bluuebunny/crossref_metadata_2025 huggingface dataset:
An experimental study of the stresses in a shell of revolution with geometrical imperfections and cracks
Authors: Godoy L A , Croll J G A , Kemp K O , Jackson J F
Published: July 2007

Interest in the effects of geometrical imperfections and cracks on the stresses in reinforced concrete shells has been stimulated by the failure of the Ardeer cooling tower. Due to the extreme difficulties of testing doubly curved, reinforced concrete shell models, a programme of experiments on an axially loaded aluminium cylinder containing controlled axisymmetric geometric imperfections has been carried out to show the nature of the stress distributions that occur when meridional cracking passes across the imperfection. Results over a wide range of crack configurations, for which the discrete cracks have both partial and complete loss of stiffness in the circumferential direction, are found to be in close agreement with predictions from an appropriate finite element numerical modelling.

It is shown how the concentration of membrane hoop stresses associated with the imperfections are redistributed to cause substantial changes in meridional bending and membrane stresses only when a complete loss of stiffness occurs at the cracks. With the thin reinforced concrete shells used in cooling towers having only limited flexural capacity, the combination of geometric imperfections and cracks could, as a consequence, readily lead to failure once yield or fracture of the hoop reinforcement occurs.
Effective widths in prestressed single t-beams
Authors: Adekola A O
Published: July 2007

This paper is concerned with the determination of effective widths of the flanges of prestressed single T-beams. There does not appear to exist any authoritative opinion on the effect of prestressing on shear lag when dealing with a monolithically constructed T-beam. Existing results can probably deal with the case when an already prestressed rib interacts with a concrete slab through embedded dowels connecting the two. Results show that effective width values for the prestressed T-section under live load are slightly different from those for the unprestressed section. It is thought that the differences are such that a single table of effective widths could still be applied in both cases. Detailed results are presented. These results have been calculated for a uniformly distributed load and for point loading.
Tensile stress/strain characterization of non-linear materials
Authors: Margetson J
Published: July 2007

A uniaxial stress/strain curve is represented empirically by a modified Ramberg-Osgood equation ∊=(σ/E) + (σ/σo)m. Firstly E is extracted then σo and m are determined from two points on the experimental curve. These values are improved iteratively by a least squares fit using all the experimental points on the curve. The procedure is used to generate stress/strain relationships for a variety of materials and there is good agreement with the experimental values. The method is also applied to a simulated aerodynamic heating experiment.
Approximate calculations on the large plastic deformation of helical springs and their possible application in a vehicle arresting system
Authors: Johnson W , Yu T X
Published: July 2007

The quasi-static large, plastic deformation of a helical extension spring is analysed to determine its load-deflection characteristic and energy-absorbing capacity. These results along with elastic effects and other related factors are then discussed in relation to a vehicle arresting system. Formulae and diagrams for facilitating the design of such systems are given. Some experimental test results for the large plastic extension of some initially close coiled helical springs are presented and compared with the theoretical results.
Optimization of inner and outer boundaries of beams and plates with holes
Authors: Durelli A J , Rajaiah K
Published: July 2007

This paper presents optimized shapes of inner and outer boundaries for three specific problems: a long rectangular plate with a central hole subjected to uniaxial tension, a simply-supported slotted beam subjected to a load uniformly distributed over a small area at the centre, and a square plate with a central hole under uniaxial uniform pressure. The two-dimensional photoelastic method is used for optimization. The results indicate a significant reduction in stress concentration factor or in weight, or in both. The examples presented also include cases where the inner and outer boundary stresses are mutually dependent.
A simplified approach to calculating stresses due to radial loads and moments applied to branches in cylindrical pressure vessels (calculations to BS 5500, Appendix G)
Authors: Teixeira M A , McLeish R D , Gill S S
Published: July 2007

Simplified charts are presented for elastic stress concentration factors due to radial loads and circumferential and longitudinal moments applied to circular branches normal to cylindrical pressure vessels. The charts are based on the procedures given in Appendix G of BS 5500.

The assumptions implied in Appendix G and the limitations on the geometrical parameters ro/r and r/t are discussed. A modification to Appendix G is suggested which is slightly more restrictive than at present. Published results for stresses due to local loads on branches in cylindrical vessels are compared with the values given by the charts.
A review of stress-strain paths and constitutive relations in the plastic range
Authors: Rees D W A
Published: July 2007

Plastic strain paths produced by both radial and non-radial stress paths are reviewed for metals and alloys under uniaxial and biaxial stress. The present interpretation illustrates collective trends and offers theoretical solutions for each of several stress paths. In general the strain path is linear for a radial stress path for most materials at low to medium temperatures. The isotropic quadratic hardening rule of von Mises rarely describes the strain behaviour accurately. but a simple anisotropic quadratic form provides good agreement by the uniform hardening rule. Exceptions are found for magnesium and an associated alloy at room temperature and for the high temperature deformation in an aluminium alloy. Descriptive yield functions are presented and the anistropic constants determined for one particular function of the Bailey form.

