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Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1969"


Journal ArticleDOI
TL;DR: In this article, a method is described which uses changes of apparent dynamic modulus and damping during fatigue cycling, for estimating accurately the fatigue lives of stainless steel (Rex 535) specimens.
Abstract: A method is described which uses changes of apparent dynamic modulus and damping during fatigue cycling, for estimating accurately the fatigue lives of stainless steel (Rex 535) specimens This technique for estimating well in advance of failure the fatigue lives of individual specimens avoids the usual difficulties caused by scatter of fatigue results, and has enabled a more precise quantitative investigation to be made of cumulative fatigue damage (ie damage due to multi-level loading) than would have been possible using conventional experimental methods By estimating the remaining life of a specimen at one stress amplitude before measuring the equivalent remaining life at a second stress amplitude by cycling to failure, it was possible to determine lines of equal damage on a plot of stress amplitude versus remaining fatigue life These lines of equal damage were used to predict the fatigue lives of specimens subjected to programmes of multi-level loading, and the accuracy of these estimates, when co

825 citations


Journal ArticleDOI
TL;DR: In this article, the effect of squeeze action on the annular clearance spaces of the leakage path of a single mass rotor was analyzed. But the effect on the acceleration of the bearing and journal surfaces was not considered.
Abstract: In centrifugal pumps, the annular clearance spaces of the leakage path, i.e. impeller seals and balance piston seals, act as powerful hydrostatic bearings with turbulent flow. In the present discussion, the dynamic forces due to these bearings acting on the rotor are analysed, including the effect of squeeze action, i.e. the effect of velocities of separation or approach of the bearing and journal surfaces.Synchronous forced whirling is analysed in a simple idealization comprising a single mass rotor, including the estimation of amplitudes as well as critical speeds. Large damping forces due to squeeze action are found, in qualitative agreement with experimental work by Marcinkowskij and Karincev (3)†. A simplified treatment of the effects of fluid rotation is included in the analysis of rotor vibrations, leading to an analysis of high speed whip instability onset.

120 citations


Journal ArticleDOI
TL;DR: In this paper, measurements of the state and velocity distribution of air in a counterflow vortex tube have been performed to determine the axial variation of the flow quantities, in order to determine axial variations of flow quantities.
Abstract: Measurements of the state and the velocity distribution of air in a counterflow vortex tube have been undertaken. In order to determine the axial variation of the flow quantities, measurements were...

98 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the noise from cold subsonic coaxial jets issuing from concentric nozzles with external mixing and made an attempt to relate the results to the flow patterns of the jets.
Abstract: The noise from cold subsonic coaxial jets issuing from concentric nozzles with external mixing has been examined and an attempt made to relate the results to the flow patterns of the jets. As the velocity of the annular jet was increased in relation to a given central jet velocity, an initial attenuation of the jet noise was observed. On further increasing the annular jet velocity until the velocities of the two streams were nearly equal, the noise was in excess of that of the central jet alone. An attempt has been made to predict the curve relating the attenuation attained to the coaxial jet velocity.In comparing the attenuation produced by a coaxial jet combination with that of a single jet, it could be argued that the total thrust in each case should be the same and experimental results are presented on this basis. Results are also available for a nozzle configuration in which the jets are mixed internally in a tube before discharge, and the paper is completed with the results obtained from an annular ...

93 citations


Journal ArticleDOI
TL;DR: In this article, a procedure for the integration of the full Navier-Stokes equations for constant-property two-dimensional flows is proposed, which is capable of dealing with cases of very high Reynolds number.
Abstract: A procedure is proposed for the integration of the full Navier-Stokes equations for constant-property two-dimensional flows. In contrast with earlier procedures, the present one is capable of dealing with cases of very high Reynolds number. The power of the new procedure is demonstrated in two cases: (1) the square recirculating eddy, for which no solution was previously available for Reynolds numbers larger than about 400, and (2) an impinging jet, for which no solution was available previously. The procedure has also been applied to the square cavity at Reynolds numbers below 400; it gives results of an accuracy comparable with that of previous solutions, but with a smaller computing time.

