bluuebunny/crossref_metadata_2025 huggingface dataset:
A note on the elastic stress in tunnel linings
Authors: Jordan D. W.
Published: July 2007

A circular tunnel lining is idealized as a perfectly elastic annulus either keyed to, or a sliding fit in a hole in an infinite elastic medium of different Young's modulus, the system being under stress at infinity. The solution to this problem is used to give a qualitative discussion of two situations:

1 The resistance of a tunnel lining is limited amongst other things by its inability to withstand tensile stress. It is shown that in the above idealization, the more flexible the lining the less likely are tensions to arise. Such flexibility might be achieved by allowing the lining freedom to slide relative to the surrounding rock rather than by keying it to the walls, by making it of laminated construction or by lowering its Young's modulus. Increasing the thickness may increase the liability to tension. 2 As a means of estimating the load on a lining, gauges may be placed to measure circumferential strain, and from these measurements the load is deduced by assuming that the lining behaves like a bending beam. A difficulty in interpreting such measurements is pointed out in the case of a keyed lining, when the shearing stresses are very large.
Incremental extension of mild steel beams in reversed bending
Authors: Royles R
Published: July 2007

The incremental extension of rectangular section mild steel beams under cycles of symmetrical reversed bending is examined at a frequency of 10 c/min. An explanation of this phenomenon is outlined on the basis of changes in the geometry of the cross-section and the introduction of radial stresses.
The crack opening displacement approach to fracture mechanics in yielding materials
Authors: Burdekin F. M. , Stone D. E. W.
Published: July 2007

An introduction is given to the fracture mechanics approach employing the concept of crack opening displacement for application to situations in which linear elastic fracture mechanics is invalidated by yielding. The hypothesis of a critical crack opening displacement to fracture has been examined experimentally using mild steel specimens of vastly differing dimensions. Subsidiary experiments have been carried out to define the factors responsible for the apparent effect of absolute size on the results. A theoretical analysis simulates elastic-plastic conditions to give a relationship between applied stresses and strains, crack length, and crack opening displacement.
Measurement of thermal strains in a free rectangular tapered plate
Authors: Webber J. P. H.
Published: July 2007

Thermal strains in the axial direction of an aluminium alloy tapered plate specimen were measured under steady state conditions by means of wire resistance strain gauges. The active gauges were temperature compensated by fixing dummy gauges to small aluminium slips and placing them in the same environment as the active gauges. This technique is discussed in the text. In general it was found that the results substantiate a theoretical analysis.
An experimental investigation of a right-angled single unreinforced mitred-bend subjected to various bending moments
Authors: Jones N , Kitching R
Published: July 2007

It is well known that, upon the application of an in-plane bending moment, the initially circular cross-section of a curved pipe tends to flatten and become approximately elliptical in shape making it much more flexible than an equivalent straight tube.

Mitred-bends exhibit similar properties though the behaviour is far more complex. A comprehensive study of a 90° single unreinforced mitred-bend having a radius/thickness ratio of 19 has been performed by means of a stress-probing method.

In order to make the work more complete, results have been obtained for a similar bend when subjected to out-of-plane bending and twisting moments.

Experimental measurements of stress and flexibility for each type of loading are discussed and certain modifications suggested to existing design procedures.
Definition of the yield point in plasticity and its effect on the shape of the yield locus
Authors: Hsu T C
Published: July 2007

Three different definitions of the yield point have been used in experimental work on the yield locus: proportional limit, proof strain and the ‘yield point’ by backward extrapolation. The theoretical implications of the ‘yield point’ by backward extrapolation are examined in an analysis of the loading and re-loading stress paths. It is shown, in connection with experimental results by Miastkowski and Szczepinski, that the proportional limit found by inspection is in fact a point located by backward extrapolation based on a small section of the stress-strain curve, near the elastic portion of the curve. The effect of different definitions of the yield point on the shape of the yield locus and some considerations for the choice between them are discussed.
A stiffness method for elastic-plastic shells of revolution
Authors: Marcal P V , Pilgrim W R
Published: July 2007

A stiffness method is proposed for the analysis of elastic-plastic shells of revolution with axisymmetric loading. A step-by-step method of integration is used in a computer programme developed to implement the method. Calculations were performed for a toroidal bellows and a torispherical pressure vessel head; the results agree with experimental values.
Analysis of elastic and elastoplastic strains in a notched plate
Authors: Esin A , Lambert T H
Published: July 2007

The photoelastic and moiré techniques are used to investigate elastic and elastoplastic distribution of stresses and strains around a 45° V notch with a circular base. It is shown that the plastic flow takes place in the highly stressed region; resulting in considerable increase in the strain ratios while lowering the stress ratios. The stress relaxation accompanying the plastic distortion causes significant changes in the general elastic distribution pattern.
Natural frequencies of cooling tower shells
Authors: Neal B G
Published: July 2007

A theoretical determination of the lowest natural frequencies of inextensional vibrations of hyperbolic cooling tower shells is first presented. It is shown that inextensional behaviour is only possible for certain types of support condition at the base, one of which consists of four pairs of inclined columns evenly spaced round the circumference which, at their points of attachment, only permit displacements normal to the plane of the shell.

