bluuebunny/crossref_metadata_2025 huggingface dataset:
Homogenized and relocalized mechanical fields
Authors: Kruch S
Published: July 2007

Usually the homogenization process used to determine the macroscopic mechanical fields from knowledge of the microscale geometry and the corresponding local fields is based on the development of localization (sometimes also called concentration) relations. The aim of this paper is to deal with the application of such relations in an opposite way, to deduce the local fields from the macroscopic ones, and their improvement when some basic hypotheses of the homogenization technique are no longer valid.
A dual-time-scale finite element model for simulating cyclic deformation of polycrystalline alloys
Authors: Manchiraju S , Asai M , Ghosh S
Published: July 2007

A dual-time-scale finite element model is developed in this paper for simulating cyclic deformation in polycrystalline alloys. The material is characterized by crystal plasticity constitutive relations. The finite element formulation of the initial boundary-value problems with cyclic loading involves decoupling the governing equations into two sets of problems corresponding to two different time-scales. One is a long-time-scale (low-frequency) problem characterizing a cycle-averaged solution, while the other is a short-time-scale (high-frequency) problem for a remaining oscillatory portion. Cyclic averaging together with asymptotic expansion of the variables in the time domain forms the basis of the multitime-scaling. The crystal plasticity equations at the two scales are used to study cyclic deformation of a titanium alloy Ti-6Al. This model is intended to study the fatigue response of a material by simulating a large number of cycles to initiation.
Orthotropic curved plates: Symbolic solution for in-plane actions and examples of collinear compression
Authors: Pavlović M N , Tahan N , Kotsovos M. D
Published: July 2007

Recent work on isotropic curved sector plates provided an exact solution that could be used both as a benchmark for numerical methods and as an efficient tool for quick and economical parametric studies. Its present extension to the case of cylindrical orthotrophy shows that similar ‘closed-form’ solutions require the formal consideration of four possible regimes and these are fully listed. Although the first of these is likely to be of main practical interest, any of the remaining three cases might become relevant in special instances of orthotrophy combined with specific term numbers in the Fourier series solutions on which the method is based. Illustrative examples are given by reference to the problem of collinear compression.
Torsion stiffness of a rubber bushing: A simple engineering design formula including the amplitude dependence
Authors: García Tárrago M J , Kari L , Viñolas J , Gil-Negrete N
Published: July 2007

An engineering design formula for the torsion stiffness of a filled rubber bushing in the frequency domain, including the amplitude dependence, is presented. It is developed by applying a novel separable elastic, viscoelastic, and friction material model to an equivalent strain of the strain state inside the bushing, thus leading to an equivalent shear modulus that is inserted into an analytical formula for the torsion stiffness. The rubber model is the result of extending the force-displacement relation established in a sound rubber component model to the stress-strain level. Unlike other simplified methods, this procedure takes into account the variation in the properties inside the bushing owing to non-homogeneous strain states. Moreover, as this formula depends on the bushing geometry in addition to the material properties, it is a fast engineering tool to design the most suitable rubber bushing to fulfil user requirements. Furthermore, it is shown - by dividing the considered bushing into several slices, consequently each equivalent shear modulus is closer to the true value - that the approach of working with only one equivalent shear modulus for the whole bushing is accurate enough.
Stresses in torispherical drumheads: A critical evaluation
Authors: Fessler H , Stanley P
Published: July 2007

An empirical equation is used to compare the results of the authors' extensive photoelastic study with stress concentration factors and other forms of head shape factor obtained from independent experimental and analytical work and from some codes of practice.

Important differences are shown between the stress distributions in a number of shallow, thin models and a prototype and some analytical solutions.

The variations of elastic stress concentration factor with wall thickness and with knuckle radius obtained from the photoelastic work are compared with other versions.

The simplifications implicit in the recommendations of codes of practice are outlined and some recommendations are made for further work.
An investigation of the fatigue life of typical aircraft gas turbine compressor discs
Authors: Owen M. J. , Dudley B. R.
Published: July 2007

The numerous discs which are incorporated in gas turbine rotors are subjected to high level stresses at full engine speed. Each time the engine is operated and run up to maximum speed one cycle of stress is applied to each disc. In the course of time there exists the possibility of a fatigue failure. The life of a component cannot be predicted accurately from the properties of laboratory specimens of the material because of the more complicated stress pattern and the number of manufacturing variables which affect the fatigue properties.

A special testing machine was built to subject compressor discs to cyclic loading at the blade fastenings whilst the disc remained stationary. Stress distributions for a typical disc were calculated for rotating and non-rotating conditions. Strain gauges were used to measure the stresses under the non-rotating conditions of the testing machine. Comparisons of theoretical and experimental results were made. It was concluded that by applying loads of sufficient magnitude at the rim it was possible to produce stresses at the bore of the same magnitude as those produced under rotating conditions and that the method of loading produced a reasonable simulation of the stress distribution in the central part of the disc. Under non-rotating conditions with these high loads the tangential stresses in the outer part of the disc were about 30 per cent higher and the radial stresses about 60 per cent higher than under rotating conditions.

