Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1962"
TL;DR: The degree of metallic contact, expressed as the ratio of the surface roughness to the oil film thickness, is found to play an important part in determining the pitting behaviour of lubricated rolling surfaces as discussed by the authors.
Abstract: The degree of metallic contact, expressed as the ratio of the surface roughness to the oil film thickness, is found to play an important part in determining the pitting behaviour of lubricated rolling surfaces. In particular under a repeated contact stress of about twice the nominal pitting endurance limit, experiments have shown that the life of the surface before pitting occurs is governed by this ratio. At the same high stress there is some evidence that, in the complete absence of metallic contact, pitting does not occur at all.
134 citations
TL;DR: In this paper, the full effects of speed over a wide range and of lubricant compressibility are presented for the elastic rollers in terms of the number of rollers used.
Abstract: Recent work by the authors and others on the lubrication of elastic rollers is briefly reviewed. The full effects of speed over a wide range and of lubricant compressibility are presented for the f...
123 citations
TL;DR: The local heat transfer characteristics for air flowing turbulently in the entrance region of a circular duct have been determined experimentally over a flow Reynolds number range of 10 000 to 110 000.
Abstract: The local heat transfer characteristics for air flowing turbulently in the entrance region of a circular duct have been determined experimentally over a flow Reynolds number range of 10 000 to 110 000. A wall-boundary heating condition of uniform heat flux was imposed. The entrance configurations investigated included a long calming section, bellmouth, orifice plate arrangements and various entries of practical significance—elbow, T-piece, etc. A correlation of heat transfer under fully developed conditions is included together with a discussion of the effects of fluid property variation in an axial direction. Entrance-region heat transfer data are presented in the form of local heat transfer film coefficients and as the dimensionless ratio , this quantity being defined in such a manner as to eliminate the effects of fluid property variation in an axial direction. Data for average heat transfer over tubes of lengths from 1/4 diameter to 320 diameters are presented in the form of the ratio . In the case of...
83 citations
TL;DR: In this article, the authors proposed a method of comparing the heat transfer coefficients in two channels in which the cross-sectional shape is different, there are different proportions of rough and smooth surfaces, and the proportions of heated and unheated surfaces are different.
Abstract: The author proposes a method of comparing the heat transfer coefficients in two channels in which(1) the cross-sectional shape is different;(2) there are different proportions of rough and smooth surfaces;(3) there are different proportions of heated and unheated surfaces.In particular the method applies to experimental results for the system in which a roughened, heated cylinder is placed centrally in a smooth unheated pipe. The effective diameter concept is used to allow for changes in shape, and the heat-transfer boundary conditions are modified to make them similar to the fluid-flow boundary conditions before the comparison is made.
55 citations
TL;DR: In this paper, an analytical solution giving conditions at instability of a thin-walled tube subjected to internal pressure and independent axial load is presented, and an attempt is made to explain the physical reasons for the occurrence of an instability.
Abstract: An analytical solution giving conditions at instability of a thin-walled tube subjected to internal pressure and independent axial load is presented. An attempt is made to explain the physical reasons for the occurrence of an instability.The analysis shows that a given material has greatest ductility when the ratio of the hoop stress to axial stress has the value one half. The material has least ductility when it is in the form of a closed-ended tube subjected to internal pressure.The terms ‘tensile strength’ and ‘percentage elongation’ are discussed within the framework of the present investigation.
54 citations
TL;DR: In this paper, the effect of higher mean stresses on the rate of crack growth was investigated, and it was concluded that, for values of mean stresses greater than 2 ton/in2, the growth rate of growth could be represented by: where l is the crack length, σalt the nominal semi-range of alternating stress, and σmean the nominal tensile mean stress.