Strain paths produced by outward non radial zig-zag and stepped stress paths are approximately linear provided that they are confined to a narrow band in stress space. It is shown that an equivalent radial stress path analysis provides good agreement with experiment. The strain paths resulting from stress paths containing corners and from paths composed of partial or complete unloading followed by reloading in a different direction are non-linear. The behaviour is attributed to strain history; namely, a Bauschinger effect where unloading occurs and an interaction between direction dependent plastic strains for stress paths containing corners. For unloading-reloading paths a rotation in the strain path towards a linear direction is indicative of the transient nature of strain history. Good agreement is found with the prediction from each of three rules of anisotropic hardening. They are thus generalized to provide the plastic strain response to any stress path that is composed of linear segments. Modifications that account for the effects of non-linear work hardening and creep are discussed.
An experimental study of the ultimate load behaviour of small-scale steel box girder models with web openings
Authors: Evans H R , Shanmugam N E
Published: July 2007

An experimental study of the ultimate load behaviour of small-scale steel box girder models is described. The models were subjected either to predominant shear or pure bending loads and, in the latter case, openings were introduced into the webs of two of the models. The effects of these openings are shown to be small. Simple theories are applied and are shown to give reasonably accurate predictions of the failure loads.
Exact solutions to some honeycomb sandwich beam, plate, and shell problems
Authors: Holt P J , Webber J P H
Published: July 2007

A consistent set of equations is given for honeycomb sandwich shells, wherein each layer of the sandwich is treated separately. The theory allows for the effects of thick cores, non-constant core thickness and arbitrary anisotropic faces. Analytical solutions are obtained for constant thickness and tapered beams, a flat plate, and a circular cylinder subjected to simple loading conditions. The principal use of such solutions is in the testing of finite elements which are intended to model honeycomb sandwich construction.
A rig for creep and thermal ratchet testing of lead alloy models
Authors: Hyde T H , Fessler H , Webster J J
Published: July 2007

The development and calibration of a rig and an axisymmetric lead alloy component for isothermal creep, non-isothermal creep, and thermal ratchetting testing is described.

Steady and variable, axial mechanical loads are applied by a dead weight and lever system. Thermal loads are applied by controlled variations of the temperature of water flowing through the bore and along the outside of the component. Strains and temperature are measured with electrical resistance strain gauges and thermocouples, respectively.
Stress concentrations on axially loaded, unsymmetrical projections on flat bars
Authors: Fessler H , Woods P J
Published: July 2007

The effects of shape and position of load application on the magnitude and position of the peak stresses in stepped bars and around T-slots are determined from photoelastic models. Stress concentration factors for any practical shape can be quickly determined from the results. Stress concentration factors at these unsymmetrical projections are related to previously published factors for symmetrical projections. Optimum proportions which give the lowest peak stresses for different specified dimensions are also presented.
End reinforcement and grips for anisotropic tubes
Authors: Highton J , Soden P D W
Published: July 2007

A method of gripping and reinforcing the ends of anisotropic tubes for testing under combined axial load and internal pressure is analysed.

Edge solutions for long, cylindrical, specially orthotropic shells are considered.

The tube, reinforcement, and grips are then modelled as an assembly of short, parallel, multilayered, thin-walled, orthotropic shells.

Theoretical results are presented for the stress distribution in a ± 75 degree filament-wound E glass/epoxy resin tube with circumferentially wound glass fibre reinforced ends.
A rig for controlled cyclic strain and temperature testing
Authors: Beauchamp D J , Ellison E G
Published: July 2007

A servo-hydraulic test rig capable of applying combined temperature and strain or load cycles has been developed and commissioned. The nature of the test has dictated the specimen form as a hollow, hour-glass type.

The critical problem of a suitable extensometer for temperature and strain cycling has been solved. The device designed and produced shows negligible transient temperature effects, has a high resolution of better than 0.1 μm, and is mechanically very stable.

The heating and cooling is controlled by an induction heating system with grip cooling; additional cooling is available using compressed air passing through the hollow specimen. The system is capable of following a temperature ramp to within 1°C linearity. The thermal strain associated with a temperature cycle is compensated for using a microprocessor system specially developed for the purpose, which also enables a mechanical strain-stress loop to be plotted during a test.

