bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical Training in Industry for the Graduate in Mechanical Engineering: Part I
Authors: Evans Kenneth R.
Published: October 2007

Part I of this paper reviews the changing outlook during the past forty years on methods of training the mechanical engineers of the future.

Industry and universities have reviewed and amended traditional methods and outlook in significant ways and, in particular, in ‘bridging the gap’ between those responsible for training in industry and those responsible for policy and curricula in the universities.

The effects of two world wars and the incidence of military service are indicated.

Financial considerations concerning fees and maintenance during both university training and apprenticeship are related to opportunity. The influence of the present conditions of more jobs than there are suitable applicants is considered in relation to long-term planning of the training of the mechanical engineer of the future.

The general lines of procedure usually required for those who include a full-time university course as a part of their education and training are considered, and particular attention is given to the increasingly accepted view that pre-university practical training has many advantages which are now recognized by professors and others who teach in the universities and senior technical colleges.

The need for work and play which educate and relax the young man during his post-school five-year formal engineering training period is explained and examples are given; and reference is made to the fact that those least interested in ‘outside’ activities usually benefit most if encouraged and helped to participate in such activities.

It is pointed out that the common good of the individual, the university, the firm, and the nation is most likely to be achieved if a long-term view is always given preference, and that, while time is all important and must not be wasted, time must be given to the preparation for a future career—preparation ample enough to fulfil the demands that opportunities and responsibilities in later life will make.
Corrosion Studies on a Model Rotary Air-preheater
Authors: Thurlow G. G.
Published: October 2007

Tests have been carried out on a model rotary air heater in an attempt to study, on a laboratory scale, corrosion phenomena under conditions similar to those experienced in industrial practice.

The acid dew-point of the combustion gases used varied from 240 to 320 deg. F. and maximum corrosion occurred at surface temperatures within the range 215–240 deg. F. The results confirm previous conclusions as to the influence of the acid dew-point and of the sulphur trioxide content of the gases on corrosion.
The Theory of Plasticity: A Survey of Recent Achievements
Authors: Prager William
Published: October 2007

After a brief historical introduction, recent achievements in the theory of plasticity are surveyed with emphasis on applications in mechanical engineering.

Kinematic models are presented that indicate the complexities of mechanical behaviour in the plastic range. The fundamental theorems of limit analysis are discussed, and their application to two- and three-dimensional problems is illustrated by examples. Shakedown analysis and limit design are defined. Problems involving large plastic deformations are discussed with special reference to metal forming processes. Applications of the theory of plasticity to impact testing and blast damage are reviewed. Recent changes in the theory of structural stability in the plastic range are mentioned. Throughout the lecture, impending developments of the theory of plasticity are indicated.
The Effect of Grinding on the Fatigue Strength of Steels
Authors: Cledwyn-Davies D. N.
Published: October 2007

The paper is a description of an investigation to determine the effects of cylindrical grinding on the fatigue strength of a range of steels: a nickel-chromium-molybdenum alloy steel hardened and tempered to give a nominal ultimate stress of 80 tons per sq. in., the same steel hardened and tempered to give a nominal ultimate stress of 62 tons per sq. in. (Vibrac V30), a 0.6 per cent carbon steel (45 tons per sq. in.) and a 0.1 per cent carbon steel (27 tons per sq. in.). Fatigue tests were carried out in a rotating-beam machine giving uniform bending moment, and the limiting fatigue ratios (endurance limit/nominal ultimate stress) of 0.538, 0.545, 0.420, and 0.550 were determined for turned and longitudinally-polished specimens of the Ni-Cr-Mo steel (80 tons per sq. in.), Vibrac V30, 0.6 per cent carbon and 0.1 per cent carbon steels.

Preliminary tests on Vibrac V30 showed that there was a small reduction (about 4 per cent) in the limiting-fatigue ratio due to grinding. Further experimental work, however, showed that there was no intrinsic reduction in the fatigue strength for this material. Fatigue tests on ground specimens stress-relieved ‘in vacuo’ after grinding indicated that the reduction found in preliminary tests was not due to surface tensile stresses, and it is suggested that the reduction was owing to poor grinding technique, causing burning of part of the surface at the bottom of the 3-inch transition radius. Some specimens of Vibrac V30 were ground by two external laboratories and tested by the author. The fatigue strength of these two batches of specimens was not completely determined owing to the small number of specimens available. In one case the grinding was very uniformly carried out, but indicated a reduction in the fatigue strength of at least 8–10 per cent. The other batch of specimens also showed a reduction in fatigue strength, but no definite conclusions can be drawn owing to the small number of tests carried out and the large scatter of results obtained.