It was found necessary to make modifications to the discs for the fatigue tests. When loaded through the standard pinhole blade fastening, the discs failed from the pinholes because of the increased nominal stress in the rim and the high local load. By cutting off most of the rim and using grips instead of the standard pin fastening it was possible to obtain failures in the diaphragm of the discs. Although the individual discs failed in different modes with fractures arising from several sources the lives of all the discs tested lay between 34 000 and 130 000 cycles. These lives were satisfactory compared with service requirements. Typical aircraft engines accumulate from 1000 to 4000 flight cycles per year according to service conditions.
Radial pressure exerted by piston rings
Authors: Bin Chik Ahmad. , Fessler H
Published: July 2007

The local pressures exerted by 15 in diameter rings closed to a circular shape by 36 point loads were measured with strain gauges. Departures from the theoretical open shape and from a circle when closed by tangential end forces, which simulated uniform pressure, did not predict the variations in local pressure. Double integration of pressures around the rings led to the open shape defects of the same order of magnitude as the measured values.

Variations in local pressure exerted by actual piston rings can only be determined by direct, multipoint measurement.
Plane strain bending with work hardening
Authors: Denton A. A.
Published: July 2007

Possible approaches to an analytical solution to the plane strain bending of a work hardening material are discussed. It is shown that the bending stress (δ x) and strain ε x) can be expressed independently in terms of the current yield stress and increment, but that further progress to the function δ x = ε x) is impeded by the implicity of the separate functions for δ x andε x. The solution is completed by a numerical method and used to determine the stress and strain paths in a wide copper plate subjected to bending. A geometrical method is also shown to exist, but is discarded because of the necessity for an iterative determination of the stress and strain increments.
Parallelogrammic elements in the solution of rhombic cantilever plate problems
Authors: Dawe D. J.
Published: July 2007

The finite element method is applied to the calculation of the deflection under a uniformly distributed load and the natural frequencies of the rhombic cantilever plate. This has required the derivation of stiffness and inertia matrices for a plate element of parallelogrammic planform.

Although, in common with the work of past investigators, the accuracy of the results decreases with increase in skew angle it is shown that the method is adequate for angles up to about 45°.
Compressive behaviour of thin layered thermally insulating structural supports
Authors: Probert S D , Jones M C
Published: July 2007

Stacks, each consisting of a large number of thin layers of the same material, were compressed under loads of up to 5 × 103 lbf. Within experimental error, the compression c per stack layer is independent of the number of layers but varies as a power m of the layer thickness: m equals 0.48 for freshly assembled stacks of flat brass discs. Changes of c upon increasing the applied load W from 5 × 102 to 103 lbf are of the order of the centre line average values of the surfaces in contact. For loads greater than 8 × 102 lbf the effective moduli exceed 105 lbf in−2, increase with W and load cycling, and are within two orders of magnitude of the bulk elastic moduli. Considerable hysteresis occurs in the first load-unload cycle, but further irreversibility rapidly decreases in subsequent cycles provided W is never reduced below 50 lbf. The W-c curves for freshly assembled stacks of flat layers are approximately exponential: changes in slope of the graph of log W against c suggest that asperity deformation processes predominate at high loads (> 5.5 × 102 lbf) and layer flattening at low loads (<2.5×102 lbf). A stack possessing lateral as well as compressive strength is described in Appendix 1: this design has been adopted for a mechanically strong thermal insulator.
In-plane bending of a large 90° smooth bend
Authors: Findlay G E , Spence J
Published: July 2007

An experimental investigation has been conducted on a 6 ft 6 in diameter 90° smooth bend which forms part of the outlet ducting of Number 2 reactor vessel at Sizewell nuclear power station. The results of the investigation show excellent agreement with various available theories, both for stresses and flexibility factors. The theories themselves are discussed and it is concluded that the asymptotic solution of Clark and Reissner, largely neglected in this country, has distinct advantages in many cases, being relatively simple to use and giving comparable results with other theories which require extensive computation.
Elastic-plastic strain distributions in short-link chain under load
Authors: Hawkes I , Foley J H
Published: July 2007

The strain distribution in short-link chain under load has been examined by a photoelastic-coating technique. It has been shown that at loads up to and just beyond the elastic limit the position of maximum strain occurs at a junction of an intrados and a straight side of the link. Beyond the elastic limit, however, changes in link geometry cause the position of maximum strain to move to the link crown.

