Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1979"
TL;DR: In this article, the wheelflats on railway vehicles are created by wheelslide in braking: the resulting imperfection in the running line generates dynamic forces and stresses at each subsequent revolution.
Abstract: Wheelflats on railway vehicles are created by wheelslide in braking: the resulting imperfection in the running line generates dynamic forces and stresses at each subsequent revolution. The authors ...
184 citations
TL;DR: In this paper, the feasibility of controlling the vibrational behavior of a flexible rotor using squeeze-film isolators was investigated using a vibrational model of the rotor, and the results showed that it is possible to control both synchronous and non-synchronous vibrational behaviour.
Abstract: This paper describes work in which the feasibility of controlling the synchronous and non-synchronous vibrational behaviour of a flexible rotor was investigated using squeeze-film isolators in seri...
54 citations
TL;DR: In this paper, the effect of a radial temperature gradient on the hydrodynamic stability in the annular gap formed by two, vertical, concentric cylinders, the inner being rotatable and the outer both stationary and isothermally heated, was studied for the cases of zero and imposed axial fluid flow.
Abstract: The effect of a radial temperature gradient on the hydrodynamic stability in the annular gap formed by two, vertical, concentric cylinders, the inner being rotatable and the outer both stationary and isothermally heated, was studied for the cases of zero and imposed axial fluid flow in the annular gap. For zero axial flow, it was found that the temperature gradient destabilizes the flow while not affecting the form of the secondary flow, viz. the classic Taylor vortex. For imposed axial flow, the point of neutral stability was modified only when natural convection was strong enough to affect the parabolic velocity profile associated with that flow; the extent of this modification was shown to depend on the direction of the axial flow. Also, the longitudinal temperature gradients within the gap were found to influence the axial wave number and the drift-velocity ratio.
39 citations
35 citations
TL;DR: In this paper, a laser-Doppler technique was applied to measure the flow field inside a closed, backswept impeller through a rotating window, in contrast to the flow in many radial...
Abstract: A laser-Doppler technique is successfully applied to measure the flow field inside a closed, backswept impeller, through a rotating window. Results show that, in contrast to the flow in many radial...
32 citations
TL;DR: In this paper, the authors present a general method for calculating the pressure distribution and the deformations in machine joints, assuming that the components of the joint are connected through finite elements which are defined as a function of the surface finish, material and pressure at the apparent area of contact.
Abstract: This paper presents a general method for calculating the pressure distribution and the deformations in machine joints. This method assumes that the components of the joint are connected through finite elements which are defined as a function of the surface finish, material and pressure at the apparent area of contact. The system so established is solved in an iterative manner using the finite-element method, obtaining, as a final result, the pressure distribution at the contacting surfaces of the components and the deformations of the surrounding body. To prove the validity and precision of the theoretical formulation, several examples of joints are considered where the correlation between the calculated and measured deflections is shown to be good.
27 citations
TL;DR: In this article, a statistical analysis of the experimental measurements for freshly-assembled contacts was established relating the loading pressure, mean roughness of the two surfaces and oxide film thicknesses to the thermal resistance of the contacts in high vacua.
Abstract: Flat, rough surfaces of steel specimens were oxidized and subsequently pressed into contact. From a statistical analysis of the experimental measurements for freshly-assembled contacts, an expression has been established relating the loading pressure, mean roughness of the two surfaces and oxide film thicknesses to the thermal resistance of the contacts in high vacua. The thermal contact resistance increased with (i) the film thickness and (ii) the ratio of the total film thickness to the mean surface roughness, and decreased with the loading pressure and the mean surface roughness. Increasing and decreasing the applied load revealed a slight hysteresis effect.
25 citations
TL;DR: In this paper, numerical solutions for the pressure distribution and footprint shape of a roller in a roller bearing subjected to both radial load and misalignment are given. But the method used makes it possible to profile the rollers axially until the longitudinal pressure distribution is either almost uniform or does not have any severe peaks, thereby increasing the bearing service life.
Abstract: Numerical solutions are given for the pressure distribution and footprint shape of a roller in a roller bearing subjected to both radial load and misalignment. The method used makes it possible to profile the rollers axially until the longitudinal pressure distribution is either almost uniform or does not have any severe peaks, thereby increasing the bearing service life.
25 citations
TL;DR: In this paper, a systematic procedure for the dynamic analysis of planar mechanisms with multiple clearances is presented, where each link of the mechanism is considered as a rigid member, and contact modes are detected by iteration according to the inequalities of input torque and pin forces.
