Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1980"
TL;DR: In this paper, the natural transition of boundary layers is investigated for a flat plate in a low-speed wind tunnel with free-stream turbulence intensities ranging from 0.3 to 5 per cent.
Abstract: Natural transition of boundary layers is investigated for a flat plate in a low-speed wind tunnel with free-stream turbulence intensities ranging from 0.3 to 5 per cent, and with pressure-gradient ...
727 citations
TL;DR: In this article, a finite-difference numerical procedure incorporating a buoyant version of the k-e turbulence model was employed to compute turbulent mixed convection in a square cavity for Reynolds number Re = 1.
Abstract: A finite-difference numerical procedure, incorporating a buoyant version of the k-e turbulence model, is employed to compute turbulent, mixed convection in a square cavity for Reynolds number Re =1...
76 citations
TL;DR: A theoretical approach is described which overcomes the problems of convergence previously associated with obtaining solutions of the elastohydrodynamic equations for a reciprocating, rectangular section rubber seal and is suitable both for instrokes and outstrokes at realistic sealed pressures.
Abstract: A theoretical approach is described which overcomes the problems of convergence previously associated with obtaining solutions of the elastohydrodynamic equations for a reciprocating, rectangular section rubber seal. Convergence of this method is extremely rapid. Results are presented which illustrate that it is suitable both for instrokes and outstrokes at realistic sealed pressures. Experimental measurements of pressure distribution are presented for comparison.
56 citations
TL;DR: In this paper, the radial stiffness of rolling element bearings under oscillating conditions is measured using a simple rig, which is very simple in principle and allows the measurement of the radial stiffness of a pair of bearings.
Abstract: There is very little information available on the characteristics of rolling element bearings under oscillating conditions. This is because of the difficulty that has been experienced in measuring the relevant characteristics. A rig is described which is very simple in principle and allows the measurement of the radial stiffness of a pair of bearings. For the angular contact bearings tested the levels of damping obtained are larger than previously expected.
48 citations
TL;DR: In this paper, the conditions at a general idealized revolute joint, with clearance but with no hydrodynamic lubrication present, were derived, and a series of numerical solutions of the equations were used to predict the conditions under which contact is lost, leading to impacts.
Abstract: Equations are derived that describe the conditions at a general idealized revolute joint, with clearance but with no hydrodynamic lubrication present. The equations are governed by three dimensionless parameters that depend on the nominal motion, mass distribution and influence coefficients of the linkage in which the joint appears, as well as the clearance magnitude. A series of numerical solutions of the equations is used to predict the conditions under which contact is lost, leading to impacts. The results are presented in the form of a design chart and the implications are discussed.
48 citations
TL;DR: In this article, closed-form and finite-element solutions are presented for thermal bending and stretching of laminated composite plates, where the material of each layer is assumed to be elastically and thermo-elastic orthotropic and bimodular, having different properties depending upon whether the fiber-direction normal strain is tensile or compressive.
Abstract: : Closed-form and finite-element solutions are presented for thermal bending and stretching of laminated composite plates. The material of each layer is assumed to be elastically and thermoelastically orthotropic and bimodular, i.e., having different properties depending upon whether the fiber-direction normal strain is tensile or compressive. The formulations are based on the thermoelastic version of the Whitney-Pagano laminated plate theory, which includes thickness shear deformations. Numerical results are obtained for deflections and neutral-surface positions associated with normal strains in both of the in-plane coordinates. The closed-form and finite-element results are found to be in good agreement. (Author)
41 citations
TL;DR: In this paper, a general scheme for including effects of elastic deformation, finite geometry changes, and strain rate sensitivity in a simple approximate scheme for estimating maximum transient and permanent deformations in structures subjected to load pulses of high intensity.
Abstract: A general scheme is proposed for including effects of elastic deformation, finite geometry changes, and strain rate sensitivity in a simple approximate scheme for estimating maximum transient and permanent deformations in structures subjected to load pulses of high intensity. The method is applied here to fully clamped beams of mild steel subjected to explosive loading. Comparisons are made between estimates from the present method and test results, as well as with estimates by various rigid-plastic methods and (to a limited extent) with results from numerical methods.