Experiments to determine the natural frequencies and modes of vibration of a model shell are then described. This model, which was made by the electro-deposition of copper on a Perspex mould, could be supported at its base by up to forty pairs of inclined columns. Using only four evenly spaced pairs of columns the lowest natural frequencies of inextensional vibrations were first determined, and found to agree well with the theoretical values. The natural frequencies and modes of the extensional vibrations which occurred when the shell was supported by forty pairs of columns were then explored. Finally, the effect of removing some of the supports, thereby simulating a horizontal fracture in part of the shell, was studied.

The possibility of wind-induced vibrations occurring in practice is then considered. It is concluded that these are unlikely to occur unless the shell has already suffered damage, as for example by experiencing a horizontal fracture over part of its circumference near the base.
Plastic stress and strain concentration factors in a strip with a hole or notches under tension
Authors: Javornický J
Published: July 2007

Spread of plastic region and influence of severity of constraint are observed and concentration factors are evaluated by photoplasticity of celluloid. Suitability of photoplasticity for solution of practical problems is discussed.
Metrology of the photo-grid determination of fracture strain for a plate in bending
Authors: Hartlen R T , Jones L E
Published: July 2007

Aluminium plates (7/1 width/thickness ratio) were bent to fracture. Circumferential strain at fracture location (maximum value 0.26) was obtained by special plotting and extrapolation of (millimetre) photo-grid data.
Numerical solution of plane elastostatic problems by point matching
Authors: Hooke C J
Published: July 2007

A description of the point-matching technique and of its application to the solution of plane elastic problems is presented. The technique is then used to evaluate the stress distribution in a number of plane elastic problems, and the accuracy of the point-matching technique is assessed by comparing the results obtained with those obtained by other methods. Finally, the technique is used to calculate the stress-concentration factors for a bar, with two symmetrically placed U-shaped notches, loaded in tension.
Effect of Poisson's ratio on compression modulus
Authors: Lindley P B
Published: July 2007

Contributions to a compressive deformation can result from change of shape and change of size. For most materials these two contributions are of similar magnitude. For materials such as rubber which have a low shear modulus but a relatively high bulk modulus any restriction on their freedom to change shape can have a very marked effect on their stiffness in compression. Poisson's ratio is used to relate the relative magnitudes of shear and bulk moduli.
Axi-symmetric method for determining thermal stresses in pistons
Authors: Enderby L R , White D J
Published: July 2007

An axi-symmetric method, which is easy to apply and is quick in yielding an answer, is presented for the analysis of thermal stresses in pistons. The designer who wishes to use the method will find the relevant formulae collected together in Appendix 2.

The theory has been applied to four different pistons and it reproduced the general measured stress levels above the gudgeon-pin bosses, although the predicted stresses were in some cases up to 30 per cent lower than the maximum measured values. It is concluded that the method gives a useful description of the thermal stresses in this critical region.
Vibration of thick curved shells, with particular reference to turbine blades
Authors: Ahmad S , Anderson R G , Zienkiewicz O C
Published: July 2007

The application of a new thick shell element is described with reference to vibration problems. The element is derived from the general isoparametric solid and therefore allows shear deformations to be included. It can take up highly distorted shapes and is useful in such studies as vibration of turbine blades for which it is superior to elements based on thin-shell theory. This element can also be used for thin shells with caution, excessive length/thickness ratios being avoided.
Experimental stress analysis and its influence on design
Authors: Allison I M , Pomeroy C D
Published: July 2007

A report on the Fourth International Conference on Stress Analysis held at Cambridge, England, on 6-10th April 1970.
The importance of shear in the yield criterion for the bending of slabs
Authors: Wood R H
Published: July 2007

An impasse has arisen in present-day rigid-plastic theory for bending of slabs, in that exact solutions may not exist for certain combinations of shape, load, and boundary conditions. It is now shown, for the first time, that a complete elastic-plastic solution for a uniformly loaded square slab is unobtainable even with simple supports, in spite of the fact that an exact rigid-plastic solution is already well known. These discrepancies are traced to over-idealization of the yield criterion, in particular to the possibility of missing plastic-shear strains. The need for new experimental investigations is apparent, as well as for changes in the theory.
The constant-moment plate-bending element
Authors: Morley L S D
Published: July 2007

