bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control of distortion due to welding and the additional cost involved
Authors: Thompson J D 
Published: July 2007

This paper details various aspects of distortion, how these faults occur, how they may be avoided, and if not avoided, how they may be most easily alleviated. The costs of avoiding or alleviating distortion are most difficult questions to discuss in that the records of many manufacturing shops do not list them separately, and they are often included in normal fabricating shop costs. Finally, the author tries to lay down some general principles of good practice that will minimize distortion and the consequent residual stress which would be detrimental to the finished structure.
On non-uniform illumination in a lens polariscope and remedies
Authors: Mehrotra C L 
Published: July 2007

Non-uniform illumination originates from (1) non-uniform transmission of light by model and polariscope elements, (2) diffraction and obstruction of light by the edges of elements and camera shutter, and (3) internal reflections of light from lenses and covering glasses. Effects appear as (1) a locally non-uniform background intensity distribution on the viewing screen or camera film, (2) a peripheral zone of generally reduced intensity, and (3) a bright central spot. This paper shows how local non-uniformities can be detected by photography. The peripheral zone may be avoided by use of a reduced size of field. Remedies for the deleterious bright spot may include a suitably chosen distance between first field lens and model, a small camera aperture and, in extereme cases, a translucent screen between light source and first field lens.
Replacement of quarter-wave plates by photographic double exposure for controlled density evaluation
Authors: Mehrotra C L , Meyer M L 
Published: July 2007

Isoclinics are eliminated by double exposure of a film in the camera of a plane polariscope and by rotation of the coupled polaroids through 45° between the two exposures of equal duration. The resultant photographic isochromatic pattern can be evaluated by interpreting and calibrating as lines of constant fractional fringe orders the sharp boundaries between dark and bright regions seen in a developed high-contrast film negative or the narrow equidensity lines obtained in a developed Agfacontour film negative. Alternatively a developed low-contrast film negative may be copied by contact or enlargement on high-contrast or Agfacontour film. The fractional fringe orders of the lines on any photograph depend on the exposure time, or copying exposure time, and on the coupling angle of the polaroids. Monochromatic light, or white light with blue-sensitive or orthochromatic film, may be used. An evaluated example and error analyses show that discrimination of fractional orders is about the same as in conventional compensation methods.
Thin annular plates having an inner clamp carrying bending moments
Authors: Ollerton E 
Published: July 2007

The problem considered here concerns a thin annular plate having an inner clamp which provides a simple support and an outer clamp which provides either a simple support or a built-in edge. The inner clamp supports a bending moment which tends to tilt it out of plane. A complete theoretical solution to the problem is presented for small deflections of the plate. Equations are derived for the deflections and stresses in terms of the applied bending moment, the plate geometry and the elastic constants of the plate material. Calculated results are compared with the trends of known values for plates with eccentric inner clamps.
Stationary creep prediction from model tests using reference stresses
Authors: Fessler H , Hyde T H , Webster J J 
Published: July 2007

The theoretical basis of the experimental determination of reference stresses from model tests is established for one-dimensional and complex stress systems. A graphical method of obtaining the experimental reference stress is presented and used to determine reference stresses for the strain in beams in pure bending and the tip deflection of cantilever beams from room-temperature tests of lead-antimony-arsenic models. The results are compared with theoretical values. It is shown how prototype deformation can be predicted from a test of a model of the component, model material creep data and the strain of a uniaxial prototype material specimen tested at the reference stress. Errors in the prediction of prototype deformations are considered.
Inextensional collapse of thin-walled tubes under axial compression
Authors: Johnson W , Soden P D , Al-Hassani S T S 
Published: July 2007

Inextensional collapse modes are presented for the axial compression of thin-walled tubes. Shortening is achieved by folding about fixed hinge lines to form a number of flat triangular planes. A new mechanism is propounded by which collapse proceeds progressively from one end of the tube, following the passage of a travelling hinge. Simple expressions are developed for mean collapse load and the energy absorbed during collapse of rigid-perfectly plastic tubes. Comparison of collapse modes and predicted loads with those obtained from experiments on rigid P.V.C. tubes of various thickness, diameter and length give encouraging agreement.
Quasistatic energy analysis of a slender D.C.B. specimen
Authors: Chow C L , Ngan K M 
Published: July 2007

This paper presents a method of quasistatic energy analysis for characterizing the fracture behaviour of a slender D.C.B. specimen having two parallel beam arms of low bending stiffness. Examples chosen are in-plane tension and anti-plane shear problems, which exhibit linear and nonlinear load-displacement relationships, respectively. The results derived analytically agree well with those obtained experimentally for both examples, thus successfully demonstrating the versatility of the quasistatic energy analysis in fracture studies. Stability of crack propagation for the geometries considered is analysed and found to be favourable unless there is a large negative value of d G/d a. Negative d G/d a was attained by contaminating portions of an uncracked specimen, and unstable crack propagation was observed experimentally in the contaminated regions.
On the measurement of residual shear stress in scragged torsion bars
Authors: Swift W A C 
Published: July 2007