41 citations
TL;DR: A method of prediction of transient behaviour is presented and applied to variable speed cutting on a lathe where such transients are significant and under certain conditions larger transient vibrations occur.
Abstract: Conventionally the stability analysis of machine tools is restricted to determining if a particular operation will become unstable. The transient behaviour is not examined in any further detail. However, under certain conditions larger transient vibrations occur even though the process may ultimately be stable. A method of prediction of transient behaviour is presented and applied to variable speed cutting on a lathe where such transients are significant.
34 citations
TL;DR: In this article, an experimental investigation of subsonic turbulent swirling flows through annular diffusers having diverging hub and casing boundaries has been conducted, where the static pressure distributions and the axial and tangential velocity profiles were measured with the help of a three-hole cobra probe suitably mounted at different cross sections along the diffuser length.
Abstract: Annular diffusers are likely to operate with varying amounts of swirl at the inlet. The work described in this paper is concerned mainly with an experimental investigation of subsonic turbulent swirling flows through annular diffusers having diverging hub and casing boundaries. The test facility was designed SO as to peImit different levels of inlet swirl. The static pressure distributions and the axial and tangential velocity profiles were measured with the help of a three-hole cobra probe suitably mounted at different cross sections along the diffuser length. The diffuser performance parameters such as static-pressure recovery, effectiveness, and the total pressure loss coefficient were then computed from the experimental observations. The behaviour of these parameters has been discussed to establish the effect of swirl. The presence of inlet swirl was found to increase the overall static-pressure recovery. A substantial increase in the pressure recovery occurred over the initial stages of diffusion and...
21 citations
TL;DR: In this article, a closed form analytical solution for the pressure in the lubricating film and the axial separating force is presented, covering the complete range of waviness and coning.
Abstract: A mechanical seal model having face geometry of combined waviness and coning is analysed. A closed form analytical solution for the pressure in the lubricating film and the axial separating force is presented, covering the complete range of waviness and coning. The separating force is found to be linearly dependent on the number of waves and strongly affected by coning. A comparison with a seal model having angular misalignment combined with coning reveals that in both models the separating force is essentially of the same order of magnitude.
19 citations
TL;DR: In this paper, it is demonstrated that rotation about a parallel axis enhances the forced convection heat transfer, and a correlating equation for assessing this effect is proposed, and the results have application for the assessment of heat transfer in certain gas-cooled electrical machine rotors.
Abstract: An investigation of turbulent heat transfer in a revolving square-sectioned tube is reported in this paper. It is demonstrated that rotation about a parallel axis enhances the customary forced convection heat transfer, and a correlating equation for assessing this effect is proposed. The range of parameters covered in the experiments permit the results to have application for the assessment of heat transfer in certain gas-cooled electrical machine rotors.
TL;DR: In this article, the results of laser-Doppler anemometry and calculations with finite-difference solutions of the time-averaged Navier-Stokes equations and a two-equation turbulence model were obtained for the turbulent isothermal flow in an axisymmetric geometry related to gas-turbine combustors.
Abstract: Measurements with laser-Doppler anemometry and calculations with finite-difference solutions of the time-averaged Navier-Stokes equations and a two-equation turbulence model, have been obtained for the turbulent isothermal flow in an axisymmetric geometry related to gas-turbine combustors. The results quantify the flow patterns in the arrangement and demonstrate the extent to which they can be represented by calculation. The discrepancies between measured and calculated results are shown to depend more on the distribution of grid nodes than on the turbulence model. Even with a distribution of nodes which is considered to be near optimum, differences between measurement and calculation exist and are particularly significant in the regions of steep velocity gradient immediately downstream of the incoming annular jet. The general trends are, however, correctly represented, and the calculation method has been used to determine the influence of the width of the annulus and of the jet gap. The results provide i...
