Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1976"
TL;DR: In this paper, the dynamics of pipes conveying fluid is described by means of the Timoshenko beam theory, and the equations of motion are derived and solved by a finite-difference technique, and by a variational method.
Abstract: The dynamics of pipes conveying fluid is described by means of the Timoshenko beam theory. The equations of motion are derived and solved (a) by a finite-difference technique, and (b) by a variational method. It is shown that the latter is the more efficient method.The eigenfrequencies of the system and its stability characteristics are compared with results obtained previously using the Euler-Bernoulli beam theory, and it is shown that in certain cases (e.g. short pipes) the two sets of results diverge. Experiments indicate that the present theory is more successful in predicting the observed behaviour. Furthermore, the present theory shows that, in some cases, cantilevered pipes may lose stability by buckling, whereas previous theories indicate that the system always loses stability by flutter.
55 citations
TL;DR: In this paper, a simple theoretical model, based on the plane strain slip-line field solution for the indentation of a block by opposed flat indenters, is developed to provide an estimate of roll force and torque for profiled rings.
Abstract: Normal pressure distribution, roll force and torque are measured accurately when rolling plain and profiled rings by using the pin-type pressure-transducer technique. A simple theoretical model, based on the plane strain slip-line field solution for the indentation of a block by opposed flat indenters, is developed to provide an estimate of roll force and torque for profiled rings. The driving torque is also predicted by deriving the resultant force and the lever arm. Examination of the results indicates that, in contrast to conventional strip rolling, the normal pressure distribution in ring rolling shows an early peak soon after the entry plane and that conventional friction-hill theory appears inapplicable. Recognizing the appreciable differences in geometry in the roll gap and elsewhere, flat rolling analysis seems generally inappropriate to ring rolling.
50 citations
TL;DR: In this article, the circumstances giving rise to the derailment of a railway wheel set under steady-state rolling conditions are re-examined in the light of recent developments in rolling contact theory.
Abstract: The circumstances giving rise to the incipient derailment of a railway wheel-set under steady-state rolling conditions are re-examined in the light of recent developments in rolling-contact theory. It is found that the problem can be stated in a form which avoids difficulties inherent in most earlier treatments. However, a quantitative solution requires data relating tangential force to creepage and spin in a parameter region previously unexplored. New experimental results are presented which partially correct this lack of data, but more work, both theoretical and experimental, is required.One outcome of the new study is the establishment of the region of applicability of Nadal's classical formula. It shows it to be highly relevant for practical decision-making.
46 citations
TL;DR: In this paper, a method of measuring the dynamic torsion and Young's moduli of a thin film of adhesive is described, and the accuracy of the technique and its suitability for structural adhesives is discussed.
Abstract: A method of measuring the dynamic torsion and Young's moduli of a thin film of adhesive is described. The accuracy of the technique and its suitability for structural adhesives is discussed. Values of modulus obtained using this method are compared with values obtained from static and dynamic tests on bulk specimens of three epoxy adhesives.
41 citations
TL;DR: In this article, the authors investigated the cause of low-speed instability on a large-capacity motorcycle and found that the cause was a fundamental castor instability at the front wheel coupled with a resonance in the upper section of the main frame.
Abstract: Motorcycles are subject to two dynamic steering instabilities, a low-speed ‘flutter’ at 6–8 Hz. and a high-speed ‘weave’ at 2-3 Hz, both of which are increased by adding a tail load, or by decreasing the rider mass. This paper is concerned with the low-speed instability, and describes work which resulted in the elimination of this potentially dangerous phenomenon from a current large-capacity motorcycle.The cause was found to be twofold: a fundamental castor instability at the front wheel, coupled to a resonance in the upper section of the main frame.Recommendations on future frame design are made, and fundamental limitations of the ‘telescopic’ front fork are demonstrated.
39 citations
TL;DR: In this article, the authors compared the performance of conventional hydrodynamic and recessed hydrostatic bearings with slot-entry bearings and showed that a much improved performance can be obtained by using non-return valves in the supply lines.
Abstract: Slot-entry bearings are compared with conventional hydrodynamic bearings and also with recessed hydrostatic bearings. Whereas recessed bearings are not ideal for hybrid operation, improvements in load capacity can be achieved by the use of non-return valves in the supply lines. However, it is shown that a much improved performance may be obtained from slot-entry bearings. Slot-entry bearings have additional advantages of manufacturing simplicity and compactness when compared with other hybrid bearings.Experimental results for recessed bearings and for slot-entry bearings justify computer solutions at moderate values of eccentricity ratio and speed parameters.