These results confirm observations of the positions of the fractures in fatigue and static tensile tests to failure but the stress concentration factors calculated from the results disagree with theoretical predictions. This anomaly is explained by assuming that the area of contact between adjacent links effects a spreading of the load, whereas the theoretical treatment assumes point contact between adjacent links.
Calculation of the strain-energy release rates of cracked plates by an approximate method
Authors: Williams J G , Isherwood D P
Published: July 2007

A method for the approximate calculation of strain-energy release rates for finite plates is proposed in terms of a mean stress. Solutions are compared with those cases for which analytical and numerical solutions exist and good agreement is obtained. The method is then applied to the general case of a plate with unequal cracks and a non-axial load and to a finite rotating disc with a central hole.
Dynamic-relaxation solutions of elastic-plate problems
Authors: Rushton K R
Published: July 2007

The analysis of the static deformation of elastic plates is achieved by studying the dynamic problem of the damped oscillation of the plate and arranging that the oscillations are rapidly reduced to zero by a suitable choice of the damping factor. This damped-wave equation, when written in an explicit finite-difference form, can readily be solved on a digital computer. The computer programme has been designed to determine automatically the critical damping factor for a rectangular plate carrying any load distribution and with any combination of edge conditions. The extension of the method to include elastic foundations is also described.
Computation of finite strains from moire displacement patterns
Authors: Bossaert W , Dechaene R , Vinckier A
Published: July 2007

A new and accurate method is described for deriving finite strains from moiré displacement patterns.

The components u and v of the displacements at the mesh points of a Lagrangian co-ordinate network are estimated from the moiré fringes. In the neighbourhood of a point, where the strains are to be calculated, two algebraic functions are determined, approximating as closely as possible to the two sets of estimated u and v values. The strains are then calculated from the partial derivatives of these two functions. The procedure is repeated for all points at which the strains are required.

When this procedure is applied to a great number of points the use of a computer becomes a practical necessity. Once the formulae have been programmed, the operator has only to estimate the u and v values at the mesh points of the co-ordinate network and to feed this set of numbers to the computer. This new method thus allows a considerable gain in time and brings about an improvement in accuracy compared with other methods.
The collection of photoelastic data
Authors: Fessler H
Published: July 2007

Necessary conditions for reliable direct loading and frozen-stress tests are stated. Efficiency of operation of transmission polariscopes is discussed and instruments which incorporate desirable features are described. The types of measurement which may be required are analysed and the necessary procedures for stress determinations and calibrations are discussed.
Effect of multiaxial stresses on the fracture strength of silicon carbide
Authors: Priddle E K
Published: July 2007

This work describes the fracture behaviour of silicon-carbide tubular specimens under multi-axial stresses at room temperature. A method of obtaining combinations of stresses in the form of torsion, hoop, axial tension, and compression is described and failure envelopes for silicon carbide are included from the data obtained.

Failure theories are reviewed and the results from the work show that the available theories are inadequate to describe both the tension-tension and tension-compression quadrants.

For practical purposes a straight-line relation can be used joining axial and hoop tensile strengths and the axial compression strength.
In-plane bending of single, unreinforced mitred pipe bends
Authors: Kitching R , Thompson W J
Published: July 2007

Measurements of strain, transverse deflection, and change of radius have been taken on single unreinforced pipe bends subjected to in-plane bending moments. Specimens having three different mitre angles for each of two sizes of pipe have been used. Observations were made with different combinations of leg lengths for each specimen.

Stresses and flexibilities are compared with those calculated by the formulae given in the A.S.A. Piping Code B.31.1 and the concept of equivalent smooth bend is examined. Alternative methods of assessment are considered and improved methods are suggested.
Finite-element stress analysis of a non-linear problem: A connecting-road eye loaded by means of a pin
Authors: White D J , Enderby L R
Published: July 2007

The stress analysis of a connecting rod under a tensile load represents a non-linear problem, since the distribution of the forces, acting between the eye of the rod and the pin, changes as the loading proceeds. This is due to the tendency of the eye to deform, thus wrapping itself around the pin as the clearance between the parts is reduced. In consequence, the stress pattern in the eye also changes.

Such a problem has been solved with a linear elastic finite-element computer programme. A connecting-rod eye was idealized as a plane-stress problem and special elements were introduced to connect the pin and rod together. These elements were assigned stiffnesses which were changed in a prescribed manner after each iteration until compatibility of forces and displacements, with due allowance for initial clearances, was obtained at each connecting point.

Although eight iterations were required to achieve the correct displacements, it was found that the circumferential stresses did not change appreciably after the first few iterations. Good agreement was found between the calculated stresses and those measured in a laboratory test with electrical-resistance strain gauges.
Thermal self-straining of fibre-reinforced materials
Authors: Asamoah N K , Wood W G
Published: July 2007

The mechanics of thermal self-straining in fibre-reinforced materials are explained. Stress distributions obtained from finite-element calculations are compared with results from photothermoelastic analysis of models.
Deflection of uniformly loaded circular plates upon equispaced point supports
Authors: Vaughan Henry
Published: July 2007

A simple formula is derived for predicting the flexure of uniformly loaded point-supported circular plates. The classical solution of Michell for a clamped plate under a single point load is extended for any number of point loads regularly spaced around a circle concentric with the plate edge. The resulting series for the edge moments and shears are summed and are shown to be very similar to a simple sine wave. Replacing the exact expressions by single sine waves enables the clamped edges to be set free by a simple superposition of solutions. The point reactions are equilibrated by a uniform load and the resulting deflection surface for a free uniformly loaded point-supported plate is obtained immediately. Deflection curves for the particular case of a plate supported at three points are given in the form of contours of equal deflection. This particular case is compared with some experimental results which were obtained by optical methods.