There was no reduction in the fatigue strength due to grinding the 80 tons per sq. in. steel, Vibrac V30, and 0.6 per cent carbon steel, although a small reduction (about 3 1/2 per cent) was obtained with the 0.1 per cent carbon steel. This may possibly have been caused by undetected burning of the surface during grinding, as the same speed, feed, and wheel were used for all four materials.

It is concluded that grinding does not cause a reduction in the fatigue strength of the materials tested, provided the grinding is carried out carefully and under good grinding conditions. The degree of care required to avoid deleterious effects, however, is such that it seems not advisable to advocate the grinding of fatigue specimens generally, unless preliminary fatigue tests have been carried out to determine the true state of the ground surface. Finally, the grinding of parts that are to be subjected to high fluctuating stresses should be avoided, owing to the uncertain state of the ‘production’ ground surface.
The Elastic-Plastic Theory of Containers and Liners for Extrusion Presses
Authors: Horne M. R.
Published: October 2007

Reasons are given for basing the design of containers and liners for extrusion presses on elastic-plastic behaviour. After a review of the available theories on the behaviour of thick tubes and rings beyond the yield point, a solution based on the stress-difference theory of elastic breakdown is adopted. The application of this solution to containers both with and without liners is elaborated, and expressions are derived for the internal pressures sufficient to cause initial yield and full plasticity. Consideration is given to the possible occurrence of alternating yield on the inner surface of either the liner or the container. It is also found that, in certain circumstances, a tapered liner will progressively penetrate the container against the taper at pressures less than those required to produce complete plasticity.

The results of the analysis are presented in the form of charts which cover the whole range of practical conditions.
The Effect of Torsional Overstrain upon the Static Strength of Spring Steel
Authors: Pope J. A. , Andrew J. E.
Published: October 2007

This paper gives the results of an investigation into the effect of low-temperature heat-treatment upon the static properties of a hardened and tempered spring steel which had been previously subjected to torsional overstrain.

The results show that the textural stresses may be relieved by low-temperature heat-treatment without reducing the beneficial body stresses produced by the torsional overstrain. At large overstrains the textural stresses are so great that plastic deformation in the reverse direction takes place on unloading. Such deformations reduce the residual body stresses, and therefore the elastic limit strength, after low-temperature heat-treatment. To prevent the plastic deformation on unloading the specimens should be given the low-temperature heat-treatment before removal of the load.

Tests on six springs showed that the results obtained from torsion specimens are directly applicable to springs.

The improvement in the elastic-limit strength after low-temperature heat-treatment is considerable, about 33 per cent, while the increase in 0.1 per cent proof stress, although marked, is somewhat less and of the order of 8.5 per cent.

After the low-temperature heat-treatment the elastic-limit strength range (that is, the sum of the elastic-limit strengths in the positive and reverse directions) and the 0.1 per cent proof stress range are unaffected by the degree of overstrain. That is, for the steel tested and within the range of strain examined, torsional overstrain does not work-harden the material, any increase in strength in one direction being offset by an equal reduction in strength in the reverse direction.

The change of strengths in the two directions is approximately equal to the corresponding body stresses induced by the overstrain.
Transient Temperature Stresses in Axially Symmetrical Systems with Special Application to a Solid Rotor of a Steam Turbine
Authors: Hoyle R. D.
Published: October 2007

A method of determining thermal stresses in axially symmetrical systems is described. The method is applicable to any axially symmetrical body of irregular shape in which temperature gradients occur in both radial and axial directions, such as ingots that ‘clink’ or crack when heated or cooled too quickly, or gas turbine ‘disks’ of appreciable thickness and to which the thin disk theories do not therefore apply. A convergent numerical solution can be obtained using a combination of two functions, and by ‘relaxing’ two governing equations. The thermal stresses can in this way be determined for any known axially symmetrical temperature distribution, whether its state be transient or steady. The application of the method to the solid rotor of a steam turbine is described.
Hydraulic Transport of Solid Material in Pipes
Authors: Worster R. C. , Denny D. F.
Published: October 2007

The growing interest in the hydraulic conveying of solid material in pipes has brought to light the lack of data for the design of these systems. To meet this need extensive research work has been undertaken both in Britain and overseas and the more important results are summarized.

The flow of mixtures in horizontal pipes is a complex phenomenon not very amenable to theoretical study. It has been found possible to correlate data obtained over a fairly wide range of conditions and the flow in vertical and sloping pipes is also mentioned.

The passage of solids through machines and pipes leads to breakage of the particles and wear of the metal parts. Some test results and conjectures on this are given.