Abstract: Fatigue tests have been carried out on sheet specimens, 10 in wide by about 0·1 in thick, containing a small central slit, and measurements made as the test proceeded of the lengths of fatigue cracks initiated by the slit Seven common engineering materials were tested at various tensile mean and alternating stresses Similar tests have been reported previously (Frost and Dugdale (1)† and Frost (2)) in which the tensile mean stresses were relatively low; in the present paper the effect of higher mean stresses on the rate of crack growth was investigated It was concluded that, for values of mean stresses greater than 2 ton/in2, the rate of growth could be represented by:where l is the crack length, σalt the nominal semi-range of alternating stress, σmean the nominal tensile mean stress and σmean ≥ σalt (ie stress cycle wholly tensile), N the number of cycles, and P and Q are material constantsFor mild steel and copper the rate of crack growth was independent of tensile mean stress,
40 citations
TL;DR: In this article, a basis for comparing different engines is suggested which takes into account the total swept volume of the machine and the maximum cycle pressure, referred to as the power parameter.
Abstract: Stirling engines can be classified into three different configurations which operate, in the ideal case, on a regenerative cycle having an efficiency equal to the Carnot cycle. Expressions are derived for the work done per cycle for each configuration. A basis for comparing different engines is suggested which takes into account the total swept volume of the machine and the maximum cycle pressure. This is a dimensionless quantity referred to as the power parameter. Several thousand different values of this quantity have been calculated for a range of all the variables with the aid of an electronic computer. This has enabled the optimum proportions for engines of each configuration to be determined. The results are presented in the form of a chart. It is found that according to the method of comparison used one configuration is superior to the others.
38 citations
TL;DR: In this paper, a differential equation for the torsional vibration of a uniform rod of non-circular section is derived, which takes into account the longitudinal stress and inertia which arise from the warping of the rod.
Abstract: A differential equation for the torsional vibration of a uniform rod of non-circular section is derived which takes into account the longitudinal stress and inertia which arise from the warping of ...
38 citations
TL;DR: In this paper, a method of determining the vibrations of cantilever beams of non-uniform pretwist and cross-section is described, and the known condition for orthogonality of normal modes for a beam in simple modes is described.
Abstract: The author describes a method of determining the vibrations of cantilever beams of non-uniform pretwist and cross-section. The known condition for orthogonality of normal modes for a beam in simple...
35 citations
TL;DR: In this article, it was shown that in some speed ranges regime (1) holds and in others (2) it does not hold and there are also speed ranges in which either regime is possible.
Abstract: If a vertical undamped shaft has one clearance bearing, the other bearings having zero clearance and all being in line, then there are two possible regimes of synchronous whirl which can hold, namely:that in which the shaft does not touch the clearance bearing,that in which the shaft touches the clearance bearing continuously, the point of contact running round the bearing at the shaft speed.It is shown that in some speed ranges regime (1) holds and in others (2). There are also speed ranges in which either regime is possible.When damping is allowed for, these results are not greatly modified. The whirling behaviour of the shaft differs however from that of a shaft with zero bearing clearance in several ways. In particular the critical speeds are lower, and also there is a more abrupt drop in the whirl amplitude curve above the critical speeds.The behaviour of the shaft when it is accelerated through a critical can differ from that when it is decelerated.
34 citations
TL;DR: In this paper, a dynamic mechanism is proposed to explain the formation of scale at the triple interface of steam bubble, heating surface and solution, and the theory advanced by Partridge that these deposits are due to evaporation is confirmed.
Abstract: This paper describes part of a programme of fundamental study of scale formation. The work described here is concerned with the initiation of scale formation at a heating surface where boiling is taking place. The crystalline ring formations first observed by Partridge (I) with calcium sulphate solution were seen using a range of other solutions under various flow conditions. A variety of other formations based on Partridge's rings were also observed. The theory advanced by Partridge that these deposits are due to evaporation at the triple interface of steam bubble, heating surface and solution was in general confirmed. A dynamic mechanism is proposed to explain these formations.
