bluuebunny/crossref_metadata_2025 huggingface dataset:
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.
Strain concentrations at the corners of stretched rubber sheets
Authors: Lindley P B
Published: July 2007

A numerical and experimental investigation has been made of the strain-concentration factors K at the corners of stretched rectangular rubber sheets having a wide range of length/width ratio, for corner curves of various shapes and sizes. It was found that K is approximately inversely proportional to the cube root of the relative size of the curve, and that elliptic corner curves are better than sine curves. Undercutting is deleterious, but corner wedges with angles of less than 45° have zero strain at the corner. K generally decreases with increasing nominal strain.
Analysis of an inclined crack centrally placed in an orthotropic rectangular plate
Authors: Gandhi K R
Published: July 2007

The problem of an inclined crack centrally placed in a generally orthotropic rectangular plate under tension is investigated. The modified mapping-collocation technique introduced by Bowie and other workers is used in the analysis and the stress-intensity factors are computed for several orientations of cracks and for rectangles of various proportions. The effects of orientation of the principal axes of orthotropy are also considered. The results indicate a fairly strong dependence of the stress field on the orientation of these principal axes of the material and the occasional complexity of the interaction of material anisotropy and the geometry of the specimen.
Performance of four plastics in relation to bolt relaxation in a non-conducting rail joint
Authors: Mitchell A S , Mills D , Kitching R
Published: July 2007

Experiments have been conducted to observe the relaxation behaviour of fishplate-bolted rail joints in which four different polymeric materials were used for electrical insulation. Static tests were conducted to study the effect of temperature and of different locking sequences for the bolts on a rig which simulated service conditions at a joint. The effect of cyclic loading was considered.
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 distribution in and around strain gauges
Authors: Stehlin P
Published: July 2007

The interaction between a strain gauge and its substratum is investigated for the special case of a one-dimensional gauge adhesively bonded to a half-plane. The influence on the strain distribution of the properties of the underlying material, of strain-gauge design, and of adhesive properties is demonstrated by numerical examples.
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.
Hole flanging and punching of circular plates with conically headed cylindrical punches
Authors: Johnson W , Chitkara N R , Ibrahim A H , Dasgupta A K
Published: July 2007

To investigate the mechanics of the hole-flanging process, the quasi-static drifting and punching of thin circular plates with conically headed cylindrical punches was carried out for different materials. The deformation modes of the defected plates and the loads associated with them at different stages of punch penetration were obtained and the results are analysed by use of an elementary theory. The neck characteristics in the flange formation, which are of basic types—lip, petal and plug—were found to be dependent on punch semi-angle, material, and size of the initial hole in the plate. The change-over from lip to petal mode and the stage at which fracture occurs were studied. A simple analysis that predicts some features of neck formation, the onset of plugging and features of fracture development is also given and results obtained by its use are compared with experimental results.
Machine for the testing of plastics under bending loads
Authors: Mucci P E R , Ogorkiewicz R M
Published: July 2007

A testing machine developed for the study of the deformational behaviour of plastics under bending loads complements high-accuracy tensile-creep testing machines and provides a more appropriate means for the testing of brittle fibre-plastics composites and plastics sandwich structures. The machine is suitable for applying constant loads and automatically recording the deflections of specimens at several points over periods of up to three months.
Large deflection of plates and beams obeying non-linear stress—strain laws
Authors: Rushton K R , Hook P M
Published: July 2007

The large deflections of rectangular plates and beams obeying a non-linear stress-strain law are examined. Solutions are obtained by use of dynamic relaxation, a numerical finite-difference technique. Comparisons are made with alternative solutions and experimental results. The effects of varying parameters in the non-linear expressions are considered.
Report on the fifth international conference on experimental stress analysis
Authors: Meyer M L
Published: July 2007

The Fifth International Conference on Experimental Stress Analysis was held on 27–31 May 1974 at Udine in Italy and was concerned with data processing in stress analysis, applications of stress analysis to materials behaviour, stress analysis in biomechanics, and advanced methods and applications of stress analysis in engineering.
A finite-element programme for the plane-strain analysis of rubber
Authors: Lindley P B
Published: July 2007

