Proceedings of the Institution of Mechanical Engineers

SYNOPSIS This paper describes a simple system of controlling exhaust emissions from gasoline engined vehicles, using a coolant-heated fuel vaporiser in the inlet system. The object of complete vaporisation of the fuel is to create a homogeneous inlet charge, giving improved cylinder-to-cylinder distribution and permitting operation with very lean mixtures. This leads to low exhaust emissions of Carbon Monoxide, Hydrocarbons and Nitric Oxides. The effects of vaporisation on the lean limit of operation, exhaust emissions, power output, fuel consumption and optimum spark ignition timing have been investigated, and are discussed in the paper. Results of tests on a 1.6 litre car are also presented. It was found that exhaust emissions were effectively controlled, while vehicle driveability remained acceptable. Engine power was reduced by 25-30%, although fuel consumption was not increased.

SYNOPSIS. Mixture quality and turbulence in the isolated cylinder of a multi-cylinder spark ignition engine were changed by the method of mixture preparation in the induction tract and by the increase of mixture flow velocity through the valve aperture which was varied by the change of the full lift of the inlet valve. The fuel consumption and the mass rates of the emissions of carbon monoxide, nitric oxide and hydrocarbons of the engine when controlled with a conventional throttle are compared with those of the valve throttled engine. The employment of exhaust gas recirculation is shown to have a decisive effect on the comparison and to be essential for low emissions from a valve throttled engine.

SYNOPSIS The paper describes experiments which demonstrate the feasibility of using a fluidic cone-jet sensor supplied with air and producing a pressure output to measure mean clearance, eccentricity and rotor speed inside a steam turbine. Mean clearance can be indicated on a bourdon tube pressure gauge whilst eccentricity can be measured using a piezo-electric pressure transducer and phase sensitive detection. Variation in mean clearance from 2mm to 4mm and eccentricity up to 0.37 mm have been shown to provide linear outputs within ± 5% of full scale. There is no significant fall-off in eccentricity signal up to a turbine rotor speed of 6000 rev/min.

Rope has always been an important item in the marine environment. The transition from one type of construction to another, notoriously slow: for example, rope of both wire and fibre supplied to the S.S. ‘Great Britain’, launched in 1843 was of a similar type and quality to that which would be equally familiar to our mariners a century later.

Many having experience in this latter period might recognize some similarity with the rope in use today but there have been substantial changes, and these changes have occurred not specifically because of any major breakthrough in rope design and production, although there have been very substantial advances in these sectors but because the detail of today's and tomorrow's applications have themselves changed.

The paper examines a number of the major applications involving rope in the marine environment, and shows how rope characteristics must be recognised and wedded to the duty parameters if optimum performance is to be achieved.

SYNOPSIS The development of a ‘catchpot’ probe to measure coarse water flows (formed by deposition and re-entrainment, or agglomeration, of fog droplets) in the low pressure stages of a steam turbine is described. Theoretical considerations and laboratory calibration showed acceptable performance and accuracy limits.

Results taken in three operating turbines at measuring stations situated downstream of the unshrouded penultimate and last row rotors are presented. These results show a peak in the radial distribution of the coarse water flow coinciding with the steam tip leakage region. The measured yaw angles of the coarse water flow agreed with the respective steam yaw angles except near the outer casing. The results are interpreted to give a simple model for the coarse water flows downstream of an unshrouded rotor and its implications for turbine design are discussed.

SYNOPSIS The paper reports a study of the determination of an optimal replacement policy for transport fleet vehicles in the 7/8 ton load carrying capacity. Comments are made about the limitations of the constant economic life approach to replacement decisions. The concept of an Annual Maintenance Cost Limit approach is suggested and used to set replacement decisions for a fleet of 150 similar vehicles.

SYNOPSIS Failures in a limpet coil vessel arising due to thermally induced stresses are discussed. A method of presenting design information on stresses due to pressure in part circular limpet coils is given for a range of parameters. Analytical and experimental work on a rectangular limpet coil vessel is also described.