35 citations
TL;DR: In this article, the normal pressure distribution in ring rolling shows an early peak soon after the entry plane, i.e. when frictional effects are pronounced, and the technique of incorporating pin-type pressure transducers into the rolls and accurate measurements for various rolling parameters when rolling plain and profiled rings.
Abstract: The technique of incorporating pin-type pressure transducers into the rolls and accurate measurements of the normal pressure are reported for various rolling parameters when rolling plain and profiled rings.Experiments have been carried out using tellurium lead at room temperature to obtain quantitative information about pressure distribution relevant to hot rolling, i.e. when frictional effects are pronounced. The results indicate that, in contrast to conventional strip rolling, the normal pressure distribution in ring rolling shows an early peak soon after the entry plane.
35 citations
TL;DR: The possibility of bearing Babbitt damage arising from transient and steady-state liquid tensile stresses is postulated in this article, where a critical eccentricity ratio has been suggested below which, for a particular clearance, a tensile stress may be generated.
Abstract: Tensile stresses of 740 kN/m2 have been observed in the oil film of a steadily loaded journal bearing. A critical eccentricity ratio has been suggested below which, for a particular clearance, a tensile stress may be generated.An extensive literature survey indicates the sensitivity of the liquid's tensile strength to such factors as gas content, viscosity, particle content and the surface finish at the liquid/bearing material interface.It is suggested that previously attempted observations of liquid tensile stresses in journal bearings may have been limited by the configuration of the pressure-measuring device.The possibility of bearing Babbitt damage arising from transient and steady-state liquid tensile stresses is postulated.
28 citations
TL;DR: In this paper, an approximate solution to the von Karman-type large-deflection equations of unsymmetrically laminated, anisotropic, rectangular plates under uniform transverse load is formulated by the perturbation technique.
Abstract: An approximate solution to the von Karman-type large-deflection equations of unsymmetrically laminated, anisotropic, rectangular plates under uniform transverse load is formulated by the perturbation technique. The membrane boundary conditions are the zero normal and shear boundary forces. By expressing the load, force function and transverse deflection in the form of series, the governing equations and boundary conditions are reduced to a series of linear partial differential equations and boundary conditions. In each approximation a solution is assumed in the form of polynomials which satisfy the associated boundary conditions and physical requirements for deflection and and three membrane forces in unsymmetric cross-ply and angle-ply plates. Taking the first three terms in the truncated series, numerical results are graphically presented for the load-deflection relations, bending moments and membrane forces in unsymmetric cross-ply and angle-ply plates with various values of aspect ratio and total numb...
27 citations
TL;DR: In this paper, it was shown that when there is mechanical coupling between blades through their root fixings, then the maximum factor by which the vibration amplitude can increase due to mistuning is given approximately by 1/2[1 + √(N/2)], where N is the number of blades in the row.
Abstract: It is shown that when there is mechanical coupling between blades through their root fixings, then the maximum factor by which the vibration amplitude can increase due to mistuning is given approximately by 1/2[1 + √(N/2)], where N is the number of blades in the row This contrasts with the factor of 1/2(1 + √N), derived in an earlier paper, due to more general aerodynamic coupling The cases when adjacent blades are excited either in phase or in antiphase are exceptional, and in these cases the earlier analysis applies These factors can be closely approached when just one blade is mistuned
26 citations
TL;DR: In this article, a theory was developed for calculating the wavelength of the waves produced at the welded interface between two identical and explosively projected (flyer) plates using the so-called symmetric welding arrangement.
Abstract: A theory is developed for calculating the wavelength of the waves produced at the welded interface between two identical and explosively projected (flyer) plates using the so-called symmetric welding arrangement. The theory appeals to the analogy between interface wave formation and the formation of a vortex street behind an obstacle in a fluid stream which has been discussed elsewhere (1)‡. It is a notional theory in the sense that the results of an inviscid analysis of jet collision are combined with a semi-empirical vortex shedding theory. In spite of this, the authors believe that it provides a useful first approximation to a more rigorous analysis, and this belief is supported by the agreement found between the theory and certain experimental results obtained from the welding of steel flyer plates.
TL;DR: In this paper, a brief summary of the use of the J contour integral in elastic-plastic finite-element analysis is given, and a more detailed appraisal is made of its interpretation as an energy balance concept in the presence of irreversible plastic deformation.