For three supports, maximum deviation from the flat is least when the supports are equispaced around a circle of radius approximately two-thirds that of the plate. The contours for this case show that the central area is remarkably flat and that there are three diameters along which the deflections are almost constant.
Application of large-deflection theory to normally loaded rectangular plates with clamped edges
Authors: Scholes A
Published: July 2007

A previous paper (1)∗described an analysis for plates that made use of non-linear large-deflection theory. The results of the analysis were compared with measurements of deflections and stresses in simply supported rectangular plates.

In this paper the analysis has been used to calculate the stresses and deflections for clamped-edge plates and these have been compared with measurements made on plates of various aspect ratios. Good agreement has been obtained for the maximum values of these stresses and deflections.

These maximum values have been plotted in such a form as to be easily usable by the designer of pressure-loaded clamped-edge rectangular plates.
Hydrostatic bulging of circular diaphragms
Authors: Chakrabarty J , Alexander J M
Published: July 2007

Tresca's yield criterion and the associated flow rule have been used to develop a solution for the plastic bulging of circular diaphragms by lateral fluid pressure. The strain distribution in the neighbourhood of the pole is derived in explicit form and a new formula is given for the polar strain at instability. The theory is found to be in good agreement with experimental results for the bulge test. A numerical method of solving the problem for Mises materials is also proposed.
An investigation of photoresists for use in optical strain analysis
Authors: Luxmoore A , Hermann R
Published: July 2007

Some commercial photoresists have been examined to assess their suitability for use with the moiré method of surface-strain measurement. As most of these materials do not produce a pattern of high contrast directly, some etching and plating procedures are also described. Combined with correct illumination, these processes will produce grids of sufficient contrast for most applications.
Cyclic behaviour of materials
Authors: Miller K J
Published: July 2007

The effect of strain rate on the cyclic behaviour of two materials is presented. For the material that cyclically hardens (En 32B) a decrease in strain rate decreases the maximum cyclic hardening of the material, whilst for a material that cyclically softens (En 25) a decrease in the rate of deformation increases the maximum cyclic softening. It is concluded that the effect of strain rate on the cyclic stress-strain curve should be more closely studied than the effect of frequency since the frequency may be constant whilst the straining rate may vary considerably in plastically deformed zones. For those zones that suffer low strain rates the inclusion of time-dependent deformation processes can maximize the degree of softening or minimize the degree of hardening, thereby creating a greater localization of the plastic strain which should increase strain-concentration factors. Finally it is argued that it is better to predict fatigue behaviour from an incremental-step high-strain fatigue test on a single specimen than from static-test data. For the same reasons correlations between static tests and fatigue tests should be discouraged, especially for those materials that exhibit marked cyclic softening.
Fatigue-life prediction under irregular stress conditions
Authors: Erismann T H
Published: July 2007

The present work is a shorter version of a more detailed treatise by the author (1)∗. The method consists of two parts: the empirical determination of certain characteristics of a material by means of a relatively small number of well defined standard tests, and the arithmetical application of the results obtained to arbitrary loading histories. The following groups of parameters are thus taken into account: the variations of the mean stress; the interaction of these variations and the superposed oscillating stresses; the spectrum of the oscillating-stress amplitudes; the sequence of the oscillating-stress amplitudes.
Plane-stress analysis of rubber at high strains using finite elements
Authors: Lindley P B
Published: July 2007

A finite-element programme has been developed for the analysis of stretched rubber sheets. The elastic energy of each of the homogeneously deformed triangular elements into which the sheet is divided can be determined from the displacements of its nodal points and a suitable strain-energy function. Each nodal point of the sheet is considered in turn and moved to a position which minimizes the energy of all the elements local to it. This iterative process is continued until the total energy of the sheet is minimized. A modified classical-elasticity-theory programme provides the first approximation. The boundary conditions are specified displacements, assumed to arise from the use of rigid clamps. The results are in good agreement with experiment for peak strains of about 150 per cent. Computation time on a CDC 6600 computer is about 0.005 × (nodal points)2 seconds.
Cyclic stress-strain relations from bending and push-pull tests
Authors: White D J , Horwood G P
Published: July 2007