A technique is described for selecting the operating: pressure and pipe sizes in fluid power circuits. The method is based upon the formulation and minimization of a cost function which quantifies the capital and running costs of the circuit. (The running costs are broadly defined in order to include the cost penalty due to the weight of the system, as well as the cost of lost power.)

The limitation imposed upon design by the commercial availability of only a limited range of stock sizes of pipe is taken into account to ensure that the design is realizable from stock components.

An example is given which compares the results of a design based upon the cost criterion with a design arising from the use of empirical flow velocities to select pipe sizes.

The paper outlines the processes which gave rise to the rapid transit proposals for Tyneside, and the development of these into the Tyne and Wear Metro. The concept of a fully integrated public transport system, capable of making a significant contribution to local movement and land use is explained, and the feasibility of introducing Metro over a significant part of the existing British Rail network detailed. A technical description of the Metro includes civil engineering, signalling and communications, and electrification. The rolling stock is described in detail. The paper concludes with sections on finance and organisation.

SYNOPSIS A versatile computer-based testing and data acquisition facility developed to improve the speed and accuracy of engine research work is described. The role of computer-aided technology is illustrated through the discussion of two quite separate problems.

Fuel burning rates (heat release diagrams) are the most basic measurement of combustion, yet highly sophisticated equipment and techniques are required to obtain accurate rate diagrams. The problem is illustrated through the derivation of heat release data by analysis of averaged and smoothed cylinder pressure diagrams from naturally aspirated and turbocharged diesel engines. Techniques developed for transducer mounting, choice of sampling interval, data-logging, processing, smoothing, etc. are presented.

During transient conditions (e.g. sudden load chnages) a turbocharged diesel engine moves through operating regimes not normally encountered in steady state operation. Although empirical models have been used to prodict the transient response of these engines, only high-speed data-logging of many engine parameters during a transient will permit the development of more basic models. A fully instrumented turbocharged diesel engine has been run (under computer control) through a series of dynamic tests comprising load and speed demand changes, plus combinations of the two. The use of a computer controlled system allowed transients to be re-enacted with a very high order of accuracy following engine design changes. The high-speed data logging system enabled basic data, such as fuel burning rates, to be obtained for each cycle during the transient.

Energy is needed to convert minerals into the basic materials which are used in the engineering industry and then to form them into end products. It is in the conversion that most of the energy is normally consumed, and increases in the costs of energy influence the relative costs of these materials. The energy needed to form the materials into the various end products is normally small in comparison and, even from an energy conservation point of view, it is more important to employ forming methods which use the minimum amount of material than to choose methods which inherently use less energy. The ability to recycle with low energy consumption the material which is discarded during the forming or shaping process is important and improved recycling could have considerable impact upon the overall energy consumption. Whereas the overall energy consumption is important, it is the cost of the raw materials themselves and the total cost of the process to the finished product (offset by any return on waste products) which determines the relative cost of each of the various engineering materials. The united Kingdom energy situation and its effect on the relative positions of these materials is discussed.

SYNOPSIS. Nuclear power should account for 20% of primary energy production in the Western world by the end of the century, but only if growth of generating capacity can be freed of the constraint of uranium supply. It is shown that, providing fast breeder reactors and their associated fuel reprocessing facilities are developed quickly, a substantial increase in nuclear capacity could be provided by fast reactors. The relative importance of various fuel cycle parameters is spelt out and brief accounts are given of the alternative fast reactors being developed to meet the requirements.

SYNOPSIS A survey of a variety of engineering experiences including education, wartime work on gunsighting and rockets, teaching at Cambridge and MIT, research in automatic control and stepless power transmissions, lecturing in France and Holland, and directing research at the Motor Industry Research Association, some of whose principal areas of work are indicated.

SYNOPSIS In this paper, a method to compute the reference line for the surface profiles by the random process analysis is explained. This reference line is compared with the other practical reference lines, namely the electrical mean line and the envelope. This method is also an interesting and useful tool for the curve fitting analysis.

This paper describes two methods of fluid flow measurements of the differential pressure type. The first method uses a new type of linear resistor in which the flow rate is linearly proportional to the pressure drop. This linear resistor, called a pad-resistor, may be used in a single configuration when the flow rate is limited to small values. For a flowmeter of high capacity and low resistance a multi-pad multi-stage configuration, where several pad-resistors are connected in parallel, has been adopted.