Abstract: A systematic procedure for the dynamic analysis of planar mechanisms with multiple clearances is presented. Each link of the mechanism is considered as a rigid member, and contact modes are detected by iteration according to the inequalities of input torque and pin forces. The method is useful for predicting the number and frequency of contacts and separations occurring in the mechanism-joints for one complete cycle of the input crank.A four-bar mechanism is used to illustrate the procedure. Results show that there are significant changes in accelerations, torque and pin forces as compared with the case without clearances. Minimal changes have been detected in displacement and velocity relationships.The model presented in the paper provides a design method for investigating torque requirements, pin forces and separation occurrences in high-speed machines with clearance.
22 citations
TL;DR: In this article, a linear analytical model of a ground-vehicle suspension system employing a pneumatic isolator and a three-way servovalve is developed, which is shown to reduce body transmissibility at very low frequencies, but is also capable of very good isolation throughout the broad frequency range.
Abstract: A linear analytical model of a ground-vehicle suspension system employing a pneumatic isolator and a three-way servovalve is developed. Damping is provided by connecting the pneumatic spring to a constant-volume surge tank through capillary resistances. Non-dimensional dynamic equations for the valve-controlled, self-damped, pneumatic isolator are derived and the effects of various feedback and feedforward controls on the performance of the closed-loop system are pointed out. Experiments are conducted to verify the validity of the assumptions made in deriving the absolute and relative displacement transmissibilities and the vehicle model is simulated on an analogue computer. It is shown that a servovalve-controlled pneumatic suspension system not only considerably reduces the body transmissibility at very low frequencies, but is also capable of very good isolation throughout the broad frequency range.
19 citations
TL;DR: In this paper, an approximate theoretical model is developed to estimate the effects of errors in temperature measurement on the computation of heat-transfer coefficients, h, from the numerical solution of Fourier's equation.
Abstract: An approximate theoretical model is developed to estimate the effects of errors in temperature measurement on the computation of heat-transfer coefficients, h, from the numerical solution of Fourier's equation. The model predicts that, depending on the Biot number and the algorithm used, a small random error on temperature will produce an amplified random error on the calculated instantaneous value of h and a bias in the average value, . ‘Experimental results’, simulated using Monte Carlo methods, are in reasonable agreement with the model, and it is shown that improved estimates of the heat-transfer coefficient can be obtained by using smoothing curves to minimize the effects of noise on measured temperatures.If the temperature measurements have a small positive bias, the theoretical model and ‘experimental results’ show that there can be a large negative bias in the calculated value of h. It is also shown that ‘missing thermocouples’ can be partially compensated for by using interpolation polynomials...
TL;DR: In this article, the results of a shear stress investigation for combined axial and rotational flow, under conditions of both laminar flow and laminars plus Taylor vortices, are presented.
Abstract: The results of a shear stress investigation for combined axial and rotational flow, under conditions of both laminar flow and laminar flow plus Taylor vortices, are presented These results show that two distinct regimes of shear stress dependency exist In the primary regime, the shear stress is constant and depends only on the imposed axial flow, the flow being either laminar (Poiseuille and Couette flows) or laminar with vortices, but with the effect of the vortices being negligible In the secondary regime, the shear stress is shown to depend only on Ta0735, irrespective of the imposed axial flow At low axial flow rates, a tertiary regime was observed, but no satisfactory explanation can be found for this phenomenon The demarcation between the primary and secondary flow regimes differs markedly from those of other investigators In the present study, critical conditions are determined by the point at which vortices begin to have an effect on measurements taken at the outer annular wall rather than
TL;DR: In this paper, the authors investigated the impact of failure mode on oblique impact by using targets having a wide range of strengths, and they found that angling of targets raises the hardness at which adiabatic shear begins to cause a reduction in penetration resistance in steels with hardness.
Abstract: In order to simplify the analysis of results, most investigations of oblique impact have restricted the range of target properties so that only one failure mode is obtained. The present work attempts to show the influence of failure mode on oblique impact by using targets having a wide range of strengths. Experiments are described in which the critical angle to defeat 0.30-calibre APM2 projectiles at two impact velocities and two target thicknesses is obtained for steel targets ranging in hardness from 270 to 735 HV. The data are used to investigate the effect of oblique impact on areal density, and it is found that softer targets (less than about 450 HV) give greater improvement in areal density with angling. The mode of target failure is related to the penetration resistance/hardness relationship. It is found that the angling of targets raises the hardness at which adiabatic shear begins to cause a reduction in penetration resistance in steels with hardness, from about 350 HV to around 430 HV. This effe...