The layer-removal method for determining the residual shear stress destribution in scragged torsion bars is examined. It is found that thickness of the layer removed is restricted if the ‘mean stress at mean radius’ assumption is to be valid. Also, it is shown that the modulus of rigidity used in the Fuchs-Mattson equation is not the conventionally accepted modulus, the use of which can lead to large errors in the calculation of the residual shear stress in the outer layers of material.
Flexural anisotropy of glass-fibre-reinforced thermoplastics injection mouldings
Authors: Smith G R , Darlington M W , McCammond D 
Published: July 2007

The anisotropy of flexural stiffness has been examined at low strain using ASTM bar and 3-mm and 6-mm thick edge-gated disc injection mouldings for two glass-fibre-reinforced thermoplastics (GFTP). Experimentally determined values were obtained under three-point bending and compared with theoretical prediction: which took account of the fibre orientation and length distributions in the mouldings. The flexural stiffness of the discs was also studied as a function of direction of test. The prediction of the resulting anisotropies in flexure compares well with experiment, but these anisotropies are markedly different from those measured previously in tension. It is concluded that it is necessary to have a knowledge of the fibre distribution of a GFTP moulding in order to predict successfully its mechanical properties, or to interpret measured data.
The location of defects in structures from measurements of natural frequencies
Authors: Cawley P , Adams R D 
Published: July 2007

A method of non-destructively assessing the integrity of structures using measurements of the structural natural frequencies is described. It is shown how measurements made at a single point in the structure can be used to detect, locate and quantify damage. The scheme presented uses finite-element analysis, since this method may be used on any structure. The principle may, however, be used in conjunction with other mathematical techniques. Only one full analysis is required for each type of structure. Results are presented from tests on an aluminium plate and a cross-ply carbon-fibre-reinforced plastic plate. Excellent agreement is shown between the predicted and actual damage sites and a useful indication of the magnitude of the defect is obtained.
Thermal stresses in cylindrical vessels with limpet coils
Authors: Kitching R , Zarrabi K 
Published: July 2007

A computer program is developed to undertake the elastic stress analysis of a limpet-coil vessel consisting of a cylindrical shell and part-circular coils, when the coils are at a different average temperature to that of the main shell. Results of the analysis are used to present data on maximum stresses for a wide range of practical geometries for the vessel.
Measurement of residual stresses by the hole-drilling method: Influence of hole eccentricity
Authors: Ajovalasit A 
Published: July 2007

The hole-drilling method is a semidestructive technique which allows the measurement of residual stresses. In this method, a source of error is due to the misalignment between the hole and rosette centres. This paper presents a theoretical analysis of the influence of such misalignment on the strains measured by the rosette. Formulae which give the residual stresses taking account of the hole eccentricity are derived. Finally, the errors, which affect the residual stresses when the eccentricity is neglected, are evaluated for some commercial strain-gauge rosettes especially developed for the hole-drilling method.
Bond of tube in semi-infinite elastic solid
Authors: Ivering J W 
Published: July 2007

The analysis of the bond stress of a thick-walled tube embedded at the surface of an elastic, isotropic, semi-infinite medium is presented. The condition of three-dimensional compatibility between the tube and the anchorage medium is taken into account. An equilibrium equation for a segment of an embedded tube is derived, from which bond stresses acting on the tube can be computed. The general solution obtained relates to the vector function for a uniform lineal load acting perpendicularly to the surface of an elastic half-space. The solution is in agreement with equations derived independently for cases of one-dimensional (lineal) compatibility. The equation of equilibrium derived for a tube segment embedded at the surface of an elastic half-space is transformed to a form suitable for solving the bond stresses of a tube anchorage embedded at some distance from the surface. A numerical solution of bond stresses obtained by elastic analysis is compared to the bond stress curve along the anchorage obtained experimentally.
Elastic stress parameters in simply supported skew plates in flexure
Authors: Cusens A R , Besser I I 
Published: July 2007

This experimental study was undertaken with the aim of examining the flexural behaviour of a skew slab bridge deck with particular regard to the obtuse corners and the boundaries of the structure. The investigation considered bending and twisting moments, and reactive and shearing forces under concentrated point loads. Tests were carried out on a simply supported asbestos-cement slab, with a 45° skew angle. Experimental results are compared with finite element solutions.
Triaxial fatigue testing machine for polymeric materials
Authors: Lawrence C C 
Published: July 2007