Cyclic plastic-straining tests have been conducted in push-pull on cylindrical specimens and in uniform bending on rectangular-section bars of mild steel (B.S. 1501–161 Grade 28A) and of stainless steel (En 58J). The mild-steel specimens were tested at room temperature and 350°C, the stainless-steel specimens at room temperature and 650°C. It is found that there is good correspondence between cyclic stress-strain relations (the cyclic semi-range of strain and the corresponding cyclic semi-range of stress) derived from bending tests, when an expression analogous to that developed by Nadai for monotonic straining is used, and those obtained more directly from push-pull tests.
Solution of axisymmetric torsion problems by point matching
Authors: Matthews G J , Hooke C J
Published: July 2007

A general numerical technique is presented for the solution of the problem of torsion of axisymmetric bodies. The method superimposes a number of basic solutions of the elasticity equations using the point-matching technique so as to satisfy approximately the prescribed boundary conditions of a body. Results obtained by this technique are compared with those obtained by alternative experimental and theoretical techniques for various body geometries to assess the accuracy of the method. The technique is then applied to the problem of the torsion of shouldered shafts since large discrepancies exist between the experimental and analytical results available for this type of structure.
Effect of torsional prestrain on the yield locus of 1100-F aluminium
Authors: Williams J F , Svenssoon N L
Published: July 2007

A series of combined stress tests in torsion-tension space is carried out on thin-walled tubes of 1100-F commercially pure aluminium, prestrained to a maximum level of 10 per cent torsional plastic strain. The results are analysed in terms of a proposed, rationally based, yield criterion constructed on statistical reasoning. It is shown that during prestrain, the yield loci undergo a significant degree of distortion, accompanied by a flattening of part of the locus opposite to the loading point.

It is found that the yield locus does not rotate under prestrain and, contrary to the findings for tensile prestrain, little evidence of the development of corners at the loading point is observed. The proposed criterion is shown to provide a good fit to the experimental results.
Point-loaded discs and blocks applicable to tensile testing of brittle materials
Authors: Appl F J
Published: July 2007

A method of numerically approximating the solutions of plane-stress or plane-strain elasticity problems with boundary conditions consisting of concentrated forces or distributed loads is presented herein. The effect of each concentrated force (commonly termed a point load) that acts on the boundary is represented by a Flamant solution. Usually, the combined effect of these Flamant solutions indicates the presence of distributed loadings or ‘residual stresses’ on some portions of the boundary that are not consistent with the actual boundary conditions. The negatives of these ‘residual stresses’ are used as stress boundary conditions in a singular integral method of numerical analysis that is applicable to plane elasticity problems involving distributed loadings on the boundaries. Since the method presented herein involves only stress boundary conditions, the solutions are valid for both plane stress and plane strain.

The accuracy of this superposition method is demonstrated by consideration of a circular disc or cylinder subjected to diametrically opposed concentrated forces for which accuracy to within 0.2 per cent of the exact solution is obtained. Parametric analyses of rectangular and elliptical compression members subjected to point loads are presented. Results determined herein are found to compare relatively well with those determined in previous numerical and experimental investigations of specific cases. These results make possible the design and analysis of compression members used to evaluate the tensile fracture strength of brittle materials.
Use of microstructure for visioplasticity analysis
Authors: Medrano R E , Gillis P P , Hinesley C P , Conrad H
Published: July 2007

It is often suggested that splitting a specimen and machining grid lines on one of the exposed planes to study flow patterns during plastic deformation interferes with the flow process under investigation. A procedure is described here for flow-function analysis of extrusion specimens in which artificial grid lines are not required. The procedure is restricted to situations in which the microstructure exhibits line segments produced by deforming grains or second-phase particles as they flow through the die. These segments represent partial-flow lines according to the assumptions of flow-function analysis. From numerical analysis of their slopes it is possible to construct the complete flow function. From this, all the kinematic quantities of the deformation can be determined.
Analysis of stresses in a limpet-coil pressure vessel due to pressure in the coil
Authors: Kitching R , Better H H
Published: July 2007

A theoretical analysis was carried out to determine the distribution of stresses and radial deflections due to internal pressure in the limpet of a limpet-coil pressure vessel. A computer programme was developed to carry out the complete calculations. Theoretical results for a vessel having the dimensions of a test vessel were compared with the corresponding experimental values obtained from strain-gauge and deflection-gauge measurements on the test vessel itself.
Complete experimental solution of three-dimensional elastic problems
Authors: Durelli A J
Published: July 2007

The mechanical and optical properties of a transparent epoxy are described, the response of which can be ‘locked-in’ at a critical temperature. The Poisson's ratio of this material is about 0.4, which is closer to the Poisson's ratio of common engineering materials than is that of the commonly used epoxies. Since the material is compressible, strain measurements on relaxed slices permit the complete determination of the stress field. Examples of applications to a solid and hollow sphere and to a tube, subjected to diametral compression, are given. The method permits the solution of three-dimensional problems by use of (1) photoelastic data only, (2) the moiré method only, or (3) mechanically obtained data only, or different combinations of them.
Type 2 energy and bound analyses for the creep of smooth circular pipe bends under combined in-plane bending and internal pressure
Authors: Spence J
Published: July 2007

