2·5; log β equalled —12·37.
Theoretical and Practical Aspects of the Application of Resonant Combustion Chambers in Gas Turbines
Authors: Muller J. L. 
Published: February 2007

This paper discusses theoretical and experimental work carried out to determine the feasibility of a pressure-gain combustion system for gas turbines. Fundamental principles involved in the design of resonant combustors are considered and potential improvements in gas turbine performance are calculated by means of a piston-cylinder analogy. The results indicate that significant improvements in overall thermal efficiency and specific power output can be expected at relatively low pressure ratios but that these improvements become less effective at higher pressure ratios due to the influence of increased compressor delivery temperatures. The results of experimental work on a multiple combustor configuration show that the theoretical performance appears to be attainable and that, subject to further development work, resonant combustion chambers could be utilized to improve gas turbine performance.
The Behaviour of Nucleation Fogs within the Nozzle Boundary Layer in the Wet Steam Turbine
Authors: Ryley D. J. 
Published: February 2007

At low pressures the boundary layer within a turbine blade passage carrying a nucleation fog is very sparsely populated with droplets and its hydrodynamic behaviour is not materially influenced by their presence. The rate of energy dissipation within the boundary layer is only sufficient to evaporate a very small fraction of the total liquid entrained in the layer; nevertheless, superheat due to temperature recovery is almost completely suppressed by this evaporation. Thermal coagulation is active within the layer and gradient coagulation is very significant when the droplets are large. Any valid theory of deposition by diffusion must recognize this fact. Calculations were made for the concave surface of a typical low pressure turbine blade and boundary layer properties of interest are displayed.
Experimental Investigation of Non-Linear Coupled Vibrations in Elastic Columns Excited at High Frequencies
Authors: Ramsey H. , Johnson D. , Hazell C. R. 
Published: February 2007

Contributions intended for publication as Research Notes should be limited in length to 1000 words and two illustrations, and should be addressed to the Editor of Proceedings at the Institution Headquarters in London. Coupling of flexual and longitudinal vibration modes has been observed experimentally in a slender column of rectangular cross-section subjected to periodic axial loading at frequencies up to 10 kHz; the fundamental longitudinal frequency of the specimen is 8·7 kHz. Resonance in the coupled flexural–longitudinal modes was observed when the frequency of axial excitation was 1, ½, and ⅓ times the fundamental longitudinal frequency. Strain levels at resonance in the coupled modes were comparable to strain levels in the purely flexural modes which were excited when the frequency of axial excitation corresponded to a flexural mode.
Unsteady Flow through a Four-Way Branch in the Exhaust System of a Multi-Cylinder Engine
Authors: Daneshyar H. , Pearson R. D. 
Published: February 2007

This paper is concerned with the investigation of unsteady flow through a four-way branch, with particular reference to its application to flow in the exhaust system of a multi-cylinder engine. The only methods of solution hitherto available are for unsteady flow through a three-way branch. The potentially most accurate theory of those reported takes pressure and entropy changes at the junction into account, but cannot be used in practice since the iterative processes employed in this method often become divergent (I)‡. A convergent method of solution has therefore been developed and is utilized to study the unsteady flow through a four-way branch, making the usual assumption of quasi-steady flow at the junction. A general computer programme for multi-cylinder engines combining the programmes for the cylinder boundary, for the nozzle boundary, for unsteady flow in the pipes, and the present method for branched systems has been developed (in Algol code) to compute the flow variables (pressure, velocity, and temperature) in the exhaust system and cylinders. The temperature variations which can arise in an engine are fully taken into account. Experimental data are presented for both steady and unsteady flow conditions. The steady data have been used to supply the pressure coefficients needed for full computation in the non-steady flow case. Simpler theories involving assumed pressure coefficients are also employed in shorter programmes which yield acceptable results of lower accuracy. Consequently, it appears that prediction can now be made to sufficient accuracy, in the range of pressure amplitudes and Mach numbers investigated, without the need for comprehensive steady flow testing.
An Exact Solution to the Variation in Force along Rotating Springs
Authors: Gillespie S. J. 
Published: February 2007

