bluuebunny/crossref_metadata_2025 huggingface dataset:
Variables Affecting the Fixation of Tibial Components
Authors: Walker P S , Thatcher J , Ewald F C , Milden J
Published: February 2007

Laboratory tests were carried out on some of the variables which might affect the fixation of tibial components. The type of component with a flat upper surface and a central peg was considered. These variables were the rigidity of the upper plate, the area of surface coverage on the bone and the thickness of the cement. The strains in the cement around the peg, and the component—bone deflections were measured. For plastic, the upper plate rigidity and cement thickness made little difference, but an all-metal component reduced peg and cement strains. Complete surface coverage reduced bone—component deflections considerably. Implications to design are discussed.
The Carshalton Halo-Pelvic Distraction Apparatus
Authors: Rodwell T R T
Published: February 2007

This paper describes the design philosophy and advantages of the Carshalton single point support halo-pelvic distraction frame. The Carshalton frame has been designed to provide a reliable and accurate indication of traction force and is convenient and easy to use for both staff and patient. The unique feature of this apparatus is the single point support which allows the patient to move and turn his head.
Analysis of Parameters Affecting Impact Force Attenuation during Landing in Human Vertical Free Fall
Authors: Mizrahi J , Susak Z
Published: February 2007

The characteristics of impact forces on the legs during vertical landing of human vertical free fall in different falling conditions were studied to reveal the parameters which take part in the attenuation of these impact forces. The following parameters were investigated: body position during landing, range of flexion of the joints of the legs at impact, usage of ground-roll immediately after impact and softness of the ground.

The results indicate that joint movements and muscle action play a major role in reducing peak forces during landing. This emphasizes the importance of adequate training to improve the pre-programmed non-reflex muscle action, necessary in the early phase of impact.
Variability of Handgrip Measurements
Authors: Gillespie F C , Fisher J , Shaw A
Published: February 2007

Two calibrated grip dynamometers were used to measure left and right handgrips of seven healthy volunteers. Ten measurements were made with each instrument on each hand. The results showed that the cheaper instrument read high by up to 5 kgf and that the more expensive instrument was accurate to within 1 kgf throughout its range. The results expressed as fractions of the mean for a set showed a broadly normal distribution with the reproducibilities of right and left hand results for the two instruments for a given individual being typical ±2 kgf. A conclusion of the study is that for statistical reasons caution should be exercised in interpreting the effects of a treatment or the progress of a disease from a very limited number of handgrip measurements. It is suggested that the mean of four measurements is a realistic compromise between practicability and accuracy.
The Stability of the Human Patello-Femoral Joint
Authors: Hvid Ivan
Published: February 2007

A three-dimensional analysis of the patello-femoral resultant force vector ( ) is presented. Results of the analysis proved to be largely independent on the valgus angle of the knee. Therefore Q angle measurements will suffice for clinical analysis. The lateral direction of decreases rapidly with knee flexion when the Q angle is small, less so for larger Q angles. Consequently, the steepness of the lateral femoral trochlea required for passive stability decreases with increasing knee flexion. In the light of these findings the dynamic stabilizing action of the vastus medialis obliquus muscle is discussed. Calculations of the magnitude of showed that the traditional analysis of the sagittal projection of the joint (two-dimensional analysis) is justified.
Modelling the Femoral Load Transfer in Total Hip Joint Replacement—A Preliminary Study
Authors: Miles A W , Dall D M , Macleland B F
Published: February 2007

This paper describes a simple modelling technique used to study the load transfer in the proximal femur in total hip replacement. Model femora cast in a rigid polyurethane foam and prostheses made from various plastics were used to study the effects of individual design parameters on stresses in the femur and prosthesis. The technique was applied in this study to examine the effects on the load transfer of two geometrically identical prostheses simulating two different materials, viz. titanium and chrome cobalt. The model simulating titanium produced more physiological femoral stresses and lower stem stresses. The technique proved to be a simple yet reliable method of studying individual parameters related to the design of femoral prostheses.
Biomechanical Design of the Total Ankle Prosthesis
Authors: Calderale P M , Garro A , Barbiero R , Fasolio G , Pipino F
Published: February 2007

The load bearing joints of the human body and particularly the ankle are often seriously damaged because of different pathological events. During the last 10 years a lot of total ankle prostheses have been studied and implanted, in consequence of the inadequate results obtained by arthrodesis (i.e. the fusion of the joint).