Using an energy method designated type 2, an approximate analysis is outlined for the stationary creep of a smooth circular cross-section constant thickness thin-walled pipe bend subject to combined internal pressure and in-plane bending. The analysis complements, but is independent of, the previous type 1 energy analysis. A simple n-power creep law is assumed relevant and direct optimization techniques are employed. Both analyses then prove useful in bounding techniques which allow the creep deformation rate to be bounded from above and below. Results are presented and discussed against the background of the type 1 work and, together, the analyses help to provide some confidence in predicting the bend behaviour in creep under combined loading. Some aspects of the type 2 theory are less satisfactory than the type 1 analysis but the outcome is simpler and, at the straight pipe end of the geometry range, the type 2 results are better.
Comparisons between mechanical analogue and experimental measurements for thermal stresses in two dimensions
Authors: Sekiya T , Sumi S , Okamoto M
Published: July 2007

This paper confirms results for plane thermoelastic problems obtained by a mechanical analogue procedure. The temperature distribution is caused by heating and cooling. The distributions of thermal stress obtained for this temperature field are compared with earlier results obtained by mechanical analogue.
Stresses around a small circular cutout in a cylindrical shell subjected to asymmetric bending
Authors: Pattabiraman J , Ramamurti V
Published: July 2007

The problem of stress concentration around cutouts in shells is an important one in the design of nuclear pressure vessels, boilers, pressure hulls of submarines, aircraft structures, pipe connections and tube and ball mills used in chemical industries. By using the finite-difference scheme suggested by Budiansky, the solution to the problem of a cylindrical shell without a cutout, subjected to an asymmetric load, is derived first. Then, the negatives of the stress resultants and stress couples at a given radius obtained from the above solution are combined with a transverse shear force to form the edge conditions for a circular cylindrical shell containing a circular cutout of radius a. The desired results are finally obtained by superposing these two solutions.
Stress analysis of axisymmetric butt joints loaded in torsion and tension
Authors: Adams R D , Coppendale J , Peppiatt N A
Published: July 2007

Axisymmetric butt joints are widely used as specimens for testing the response of adhesives to shear and tensile stresses. When analysing the results from these tests, the stress distributions must be accurately known. A finite-element analysis has been used to examine the effect of non-rigid adherends and a spew fillet in solid and annular butt joints for a range of geometries and adhesive properties. It has been shown that stress concentrations occur in butt joints loaded in tension; in the latter case, the stress concentration is directly due to the presence of the spew fillet.
A note on the yielding of an accelerating, non-homogeneous disc of varying thickness and density with radial loading
Authors: Gurushankar G V
Published: July 2007

The influences of non-homogeneity and density on the normal stresses and shear stresses developed due to the acceleration of a disc, of varying thickness, at any particular instant, are analysed. Yield loci, on the basis of von Mises' criterion, are found for discs of varying thickness and uniform thickness with a bore ratio ( a/ b) of 0.25 and also for linearly varying ( p = 1.0, q = 1.0) and nonlinearly varying ( p = 0.5, q = 0.5) density and homogeneity. A homogeneous, uniform density and uniform thickness disc forms a special case of the analysis.
Crack-opening displacement as a method of measuring crack length in compact-tension specimens
Authors: Ponton J W , Lee G M C
Published: July 2007

A pseudo-compliance method is discussed as a means of measuring fatigue crack lengths in BS 5447, ASTM E399.72 compact-tension specimens. A calibration curve for these specimens is obtained together with a relationship between pseudo-compliance and K, the stress intensity factor. This method is suitable for automatic crack monitoring and load control.
Flexural failure analysis of angle-ply laminates of gfrp and cfrp
Authors: Turvey G J
Published: July 2007

An exact solution of the strip equilibrium equations is combined with the Tsai-Hill failure criterion to facilitate an initial flexural failure analysis of uniformly-loaded, antisymmetrically-laminated, GFRP and CFRP angle-ply strips. Dimensionless, initial-failure data (that is, failure loads and their associated strip centre-line deflections) are presented for the practical range of fibre orientations, 15° ≤|θ| ≤ 75°, in strips comprising up to ten laminae.
Strain rate sensitivity of a mild steel at room temperature and strain rates of up to 105s−1
Authors: Hashmi M S J
Published: July 2007

Experimental results on a mild steel are reported from ballistics tests which gave rise to strain rates of up to 105 s−1. A finite-difference numerical technique which incorporates material inertia, elastic-strain hardening and strain-rate sensitivity is used to establish the strain-rate sensitivity constants p and D in the equation, σ4 = σ1 (1+(∊/D)1/ p). The rate sensitivity established in this study is compared with those reported by other researchers.
Very thin torispherical pressure vessel ends under internal pressure: Test procedure and typical results
Authors: Stanley P , Campbell T D
Published: July 2007