TL;DR: In this article, the main object of the work reported here was to find a rational design method for granule-fed single-screw extruders used for plastics processing, and the first half of the paper contains a brief revie...
Abstract: The main object of the work reported here was to find a rational design method for granule-fed single-screw extruders used for plastics processing.The first half of the paper contains a brief revie...
TL;DR: In this article, uniform tension was applied to 1in. thick 6in. wide plates, which contained edge cracks normal to the direction of loading, after stress freezing, slices normal to a plane of the crack were cut and analyzed.
Abstract: Uniform tension was applied to 1-in. thick 6-in. wide plates which contained edge cracks normal to the direction of loading. After stress freezing, slices normal to the plane of the crack were cut and analysed. The results were compared with theoretical solutions by Westergaard (1)‡ and Williams (2). In general, both solutions were found satisfactory, but the hydrostatic tension predicted for the line of the crack was not found. The slight inequality of the stresses changed the directions of the principal stresses radically near the line of the crack.
TL;DR: A Stirling engine is a mechanism used to convert heat into power or vice versa and operates on a closed regenerative thermodynamic cycle with compression and expansion of the working fluid at diffe...
Abstract: A Stirling engine is a mechanism used to convert heat into power or vice versa and operates on a closed regenerative thermodynamic cycle with compression and expansion of the working fluid at diffe...
TL;DR: In this paper, a shear plane theory of hot rolling is proposed, based on the well-known observation of localized deformation during the rolling process, which gives a more satisfactory indication of the influence of the R/h ratio on load and torque than does the Sims analysis.
Abstract: A shear plane theory of hot rolling is proposed, based on the well-known observation of localized deformation during the rolling process.Equations of simple form in terms of yield stress and geometric functions enable roll load and torque to be readily evaluated with or without tensions.Comparison with the experimental results of Wallquist suggests that the theory gives a more satisfactory indication of the influence of the R/h ratio on load and torque than does the Sims analysis.Equations are presented in four forms:the general case with tensions;the more common case without tensions;simplified equations which are valid for most practical conditions; andgraphical functions for use with the Cook and McCrum yield stress data.
TL;DR: In this paper, the results of an experimental investigation into the possible modes of gas-excited vibration of a single row of tubes in a heat exchanger at typical practical spacings are presented.
Abstract: The results are presented of an experimental investigation into the possible modes of gas-excited vibration of a single row of tubes in a heat exchanger at typical practical spacings. The vibrations discussed are vortex excited and, for damping which permits large amplitudes, occur at values of the Strouhal number 0·26 < ND/V < 0·89. The critical range of ND/V is affected by both Reynolds number and spacing. Four distinct modes of vibration are found, all consisting of motion principally transverse to the flow direction.Preliminary studies of pairs of tubes, at varying spacing, indicate similarly large ranges of the parameter ND/V in which vibration will occur at typical practical spacings.The types of vibration described are distinct from, and should not be confused with, either the acoustically coupled type or the equally important modes, in which the motion is principally streamwise, occurring at much lower values of ND/V.
TL;DR: In this paper, a non-dimensional diagram is used to compare the load-rate of deflection characteristics of the structure for different values of n. The authors set out to consider the effects of changes in the index n.
Abstract: A structure of given geometry is made of a material whose stress-strain rate law is of the formwhere Bn and n are properties of the material. The authors set out to consider the effects on the load-rate of deflection characteristics of the structure of changes in the index n. A non-dimensional diagram is used to compare the load-rate of deflection characteristics of the structure for different values of n. A recent theorem is quoted which indicates that in this diagram the (closed) curves corresponding to different values of n nest inside each other as n increases. As the curves for n = 1 (which corresponds to linear elasticity) and n=∞ (which corresponds to perfect plasticity) may usually be established without much difficulty, they may therefore be used conveniently to locate the region in which the curves lie for any other intermediate value of n. Inspection of the curves for different values of n for several structures indicates that the theorem may become a useful tool in the study of the steady cree...