The aim of this paper is to analyze mechanical features (functional, kinematic, and strength) of the ankle joint in order to provide optimized design criteria of an arthroprosthesis substituting the disabled joint.
Voluntary and Diurnal Variation in Height and Associated Surface Contour Changes in Spinal Curves
Authors: Goode J D , Theodore B M
Published: February 2007

Height is not a static state. The ‘standing as tall as possible’ heights of 34 females of medium height aged 18–40 were 7–36 mm greater than when they stood as relaxed as possible. All measurements were made with heels on the floor, knees extended and heels, buttocks, back and occiput against the wall. The cervical curve was always, and the lumbar curve usually, straighter with the taller height. Using the same criteria and standing as tall as possible the height on rising could be up to 18 mm greater than later in the day. The decrease in height occurred mainly in the first four hours. Full restitution occurred with a night's rest and partial restitution after relaxation or lighter work.
Ground Reaction Forces during Human Standing
Authors: Shimba Takeshi
Published: February 2007

Foundamental characteristics of ground reaction forces measured by using a force plate during human standing were investigated. Force fluctuation levels and power spectrums of the force data for standing posture were compared with those for sitting. The force fluctuation levels in the horizontal plane and their time varying characteristics were evaluated by using an index of short time interval variance (SIV). Three curves, denoted by A, E, and G, approximating change with time of the centre of gravity of the body were calculated from the force data and traces of these curves were compared.

The fluctuation levels of forces in relaxed standing were not so high as those during sitting. The value of SIV and its mid-mean value for each measured data appeared to be useful to represent the force fluctuation level in the standing posture. The curves A, E, and G were well fitted as a whole and each of them can be estimated, more or less, an approximation of the true curve of centre of gravity unless the body movement is not so vigorous.
The Load Bearing Capacity of Vertebral Cancellous Bone in Interbody Fusion of the Lumbar Spine
Authors: Pearcy M J , Evans J H , O'Brien J P
Published: February 2007

Interbody fusion involves the grafting of bone between the vertebral bodies themselves. The bone graft is considered to be load bearing post-operatively, and it is necessary to know how large the transverse sectional area of the graft should be in order to sustain the loads on the spine, post-operatively, before bony union is attained.

The cancellous bone of the vertebral bodies has previously been shown to be the weakest element of the grafted spinal segment and a series of compression tests on cadaveric material was undertaken in order to determine the size of graft required to distribute the compressive loads so as not to exceed the failure strength of the vertebral bone.

The results suggest that at least 0.4 of the transverse sectional area of the vertebral bodies should be covered by the graft for the fused segment to sustain axial loading post-operation.

Local trabecular fracture due to incongruency of the graft/vertebra surfaces and slight movements at the grafted joint is proposed as a mechanical reason for delayed union.
Ten Years of Experience with test Criteria for Fracture-Proof Anchorage Stems of Artificial Hip Joints
Authors: Semlitsch M , Panic B.
Published: February 2007

Since loosened femoral component stems are subjected to severe stresses, the material of which the stem is made becomes over-stressed and this may eventually result in an absolutely undesirable fatigue fracture of the loosened stem. Extensive static stress measurements performed along the lateral aspect of simulated loosened stems of various hip prosthesis types yield load/stress curves for determining the safety factor for the structural strength of the stem design. Decisive for the safety against fracture of a loosened femoral prosthesis stem is, ultimately, the dynamic pulsating fatigue test at up to 5 × 106 load cycles in Ringer's solution. Under the given test conditions as many as 2000 hip prosthesis stems have been subjected to 5–10 million load cycles over the last ten years, and minimum requirements have been laid down for the fracture-safety of these components under conditions of loosening in the body. The experience gained over a period of ten years with more than 500 000 series-produced fracture-proof anchorage stems strongly suggest that these test conditions should be standardized nationally and internationally.
Biomedical Engineering Teaching and Research at the Centre for Biomedical Engineering, University of new South Wales, Kensington, Australia
Authors: Farrell P C , Flicker W , Svensson N L
Published: February 2007

The Centre for Biomedical Engineering is a postgraduate facility which is unique within Australia in terms of the breadth of its research activities.

The postgraduate training of biomedical engineering professionals is a major objective of the Centre's programme; training and research is provided not only for graduates with engineering backgrounds, but also for those with medical, biological, and physical sciences background. The output of Masters and PhD graduates is approximately 15 per annum.

Predominant research areas are in the mathematical modelling of medical treatment such as optimization of artificial kidney and plasma exchange therapies, application of microprocessors and computers to medical problems, investigation of respiratory and cardiovascular dynamics, and improvement of orthopaedic implants. Studies in rehabilitation engineering, biomechanics, hormonal control systems, and neurophysiological modelling are conducted in associated departments.
The Present State of Biomechanical Research in Orthopaedics in Japan - an Observation by an Orthopaedic Surgeon
Authors: Terayama Kazuo
Published: February 2007

Although lacking a comprehensive knowledge of the entire field, especially of bioelectronics, the author describes briefly the present state of orthopaedic biomechanics, biomaterials, and biotribology in Japan.
An Idealized Element Model of Human Skin
Authors: Gunner C W , Burlin T E , Hutton W C , Magureanu R
Published: February 2007