TL;DR: In this paper, a discrete-time approach to estimate the linearized velocity coefficients of a squeeze-film bearing is described. But the estimation of the coefficients is assumed that motions in the vertical and horizontal directions are uncoupled.
Abstract: This paper describes the application of a discrete-time approach to the estimation of the linearized velocity coefficients of a squeeze-film bearing. It is assumed that motions in the vertical and horizontal directions are uncoupled. Sampled observations from laboratory experiments are processed digitally to yield estimates of the parameters in a vector-matrix difference equation. A transformation applied to this equation produces direct estimates of the oil-film coefficients. Verification of the estimated coefficients is achieved through the prediction of the dynamical behaviour of the bearing. In this way, the effectiveness of the experimental models is assessed and compared with predictions based upon short, uncavitated bearing theory.
TL;DR: In this paper, the governing equations of vibrations of double-layered cylindrical shells are derived from classical thinshell theory and the outer layer of the shell is assumed to be viscoelastic, possessing high damping capacity to control vibrations (loss factor, β = 0.3).
Abstract: The governing differential equations of vibrations of double-layered cylindrical shells are derived from classical thinshell theory. The outer layer of the shell is assumed to be viscoelastic, possessing high damping capacity to control vibrations (loss factor, β = 0.3). Decoupled torsional and coupled radial-longitudinal vibration modes are analysed by the method of ‘damped normal modes’. The present theory refines Kagawa and Krokstad's former analysis (1)‡. The results obtained point to a strong dependence of mechanical losses upon the thickness-to-radius ratio, h1/R, even in the case of axisymmetric modes. This phenomenon was not recognized in Kagawa-Krokstad's approach.
TL;DR: In this article, a nonlinear analysis of unsymmetric, angle-ply, rectangular plates under uniform in-plane edge shear is presented, based on the von Karman-type large-deflection equations, with the force function and the transverse deflection expressed as double series in terms of appropriate beam functions.
Abstract: A nonlinear analysis of unsymmetric, angle-ply, rectangular plates under uniform in-plane edge shear is presented. The solution is based on the von Karman-type large-deflection equations, with the force function and the transverse deflection expressed as double series in terms of appropriate beam functions. The prescribed boundary conditions, including those for the vanishing of normal bending moment at the edges of simply supported plates, are satisfied. Numerical results for the buckling loads and for the post-buckling deflections, membrane forces and bending moments are presented for plates composed of high-modulus, fibre-reinforced epoxy composites.
TL;DR: In this article, a perturbation theory for small vibrations is used to solve an incompressible, finite journal bearing with a time-dependent term, and load capacity, attitude angle, friction parameter, stiffness and damping coefficients are evaluated for a capillary-compensated bearing.
Abstract: A theoretical analysis of the steady-state and dynamic characteristics of multi-recess hybrid oil journal bearings is presented. A perturbation theory for small vibrations is used to solve an incompressible, finite journal bearing with a time-dependent term. Load capacity, attitude angle, friction parameter, stiffness and damping coefficients are evaluated for a capillary-compensated bearing.
TL;DR: In this article, a numerical technique is developed for predicting the evolution of drop-size spectra in turbulent, two-phase pipe flows while relevant to many chemical engineering processes, it is applied here to the crossover pipes of a nuclear wet steam turbine.
Abstract: A numerical technique is developed for predicting the evolution of drop-size spectra in turbulent, two-phase pipe flows While relevant to many chemical engineering processes, it is applied here to the crossover pipes of a nuclear wet-steam turbineValid expressions for turbulent coagulation rate in the cross-over pipes are available only for drops below about 10 μm diameter in the core flow, and for those exceeding about 20 μm near the pipe wall Using these expressions, it is found that the rapid formation of large drops in the core allows prediction for only a small fraction of the typical residence time in the pipe, but near the wall the volume median diameter of an initial 20 μm monodispersion can double in 100 ms Further work is required to validate the technique and extend it to handle the intervening ranges of drop size and turbulence parameters
TL;DR: In this paper, the hydrodynamic stability of the flow in an annular gap, formed by a stationary outer cylinder and a rotatable inner cylinder, through which an axial flow of air can be imposed, is studied experimentally.