65 citations


Journal ArticleDOI
TL;DR: In this paper, a simplified linear theory of steady-state curve traversing is developed for bogie and two-axled vehicles based on providing guidance by creep forces in conjunction with wheel conicity, so that flange contact is normally avoided.
Abstract: A simplified linear theory of steady-state curve traversing is developed for bogie and two-axled vehicles. The approach is based on providing guidance by creep forces in conjunction with wheel conicity, so that flange contact is normally avoided. It is shown that this approach is realistic for a wide range of vehicle and track parameters. However, steering by creep forces is limited by the onset of wheel slip. Representative experimental results for a two-axled vehicle are presented.

49 citations


Journal ArticleDOI
TL;DR: In this article, the effectiveness of adiabatic-wall in a two-dimensional, constant-property flow was investigated for a slot of fixed height but with two different slot-lip thicknesses, and the results confirmed the trends exhibited by earlier measurements of the impervious-wall effectiveness.
Abstract: Measurements of adiabatic-wall effectiveness in a two-dimensional, constant-property flow are reported for a slot of fixed height but with two different slot-lip thicknesses. The results confirm the trends exhibited by earlier measurements of the impervious-wall effectiveness which showed that the ratio of slot-lip thickness to slot height, t/yc, is an important parameter in determining the effectiveness of film cooling. The effectiveness is shown to decrease significantly as t/yc is increased beyond a value of 0·25; for lower values, the influence is dependent upon the ratio of slot to free-stream velocities.The influence of the injection angle has also been investigated and measurements of the adiabatic-wall effectiveness are reported for angles of 30, 60 and 90 to the direction of the free-stream. These measurements agree qualitatively with the measurements of Papell but show quantitative differences.

45 citations


Journal ArticleDOI
TL;DR: In this article, the theoretical mode shapes of vibration of pre-twisted rectangular cross-section beams for various width to depth ratios and pretwist angle in the range 0-90° are examined.
Abstract: An important aspect of the theoretical study of the vibrational characteristics of turbine and compressor blading is the prediction of the modal curves from which the stresses along the length of the blading can be determined.The accurate prediction of the modal curves allowing for such factors as pre-twist, camber, size of cross-section, centrifugal tensile effects, aerodynamic effects, etc., is still not possible. However, a better understanding of the effects of some of these parameters can be obtained by a study of the modal curves of relatively simple idealized models. In this work the theoretical mode shapes of vibration of pre-twisted rectangular cross-section beams for various width to depth ratios and pre-twist angle in the range 0-90° are examined.The theoretical results are obtained by the transformation method given by Carnegie, Dawson and Thomas (1)† and the accuracy of these results is verified by comparison with results obtained by Dawson (2) using the Ritz method. The theoretical results a...

41 citations


Journal ArticleDOI
TL;DR: Yet another set of dimensionless variables is offered that have the advantage of the Blok groups, that all results can be plotted on a single graph, but in addition one group is of secondary impo...
Abstract: Yet another set of dimensionless variables is offered. These have the advantage of the Blok groups, that all results can be plotted on a single graph, but in addition one group is of secondary impo...

40 citations


Journal ArticleDOI
TL;DR: In this paper, a mathematical model is set up to predict the deflection of a flow passing obliquely through a plane gauze, which differs from existing descriptions in accounting consistently for velocity variations in the deflecting flow, and in relating deflection at the gauze to the total deflection in a more realistic way.
Abstract: A mathematical model is set up to predict the deflection of a flow passing obliquely through a plane gauze. It differs from existing descriptions in accounting consistently for velocity variations in the deflecting flow, and in relating the deflection at the gauze to the total deflection in a more realistic way. The deflection at the gauze is specified in two ways, as being half the total, and as equalling the total. These two relations are found to represent the performance of gauzes whose solidities are, respectively, less than and greater than one-half. Formulae are developed which predict the flow deflection with good accuracy for these two regimes.