Because high pressures are required for long-distance hydraulic transport or for vertical lifting through pipes, the practical problems of pumping solids are severe. These are discussed with special reference to coal-feeding devices.
An Electrolytic Tank Investigation into Stepped Thrust-Bearings
Authors: Kettleborough C. F.
Published: October 2007

Many years ago the very unsatisfactory bulky and expensive multi-collar thrust-bearing was replaced by the very compact Michell tilting-pad thrust-bearing, which has given very satisfactory service. Of recent years interest has been focused on simpler types of non-tilting thrust-bearings such as parallel-surface bearings and bearings with a machined taper. There is a general desire for a satisfactory cheap, simple, thrust-bearing.

An investigation into stepped thrust-bearings has been carried out with an electrolytic tank, and results indicate that the load capacity is greater than for the tilting-pad bearing. The friction is increased but not in the same proportion as the load capacity.

By a suitable choice of the operating conditions it is possible to design a stepped-pad thrust-bearing which operates over a wide range of loads with a greater film thickness and a lower coefficient of friction than a tilting-pad thrust-bearing.

Owing to the decrease in friction and the simple and cheap construction, there appears no out-standing reason why this new bearing should not supersede the conventional tilting-pad thrust-bearing.
Journal Bearing Performance under Sinusoidally Alternating and Fluctuating Loads
Authors: Shawki G. S. A. , Freeman P.
Published: October 2007

A testing machine has been designed and developed to investigate the performance of a complete journal bearing under a vertical cyclic load of the form P = P0 + P1 sin (ω1 t)+ P n sin (nω1t + φ). This paper presents the results of the experimental study of the bearing performance for the case where Pn = 0 and for values of P1/ P0 between infinity and zero inclusive.

Test results show that the ratio of the rate of load application to that of journal rotation (ω1/ω) is a prime factor in the bearing behaviour. Values of this ratio slightly less than 0.5 give rise to critical changes in the bearing performance, of a character mainly dependent on the ratio of P1 to P0.

The results do not, in general, confirm the theory put forward by Swift; they do, however, indicate closer agreement with some recent theoretical studies.

Further work on the subject is proceeding.
The Influence of Some Design Factors on the Characteristics of Ball-bearings and Roller-bearings at High Speeds
Authors: Fogg A. , Webber J. S.
Published: October 2007

The paper describes investigations into the performance characteristics of ball-bearings and roller-bearings running under conditions similar to those encountered in gas turbines. The majority of the work was carried out on ball-bearings, suitable for shafts of 2 inches diameter, which were run under various combinations of radial load and thrust load. Modifications were made to diametral clearance and track curvature of the bearings and to the material, design, and dimensions of the cages. The effects of these on bearing performance are given and discussed. Investigations on larger (5-inch bore) bearings indicate additional precautions necessary with this size. Work on roller-bearings was confined to the 2-inch size and the variables investigated included diametral clearance of bearing and end clearance of rollers. An interesting comparison is provided by the performance of a cageless roller-bearing.
Micheli Bearing Lubrication
Authors: Kettleborough C. F. , Dudley B. R. , Baildon E. , Kettleborough C. F.
Published: October 2007

An experimental investigation into the operation of tilting-pad thrust bearings has been carried out. The following experimental determinations have been made: film pressure distributions, film geometry, friction characteristics, and temperature distributions for a range of speeds, loads, operating temperatures (that is, viscosity), and pivot positions. An attempt has been made to correlate these results with existing theories.
Surface Examination by Reflection Electron Microscopy
Authors: Halliday J. S.
Published: October 2007

In reflection electron microscopy the surface is viewed very obliquely and the surface protuberances are seen in profile. It is shown that the method may be used for the quantitative study of surface finish. The method is particularly suitable for the examination of surfaces on which the irregularities are small and ground, lapped, finely abraded and polished surfaces can conveniently be studied. Micrographs of various metals show that ground surfaces of comparable roughness may have different textures and these differences appear to be related to the mechanical properties of the metals. The range of surface finish which can be examined is illustrated by micrographs of electropolished aluminium which, over large areas, is flat to about 0.1 deg. and on which the highest asperity is 0.4 micro-inch, and of ground hardened tool steel with asperities up to 70 micro-inches high and sloping at 30 deg. to the general surface. The method is suitable for the examination of surface damage by wear processes and the surface damage on copper after passage of a steel slider is illustrated. Finally, the advantages of reflection electron microscopy over other methods of surface examination are discussed.
The Structural Efficiency of Tube-plates for Heat Exchangers
Authors: Duncan J. P.
Published: October 2007

Experimental investigations are described in which the stress and deflexion distributions in models of tube-plates for high-pressure feed-water heaters were determined. The plates were drilled on a triangular pitch and the loading conditions of heaters employing hair-pin tubes were simulated by equivalent concentrated loads and by means of the ‘Flexible-bag’ technique. Direct measurement of the deflexion and the linear strain on the surface of the plate were made under a wide range of conditions.