The second method uses a non-linear resistor called a quad-resistor. This type of resistor has a flow characteristic proportional to the fourth order of the pressure drop. By combining the quad-resistor with an orifice, the relationship between the pressure drop and the flow rate becomes approximately linear. The quad-resistor has been used in conjunction with a fluidic analogue amplifier to give a linearized output pressure proportional to the flow rate in a fluid duct.

Reactor safety assessment is a highly specialized topic which, in many of its aspects, depends heavily on a satisfactory understanding of a wide variety of heat transfer phenomena. It is the aim of the paper to air some of these problems outside the ranks of the reactor safety specialists. Typical liquid-cooled reactors, their operating characteristics, and some heat transfer aspects of their safety assessment are discussed: for example, transient boiling, quenching of hot surfaces and thermal explosions.

SYNOPSIS Training and career development of the Chartered Engineer in the Railway Industry has changed greatly in the last fifteen years. A degree or its equivalent is now obligatory as a basis for Chartered status. Industrial experience has to be condensed and carefully executed and the development of a young man's career must be given greater attention than in the past. Much has been done in recent years, more remains to be done if the right balance in training and development is to be achieved. The authors, experienced managers in the Industry, have drawn on their experience to write a paper in which some of the answers are given, which should provoke discussion and which it is hoped will be practical and useful.

SYNOPSIS Initially the vehicle response during braking is investigated with the aid of a mathematical model having a realistic road input. Using an integrated hybrid computer, the road-tyre characteristics are simulated by generating non-linear functions on the digital computer, while the mathematical model is described on the analogue computer with parallel logic facility. An adaptive braking control system is proposed which measures and processes the rear-wheel motion. Activation of the system occurs when the wheel deceleration and a quasi wheel slip reach given reference values. The adaptive system as developed and optimised on the hybrid computer is implemented on the rear wheels of the test vehicle. The predicted values of wheel speed, brake-pressure modulation, stopping distance and vehicle yaw are shown to compare favourably with the test results.

In applications requiring simultaneous rotation about two orthogonal axes it is normal practice to employ some form of gimbal structure. An alternative solution is presented whereby the motion is obtained by a self contained two-axis hydraulic actuator. The design, analysis and manufacture of the device is discussed. Preliminary experimental tests have shown that the basic design of the device is sound. Some possible fields of application are suggested.

SYNOPSIS A system is described for low-temperature heat generation for space heating envisaging the adoption of an organic fluid external combustion engine as the direct drive for a heat pump. Waste heat from the engine condenser contributes a substantial fraction of the overall heat output. Progress in experimental work to ascertain the suitability of organic fluids to operate at comparatively high temperature without appreciable decomposition or corrosive action on materials is reported. Results are given of a computation program predicting the performance of systems of various capacity. For the examples considered yearly fuel consumption was calculated to range between 41 and 48% of that of a conventional plant.

SYNOPSIS A computer controlled diesel engine test-bed is described. The system is capable of excursions into regions of very low air-fuel ratio operation without damage to the engine; this enables the engine “steady-state” characteristics to be measured for off-design operating conditions. A computer-based data acquisition system was developed to acquire test-bed results under engine transient operating conditions. An analogue computer model of the engine was constructed using the steady-state characteristics of the engine as obtained from on- and off-design. This model operated in real-time and was suitable for both studies of engine control systems and the testing of control hardware. Results obtained from the test-bed and the model are compared. It is shown that good agreement can be achieved by minor modifications to the model based on steady state results.

SYNOPSIS This paper traces the evolution of the velocity gradient factor as the most appropriate boundary-layer laminarisation criterion as a prelude to examination of its advantages over the original and modified Pohlhausen parameters for laminar boundary-layer situations involving positive and negative pressure gradients. The velocity gradient factor, which involves only directly-measurable quantities, appears a more sensitive indicator of changes in other parameters over a wide range of flow models, including the onset of transition in the presence of significant mainstream turbulence.