For a highly incompressible material the use of triangular elements in plane-strain finite-element analyses restricts the number of degrees of freedom. A computer programme is developed which uses quadrilateral elements, and various methods of reducing computation time are employed. A strain-energy function is proposed which will enable solutions to be obtained at strains well beyond those of linear classical elasticity theory.
Recent x-ray diffraction studies of metal fatigue in Japan
Authors: Tanaka K
Published: July 2007

This paper describes results of several recent studies, carried out in Japan, on metal-fatigue problems using X-ray diffraction techniques. The subjects covered are the effect of residual stress on fatigue strength, non-destructive detection of fatigue damage from information supplied by X-ray diffraction, and X-ray microbeam analysis of stress and strain near the tips of fatigue cracks and fracture surfaces. The usefulness of the X-ray approach to fatigue problems is emphasized and possible future developments are suggested.
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.
Acoustic emission studies of filament-wound carbon fibre reinforced rings and pressure vessels
Authors: Fuwa M , Bunsell A R , Harris B
Published: July 2007

Following earlier work on the use of acoustic emission techniques for studying fatigue and fracture in unidirectional plane samples of carbon fibre reinforced plastic, experiments have been carried out on filament-wound rings and pressure vessels. The hydraulic expansion to failure of rings of carbon/epoxy composites represents the first step away from the earlier studies of model systems to more realistic structures, and it appears that the rings behave in exactly the same way as tensile samples. Of greater significance, however, is the fact that polar-wound pressure vessels in the form of oblate spheroids with aluminium screw-thread end connexions also show the same kind of acoustic emission patterns. If a vessel is pressurized and held at constant pressure the acoustic output is gradually reduced until it ceases. If the vessel is unloaded and reloaded, the pressure at which emission recommences (about 93 per cent of the previous maximum) can then be considered to be a safe working pressure. The response of these vessels to monotonic loading, cyclic loading and stress relaxation is very similar to that of unidirectional tensile samples.
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.
Quadratic isoparametric circular plate element with strain smoothing
Authors: Mawenya A S
Published: July 2007

A number of plate bending elements which include shear suffer from spurious shear effects. So far, however, the techniques that have been used to eliminate these effects involve only the manipulation of the stiffness matrix, and are incapable of accurately predicting the distribution of the shear stress resultants within the element. Herewith, a least squares linear smoothing is applied to the strain matrix of a quadratic, isoparametric symmetrical circular plate element before assembling the stiffness matrix; thereby leading to a better prediction of the stress field within the element.
Fatigue crack propagation in biaxial stress fields
Authors: Hopper C D , Miller K J
Published: July 2007

The propagation of fatigue cracks in notched and un-notched biaxially stressed plates is investigated. The rate of propagation is found to be affected by both the stress field associated with the notch and the biaxial stress state of the bulk material. It is found that the propagation rate of a crack from a notch may be predicted by the use of a theoretical notch contribution factor in conjunction with propagation data for a crack in un-notched material.
X-Ray stress measurement on steels having preferred-orientation
Authors: Dölle H , Hauk V , Kockelmann H , Sesemann H
Published: July 2007

A non-linear distribution of (211) interplanar spacing is shown to occur in textured steels, the reasons for the non-linearity being marked texture, cold-formed structure and stresses. For stress evaluation it is recommended that the directions ψ be used, which are independent of texture. The paper gives the modified sin2ψ method, for both film and goniometer techniques, for predominantly uniaxial stresses.
A study of the behaviour of square plates at large deflections according to the theories of Foeppl and Von Karman
Authors: Turvey G J
Published: July 2007

Dynamic relaxation is used to analyse square plates at large deflections according to the Foeppl and Von Karman theories. The results quantify their asymptotic nature and the effect of variable thickness.
Pad-reinforced cylindrical shell loaded radially through a plate bracket attachment
Authors: Hughes J F , Kitching R
Published: July 2007

The constructional detail of a bracket attached to a pad-reinforced cylindrical vessel and subjected to a radial load is studied experimentally. An approximate analysis which is based on experimental observations of the load distribution in the bracket is developed. It allows a complete stress analysis of the reinforcing pad and vessel. Stress distributions determined using this analysis show general agreement with experimental stress distributions. Stress calculations based on the BS1515 method of assessment result in values greater than the measured stresses.
Elasto-plastic and creep behaviour of axially loaded, shouldered tubes
Authors: Dawson R J , Fessler H , Hyde T H , Webster J J
Published: July 2007

This paper compares the finite element predictions of elasto-plastic and creep behaviour with experimental data for axially loaded, shouldered tube models.