An exact solution to end reactions of a close coiled helical spring rotating about an axis perpendicular to that of the spring is shown. The solution allows for the general case of a spring initially offset longitudinally to the centre of rotation but restrained against bowing. The solution requires knowledge of spring dimensions and free and installed length.
The Cooling of Methane with Vortex Tubes
Authors: Williams A. 
Published: February 2007

Measurements have been made of the amounts of cold and heat produced by a vortex tube operated with methane containing some carbon dioxide, and with Algerian natural gas, which has a high methane content. The effects of gas supply temperature and pressure have been investigated. The contribution of the Joule–Thomson effect to the total cooling has been calculated and allowed for. Vortex effect cooling decreases with lowering of the supply temperature and probably disappears at the gas liquefaction point. It is dependent on the pressure expansion ratio across the tube. The findings are compared with those of other workers and those predicted by vortex tube theories.
Hydraulic Jacking
Authors: Eliasson E. T. 
Published: February 2007

The trend in modern plain journal bearing design is towards a reduction in the relative bearing width; this results in reduced machine bulk and bearing losses, but has the disadvantage of increased bearing wear, particularly at starting, stopping and the reversal of motion. A method of reducing this wear problem is by means of hydraulic jacking, or the separation of the load carrying surfaces by the introduction of high pressure oil into the clearance space, through suitable feed grooves. The article describes an analytical solution to the problem of hydraulic jacking. The following solutions are presented, giving full performance characteristics. (1) Single- and twin-axial feed grooves, end leakage neglected. (2) Single- and twin-axial feed grooves, concentric journal, finite length bearing (approximate solution). (3) Single- and twin-axial feed holes, concentric journal, small diameter feed holes (approximate solution). Some experimental verification is given for the theory of the axial feed groove arrangement, both the single grooved and the twin grooved arrangement.
The Plane Strain Indentation of Anisotropic Aluminium Using a Frictionless Flat Rectangular Punch
Authors: Venter R. , Johnson W. , de Malherbe M. C. 
Published: February 2007

In Part 1, the slip-line field solutions and the associated load requirements necessary for the indentation of anisotropic solids are presented. The analysis is based on Hill's approach to the analysis of anisotropic material. All results are recorded in terms of a lumped anisotropic parameter, c. In Part 2, the results of an investigation to determine the anisotropic parameters of a commercially available aluminium are reported. Specimens machined from the aluminium at selected orientations to the anisotropic axes were indented using a nominally frictionless flat rectangular punch. A comparison between the theoretical and experimental indentation loads is given.
Tests of some Taper-Hub Flanges with Narrow Gaskets
Authors: Fessler H. , Musson J. K. 
Published: February 2007

Seventeen 4 in bore models having two pipe thicknesses, various flange thicknesses and hub lengths, made of spheroidal graphite (s.g.) iron, mild steel and bronze, were subjected to series of initial bolt tensions and, at each bolt tension, pressurized in stages to leakage or failure of the metal. Outer surface strains were measured at each stage. Elastic behaviour was also determined from some Araldite models using strain gauges or frozen stress photoelasticity. The elastic flange-hub fillet stresses due to initial tightening are compared with predictions based on Taylor-Forge and DIN methods of calculation. For different positions of gasket reactions, the effect of internal pressure on flange fillet stresses may be predicted from consideration of the external forces. Plastic-elastic behaviour is described; leakage and failure characteristics are presented.
Turn-Up and Turn-Down in Hot Rolling: A Study on a Model Mill Using Plasticine
Authors: Buxton S. A. E. , Browning S. C. 
Published: February 2007