SYNOPSIS The unsteady boundary layer behind a moving shock wave in a rectangular duct 7.62 cm wide × 5.08 cm high has been studied using a high quality schlieren system. Growth of the boundary layer has been compared with the results of calculations for laminar and turbulent flows. The experimental results indicate that three dimensional effects are present which cause, in some cases, very early transition from laminar to turbulent flow. Agreement with theory is satisfactory only in the case of the weakest shock wave examined although the trends in growth rates generally conform to theoretical predictions.

SYNOPSIS An analysis of orthogonal skiving is presented which includes the previously omitted effects of machine deflections and non-circular final geometry. Also the skiving process is shown to be a useful method for the rapid accumulation of data on cutting forces. The method uses fewer tests than would be required using conventional methods and the data are shown to agree well with those obtained by such conventional methods. Finally predictions are made of force variations during a skiving cut and also of the final geometry of the workpiece and these are found to agree well with experimental results.

SYNOPSIS The bedplate, column, cylinder casings, bearing caps and crankshaft of a model of one bay of a Vee type medium speed Diesel engine have been made in epoxy resin and joined by compression springs simulating the appropriate bolt forces and stiffnesses.

The model has been loaded by freely hanging weights simulating firing and reciprocating inertia forces and subjected to frozen stress loading. Stresses obtained from numerous slices cut from these components are analysed and related to the designer's qualitative understanding of the load paths.

Static and cyclic creep tests have been carried out on a 1 Cr Mo V steel at 565 °C. In addition, the effects of prior high strain fatigue on subsequent creep behaviour has been studied. A well defined ductile/brittle transition was noted which was unaffected by the type of load controlled cycle. The material softened under cyclic plastic strain and no experimental evidence was obtained which indicated that fatigue and creep damage interacted in a load controlled test to give rise to unexpectedly short lives. The conclusion derived is that “softened creep” data should be used in predictions of deformation and rupture behaviour, and that the use of virgin creep data can give rise to substantial errors.

A 1 Cr Mo V steel has been studied at 565 °C under a cyclic strain axial mode with various combinations of tensile and compressive dwell periods. Compared with the continuously cycled data, the presence of a tension only dwell caused a considerable decrease in the number of cycles to failure. The addition of a compressive dwell to the cycle already containing a tensile dwell tended to reduce or eliminate the harmful effects of the latter. Metallographic evidence suggests that the compressive dwell reduced the incidence of internal intergranular cracking. A ratchetting grain boundary damage model to account for this is proposed.

Predictions of the behaviour of a 1 Cr Mo V steel at 565 °C under cyclic strain plus dwell conditions have been carried out. The strain hardening mechanical equation of state appears to be useful under virgin material conditions but the presence of cyclic softening can cause major errors. Reasonable success was obtained in predicting “softened creep” curves from the virgin creep data and the cyclic stress strain curve. Both strain and time are important in life prediction and a method is proposed which combines the strain range partitioning approach and a modified form of cumulative damage method. Predictions under various combinations of tensile and compressive dwell have been presented.

SYNOPSIS The pressure losses arising from the flow through internal flow systems are usually estimated by subdividing the system into elementary components, assigning a loss to each component, and then summing these individual contributions. This approach can lead to appreciable errors when the components are sufficiently close to one another for interactions to occur. As a contribution to the discussion of this complicated subject, this paper is concerned with the steady, turbulent flow through combinations of bends and diffusers.

Under some circumstances the combined losses of the interacting components are greater than the sum of the individual losses in interference free flow. In other circumstances the reverse is the case. However, as this paper demonstrates, in all cases it is possible to produce sound physical reasons for the variations and, as a consequence, it is possible to generalise the results to interactions involving other components in combination. The paper concludes with a list of broad design principles which have wide application to systems in which interaction effects are important.

SYNOPSIS A numerical method that involves setting up equations to express the heat balance at every region in the clutch is used to determine the temperatures at various elements when band contact occurs between the rubbing surfaces during the operation of an automotive clutch. Temperature calculations have been made for contact areas of different band width on the two clutch facings and the results obtained compared with those attained when complete contact occurs. Both single and repeated engagements made at regular intervals are considered.