Part 1 of this paper is concerned with the design and development of a multiaxial fatigue testing machine. The machine structure is considered in some detail to emphasize the dynamic as well as the static stability essential in machines applying fatigue loading. The machine is capable of testing specimens of the same geometry in torsion, push-pull, and internal pressure (if hollow), either statically or dynamically. These test modes can be operated independently or in combination, both in phase and out of phase. Each mode can be stress or strain dependent. Part 2 deals with the associated extensometry, test procedures, and preliminary tests on polymethylmethacrylate. These preliminary tests, originally undertaken to test the capability of the machine, whilst not extensive enough to be considered rigorous, are included to illustrate some of the interesting potentialities of multiaxial testing.
Crack propagation in thin plates under double torsion
Authors: Chow C L , Ngan K M 
Published: July 2007

A method of analysis for characterizing non-linear crack propagation in thin plates under double torsion is presented. Quasistatic energy method is used to derive the fracture toughness and to study the stability conditions of crack propagation within the subcritical crack growth range. Non-linear relationship between the torque and angular deflection of a thin rectangular bar is well known. A thin rectangular plate containing a central longitudinal crack and acted upon by a system of four-point loading (two opposite forces on each side of the crack) causes non-linear structural response to this loading mode. The stability of crack propagation in thin plates under double torsion is examined for both the linear (thin plates) and non-linear (thick plates) cases. It is shown that improved stability can be attained if the specimen geometry and loading mode display a non-linear load-displacement relationship at constant crack area, as compared with the corresponding linear case. A series of experiments is conducted to measure the fracture toughness of PMMA material of different thicknesses. It is observed that the fracture toughness values evaluated analytically using the quasi-static energy method compare favourably with those measured experimentally. For the range of PMMA plate thicknesses considered, the effect of thickness on the fracture toughness of PMMA material is negligible. Finally, the validity of employing the double torsion specimen for fracture studies is examined by comparing the fracture toughness of thin plates of different thicknesses loaded separately by double torsion and by tension. No significant difference between the two sets of results is observed.
Effects of anisotropy and diaphragm size on biaxial stress—strain curves for sheet metals
Authors: Ilahi M Fazli 
Published: July 2007

When a circular diaphragm clamped at the edge is deformed by unilateral hydrostatic pressure the pole is under balanced biaxial tension if the absence of edge effects is assumed. The diaphragm test is an excellent way of obtaining the work-hardening characteristics of sheet metals to fairly high strains. Some previous investigators have tried to correlate the experimental and theoretical stress-strain characteristics of the pole of a diaphragm. In this present work 10 in. and 4 in. diameter dies and sheet metals with an average thickness of 0·040 in. have been used. Previous investigators used diaphragms of smaller sizes; but if the thickness—diameter ratio can be kept small the bending stresses will be negligible. All sheet metals are anisotropic and for simplicity anisotropy in the plane is neglected, so that an average R value can be adopted. Hill's theory of yielding and plastic flow for anisotropic materials has been used together with the uniaxial tension test values to predict the stress—strain characteristic at pole. The effects of the diameter of the die and the normal anisotropy of the sheet metals on the stress—strain characteristics at pole are discussed.
An experimental study of the stresses in a shell of revolution with geometrical imperfections and cracks
Authors: Godoy L A , Croll J G A , Kemp K O , Jackson J F 
Published: July 2007

Interest in the effects of geometrical imperfections and cracks on the stresses in reinforced concrete shells has been stimulated by the failure of the Ardeer cooling tower. Due to the extreme difficulties of testing doubly curved, reinforced concrete shell models, a programme of experiments on an axially loaded aluminium cylinder containing controlled axisymmetric geometric imperfections has been carried out to show the nature of the stress distributions that occur when meridional cracking passes across the imperfection. Results over a wide range of crack configurations, for which the discrete cracks have both partial and complete loss of stiffness in the circumferential direction, are found to be in close agreement with predictions from an appropriate finite element numerical modelling. It is shown how the concentration of membrane hoop stresses associated with the imperfections are redistributed to cause substantial changes in meridional bending and membrane stresses only when a complete loss of stiffness occurs at the cracks. With the thin reinforced concrete shells used in cooling towers having only limited flexural capacity, the combination of geometric imperfections and cracks could, as a consequence, readily lead to failure once yield or fracture of the hoop reinforcement occurs.
A simplified approach to calculating stresses due to radial loads and moments applied to branches in cylindrical pressure vessels (calculations to BS 5500, Appendix G)
Authors: Teixeira M A , McLeish R D , Gill S S 
Published: July 2007