A theoretical model of the skin is developed to model the results obtained from uniaxial in vivo tests. The model, which exhibits non-linear viscoelastic behaviour, is based on idealized representations of the skin's structure.
Design, Development, and Clinical Trial of a Modular Elbow Replacement Incorporating Cement-Free Fixation
Authors: Amis A A , Miller J H
Published: February 2007

This paper describes the design process leading to a total elbow replacement with components which have an accurate anatomical shape and require minimal bone resection. This allows a ‘modular’ approach to elbow reconstruction, i.e., radial head replacement alone, humeral hemiarthroplasty, humero-radial or ulnar replacement, or total (three component) reconstruction. This approach means that the surgeon may choose to replace only the damaged joint surfaces, rather than being committed to total replacement.

The parallel development of instruments for accurate bone forming is also described, allowing firm and precise fixation of prosthetic components without bone cement, a necessity for interlocking bone ingrowth to occur without extended immobilization.

A clinical trial of these components, in more than fifty patients for periods up to five years, is reviewed, showing the restoration of pain-free stability and greater ranges of motion than have been reported for other elbow replacement devices, and with no incidence of prosthetic removal caused by painful loosening.
Porous Titanium Dental Implants in Primates and Humans
Authors: Young F A , Keller J C
Published: February 2007

A series of 30 cylindrical implants employing sintered powder metal exteriors to promote bone ingrowth have been employed to support bridges and crowns in Rhesus monkeys for periods exceeding 36 months. Clinical indicators demonstrated successful function during the period of the experiments for 24 of the 30 implants. The four implants which did not perform well clinically were analysed by histology and found to be locally infected. Implants retrieved at various times after function were analysed by histomorphometric techniques. In all successful implants bone had grown into the porous exterior of the implant and was found to be supporting the loads of mastication. Long term bone remodeling under stress was evaluated quantitatively. It was found that for periods of function exceeding three years, remodeling which was not present in one and two year specimens was detectable. Clinical success was attributed to stabilization accomplished by the bone ingrowth. Clinical and histological results were analysed using a computerized data handling system, and correlations between histology and clinical performance were attempted.

In human experiments eight patients have received implants which will support bridges used as distal extensions in the mandible. At this writing, the results are short term and comparison with the animal experiments difficult.
Fracture Healing Assessment with External Fixation
Authors: Churches A E , Tanner K E , Evans M , Gwillim J
Published: February 2007

The increased use of external fracture fixation has brought a need for improved methods of assessing bone healing while the fixator is still in place. In this paper, a method using a strain gauge transducer clamped to the support column of the Oxford External Fixator is considered. Experimental strain gauge data are found to agree very closely with the theoretical analysis for a range of fracture stiffnesses, and to provide a useful measure of progressive bone healing. Bone pin loosening during the course of fracture healing is shown to have a significant effect on the assessment, typically decreasing the strain gauge data by 20 per cent for one loose pin and by 55 per cent for two loose pins. The effects are such that pin loosening could erroneously be interpreted as increased fracture stiffness. Methods are given for correcting the strain gauge data to account for loose pins.
Simulation of Tendon Transfer Surgery
Authors: Dul J , Shiavi R , Green N E
Published: February 2007

A biomechanical model is used to simulate a tendon transfer operation. The model predicts the required forces in twelve ankle muscles during standing and walking, and also the endurance time of the (instantaneous) posture. In particular, the mechanical effect of anterior transfer of the posterior tibial tendon of a patient with muscle paralysis due to peroneal nerve injury is studied.

The results show that before surgery the patient can stand normally but cannot walk normally. Normal walking is mechanically not possible because the required muscle forces in early stance cannot be produced, although the necessary forces can be realized during the remainder of stance. After surgery, both normal standing and normal walking are mechanically possible. The cost is higher forces and shorter endurance times in the healthy muscles. The results agree with clinical findings.
Material Properties of Cancellous Bone in Repetitive Axial Loading
Authors: Linde Frank , Hvid Ivan , Jensen Niels Chr.
Published: February 2007

Machined cancellous bone specimens from human cadaver knees were tested under repetitive nondestructive axial compression. Loads were applied up to 50 per cent of the ultimate strength of the specimens predicted from their mineral content measured by photon absorption technique. The stiffness increased greatly between the first two compressions, and thereafter asymptotically approached a constant level. There was a 44 per cent median increase in the modulus of elasticity from compression No. 1 to compression No. 10. Steady state was apparently reached after the fifth compression with intervals between compression cycles of not more than 2 minutes. The results were reproducible, and the precision of the modulus of elasticity determined by double measurement at compression No. 10 was Ē ± 9.8 per cent (95 per cent confidence limits). The modulus of elasticity at steady state determined as the mean of compressions 6–10 was found to be Ē ± 5.6 per cent (95 per cent confidence limits). With both methods there was a strong linear correlation between the ultimate strength and the modulus of elasticity. The correlation coefficient was r = 0.95 ( p < 0.005) and r = 0.99 ( p < 0.001), respectively.

