Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1978"
TL;DR: In this paper, a method of non-destructively evaluating the integrity of structures is described and applied to structures for which a one dimensional analysis is satisfactory, and it is shown how vibration measureme...
Abstract: A method of non-destructively evaluating the integrity of structures is described and applied to structures for which a one dimensional analysis is satisfactory. It is shown how vibration measureme...
665 citations
TL;DR: In this article, a complete set of equations of motion and boundary conditions governing the vibration of sandwich beams are derived by using the energy approach, and they are solved exactly for important boundary conditions.
Abstract: A complete set of equations of motion and boundary conditions governing the vibration of sandwich beams are derived by using the energy approach. They are solved exactly for important boundary conditions. The computational difficulties that were encountered in previous attempts at the exact solution of these equations have been overcome by careful programming. These exact results are presented in the form of design graphs and formulae, and their usage is illustrated by examples.
326 citations
TL;DR: In this article, detailed flow measurements obtained by a new measuring technique are presented for the flow in a stalled axial-flow compressor, based on the observation that the fluid must cross from one side of the cell to the other in order to preserve continuity in the tangential direction.
Abstract: Detailed flow measurements obtained by a new measuring technique are presented for the flow in a stalled axial-flow compressor. Results were obtained from a wide range of compressor builds, including multi-stage and single-stage configurations of various design flow rates and degrees of reaction. Instantaneous recordings of absolute velocity, flow direction and total and static pressures have been included for both full-span and part-span stall.With the aid of these results, it has been shown that the conventional model of the flow in a stall cell is erroneous. An alternative model is proposed, based on the observation that the fluid must cross from one side of the cell to the other in order to preserve continuity in the tangential direction. An investigation of the experimental results also reveals the finer details of the flow in the cell and shows how these details are related to the design flow rate of the compressor. The influence of these cell details on the power absorbed by a stalled compressor ar...
90 citations
TL;DR: In this article, the normal and shear stiffness characteristics of joint interfaces formed from cast-iron surfaces which are subjected to a combination of normal and Shear forces were investigated. But the results were limited to a single measurement and averaged out small topological differences between nominally identical surfaces.
Abstract: The paper is concerned with the experimental investigation of the normal and shear stiffness characteristics of joint interfaces formed from cast-iron surfaces which are subjected to a combination of normal and shear forces. Because of the relatively small deflections, an experimental procedure is adopted which enables a number of interfaces to be considered in series, thereby increasing the resolution of a single measurement and averaging out small topological differences between nominally identical surfaces.The range of parameters investigated covers those which are used in current design practice. The combination of machined surfaces include ground on ground and hand-scraped on ground. These surfaces were subjected to normal pressures up to 9 times 106 Nm-2 and the resulting characteristics are represented in graphical form.
51 citations
TL;DR: In this paper, the authors used a miniature pressure and film thickness transducers mounted in the cylinder liner of a diesel engine to study the oil starvation in the inlet of the piston rings.
Abstract: Miniature pressure and film thickness transducers mounted in the cylinder liner of a diesel engine have been used to study the lubrication of piston rings. The method of using the gauges to determine oil starvation in the inlet of the rings is described and results from a working engine are presented. Calculations for both starved and fully flooded rings have been carried out and are compared with the measured results.
45 citations
TL;DR: In this article, the authors describe the construction and pressure testing of fifteen cylindrical shells made by filling the space between two thin, steel, concentric membranes with a resin-glass composite.
Abstract: The paper describes the construction and pressure-testing of fifteen cylindrical shells made by filling the space between two thin, steel, concentric membranes with a resin-glass composite. Their behaviour is compared with a previously published theory (1)†. The comparison is satisfactory over about two thirds of the length of the shell, with excellent agreement before the steel skins yield and good agreement with mean behaviour at higher pressures. All the shells remain totally stable after the steel skins have yielded and some achieve their full theoretical strength.
36 citations
TL;DR: In this article, large negative pressures have been observed in the oil film lubricating a piston ring, reaching a peak value of −0.78 MN/m2 (-113.1 lbf/in2), which is far in excess of the values normally assumed to be needed to produce cavitation.
Abstract: Large negative pressures have been observed in the oil film lubricating a piston ring. Just after the dead-centre position, these reach a peak value of −0.78 MN/m2 (-113.1 lbf/in2), which is far in excess of the values normally assumed to be needed to produce cavitation. They are only sustained for a short period of time, but have the important effect of reducing the minimum film thickness.
32 citations
TL;DR: In this article, a simple surface model is proposed to explain the deflection characteristics when two contacting machined surfaces are subjected to normal and shear forces, assuming that contac...
