bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mathematical model for generating microplastic hysteresis loops
Authors: Esin A , Jones W J D 
Published: July 2007

A method is suggested for defining the extent of the microplasticity which can exist in a material at stresses between the ‘true elastic limit’ and the nominal yield point or proportional limit. The suggested mathematical model makes it possible to extrapolate the macroscopic plastic equation into the elastic region in order to take account of the localized nature of the plastic flow. This analysis can be used to calculate the microplastic hysteresis energy absorbed per cycle by a material under cyclic loading and with a knowledge of the total energy to fracture can be used to predict the number of fatigue cycles to failure; an example is given.
Finite-element analysis of stresses in shafts due to interference-fit hubs
Authors: White D J , Humpherson J 
Published: July 2007

Stress distributions in shafts due to interference-fit hubs are presented for shafts with various hub-seat features. For the calculations axisymmetric finite-element computer programmes were used. In a plain shaft there is a high local pressure just inside the hub face and a high axial tensile stress just outside it. These stresses are relieved by features, such as fillets or grooves in the shaft, arranged to give a raised or isolated hub seat and, of the two, a raised seat with a transition radius is more effective than a stress-relieving groove. Hubs fitted on either side of a groove reduce the maximum tensile stress compared with a single hub, while overhung hubs produce no significant change compared with flush hubs. Methods of fitting which promote axial constraint between the hub and shaft should be avoided since this leads to an increase in tensile stress in the shaft.
Effect of pre-stress on the yield and flow of En 25 steel
Authors: Rogan J , Shelton A 
Published: July 2007

Combined tension-torsion tests have been performed at constant stress ratios on En 25 steel, previously annealed and then subjected to a pre-stress in either tension or torsion. The post-yield behaviour showed marked room-temperature creep and, in general, both the axial- and the shear-strain components could be expressed by the logarithmic creep equation. The direction of the incremental strain-ratio vector was initially markedly different from that shown in the previous tests on annealed En 25 steel, but rotated towards that direction with increased stress. The yield locus subsequent to each pre-stress was established by fulfilling two requirements: that it must pass through the stress space normal to all the plastic-strain-increment vectors it encounters; that each yield stress should be an extrapolation from the curves of creep coefficient plotted against stress and stress plotted against ‘long time’ strain. The results show that a pre-stress hardens the material over that half of biaxial stress space bisected by the pre-stress axis and hardens it less or even softens it in the reverse half of that space. The cross-effect of a tensile pre-stress is greater than that of a torsion pre-stress and increasing the degree of pre-stress has a gradually reducing cross-effect.
Design of steam-turbine casing flanges: A two-dimensional photoelastic study
Authors: McKenzie H W , White D J , Snell C 
Published: July 2007

Photoelastic tests have been made on two-dimensional models of steam-turbine flanges for various combinations of the flange parameters depth, width, and bolt position. Design curves have been produced which show the relation between these flange parameters and the ratio of bolt force to pressure force necessary to produce a compressive stress at the inner edge of the flange equal to the internal pressure, this being the criterion adopted to ensure steam-tightness. Comparisons have been made between the experimentally determined stress distributions and distributions calculated by various methods. Of computer-aided methods, the English Electric Kidsgrove structural-analysis programme gave the best correspondence to the experimental results with a relatively simple idealization of the problem. When the depth of a flange exceeds the width and the bolt load acts within the inner half, the stress distribution is reliably predicted if the flange is assumed to behave as an eccentrically loaded column.
Numerical solution of axisymmetric-stress problems by point matching
Authors: Hooke C J 
Published: July 2007

In a previous paper the author described the application of the point-matching technique to the solution of plane elastic problems. It was shown that it is possible to produce a single computer programme capable of analysing a wide range of such problems. The technique is extended in this paper to the case of an axisymmetrically loaded elastic body of revolution. The details of the technique are necessarily more complicated in the present instance but it has proved possible to develop a general computer programme for this type of problem. The application of the method is illustrated for a number of problems for which approximate or experimental results are available. Good agreement between these results and the point-matched stress distribution is obtained in every case.
Use of collapsible structural elements as impact isolators, with special references to automotive applications
Authors: Postlethwaite H E , Mills B 
Published: July 2007