Abstract: The hydrodynamic stability of the flow in an annular gap, formed by a stationary outer cylinder and a rotatable inner cylinder, through which an axial flow of air can be imposed, is studied experimentally. Two annulus radius ratios of 0.8 and 0.955 are considered, representing wide- and narrow-gap conditions, respectively. It is shown that, when a large, axial pressure gradient is superimposed on the tangential flow induced by the rotation of the inner cylinder, the characteristics of the flow at criticality change significantly from those at zero and low axial flows, the axial length and width of the resultant spiral vortex departing greatly from the known dimensions of a Taylor vortex cell at zero axial flow. Also, the drift velocity of the spiral vortex is found to vary with the axial flow. Axial Reynolds numbers, Rea, of up to 700 are considered.
TL;DR: In this paper, a method for calculating three-dimensional, time-dependent, inviscid, subsonic flow is presented for flow through the rotor of a small radial inflow turbine and comparison with conventional throughflow calculations and experimental results is made.
Abstract: A method for calculating three-dimensional, time-dependent, inviscid, subsonic flow is presented. Application is made to flow through the rotor of a small radial inflow turbine and comparison with conventional through-flow calculations and experimental results is made. The nature of the strong secondary flow in this rotor indicates the probable inadequacy of the two-dimensional calculations which is confirmed by the comparison.
TL;DR: In this article, the authors investigated the axial and rotational flow in a concentric annular gap, formed by a stationary outer and a rotatable inner cylinder, and the effects of hydrodynamic instability on the mean flow were investigated.
Abstract: This experimental investigation is devoted to the study of combined axial and rotational flow in a concentric annular gap, of radius ratio 0.8, formed by a stationary outer and a rotatable inner cylinder. Taylor numbers varying from the critical to an order of 106 will be considered. The investigation is divided into three parts, illustrating different aspects of spiral vortex flow. Firstly, the evolution of the flow with increasing Taylor number at a constant axial Reynolds number is studied by the analysis of the spectrum of the signal from a hot-wire anemometer. Secondly, the wave length and drift velocity of the spiral vortices are determined for the axial direction. Thirdly, the effects of hydrodynamic instability on the mean flow are investigated. It should be noted that the first and second parts are under adiabatic conditions, while the third is both adiabatic and diabatic, heat being transferred isothermally through the outer wall of the annular gap. Also, all of the measurements were made in the...
TL;DR: In this article, an investigation into a developing, combined axial and rotational flow in an annular gap formed by a stationary outer cylinder and a rotatable inner cylinder for an annulus radius ratio of 0-8 and an axial Reynolds number of 1200 was performed.
Abstract: Results are presented of an investigation into a developing, combined axial and rotational flow in an annular gap formed by a stationary outer cylinder and a rotatable inner cylinder for an annulus radius ratio of 0–8 and an axial Reynolds number of 1200.These results show that, in the Taylor vortex flow regime, the development length decreases with the parameter Re2a/Ta and that the greatest development length in an annular gap, for a given axial Reynolds number, occurs when the Taylor number is near to its critical value.Consideration of isothermal heat transfer through the outer wall of the annular gap suggests that, in the development of the flow, the Nusselt number rises to a high value before falling to a constant value, at full development.
TL;DR: In this article, the thermal resistances of two pressed contacts, which under isothermal conditions were respectively between (i) a flat and a convex surface and (ii) nominally flat surfaces, have been predicted and the deductions compared with experimental measurements.
Abstract: The thermal resistances of two pressed contacts, which under isothermal conditions were respectively between (i) a flat and a convex surface and (ii) nominally flat surfaces, have been predicted and the deductions compared with experimental measurements. The analysis evolved is useful in the design of thermal rectifiers.
TL;DR: In this paper, the numerical solution of the equations of compressible flow through axisymmetric convergent nozzles is described, and the class of supercritical flows is considered, in which the gas velocities in the jet downstream from the throat are supersonic.
Abstract: The paper describes the numerical solution of the equations of compressible flow through axisymmetric convergent nozzles. The class of supercritical flows is considered, in which the gas velocities in the jet downstream from the throat are supersonic. The subsonic region of the flowfield is solved in the hodograph plane by a finite-difference method. The supersonic region is solved in the physical plane by the method of characteristics. The stream function distribution on the sonic line is adjusted iteratively to match the boundary conditions at the lip and free streamline. Discharge coefficients are evaluated and truncation errors in the results are considered.