Abstract: In order to explain the deflection characteristics when two contacting machined surfaces are subjected to normal and shear forces, a simple surface model is proposed. This model assumes that contac...
29 citations
TL;DR: In this paper, the effects of quantization, sampling and the numerical model on the digital assessment of peak density, peak height distribution and peak curvatures are investigated, and it is shown that there are practical limits which should be adhered to in order to avoid erroneous results.
Abstract: The effects of quantization, sampling and the numerical model on the digital assessment of peak density, peak height distribution and peak curvatures are investigated. It is shown that there are practical limits which should be adhered to in order to avoid erroneous results.
26 citations
TL;DR: In this article, the authors investigated the effect of rotation on heat transfer in the entrance region of circular tubes that are constrained to rotate about an axis parallel to the symmetry axis for cooling the rotor windings and armature drums of electrical machines.
Abstract: The paper presents the results of an investigation into the effect of rotation on heat transfer in the entrance region of circular tubes that are constrained to rotate about an axis parallel to the symmetry axis. This rotating geometry is an important feature of flow systems designed for cooling the rotor windings and armature drums of electrical machines and other prime movers. It is demonstrated that rotation tends to improve local and mean heat transfers, and correlating equations are proposed for turbulent and laminar flows.
23 citations
TL;DR: In this article, a theoretical model of the squeeze-film bearing unassisted by a retainer spring is developed, based on experimental information revealing the ability of the squeezfilm to sustain appreciable subatmospheric pressure.
Abstract: A theoretical model of the squeeze-film bearing unassisted by a retainer spring is developed, based on experimental information revealing the ability of the squeeze-film to sustain appreciable subatmospheric pressure.
TL;DR: In this paper, the authors presented the complete, three-dimensional, subsonic, non-viscous flow in turbo impellers of arbitrary shape (axial, radial or mixed flow) using the finite-element method.
Abstract: The calculation of the complete, three-dimensional, subsonic, non-viscous flow in turbo impellers of arbitrary shape (axial, radial or mixed flow) is presented. The finite-element method is used to...
TL;DR: In this paper, a theoretical study of the hydrodynamic load capacity and friction between a ball-bearing ball element and its straight-sided annular pocket is presented, which enables forecasts of load capacity, stiffness, torque and power absorbed to be made.
Abstract: This paper reports a theoretical study of the hydrodynamic load capacity and friction between a ball-bearing ball element and its straight-sided annular pocket. Design curves are derived which enable forecasts of load capacity, stiffness, torque and power absorbed to be made. The theory is confirmed by appropriate experiments and is also compared with previously published results obtained elsewhere by indirect means.
TL;DR: In this paper, the authors examined the use of some differential formulae in the context of surface texture profile analysis and showed that simple models of real profiles are adequate to predict the observed behaviour.
Abstract: This paper examines the use of some differential formulae in the context of surface texture profile analysis. After a theoretical analysis, their behaviour on real profiles was studied. It is shown that simple models of real profiles are adequate to predict the observed behaviour and so allow a judgement to be made on the accuracies of the formulae under real conditions.
TL;DR: In this article, an equation for predicting the friction pressure gradient during turbulent two-phase flow in smooth pipes was developed, which can be extrapolated to smooth pipes with rough surfaces.
Abstract: An equation is developed which enables procedures for predicting the friction pressure gradient during turbulent two-phase flow in smooth pipes to be extrapolated to pipes with rough surfaces.
TL;DR: This paper presents a procedure for obtaining the conditions for a full force-balance of a planar linkage that automatically uses the minimum number of counterweights and keeps the added inertia low.
Abstract: This paper presents a procedure for obtaining the conditions for a full force-balance of a planar linkage. It includes a check on whether a full force-balance is possible where the presence of prismatic joints or links that cannot be counter-weighted for some reason may preclude this. The procedure automatically uses the minimum number of counterweights and keeps the added inertia low. An example demonstrates the advantages of the procedure over those methods that require the derivation of the kinematic equations of motion for the linkage.
TL;DR: In this paper, a surface vorticity theory is developed for the prediction of annular aerofoil performance in three-dimensional flow, based on the basic Fredholm integral equations.
Abstract: Starting from the basic Fredholm integral equations, a surface vorticity theory is developed for the prediction of annular aerofoil performance in three-dimensional flow. A mathematical model is proposed for the general case of the axisymmetric body in non-axisymmetric flow, using a Fourier series to represent circumferential variations in bound vorticity strength. Using the pure incidence case as an example, it is indicated how an economical solution of the flow may be arrived at by use of a digital computer. The theoretical pressure distributions obtained are compared with the results of wind-tunnel tests on an annular aerofoil model.