A non-conforming displacement triangular finite element is derived with quadratically varying displacements for use in plate-bending problems. It is shown that the element corresponds with a known constant-bending-moment element and provides, in consequence, an over-estimate of the influence coefficients. Convergence is also assured in advancing to successively finer mesh sizes. A few simple test problems are computed so as to illustrate the kind of accuracy which can be expected.
Torsional stiffness of plastic tubes reinforced with glass fibres
Authors: Ogorkiewicz R M , Sayigh A A M
Published: July 2007

Torsional stiffness of composite tubes made from glass fibres and epoxy resin by winding the fibres at different angles to the axis of the tubes is compared with the stiffness predicted by theoretical solutions.
A quick method of estimating the maximum stress in a longitudinally reciprocated bar
Authors: Beddoe B
Published: July 2007

A dimensionless form of transient solution for a single reversal of a uniform bar is derived and interpreted in terms of reflected stress waves. It is shown that the maximum bar stress is simply related to the function that specifies the reversal of the bar and to the ratio of the return time (defined as the time for a longitudinal wave to propagate twice the length of the bar) to the reversal time. Uniformly distributed viscous damping may increase the maximum bar stress.

This “one reversal” solution is invaluable for determining maximum stresses in cam-driven traverse bars on fibre-winding machines which carry uniformly spaced yarn guides. It can conveniently be used to determine the stress due to a regular succession of reversals and thereby provide solutions for continuous reciprocation, including resonant conditions, without recourse to Fourier analysis.
Tension-compression stress-strain curves from bending tests
Authors: Oldroyd P W J
Published: July 2007

A formula—Nadai's bending formula—is derived which enables the tension (or compression) stress-strain curve for a material to be obtained from the curve relating bending moment to curvature for a beam of solid rectangular section. The method is extended to give a formula which covers deformations in which reversals of plastic strain occur.

The results obtained from a unidirectional bending test made on annealed copper are compared with those obtained from a tensile test made on the same material and the accuracy of the stress-strain values obtained from the bending test is discussed. The results obtained from a reversed bending test are also compared with those obtained from a tension-compression test in which a specimen was first stretched and then compressed to its original length.

The limitations imposed by this method of obtaining the stress-strain curve for a material are examined and the advantages its presents in the study of the behaviour of materials under uniaxial stress are outlined.
A comparison between the tensile and compressive creep behaviour of an 11 per cent chromium steel
Authors: Tilly G P , Harrison G F
Published: July 2007

Comparative tensile and compressive creep behaviour at constant stress has been studied for an 11 per cent chromium steel. No significant differences were observed for stresses and temperatures of engineering relevance, i.e. producing lives greater than 200 h. High stresses, producing shorter tensile lives, caused creep to occur more rapidly under tension owing to an earlier development of tertiary-type deformation. It is suggested that the deformation mechanisms are similar for the two modes of stressing but development of stable cracks under tension produces more rapid creep behaviour during the later stages of life.
Thermal stresses in axially connected circular cylinders
Authors: Hallam C B , Ollerton E
Published: July 2007

Experimental and theoretical investigations are reported concerning the stresses and deflections which occur in a composite cylinder due to a uniform rise in temperature. The composite cylinder consists of two solid circular cylinders, made of dissimilar materials but having the same diameter, which are stuck together so that their axes coincide. The interface between the two cylinders is a plane prependicular to their axes, and the lengths of both parts of the composite cylinder can vary. The composite cylinder is assumed to be free of stress initially.

Theoretical results have been obtained by use of infinite-difference approximations to the governing equations and an iterative technique involving successive over-relaxation. These have been compared with experimental results obtained by a special application of the frozen-stress technique of photoelasticity.
A comparison of some curved two-dimensional finite elements
Authors: Bond T J , Swannell J H , Henshell R D , Warburton G B
Published: July 2007

This paper gives a series of examples which demonstrate to the stress analyst the value of high-order curvilinear finite elements. The examples given show the numbers of elements which are required to obtain a given accuracy in two-dimensional problems. It is shown that the curvilinear isoparametric family is extremely sensitive to certain types of distortion from the basic triangular or quadrilateral shape. Another new family of curvilinear elements is presented; these elements are slightly less accurate than isoparametric elements when the sides are mildly curved but are considerably better when the sides become greatly distorted.
Thermal stress analysis of plates and shallow shells by hybrid finite-element method
Authors: Tabarrok B , Hoa V S
Published: July 2007

A rectangular finite-element model has been developed for thermal-stress analysis of shallow shells. The elemental equations are obtained from a two-field variational principle which employs equilibriating stress fields within the elements and compatible displacement fields along inter-element boundaries. The extremization of the variational functional tends to satisfy the compatibility requirements within the elements and equilibrium conditions along inter-element boundaries. The element is employed for thermal-stress analysis of several examples and the numerical results obtained are compared with some analytical results.
Principal displacements in a pressurized elliptic cylinder: Theoretical predictions with experimental verification by laser interferometry
Authors: Holland M , Lalor M J , Walsh J
Published: July 2007

Equations for principal displacements in a uniformly pressurized thin-walled cylinder having an elliptic median line are developed from a knowledge of the expressions for tension and bending moment (1) at a general position in the cylinder wall. Displacements derived from these equations are compared with the simple expressions presented by Bresse (2) and MacAlpine (3).