Four shouldered tube models were made of a lead alloy and tested at 61°C, using strain gauges to measure the elasto-plastic and creep strains in the plain tube and fillet regions of the models. Instantaneous stress-strain and creep data were obtained from strain-gauged, uniaxial tensile specimens.

The finite element solutions are based on the incremental Prandtl-Reuss equations. The elasto-plastic iterative solutions use a ‘negative gradient’ from the calculated point to the equivalent stress-equivalent strain curve to get the next estimate of the plastic strain increment. A time incremental method is used to obtain the creep solutions.

Tests with the mean tube stress below, at and above the yield stress showed very good agreement between prediction and measurement of initial strains in the fillets. Differences between predictions and measurements of creep strains are attributable to cast-to-cast variations.
Model road-tank metal vessels subject to internal explosion or static penetration
Authors: Johnson W , Reddy T Yella , Reid S R
Published: July 2007

Thin-walled tubes, having hemi-spherical ends and four symmetrically placed stiffening rings to model a typical road transport tank container, were subjected to a mechanical loading from either: (i) an axial line or point charge of explosive, or (ii) static penetration from the outside by a punch to determine their plastic deformation characteristics.

The vessels were examined when: (a) nominally empty, (b) air pressurized, and (c) almost completely full of water.

Results for a range of tests in which the vessels were not stiffened are also reported and this facilitates useful comparison between the stiffened and unstiffened cases.
A thermo-plastic shear instability criterion applied to surface cracking in upsetting and related processes
Authors: Jenner A , Bai Y , Dodd B
Published: July 2007

The workability of wire and rod in upsetting and related processes is dependent on the ductility exhibited by the expanding free surface. From previous measurements of the equatorial strain histories during incremental upsetting of cylinders, linear fracture conditions for a large number of materials of engineering importance have been derived.

A simple theoretical explanation of the experimentally observed fracture condition is given. This is done using the concept of a thermo-plastic shear instability criterion. It is shown that one mode of shear instability coincides with the observed straight-line fracture condition.
Mounting deformations of hydraulically expanded taper-sleeve couplings
Authors: Fessler H , Stewart R W
Published: July 2007

The ‘frozen deformation’ method has been used to determine the deformations of the hub, taper-sleeve, and shaft of a flanged coupling as used in marine gear boxes.

Hydraulic mounting caused gaps between hub and sleeve over most of the length of the hub. Contact occurred at the ends of the hub only. with the sleeve in tension or in compression during mounting. The presence of a flange at either end of the coupling did not change the above significantly.
Fracture of aluminum-epoxy layered composites containing cracks
Authors: Gdoutos E E
Published: July 2007

The plane problem of a composite plate consisting of two aluminum half-planes bonded together through an epoxy layer and containing two parallel cracks, one in the layer and the other in one of the half-planes was considered. The composite plate was loaded by a uniform uniaxial compressive stress distribution applied along the surfaces of the crack of either the layer or the half-plane. The critical value of the applied stress as well as the corresponding angle for crack extension were determined by using the minimum strain energy density theory. Valuable results governing the dependence of the critical failure stress of the composite plate as well as the angle of crack extension from the more vulnerable crack on the geometry of the plate were derived.
Araldite models for the study of elastic stability of plates
Authors: Narayanan R , Chow F Y
Published: July 2007

The suitability of Araldite as a model material for the study of plate instability problems is investigated. Model tests on stiffened plates made of Araldite and steel sheeting are reported and the test results are compared with theoretical predictions.