Comparisons of deflexion and stress in a given test plate before and after drilling to a four-, two-, and one-pass drilling-pattern provided specific experimental values for the structural efficiency of each type of drilled plate. The dependence of this efficiency on the ratios of hole-size/pitch and pitch/thickness was also investigated.

Methods proposed by other authors for estimating structural efficiency are reviewed in the light of experimental findings and an analytical method of treating one-pass tube-plates, based on Horvay's thick-plate theory, is proposed.
Impact Torsion Experiments
Authors: Calvert N. G.
Published: October 2007

In 1936, the author, working under Professor W. Mason, attempted to obtain a complete torque-time curve for impulsive torsional fracture and thus to obtain quantitative information on both yield and rupture phenomena. The forces were measured by piezo-electric methods and recorded photographically against a uniform time base. The results (hitherto unpublished) showed that while the maximum stresses did not differ appreciably from the static values, the yield point was always greater when the straining rate was high (about 60 radians per sec.).

In recent years the author has carried out a series of experiments at much lower speeds (4 radians per sec. and less) to explore the region between static and impact conditions. The lower speed has brought the upper yield well within the scope of the crystal gauge. Results from a range of mild steels show that both upper and lower yield points increase progressively with the rate of straining, and logarithmic plotting suggests that, for the steels tested, a transition from static to impact conditions takes place at a straining rate of about 1/10 radian per sec. or less.
Heat Transfer between Tubes and a Fluid Flowing through Them with Varying Degrees of Turbulence Due to Entrance Conditions
Authors: Davies V. C. , Al-Arabi M.
Published: October 2007

An electrically heated tube was arranged to give the local, as well as the average, heat transfer between the tube and water, for both normal and abnormal turbulent conditions. The range of the Reynolds number was from 5,000 to 17,000.

The inlet-end thermal effect and the effect of abnormal turbulence were investigated, and the results obtained were correlated by dimensionless groups and compared with the data for air recently obtained by the local method.

The hydraulic loss of head due to abnormal turbulence was measured and compared with the increase in heat transfer.
Effects of Screw and Speed-setting Changes on Gauge Speed and Tension in Tandem Mills
Authors: Hessenberg W. C. F. , Jenkins W. N.
Published: October 2007

The rule that governs the steady state of tandem mills is that the volume of metal passing through each stand in a given time is the same. If the screw setting of the rolls or the speed of the motor on any one stand is altered so as to alter the flow rate, then the other stands must be capable of adjusting themselves to this disturbance with fixed screw and speed settings. They are able to do this because the mechanical parts of the mill are sufficiently resilient to permit the separation of the rolls to alter even though the screws are fixed, and because the characteristics of the motor drive are such that the mill speed may vary even though the speed setting is fixed.

In this paper an attempt is made to relate the changes in interstand tension and finishing gauge which result from such a disturbance to the mechanical and electrical characteristics of the mill, and to predict the behaviour of tandem mills under various conditions.
Fluid Flow and Heat Transfer in an Annulus with a Heated Core Tube
Authors: Barrow Henry
Published: October 2007

Fluid friction, velocity distribution and heat transfer at the inner wall of a smooth concentric annulus in turbulent flow are dealt with in this paper. The results and correlations of a number of previous investigators are briefly reviewed. New friction, velocity-distribution and heat-transfer data from experiments with air flowing turbulently in an annulus of radius ratio 2.248 are presented.

The outer-wall friction factors and velocity data have been correlated by the methods used for smooth circular tubes. Based on these correlations, and the analogy between heat transfer and fluid friction, a semi-theoretical equation for the heat-transfer coefficient is proposed. The suggested equation suits the author's experimental results well, and is applicable for all commercial radius ratios. The range of Prandtl number for which the equation is valid has not been determined.
On the Basic Yield Stress Curve for a Metal
Authors: Watts A. B. , Ford Hugh
Published: October 2007

In a previous paper (Watts and Ford 1952)‡, it was shown that the true yield stress in plane strain could be derived by compression between smooth parallel dies. In this paper the use of the method to determine yield stress-strain curves of strip material is investigated. The various factors involved are studied, and it is shown that the results can be correlated with those of simple tension and compression.

The test forms a practical means for accurately determining the yield stress-compressive strain curve for strip materials in the cold rolling process, and the optimum test conditions are established. The anomalous results found in rolling relatively thick material are demonstrated.
Mechanism of Convective Heat Transfer and its Role in Gas Turbines
Authors: Wilson D. G.
Published: October 2007

The fundamental dependence of convective heat transfer on the pattern of fluid flow is first stated, and this is followed by an elementary presentation, illustrated by examples of the behaviour of models, of the governing principles of fluid dynamics, particularly those concerning the boundary layer. The resultant relative levels of heat transfer from various surfaces are then discussed, together with the effect of different types of fluid. With these fundamental considerations established, an analysis is made of the economics of different types and arrangements of heat exchanger. Finally, methods of turbine-blade cooling are considered from estimates of the heat-transfer pattern round the surface of the blade.
Developments in Mechanized Welding in the Aero-Engine Industry
Authors: Sandiford F. G. C.
Published: October 2007

In this paper, the author emphasizes the rapid development and change which have taken place in the preceding ten years in the sheet metal manufacturing side of the aero-engine industry.