The results of a detailed experimental study in which displacements were measured by a laser interferometer are used to assess the validity of the new displacement equations and to compare these with the predictions due to Bresse and MacAlpine.

It is shown that the equations developed here give good agreement with experimentally measured displacements and furthermore the predictions made in (2) and (3) grossly overestimate the displacement values and are also very much in error when stating that the minor-diameter expansion is of the same order as the major-diameter contraction. In the investigation reported here (ellipse with mean aspect ratio 1.9509) the expansion of the minor diameter is approximately twice the value obtained for the contraction of the major diameter.
Stress analysis of adhesive-bonded lap joints
Authors: Adams R D , Peppiatt N A
Published: July 2007

Stresses in a standard metal-to-metal adhesive-bonded lap joint are analysed by a two-dimensional finite-element method and comparisons are made with previous analyses. Particular attention is paid to the stresses at the ends of the adhesive layer. Unlike previous work, which assumes the adhesive to have a square edge, the adhesive spew is treated as a triangular fillet. The highest stresses exist at the adherend corner within the spew. Linear elastic behaviour is assumed throughout.

A rubber model is reported which confirms these results physically.

Good agreement was also obtained between some practical results and the finite-element predictions.
Prediction of endurance of fillet welds subjected to narrow band random loading
Authors: Jerram K
Published: July 2007

Fatigue crack propagation theory is used to predict the performance of cruciform welds subjected to either axial or bending narrow band random loading. The predictions are shown to provide a general representation of two sets of test data. It is concluded that the method enables narrow band random loading fatigue data for welds to be extrapolated to longer endurances.
Analysis of the large thermal bending of sandwich plates by a modified Berger method
Authors: Kamiya N
Published: July 2007

In order to apply the Berger method to the large thermal bending of sandwich plates, a modified method which employs average face strains is presented. The governing field equations are derived by the variational calculus for a thermal stress field when reduced strain energy is used, and they are formulated quasi-linearly with respect to the deflection and the differences of in-plane displacements on each face. As in the case of elastic plates, we may analyse sandwich plates that undergo thermal effects as well as mechanical loading with relative ease by the present method.
Torsional stresses in tubular specimens
Authors: Brown M W
Published: July 2007

Nadai's method for determining the shear stresses in solid cylindrical specimens subjected to torsional loads is extended to give the shear stresses in tubular specimens. A simple approximation to this solution is also proposed. Nadai's method may also be extended to anlyse the surface stresses of tubular specimens under combined axial and torsional loads.
Creep behaviour of components containing cracks—a critical review
Authors: Ellison E G , Harper M P
Published: July 2007

The prediction of crack propagation rates at elevated temperatures is important and this paper provides a critical review of available information and models for behaviour. For simplicity, behaviour is divided into three situations. At one extreme, a brittle situation may exist in which the material is brittle and the degree of constraint high, so that substantially plane strain conditions exist and stress redistribution at the crack tip is small; in this situation, the fracture is a local crack tip event and the stress intensity may be of use in correlaiting creep crack propagation data. At the other extreme, ductile behaviour may result if the material is ductile and the constraint is low with plane stress conditions prevailing; in this case, stresses at and near the crack tip will redistribute quickly down to more even values and conventional creep analysis techniques using, say, the reference stress will be most useful, particularly for estimating times to rupture. It is postulated that there is also a large intermediate régime, termed quasi-brittle, in which ductile materials under high constraint exhibit brittle characteristics. A new parameter, C∗, appears to be of more general use in this case and even be extended to other situations. Finally, an attempt is made to survey the information available on the effects of environment on crack propagation at high temperature, though conclusions are necessarily tentative at this time.
The effect of stress history on fatigue crack retardation behaviour
Authors: Obianyor D F , Miller K J
Published: July 2007

The effect of a decrease in stress range on fatigue crack propagation behaviour in mild-steel plate is investigated.