Both ‘in-phase’ and ‘out-of-phase’ temperature/strain cycles have been carried out and development continues to include dwell periods.
Determination of the flexural stiffness of thin plates from small deflection measurements using optical holography
Authors: Marchant M J , Snell M B
Published: July 2007

A technique is presented for accurate determination of the flexural stiffness of thin plates using optical holography. Measurements of the interference fringes on thin rhombic plates in anticlastic bending are used to calculate the components of curvature by a simple numerical method Control experiments on a metal plate give good agreement with the results of small deflection bending theory. The method appears ideally suited to the measurement of anisotropic flexural stiffness properties.
The stresses induced in reinforced plastic matrix pipes by saddle supports
Authors: Greatorex C B , Tooth A S
Published: July 2007

The results of a series of experiments conducted on reinforced plastic matrix pipes show how the peak stresses, occurring in the saddle support region, can be reduced in magnitude by certain design features. Two methods are found of value: (1) to use a flexible medium, such as PVC or rubber, between the saddle and pipe, and (2) to support the pipe on a saddle with a radius greater than the pipe radius. The experimental results are compared with an analytical approach using shell theory making the assumption that the pipe material is isotropic. The agreement between the experimental and analytical results is promising.
An analysis for cylindrical vessels under local loading-application to saddle supported vessel problems
Authors: Duthie G , White G C , Tooth A S
Published: July 2007

An analysis is presented for unstiffened circular cylindrical vessels subjected to non-rotationally symmetric and/or local loading. The analysis has been employed to develop a rigorous solution for saddle supported vessels mounted on saddles which are either loose or welded to the vessel. An illustrative example is included to demonstrate the validity and application of the analysis and typical results presented for the saddle supported vessels problem. The document extends previous work (1)† to take full account of saddle flexibility and is published in parallel with a second paper (2) which compares theory with experiment.
A three-dimensional photoelastic study of the stresses in horizontal, saddle-supported, liquid-filled storage vessels
Authors: Stanley P , Mabelson A R
Published: July 2007

A series of three-dimensional photoelastic models (thickness to diameter ratio 0.009–0.016) have been tested and analysed with the objective of providing detailed experimental stress distributions for examples of this important configuration. Typical results are presented and discussed. The effects of varying the vessel length to diameter ratio, the support spacing to vessel length ratio, and the wall thickness to diameter ratio are examined; the effects of radiusing the edges and horns of the saddle are also studied.
Plastic collapse loads of cylindrical pressure vessels supported by rigid saddles
Authors: Tooth A S , Jones N
Published: July 2007

The plastic collapse of cylindrical pressure or storage vessels supported by rigid saddle supports is examined both experimentally and in an exploratory theoretical manner. Two cases are considered: (1) when the saddle is welded to the vessel, and (2) when the saddle and vessel are not welded.

It is found that the load to cause first yield is much smaller than the fully plastic load and thus there exists a considerable reserve strength even when a vessel is stressed up to yield. The object of this investigation is to examine this considerable reserve strength and to provide results which, when taken with previous elastic studies, should help to improve vessel and support design.
Recommendations for the measurement of R-curves using centre-cracked panels
Authors: Wheeler C , Eastabrook J N , Rooke D P , Schwalbe K-H , Setz W , De Koning A U
Published: July 2007

Experimental techniques for obtaining the R-curve, a measure of fracture toughness used for selection and quality assurance of thin-section materials, are discussed in the light of experience at RAE, DFVLR, and NLR. Detailed recommendations are made for R-curve measurement using centre-cracked panels.

To improve standardization, the procedure is more closely defined than in the proposed recommended practice for R-curve determination of the American Society for Testing Materials (ASTM), but machining costs are reduced by relaxing tolerances on specimen dimensions.

The crack length is measured by either a potential-difference of a compliance method, and the specimen is loaded to give uniformly increasing load-point displacement of crack-opening displacement. Constant rate of increase of load is not recommended. Optical measurement of crack length is not recommended. The R-curve is calculated by a method which avoids giving undue weight to measurements made at zero or small crack extensions.
Determination of fracture toughness of ductile materials using a reinforced double cantilever beam specimen
Authors: Woo C W , Kuruppu M D
Published: July 2007

A method of determining the fracture toughness of ductile material in the form of a reinforced double cantilever beam (RDCB) specimen is presented. The analysis makes use of the Dugdale strip yield model incorporated in the beam-on-elastic foundation model to represent the fractures of a DC3 specimen. Two different foundation models are considered. The first model assumes that one half of the RDCB acts as the elastic foundation for the other half and the second model assumes that the groove acts as the elastic foundation. The results of the groove foundation model are found to be closer to the experimental values based on the crack growth resistance curves than those of the beam foundation model. The results are further verified using a J control integral determination based on a two dimensional elastic-plastic finite element analysis.