Abstract: In Part 1, a brief summary of the justification and advantages of the use of the J contour integral in elastic-plastic finite-element analysis is given. A more detailed appraisal is then made of its interpretation as an energy balance concept in the presence of irreversible plastic deformation. Numerical illustration of the points made is provided by an elastic-plastic finite-element analysis on a series of monotonically loaded centre-cracked plates of different 2a/W ratios. With incremental plasticity it is concluded that although an energy balance interpretation can be assigned to J, it is not a release rate of energy available to propagate a fracture. In Part 2, the role of J as a crack-tip characterizing parameter is examined with the help of elastic-plastic finite-element analysis. The evidence indicates that a given value of J does not ensure a unique crack-tip environment for different cracked-body geometries. It may, however, characterize the crack tip adequately for some engineering purposes and,...
TL;DR: In this paper, an analytical and experimental study of axial compressor-diffuser interaction in circumferentially non-uniform flow is presented, based on an inviscid rotational core flow plus the use of a diffuser effective area ratio to account for boundary layer blockage.
Abstract: An analytical and experimental study of axial compressor-diffuser interaction in circumferentially non-uniform flow is reported. An analysis of non-axisymmetric flow in an annular diffuser is presented, based on an inviscid rotational core flow plus the use of a diffuser effective area ratio to account for boundary layer blockage. The analysis is applied to the prediction of the diffuser flow field associated with the presence of a circumferential total pressure distortion. It is found that large static pressure non-uniformities can exist at the inlet of diffusers that are short compared with their mean circumferences, as is usually the case in turbomachinery applications. The analysis is coupled to an asymmetric compressor flow field prediction to provide a method for calculating the effect of an exit diffuser on compressor performance with distortion. It is shown that the velocity defect seen by the compressor can be substantially increased by the presence of the diffuser.The experiments were directed a...
TL;DR: In this article, an expression for the steady forced response of a system governed by the equationin which A, B and C are real but not symmetric is derived, which is effectively an adaptation and exploration of the theory.
Abstract: An expression is derived for the steady forced response of a system governed by the equationin which A, B and C are real but not symmetric. The theory is effectively an adaptation and exploration o...
TL;DR: In this paper, a creep analysis of a thick-walled anisotropic cylinder subject to combined internal and external pressures is presented, where the elastic strains are also taken into account.
Abstract: A creep analysis of a thick-walled anisotropic cylinder subject to combined internal and external pressures is presented. The elastic strains are also taken into account. By considering the creep r...
TL;DR: In this article, the properties of iron foil have been investigated for current densities of 10 to 30 A/DM2, provided that the electrolyte temperature is above 85°C.
Abstract: Iron foil, ranging in thickness from 0.05 to 0.16 mm, has been prepared by electrodeposition with an electrolyte solution composed mainly of ferrous chloride. Bright, smooth foil is obtained for current densities of 10 to 30 A/dm2, provided that the electrolyte temperature is above 85°C. Techniques developed to measure the mechanical properties of such a thin material are discussed. Unlike conventionally produced foil, the values of the main mechanical properties of the electrodeposited material, e.g. tensile strength and hardness, increase with decreasing thickness. The properties can also be affected by the main process variables: for instance, the lower the electrolyte temperature, the higher is the tensile strength. These effects are explained in terms of changes in grain size of the foil which are largely influenced by the process variables.
TL;DR: In this paper, the introduction of a small transverse opening or cross-bore into the wall of a cylindrical pressure vessel is sometimes necessary, and it is shown that under cyclic stress conditions, the fatigue life of the vessel is severely reduced.
Abstract: The introduction of a small transverse opening or cross-bore into the wall of a cylindrical pressure vessel is sometimes necessary. Under static conditions such a cross-bore may have little effect on the bursting pressure of a plain cylinder, but under cyclic stress conditions, the fatigue life of the vessel is severely reduced. If the cross-bore axis is offset from the radial centre-line of the cylinder, then the fatigue life of such a vessel is shown to be substantially greater than that of a similar vessel containing a radial cross-bore.
TL;DR: In this article, the effect of transverse shear deformation on the bending of simply supported, circular, cylindrical plates consisting of cross-ply laminates with arbitrary sequences of 0° and 90° plies was investigated.