An experimentally determined equation relating the threshold stress intensity factor to stress intensity history is introduced and is seen to be a function of specimen thickness, which determines the crack tip stress—strain state. The delay period between the arrest of a stage II crack and its re-propagation is also a function of stress history and specimen thickness. The effect of increasing the initial high values of stress intensity is to cause the delay period and the threshold stress intensity to increase, both of which are beneficial, i.e. they increase fatigue lifetime.
Stresses at offset-oblique holes in thick-walled cylinders subjected to torsional loading
Authors: Stanley P , Day B V
Published: July 2007

The paper describes a three-dimensional photoelastic analysis of a series of Araldite models, each containing five or six different offset-oblique holes positioned in such a way that there were no ‘interaction’ effects between neighbouring holes. The geometric parameters defining a hole were varied systematically and the elastic stress distribution around the outer edge of each hole was obtained. The stress data are presented in non-dimensional form in terms of the shear stress in a plain cylinder. The dependence of the maximum stress on the geometric variables is discussed and it is shown that the stress concentrations for a wide range of hole/cylinder parameters can be reasonably well predicted from flat plate data. In some cases the predictions are unconservative.
Stress intensity factors in elastic plates with re-entrant corners asymmetrically loaded
Authors: Theocaris P S , Prassianakis J
Published: July 2007

The method of reflected caustics was extended to evaluate the complex stress intensity factors at the roots of re-entrant corners in elastic plates under generalized plane-stress conditions. The plates were considered loaded under a general mode of loading creating asymmetric stress states at the corners and, thus, engendering complex stress intensity factors at these zones.

For the evaluation of the complex stress intensity factors the coordinates of at least two points on the caustics are necessary whose polar coordinates on the respective initial curves on the specimen are defined in advance. These experimental data must be introduced into a system of six equations, four of which are linear and the remaining two non-linear. The solution of this system yields the components of the complex stress intensity factors with a high accuracy, independently of the form and shape of the caustics developed around the roots of the corners. This high accuracy was achieved among others by the fact that two terms in the asymptotic expansion of Muskhelishvili's complex stress function Φ(z) are taken into consideration for the evaluation of stress intensity factors.

The method was applied first to a symmetric notch whose theoretical solution is known, so that the accuracy of the method could be checked, and afterwards to an asymmetrically loaded notch whose theoretical solution does not exist. For this case a recurrent procedure was applied for checking the accuracy of the experimental results.
The compressive stiffness of a thin plate buckled in shear
Authors: Rothwell A , Allahyari H
Published: July 2007

The loss of compressive stiffness of a thin square plate buckled in shear is calculated. Two cases are considered, first a perfectly flat plate, and second a plate with an imperfection amplitude equal to 10 per cent of the plate thickness. Changes in shear stiffess are also plotted. The analysis is by a finite-element method. Substantial reductions in compressive stiffness due to shear buckling are found, with further variation in stiffness as the buckling mode develops. The significance of these results in the design of a stiffened shear web is examined. It is shown that, by a suitable design procedure, the corresponding loss of efficiency can be made quite small.
The effect of transverse pressure loading on the thermal ratcheting of circular plates
Authors: Hyde T H
Published: July 2007

Many components in conventional and nuclear power plant and chemical plant are subjected to steady mechanical and cyclic thermal loads. The life of such components may be governed by the accumulation of inelastic strain and/or deformation (i.e., ratcheting).

Elasto-plastic finite-element results for a circular plate with radially movable, direction fixed edges, subjected to steady membrane loads, steady transverse pressure loads, and cyclic through-thickness thermal loads, are given. A temperature independent, elasticperfectly plastic material model is assumed. Plastic strains are governed by the von-Mises effective stress criterion and the Prandtl-Reuss flow rule. Cyclic hardening (or softening) effects are not considered. The results are compared with the Miller-Bree uniaxial model (1)(2)(3)†

The results have been normalized with respect to the material properties so that they may be applied to plates made from any material which may be represented by the material model.
A novel mapping finite element method for stress analysis in two dimensions
Authors: Nath B , Nath P
Published: July 2007

A mapping finite element method has been proposed in this paper for the solution of elasto-static problems in two dimensions. In this method the physical problem domain is mapped into an ‘image’ domain using exponential-polar type mapping functions. Properties of finite elements in the image domain are also obtained in accordance with the transformation implemented; these elements are then used to solve the problem in the image domain, subject to the appropriately transformed boundary conditions.

Results of examples considered show that the proposed method, which is, incidentally, no more difficult or cumbersome to implement than the standard FEM, gives significantly better accuracy than when the standard FEM is used to solve the problem in the physical domain, using the same number of equations. Furthermore, since physical space is logarithmically condensed into the image space, the method is capable of dealing with large aspect ratio problems more simply and economically than is possible with the standard FEM or the boundary element method.
Method of fracture toughness determination in sidewall of a pneumatic tyre
Authors: Chow C L
Published: July 2007

A method for determining the fracture toughness of a pneumatic tyre sidewall was developed. Conventional methods of fracture toughness determination require the structural material to be tested independently of the structure. the proposed method allows fracture toughness to be measured directly from the type sidewall. Two advantages follow: (i) elimination of the need for duplicating the identical cured sidewall properties in the testpiece, and (ii) avoidance of the buckling inherent in thin sidewall test specimens.