Very thin cylindrical pressure vessels with torispherical end-closures have been tested under internal pressure until buckles developed in the knuckles of the ends. These were prototype vessels in an austenitic stainless steel. The preparation of the ends and the closed test vessels is outlined, and the instrumentation, test installation, and test procedure are described. Results are given and discussed for three typical ends (diameters 54, 81, and 108in.; thickness to diameter ratios 0.00237, 0.00158, and 0.00119). These include measured thickness and curvature distributions, strain data and the derived elastic stress indices, and pole deflection measurements. Some details of the observed time-dependent plasticity (or ‘cold creep’) are given. Details of two types of buckle that developed eventually in the vessel ends are also reported.
Measurement of residual stresses by neutron diffraction
Authors: Stacey A , MacGillivary H J , Webster G A , Webster P J , Ziebeck K R A
Published: July 2007

A neutron diffraction method has been applied to measure residual stresses in rings sliced from as-recieved and autofrettaged thick-walled steel tubing. The principles of neutron diffraction are outlined and the method is described. A comparison is made with results obtained using the more traditional Sachs boring technique. It is shown that satisfactory agreement is achieved between the two procedures and that the neutron diffraction method can be used with acceptable accuracy to measure residual stress non-destructively in bulk samples of steel several centimetres thick.
Buckling of shallow torispherical domes subjected to external pressure — a comparison of experiment, theory, and design codes
Authors: Galletly G D , Kruzelecki J , Moffat D G , Warrington B
Published: July 2007

The test results obtained on 24 externally-pressurised torispherical steel shells are given in this paper. The knuckle radius-to-diameter ratio of the domes varied from 0.06 to 0.18 and the spherical cap radius-to-thickness ratios were between 75 and 335. Initial shape and thickness measurements were carried out on all the torispheres and a summary of this information is given. The BOSOR 5 shell buckling program was employed to predict the buckling/collapse pressures of all the domes; both perfect domes and those with axisymmetric imperfections were considered. The correlation between the theoretical predictions and the experimental results was, in general, very good.

The main conclusions of the present investigation are: (i) that some of the experimental buckling pressures were lower than those obtained by multiplying the BS 5500 design values by a safety factor of 1.5, and (ii) that those torispheres with sharp knuckle radii failed by plastic collapse in the knuckle region and the collapse pressures were not very sensitive to initial geometric imperfections. It thus appears that the BS 5500 rules relating to the strength of shallow torispheres subjected to external pressure need to be amended, and that the tolerances on geometric shape for cases which are likely to be imperfection-insensitive should be reconsidered.
Clamped torispherical shells under external pressure — some new results
Authors: Blachut J , Galletly G D
Published: July 2007

Perfect clamped torispherical shells subjected to external pressure are analysed in the paper using the BOSOR 5 shell buckling program. Various values of the knuckle radius-to-diameter ratio ( r/D) and the spherical cap radius-to-thickness ratio ( Rs/ t) were studied, as well as four values of σyp, the yield point of the material. Buckling/collapse pressures, modes of failure and the development of plastic zones in the shell wall were determined. A simple diagram is presented which enables the failure mode in these shells to be predicted. The collapse pressures, pc, were also plotted against the parameter Λs (√( pyp/ pcr)). When the controlling failure mode was axisymmetric yielding in the knuckle, the collapse pressure curves depended on the value of σyp, which is unusual. However, when the controlling failure mode was bifurcation buckling (at the crown/knuckle junction), the collapse pressure curves for the various values of σyp all merged, i.e., they were independent of σyp. This latter situation is the one which normally occurs with the buckling of cylindrical and hemispherical shells.

A limited investigation was also made into the effects of axisymmetric initial geometric imperfections on the strength of externally-pressurised torispherical shells. When the failure mode was axisymmetric yielding in the knuckle, initial imperfections of moderate size did not affect the collapse pressures. In the cases where bifurcation buckling at the crown/knuckle junction occurred, small initial geometric imperfections at the apex did not affect the buckling pressure, but axisymmetric imperfections at the buckle location did influence it. With the other failure mode (i.e., axisymmetric yielding collapse at the crown of the shell), initial geometric imperfections caused a reduction in the torisphere's strength.
A study of the diffusion analogy technique for the photoelastic determination of transient thermal stresses
Authors: Stanley P , Yip Y J
Published: July 2007

The formal similarity between the equation governing the diffusion of a substance through a “porous” isotropic material and the heat conduction equation for the temperature distribution in an isotropic homogeneous solid is examined, and its use as a basis for the photoelastic study of transient thermal stresses is explored.
Design of sheathed spiral strands against free bending fatigue at terminations
Authors: Raoof M
Published: July 2007