The design of mechanisms for use in practical machinery applications is often of a trial-and-error nature based on traditional practice. Much emphasis has been given to the theory of mechanisms in recent years but this has yet to find wide practical application.

This paper is a case study of how a basic idea, conceived by University-based inventors and intended to improve a slow method of making a textile pile fabric, became a reality in the form of a completely new type of high-speed textile machine for making an improved textile product, all within a time scale of four years.

It also shows how recent University researches are further advancing its potential from both the machinery manufacturing and textile technology aspects.

Step-by-step from the early experimental stages, it illustrates how the challenges of developing the novel mechanisms required for this unconventional machine and process were met by combining practical experience of traditional machinery design with theoretical investigations based on the new techniques of mechanism analysis and synthesis.

Experiments were carried out to ascertain the effects of a slurry on the pump characteristics. The performance of the pump depended mainly on the sizing, specific gravity and concentration of solids in the slurry. A method has been developed for predicting the characteristics of a pump when pumping a slurry, from the clear water performance of the pump and a knowledge of the characteristics of the slurry.

SYNOPSIS Measurements of turbulence kinetic energy, Reynolds stress, velocity profiles and heat transfer were made in the flow development region of a pipe. Predictions were made using a turbulent energy-dissipation rate two equation turbulence model with different assumed values of the inlet turbulence levels. Good agreement between predictions and measurements was obtained throughout the entrance region.

SYNOPSIS The determination of the torsional stiffness of a ladder frame is investigated and a comparison made between the assumptions of infinite and finite bending stiffness of the members.

A method is proposed for the estimation of the torsion constants of the members of a ladder frame and is shown to give good agreement with measured values. Stress distributions in the cross-members of a ladder frame are also determined.

Finally charts are presented to enable the torsional stiffness and stress distributions to be calculated for ladder frames comprised of channel and I-Section members.

SYNOPSIS Railwaymen commonly associate low adhesion with slightly wet rails. It is shown that solid railhead debris can cause extremely low values of wheel/rail adhesion when mixed with water or other fluids. The rheological properties of common track contaminants are examined in terms of yield stress and viscosity, concentrating on mixtures of iron oxide and water. The viscosity of these mixtures is found to increase exponentially with increasing solid content. Hydrodynamic equations are then developed to assess whether the train wheel could be lubricated by a limited quantity of viscous lubricant (i.e. railhead contamination). It is concluded that there are two explanations for low adhesion caused by debris. Solid contamination can be both sufficiently strong and pliable enough to support a wheel, yet have a low shear strength. When sufficient viscous contamination is present, however, a train wheel can be hydrodynamically lubricated with the resulting coefficient of adhesion being low.

SYNOPSIS The paper describes the results of experiments on forced convection heat transfer to water at 245 bar flowing through small-bore tubes heated at approximately uniform flux. Basic similarity criteria for forced convection to variable property fluids are established and experimentally demonstrated. An estimate of the demarcation between forced and mixed convection is arrived at by observing departures from similarity, and comparing the results with those of previous workers. Finally, some unusual time dependent wall temperature distributions are presented which suggest that axial conduction in the test section wall may be particularly important in highly variable property situations.

SYNOPSIS Development of the velocity and temperature of the flow behind a shock wave propagating in atmospheric air in a smooth rectangular duct has been followed by hot wire anemometry. Averaged data were analyzed iteratively to yield the velocity and temperature at several points. Property distributions close to the wave front are non-uniform. Far from the front, the steady velocity profile is approximately the same as for flow in a rectangular duct. The temperature profile develops in a similar manner to the velocity but it is difficult to define the boundary layer edge because the temperature decreases with time.

SYNOPSIS A torque converter is described in which the prime mover is directly coupled to a pulsator unit which produces an alternating torque. Sprag-type clutches are used to rectify this torque and to transmit it to the converter output shaft.

A developed version of this basic design for use as an automobile automatic transmission is described and theoretical and experimental performance curves are given which show that an automobile drive is possible which approaches a manual transmission for fuel consumption and performance.

SYNOPSIS Forging tests have been made using axisymmetric cavity dies with various flash geometries.