TL;DR: In this paper, the authors measured the drag on metallic spheres falling through various fluidized beds of glass beads and certain granular powders and found that the drag is a function of three dimensionless groups.
Abstract: Certain substances float on the surfaces of gaseous fluidized beds and others sink. This phenomenon has industrial applications in separation by creaming and sedimentation. To help the development of these applications the author measured the drag on metallic spheres falling through various fluidized beds of glass beads and certain granular powders. The meta***llic spheres were attached to a nylon thread which passed over a pulley system. Different balance weights were attached to the other end of the thread to produce different uniform velocities of fall. The friction of the system and the buoyancy of the immersed metallic spheres were predetermined. The drag on the sphere was then the only unknown. It was found that the drag is a function of three dimensionless groups, namely Reynolds number, Froude number and the ratio of the diameter of the metallic spheres to the mean diameter of the glass beads or powders forming the fluidized beds.For spheres above a certain diameter deviation occurred in the measu...
TL;DR: In this article, the concept of receptances is used to investigate the stability of machine tools under orthogonal cutting conditions when regeneration does not take place, i.e. on the first pass, or on the second pass.
Abstract: This paper utilizes the concept of receptances to investigate the stability of machine tools under orthogonal cutting conditions when regeneration does not take place, i.e. on the first pass, or wh...
TL;DR: In this article, a pair of shafts, connected by gears, forms a mechanical system having a number of modes of vibration, each mode involves a combination of torsion and flexure of the shafts and of bending of the me...
Abstract: A pair of shafts, connected by gears, forms a mechanical system having a number of modes of vibration. Each mode involves a combination of torsion and flexure of the shafts and of bending of the me...
TL;DR: In this article, a theory for the development of the axial and peripheral velocity profiles in the early stages of an axial-flow compressor is presented, which assumes the existence of a stall-zone in the corner formed by the convex surface of each blade and the annulus wall.
Abstract: A theory for the development of the axial and peripheral velocity profiles in the early stages of an axial-flow compressor is presented. The theory assumes the existence of a stall-zone in the corner formed by the convex surface of each blade and the annulus wall. The extent along each blade of this stall-zone is assumed to be related to the theoretical annulus boundary layer thickness; equations are derived for predicting its growth through the blade roots and tips. The conditions at the blade ends are determined from the theory of a two-dimensional stalled cascade and the outlet angle variation is determined by momentum mixing. Actuator disc theory is then used to find the resulting flow. The predictions of this method are compared both with experimental results obtained from a three-stage compressor and with the predictions of secondary flow theory in which both loss and blade row entry velocity profile are taken from experiment. Somewhat better agreement between the stall-zone theory and experiment is...
TL;DR: In this paper, the effect of normally distributed variations in the coefficient of friction between the screw threads of the nut and bolt was considered, and the effects of these variations on the pretension of the bolt were investigated.
Abstract: When load is applied to a bolted connection in the direction of the bolt axes, the residual clamping force on the joint is dependent upon the pretension of the bolt. Where bending action is also present, the fluctuating stress in the bolts may also be dependent upon the pretension. In most cases where an accurate pretension is required, the bolts are tightened by means of a torque spanner, and the pretension is then dependent upon the coefficient of friction between the screw threads of the nut and bolt. The effect of normally distributed variations in the coefficient of friction on the pretension is considered.
TL;DR: In this paper, the thermal stresses in axially symmetrical elastic bodies with irregular boundaries can only be obtained using finite difference techniques, and two other stress functions are suggested which have several advantages, one of which is that these functions converge satisfactorily when completely relaxed alternately.
Abstract: The thermal stresses in axially symmetrical elastic bodies with irregular boundaries can only be obtained using finite difference techniques. Hoyle demonstrated that a solution can be computed by using the two-diagram technique but the two stress functions used have proved to be difficult to handle. These difficulties are analysed and two other stress functions are suggested which have several advantages, one of which is that these functions converge satisfactorily when completely relaxed alternately. The boundary conditions which these functions must satisfy have been rationalized and a new approach to boundaries developed which removes the worst of the difficulties formerly associated with curved boundaries.