TL;DR: In this article, the authors measured the initial rates of depressurization generated within ductile steel pipes in pneumatic rupture tests and showed that for short initial defects, a significant breach does not develop until the defect has propagated axially to a length of the order of two pipe diameters.
Abstract: Measurements are presented of the initial rates of depressurization generated within ductile steel pipes in pneumatic rupture tests. The breach was initiated by failure of an axial, part-through, flat-bottomed defect machined in the outer surface of the pipe.The measured depressurization rates for supercritical defects are shown to be in agreement with values predicted by a theoretical model which assumes that the pipe hinges open. Where the initial defects are longer than two pipe diameters, the extent of the hinging section is defined by the initial defect length. For short initial defects, a significant breach does not develop until the defect has propagated axially to a length of the order of two pipe diameters, and hence the effective hinging length is two pipe diameters Initial depressurization rates for subcritical defects correlate with the Folias bulging parameters.
TL;DR: Numerical solutions of the two-dimensional, Navier-Stokes equations are presented for boundary conditions corresponding to the laminar flow of Newtonian and non-Newtonian fluids in a round tube with axisymmetric constrictions.
Abstract: Numerical solutions of the two-dimensional, Navier-Stokes equations are presented for boundary conditions corresponding to the laminar flow of Newtonian and non-Newtonian fluids in a round tube with axisymmetric constrictions. The influence of Reynolds number, blockage diameter ratio and length on the velocity components, streamlines, local shear stress and pressure drop are quantified and, in the case of the first two, shown to be large. The non-Newtonian stress-strain relationship corresponds to that for blood flowing in venules and results in an increased recirculation length and larger regions of high shear stress.
TL;DR: In this article, a mathematical model for predicting the crack-formation life of components is proposed, which allows for the effects of mean stresses and strains and is dependent upon the determination of local material behaviour.
Abstract: This paper discusses the parameters likely to influence the crack-formation life of components. In particular, the relationship between the fatigue life of plain and notched specimens is considered, and a mathematical model for predicting the crack-formation life of components is proposed. This allows for the effects of mean stresses and strains and is dependent upon the determination of local material behaviour. The approach is original in that it makes allowances for the influence of the degree of plasticity around a notch, represented in terms of the strain gradient. The Neuber method is evoked, suitably modified to allow for strain gradient effects, and strain gradients are estimated by differentiating Neuber's rule in the immediate vicinity of the notch.Experimental studies have been conducted to determine strain distributions, strain gradients and cyclic lives, and the results compared with predicted values; correlation is good.
TL;DR: In this paper, a new finite-difference technique, designated EMIT, is presented for calculating flows that are parabolic (that is, boundary-layer type) in some regions and elliptic in others without recirculation.
Abstract: A new finite-difference technique, designated EMIT, is presented for calculating flows that are parabolic (that is, boundary-layer type) in some regions and elliptic in others without recirculation. The technique uses velocities and pressure as the dependent variables, and employs a marching procedure in all regions of the flow, wherein calculations are made along only one plane of the flow domain at a time, and the entire planes are visited in an ordered sequence. An application of the method is made to the plume in calm, stably-stratified surroundings. For this test case, a comparison is made between the EMIT and the SIMPLE procedure of Patankar and Spalding, and the EMIT algorithm appears to be more efficient than SIMPLE.
TL;DR: In this article, a method of electroforming smooth, bright, iron-nickel alloy foil, of thickness about 0.1 mm, is developed, where the electrolyte, mainly a solution of ferrous chloride and nickel chloride, is operated at a temperature of 95 °C, and at current densities of between 5 and 20 A/dm2.
Abstract: A method of electroforming smooth, bright, iron-nickel alloy foil, of thickness about 0.1 mm, is developed. The electrolyte, mainly a solution of ferrous chloride and nickel chloride, is operated at a temperature of 95 °C, and at current densities of between 5 and 20 A/dm2. Below that temperature, and at current densities greater than 20 A/dm2, the foil becomes cracked. The amount of nickel co-deposited in the alloy can be increased up to a limit of 6.24 per cent, by reducing the current density and/or increasing the concentration of nickel chloride in the electrolyte. As the nickel content of the foil rises, the material suffers increasingly from hydrogen embrittlement. The main mechanical properties of the alloy foil are more affected by hydrogen embrittlement, the amount of which is influenced by current density and the concentration of nickel chloride, than by changes in grain size. This behaviour is in contrast with that of electroformed iron foil, for which the mechanical properties are largely cont...