Turn-up and turn-down is a phenomenon which occurs in the hot rolling of flat products when the nose of a slab, or the whole slab, curls up or down upon emerging from the rolls and remains deformed unless subsequently straightened. Turn-up and turn-down can be troublesome to production, since it can cause damage to the mill rolls, housing, and run-out tables and can also cause production delays due to the difficulty of re-rolling a deformed slab. The object of this paper is to determine the main factors governing the phenomenon, to obtain quantitative relationships between causes and effects, and to suggest means of preventing curvature occurring. The best approach was considered to be a scale model using plasticine to simulate the hot metal. As a basis for the work, several dimensionless ratios are formed which have to be the same in both model and full size mill, if the model is to be both dynamically and geometrically similar. In the more important dimensionless ratios, account is taken of the plastic yield characteristics of the material, including the rate-of-strain component, of the stresses due to surface friction and gravity, and finally of the ratio of roll speeds. The results are compared with some previous work by others on steel slabs using a full size mill. In all respects, the results agree closely. The most significant factor affecting turn-up and turn-down is the ratio of surface speeds of the two work-rolls. Curvature is proportional to this speed ratio, but slipping at the rolls may modify this relationship. For a given angle of entry, the ratio of torque upon each roll is a function of the speed ratio. Angle of entry has negligible effect on turn-up and turn-down, but has a powerful effect upon the torque ratio. Slip is very undesirable and it appears that the roll surface finish should not be better than necessary if slip is to be avoided. To produce a flat slab, a speed ratio of about 0·97 is required in the model. In practice, this may be achieved either directly by controlling the speed ratio, or indirectly by controlling the torque ratio, provided the angle of entry is constant.
Unsteady One-Dimensional Compressible Frictional Flow with Heat Transfer
Authors: Issa R. I. , Spalding D. B. 
Published: February 2007

The paper briefly describes a numerical procedure for solving problems of one-dimensional, unsteady, compressible, frictional flows with heat transfer. The procedure is based on the Hartree ‘hybrid’ method which combines the use of a rectangular grid with the use of characteristics. The main features of the procedure are its applicability and ease of adaptability to complex unsteady-flow problems. Another feature is the simplicity of its programming for a computer. Computations for flows in shock tubes are presented; they are in good agreement with previously published experimental data.
Paper 2. Problems and Requirements of Directional Stability, Control and Manoeuvrability; High-Speed Craft
Authors: Eames M. C. 
Published: February 2007

The problems of stability and control of high-speed craft are somewhat different for the various vehicle types. The first part of this paper briefly compares characteristics of air-cushion vehicles and planing craft. This is followed by a more detailed discussion of the problems and requirements of hydrofoil craft.
Paper 15. Some Aspects of Prediction and Simulation of Manoeuvres
Authors: van Leeuwen G. 
Published: February 2007

Prediction and simulation are dependent on the knowledge gained from mathematical models. The choice and the form of the model is determined by the specific application and the accuracy required. Model techniques, such as horizontal oscillation tests, provide the means of finding the coefficients of extensive non-linear models, though for other purposes, such as simulation, there is also a need for simpler, empirical models. To determine the coefficients of such models, free-running full-scale or model tests are necessary.
Paper 24. Stability and Control Problems Associated with Acceleration and Deceleration
Authors: Jourdain M. 
Published: February 2007

This paper gives a general survey of the behaviour of surface vessels subjected to accelerations in a horizontal plane. There are two different cases which frequently occur in combination but which, for convenience, are treated separately. First, longitudinal acceleration is considered, including positive or negative acceleration in the fore and aft plane; problems of stability and manoeuvrability and means of improving directional control are discussed. Next, the manoeuvring problem associated with transverse accelerations is described, with particular emphasis on the use of auxiliary devices, such as side thrusters, and modified propulsive arrangements. Finally, the influences of currents, winds and restricted depth on manoeuvrability are outlined.
Fluid Oscillations in a Pitot Tube in Unsteady Flow
Authors: Horlock J. H. , Daneshyar H. 
Published: February 2007

An analysis is presented for the response of a pitot tube placed in an unsteady flow and connected to a liquid manometer. The error in time mean total pressure recorded by the system is negligible unless its natural frequency is close to that of the flow oscillations or unless the density of the measuring fluid is close to that of the fluid whose total pressure is being measured. The results of the analysis are broadly confirmed by experiment.
Transverse Modes and Frequencies of Beams Translating between Fixed end Supports
Authors: Simpson A. 
Published: February 2007

The effects of longitudinal steady translational motion on the vibration frequencies and modes of simple Euler beams are outlined. An example shows that the natural frequencies decrease monotonically with increasing translation velocity, while the mode shapes are complex, indicating significant phase disparities from point to point across the span. Divergence is shown to occur when the translation velocity is greater than the fundamental flexural wave propagation velocity. More general equations of motion, governing the translating Timoshenko beam under axial loading, are derived in Appendix 1.