He singles out the development of mechanized welding as one of the more interesting features and gives an illustrated review of a wide range of applications of fusion and resistance welding in current use at the Rodney Works of his company, in the Engine Division.
Hydraulic Accumulators in Heavy Industry
Authors: Frith J. G.
Published: October 2007

In the paper are described the principal features of the weight-loaded and gas-loaded types of hydraulic accumulator together with the applications where they are of particular service.

A distinction is drawn between those gas-loaded accumulators where the gas and the pressure liquid are separated, and those where they are directly in contact with each other, and the separated type is further subdivided according to the method of separation.

The appropriate control gears for the various types of accumulator are described and special reference is made to the particular problems associated with the control of the non-separated type of gas-loaded accumulator.

The normal method used in calculating the volumetric ratio between the compressed gas and the usable liquid in gas-loaded accumulators is quoted, together with the effect of special conditions upon the amount of pressure variation. Figures are also given to show the effect of temperature changes upon the working pressure in this type of accumulator, and the normal maximum allowable working pressure in the non-separated type.
Some Experiments on the Deflections and Vibrations of Drilling Machines
Authors: Galloway D. F.
Published: October 2007

The experiments described in this paper are part of a series of researches being carried out to obtain data for improving the design, construction, and utilization of production equipment, having regard to the increasing demand for such development which will be occasioned by the growth of automation. Research techniques and equipment were developed for examining the deflection and vibration characteristics of various drilling machines. Some comparisons were made between radial-drilling machines, vertical-drilling machines, and portal-frame drilling machines, the latter type being included particularly because of the increased possibilities for its employment in unit construction automated lines. An account is given of the general experimental procedure and the special apparatus used. An analysis is made of the deflection characteristics of each type of machine, and examples are given of the magnitudes of the deflections. The principal natural frequencies of vibration of the machines were determined, and the vibration characteristics of the machines in drilling and facing operations were examined. Recommendations are made for the reduction of machine deflections and vibrations, and a basis for some machine design calculations is developed.
Stability of Parallel-Branch and Differential Surge Tanks
Authors: Zienkiewicz O. C.
Published: October 2007

The paper presents a mathematical theory of stability of small oscillations in surge tanks of the type where two water surfaces are present. The name ‘parallel-branch’ surge tank is coined to describe such a system, and it is shown that results for orifice and differential surge tanks can be obtained from it.

On the assumption of ideal governing and small oscillations of flow and water levels, equations giving the limits of stability are deduced for all cases. It is an easy matter from these to test the stability of any particular design by inserting appropriate numerical values.

In general, the results confirm the well-known Thoma formula for the case of a simple surge tank and give results identical with those obtained by Professor Escande for the case of an orifice surge tank. For differential surge tanks, the limits of stability are given in an equation covering the area factors of the riser and the outer chamber as well as the resistance factors of the main conduit and orifices respectively. Graphs showing this relation between the above quantities indicate that:

(1) if the combined area of riser and outer chamber is equal to the Thoma area calculated for a simple surge tank, then the system is stable provided the resistance factor of the orifice is below a certain limiting value; (2) when the above combined area is less than the Thoma area, then, in general, small but finite oscillations of the water level will persist. By suitable choice of orifices the amplitudes of these oscillations can be made negligible; (3) if the resistance factor of the orifices exceeds the previously mentioned limiting value, then, in general, it is not possible for stability to be achieved with riser areas less than a specified value.

Methods of calculating the frequency and amplitude of permanent oscillations are presented in the paper. The general case of a true parallel-branch system is best solved numerically, but the results indicate that in all practical cases the phenomenon of finite amplitude oscillations will exist. Attention is drawn, however, to the necessity of considering the period at which instability is possible as, on occasion, this is too short for the assumption of ideal governing to be applicable.
Power Station Auxiliary Plant
Authors: Kennedy Geoffrey F. , Hutchinson F. J.
Published: October 2007

Some of those aspects of the auxiliary services in large power stations on which decisions have to be taken at the planning stage are discussed. The effects on the planning of auxiliary services of recent changes in generation practice are noted. The aspects discussed include alternative means of providing auxiliary power, the economic justification for providing standby for various auxiliary-plant items, the diagrammatic arrangement of auxiliary services, the economic and practical importance of certain basic design features and performance figures and sundry practical details that require thought at the planning stage.