38 citations


Journal ArticleDOI
TL;DR: In this article, the aerodynamic forces of incipient flutter were modeled using wind tunnel model vibratory response under steady wind and used to predict the torsional flutter of the original Tacoma Narrows bridge.
Abstract: Certain coefficients are designated, in the analytical formulation of the suspension bridge flutter problem, to provide for the aerodynamic forces of incipient flutter. A method is given for evaluating these coefficients through observation of wind tunnel model vibratory response under steady wind. Use of the method successfully reproduces the classical flutter aerodynamic coefficients of an aerofoil. When flutter coefficients are obtained by it for a model of the original Tacoma Narrows bridge, the method successfully predicts the incipient torsional flutter characteristic of this well-known structure. The paper also discusses the roles of model and prototype damping and the aerodynamic representativeness of section models relative to the full bridge.

Journal ArticleDOI
TL;DR: In this article, a detailed analysis of a flow-compensated, two-stage, four-way, closed-ports electrohydraulic flow-control valve is given, where electromagnetic forces generated by the torque motor, impedance of the motor coil, inertia of the flapper, viscous damping forces, spring forces, pressure feedback forces, and leakage flow are considered.
Abstract: A detailed analysis is given of a flow-compensated, two-stage, four-way, closed-ports electrohydraulic flow-control valve Factors considered in the analysis of the first stage include: the electromagnetic forces generated by the torque motor, impedance of the motor coil, inertia of the flapper, viscous damping forces, spring forces, pressure feedback forces, and leakage flow Factors considered in the analysis of the second stage include the acceleration force on the spool, viscous friction forces, restraining spring forces, flow reaction forces, leakage flow, and the compressibility of the oilExperimental verification of the analytical work is included

Journal ArticleDOI
TL;DR: In this article, the effect of stress or strain cycling, dwell periods, temperature, notches, environment, multiaxial stress, ductility, and effect of prior testing on subsequent endurance are discussed.
Abstract: Many components in supersonic aircraft and modern power plant operate under cyclic conditions at increased temperatures at which creep processes also occur. Solving associated material problems depends, to a major extent, on understanding the various factors influencing behaviour, such as the effect of stress or strain cycling, dwell periods, temperature, notches, environment, multiaxial stress, ductility, and the effect of prior testing on subsequent endurance. The various methods of testing are briefly described and the mode of failure where there is interaction between creep and fatigue is discussed. Methods for predicting deformation and life are also presented. Finally, the review concludes with suggestions for future work.

Journal ArticleDOI
R. Hooke1
TL;DR: In this article, an approximate analysis of the large deflection elastic behavior of clamped, uniformly loaded, rectangular plates is carried out using a perturbation method using a general form which allows the behaviour of a plate having any particular value of aspect ratio to be predicted.
Abstract: An approximate analysis of the large deflection elastic behaviour of clamped, uniformly loaded, rectangular plates is carried out using a perturbation method. The solutions obtained are presented in a general form which allows the behaviour of a plate having any particular value of aspect ratio to be predicted. The predictions of the present solutions are compared with those of existing solutions where these are available.

Journal ArticleDOI
TL;DR: In this article, the analysis of a proportional controlled pneumatic servomechanism has been extended to consider motion about any initial position along the stroke, and it is shown that there is an inherent damping effect which is dependent upon position.
Abstract: The analysis of a proportional controlled pneumatic servomechanism has been extended to consider motion about any initial position along the stroke. It is shown that there is an inherent damping effect which is dependent upon position and this supports previously published experimental work.

Journal ArticleDOI
TL;DR: In this paper, a theoretical analysis is presented for the problem of flat rectangular plates undergoing large deflections due to the action of a uniform lateral pressure or combinations of uniform lateral pressures and compressive edge loading.
Abstract: A theoretical analysis is presented for the problem of flat rectangular plates undergoing large deflections due to the action of a uniform lateral pressure or combinations of uniform lateral pressure and compressive edge loading. The governing partial differential equations are replaced by their finite difference equivalents and the resulting difference equations solved by over-relaxation using an I.C.T. 1905 computer.The results for plates subjected to lateral loads only are in good agreement with the few existing solutions. For plates subjected to lateral loads and combinations of lateral and edge loading, the results show good agreement with the results of an experimental programme carried out at the University of Strathclyde.