TL;DR: In this article, a periodic displacement disturbance is imposed on an aerostatic, porous, journal bearing of finite length under steady-state conditions, and the dynamic pressure distribution is obtained by a pressure perturbation analysis of Reynolds equation and a modified flow continuity equation in a porous medium.
Abstract: A periodic (displacement) disturbance is imposed on an aerostatic, porous, journal bearing of finite length under steady-state conditions. The dynamic pressure distribution is obtained by a pressure perturbation analysis of Reynolds equation and a modified flow continuity equation in a porous medium. Dynamic stiffness and damping coefficients for different operating conditions are calculated numerically, using a digital computer, and presented in the form of design charts.
TL;DR: In this article, double-skinned composite shells of imperfect geometry were collapsed under external pressure and the performance of the shells was compared to their theoretical strength and stability failure pressures. But the authors only considered the case where the shells were designed to withstand pressures equal to or, if required, greater than the pressure required to cause yielding of the steel membranes in the circumferential direction.
Abstract: In addition to the tests previously reported (1)†, ten further double-skinned composite shells of imperfect geometry were collapsed under external pressure. This paper seeks to relate the performance of the shells to their theoretical strength and stability failure pressures. One of the conclusions is that this type of shell can be confidently designed to withstand pressures equal to or, if required, greater than the pressure required to cause yielding of the steel membranes in the circumferential direction.
TL;DR: In this article, the free response of a gyroscope to a constant applied rate of turn is derived and the form of each response is greatly influenced by the geometry, inertia and stiffness characteristics of the suspension and the rotor speed.
Abstract: The paper considers the dynamics of a gyroscope where the gyro rotor is supported and driven through a gimbal suspension, which takes the form of a parallel assembly of universal couplings. The linearized equations of motion are derived and the free response, and the response to a constant applied rate of turn, are determined. It is shown that the form of each response is greatly influenced by the geometry, inertia and stiffness characteristics of the suspension and the rotor speed. Tuning conditions are identified and the performance of the gyroscope as either an angular rate or an angular displacement sensor is evaluated.
TL;DR: In this paper, a two-dimensional temperature and stress distribution for an orthotropic elastic body having a rectangular boundary is examined for situations in which one edge of the rectangle experiences an arbitrary variation of temperature, heat flow or convection, while each of the remaining edges is either insulated or maintained at the initial temperature.
Abstract: Stationary two-dimensional temperature and stress distributions are examined for an orthotropic elastic body having a rectangular boundary. Temperature fields are determined for situations in which one edge of the rectangle experiences an arbitrary variation of temperature, heat flow or convection, while each of the remaining edges is either insulated or maintained at the initial temperature. Displacement potentials are then used to find the thermal stresses for those cases in which the temperature remains constant over two opposite ends of the rectangle. As an illustrative example, the temperature and stresses resulting from a uniform temperature rise over a portion of one edge of the rectangle are computed; numerical results are given for a fibre-reinforced composite material.
TL;DR: In this article, the effect of damping and mistuning on the performance of a dynamically-tuned, multigimbal, Hooke's-joint gyroscope is examined.
Abstract: The paper examines the effect of damping and mistuning on the performance of a dynamically-tuned, multigimbal, Hooke's-joint gyroscope. The dynamic stability of the gyro is considered and rotor damping is shown to be a source of instability at rotor speeds in excess of the tuning speed. Using an approximate solution to the governing equations of motion, it is shown that the instrument's capacity to measure either rate of turn or total angular displacement is limited by the degree of mistuning and the damping conditions. The response of the tuned instrument to harmonic inputs at twice rotor frequency is examined and the conditions for a 2ω drift-free gyro are derived.
TL;DR: In this article, the ploughing action of hard asperities was used to calculate the coefficient of friction and wear of an annular end surface of a mild-steel cylinder rubbed by that of a hardened steel cylinder.
Abstract: Assuming that the radii of curvature at tips of spherical asperities are distributed, analyses of friction and wear in boundary lubrication are carried out by considering the ploughing action of hard asperities. To check the theory, the coefficient of friction and the wear rate of an annular end surface of a mild-steel cylinder rubbed by that of a hardened-steel cylinder are measured for various degrees of roughness from 0.038 to 0.568 μRmax under lubricated conditions. The general trend of the experimental results is in agreement with the calculations. The results also indicate that the repetition of the ploughing action of hard asperities forms the wear particles.
TL;DR: In this paper, a comprehensive investigation is made into the merits of annular injection as a means of obtaining a high-performance diffuser with short axial length, and it is shown that injection yields considerable improvements in both the quality of discharging flow and the magnitude of the pressure recovery.