The pneumatic tyre chosen for the investigation was a 7.75–14 bias passenger tyre with a two-ply nylon carcass. An artificial crack was created in the tyre sidewall and the cracked tyre was loaded by inflation pressure. The experimental parameters taken from the tyre include the inflation pressure, volume, and crack opening area at different crack lengths. Based on a quasistatic energy analysis, the pressure-volume-crack length diagram was used to graphically determine the sidewall fracture toughness. In addition, an equation based on the reciprocal theorem for a cracked body and netting analysis was derived and used to analytically determine the sidewall fracture toughness. The computed fracture toughness compares reasonably well with the measured G values via the experimental approach.
Two and three parameter representations of crack-tip stress fields
Authors: Chona R , Irwin G R , Shukla A
Published: July 2007

An analytical technique is developed to determine, from experimental photoelastic data, parameters additional to the stress intensity factor, K, required to provide an adequate representation of the stress field in an enlarged region around a crack tip. Various methods for the evaluation of these parameters from isochromatic fringe patterns are used to show that a meaningful analysis of experimental data requires the use of a stress field representation involving more than two parameters.
Stress analysis of axial flow cooling fans
Authors: Ramamurti V , Shanmugavel T
Published: July 2007

Tests on automobile radiator cooling fans of three types of construction pressed out from sheets are reported. The blades of the fans are treated as twisted (from tip to root) cantilever beams (fixed at root) for the purpose of analysis. The effects of centrifugal force, driving torque, and the axial thrust over the blade due to air flow are taken into account. Air flow measurements are obtained using a pitot-static probe. The input power for various speeds is also recorded. The stress values are verified with the strain gauge readings taken at the root and at mid span. The effects of twist angle and number of blades are also discussed. The study does not include riveted construction.
Experimental and finite element studies of circular cylindrical shells loaded radially through a central pad
Authors: Dawe D J , Ucmaklioglu M
Published: July 2007

Examination is made of the static linear response of circular cylindrical shells to a radial loading applied halfway along the shells: the chief concern is with shells in which the loading is applied by way of a circular pad containing a small concentric hole. The examination comprises tests on physical models, in which point displacements and strains are measured, and numerical studies based on the use of the finite element method. In the numerical studies two markedly different types of element are used and particular attention is paid to the modelling of the pad region of the cylinder pad combination. Good correlation between test measurements and numerical results is exhibited for radial displacement and for stresses, even when the pad itself is removed from the finite element models by appropriate specification of boundary conditions which reflect full pad rigidity.
Peak stresses near narrow rectangular notches, with rounded corners, subjected to tensile and shear loading
Authors: Hyde T H , Yaghi A
Published: July 2007

The finite element method is used to determine the peak stress for narrow rectangular notches, with rounded corners, for a range of notch width to corner radius ratios, under mode I, mode II, and mixed-mode loading conditions. It is shown that the specific geometry and loading conditions are unimportant and that the loading is conveniently characterized by the mode I and mode II stress-intensity factors for an equivalent crack. Superposition of peak stresses for mode I and mode II conditions allows the peak stress in a semi-circular notch to be obtained from simple equations describing the surface tangential stress distributions. A notch shape factor, which dependes only on the notch width to corner radius ratio and mode-mixity parameter, is then used to modify the peak stress values obtained for a semi-circular notch. The method provides a relatively cheap and efficient means of determining stress concentration factors for what can appear to be complex geometries and loading situations.
An improved collapse axis on the R6 FAD for combined tension and bending loading
Authors: Kristiansen N ø , Turner C E
Published: July 2007

Experimental and computational studies were made of a number of single edge notch (SEN) specimens loaded through eccentric pins with notch depth ratios 0.21 and 0.52. It was found that as the applied load was increased the formation of a plastic hinge mechanism caused the ligament to shift sideways and in turn alter the ratio of bending to tension loading. The two different assumptions, constant and variable bending to tension ratio, gave very different paths in the moment-load ( M-Q) space, and failure lines when plotted on the R6 Fracture Analysis Diagram (FAD). An improved expression for normalized load, Sr, for SEN geometries under a linear loading system was obtained by including a plastic constraint factor in the uncreacked lower bound solution. For the pin-loaded SEN specimens under a non-linear loading system, it was shown that Sr based on ‘true path lengths’ in the yield diagram gave a failure curve which was in good agreement with the R6 Rev3 solution.
Large deformation finite element analysis of non-linear viscoelastic membranes with reference to thermoforming
Authors: Shrivastava S , Tang J
Published: July 2007