The material used is 2024-T3, which is moderately ductile, and the proposed method yields fracture toughness values with a reasonable degree of accuracy.
Crushing analysis of rotationally symmetric plastic shells
Authors: De Oliveira J G , Wierzbicki T
Published: July 2007

The crushing analysis of rotationally symmetric plastic shells undergoing very large deflections is presented. A general methodology is developed and simple closed-form solutions are derived for the case of a conical shell, a spherical shell under point load, a spherical shell crushed between rigid plates and under boss loading, and a spherical cap under external uniform pressure.
Pressurized non-circular member—effect of mean-line form
Authors: Holland M
Published: July 2007

Using an energy analysis, it is shown that for each aspect ratio and for a particular family of curves representing the mean-line form, there will be one particular form which ensures that the maximum bending moment acting on the member takes a minimum value.

The traditional elliptic mean-line form currently used for some heat exchanger tubes, sluice-value bodies, and some aircraft monocoque stiffening frames, could be improved by using the optimum form which has heat transfer and fluid-flow characteristics similar to those associated with the elliptic profile (sometimes an essential feature of the design).

It is shown that when the aspect ratio is equal to two and the elliptic shape is replaced by an optimum form determined by the method described above, the uniform applied pressure can be increased by fifteen and one-half per cent before the maximum stress in the two members becomes equal.
Thermal ratchetting of axially loaded tubes operating in the creep range
Authors: Hyde T H , Webster J J , Fessler H
Published: July 2007

Finite element predictions of ratchetting and creep behaviour are compared with experimental data for axially loaded tubes subjected to axisymmetric cyclic temperature variations.

Eleven tubes made of a lead alloy model material which creeps at ambient temperature were tested. Strain gauges were used to measure the ratchet and creep strains.

In the finite element calculations it was assumed that no plasticity-creep interactions occur. Reasonably good predictions of ratchet strains were obtained, particularly in the range of most practical interest. Some of the discrepancies between ratchet and creep results can be accounted for by considering the results from a small number of uniaxial plasticity-creep interaction tests.
Experimental theramal ratchetting data for a component with a stres concentration
Authors: Hyde T H , Webster J J
Published: July 2007

The result from eleven tests of lead alloy model shouldered tubes, subjected to constant axial mechanical loads and cyclic, axisymmetric thermal shocks are described. Dwell periods between 0.5 h and 24 h allowed creep to occur between the thermal shocks. Electrical resistance strain gauges were used to measure ratchet and creep strains.

At low mean axial stresses (< 0.94σy), it was found that the ratchet strains increased with load and dwell period. It was also found that the ratchet strains in the fillet region were significantly larger than those in the shank and are induced at lower mechanical loads than those in the shank. For higher stresses, the ratchet strains were found to be relatively insensitive to both load and dwell period. Also, the ratchet strains in the fillet and shank were found to be of the same magnitude.
Predicting the thermal ratchetting and creep behaviour of a component with a stress concentration
Authors: Hyde T H , Webster J J
Published: July 2007

Finite element and ‘upper bound’ predictions of ratchetting and creep are compared with experimental data from two axially loaded shouldered tubes subjected to axisymmetric cyclic temperature variations.

The shouldered tubes were machined from chill-cast bars of a lead alloy material. Electrical resistance strain gauges were used to measure the ratchet and creep strain.

The results show that ratchet strains can accumulate significantly faster in stress concentration regions when compared with plain tube regions. Acceptable predictions were obtained for the ratchet strains. The discrepancies between the predicted and measured dwell period strains were due to neglecting the material plasticity-creep interactions. Some simple methods for estimating the strains are suggested.
Creep stress redistribution in a visco-elastoplastic strip containing a hole
Authors: Nishitani T , Kobayashi N
Published: July 2007

The time dependent variation of the stress concentration factor during creep is discussed for a visco-elastoplastic celluloid strip containing a circular hole. The variation of stress at this stress raiser is analysed by means of a proposed photo-viscoplasticity method for several cases of tensile loading.
Stress concentrations due to axial tension and bending of loaded axisymmetric projections
Authors: Hyde T H , Marsden B J
Published: July 2007

The finite element method has been used to investigate the behaviour of axisymmetric loaded projections (e.g., bolts) subjected to axial tension and bending.

The results show that existing data for stepped shafts, which have the axial tension and bending loads applied remote from the region of the step, cannot be applied to loaded projections with the same geometry.

For h/d (head thickness to shank diameter ratio) values greater than 0.66 and 0.41 for axial tension and bending, respectively, the stress concentration factors are independent of h/d, load position, and D/d (head diameter to shank diameter ratio) for D/d in the range 1.5 ≤ D/d ≤ 2.0. Smaller h/d values result in large increases in the stress concentration factors due to dishing of the head.
Stresses in a bottoming stud assembly with chamfers at the ends of the threads
Authors: Fessler H , Jobson P K
Published: July 2007

Three-dimensional, frozen-stress, photoelastic models of 1 in. BSW studs and tapped blocks have been loaded axially and in torsion. Detailed distributions of axial, principal, and shear stresses show that, as expected, the greatest stresses occur near the front end of engagement, but there are secondary peaks near the back end due to the stresses set up by ‘locking’ the stud at the bottom of the hole.