It is shown that decisions at this stage should be based as closely as available data permit on quantitative assessments. Among these, particular attention should be given to assessments of the reliability of individual plant items, of the cost of any measures such as duplication for increasing reliability, and of the total cost of forced outages. Methods of basing decisions on such assessments are given. On the basis of experience with a large number of power stations recommendations are made for obtaining the greatest possible ease of operation and maintenance.
Heat Transfer in Pipe Flow at High Speeds
Authors: Bialokoz J. E. , Saunders O. A.
Published: October 2007

Measurements have been made of adiabatic friction and of heat transfer for air flowing in pipes at speeds up to 1·6 times that of sound for conditions closely approaching established pipe flow in the range of Reynolds numbers Re = 1·24 to 4·35 × 105, free stream air temperatures Tb = 190 to 286 deg. K., and wall to free stream temperature ratios Tw/Tb = 1·08 to 1·73.

The heat transfer results agreed within ±5 per cent with the formula

and frictional data were some 4 per cent above

The above formulae were obtained by a method, first suggested by von Kármán (1935), of allowing for compressibility effects by replacing, in formulae for incompressible fluids, the fluid properties computed at bulk temperature by those at wall temperature, and then transforming to terms of these properties at bulk temperature, using the laws of variation of physical properties with temperature as obtained from N.B.S.-N.A.C.A. Tables (1949-50).

Separate tests were made of the heat transfer in the presence of a plane shock-wave in the heated length of the test pipe, and the values of Stanton number were found to be up to 30 per cent higher than for shockless flow. A subsonic test with a similar adverse pressure gradient over the heated length also showed considerably increased heat transfer.

The recovery factors calculated from the adiabatic runs were close to √ Pr, that is, 0·84.
An Experimental Investigation into Stepped Thrust-Bearings
Authors: Johnston R. C. R. , Kettleborough C. F.
Published: October 2007

An experimental investigation into the operation of stepped thrust-bearings has been carried out using an experimental machine and measuring equipment specially designed for the purpose, but adaptable to other types of thrust bearing. The running oil-thickness and friction characteristics have been determined for a range of speeds, loads, and inlet temperature for several different angular positions of the radial step and for two curved steps. Results are given in the usual manner using ZN/P and also in non-dimensional form and are compared with theoretical predictions based on constant viscosity.

The experimental results are compared with the corresponding results obtained on tests of a Michell bearing of identical size and they establish the stepped bearing as being superior to the Michell bearing so far as load capacity and friction are concerned.
Fatigue under Triaxial Stress: Development of a Testing Machine and Preliminary Results
Authors: Morrison J. L. M. , Crossland B. , Parry J. S. C.
Published: October 2007

In this paper the reasons for attempting to investigate the effect of repeated triaxial stresses are discussed briefly. In particular the case of the thick cylinder subjected to repeated internal pressure, which is of some practical importance, is considered.

The design and development of a machine capable of repeatedly applying to cylinders internal pressures of the order 20 tons per sq. in. (3,000 atm.) are described in some detail. Results are presented for such tests on one particular material and these are regarded as presenting an interim statement, but they are compared with detailed information about the properties of this material under a single and repeated application of uniaxial and biaxial stress. In all cases some attention has been paid to the effect of anisotropy.

The thick cylinder tests give results much lower than might be expected from a knowledge of the properties of the material. A number of tentative explanations are put forward: some of these are at present being investigated.
An Approach to the Techniques of Graduate Training
Authors: Marples D. L. , Radford J. F. A. , Reddaway J. L.
Published: October 2007

The initial practical training of the graduate apprentice has been largely a matter of workshop experience and training in craft skills. Such activities do not continue the training of the graduate in the way to which he is accustomed and by which he could best absorb the new knowledge required in industry. The paper describes experiments in methods of instruction for the topics which could be included in the initial three months' graduate training period in any works of which a machine shop is a dominant feature. The methods used followed the typical university teaching pattern of lectures, exercises, and preparation of reports. The topics included the study of the machine shop technology and the study of the machine shop as an operating unit together with the office work, or pre-production activities, concerned with its operation. The experimental methods have been tried out in a factory with a group of twelve undergraduates during a total period of twelve weeks.

It is concluded that training which gives the graduate an opportunity to exercise the special learning abilities he has developed at the university is not only possible but the quickest way to give him the basic knowledge of the technology and organization of production necessary for any mechanical engineering career.
Crankcase Explosions: An Investigation into Some Factors Governing the Selection of Protective Devices
Authors: Freeston H. G. , Roberts J. D. , Thomas A.
Published: October 2007

Remedies which have been suggested for crankcase explosions include the use of warning devices to detect over-heating in the crankcase, and the provision of relief vents to limit the explosion pressure to a safe value.