The overwhelming advantage in testing Araldite models is due to the large range of material elasticity (extending up to 36 000 microstrain compared with 1200–1600 microstrain for steel). Models made of Araldite are shown to be useful in simulating buckling modes and in obtaining magnified values of the likely plate and stiffener deformations in the serviceability and ultimate limit states. The ultimate capacity predicted from models is, however, significantly lower than the values of the corresponding steel prototypes on account of the early loss of stiffness of the members caused by the large deformations.
Influence of constraint on creep stress distribution in notched bars
Authors: Wu D , Christian E M , Ellison E G
Published: July 2007

Stresses and strains occuring during creep were determined for circumferentially notched round bars having several specimen notch geometries representing different degrees of constraint. The specimen geometries and the material data used in the calculations were those pertaining to a parallel experimental investigation. It was found that, for the wide notch specimens, the notch to net-section radius ratio has a greater influence on the degree of constraint than the notch depth ratio. For the thin slit specimen, the small slit tip radius to net section radius ratio caused a big difference in stress distribution from that for the wide notch specimen of the same net-to-gross radius ratio. Global and local events were distinguished by the change of notch sharpness: for the relatively wide notch, creep was mainly a global process, whereas for the sharp slit, the creep process remained in a very local region near the slit tip. Various indicators for the degree of constraint are discussed, of which the triaxiality factor I1/σ seemed to be the most useful.
A linear programming upper bound approach to the shakedown limit of thin shells subjected to variable thermal loading
Authors: Karadeniz S , Ponter A R S
Published: July 2007

This paper describes an upper bound technique for the evaluation of the shakedown limit of thin cyclindrical shells subject to thermal loading. The method is based upon the upper bound kinematic shakedown theorem of Koiter. By suitable choice of displacement field, in a finite element form, and yield surface, the problem is reduced to a linear programming problem. A number of solutions are presented involving a tube subjected to a moving temperature front which indicates that the technique provides, in an efficient way, a complete description of the load levels at which ratchetting would occur and the corresponding modes of deformation. The technique seems therefore, to provide a useful intermediary between the use of the simple rules incorporated in design codes and full inelastic analysis.
An analysis of die filling in a forging operation
Authors: Monaghan J M , Torrance A A
Published: July 2007

The nature and type of flow which occurs when metal is deformed within a closed die has a direct bearing on the loads required to form the metal and the resulting stresses within both workpiece and die. In this paper an analysis of the metal flow which occurs during a non-steady plane-strain closed-die forging operation is investigated with the aid of a version of the well established visioplasticity method. The strain components resulting from an analysis of a deformed grid pattern are used to indicate directions of maximum shear strain. These maximum shear strain directions are then used to suggest possible slip-line fields at various stages of deformation. The results clearly indicate the nature and extent of the metal flow during the final stages of the closed die forging operation. The values of forging pressure based on the computer aided slip-line field analysis is shown to be in good agreement with the experimental results. The use of a micro computer in conjuction with established stress analsysis techniques, such as the visioplasticity method and slip-line field analysis, is shown to provide additional flexibility and accuracy in the use of these techniques.
An approximate numerical method for circular membranes under lateral pressure
Authors: Gamby D , Lampi L H
Published: July 2007

The deformation of a circular membrane during a bulge test is considered as resulting from the superposition of a main, large displacement field, having a simple analytical form, on one hand, and of an additional, small displacement field, on the other. The numerical problem pertaining to the determination of the additional displacements is posed and solved. Reasonably accurate results are obtained with a restricted amount of computation.
An assessment of simple material behaviour models for predicting the mechanical ratchetting of a stepped beam
Authors: Hardy S J , Webster J J , Hyde T H
Published: July 2007

Finite element programs are often used, without experimental verification, to predict the elastic-plastic behaviour of components, but most programs only contain simple material behaviour models. In this paper, the results from three lead alloy stepped beam components, subjected to steady axial load and cyclic bending, are compared with predictions based on elastic-perfectly plastic, isotropic hardening, and kinematic hardening material behaviour models. These comparsions show that under severe load conditions, in which cyclic plasticity occurs, none of these simple models provides good predictions for the ratchetting behaviour of the beams. This is because the models do not accurately describe the cyclic elastic-plastic behaviour of the lead alloy which is similar to that of many engineering materials. It is concluded that the simple elastic-plastic material behaviour models included in most finite element packages will have to be extended to include more accurate models of material cyclic behaviour if they are to provide accurate predictions for component behaviour.
Stresses in axisymmetric rotating bodies determined by the boundary integral equation method
Authors: Abdul-Mihsein M J , Bakr A A , Parker A P
Published: July 2007

An alternative approach to arrive at the fundamental solution of the boundary integral equation (BIE) for axisymmetric elastostatic problems with rotational body force is presented. The formulation is implemented in an elastostatic BIE axisymmetric program using isoparametric quadratic elements.