Significant shortcomings of the previously available approaches for designing steel cables against free beinding fatigue at nominally fixed terminations are briefly discussed. The salient features of a more appropriate design approach based on the ‘contact stress-slip’ parameter are presented. Unlike traditional approaches, this approach takes the effect of interwire/interlayer fretting fully into account. In view of the lengthy theoretical formulations for the previously reported contact stress-slip approach, the present paper covers in detail the development of a set of straightforward design formulations which are based on an extensive series of theoretical parametric studies. The parametric studies cover the full practical range of cable (and wire) diameters and lay angles in sealed spiral strands under external hydrostatic pressure due to depths of water, h, in the range 0 ≤ h ≤ 1500 m. The proposed design formulations are all amenable to hand calculations and should prove valuable to design engineers. A numerical example is provided to facilitate the use of the new design formulations.
Stress concentrations at an oblique hole in a thick flat plate under an arbitrary in-plane biaxial loading
Authors: Stanley P , Day B J
Published: July 2007

The results of an extensive ‘frozen-stress’ photoelastic investigation of the stresses at isolated oblique holes in thick wide plates subjected to uniform uniaxial tension are used to provide stress concentration factors at holes resulting from any form of biaxial in-plane loading. The work covers plate thickness/hole diameter ratios from 1.3 to 3.0 and hole obliquity angles up to 60 degrees. Over these ranges the effects of changes in the plate thickness/hole diameter ratio are not of major importance but the effects of changes in the angle of obliquity are considerable.
Response of AL 7050—T7451 to complex load spectra
Authors: He D T , Williams J F , Ibrahim R , Rees D , Jones R
Published: July 2007

The Ramaswamy-Stouffer—Laflen constitutive model (1) has recently been extended (2) to account for the inelastic response of 7050—T7451 aluminium alloy. This paper presents the results of a combined analytical and experimental investigation into the ability of this model to predict the inelastic response to complex load spectra.
Prediction of settled cyclic behaviour of metals using first cycle data and combined hardening laws for reversed plasticity
Authors: Oloyede V O A , Turner C E
Published: July 2007

This paper presents a generalized concept of combined hardening which is examined by experimental and computational methods. A ‘kinematic displacement parameter’, β, relating the movement of the yield function surface to the Bauschinger effect, is defined in terms of its dependence on material properties and loading state. Experimental relations between β and the plastic strain, εp, are prsented for three metals. The monotonic stress-strain and β data are used in a finite element program to show that settled cyclic hysteresis loops are soon established. Settled cyclic stress-strain curves computed in this way are in good agreement with the experimental results for an aluminium alloy, a stainless steel that shows cyclic hardening, and a titanium alloy that shows little cyclic effect.
The influence of orientation on the elastic and low cycle fatigue properties of several single crystal nickel base superalloys
Authors: Li S X , Ellison E G , Smith D J
Published: July 2007

Experimental studies on the influences of orientation on the elastic behaviour at 20°C and 950°C and the low cycle fatigue creep properties at 950°C of the single crystal nickel base superalloy SRR99 are described. The elastic response at 20°C is found to be in good agreement with predictions from the properties of pure nickel. At 950°C the orientation dependence is shown to be well correlated with a simple orientation function, which is also found to be insensitive to temperature. Similar correlations are shown for the single crystal nickel base superalloys PWA1480 and RENE N4 at high temperatures.

The low cycle fatigue properties for fully reversed strain controlled cycles of SRR99 are shown to be strongly dependent on crystal orientation. Similar results from earlier work for RENE N4 are also illustrated. It is shown that by modifying the applied total strain range to take into account the influence of orientation for elastic deformation, essentially orientation-independent low fatigue cycle curves for SRR99 and RENE N4 are obtained.
Residual stress investigations on a hot-rolled plane sandwich-type composite X5 Cr Ni 18 9-C45-X5 Cr Ni 189 by means of neutron diffraction
Authors: Schr–der J , Keuter J M , Priesmeyer H G
Published: July 2007

The residual stresses in the three layers of a composite averaged over the layer thickness were determined by means of neutron diffraction experiments using the Fourier stress spectrometer (FSS) at GKSS Forschungszentrum Geesthacht (Germany). For stress analysis, the lattice strains of many different Bragg reflections have to be measured in the directions along and normal to the rolling direction employed during fabrication of the composite. These results have been compared with residual stress measurements using the ring-core method (RCM) performed at the IFAM (Fraunhofer Institut für Angewandte Materialforschung), Bremen. In addition to the stress states in the rolling and transverse directions, averaged over the whole thickness, the normal components of the stress tensor in the different layers of the composite—which are not detectable by RCM—have been investigated by neutron diffraction.
The solution of plane crack problems by dislocation dipole procedures
Authors: Korsunsky A M , Hills D A
Published: July 2007

The solution of crack problems by employing dislocation loops (or dipoles) as strain nuclei is described. The relationship between this technique and dislocation density methods is outlined, the advantages of the former being illustrated by practical examples. The procedure also has the merit of being capable of extension to three-dimensional problems.