For a particular flash geometry greater ‘rise’ was obtained with thinner flash. Also greater rise was obtained on a hammer than on a press, the load requirements being greater on the higher speed machine. Modes of metal flow were similar at all preheat temperatures. Theoretical treatment of the later stages of die filling, considering metal flow to be significant only in the region of the flash land, is able to describe the main features of the experimental results.

SYNOPSIS The effect upon computational cost and accuracy of various assumptions in diesel combustion models was investigated by comparing the performance of a range of models and by comparing the results of computation with experimental results.

The nature of the interaction between a rigid spherical asperity and an asperity governed by the stress/strain law is studied. The interfacial shear stress is defined by f τ_max where 0 < f < 1, τ _maxbeing the maximum allowable shear stress at the contact. By integrating the total effect of a population of such surface asperities expressions for the total frictional forces, and the total load are derived. The value of the coefficient of friction is thus obtained and the special conditions for perfectly plastic and elastic behaviour are considered. In both cases the friction coefficient is seen to contain a term defined by the deformation and dependent on surface roughness and a term totally defined by f. Using the same model a fatigue type failure criteria is introduced to predict the volume of wear. It is then possible to produce a wear law which is consistent with experience and which includes the relationship between the wear and the coefficient of friction.

Provided that separation on the blades of a cascade takes place aft of the leading edge, the hypothesis that suction side velocity outside of an enlarged boundary layer remains constant is used as the starting point in a potential flow solution assuming that blades and enlarged bounary layers are thin compared with chord. Representing thickness, boundary layers and wake by a source distribution, an integral equation for the latter is deduced and numerical solutions are found for a nearly two-dimensional rotating radial impeller for various diffusion ratios on the suction side of the blades.

The method is valid, incompressible flow for any blade-to-blade surface that is a surface of revolution and in the presence of stream sheet thickness variation.

The theory is compared with experiments conducted on a radial impeller and good agreement with velocity distribution and impeller tip pressure rise is shown. Predictions of blade work may be obtained using a shape factor found from the experiment but loss coefficient predictions are too low. The conclusion is drawn that a three-dimensional influence is involved in the displacement growth on the impeller blades.

SYNOPSIS The air fuel mixing process in the high swirl open chamber diesel engine is simulated by a steady state gas jet injected into a steady air swirl flow. The results from the simulation show good agreement with engine studies using high speed photography.

An attempt to quantify fuel dispersion has been made through the introduction of a mixing parameter, which allows for combustion system geometry in addition to fuel jet and air swirl momenta.

SYNOPSIS The paper describes the present acoustic environment in railway passenger vehicles, and discusses the various mechanisms leading to this. The factors providing a basis for an internal noise criterion are stated, and suitable criteria for different classes of stock suggested. A more detailed discussion is presented of various problems encountered during investigation, and of the experiments and analytical techniques evolved during their solution. It is pointed out where the experience gained in this work can be applied, and also where gaps still remain to be filled by future investigation.

This year's Presidential Address departs from the autobiographical approach commonly adopted because I wish to express my views on the important issues which confront the Institution, the profession and the individual mechanical engineer in our 130th year. It is a personal testament and will be regarded as wise, opinionated or outrageous, depending on the degree of accord felt by the reader.

SYNOPSIS A time-transient nonlinear analysis has been developed to examine the dynamical limit cycle motion of a plain journal bearing. The effect of unbalance and ambient pressure on the journal limit cycle motion below and above the linearized stability threshold speed is examined.

The short bearing approximation is used, and the assumption of a 180° oil film has been relaxed. An arbitrary film extent based upon the instantaneous values of journal displacement, velocity, and ambient pressure is used.

It has been found possible to optimize the unbalance to minimize the amplitude and the force transmitted for limit cycle operation above the stability threshold speed. Below this optimum value the whirl is fractional frequency and above this value it is synchronous.

It has been found that when the journal is operating above the stability threshold speed, rotor unbalance may result in a smaller limit cycle than the balanced rotor. The effect of a non-zero ambient pressure at the optimum value of unbalance is to increase the size of the limit cycle and make the motion nonsynchronous.