The method is applied to rotating disks of constant or variable thickness and linearly tapered. The results compare very well with avaialable analytical and numerical solutions.
Radial flexibility factors of nozzles in pressure vessel heads
Authors: Chao Y J , Sutton M A
Published: July 2007

An analytical study is performed to investigate the flexibility of nozzless in pressure vessel heads. Classical thin shell theory is employed. Radial flexibility factors for nozzles in hemispherical and ellipsoidal pressure vessel heads are presented as graphs of non-dimensional shell parameters.
Experimental investigation of creep crack growth in a lead alloy
Authors: Hyde T H , Kubba B , Low K C , Webster J J
Published: July 2007

The results of 27 creep crack growth tests performed on four different specimen types (CT, 3PB, ECP, and CCP) are reported. A lead alloy, previously used as a creep ‘model material’ was used. Of the parameters commonly used to correlate creep crack growth data, the C∗ parameter was found to be the best for the lead alloy data. It is concluded that the lead alloy may be useful for ‘modelling’ the creep crack growth rates in components made of other materials with similar creep ductilities.
Biaxial strength of paperboard predicted by hill-type theories
Authors: Rowlands R E , Gunderson D E , Suhling J C , Johnson M W
Published: July 2007

Paperboard strength under biaxial normal plus shear stresses is predicted using Hill-type criteria (including Tsai-Hill, Norris, Fischer, and Ashkenazi). Results are compared throughout all four quadrants with experimental data obtained from on- and off-axis uniaxial coupons, cylinders, and cruciform specimens. The Norris and Fischer theories predict observation quite well except at higher values of shear stress where they become too conservative. The Tsai-Hill theory is conservative throughout. Simplicity of both analysis and implementation, plus need for only minimal experimental input data, are signficant advantages of Hill-type criteria. Moreover, their reliability for paper is comparable to that of other published results. Other strength theories will be addressed in subsequent papers.
An assessment of local radial loads on cylinders based on the Sanders linear shell equations
Authors: Timmins W , Little W , Findlay G E
Published: July 2007

In a recent paper, two of the present authors showed that the maximum stresses measured in a cylindrical shell subjected to a radially applied local load were higher than BS 5500, Appendix G could predict.

In order to investigate this apparent discrepancy, an analysis of a cylindrical shell under non-axisymmetric radial loading was carried out using Sanders linear shell equations, which are generally acknowledged as being the most exact available.

It is shown, however, that the results from this analysis do not provide better agreement with experiment than those earlier analyses on which design codes are now currently based.
The prediction of stress rupture life of notched specimens in the beta-processed titanium alloy Ti5331s
Authors: Webster P S , Pickard A C
Published: July 2007

Methods of predicting notched bar stress rupture behaviour are reviewed. Two very different types of notched specimens are analysed using the finite element method; one being a circumferentially V-notched test piece, the other having two semi-circular notches in a plane section.

A prediction based on the Von Mises equivalent stress distribution is proposed. Predictions using this method are compared with notched specimen test results in a commercially available titanium alloy, Ti5331s, tested at 600°C. The correlation is good for the semi-circular notched specimen and for the V-notched specimen at low stress, long life and can be improved at high stresses by making allowance for time independent plasticity and for the initial high rate of creep strain accumulation at the notch root.
Experimentally determined transient and residual stresses in a butt-welded pipe
Authors: Jonsson M , Josefson B L
Published: July 2007