TL;DR: In this paper, a study of ventilated gaseous cavitation in a steadily loaded, non-conformal contact has been undertaken, particularly appropriate to what can be called ‘lightly loaded’ situations such as those occurring in radial race seals and certain industrial coating processes.
Abstract: A study of ventilated gaseous cavitation in a steadily-loaded, non-conformal contact has been undertaken. The work is particularly appropriate to what can be called ‘lightly loaded’ situations such as those occurring in radial race seals and certain industrial coating processes. A wide-ranging experimental programme has been carried out and measurements of film rupture location and pressure distributions compared to computer predictions obtained using the cavitation boundary conditions of Coyne and Elrod. Photographic studies are also reported. The boundary conditions due to Coyne and Elrod have been confirmed as appropriate for the experimental conditions studied.
TL;DR: In this paper, it was shown that the curvature of any initially straight line element is proportional to the heat flux across the line element, and a closely related three dimensional result was proved for the sum of the principal curvatures of planes parallel to the faces of an infinite thick plate.
Abstract: It is well known that a simply-connected isotropic elastic body in a state of plane strain and with traction-free boundaries remains free of stress if it is subject to steady-state heat conduction. A recent theorem due to Dundurs shows that in this state the curvature of any initially straight line element is proportional to the heat flux across the line element.A closely related three dimensional result is proved for the sum of the principal curvatures of planes parallel to the faces of an infinite thick plate.These results have certain implications for thermoelastic crack and contact problems. For example: (i) thermal distortion has no effect on the contact pressure distribution at an insulated interface or at an interface between two similar materials, (ii) the thermal stress in a cracked solid depends on the temperature field only through the value of a certain constant related to the average temperature difference across the crack, (iii) steady-state heat flow induces no stresses in an axisymmetric t...
TL;DR: In this paper, the authors determined the pressure distribution, contact arc extent, and deflection for the elastic contact of a long roller and a cylindrical hole in an infinite body.
Abstract: The pressure distribution, contact arc extent, and deflection are determined for the elastic contact of a long roller and a cylindrical hole in an infinite body. It is shown that these variables depend on the degree of conformity of the two bodies and that Hertz's theory should not be used when the arc dimensions are of the same order as the radii of curvature, as its assumptions are violated. When the hole circumference available is reduced, pressure discontinuities can occur where the arc terminates. The results of the analysis have application in the design of some engineering components, such as complete and partial arc bearings and Novikov gears, where a knowledge of the magnitude and distribution of the contact stress is important.
TL;DR: In this paper, the surface roughness of the face of the foil formed adjacent to the cathode, and of that electrode, are similar and the hardness of the reverse anodic face increases with increasing foil thickness, due to the increase in size of the crystal growth sites.
Abstract: Iron foil, of thicknesses between 003 and 0.15 mm has been electroformed at a current density of 30 A/dm2 and an electrolyte temperature of 100°C upon cathodes of surface roughness ranging from 0.04 to 4.4 μm Ra. The surface roughnesses of the face of the foil formed adjacent to the cathode, and of that electrode, are similar. The roughness of the reverse anodic face increases with increasing foil thickness, due to the increase in size of the crystal growth sites. The hardness of the cathodic face of the foil is unaffected by either cathode surface roughness or foil thickness. The hardness of the anodic face increases with both increasing cathode surface roughness and decreasing foil thickness, due to corresponding changes in grain size. A slight net decrease in tensile properties with increasing cathode surface roughness is attributed to the greater amount of stress concentration borne by the rougher foils. Young's modulus for the foil is not affected by cathode surface roughness.The electroforming of fo...
TL;DR: In this paper, the location of both rupture and reformation boundaries in liquid film bearings is important in determining overall performance characteristics, and the problem of determining cavitation interfaces may be trivial or extremely complex depending upon the physical model adopted.
Abstract: The location of both rupture and reformation boundaries in liquid film bearings is important in determining overall performance characteristics. Finite difference approximations have been most widely used in the numerical analysis of hydrodynamic bearings, and the problem of determining cavitation interfaces may be trivial or extremely complex depending upon the physical model adopted. For some situations finite element analysis may offer an advantage and this possibility is investigated here.