Data were obtained experimentally at the Thornton Research Centre for the conditions necessary for the ignition of mists of lubricating oil in air in order that the margin of safety offered by a detector of overheating might be more fully assessed.

The venting of explosions was also studied both on a rig scale and in the crankcase of a Diesel engine of 1,100 h.p. The results indicated that it would not be practical to provide sufficient venting area on an engine of this size, to limit the maximum explosion pressures to a safe value for the more violent explosions which might occur. For venting to provide complete protection, it would seem necessary to take measures to prevent the flame from spreading throughout the whole crankcase.
Crankcase Explosions: Development of New Protective Devices
Authors: Mansfield W. P.
Published: October 2007

Tests of a crankcase explosion relief-valve 6 inches in diameter, provided with various wire-gauze flame traps showed such flame traps to be ineffective when ***severe explosions were made with mixtures of town gas and air. It was discovered that coating the wire gauze with lubricating oil greatly increased the effectiveness. of the flame trap. An internal, oil-wetted flame trap of less ***than half the original size was fully effective with the most severe explosion that could be produced.

An oil-wetted flame trap, covering an aperture in a dividing partition of a cylindrical explosion vessel fully charged with gas-air mixture, was found to limit combustion to the chamber in which the mixture was ignited, and to limit the maximum pressure to one quarter of the value reached without the partition flame trap.

Internal oil-wetted relief-valve flame traps and partition flame traps were then successfully tested on a ***three-cylinder engine of 9 inches bore. From the results obtained, the requirements of a large engine are estimated and it is concluded that the use of the two new devices would provide adequate protection at acceptable cost.
The Performance of an Axial-Flow Pump
Authors: Spencer E. A.
Published: October 2007

Tests were made on an 11-inch diameter axial-flow propeller pump with impeller and guide blades designed for free vortex conditions, using as a basis the modified aerofoil theory. The best overall efficiency obtained was 82 per cent. Apart from head-flow and efficiency characteristics, measurements were made of velocities and yaw angles within the pump at the design flow of 6 cusecs. and these showed where departures from the theoretical assumptions occurred.

Head-flow characteristics were obtained for various impeller blade-tip clearances from 0·015 to 0·060 inch (0·6 to 2·4 per cent blade height) and it was deduced that secondary flows were not confined to the tip region alone, but extended across the whole annulus.

The pump was on an open circuit, so that cavitation tests were limited. Nevertheless, methods of increasing the resistance to cavitation susceptibility are considered.

It was concluded that despite the fact that some of the assumptions made in the theory are invalid, this method of design may be used with confidence for pumps in the specific speed range of approximately 8,000.
Forces on a Brake Block and Brake Chatter
Authors: Broadbent H. R.
Published: October 2007

The paper commences with an examination of the forces on a brake block applied to the wheel of a railway vehicle. Servo action and certain implications concerning test figures of block friction and adhesion are discussed. The dynamic conditions of equilibrium are shown, if upset, to cause oscillation or ‘chatter’ of the brake gear; an explanation is given of this phenomenon and, with it, a cure.
Economic Basis and Character of Steam-Turbine Design
Authors: Elce Norman
Published: October 2007

The economic basis of the design of steam power plant as compared with the situation recorded in Baumann (1949)† is reviewed, and the character of turbine design is illustrated by reference to two selected groups of problems, one related to the behaviour of rotors in service, the other to the design of diaphragms and some associated questions of efficiency.
An Experimental Study of Fretting
Authors: Feng I-Ming , Rightmire B. G.
Published: October 2007

A new technique for visual examination of the progressive development of fretting is evolved and found to be especially useful in following the progress of fretting from the initial stage to the later stages. The qualitative investigation, co-ordinated with a quantitative study in three different atmospheres, dry air, carbon dioxide, and helium, yielded results supporting the mechanism of fretting suggested by the authors in a previous publication. Visual observation also leads to the conclusion that chemical reaction, for example, oxidation, of metal with the environment takes place when the metal is being removed, or after it has been removed, from the surface.
The Development of a Mechanical-Draught Water-Cooling Tower
Authors: Smith L. Gilling , Williamson G. J.
Published: October 2007

The paper describes the development of a mechanical-draught water-cooling tower containing a number of novel features. The packing is composed of serrated timber laths down which the water flow is film-wise to avoid splash formation. An earlier paper (Carey and Williamson 1950)§ gave the results of small-scale tests which indicated the theoretical advantage of grid film-flow packings in that the ratio of heat transfer to pressure drop is greater in this type of packing than in any other. A non-splash multi-trough water distributor is used to avoid the carry-over of splash droplets and hence to prevent a local deposition nuisance. Special attention has been given to the even distribution of water and air. Induced draught effects this better than forced draught and, since the fans exhaust heated air, there is no danger of ice formation upon them in frosty weather. The fans are large slow-running and aerofoil bladed, designed to give the highest possible static efficiency and to reduce the loss of velocity head at exit. The main design variables of air velocity and air/water ratio are determined from a balance of capital charges, packing, and power cost.