Single pass butt-welding of a pipe is studied. Low heat input has been used to obtain high cooling rate with adherent martensite in the final phase transformation in the heat affected zone. Strains and stresses have been measured during and after welding on the pipe outer surface. Deviations from rotationally symmetric strain and stress fields in the pipe are studied. Two different analytical solutions for the residual stress field from the literature are discussed. The experimentally obtained residual stresses are compared with those analytical solutions. Qualitatively good agreement between experiments and analytical solutions was obtained, although the analytical solutions do not consider effects of phase transformations.
Stress analysis of short weld toe cracks
Authors: Pang H L J
Published: July 2007

Finite element analysis of weld toe cracks was used to determine the J integral and hence stress intensity factors based on elastic and elastic-plastic conditions. For a given fillet notch geometry, the results showed that the elastic solution overestimated stress intensity factors for short weld toe cracks, below 0.5 mm deep, under applied stresses which were around half the magnitude of the yield stress.
Theoretical and experimental re-examination of a crack perpendicular to and terminating at the bimaterial interface
Authors: Wang W C , Chen J T
Published: July 2007

The plane problem of a crack that terminates perpendicularly to a bimaterial interface was re-examined both theoretically and experimentally. Using the complex variable method, the crack trip stress singularities and stress distributions were generalized. Digital photelastic technique was successfully employed to confirm the generalization of the theoretical analysis. The results showed that the so-called far-field effects indeed played a significant role in the stress distribution and determination of the stress intensity factor.
The evaluation of stress intensity factors for plane cracks in residual stress fields
Authors: Wilks M D B , Nowell D , Hills D A
Published: July 2007

A reliable, efficient method is described for modelling plane cracks in arbitary residual stress fields, using the technique of distributed dislocations. This allows correctly for re-distribution of residual stresses as the crack grows. Problems where crack closure occur are discussed, and implications for solution by finite element procedures are inferred and confirmed by comparison.
On the bursting mechanism in rotating rings
Authors: Bandera C , Nicolich M , Strozzi A
Published: July 2007

The bursting mechanism in roatating, bored discs is theoretically reviewed in the light of published experimental information. In particlar, the segmentation sequence in bursting wheels is analysed according to a curved bar modelling and to a quasi-static loading, where a dynamic correction factor is introduced which reconciles theory with experiments. Finally, a diagram reporting the number of wheel fragmented pieces in terms of the ratio of ring inner to outer radii is presented, based upon available experimental data and theoretical interpretation.
Thermal stress analysis of the parting plane flange joint of an industrial steam turbine
Authors: Alwar R S , Srinivasarao S
Published: July 2007

A typical 14 MW steam turbine casing is analysed using a range of flange parameters and heating conditions with three-dimensional and two-dimensional models, in order to find the contact pressures and thermal stresses during transient thermal operations. Thermal stresses are also calculated with simple analytical formulae which are available in literature. Two-dimensional and analytical results are compared with three-dimensional results, and some correction factors are suggested. These correction factors can be used in day to day design work to obtain quick and simple solutions. Contact behaviour of the parting plane flange under transient thermal loads is studied using ‘gap’ elements available in the application software ‘NISA’.
Elastic-plastic finite element analysis of hollow tubes with axially loaded axisymmetric internal projections
Authors: Hardy S J , Gowhari-Anaraki A R
Published: July 2007

The finite element method is used to study the monotonic and cyclic elastic-plastic stress and strain characteristics of hollow tubes with axisymmetric internal projections subjected to monotonic and repeated axial loading. Two geometries having low and high elastic stress concentration factors are considered in this investigation, and the results are complementary to previously published data. For cyclic loading, three simple material behaviour models, e.g., elastic-perfectly-plastic, isotropic hardening, and kinematic hardening are assumed. All results have been normalized with respect to material properties so that they can be applied to all geometrically similar components from other materials which may be represented by the same material models. Finally, normalized maximum monotonic strain and steady state strain range, predicted in the present investigation and from previously published data, are plotted as a function of the nominal load for different material hardening assumptions and different elastic stress concentration factors. These plots can be used in the low cycle fatigue design of such geometrically similar components.
Stress and strain range predictions for axisymmetric and two-dimensional components with stress concentrations and comparisons with notch stress-strain conversion rule estimates
Authors: Hardy S J , Gowhari-Anaraki A R
Published: July 2007