Due to the calculation error the figures for ultimate stress (US) in Table 2 and Fig. 4, and ultimate stress derived from the regression equations in Table 3 are reduced by a factor of two.

The present technique allows studies of viscous properties without engaging in otherwise time-demanding creep studies; yet in order to approach the issue quantitatively, the technical arrangement must be more meticulously prepared. Studies of viscous properties may, however, be of importance to evaluate the damping effect of cancellous bone and its role in the musculo-skeletal damping system.
A Study of the Feasibility of Using Adhesive Tapes for the Long-Term Relief of Tension from Healing Surgical Wounds
Authors: Gill J M , Bowker P
Published: February 2007

The feasibility of the long-term relief of tension from healing wounds by the application of adhesive tapes has been investigated. The characteristics of a tape which would be suitable for this purpose are described and the results of in vitro and in vivo tests on several currently available products are reported. It is concluded that a satisfactory tape for the long-term relief of tension from a wound is not yet available.
Some Gait Characteristics of Below-Knee Amputees and Their Reflection on the Ground Reaction Forces
Authors: Seliktar R , Mizrahi J
Published: February 2007

Human locomotion studies employing cinematography and force plates have been conducted during the last five decades with the goal of producing a clinically acceptable gait evaluation technique. The bulk of information contained in the kinetic studies was the major obstacle in achieving this goal. Our aim in this work was to explore the possibility of representing some locomotor abnormalities solely by their reflection on the ground reaction force characteristics. As a first stage towards the establishment of these relationships, the gait characteristics of below-knee amputees were examined.

One hundred and thirty ground force test results as obtained on twenty three below-knee amputees were analysed. Different variables such as time durations of the various phases, peak forces, impulses, rate of change of the forces, and others, were examined. The conclusions suggest that some of these variables are suitable for evaluation of gait and some, such as small perturbations superimposed on the curve, may serve as indicators of specific malfunction of the prosthetic system.
A Novel Data Compression Technique for Electrocardiogram Classification
Authors: Ibiyemi T S
Published: February 2007

A novel high data compression of ECG data in the measurement space by clipping the signal and using the zero-crossing intervals as features. This yields low-dimensional features sufficient and efficient for screening and some diagnostics. It is validated by experiment using ECG of an in vitro heart of a rat. This new idea is built around a Z-80 microprocessor.
Anatomical Definition and Modelling
Authors: Duncan J P
Published: February 2007

Methods of measuring and replicating elements of human anatomy as models formed by machining to aid surgery and for prosthetic applications are reviewed from their historical development up to contemporary practice.
Load Bearing Capacity in Total Ankle Joint Replacement
Authors: Jensen N C , Hvid I
Published: February 2007

The influence of some simple design variations on the compressive load bearing capacity of tibial and talar prosthetic components in total ankle joint replacement were investigated in an attempt to suggest improvements to current prosthetic designs.

Eighteen paired ankle joint preparations were fitted with three types of tibial components and two types of talar components. The tibial component with an intramedullary peg tolerated significantly higher loads before mechanical failure than the two other designs that were equal in load bearing capacity. The mean value of ultimate force was 40 per cent higher and the mean value of yield force was 15 per cent higher. However, for the coefficient of stiffness there was a significant fall of 18 per cent in the mean value. The talar components were equal in load bearing capacity and stiffness.
Some Experimental Results concerning the Mechanical Coupling in Endoprosthetics
Authors: Gola M M , Gugliotta A
Published: February 2007

The work continues and completes an earlier work (Gola and Gugliotta, 1982). The refined model of a special transducer-stem is here used, after implantation in a dry bone, for two purposes. First, to confirm a recent numerical finding which states a stress equivalence between physiological loads on a prosthesis-femur system and a simplified load condition, more desirable for testing purposes. Second, the separate effects of throchanteric muscle forces and of femural head forces on the stresses in the prosthetic stem are shown at various angles; superposition of effects compares well with the physiological loading case.
Laboratory Testing of Prosthetic Heart Valves
Authors: Reul H , Giersiepen M , Knott E
Published: February 2007

A whole range of laboratory testing methods for prosthetic heart valves, such as steady flow testing, pulsatile flow testing, and fatigue testing, are presented. Comparative test results for various valve types are given and relative valve performance is discussed.
A Mathematical Model of the Locomotor Apparatus
Authors: Calderale P M , Scelfo G
Published: February 2007

This study presents a mathematical model for the musculo-skeletal system of the locomotor apparatus. Muscle forces and joint reactions are calculated for the static problem of leaning and squatting and for the dynamic problem of walking on a level surface. Muscle forces thus calculated are compared with electromyographic (EMG) patterns.