Abstract: A comprehensive investigation is made, for a wide range of incompressible flows, into the merits of annular injection as a means of obtaining a high-performance diffuser with short axial length.Results show that injection yields considerable improvements in both the quality of the discharging flow and the magnitude of the pressure recovery. Accordingly, the technique is strongly recommended when a short, high-performance diffuser is required and when a suitable secondary supply is available. Recommendations are also made regarding the optimum cone angle and the geometry of the injection slot.
TL;DR: In this paper, it was shown that it is not possible to draw either a unique p-v diagram or a unique t-s diagram for any practical embodiment of the Stirling cycle.
Abstract: Equations are set up by means of which arbitrarily selected particles of working fluid may be ‘tracked’ continuously throughout a cycle Pressure is assumed to be instantaneously uniform, but account is taken of variable working space temperatures Fluid particle trajectory maps are presented for machines of two types One has opposed pistons following the ‘ideal’, discontinuous motion The other has coaxial piston and displacer actuated by the rhombic drive mechanism For the limiting case of isothermal phases, pressure is plotted against specific volume, and temperature against specific entropy for selected tracked particles Thus it is deduced that, even when the unswept volume is taken to be zero, and piston motion to be discontinuous, it is not possible to draw either a unique p-v diagram or a unique t-s diagram for any practical embodiment of the Stirling cycle It is demonstrated that such relationships may be viewed instead as summations of an infinity of p-vs or t-s relationships, that is, one fo
TL;DR: A description of roughness and misalignment of the guideway surface is proposed which is valid in both statistical and wave-length-amplitude domains and a method of computer generation to typical roughness profiles is discussed.
Abstract: One of the significant disturbances to a tracked hovercraft or any other high-speed ground transport vehicle is the roughness of the guideway surface together with misalignment of the guideway structure itself. Existing methods of describing this roughness and misalignment are reviewed and their shortcomings noted. A description is proposed which is valid in both statistical and wave-length-amplitude domains. A method of computer generation to typical roughness profiles is discussed.
TL;DR: In this article, an analysis of the stress path and the strain trajectory of a pre-strained engineering material in the deviatoric plane is presented, and the significance of the isotropic hardening rule in relation to a metal's straining memory is demonstrated.
Abstract: An analysis of the stress path and the strain trajectory of a pre-strained engineering material in the deviatoric plane is presented. The deviatoric stress vector, which for a pre-strained material is initially at an angle to the strain trajectory, is shown to coincide with it after the ‘recoverable’ energy is consumed.Experimental work is carried out on the yield criteria and the stress—strain relationships of a pre-strained commercially pure aluminium. The significance of the isotropic hardening rule in relation to a metal's straining memory is demonstrated. It is shown that beyond a stress level associated with an isotropic hardening rule based on the Mises yield criterion, the representative stress—strain curves of a pre-strained specimen run parallel to that of an annealed material.
TL;DR: In this paper, equilibrium solutions for the thermoelastic displacements of an initially wavy, moving surface subjected to non-uniform viscous heating derived from a hydrodynamic lubricant film were given.
Abstract: Equilibrium solutions are given for the thermoelastic displacements of an initially wavy, moving surface subjected to non-uniform viscous heating derived from a hydrodynamic lubricant film. The configuration studied is similar to a flexibly mounted face seal with one metallic face running against a thermal insulator. Changes in mean film-thickness with changing speed are discussed with reference to earlier analyses which predicted thermoelastic instability and to experiments which illustrated this. The operating conditions approach those where instability was predicted for conditions of fixed mean film thickness; however, no instability is predicted for present conditions where axial load is fixed. Thermoelastic effects upon growth of surface waviness become significant when the sliding speed exceeds u*, given by u* = h1k √(K/µ), where h1 is the initial waviness amplitude, K is the wave number (κ = π/Λ, where Λ is half the wavelength of a sinusoidal waviness), K is the thermal conductivity of the metal, μ...
TL;DR: In this paper, the effects of pile-up (cutting efficiency, β) on surface finish (Ra) were investigated for a single-grit approach to simulate random surfaces; the geometric shapes used in the theory are also used to form actual surfaces.
Abstract: Theoretical models are developed to simulate random surfaces; the geometric shapes used in the theory are also used to form actual surfaces using a ‘single-grit’ approach. A particular feature of the work is the study of the effects of pile-up (cutting efficiency, β) on surface finish (Ra). For a unit event, the theory relates surface finish to cutter geometry, pile-up and load; the equivalent parameters for grinding are the average slope of the abraded surface, process efficiency and average load per grit. Finally, similar experimental techniques are used to synthesize the formation of a ground surface at spark-out.