Simplified charts are presented for elastic stress concentration factors due to radial loads and circumferential and longitudinal moments applied to circular branches normal to cylindrical pressure vessels. The charts are based on the procedures given in Appendix G of BS 5500. The assumptions implied in Appendix G and the limitations on the geometrical parameters ro/r and r/t are discussed. A modification to Appendix G is suggested which is slightly more restrictive than at present. Published results for stresses due to local loads on branches in cylindrical vessels are compared with the values given by the charts.
A review of stress-strain paths and constitutive relations in the plastic range
Authors: Rees D W A 
Published: July 2007

Plastic strain paths produced by both radial and non-radial stress paths are reviewed for metals and alloys under uniaxial and biaxial stress. The present interpretation illustrates collective trends and offers theoretical solutions for each of several stress paths. In general the strain path is linear for a radial stress path for most materials at low to medium temperatures. The isotropic quadratic hardening rule of von Mises rarely describes the strain behaviour accurately. but a simple anisotropic quadratic form provides good agreement by the uniform hardening rule. Exceptions are found for magnesium and an associated alloy at room temperature and for the high temperature deformation in an aluminium alloy. Descriptive yield functions are presented and the anistropic constants determined for one particular function of the Bailey form. Strain paths produced by outward non radial zig-zag and stepped stress paths are approximately linear provided that they are confined to a narrow band in stress space. It is shown that an equivalent radial stress path analysis provides good agreement with experiment. The strain paths resulting from stress paths containing corners and from paths composed of partial or complete unloading followed by reloading in a different direction are non-linear. The behaviour is attributed to strain history; namely, a Bauschinger effect where unloading occurs and an interaction between direction dependent plastic strains for stress paths containing corners. For unloading-reloading paths a rotation in the strain path towards a linear direction is indicative of the transient nature of strain history. Good agreement is found with the prediction from each of three rules of anisotropic hardening. They are thus generalized to provide the plastic strain response to any stress path that is composed of linear segments. Modifications that account for the effects of non-linear work hardening and creep are discussed.
A rig for creep and thermal ratchet testing of lead alloy models
Authors: Hyde T H , Fessler H , Webster J J 
Published: July 2007

The development and calibration of a rig and an axisymmetric lead alloy component for isothermal creep, non-isothermal creep, and thermal ratchetting testing is described. Steady and variable, axial mechanical loads are applied by a dead weight and lever system. Thermal loads are applied by controlled variations of the temperature of water flowing through the bore and along the outside of the component. Strains and temperature are measured with electrical resistance strain gauges and thermocouples, respectively.
End reinforcement and grips for anisotropic tubes
Authors: Highton J , Soden P D W 
Published: July 2007

A method of gripping and reinforcing the ends of anisotropic tubes for testing under combined axial load and internal pressure is analysed. Edge solutions for long, cylindrical, specially orthotropic shells are considered. The tube, reinforcement, and grips are then modelled as an assembly of short, parallel, multilayered, thin-walled, orthotropic shells. Theoretical results are presented for the stress distribution in a ± 75 degree filament-wound E glass/epoxy resin tube with circumferentially wound glass fibre reinforced ends.
A rig for controlled cyclic strain and temperature testing
Authors: Beauchamp D J , Ellison E G 
Published: July 2007

A servo-hydraulic test rig capable of applying combined temperature and strain or load cycles has been developed and commissioned. The nature of the test has dictated the specimen form as a hollow, hour-glass type. The critical problem of a suitable extensometer for temperature and strain cycling has been solved. The device designed and produced shows negligible transient temperature effects, has a high resolution of better than 0.1 μm, and is mechanically very stable. The heating and cooling is controlled by an induction heating system with grip cooling; additional cooling is available using compressed air passing through the hollow specimen. The system is capable of following a temperature ramp to within 1°C linearity. The thermal strain associated with a temperature cycle is compensated for using a microprocessor system specially developed for the purpose, which also enables a mechanical strain-stress loop to be plotted during a test. Both ‘in-phase’ and ‘out-of-phase’ temperature/strain cycles have been carried out and development continues to include dwell periods.
Plastic collapse loads of cylindrical pressure vessels supported by rigid saddles
Authors: Tooth A S , Jones N 
Published: July 2007

The plastic collapse of cylindrical pressure or storage vessels supported by rigid saddle supports is examined both experimentally and in an exploratory theoretical manner. Two cases are considered: (1) when the saddle is welded to the vessel, and (2) when the saddle and vessel are not welded. It is found that the load to cause first yield is much smaller than the fully plastic load and thus there exists a considerable reserve strength even when a vessel is stressed up to yield. The object of this investigation is to examine this considerable reserve strength and to provide results which, when taken with previous elastic studies, should help to improve vessel and support design.