The model follows previous statically indeterminate mathematical models, from which it differs chiefly in introducing intermediate constraints (in addition to the points of insertion) for the muscles, and in setting bounds on muscle tensile stress depending on system geometry, kinematics, and loading.
The Thermal Properties of Human Cortical Bone: An in Vitro Study
Authors: Ranu Harcharan Singh
Published: February 2007

In vitro thermal properties of human cortical bone have been measured using a specially developed technique. The technique enables accurate measurement of the coefficient of thermal expansion and contraction and the average values have been measured to be 27.5 ± 3.9 × 10−6 mm/°C for expansion and 27.2 ± 5.2 × 10−6 mm/°C for contraction.
The Development of a Scleral Applicator for the Irradiation of Choroidal Melanoma
Authors: Frost R B , Karolis C A , Billson F A
Published: February 2007

The development of a simple and efficacious ophthalmic applicator for the irradiation of choroidal melanoma and other intra-ocular tumours is described, together with early surgical experience.
Frictional Properties of Artificial Hip Joints
Authors: Unsworth A , Pearcy M J , White E F T , White G
Published: February 2007

A new generation of hip replacements has been designed incorporating compliant layers to promote fluid film lubrication when the joints are implanted in patients. Tests in the Durham hip function simulator show that the friction in these joints is up to an order of magnitude lower than in currently used prostheses, and because this is due to complete separation of the rubbing surfaces, wear ought to be vastly reduced.

Experiments have shown that the best results are achieved with compliant surfaces of hardness between 4 and 8 N/mm2. Such surfaces produce coefficients of friction of the order of 5 × 10-3.
Opto/Computer Methods Applied to the Evaluation of a Range of Acetabular Cups
Authors: Atkinson J T , Burton D R , Lalor M J , O'Donovan P C
Published: February 2007

Non-contact optical measurements have been made for acetabular cups of both the Charnley (worn in vivo) and Stanmore (simulator worn) types.
Wear and Contact Stress Studies of the Minns Meniscal Knee Prosthesis
Authors: Minns R J
Published: February 2007

This paper describes the results of wear testing and contact area studies of a Minns meniscal knee prosthesis and compares the results of previous work on wear and contact stress studies of other knee prosthesis designs.

Although stresses that arise at the surface of the polyethylene meniscus components are large, after repetitive loading the contact area rises, as a consequence of plastic flow and creep, and they reduce to a fifth of the initial stress after 1 million cycles. Contact area studies show that asymmetrical loading of the meniscus give proportionally high stresses on the higher loaded meniscus and, at large values of flexion, have similar values to a more conforming but fixed polyethylene tibial component design of knee prosthesis.
A Refinement in the Calculation of the Characteristics of a Shrink-Fitted Assembly Loaded in Torsion
Authors: Severn R. T.
Published: February 2007

In an earlier paper, (1)†, the characteristics such as slip, depth of slip, and stiffness, of a shrink-fitted assembly loaded in torsion were obtained on the basis of shrinkage pressures which were assumed to be constant along the contact interface. This short paper investigates, in more detail, the shrinkage-pressures close to the end-point of contact and uses these pressure-values to refine the calculation of depth-of-slip in a shrink-fitted assembly loaded in torsion. It is shown that the refinement has an appreciable effect on the depth of slip and, therefore, on the other torsional characteristics.
Effect of Hydrostatic Pressure on the Direct-Stress Fatigue Strength of an Alloy Steel
Authors: White D. J. , Crossland B. , Morrison J. L. M.
Published: February 2007

This paper describes tests in which specimens are subjected to cyclically varying direct stress, that is, in ‘push-pull’ with additional tensile and compressive mean stress, both at atmospheric pressure and also while the material is subjected to ambient fluid pressure of the order 3000 atm (20 ton/in2); for this work a novel testing machine was developed.

The results of tests at atmospheric pressure are in good agreement with earlier tests and show that the range of direct stress leading to fatigue failure is a continuous function over the range of mean stress used. When fluid pressure of 20 ton/in2 is superimposed on the stress system, the range of reversed stress required to cause fatigue failure is increased by a small, but definite, amount. For the tensile mean stress values investigated the fatigue limit appears to have been raised until it coincides with the range of stress required to cause ‘gross yielding’ with a reduction in area greater than that which occurs in a static tension test at atmospheric pressure. For the compressive mean stress values investigated, fatigue failure has been entirely eliminated.
The Vibration of Rotating Shafts
Authors: Bishop R. E. D.
Published: February 2007