This paper reports on the development of finite element formulations and computer programs for modelling free and constrained inflation of thin polymeric sheets in the context of thermoforming of plastic articles. In recognition of the generally time-dependent viscoelastic behaviour of polymers, and the large strains encountered in thermoforming applications, the material is modelled as non-linear visoelastic. For this purpose the constitutive relation proposed by Christensen (1)† is adopted, assuming the relaxation function to be exponential. Most of the published work on non-linear viscoelastic membranes deals with simple axisymmetric geometries, while the finite element formulations presented in this work are for both axisymmetric and non-axisymmetric membrane inflations, including contact against constraining surfaces. Both frictionless and slipless idealizations of contact conditions are studied. The finite element solutions of free and constrained inflations of circular membranes serve as illustrative examples for the axisymmetric case, while those for elliptical membranes demonstrate the non-axisymmetric cases. Comparison of the finite element results with the analytical solutions obtained (Appendix 1) for some simple free and constrained inflation problems shows good agreement.
Three-dimensional deformations in a single-lap joint
Authors: Tsai M Y , Morton J
Published: July 2007

The three-dimensional nature of the state of deformation in a single-lap test specimen is investigated in a linear elastic finite element analysis in which the boundary conditions account for the geometrically non-linear effects. The validity of the model is demonstrated by comparing the resulting displacement fields with those obtained from a moiré inteferometry experiment. The three-dimensional adherend and adhesive stress distributions are calculated and compared with those from a two-dimensional non-linear numerical analysis, Goland and Reissner's solution, and experimental measurements. The nature of the three-dimensional mechanics is described and discussed in detail. It is shown that three-dimensional regions exists in the specimen, where the adherend and adhesive stress distributions in the overlap near (and especially on) the free surface are quite different from those occurring in the interior. It is also shown that the adhesive peel stress is extremely sensitive to this three-dimensional effect, but the adhesive shear is not. It is also observed that the maximum value of the peel stress occurs at the end of the overlap in the central two-dimensional core region, rather than at the corners where the three-dimensional effects are found. The extent of three-dimensional regions is also quantified.
Digital fringe multiplication in three-dimensional photoelasticity
Authors: Chen T Y
Published: July 2007

Digital fringe multiplication of three-dimensional photoelastic images using the image-division technique and multiple-angle relations of the cosine function is described and demonstrated. Fringe multiplication of two slices from a stress-freezing model to a factor of 9 is shown. The fractional fringe orders counted by this method agree well with that determined by the Tardy method and a null-balance compensator. The multiplication process is very simple and effective for practical use.
Neutron strain scanning of a small welded austenitic stainless steel plate
Authors: Webster P J , Mills G , Wang X D , Kang W P , Holden T M
Published: July 2007

Neutron strain scanning has been used to determine the residual stress distribution over the area of the mid-thickness plane of a small austenitic steel piate across which a weld had been laid. The longitudinal and transverse stresses in the centre of the plate and weld are strongly tensile. Stresses normal to the plane of the plate are low everywhere except near the ends of the weld where tensile ‘hot-spots’ are observed. Near the edges of the plate the effects of boundary and balancing conditions are evident. Longitudinal and transverse stresses tend to zero along the edges of the plate to which they are perpendicular but become strongly compressive near the middle regions of the edges to which they are parallel. The results are compared with published data from other welds that were made and constrained differently. The accuracy of the technique is discussed and the results obtained by measuring with different reflections are compared. It is shown that neutron strain scanning is an acceptable, and unique, method for determining non-destructively the residual stress distribution throughout small austenitic steel components with sufficient accuracy to provide data for design purposes and to validate model calculations.
Mixed-mode stress intensity factors in finite, edge-cracked orthotropic plates
Authors: Walker C A , Jamasri
Published: July 2007

A generalized experimental method for measuring mixed-mode stress intensity factors is described for use in orthotropic materials. Moiré interferometry has been used to record the whole field surface displacements of double-edge cracked specimens made from unidirectional laminated composites. The moiré patterns were subsequently used to determine mode I and mode II stress intensity factors ( KI and KII) by utilizing the displacement fields around the crack tip. The equations expressing KI and KII as functions of the displacement fields were reformulated to encompass the orthotropic material constants. A method for deriving these has been described. The accuracy of the results was found to depend on the precision in determining the location of the crack tip, as well as the measurement of the fringe spacing.
Closed-form functions for elastic stress concentration factors in notched bars
Authors: Gray T G F , Tournery F , Spence J , Brennan D
Published: July 2007

The closed-form equations given are based on the results of finite element analyses of double-edge-notched plates subject to tension or in-plane bending. The notch dimensions were varied in a parametric survey from shallow, part-circular forms to deep, sharp, slits with semi-circular ends, giving stress concentration factors varying from 1.2 to 13 (net stress basis).