Journal ArticleDOI
TL;DR: In this paper, the location of the inversion locus (mu) was defined for the first time with some precision in the temperature range 0-100cC and a higher inversion temperature was indicated.
Abstract: Equations specifying the dynamic viscosity of compressed water and steam are presented. In the temperature range 0-100cC the location of the inversion locus (mu) is defined for the first time with some precision. The low pressure steam results are re-correlated and a higher inversion temperature is indicated than that previously accepted. From 100 to 600°C values of viscosity are derived up to 3·5 kilobar and between 600 and 1500°C up to 1 kilobar. All the original observations in the gaseous phase have been corrected to a consistent set of densities and deviation plots for all the new correlations are given.Although the equations give values within the tolerances of the International Skeleton Table it is clear that the range and tolerances of the latter could with some advantage be revised to give twice the existing temperature range and over 10 times the existing pressure range at low temperatures. A list of the observations used and their deviations from the correlating equations is available as a sepa...

Journal ArticleDOI
TL;DR: In this paper, a theoretical model is derived which shows that flow measurement errors of up to 5 per cent can result if turbine flowmeters are subjected to changes in upstream velocity profiles, and this theory is then used to show how proper meter design can considerably reduce these errors.
Abstract: A theoretical model is derived which shows that flow measurement errors of up to 5 per cent can result if turbine flowmeters are subjected to changes in upstream velocity profiles. This theory is then used to show how proper meter design can considerably reduce these errors. Experiments in a 50·8 mm (2 inch) diameter pipe, with water as the working fluid, were made to confirm the model and the suggested design improvements. The test results show good correlation with theory.

Journal ArticleDOI
TL;DR: In this paper, the overall damping of freely supported uniform beams of circular and rectangular sections was investigated and it was shown that the loss factor is, beyond a certain stage, highly frequency dependent but that this dependency largely disappears when the experiment is carried out in vacuo.
Abstract: Experimental results on the overall damping of freely supported uniform beams of circular and rectangular section are reported. These results show that the loss factor is, beyond a certain stage, highly frequency dependent but that this dependency largely disappears when the experiment is carried out in vacuo. The frequency dependency is shown to be due to acoustic radiation from the beam. Theoretical results using an approximate theory for rectangular sections agree well with the observed values. Over a certain frequency (wavelength) region the acoustic damping may be many times the internal damping of the beam for the material tested (mild steel).

Journal ArticleDOI
B. N. Cole1
TL;DR: In this paper, it is shown how to reclaim a large proportion of the lost pressure capacity by use of a cross-bore which is either elliptical in section, or, more conveniently, round but offset from a diametral centre-line.
Abstract: It is frequently necessary to drill a cross-bore through the wall of a cylindrical pressure vessel, and it tends to be taken for granted that the cross-bore—itself of circular section— should lie along a diameter of the main cross-section. The weakening effect of such a hole is well known, and reduces the safe working pressure down to 2/5 of the value for the undisturbed cylinder in the case of a Tresca material, or nearly down to 1/3 in the case of a von Mises material. The paper shows how it is possible to reclaim a large proportion of the ‘lost’ pressure capacity by use of a cross-bore which is either elliptical in section, or, more conveniently, round but offset from a diametral centre-line. Such procedure could thus also greatly improve the fatigue life of the pressure vessel.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the factors affecting cage and roller slip in high-speed roller bearings using several lubricants and compared the theoretical evidence with existing theoretical evidence to improve the correlation between theory and practice further theoretical results of cage and roll-bar motion are obtained for bearing conditions relevant to the regime where the fluid pro-properties are pressure dependent.
Abstract: This paper describes the start of an investigation into the factors affecting cage and roller slip in high-speed roller bearings. Cage and roller speeds, for different radial clearances, are measured over a range of steady radial loads and shaft speeds, using several lubricants. These results are analysed and compared with existing theoretical evidence. To improve the correlation between theory and practice further theoretical results of cage and roller motion are obtained for bearing conditions relevant to the regime where the fluid pro-perties are pressure dependent. The theoretical extent of cage and roller slip shows only a fair agreement with the experimental findings. However, the load below which cage slip will occur is much more accurately forecast.