Part 1: Simple struts have been impacted between travelling and stationary masses and the collapse found to consist of two distinct phases. The pre-failure phase, being primarily an elastic region, has been analysed by stability criteria and the post-failure phase by consideration of the plastic collapse of the strut. Associated with the pre-failure phase is a large transient deceleration which is found, among other parameters, to be a function of the strut shape. Part 2: A series of sheet-metal structures have been impacted and, like struts, the collapse found to consist of pre- and post-failure phases of separate identities. The pre-failure phase is again associated with the shape of the structure and may give rise to a large transient deceleration. This analysis has led to the consideration of more complex elements, such as might be found in an automobile frontal structure, and finally to a complete automobile analogue. Conclusions are drawn about the structural parameters required to bring about specific deceleration characteristics in a vehicle crash.
Grey cast irons for thermal-stress applications
Authors: Bertodo R 
Published: July 2007

Pearlitic flake-graphite grey cast irons have long been widely used for the manufacture of diesel-engine combustion-chamber components. Nonetheless, very few pertinent high-temperature data are to be found in published work. The investigation described attempts to enlarge current knowledge on the high-temperature behaviour of grey cast irons in view of requirements highlighted by high thermal ratings. A general consideration of the problem showed that the often quoted Eichelberg material-quality factor is largely irrelevant and an alternative assessment formula is proposed. This is broadly confirmed by a systematic examination of the mechanical and physical properties of 166 plain and alloyed cast irons and a limited number of engine components. Different engine components impose different demands upon the material properties but for economic reasons a single cast-iron melt capable of meeting most of the requirements of all components is needed. It is shown that this situation is best met with an alloyed iron containing 1.3 per cent of copper-nickel and 0.4 per cent of molybdenum. The scatter in properties obtained from production casts was found to be typical for such irons. For components having safety factors of 2 or less, a prerequisite of economic engineering design, the service reliability is crucially dependent upon the scatter of material properties. Thus, there are advantages in reducing this scatter and it is shown that this can be achieved by attention to the cleanliness of the matrix and tight control of the chemistry of the melt. In general, the absolute values of mechanical and physical properties of flake-graphite cast irons appear to be governed mainly by the form and size of the graphite flakes and the chemistry of the matrix (i.e. CEV and alloying additions). Regression analysis of the results permitted the derivation of empirical formulae for the prediction of the iron properties. The general findings are used to suggest possible ways of improving the thermal resistance.
Stress-concentration factors in u-shaped and semi-elliptical edge notches
Authors: Baratta F I , Neal D M 
Published: July 2007

Stress-concentration factors are analytically determined for relatively deep U-shaped edge notches of constant radii in a semi-infinite sheet with uniaxial tension applied parallel to the sheet edge. Because a strong geometric similarity exists between a U-notch and a semi-elliptical notch of the same tip radius, a comparison of such analytical data is effected. Stress-concentration factors for U-notches in a semi-infinite sheet are also compared with other comparable analytical and experimental data available in the literature. Finite-width correction factors are applied to the results of the semi-infinite-sheet analysis to provide practical design data. These data are compared with experimental results provided by a number of investigators.
An experimental linear cumulative-damage law
Authors: Miller K J 
Published: July 2007

An hypothesis of cumulative damage is presented that may be expressed mathematically as Σn÷Nf = constant where n is the number of cycles performed at a constant strain range and strain rate and Nf is the number of cycles to failure at the same strain range and strain rate. An initial experimental investigation at room temperature shows that, under constant strain-rate conditions, the load-sequence effect is removed, but the value of the constant is dependent on the definition of failure. If failure is defined as complete rupture the summation term is less than unity whatever the sequence of loading. Should failure be defined as the termination of the steady-state period, that is at the point of crack growth instability, then the summation term is greater than unity. This latter definition therefore leads to a linear law of cumulative damage that gives a doubly cautious prediction of life that is of obvious advantage to engineers.
Experimental determination of adhesion and slip areas in rolling contact
Authors: Ollerton E , Pigott R 
Published: July 2007

An experimental technique has been developed to allow the rapid determination of adhesion and slip areas in steady-state rolling contact. The technique consists in rolling solid black-rubber toroids on a ground-glass plate under carefully controlled conditions. It enables the division of the contact area into slip and adhesion areas to be observed and photographed whilst rolling is taking place. A loading frame was devised to enable rolling with longitudinal shearing traction, rolling with transverse creep, and rolling with spin to be investigated either separately or in combinations. The results of the experiments have been compared with existing theories, and some conclusions as to the accuracy of the theories have been made.
Photothermoelastic analysis of thermal stresses in discs with eccentric holes
Authors: Ajovalasit A 
Published: July 2007