This paper is the first of a series whose purpose is to relax the usual assumptions in the analysis of shaft vibration. The formulation of a more complete theory suggests a method of balancing flexible shafts, a fresh approach to problems of stability and a way of allowing for bearing characteristics; it also suggests methods of allowing for lack of axial symmetry. Following a suggestion due to Johnson (1, 2)†, the theory is developed in simple terms. Use is made in this exposition of the mechanical analogy which exists between an initially bent shaft and a simple conical pendulum whose point of support is given a circular motion in a horizontal plane.
Stress and Deflection Studies of Flat-Plate and Toroidal Expansion Bellows, Subjected to Axial, Eccentric or Internal Pressure Loading
Authors: Turner C. E.
Published: February 2007

Tests in axial compression, eccentric (hinge) loading and internal pressure are described for corrugated-pipe and flat-plate bellows. Strain gauge surveys and deflection readings were made for each test. A recently developed theory for the small elastic deflection of toroidal elements is briefly described and its application to a wide range of bellows shapes and loadings is discussed. For some flat-plate bellows, where the depth of convolution is much smaller than the overall radius of the bellows, an approximate theory neglecting circumferential effects is possible, and comparison is made between this approximate and the more exact theory.

Both theory and experiment show that the location of the maximum stresses depends markedly upon the proportions of the bellows. General bellows design and construction problems are examined in the light of the stresses likely to be caused by actual service conditions of operation.
Experimental Determination of the Centre-of-Flexure and Centre-of-Torsion Co-Ordinates of an Asymmetrical Aerofoil Cross-Section
Authors: Carnegie William
Published: February 2007

The differential equations of motion (1)† of a vibrating cantilever blade contain coupling terms dependent upon the co-ordinates of the centre-of-flexure relative to the centroid of the blading cross-section. Complete solution of the equations, therefore, requires a knowledge of the co-ordinates.

The general theoretical problem of flexure of a cantilever blade has not yet been solved but a solution (2) based on St. Venant's theory of torsion is available for the case of a blade of uniform cross-section with symmetry about one of its principal axes but asymmetrical about the other. The accuracy of the theory is confirmed by experiment (***3). The present paper describes an extension of the flexure experiment to the case of a blade of asymmetrical aerofoil cross-section, the most usual form of cross-section found in turbine and compressor blading. For a cross-section with symmetry about one of its principal axes but asymmetrical about the other it has been shown by reasoning and confirmed by experiment (3) that, providing the root fixing is encastré, the centre-of-flexure is coincident with the centre-of torsion. A second experiment is presently described in which the centre-of-torsion coordinates are determined when the cross-section is asymmetric. Close agreement is shown to exist between the co-ordinates of the centre-of-torsion and those of the centre-of-flexure of the asymmetrical aerofoil cross-section blade.
Design of Small Isolator Units for the Suppression of Low-Frequency Vibration
Authors: Tobias S. A.
Published: February 2007

The customary linear vibration isolators are unsuitable for the suppression of low-frequency vibration in applications where, in addition to steady-state vibration, the danger of shock excitation exists. Linear suspensions which ensure a low natural frequency are necessarily very soft and, as a result, excessive large deflections will arise during steady accelerations or shock excitation. These undesirable features are not encountered with symmetrical nonlinear suspensions, which under steady state vibration excitation behave like linear springs, but when suffering large deflections from their ‘working point’ become progressively stiffer. One of the spring elements which has the required spring characteristic is the ‘sine spring’. The properties of this spring element are summarized and the various ways of coupling sine springs and ordinary springs are discussed. Several designs of isolator units, incorporating sine springs for the vertical degree of freedom and leaf springs for the horizontal degree of freedom are described.

The Appendices contain a short discussion of various ‘constant-force’ springs suitable for low-frequency suspensions, a description of the experimental equipment used, and some experimental results regarding the behaviour of sine spring suspensions.
Interior Receptances of Beams
Authors: Gladwell G. M. L. , Bishop R. E. D.
Published: February 2007

The usefulness of the receptances of beams has been demonstrated elsewhere; they permit, for instance, the calculation of natural frequencies of rigid-jointed frames from standard tables by simple routine methods of arithmetic. For many purposes it is convenient, if not essential, to use the receptances in closed (as opposed to series-) form. Tables of receptances in closed form have been confined to those measured at and between the ends of beams or between the ends and interior points along the length. A knowledge of receptances measured at and between interior points, however, may shorten calculations considerably. A method is explained for finding these quantities and tables of results are presented for uniform beams. Experimentally determined results confirmed the accuracy which was easily obtainable with the data presented.
Effect of Flow Pulsations on the Drag of Baffles in Pipes
Authors: Cox M. , Bayley F. J.
Published: February 2007

This paper describes two complementary investigations into the factors affecting the pressure loss across flame-stabilizing baffles. In the first a series of tests made under ‘cold’ and burning conditions is reported, and it was found that except when very high rates of heat release were utilized, observations made in the cold and burning tests were compatible. It was suggested that the large increases in loss observed in certain cases were due to the effects of flow pulsations. The second investigation, made under more controlled conditions, confims this, and a simple quasi-steady theory of the effects of the pressure fluctuations is found to account wholly for the results obtained.
Intermittent Release of Smoke from Chimneys
Authors: Turner J. S.
Published: February 2007