Abstract: The paper deals with the transverse bending of simply supported, circular, cylindrical plates consisting of cross-ply laminates with arbitrary sequences of 0° and 90° plies. The analysis is carried out within the framework of laminated-plate theory and shallow-shell theory, where the effect of transverse shear deformation is considered. The non-dimensional deflection parameters are computed for panels consisting of antisymmetric graphite-epoxy plies. The influence of the coupling between bending and extension, the plate curvature and the aspect ratio are studied and discussed.
TL;DR: In this paper, a theoretical model of electroforming, which includes the effects of current efficiency and periodic reversal of polarity, is derived by a perturbation procedure for a case where a metal layer is formed upon a mandrel-electrode carrying sinusoidal irregularities on its surface.
Abstract: A theoretical model of electroforming, which includes the effects of current efficiency and periodic reversal of polarity, is derived. The model is analysed by a perturbation procedure for a case where a metal layer is formed upon a mandrel-electrode carrying sinusoidal irregularities on its surface. Analytic solutions of the resulting equations are shown to be so complicated that numerical methods offer the best means of solution. The latter methods are therefore used to demonstrate how the achievement of a uniform thickness for the layer is influenced by the time intervals of the polarity-cycle and the current efficiencies for deposition and dissolution. Extensions of the model to cover arbitrarily shaped surfaces on the mandrel are shown to impose limitations on the amplitude of the irregularities that can be so treated.
TL;DR: In this paper, predictions of the swirling, recirculating, turbulent flow between a rotating and a stationary shrouded disc with an axial source flow were made using a two-dimensional finite-difference procedure.
Abstract: Predictions were made of the swirling, recirculating, turbulent flow between a rotating and a stationary shrouded disc with an axial source flow. A two-dimensional finite-difference procedure was used. Turbulent transport processes were calculated with the aid of a turbulence model involving the solution of two differential equations.Comparison of predicted disc torque with experimental data showed good agreement. Details of the predicted flow between the discs are presented and shown to be plausible; they also highlight the need for detailed hydrodynamic measurements in these types of flows to aid more rigorous testing of the method.
TL;DR: In this paper, a linear stability analysis is used to examine the influence of axial length, axial Reynolds number and annulus radius ratio on the critical Taylor number for neutral stability when the axial velocity is assumed uniform.
Abstract: The stability of developing tangential flow induced by the imposition of an axial velocity on the tangential velocity distribution created by core rotation is theoretically and experimentally investigated. A linear stability analysis is used to examine the influence of axial length, axial Reynolds number and annulus radius ratio on the critical Taylor number for neutral stability when the axial velocity is assumed uniform. Predictions compare favourably with measurements obtained by hot-wire anemometer for air flowing in an annulus of radius ratio 0·9, particularly at small Reynolds number and large values of the axial length parameter.
TL;DR: Theoretical studies of various model systems, in which the direct effect of the roughness of the surfaces on the hydrodynamics has been ignored, show that the systems remain thermally stable under the most realistic assumptions made in the various models as discussed by the authors.
Abstract: Asperity interactions in the inlet zone of an elastohydrodynamic system may increase the local temperatures in that zone and cause a significant decrease in the minimum thickness of the lubricant film.Theoretical studies of various model systems, in which the direct effect of the roughness of the surfaces on the hydrodynamics has been ignored, show that the systems remain thermally stable under the most realistic assumptions made in the various models. It is therefore unlikely that the mechanism studied is that of scuffing.
TL;DR: In this article, it was shown that for two members having a ratio of principal axes equal to 2.0, being of equal weight and subjected to the same maximum stress level, the member with varying radial thickness will withstand an applied pressure which is just over forty per cent higher than that carried by the traditional constant-thickness member.
Abstract: Radial thickness function is represented by the first two terms of an even Fourier series and the unknown coefficient in the function is determined from the constraint: ‘maximum amplitude of stress in the member must be restricted to the minimum value possible’.Using this technique, it is shown that for two members having a ratio of principal axes equal to 2.0, being of equal weight and subjected to the same maximum stress level, the member with varying radial thickness will withstand an applied pressure which is just over forty per cent higher than that carried by the traditional constant-thickness member. Alternatively, for equality in pressure loading and maximum stress level, the ratio of weights for the two members is 0.844, in favour of the variable-thickness member.
TL;DR: In this paper, an analysis of the immiscible liquid binary Rankine cycle using aqueous/perfluorocarbon binaries has been carried out and it has been shown that the cycle is characterized principally by the volatility of its organic component.