A comparison is made between finite element predictions of strain and strain range for hollow tubes with axially loaded axisymmetric internal projections and values obtained from the simple notch stress-strain conversin (NSSC) rules. Data from other published analyses, where notch strains were predicted, support this investigation. The comparison is made for a variety of monotonic and cyclic loads, material hardenning assumptions, and geometries. An intermediate rule ( m = 0.5) which appears to correlate with the finite element predictions to a reasonable degree of accuracy, is identified. In addition, an analytical relationship is suggested for calculating strain and strain range, in terms of load level, strain hardening assumption, and elastic stress concentration factor (SCF) for this type of axisymmetric component. Also, a comparison is made between some previously published experimental and numerical data, obtained for other two-dimensional and axisymmetric problems, and NSSC rule estimates in order to confirm the suitability of the intermediate rule. Finally, on the basis of these comparisons, an approximate procedure for predicting stress and strain ranges under conditions of gross yielding is presented for plane stress, plane strain, and axisymmetric problems.
An assessment of a model method for predicting the fracture of cracked components
Authors: Hyde T H , Yaghi A
Published: July 2007

Three-point-bend (3PB) specimens with real cracks and very sharp notches have been manufactured from Araldite CT200 with HT907 hardener. The plane strain fracture toughness, KIC, has been obtained from cracked specimen tests and the apparent plane strain fracture toughness, KAppIC, has been obtained for various very sharp notched widths. A systematic variation of apparent fracture toughness with notch width has been observed.

Burst tests have also been performed on cylinders with similar, very sharp, axially aligned, external, semi-circular notches. It has been shown that the burst pressure for the cylinders, with different depths of crack, can be predicted from the corresponding 3PB apparent fracture toughness data. The notches in the cylinders and 3PB specimens must be very sharp, and manufactured in a similar way, for the predictions to be accurate. Therefore, by loading model components containing very sharp crack-like flaws to obtain the failure loads, the failure loads of similar actual components having a real crack and behaving in a brittle manner can be predicted.
Automated photoelasticity in white light: Influence of quarter-wave plates
Authors: Ajovalasit A , Barone S , Petrucci G
Published: July 2007

This paper deals with the influence of optical retarders on the isochromatic fringes obtained by automated white light photoelasticity using methods such as those based on spectral content analysis (SCA) and on primary colour (red, green and blue) analysis. In the following the light intensity equations of dark- and light-field polariscopes with both crossed and parallel optical retarders are reviewed. In particular, it is shown that the retardance error of the quarter-wave plates produces an attenuation of the maximum intensity in dark field and an increase of minimum intensity in light field. Experimental evidence of the influence of optical retarders is also shown.
Variational analysis for the steady state flexural behaviour of rotating orthotropic sandwich beams
Authors: Ko C L
Published: July 2007

Governing equations for predicting the steady state flexural behaviour of rotating sandwich cantilever beams with two orthotropic facings and an isotropic inner core are formulated by using the variational principle. Those for describing the steady state deformation and displacements of an orthotropic beam are also formulated by using the same method. The effect of the curing temperature of the orthotropic material upon steady state stress distributions is also included in this analysis. Exact solutions of these differential equations are obtained to calculate displacements and stress distributions in both symmetric and non-symmetric sandwich beams subjected to uniformly distributed loads. Steady state stress values for an orthotropic beam loaded with a flatwise tip force are calculated so that they can be compared to dynamic measurements for the type of beam reported in the literature. The present analysis also predicts both the lateral and the transverse inertio-elastic instabilities due to the rotational action of the beam.
Simple creep relation for a polymer that includes the effect of back stress
Authors: Nishitani T , Tsuji M , Suetsugu M , Ogura H
Published: July 2007

The subsequent creep behaviour of polymers is influenced by prior plastic deformation. The constitutive creep equation is deduced by introducing the concept of a back stress. The creep relation obtained with back stress is compared with the experimental results for the subsequent creep after prior plastic tension. This creep relation gives good agreement with the experimental results for the small creep strain.
Theoretical and experimental analysis of an arbitrarily inclined semi-infinite crack terminated at the bimaterial interface
Authors: Chen J-T , Wang W-C
Published: July 2007