Dimensional arguments and the results of recent laboratory experiments are used to show that a considerable increase in the height attained in a calm stable atmosphere could be expected if the effluent were forced out of chimneys at high velocity in discrete puffs, rather than continuously. Numerical values are given for the final height, the size of the chimney and the optimum storage and release times under various conditions. An important application is likely to be to noxious gases which could be removed to a safe height with very little mixing into the atmosphere at lower levels.
Temperatures Reached in Disc Brakes
Authors: Newcomb T. P.
Published: February 2007

A solution is given to the problem of the conduction of heat through an infinite slab bounded by parallel planes, initially at zero temperature, when unit area of each surface is subjected to a flux which decreases linearly with time and loses heat at a rate which is proportional to the temperature at that surface. This solution can be used to determine the transient temperatures reached during disc braking at uniform deceleration if it is assumed that all the heat flows into the disc. Both cooled and uncooled brake discs are considered and typical curves are given showing the agreement between the temperatures determined theoretically and experimentally at the friction surface during single brake applications.

The problem of repetitive braking at regular intervals is also discussed and a comparison made between the disc brake and the drum brake under similar conditions. Consideration is also given to the problem when no assumptions are made concerning the manner in which heat is shared between disc and pad.
Vibration Characteristics of Stiffened Plates
Authors: Kirk C. L.
Published: February 2007

This paper describes methods of calculating natural frequencies of free flexural vibration of rectangular plates which have stiffeners parallel to one edge.

An approximate frequency equation is derived for a clamped plate with closely spaced stiffeners by extending the Rayleigh method as applied by Warburton (1)† to rectangular isotropic plates. For a plate containing a single central stiffener, an exact frequency equation is derived for simply supported edges and an approximate fundamental frequency equation is derived for clamped edges. Comparison between observed and calculated frequencies is made and the practical effect of stiffening upon natural frequencies is discussed. The application of the Rayleigh method to the calculation of natural frequencies of integrally stiffened plates is illustrated by calculating frequencies determined by Hoppmann and Thorkildsen (2).
Localized Loads Applied to a Spherical Pressure Vessel through a Cylindrical Insert
Authors: Bailey R. , Hicks R.
Published: February 2007

A solution is obtained for the membrane and bending stresses in a thin spherical shell due to the action of a localized bending moment or radial load which is applied through a thin cylindrical insert, for example, a duct connection on a reactor pressure vessel. The stress distribution will be affected by the nature of the duct to vessel connection. In this paper attention is confined to the case of an unreinforced junction as sketched in Fig. 1. The solution is general in so far as it is reduced to a set of four simultaneous equations which can be solved readily when dealing with practical problems.

As a numerical example, the case of the Hunterston reactor pressure vessel is considered, and it is shown how the localized stresses are affected by a change in duct thickness. Furthermore, these stresses are compared with those which would be induced in the sphere if the duct insert were rigid. It is found that in this practical example, the cylinder thickness has a significant effect on the calculated values for the stresses and displacements.
Determination of the Area of Friction Surfaces of Automotive Vehicles
Authors: Newcomb T. P.
Published: February 2007

Expressions for the temperature rise in drum and disc brakes are given for both single stops and regular repeated applications when cooling is taken into account. It is shown how these expressions enable the area of the braking path to be calculated if the temperature is not to exceed a specified value. The effect of the dimensions and the thermal properties of the brake components on the rate of temperature rise and on the limiting temperatures reached during a series of applications is discussed. Finally it is shown how random braking can be reduced to equivalent cyclic applications, and the braking area of a small sports car being driven in the Alps is calculated.
A Semi-Theoretical Solution of Asymmetric Heat-Transfer in Annular Flow
Authors: Barrow Henry
Published: February 2007

A brief account is given of the analogy between the transfer of heat and the transfer of momentum. For asymmetric heat transfer in annular flow, the distributions of friction and thermal flux associated with the transport processes are considered. By simplifying the equations describing these distributions, and using an observed experimental fact concerning the temperature profile, the analogy is modified to apply to the annular flow with a fluid having a Prandtl number equal to 1.

The modification results in additional factors in the final form of the conventional heat-transfer equation. These factors are functions of the annulus radius ratio parameter. A comparison is made between the final result and the recommendation of a well known authority.
An Investigation of the Pilger Process by a Plane Strain Analogue
Authors: Sansome D. H. , Lloyd H. K.
Published: February 2007

A review of the important papers and patents on the pilger process of hot-rolling seamless tubes shows that there have been divergencies of views as to the most desirable type of roll profile to use, and that there is an incomplete knowledge of the loads and torques involved.