Chamfering the first two turns of the thread of the block eliminates the stress concentration at the front of the block itself but does not reduce the stud stresses significantly. Similarly, the stresses at the back of engagement are reduced if the stud thread is chamfered.
Elastic-plastic analysis of thermally loaded cylindrical shells
Authors: Gamby D , Bourdillon H
Published: July 2007

A new incremental procedure is proposed, that widens the scope of Marcal's stiffness method; it is notably applicable to non axisymmetrically heated tubes encountered in solar superheaters or in more conventional boilers.
Experimental and theoretical correlations for elastic buckling of axially compressed stringer stiffened cylinders
Authors: Ellinas C P , Croll J G A
Published: July 2007

A re-examination of some 240 past experiments on the general elastic buckling of axially loaded stringer stiffened cylinders suggests that the observed buckling behaviours exhibited a degree of imperfection sensitivity considerably higher than that so often ascribed to them. It is demonstrated how the underestimation of these experimental knock-downs may have resulted from the use of theoretical models insufficiently representative of test conditions. By incorporating a more precise modelling of the test shells the present analyses show how, contrary to a widely held belief, the potential knock-down factors for general elastic buckling can approach those of the isotropic cylinder. Furthermore, despite the relatively perfect nature of many of the test shells, the recently described ‘reduced stiffness analysis’ method provides lower bounds of the observed experimental scatter that are sufficiently reliable to recommend this method as a basis for future design.
Effect of contributions from bending in evaluation of axial strain in rods with circular cross-section
Authors: Lagerkvist L , Sundin K-G , Lundberg B
Published: July 2007

Contributions from bending to the evaluated axial strain in an elastic rod are commonly suppressed by forming half the sum of measured surface strains at diametrically opposite positions. A simple method is presented which gives a useful estimation of the bending suppression (the ratio of the bending strain to the absolute value of the evaluated axial strain when a rod is subject to bending only) from (i) optically measured mis-positioning, and (ii) estimated differences between the gauge constants for the two strain gauges. Good agreement is obtained with results obtained from strain measurements on a rod loaded in bending.
Some useful results in the classical Hertz contact problem
Authors: Sackfield A , Hills D A
Published: July 2007

A resumé is given of the results available in the literature for the stresses resulting from frictionless loading by Hertz pressures. The problem is posed formally in tensor notation and new convenient forms are given for the complete stress field, in the general elliptical-patch case.
The determination of the equivalent strain in finite, homogeneous deformation processes
Authors: Sowerby R , Chakravarti P C
Published: July 2007

This article considers the in-plane deformation of a thin, incompressible membrane undergoing an arbitrary, but finite, homogeneous deformation mode. No discontinuities in the loading system are permitted, and the nature of the straining process is assumed unchanged from beginning to end. For these restricted deformation modes a technique is described whereby the equivalent strain can be evaluated by measuring the initial and final shape only of a finitely deformed grid marked on the surface of the membrane. The analysis is performed with reference to an initially square or rectangular grid of lines, since the nodes of the grid facilitate the experimental measurements. A distinction is drawn between homogeneous deformation and the special case of pure homogeneous deformation which results in the same shape change. In the latter mode a pair of principal axes can be identified which remain orthogonal during the entire deformation history; while for the former mode there is no such line pair which preserves orthogonality throughout the deformation. The article concludes with a brief discussion on the determination of strain in industrial stampings.
Three-dimensional, elastic stress distribution in end-milled, keyed connections
Authors: Fessler H , Eissa M
Published: July 2007

Three- and two-dimensional, photoelastic, frozen-stress models of Standard metric and inch keyed connections have been loaded in torsion. Results from models with three different key lengths are presented here and related to the axial distribution of torque transmission.

Empirical equations for the elastic stress concentrations in the prismatic part of key and keyway at the positions of contact between key and shaft have been derived for any likely width, thickness, and length of key, keyway fillet size, and applied torque. A simple method of eliminating stress concentrations in the keyway end is described.
Determination of stable crack growth resistance of ductile material using an rdcb specimen
Authors: Woo C W , Kuruppu M D
Published: July 2007

A method to determine the plane stress fracture resistance curve for the stable crack growth of ductile material is presented. A reinforced double cantilever beam (RDCB) specimen of thin grooved section is used to determine the COD and JR of aluminium 2024-T3 material which exhibits substantial stable crack growth. The method makes use of the BEF and Dugdale models to determine the load-deflection behaviour of the specimen. The derivation is based on the experimentally determined load and crack extension values.