SYNOPSIS This paper describes a study in which nucleation theory has been applied to the flow in turbines.

The treatment is one dimensional and use is made of friction coefficients to allow for the aerodynamic losses. The experimental results quoted have been obtained independently from tests on a model turbine. The results of a dry run have been used to obtain friction coefficients which have then been adopted in the prediction of the wet test.

The theoretical results are extracts from the computer prints out, the comparisons are with the turbine wet efficiency and the agreement obtained is remarkably good.

SYNOPSIS This paper presents the results of an investigation into the influence of rotation on the thermal and hydrodynamic characteristics of a rotating coolant circuit which has relevance to the design of cooled rotors for electrical machines. Tests conducted with a fixed pressure drop across the entire rotor circuit demonstrate that increases in rotational speed can produce consequential increases in the temperature of the simulated winding. This is true for the case where the energy dissipation is constant.

SYNOPSIS The application of Griffith energy concepts to Elastic-Plastic Fracture Mechanics (EPFM) is investigated. An elastic-plastic finite element program is used to calculate the values of the Crack Separation Energy Rate, G^Δ, corresponding to a variety of biaxial stress-strain states. The effect of the size of the crack tip plastic zone on the fracture stress is investigated and a relation is established between two non-dimensional parameters φ and ψ. The first parameter φ gives a measure of the ductility of the material while the second parameter ψ is related to the applied stress when brittle fracture occurs. The character of the φ, ψ dependence suggests that when a certain value of the ductility parameter φ is exceeded, brittle crack growth is no longer possible and the mode of crack extension must change to one of a ductile nature. The theoretical predictions of fracture toughness are favourably compared with the results of experiments. Calculated values of G^Δ, the stress intensity factor, K, and Rice's path independent integral J are also compared and the applicability of these parameters to brittle, quasi-brittle and ductile fracture is critically discussed.

SYNOPSIS

Brittle materials are usually characterised in terms of the “modulus of rupture” obtained from the results of fracture tests on beam specimens. This is not a fundamental quantity. Alternative quantities (the mean strength of unit volume and of unit area) are introduced which are independent of the size of the specimen and the form of test, which allow the correlation of results from different tests, and which may be validly used in design calculations. After an outline of the necessary theory, the derivation of the two “unit strengths” and their use in correlating test results are illustrated using fracture data from a series of reaction-bonded silicon nitride beams. Minimum values obtained are:- mean uniaxial fracture stress of unit volume, 140 N/mm² per cm³; mean uniaxial fracture stress of unit surface area, 180 N/mm² per cm².

A means of allowing for the effects of contact friction in the analysis of beam fracture test data is presented. The ignoring of these effects may result in a significant over-estimate of strength. The measured coefficient of friction decreased with increased load intensity.

SYNOPSIS A method of calculation of droplet vaporisation rates which takes into account the effects of finite injection rates and diameter distribution is presented. A simple approximate expression is derived and used to investigate the significance of these effects. It is concluded that they are both important: numerical techniques for allowing for the effects are suggested. The relevance to engine combustion performance at different speeds and injection conditions is discussed.

Starting with a review of the development of incinerator plants from simple destruction units to installations for heat recovery, the author surveys different aspects of a complex theme.

Using the concept of ‘heat production’, the composition of the refuse and the operating conditions which are important in the planning and construction of an incinerator are considered.

The paper then discusses the choice of furnace equipment and the conditions to be imposed on it, using as an example the ‘Düsseldorf roller grate system’. The configuration of the furnaces is also dealt with in the light of experience in the construction of the boilers.

Finally, under the heading ‘Operating Experiences’, facts are given about the reliability of incinerators, with special emphasis upon the problem of corrosion of the boiler-tubes.

SYNOPSIS Various considerations which need to be kept in mind when making a choice between and designing rear axles and independent rear suspensions are listed and explored, so that a sensible compromise related to the vehicle type and desired characteristics can more easily be achieved or approximated at the design stage. Methods of avoiding standing height and bounce frequency variation between one-up and fully laden are described and illustrated with reference to optional extra and initially incorporated systems. Accepting the desirability of maintaining the same relationship to critical damping over the load range, different ways of achieving it are described.