TL;DR: In this article, the large deflection analysis of a rigid-plastic encastre beam carrying a point load obtained by Haythornthwaite is extended to cover beams carrying uniformly spaced equal point loads.
Abstract: The large deflection analysis of a rigid-plastic encastre beam carrying a point load obtained by Haythornthwaite is extended to cover beams carrying uniformly spaced equal point loads. It is shown how the principles revealed in the extended analysis may be used to draw the flow line for an idealized encastre three beam by three beam grid loaded at all node points. Experimental results are presented to show what significance may be attached to the analysis.
TL;DR: In this article, an analysis of the effect of spline friction on the torque capacity and interface temperatures reached in a multi-disc clutch was made and a rapid method of determining the maximum temperature during an engagement was also given.
Abstract: An analysis is made of the effect of spline friction on the torque capacity and interface temperatures reached in a multi-disc clutch. A rapid method of determining the maximum temperature during an engagement is also given.
TL;DR: In this paper, a method for predicting the flexural behaviour of simply supported plates supported in elastic mountings is presented, which is related to the existence of points of inflection in a simply supported plate.
Abstract: A method is presented for predicting the flexural behaviour of circular plates supported in elastic mountings. When loaded, such plates acquire a boundary condition intermediate between a simply supported and encastre condition. If, is as often the case, a relation Mr / dw/dr= A exists between the moment exerted on the mounting by the plate, Mr, and the slope produced in the mounting, dw/dr, the plate deflects like a simply supported plate having an ‘effective Poisson's ratio’ equal to Aa/D+ρ where ρ is the natural Poisson's ratio. This has been demonstrated both theoretically and experimentally and related to the existence of points of inflection in simply supported plates.
TL;DR: In this article, the failure of a turbine-driven compressor set as a result of torsional excitation due to gearing error is reported, but the type of system and conditions under which the failure occurred are not described.
Abstract: Some details are recorded of the failure of a turbine-driven compressor set as a result of torsional excitation due to gearing error. While serious vibrations of this sort are apparently rare, the type of system and conditions under which the failure occurred are not.
TL;DR: In this paper, the reliability of the calculation methods used to predict the flexibility, forces, and stresses in a typical pipework system was evaluated on a full-scale pipeline of 6 1/2in. nominal bore pipe for 450 lb/in2 working pressure and 750°F steam temperature with two right-angle bends.
Abstract: This paper describes tests made to check the reliability of the calculation methods used to predict the flexibility, forces, and stresses in a typical pipework system.A test rig set up in the laboratory has been used to carry out tests on a full-scale pipeline of 6 1/2-in. nominal bore pipe for 450 lb/in2 working pressure and 750°F steam temperature with two right-angle bends. Tests at room temperature have been made with controlled anchor movements corresponding to those which would occur on cold pull-up, thermal expansion, or pure bending, all without internal pressure. In addition tests have been made with internal pressure only, and with internal pressure combined with controlled anchor movements. Further tests were carried out by heating the pipeline and measuring the increase of the forces at the restrained anchors, but no strain measurements were made at high temperatures.The results show that the calculation methods are sufficiently reliable for predicting the forces and stresses in such a pipelin...
TL;DR: In this article, a new correlation for fresh experimental data is suggested, which introduces the shear force at the wall of the tube into an existing dimensionless expression, which deviates from the mean lay of results by as much as ± 20 percent.
Abstract: Existing correlations for the heat transfer coefficient to water in forced convection appear to deviate from the mean lay of results by as much as ±20 per cent. A new correlation for fresh experimental data is therefore suggested, which introduces the shear force at the wall of the tube into an existing dimensionless expression.