The crack growth resistance for specimens of different thicknesses are deduced using the proposed method and are compared with those of the compliance method as well as the finite element method.
Elastic-plastic-creep behaviour of a compact-tension specimen
Authors: Hyde T H , Low K C , Webster J J
Published: July 2007

Elastic, elastic-plastic, elastic-creep, and elastic-plastic-creep finite element calculations have been performed for a compact-tension specimen under plane-stress conditions. The von-Mises effective stress criterion and the Prandtl-Reuss flow rule were assumed for both the plastic and creep deformations. A 4-line stress-strain relationship with a UTS value 1.48 times greater than the yield stress was used. A strain hardening, Norton-Bailey creep law was assumed.

A fairly course mesh of 8 noded, isoparametric elements was found to be adequate for determining reference stress, crack tip opening displacement, J-contour integral, and C∗-contour integral values.

The UTS zone, rather than the yield zone, was found to have a significant effect on the C∗-contour integrals and CTOD rates. An approximate method of determining C∗ values was found to give reasonable results, particularly for low load cases, i.e., when the UTS zones are small. Hence, provided care is taken not to perform tests at very high loads, accurate C∗ values can be determined from experimentally determined pin displacement rates.
Deformation and stability studies of thin-walled domes under uniform external pressure
Authors: Ross C T F , Mackney M D A
Published: July 2007

Fifty hemiellipsoidal domes were cast in solid urethane plastic, with profiles which varied from oblate to prolate shapes.

The domes were subjected to external hydraulic pressure in a test tank and tested to failure. All the domes appeared to fail through elastic instability, the oblate shapes failing axisymmetrically, and the prolate shapes failing asymmetrically in a lobar manner.

The theoretical analysis was carried out via the finite element method, and stiffness matrices were developed for an axisymmetric element of constant meridional curvature. The element was capable of being applied to axisymmetric deformation or axisymmetric and asymmetric instability, and it was generated numerically.
Determination of mode I stress intensity factors in surface-flawed plates by scattered-light photoelasticity
Authors: Holmes J W , Holmes R A , Conway J C
Published: July 2007

The scattered-light photoelastic technique was utilized to determine Mode I stress intensity factors associated with a semi-elliptical surface flaw in a plate subjected to uniaxial tension. Stress intensity factors were experimentally determined for the point of maximum flaw penetration and the point of intersection of the flaw border with the free surface of the plate. Experimental results are compared to those obtained in a three-dimensional finite element analysis with reasonable agreement being shown.
Creep life of AISI 316 stainless steel loaded at constant strain rate
Authors: Kelly D A , Morrison C J
Published: July 2007

Results of tensile tests at constant strain rate on an AISI 316 stainless steel at 550°C are presented and shown to imply that mathematical modeling of the creep life of ductile materials subject to variable load must take into account their short term behaviour and a practical failure criterion.
Stress intensity factors for cracked C-shaped and ring type test-pieces
Authors: Webster G A , Klintworth G C , Stacey A
Published: July 2007

Two boundary integral equations (BIE) methods have been applied to obtain stress intensity factor K calibrations for cracked C-shaped, split-ring (SR) and ring specimens. It is shown that good agreement is achieved with experimental determinations and other information in the literature. Also fatigue crack growth studies have demonstrated that all the shapes are suitable for establishing the fatique properties in the radial direction of thick-walled tubing. The ring specimen is shown to be particularly appropriate for determining fatigue crack growth behaviour in tubes which have been autofrettaged.
Boundary integral equation stress analysis of a rotating disc with a corner crack
Authors: Tan C L
Published: July 2007

The analytical and numerical formulation of the boundary integral equation (BIE) method are outlined for the general case in linear elasticity. Using this method, three-dimensional linear elastic fracture mechanics analyses of a rotating disc with a corner crack at its bore are carried out. The cases considered are for a disc with external to internal radius ratio of 8 and with thickness equal to the diameter of the central bore. Two different crack shapes, namely, a quarter-circular crack and a quarter-elliptical crack with ellipse aspect ratio of 0.75, are analysed. For each of these shapes, corner cracks penetrating 50 per cent and 75 per cent of the disc thickness are treated. Stress intensity factor solutions for these cracks are presented for the centrifugal loading condition, as well as when the disc is subjected to a radial tensile stress at its external circumferential periphery.
Elastic-plastic stress analysis of a cracked thick-walled cylinder
Authors: Tan C L , Lee K H
Published: July 2007

The boundary integral equation (BIE) method for two-dimensional elastic-plastic stress analysis is applied to an internally pressurized thick-walled cylinder containing a radial crack. Two different types of material are considered, namely, an elastic-perfectly plastic material and a work-hardening material. The loading conditions applied include the case when the internal pressure also acts on the crack faces, and the case when it does not. Results are presented showing the plastic zone development in the cylinder and the variations of the fracture mechanics parameter, the J line integral, with increasing internal pressure.
Applications of the boundary element method to large strain large deformation problems of viscoplasticity
Authors: Chandra A , Mukherjee S
Published: July 2007