Several examples, showing the methods of construction, are given of these towers. The main structure and shell is usually in reinforced concrete because of its rigidity in supporting the fans and drives and its permanence and fire resistance, but timber is quite satisfactory and cheaper. The pond is in concrete in all large towers. Timber is the usual material for the packing and distribution troughs, and the water flow is controlled by orifice tubes now made in glass. Methods have been developed for supporting the laths and troughs so that they remain level and in proper relation to each other after wetting. The packing is usually built on reinforced concrete beams across the main structure.

Running experience obtained during six years is given together with the results of a comprehensive programme of tests. The good small-scale packing performance has been confirmed on the large scale. The tests have shown deficiencies in gear-driven fan installations, established the harmful effect on cooling efficiency of recirculation of the warm exit air and, in general, put on record performance details for critical assessment of this new development.
Salvaging of Ships with Special Reference to the Empress of Canada
Authors: Colbeck W. R.
Published: October 2007

The lecturer discusses considerations affecting harbour salvage, the growth and the existing plant of the port salvage organization at Liverpool and the reasons why such an organization is required. Emergency operations are briefly discussed. The removal of wrecks by lifting or dispersal is considered and the operation of lifting vessels with the aid of wires and external buoyancy provided by camels is described in detail, two recent operations being given as examples. In January 1953 the Empress of Canada, a passenger liner of 20,021 gross tons, sank on her side in Gladstone Dock, Liverpool, as a result of a fire. The events leading to the loss and the operations of uprighting and refloating are described with details of methods and materials used and the difficulties encountered.
Education of Engineers in European Countries
Authors: Davies S. J.
Published: October 2007

Systems of education in certain European countries are surveyed in detail in relation to the special circumstances of each country. Reference is also made to the numbers of those trained in allied branches of science. In addition to this provision, it was found that in these countries technical schools and colleges exist which cater for ‘technicians’ and in which considerable numbers of students attend full-time courses and reach standards roughly comparable to Higher National Certificate (H.N.C.)

Among other matters, the survey reveals that, in spite of the fact that Great Britain is the most industrialized country of those considered, in the relative numbers of engineers educated to degree level it shares with Austria and Belgium the lowest positions. The lack of qualified engineers to fill posts abroad is mentioned, a lack which, in the long-term, must lead to loss of trade. On the other hand, Britain's position with respect to higher degrees is relatively better.

Notwithstanding Britain's need for engineers, there are vacancies in some of her universities. The ‘bottle-neck’ in the supply is in the restricted numbers studying science in the sixth forms of schools; to make use of the increasing provision now being made for high-level engineering studies, these are the numbers most in need of attention.
An Investigation into the Mechanism of Oil Loss past Pistons
Authors: Dykes P. de K.
Published: October 2007

The mechanism of oil loss past pistons was investigated in a laboratory test rig in which a piston was both reciprocated and subjected to gas pressures. The investigation brought to light the following facts and it is believed that this is the first time that they have been demonstrated:

(1) Oil control is a two-way and not a one-way problem. The only reason why the rate of oil consumption is reasonably small in most engines is that, although a large amount of oil flows towards the combustion chamber past the rings during part of the engine cycle, nearly all of it returns to the sump during the remainder of the cycle. (2) The various routes permit surprisingly large rates of oil flow in both directions past rings. This applies even with good rings. (3) If oil is added to the combustion chamber, a good ring arrangement will pass it to the sump at a rate up to many thousand times larger than the normal rate of oil consumption with the same arrangement. (4) The piston lands, and the top land in particular, play an important role in deciding the rate of oil consumption. If some oil has passed the rings it may be thrown into the combustion chamber and be lost; alternatively, an effective top land may retain this oil until by one method or another it is returned to the sump.
A Study of Piston-Ring Lubrication
Authors: Eilon Samuel , Saunders O. A.
Published: October 2007

This paper describes an experimental study of the lubrication between a one-ring piston assembly and a cylinder. Instantaneous friction forces of the piston assembly were recorded by means of a special apparatus with a stationary piston and a reciprocating liner. Tests were carried out to determine the effects of viscosity, speed, and pressure on the friction, from which the oil film thickness under the ring was calculated. A suggested lubrication theory of piston rings is given, based on a balance of forces acting radially on the ring, leading to a theoretical formula for calculating the ring film thickness, which is in reasonably good agreement with the experimental results. Suggestions are made for the design of rings to give improved friction and heat transfer and to reduce cylinder wear, especially in the initial running-in period.