TL;DR: In this article, the angle of fold and the plastic work done in folding along a line were examined for a series of cases, such as folding-up into a prism and a frustum, folding on a cylinder along a circular arc, and more generally, folding-on a developed surface along an arbitrary curved line.
Abstract: Under the condition of inextensibility, an initially flat sheet of metal can be folded along straight lines or a curved line to produce various surfaces. The angle of fold and the plastic work done in folding along a line are examined for a series of cases, such as folding-up into a prism and a frustum, folding on a cylinder along a circular arc, and more generally, folding on a developed surface along an arbitrary curved line. Some numerical results are given.
TL;DR: In this article, the axisymmetric problem was extended to the more general case where two spherical particles move in a direction parallel to their line of centres parallel to the axis of a circular cylinder.
Abstract: Numerical values are provided which enable the drag force on the reference spherical fluid or solid particle, and the torque on the reference spherical solid particle, to be computed for the particular case when two spherical particles move in a direction parallel to their line of centres parallel to the axis of a circular cylinder. Results for this motion are also expressed in terms of the ratio of drag forces experienced by (1) the particle of arbitrary shape in a bounded, two particle system, and the particle in an unbounded, two particle system, and (2) the particle in a bounded, two particle system, and the particle moving alone with the same speed and orientation in the same, but unbounded, fluid. The computation furnishes the interaction and wall corrections correctly to the first-order in the ratios of characteristic particle dimension to characteristic distance of the particle from both another particle and from the cylinder wall.The axisymmetric problem was extended to the more general case wher...
TL;DR: In this paper, a semi-analytical study of the influence of inertia terms on the thermohydrodynamic analysis of infinitely wide thrust bearings operating under conditions of laminar and turbulent flow is presented.
Abstract: This paper presents a semi-analytical study of the influence of inertia terms on the thermohydrodynamic analysis of infinitely-wide thrust bearings operating under conditions of laminar and turbulent flow. The momentum and energy equations are not seriously affected by the presence of inertia forces. Results show that the inclusion of inertia terms causes an increase in the fluid film pressure and load-carrying capacity. Thermal effects exert a pronounced influence on bearing performance.
TL;DR: In this paper, the authors considered the squeeze film lubrication process of a cylinder approaching a plane rigid surface covered in a thin elastic layer and presented a simplified lubrication theory, which made the assumption that the shapes of the solids are the same as the elastically deformed surfaces under dry conditions.
Abstract: This paper considers the squeeze film lubrication process of a cylinder approaching a plane rigid surface covered in a thin elastic layer. A simplified lubrication theory is presented, which makes the assumption that the shapes of the solids are the same as the elastically deformed surfaces under dry conditions. The lubrication equations are solved using alternative pressure boundary conditions derived from the dry contact pressure curve. In the experiments, lubricant film thickness is measured using optical interference methods. Curves of film thickness against time are plotted, and the effects on these curves of variations in load and layer thickness are shown to agree with the predictions of the theory.
TL;DR: In this article, the friction factor, load capacity and attitude angle of a plain cylindrical journal bearing with a central, circumferential inlet groove were derived for a simple, empirical theory, which incorporates measured friction factors, gives better agreement with the experimental load capacity results than previous theories.
Abstract: Experimental results are presented, relating to the friction factor, load capacity and attitude angle, for a plain, cylindrical journal bearing with a central, circumferential inlet groove. The length to diameter ratio of the journal bearing was 1/3 and the clearance ratio was 0.011. By the use of various lubricants, including water, Reynolds numbers ranging from 40 to 50 000 were attained. Comparisons with various theoretical predictions are given. It is shown that a simple, empirical theory, which incorporates measured friction factors, gives better agreement with the experimental load capacity results than previous theories.
TL;DR: In this article, the response of a system to external forces is determined by generating matrices, the coefficients of which are functions of the varying parameters, and the original differential equations are then replaced by sets of linear algebraic equations which are solved numerically.