A boundary element formulation for the solution of viscoplasticity problems in the presence of large strains and displacements is presented in this paper. The BEM formulation is based on an appropriate form of Betti's reciprocal theorem together with a time marching scheme using an updated Lagrangian approach. Numerical results are presented for various plane strain and plane stress viscoplasticity problems. Results from the boundary element analysis are compared to those from the finite element analysis with regard to accuracy and computational efficiency.
Large deflection analysis of clamped annular sector plates
Authors: Srinivasan R S , Thiruvenkatachari V
Published: July 2007

Thin annular sector plates undergoing large deflections due to lateral loads are considered in this paper. For such plates exact solutions are not available. A matrix method using integral equation of beams and the Newton Raphson procedure has been adopted for the analysis of clamped annular sector plates. Numerical values for the deflection, the membrane and the bending stresses at the interior of the plate, and the bending stresses at the edges of the plate are obtained. A parametric study has been carried out by varying the sector angle from 30 to 90 degrees in steps of 30 degrees, and the ratio of the inner and outer radii from 0 to 0.6 in steps of 0.2. The results are presented in non-dimensional graphical format.
Yield and shakedown states in the contact of generally curved bodies
Authors: Hills D A , Sackfield A
Published: July 2007

The known elastic limits and shakedown limits are reviewed for the problem of Hertzian contact with and without friction. Additional values are then derived where the literature is deficient, i.e., for the case of a general elliptical contact with a frictional force applied parallel with one of the axes. A new limit is then derived for the case when the residual stress is ‘cylindrical’ in nature.
Stresses in and deformations of swivel ring flanges due to bolt loading
Authors: Hyde T H , Marsden B J
Published: July 2007

Photoelastic and finite element methods of analysis were used to study the behaviour of swivel ring flanges. The use of tapers on the ‘back faces’ of flanges or of small, local reductions in flange thickness, to control the ‘load position’ and hence reduce the stresses, were investigated. The effectiveness of these techniques was assessed by comparing results with those for the more usual lapped joints between the flanges and rings. It was found that the taper and ‘reduced thickness’ techniques can result in significantly reduced stresses for the same bolt loads. However, the largest stress, which occurs in the fillet regions of the flanges, is not reduced by as much as the design codes predict. The friction conditions between the flange and ring were also found to have a significant effect on the stresses
Photoelastic determination of stress intensity factors for single and interacting cracks and comparison with calculated results. Part I: Two-dimensional problems
Authors: Phang Y , Ruiz C
Published: July 2007

Various methods for the determination of stress intensity factors from photoelastic data obtained from models containing narrow slits, are compared by reference to the case of a wide plate with a central crack. The linear slope method is applied to a number of two-dimensional problems when cracks interact with free surfaces or with other cracks.
Photoelastic determination of stress intensity factors for single and interacting cracks and comparison with calculated results. Part II: Three-dimensional problems
Authors: Phang Y , Ruiz C
Published: July 2007

The application of the frozen stress photoelastic technique to the determination of stress intensity factors in two-and three-dimensional problems is discussed. The technique, involving casting flaws by the insertion of thin shims, is found to give accurate results for problems with a known exact analytical solutions: a central crack in a wide plate and an embedded circular crack. It is applied to other problems without a known solution or for which only approximate solutions, often providing inconsistent answers exist.
Poisson's stresses in fibre composites. I: Analysis
Authors: Ostrowski J , Will G T , Piggott M R
Published: July 2007

Two methods have been used to evaluate the transverse stresses when an aligned fibre composite is stressed in the fibre direction. A single fibre model is shown to overestimate the stresses at the fibre-matrix interface by about 20 per cent compared with a finite element solution for an infinite array of fibres. Using relatively few fibres in the finite element analysis, however, only gives very approximate stress distributions. With fibre volume fractions in the range 0-0.50 the average radial stresses across the fibre-matrix interface are always compressive, and can be represented by a relatively simple formula with an accuracy which is normally with in a few percent of the finite element value.
Biaxial stress effects in a reinforced cracked sheet
Authors: Dowrick G , Cartwright D J
Published: July 2007

The effect of biaxial stress on the stress intensity factor and rivet loads has been determined for a single crack in a reinforced sheet. It is shown that for a sheet reinforced by intact orthogonal stiffeners the stress intensity factor is unaffected by the stress applied parallel to the crack. In this respect its behaviour follows that of a crack in a unstiffened sheet but is contrary to conclusions drawn from previous results in the literature on biaxially stressed stiffened sheets. However, a re-analysis of these existing results shows them to be consistent with the present finding that the stress intensity factor is independent of the stress applied parallel to the crack in a sheet stiffened by orthogonal intact stiffeners. For a sheet in which a stiffener is broken across the crack line a tensile stress parallel to the crack is shown to reduce the stress intensity factor compared to that which exists for a uniaxial tensile stress only, applied perpendicular to the crackline. The opposite effect is shown to occur for a compressive stress parallel to the crack in the biaxially stressed sheet. For a cracked sheet reinforced with a patch, it is shown that the stress intensity factor will also depend on the stress applied parallel to the crack. The various effects of biaxial stress are illustrated with new results for the stress intensity factor, rivet loads, and maximum stiffener stress for a sheet having equally spaced stiffeners along line perpendicular to the crack.
Aluminium alloy cylindrical jack body failure investigation
Authors: Webber D , Maddox S J
Published: July 2007