SYNOPSIS A computer program representing a shaft and rotor whirling in bearings which allows for realistic oil film boundary conditions and non-circular bearing profiles has been developed. It gave good agreement with experimental results published by Brown and France.

With the aim of increasing understanding of the influence of bearing profile on system instability, the program calculates the timewise variation of the energy in translational motion supplied to the rotor by oil film forces. One case is illustrated.

SYNOPSIS Predicting the stability of rotating systems at intermediate and large whirl amplitudes is costly. This paper suggests a cheaper' approximate method based upon an overall energy balance.

By representing the force exerted on the bearings as combinations of constant forces and cyclically varying forces, the influence of bearing geometry, and other factors on the magnitude and direction of the energy flow between oil film and rotor for a complete cycle was investigated and found significant.

It is suggested that designers should check stability of intermediate or large amplitude whirls by an overall energy balance.

SYNOPSIS A method of generating reduced order models from the Laurent series expansion of a transfer function is examined by means of the Hankel Matrix and its correspondence to the field of rational functions. The approach enables particularly simple results to be derived regarding the composition of the reduced form and the avoidance of non minimum phase characteristics therein.

Synopsis The history and development of British Railways' Advanced Passenger Train (APT) are discussed. The technical objectives are considered in the context of their value to commercial and operating performance. Among the technical aspects discussed are dynamics of guidance and suspension, aerodynamics, power and transmission, braking, and lightweight body structures. Highlights of the research and development programme are described, with reference to laboratory and track testing of the experimental train (APT-E) and associated experimental vehicles. The paper concludes with a description of the design of the prototype electric train (APT-P), of which three are currently being constructed for operation on the London/Glasgow route.

Despite the fact that the world's need for fresh water is becoming more urgent, the ability to desalinate economically on a large scale still remains a goal rather than a reality. Distillation systems are by far the most widely employed systems for sea water desalination. However, the relatively high costs of these systems' products limits their competence with natural water resources, particularly for agricultural use. In this paper a distillation system is proposed. The system gives high performance ratios at low flashing ranges, which leads to a substantial saving in the distillation plants running costs. The analyses showed that the system has big thermodynamic potentialities.

SYNOPSIS

Results are presented of experimental observations made during investigation of the basic causes of vortex formation which show that air ingestion and vortex formation phenomena can be divided into three regimes corresponding to three ranges of submergence.

Simple theoretical modelling of the flow in which the suction pipe is replaced by a point sink, shows that the occurrence of vortex formation is associated with the behaviour of the surface stagnation point.

The theoretical results are compared with the extensive experimental data of Denny (4).

SYNOPSIS

Two alternative methods are described for the calculation of gas composition. These are:- 1. Complete chemical equilibrium; 2. A combination of chemical rate equations for some slower reactions with partial equilibrium for faster reactions. Some calculated results are given in the form of comparisons between the two methods, showing the changes in gas composition caused by a temperature rise and fall with a constant rate of change of temperature. Equations are also given for the thermodynamic properties of individual species which may be used together with the appropriate gas composition to obtain properties of the gas mixture.

SYNOPSIS A new theory is developed in an attempt to explain the scuffing failure of circumferentially ground discs. The characteristics of the surfaces of a particular pair of such discs just before scuffing took place have been analysed in detail. The roughness of the surfaces has been taken into account in the treatment both of the hydrodynamics and of the contact mechanics of the system.

The disc bulk temperature at which high hydrodynamic pressures just fail to be generated shows a reasonable agreement with the temperature observed just before scuffing. The implications for the mechanism of scuffing are discussed.

SYNOPSIS The geometry of current motorcycle rear suspension systems is such that the centre distance between the gearbox output sprocket and the rear wheel sprocket varies as the suspension deflects.

SYNOPSIS Failures due to on-load corrosion have occurred in the steam generating tubes forming the sloping furnace floor of a large, high pressure boiler. Measurements carried out on the operating plant have shown the cause to be tube wall dryout. The data obtained have enabled plant operating conditions to be detailed which avoid dryout. Close agreement has been shown between the plant data and the results obtained from comprehensive rig tests.