Abstract: The motion of systems in which mass, damping, and stiffness properties are known functions of time is described in terms of time-domain finite elements. The response of such systems to external forces is determined by generating matrices, the coefficients of which are functions of the varying parameters. The original differential equations are then replaced by sets of linear algebraic equations which are solved numerically. Examples of the use of the method are given.
TL;DR: In this article, a first-order perturbation method was adopted to find the dynamic behavior of an aerostatic circular thrust bearing having a central porous insert as a restrictor.
Abstract: A first-order perturbation method is adopted to find the dynamic behaviour of an aerostatic circular thrust bearing having a central porous insert as a restrictor. The linearized gas film stiffness and damping are derived and used to study their behaviour with other design variables.
TL;DR: In this paper, it is shown theoretically that fatigue of a component will result in a failure pattern which consists of an initial period of intrinsic reliability, or near zero failures, followed by a rapid increase in failure rate when loss of fatigue strength becomes operative, to be followed in turn by a period during which the failure rate decreases with time or maybe remains constant.
Abstract: It is shown theoretically that fatigue of a component will result in a failure pattern which consists of an initial period of intrinsic reliability, or near zero failures, followed by a rapid increase in failure rate when loss of fatigue strength becomes operative, to be followed in turn by a period during which the failure rate decreases with time or maybe remains constant. By contrast other wear-out modes involving a continuous loss of strength give rise to a steadily increasing failure rate after the period of intrinsic reliability has expired. Practical examples of each type are quoted to substantiate the theoretical deductions. The interpretation of wear out characteristics by Weibull distributions is discussed.
TL;DR: In this paper, a general analysis of three-dimensional flow through a porous rectangular thrust bearing which incorporates both viscous and inertia permeabilities of the porous media is presented, and solutions for load capacity and flow rate are obtained using standard numerical procedure but introducing a new term ‘the effective permeability’.
Abstract: A general analysis of three-dimensional flow through a porous rectangular thrust bearing which incorporates both viscous and inertia permeabilities of the porous media is presented. Solutions for load capacity and flow rate are obtained using standard numerical procedure but introducing a new term ‘the effective permeability’. It is shown that inertia flow reduces the load capacity and increases the flow rate through the bearing.
TL;DR: In this paper, a solution for tangential tractions developed between two rolling cylinders of identical elastic materials, whose axes are slightly misaligned, is given for the tangent tractions.
Abstract: A solution is given for the tangential tractions developed between two rolling cylinders of identical elastic materials, whose axes are slightly misaligned. A critical misalignment angle is found, above which slip occurs throughout the contact area. For smaller angles, the contact area contains regions of adhesion and microslip. Results are given for the extent of these regions and for the axial force generated due to the misalignment.
TL;DR: In this paper, the problem of hydrogen embrittlement, which adversely affects the quality and mechanical properties of electroformed iron-nickel alloy foil, is considered, and heat treatment, such as annealing, can reduce these effects.
Abstract: Contributions intended for publication as Research Notes should preferably be limited in length to 1000 words and two illustrations, and should be addressed to the Manuscript Section, The Institution of Mechanical Engineers, I Birdcage Walk, Westminster, London SW1H 9JJThe problem of hydrogen embrittlement, which adversely affects the quality and mechanical properties of electroformed iron-nickel alloy foil, is considered. Heat-treatment, such as annealing, can reduce these effects of hydrogen embrittlement. The electroformed metal can also be converted to alloy steel by carburizing; and by other heat-treatments, such as hardening and tempering, a range of mechanical properties for the foil can be achieved.
TL;DR: In this article, a DISA two-colour backscatter laser Doppler anemometer was used to take measurements of mean and fluctuating velocities of an air flow of 4.6 × 104 Reynolds number in a short duct with a normal wall fixed to one side.
Abstract: A DISA two-colour back-scatter laser Doppler anemometer was used to take measurements of mean and fluctuating velocities of an air flow of 4.6 × 104 Reynolds number in a short duct with a normal wall fixed to one side. Walls of 30 and 20 mm height were investigated and the resulting flow patterns were compared.