In this paper, the effect of the variations of material combinations on the fracture behaviour of an arbitrarily inclined crack terminated at a bimaterial interface was investigated. By using the complex variable method, a comprehensive analysis of the state of stress and stress intensity factors (SIFs) was performed. The digital photoelastic technique was also employed to verify the analytical results. To ensure the accuracy in the process of determining SIFs, a visual check between experimentally obtained images and theoretically reconstructed images was performed. It was concluded that far-field effects usually found in the homogeneous case had to be included in the stress equations.
Relative movements within wire ropes bent over sheaves
Authors: Nabijou S , Hobbs R E
Published: July 2007

The relative movements between the centre-lines of the strands of a wire rope during bending are analysed, as are the movements between the individual wires forming those strands. The formulae are applied to an example, and used to identify the position of greatest relative movement (slip). This position coincides with the most common location of wire failures in bend-over-sheave fatigue testing, suggesting that such slip calculations may form a valuable input to wire rope fatigue predictions.
Analysis of stress concentration factors for stepped plates based on a crack tip stress intensity approach
Authors: Gray T G F , Tournery F , Spence J
Published: July 2007

The analytical equations given for stress concentration factors are based on the results of finite element analysis of stepped plates subject to uniaxial tension loading. The fillet radii at the stepped transitions were varied over a wide range, leading to elastic stress concentration factors between 1.1 and 8.3 (net stress basis).

The parametric equations depend on the previously described concept of a ‘notch configuration factor’. This is similar to the crack configuration factor or compliance function used to modify the basic crack tip stress intensity solutions in the case of finite width or other problems.

In the present case of the stepped plate, an energy approach was used to relate the sharp corner stress field to the corresponding sharp crack field, leading to a ‘sharp corner configuration factor’. This factor was then applied to the equation for the stress concentration factor at an elliptical hole in an infinite plate, to give a simple analytical expression for the stepped plate with a radiused fillet. The basic expression was refined further to improve the quality of fit, to an accuracy of 2 per cent with respect to the finite element models.
Saint-Venant's principle and the anti-plane elastic wedge
Authors: Stephen N G , Wang P J
Published: July 2007

The stress field due to self-equilibrating loading on the inner or outer radius of a wedge sector, consistent with anti-plane deformation, will be affected by two agencies: a geometric effect of increasing or decreasing area and decay as anticipated by Saint-Venant's principle. When the load is applied to the inner radius the two effects are acting in concert; however, when the load is applied to the outer radius the two effects act in opposition. For a wedge angle in excess of the half-space the geometric effect is dominant over Saint-Venant decay and the stress increases the greater the distance from the loaded outer radius, indicating a breakdown in Saint-Venant's principle. For the wedge angle 2α = 360°, the unique inverse square root stress singularity at the crack tip, which is at the heart of linear elastic fracture mechanics, can be attributed to this breakdown of Saint-Venant's principle for just one eigenmode.
Three-dimensional coupled thermal stresses in infinite plate subjected to a moving heat source
Authors: Tsuji M , Nishitani T , Shimizu M
Published: July 2007

In this paper, the three-dimensional problem concerning the transient thermal stress is theoretically analysed by considering the thermomechanical coupling effect by means of the Laplace transformation and the generalized Fourier transformation. Numerical evaluation is carried out for the temperature distribution and the thermal stresses in an infinite plate heated by a local heat source that moves with constant velocity on the surface.
Gastrointestinal pH measurement in rats: influence of the microbial flora, diet and fasting
Authors: Ward F. W. , Coates M. E.
Published: July 2007

The pH of the rat intestinal tract was decreased by the presence of a microbial flora, but its influence in the forestomach is less clear. Stomach pH values varied according to the amount of food present at the time of measurement. Fasting increased the pH of the gastrointestinal tract in conventional rats but had little effect in germfree rats. In the conventional rat, feeding a purified diet compared with a commercial diet resulted in a lower pH in the forestomach and a higher pH in the caecal contents. Magnesium trisilicate promoted gastric emptying in conventional rats and its antacid effect was observed only in the caecum and colon.