Journal ArticleDOI
TL;DR: In this paper, the lateral motion of a multi-degree-of-freedom shaft with cross-sectional asymmetry having common principal planes, mounted on asymmetrically flexible bearings having fixed common principal plane, is analyzed in terms of a generating system consisting of a symmetric shaft with the mean crosssectional rigidity mounted on the asymmetric bearings.
Abstract: The lateral motion of a multi-degree-of-freedom shaft with cross-sectional asymmetry having common principal planes, mounted on asymmetrically flexible bearings having fixed common principal planes, is analysed in terms of a generating system consisting of a symmetric shaft with the mean cross-sectional rigidity mounted on the asymmetric bearings. Equations of motion are developed in terms of the principal co-ordinates and modes of the generating system, the shaft asymmetry producing coupling terms with periodic coefficients. The equations are solved by the perturbation-variation method of Hsu, leading to simple explicit formulae for instability bands in many practically important cases. The solutions are limited to small shaft asymmetry; any degree of bearing asymmetry is admissible.

Journal ArticleDOI
TL;DR: In this paper, the deformation of wedge-shaped model asperities, supported on rigid bases, is examined and the effect of displaced material on deformation pressure and on the rate of fluid leakage between the contacting surfaces is taken.
Abstract: The gas flow between two surfaces in contact is affected by the way in which the surface asperities are deformed by the contact load. The plastic deformation of wedge-shaped model asperities, supported on rigid bases, is examined. Full account is taken of the effect of displaced material on the deformation pressure and on the rate of fluid leakage between the contacting surfaces. Characteristics of deformation pressure versus compression are plotted for a range of wedge asperity angles, assuming two-dimensional deformation and non-hardening material, and from these are derived expressions for fluid leakage between the contacting surfaces. It is shown that a critical contact pressure exists for a given seal contact load at which the leakage rate has a maximum value. This contact pressure may be avoided by either increasing or decreasing the seal length.

Journal ArticleDOI
TL;DR: In recent years, increasing interest in the mechanics of grinding as a metal cutting process has resulted in a considerable step forward in understanding the fundamental parameters, though no compl....
Abstract: In recent years, increasing interest in the mechanics of grinding as a metal cutting process has resulted in a considerable step forward in understanding the fundamental parameters, though no compl...

Journal ArticleDOI
TL;DR: In this paper, the circumferential average of the source distributions required to represent the blade profiles is considered and the equations of fluid motion are first averaged across the blade passage and the resulting equations solved for the averaged properties.
Abstract: Variations of blade thickness from hub to casing of a turbomachine, which impose a non-uniform blockage upon the meridional flow, often give rise to significant perturbations. In the first part of this paper this effect is simulated by considering the circumferential average of the source distributions required to represent the blade profiles. In the second part the equations of fluid motion are first averaged across the blade passage and the resulting equations solved for the averaged properties.Similarity between the differential equations obtained in these two ways is noted. A number of analytical examples are discussed and a simple experimental result is reported.

Journal ArticleDOI
TL;DR: In this article, the authors performed pressure tests on four thin cylindrical aluminium vessels with circular cutouts and cover plates, and on two vessels with radial branches, and found that the observed limit pressures fit in well with those observed by other workers for vessels of different proportions.
Abstract: Pressure tests were performed on four thin cylindrical aluminium vessels with circular cutouts and cover plates, and on two vessels with radial branches. In all cases a fairly well defined ‘limit pressure’ was observed—corresponding to plastic deformation in the vicinity of the cutout or branch—together with a moderate increase in pressure as deformation proceeded, which may be interpreted as a moderately strong ‘geometry-change effect’.The limit pressures observed for vessels with cutouts agree well with a lower-bound analysis which is described in outline. In general the observed limit pressures fit in well with those observed by other workers for vessels of different proportions. Correlation of geometry-change effects is not so simple, but a fairly clear picture of trends emerges from the study.The question of appropriate geometrical parameters for correlation of results is discussed, and a suggestion is made for taking into account any ‘extra’ cross-sectional area at the junction weld.