The paper deals with thermal stresses that arise in discs with eccentric holes, such as are employed in the rotors of multi-stage gas turbines. The stress distribution was analysed by the photothermoelastic method. CR 39 sheets were used as the material and dry ice as the refrigerant. The effect of several geometric parameters on stress distribution, especially the influence of adjacent holes, was investigated by testing 32 configurations of discs. Curves that allow the determination of the peak stresses and optimum spacing of holes are given.
Cruciform specimens for biaxial fatigue tests: An investigation using finite-element analysis and photoelastic-coating techniques
Authors: Wilson I H , White D J 
Published: July 2007

The results are presented of investigations made on four cruciform biaxial fatigue specimens, each of which had a differently designed central region. This central region consisted of a reduced section of uniform thickness t over a circular area of diameter d which was connected by a transition radius to the full thickness of the cruciform. Equal tensile and compressive forces were applied alternately along one pair of arms only and the distribution of surface strain was studied by photoelastic-coating techniques after elastic cycling and then plastic cycling. To assess the fatigue performance of the specimens further cycling was carried out until cracks developed. Under elastic conditions, strains uniform over the thickness were calculated by finite-element techniques. For conventional fatigue tests in the high-endurance range the specimen with d/t = 12.5 is recommended. For high-strain low-endurance fatigue investigations the specimen with d/t = 5 is preferred. The recommended designs are free from problems of buckling and are such that an area of uniform strain is produced at the centre of the specimen.
Computation of stresses and flexibilities for multi-mitred pipe bends under in-plane bending
Authors: Bond M P , Kitching R 
Published: July 2007

The analysis developed is a refinement and generalization of an existing theory. The extensions incorporated are necessary for the accurate theoretical prediction of stress distributions and flexibility factors for multimitred pipe bends of low pipe factor. A method of approach that renders computation of the analysis more practicable has been introduced and a programme has been developed for the production of design information. Flexibility factor and stress distributions calculated in this way have been compared with experimental results for a 30-inch-diameter, three-weld right-angled mitred bend of low pipe factor (0·0246).
Strain localization in beams under cyclic plastic straining at room and elevated temperature
Authors: Horwood G P , White D J 
Published: July 2007

Deflection-controlled tests have been conducted on beams subjected to uniform bending and two forms of non-uniform bending in which strain localization occurs. The materials tested were mild steel to B.S. 1501–161 Grade 28A at room temperature and 350°C and stainless steel En 58J at room temperature and 650°C. For materials which show a settled cyclic stress-strain relation (the cyclic semi-range of strain and the corresponding cyclic semi-range of stress) estimates may be made of life in deflection cycling for beams under strain-localization conditions if the strains are calculated from the cyclic relations and the corresponding endurances are obtained from strain-cycling tests in uniform bending. On the basis of the present and previous results, it is believed that this procedure will give predictions which are on the side of safety. In the present work the predictions were often unduly safe. For materials which strain-harden severely, an elastic analysis may sometimes be adequate for an assessment of the strains involved. However, with such an analysis the predicted endurances may be unsafe and should be reduced by a suitable factor to allow for uncertainties.
Design of cams to reduce maximum stress in a longitudinally reciprocated bar
Authors: Beddoe B 
Published: July 2007

There is a lower limit to the maximum stress in a bar that is moved longitudinally at constant velocity and reversed at one end in a finite time, the other end being free. The lowest possible value of the maximum bar stress during a single reversal is determined for the general case and equations to define cams that achieve it are established. These cams have the disadvantage of giving much higher stresses when run above or below the speed for which they were designed. Another type of cam without this disadvantage is obtained by reversing through two parabolic arcs which are selected to minimize the maximum bar stress. Proof that the selection is the best obtainable from two parabolas is derived from solutions in terms of progressive stress waves with consideration for light damping. Specification of this type of cam and measurements of the stresses in ‘traverse bars’ reciprocated by such cams on machines for winding yarn are included.
Elastic-plastic response of a sandwich cylinder subjected to internal pressure
Authors: Muensterer H F , Rimrott F P J 
Published: July 2007

The propagation of plastic zones in a thin-walled sandwich-type cylinder has been analysed theoretically. Boundary conditions are clamped-clamped at both ends, i.e. no rotation is permitted. The material was assumed to behave isotropically and to obey the yieid criterion of Huber-Hencky-von Mises. Deformation was computed on the assumption that the vector of rate of strain was normal to the plastic-interaction curve. The predicted result was verified experimentally. Four specimens were built by lamination of a hexcell core between two concentric cylinders. In the two mild-steel specimens, the initial stage of plastic flow conformed well with the prediction. This proved that plastic flow is not initiated at the mid-position between the end constraints. In two aluminium specimens, this phenomenon of incipient plastic flow could not be observed owing to the absence of a pronounced yield point. The overall agreement was, however, satisfactory.
Pressure distribution in hydrostatic extrusion dies
Authors: Kamyab S , Alexander J M 
Published: July 2007