An apparatus to simulate successfully the pilger process under plane strain conditions using lead as the working material, and to measure load, torque, and speed was adapted to a milling machine. The choice of a two-dimensional analogue was made in order to eliminate some of the many variables that occur in practice.

The work has shown how such factors as roll profile, amount of reduction, and feed per blow affect loads and torques, and that under given conditions the parabolic cone is more desirable than the hyperbolic. It is pointed out however that in practice it does not necessarily follow that the cam requiring the least power per blow, or generating the lowest peak load or peak torque, produces the most acceptable tube. A theory has been developed to enable loads and torques to be predicted for the plane strain analogue based on Hill's indentation theory.
Power Flow and Loss in Differential Mechanisms
Authors: Macmillan R. H.
Published: February 2007

The fundamental relations (connecting the torques, the velocities and the power flows) for a general differential mechanism of imperfect efficiency are newly derived from first principles. The power flow relations, which have not previously been published, are shown to be a useful tool for the analysis of complex chains of differential gears and they also permit the immediate derivation of the efficiency of all the inversions of an epicyclic gear. The range of applicability of the power relations is investigated and clearly defined, and results obtained by their use are tabulated.
Elastic, Post-Buckling Behaviour of a Simply Supported Circular Plate
Authors: Sherbourne A. N.
Published: February 2007

A numerical method is presented for the elastic, post-buckling behaviour of a simply supported, mild-steel circular plate loaded in uniform compression around the edge of the plate. Such a procedure obviates the solution of the orthodox von Kármán large deflection equations, substituting, instead, a step-by-step integration of the differential equations of equilibrium and testing at each step to satisfy prescribed boundary conditions. The equations are programmed for a high-speed digital computer and the overall behaviour of the plate is obtained in terms of the applied edge load and the central deflection. The programme is evaluated for various plate sizes, and the edge load and central deflection are related through contours of moment and thrust at the centre of the plate.
Notes on Incremental Collapse in Pressure Vessels
Authors: Edmunds H. G. , Beer F. J.
Published: February 2007

A few simple cases of incremental collapse are reviewed in the context of the design of pressure vessels. Incremental shakedown and limited-life design in terms of an allowable aggregate strain are considered. It is suggested that incremental collapse will commonly impose limitations on design which will be much more severe than high strain endurance. However it is considered that this may not be true if the high strain fatigue is complicated by questions of creep relaxation.

Simple results are presented of two selected examples of exploratory experiments, one illustrating incremental collapse in a pipe bend, and the other incremental shakedown in a tie-plate.
Three-Dimensional Design of Multi-Stage Axial-Flow Compressors
Authors: Railly J. W.
Published: February 2007

The design of multi-stage axial-flow compressors, particularly where the blade rows are closely spaced, presents a problem to the designers owing to the mutual interference of the separate blade rows. The actuator disc approximation, applied to the design of single stages at a time has been shown to be useful, and this technique can be used for the multistage machine if the mutual interference of the separate stages may be neglected. Carmichael and Horlock (1)† have carried out calculations by including only the mutual interference of adjacent rows (see also Horlock (2) for an introduction to actuator disc theory).

Using the theory of simple radial equilibrium of the flow at the trailing edges of the blade rows, it has been demonstrated, Howell (3), that the flow tends to a state which is termed the ‘ultimate steady flow’ after about two stages. The design of the third stage on a machine may be attempted, making use of this assumption, treating this stage as if it were flanked by many stages. The first part of the paper deals with an extremely simple method of design, for the ultimate steady flow, using the actuator disc theory, and a particular example of this method is compared with a more exact solution of the equations, based on a modified radial equilibrium approach. Both results are then compared with a set of experimental results taken from an experimental three-stage axial-flow compressor in the Department of Mechanical Engineering at the University of Birmingham.

In the second part of the paper, the validity of the above assumptions regarding the ultimate steady flow state is discussed, along with the problem of the ‘entry stages’. These problems may be resolved by an exact solution for the flow through a series of identical stages in which parameters such as number of stages, blade row spacing and blade row axial length may be systematically varied. Such an approach is described, and the results of a series of calculations are presented. It is shown that the overall behaviour of the entry stages depends upon the ratio of blade row axial length to blade row spacing. Thus, for small values of this ratio, the flow tends slowly to the ultimate state, but for small axial clearance the ultimate state is reached virtually by the third stage. The influence on the entry stages of blade row spacing and of number of stages is also discussed. It is shown that the treatment of the practical multi-stage machine, even for closely spaced blading, reduces to the separate treatment of the first stage only (inlet guide vanes plus one rotor and one stator), plus the ultimate steady flow treatment to obtain the behaviour of the third stage; otherwise the exact approach may be applied to the first three stages taken as a group, although this involves more calculation. On a high-speed digital computer, such as the Ferranti ‘Mercury’ machine which was, in fact, used for the calculations, a 3-stage compressor design would take about 15 minutes.