Journal ArticleDOI
TL;DR: In this article, an extension of Martensen's method is described which permits an exact solution of the inverse or blade design problem, where an equation is derived for the normal velocity distributed about a given contour when a given tangential velocity is imposed about the contour and from this normal velocity an initial arbitrarily chosen blade shape may be successively modified until a blade is found having a desired surface velocity distribution.
Abstract: An extension of Martensen's method is described which permits an exact solution of the inverse or blade design problem. An equation is derived for the normal velocity distributed about a given contour when a given tangential velocity is imposed about the contour and from this normal velocity an initial arbitrarily chosen blade shape may be successively modified until a blade is found having a desired surface velocity distribution. Five examples of the method are given.

Journal ArticleDOI
TL;DR: In this article, the problem of vortex shedding from parallel rows of circular cylinders of equal diameter set normal to an airstream was considered and the experimental results showed that when the lateral spacing between the axes of two adjacent cylinders is less than two diameters, the flow downstream of the row does not exhibit any obvious single dominant frequency of shedding.
Abstract: This paper deals with the problem of vortex shedding from parallel rows of circular cylinders of equal diameter set normal to an airstream.A single row of cylinders is first discussed. The experimental results show that when the lateral spacing between the axes of two adjacent cylinders is less than two diameters the flow downstream of the row does not exhibit any obvious single dominant frequency of vortex shedding.The flow set up by two rows of cylinders is next considered for both tandem and staggered arrangements of the cylinders. The sets of measured values reported are complete in the sense that they cover the whole range of spacings for which a dominant frequency of vortex shedding could be measured.The Reynolds numbers of these tests correspond to the high subscritical range for a cylinder in isolation.

Journal ArticleDOI
TL;DR: In this paper, the side force produced by the injection of secondary gas into the supersonic regime of a main nozzle is investigated with particular reference to the effect of the angle between the secondary jet and the main nozzle axis.
Abstract: The side force produced by the injection of secondary gas into the supersonic regime of a main nozzle is investigated with particular reference to the effect of the angle between the secondary jet and the main nozzle axis. In the experiments, downstream and upstream injection angles at one secondary port location in the main nozzle were examined. It is shown that there is a definite advantage to be gained by injecting the secondary gas in an upstream direction. An analytical analysis of the results indicates that for moderate secondary mass flows maximum side force is produced when the angle between the axis of the secondary port and the normal to the axis of the main nozzle is in the range 40-50°. When injecting a given secondary mass flow at the angle for maximum side force the axial thrust augmentation is almost zero. As the angle of injection is reduced from upstream values to downstream values the side force reduces and the thrust augmentation increases, indicating that thrust augmentation can be use...

Journal ArticleDOI
TL;DR: In this article, the authors investigated the relationship between flexural vibration of the tines and longitudinal vibration of a symmetric tuning-fork, with particular reference to the effects of the fork mounting.
Abstract: The paper records an investigation of the vibration of a symmetric tuning-fork, with particular reference to the effects of the fork mounting. The relation between flexural vibration of the tines and longitudinal vibration of the fork as a whole is analysed in terms of the coupling induced by unbalanced inertia forces directed parallel to the axis of the stem. It is shown theoretically and confirmed experimentally that longitudinal oscillations can occur at fork frequency and twice fork frequency, and that the fundamental frequency of the fork is affected by the mounting characteristics if there is primary longitudinal unbalance. A method is described whereby the primary component of longitudinal unbalance may be eliminated.