To be able to understand the detailed mechanics of plastic flow and lubrication during hydrostatic extrusion it is very desirable to be able to measure the precise pressure distribution along the length of the die. In the present work, experiments have been developed which enable this pressure distribution to be measured indirectly with reasonable accuracy and comparison is made between the distribution obtained experimentally during slow-speed hydrostatic extrusion of annealed copper and the distribution predicted by theoretical analysis. Very good agreement was obtained for the single geometry investigated.
Experimental analysis of stresses in a buoy-cable system model using a birefringent fluid
Authors: Durelli A J , Clark J A 
Published: July 2007

An extension of the method of photoviscous analysis is presented which permits quantitative studies of strains associated with steady-state vibrations of immersed structures. Strains can be determined both in the vibrating structure and in the surrounding fluid. The method is applied in an investigation of one form of behaviour of buoy-cable systems loaded by the action of surface waves. Procedures are illustrated for evaluating directly from the strain data parameters useful to the buoy-cable system designer. The analysis performed is two-dimensional. The cable is modelled by a soft rubber strip, and the buoy by a round can floating on the surface of a birefringent fluid. A payload is simulated by a weight attached to the lower end of the strip. Waves of controllable frequency are produced by a device actuated by a shaker. Strains in the fluid and in the strip are determined from isochromatic and isoclinic data and the possible extension of the experimental results obtained to prototypes by means of scaling laws is suggested.
Strain accumulation and rupture during creep under variable uniaxial tensile loading
Authors: Marriott D L , Penny R K 
Published: July 2007

The results of uniaxial creep tests performed on a structural aluminum alloy at 180°C are presented for steady and variable loading. Continuous measurement of strain throughout the tests has enabled a meaningful comparison of commonly used creep theories for strain accumulation and ruptue to be made. For the material investigated it appears that creep strains are accurately predicated by time-hardening theory and the total-strain theory is likely to be a useful approximation for predicting component behaviour at large strains. Stress relaxation has no effect on rupture times and there is some evidence for strain as a criterion for rupture.
Collapse loads for thin cantilevers with rectangular holes along the centre-line
Authors: Ranshi A S , Johnson W , Chitkara N R 
Published: July 2007

Plane stress slip-line field solutions, which provide the modes of yielding and the corresponding yield loads, are presented for the plastic bending of end-loaded thin cantilevers of rectangular cross-section containing rectangular holes. The theoretical results obtained from these solutions are compared with some experimental results and those obtained from plane strain slip-line fields and lower bound estimates, all presented previously by the authors (1)‡. It is observed that the correlation of the experimental results was much better with the plane stress solutions than with either the plane strain or lower bound results. The effect of adjacent holes and possible lateral or local buckling on the ultimate strength of the cantilevers is also examined.
The deflection of a thin circular plate with an eccentric circular hole
Authors: Ollerton E 
Published: July 2007

A theoretical investigation of the small deflections of a thin circular plate is reported. The plate has a flat circular clamp at the outer edge and a similar clamp at the inner edge, which is placed eccentrically. These supports can be arranged to prescribe either a clamped edge or a simply supported edge, and all combinations of the two types are investigated. The plate can be subjected to a concentrated load at the centre of the inner clamp, moments about two perpendicular axes of the inner clamp, or pressure on the plate surface between the clamps. Deflections and slopes of the inner clamp have been determined, and in all cases the new values tend towards established values for the case of a central inner clamp, as the eccentricity of the inner clamp is reduced.
Quasistatic cracking of polymers with residual stresses
Authors: Chow C L , Ngan K M 
Published: July 2007

Residual stresses are often introduced during manufacturing processes of polymeric components whose structural capabilities must be adequately evaluated in design of engineering components against brittle fracture. As the applications of these materials expand, the need to understand their behavior with residual stresses becomes more necessary. This paper presents a compliance method of analysis which enables the measurement of fracture toughness of thermoplastics with residual stresses and illustrates the effect of residual stresses on quasistatic cracking of these materials. Polymethylmethacrylate was chosen as a typical material for the investigation. Theoretical analysis has shown that effective fracture toughness and residual strain energy can be readily evaluated with the compliance approach. Experiments were carried out to mechanically simulate a set of known residual stresses in polymethylmethacrylate specimens. Results measured experimentally compared well with those derived analytically.