Abstract: An analysis of the immiscible liquid binary Rankine cycle using aqueous/perfluorocarbon binaries has been carried out. Six such binaries have been studied and it has been shown that the cycle is characterized principally by the volatility of its organic component. The cycle performance has been compared with that of promising pure organic working fluid cycles. Although having generally lower efficiency than the optimum organic pure fluid cycle, practical considerations may favour the binary cycle at the bottom end of the Rankine cycle power range.
TL;DR: In this article, the authors compared the creep rupture lifetime under constant uniaxial tensile load according to various theories, including purely ductile and purely brittle mechanisms, as well as some recently proposed combined mechanisms of failure.
Abstract: Predictions of the creep rupture lifetime under constant uniaxial tensile load according to various theories are compared. Both purely ductile and purely brittle rupture mechanisms are included as well as some recently proposed combined mechanisms of failure.One of these latter mechanisms is shown to yield results which describe quite well the dependence of the creep rupture lifetime on load in the entire region from instantaneous, usually rather ductile, rupture at high loads to long delayed, usually rather brittle, creep rupture at smaller loads.
TL;DR: In this article, a technique for visualizing the air flow over a surface by means of an oil film is described, which is used in conjunction with experimentally determined flapperplate pressure profiles to examine the flow characteristics of a flapper-nozzle valve used to control air at 425 kPa (4.25 bar).
Abstract: A technique is described for visualizing the air flow over a surface by means of an oil film. The technique is used in conjunction with experimentally determined flapper-plate pressure profiles to examine the flow characteristics of a flapper-nozzle valve used to control air at 425 kPa (4.25 bar). The oil film shows clearly the points of separation and reattachment of the air boundary layer resulting from shock wave and boundary layer interaction.Possible applications of the technique are discussed and attention is focused on the use of the oil-film technique in conjunction with interferometry as a tool for the rapid determination of the effects caused by changes in nozzle geometry.
TL;DR: In this article, a small-perturbation analysis is developed to express the unsteady-state continuity-of-flow equation for an isolated recess in a passively compensated, multirecess, hydrostatic journal bearing in terms of generalized co-ordinates.
Abstract: A previously established small-perturbation analysis is developed to express the unsteady-state continuity-of-flow equation for an isolated recess in a passively compensated, multirecess, hydrostatic journal bearing in terms of generalized co-ordinates. The concise form of this equation enables motion of the shaft about the concentric position to be described by equations which are derived in closed form for bearings with orifice, capillary or constant flow compensation and any number of recesses.These equations of motion, and hence the expressions for the receptances which describe the response of a bearing to external excitation, are shown to be of exactly the same form for all bearings of the type considered. Furthermore, the damping ratio and natural frequency in any particular case are determined by a single dynamic constant which is shown to be equal to a linear combination of circular functions and a limited number of coefficients which may be found explicitly by routine use of signal flow graphs.T...
TL;DR: In this article, the one-dimensional equations of surge in centrifugal compressors are solved graphically for the pressure head and mass flow rate as functions of time for a variety of situations, and the results are discussed in terms of the acoustical properties of the external piping.
Abstract: The one-dimensional equations of surge in centrifugal compressors are solved graphically for the pressure head and mass flow rate as functions of time for a variety of situations, and the results are discussed in terms of the acoustical properties of the external piping. Two important parameters affecting the nature of the surge limit cycle are found to be simply related to the acoustic capacitance and acoustic inductance of the system.
TL;DR: In this article, a new equation describing recovery creep is proposed, where e is the strain and is the eventual steady creep rate, where r is the recovery rate and h is the hardening coefficient.
Abstract: A new equation describing recovery creep is , where e is the strain and is the eventual steady creep rate. From one form of the equation, namely , the McVetty-Garofalo, two forms of logarithmic, and Andrade creep equations are obtained with n = 1,2, and 5/2 respectively. From another form, namely , Li's, Akulov's and McLean's equations are obtained. These and other equations which are obtained are thus systematically related to each other. The physical bases of several derivations are also shown to be similarly related.During the deceleration from the initial creep rate to the final rate , there develops not only a balance between the rate of recovery, r, and the strain hardening coefficient, h, so that , but also a decrease in r and an increase in h which prolongs primary creep. This paper shows how to take into account the changes in r and h, and that equations which do so, whether implicitly or explicitly, describe experimental creep strain/time curves quite well.It is thus shown that behind the presen...