bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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 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.
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.
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.