The concept of a configuration factor for notches, similar to that used to calculate crack-tip stress field intensity factors, is introduced. It is shown in the first instance that the analogous crack configuration factor can be used directly to modify the elastic stress concentration factor for an elliptical hole, giving closed-form functions that do not involve empirical fitting constants and have acceptable practical accuracy. Reasons for the effectiveness of this form are given, together with an analysis of the points where the notch stress concentration factors diverge from the simple closed form. Further refinements that improve accuracy are given and comparisons are also made with stress concentration factors for hyperbolic edge notches.
Morphometrical observations on the mandible of five strains of rabbits and strain identification using mandible measurements
Authors: Goto N. , Watanabe K. , Umezawa H. , Yazawa H. , Kuramasu S.
Published: July 2007

In order to clarify the relationships between five strains of rabbits and to identify the strains, principal component and discriminant analyses were carried out using 12 mandibular measurements of three inbred strains (JW-NIBS/Y (JW/Y), NW-NIBS/Y (NW/Y) and Dutch-NIBS/Y (D/Y)) and two outbred strains (JW-NIBS (JW) and NW-NIBS (NW)) which were maintained at the Nippon Institute for Biological Science. The results obtained were as follows.

(1) Principal component analysis revealed that in the males the mandible of JW was the largest but with considerable variation. D/Y was the smallest of all strains examined. The mandibles of NW and NW/Y were similar to the JW mandibles but had a shape which was shorter and higher. In the females the mandible of NW was the largest of all strains and, as in the males, D/Y was the smallest and JW varied markedly.

(2) Discriminant analysis showed the probability of erroneous discrimination to be 14·8% (34/229) when the inbred and outbred strains were combined. In both sexes erroneous discrimination mostly occurred between NW and NW/Y, which have the same origin, and between JW and NW, which have a common ancestor. However, when the inbreds and outbreds were identified separately by discriminant analysis, the probability of erroneous discrimination was low in both cases (4·5% (5/112) and 7·7% (9/117) respectively). These results indicate that strain differences are found in the size and shape of rabbit mandibles and that mandible analysis is effective for strain identification of laboratory rabbits.
Age-related non-neoplastic lesions in the heart and kidneys of Syrian hamsters of the APA strain
Authors: Doi K. , Yamamoto T. , Isegawa N. , Doi C. , Mitsuoka T.
Published: July 2007

Spontaneous cardiac and renal lesions in APA hamsters were examined histopathologically. Myocardial degeneration, valvular thickening, coronary arterial degeneration and increase in heart weight were common in old hamsters. These changes, which suggest cardiac failure, seem to be related to cardiac thrombosis which predominantly affected the left atrium and was found in over 40% of each sex over 16 months of age. Neither glomerular amyloidosis nor arteriolar nephrosclerosis was detected. In general the histopathology of renal lesions in APA hamsters resembled that of the condition known as glomerulonephrosis in rats. Renal lesions occurred more frequently and more severely and developed more rapidly in females than in males. There was no apparent correlation between cardiac thrombosis and renal disease.
The effect of neuroleptanalgesia on some cardiorespiratory variables in the rabbit
Authors: Guerreiro D. , Page C. P.
Published: July 2007

A technique of neuroleptanalgesia during which rabbits breathed spontaneously for as long as 6 h without any outward sign of stress and with full recovery within 12 h is described. The method involved the constant infusion of a solution comprising fentanyl (0·05 mg/ml) and droperidol (0·13 mg/ml) in 5% dextrose following an intramuscular dose of fentanyl and droperidol. Hourly measurements of blood gases, lung mechanics, mean arterial blood pressure and heart rate were made to assess changes in ventilation and in these physiological parameters for the length of the study. The animals' tracheas were intubated under direct vision with an uncuffed tube. The animals breathed spontaneously and their cardiovascular and respiratory systems were stable throughout the entire monitoring period. There was no statistical difference between the values for all the parameters measured ( P < 0·1). A two-way analysis of variance statistical test was applied to all the measurements.
A simple technique for endotracheal intubation in rabbits
Authors: Fick T. E. , Schalm S. W.
Published: July 2007

A technique for endotracheal intubation in rabbits, which eliminates the need for tracheostomies, special devices, laryngoscopes and guide wires, is described. Inhalation anaesthesia with controlled ventilation for major surgical procedures in rabbits is easier to perform than previous reports in the literature suggest.