The premature fracture of a jack body during pressure testing drew attention to the need to examine the integrity of the body in the presence of defects, from the point of view of fracture and fatigue, and to re-examine the adequacy of existing inspection measures. This assessment was based on fracture mechanics, and the methods used and conclusions drawn are described in the present paper.
Interrelation between static and dynamic stress intensity factors and their evaluation by caustics
Authors: Theocaris P S , Papadopoulos G A
Published: July 2007

The stress field around the tip of a crack propagating with constant velocity depends on the dynamic stress intensity factors KId and KIId if both of them are operative. These factors may be defined by their corresponding static values KIS and KIIS multiplied by convenient correction factors depending mainly on the crack propagation velocity c and on the longitudinal ( c1) and shear ( c2) was velocities of the material of the specimen. In this way a quantitative relation between dynamic and static components of the stress intensity factors is established. The dependence of this relation on the various components of velocities is investigated in this paper. It is also shown that the experimental method of reflected caustics gives an evaluation of this relation for various crack velocities and angles of inclination of the propagating crack.
Stress concentrations due to axial loading applied to axisymmetric internal projections on hollow tubes
Authors: Hyde T H , Marsden B J
Published: July 2007

Stress concentration factors due to the axial loading applied to axisymmetric, internal projections on hollow tubes have been obtained by using the finite element method. A range of tube and projection dimensions and fillet radii have been covered by the investigation. It was found that all of the results could be presented on just two graphs. Hence the stress concentration factor, for any shape within the range investigated, can be quickly determined. A simple relationship between stress concentration factor and ‘load position’ was also found to exist.
Mode I and II fracture of adhesive joints
Authors: Anandarajah A , Vardy A E
Published: July 2007

The compliance method is used to determine strain energy release rates in mode I and II fracture of adhesive bonded joints. A strong dependence of the strain energy release rates upon the adhesive thickness is found.

Standard compact tension and compact shear specimens are used. It is found that the former are well suited to the investigation of mode I fracture, but that the latter are less well suited to mode II investigations.

Attention is focussed on bond failures caused by cracks propagating between an adhesive and an adherend. Experimental and theoretical arguments are combined to determine the critical strain energy release rates at which such failures occur. The critical values are shown to be strongly dependent upon the method of surface preparation as well as upon the physical properties of the materials used.
Multiaxial strength tests for brittle materials
Authors: Fessler H , Fricker D C
Published: July 2007

Matchstick and coin shaped specimens are used to determine the material strength consistency and mean fracture strength under five different stress rations, using Weibull statistics.

Many practical loading modes of these simple shapes are assessed. For the best, the necessary experimental work and results of the analyses are presented and illustrated for as-fired reaction-bonded silicon nitride (RBSN) tested at room-temperature.
Stresses in axially loaded cylinders with imperfections and cracks
Authors: Godoy L A , Croll J G A , Kemp K O
Published: July 2007

The combined effects of imperfections in the form of the meridians and meridional cracks in axially loaded cylindrical shells are studied by means of a finite element programme capable of handling well defined, discrete cracks. Two basic mechanisms are shown to occur in shells in such a state: first, a redistribution of vertical load away from the cracked zone, and second, a redistribution from hoop membrane to meridional bending action.

The mechanics of behaviour of shells with imperfections in the geometry and cracks are systematically studied by examining the effects of shell, imperfection, and crack characteristics, so that the dominant parameters controlling the linear elastic response of the shell can be isolated. Numerical experiments show that those parameters that influence the behaviour in an uncracked imperfect shell also influence the stresses accompanying cracking.
Experiments on perforated plates subjected to shear
Authors: Narayanan R , Chow F Y
Published: July 2007

Experiments on the buckling and ultimate capacity of thin-walled steel web plates containing circular and square cut-outs are reported. Some 64 tests were carried out on plates containing either one or two holes. The parameters varied included the size of the hole and the eccentricity of the location of the hole.

For an increase in the eccentricity of the hole, the shear buckling coefficient increased when the opening was located in the compression diagonal and decreased when it was in the tension diagonal; it was found to be insensitive to the location of the hole, for small openings.

Approximate formulae are suggested in the paper for computing the shear buckling coefficients for plates with central and eccentric holes, and are suitable for use by designers. A method of predicting accurately, the ultimate capacity of the web is presented.