Showing papers in "Journal of Strain Analysis for Engineering Design in 1995"
TL;DR: In this article, two-dimensional finite element (FE) studies for plane stress, plane strain and axisymmetric conditions were conducted to simulate 4 per cent cold working of a 6.35 mm diameter hole in a 6 mm thick plate of 2024 T 351 aluminium alloy.
Abstract: Two-dimensional finite element (FE) studies, for plane stress, plane strain and axisymmetric conditions, were conducted to simulate 4 per cent cold working of a 6.35 mm diameter hole in a 6 mm thick plate of 2024 T 351 aluminium alloy. The simulations were used to assess the influence of strain hardening, the role of reversed yielding and through-thickness residual stress distributions. Experiments were also conducted to determine the tensile and compressive stress-strain response of the aluminium alloy, revealing a pronounced Bauschinger effect and non-linear strain hardening in compression. The FE simulations and results from several earlier analytical models were compared and substantial differnces found in the region of reversed yielding. Approximations used to model the compressive deformation behaviour of the material overestimate the compressive residual stresses at the hole edge. From the axisymmetric FE model a residual stress gradient through the plate thickness was found. The plane stre...
74 citations
TL;DR: In this article, the influence of optical retarders on the isochromatic fringes obtained by automated white light photoelasticity using methods such as those based on spectral content analysis (SCA) and on primary colour (red, green and blue) analysis was examined.
Abstract: This paper deals with the influence of optical retarders on the isochromatic fringes obtained by automated white light photoelasticity using methods such as those based on spectral content analysis (SCA) and on primary colour (red, green and blue) analysis. In the following the light intensity equations of dark- and light-field polariscopes with both crossed and parallel optical retarders are reviewed. In particular, it is shown that the retardance error of the quarter-wave plates produces an attenuation of the maximum intensity in dark field and an increase of minimum intensity in light field. Experimental evidence of the influence of optical retarders is also shown.
33 citations
TL;DR: In this article, the relative movements between the centrelines of the strands of a wire rope during bending are analysed, as well as the movements between individual wires forming those strands, and used to identify the position of greatest relative movement (slip).
Abstract: The relative movements between the centre-lines of the strands of a wire rope during bending are analysed, as are the movements between the individual wires forming those strands. The formulae are applied to an example, and used to identify the position of greatest relative movement (slip). This position coincides with the most common location of wire failures in bend-over-sheave fatigue testing, suggesting that such slip calculations may form a valuable input to wire rope fatigue predictions.
27 citations
TL;DR: In this article, it was shown that the free bending strains in the innermost layer of a strand in a rope taken as an example are higher than those in the outer layer wires, while the second wire layer has the lowest bending strains.
Abstract: The changes in curvature in single and double helices as they are bent into circular arcs are derived from first principles. This analysis is applied to wire ropes to examine the bending strains in the wires of a frictionless rope as it is bent over a sheave. It is shown that the free bending strains in the wires in the innermost layer of a strand in a rope taken as an example are higher than those in the outer layer wires, while the second wire layer has the lowest bending strains.
24 citations
TL;DR: In this article, the elastic-plastic stress-strain field produced in a thin plate under equibiaxial loading during the operation of drilling a through-thickness hole was analyzed.
Abstract: The elastic-plastic stress-strain field produced in a thin plate under equibiaxial loading during the operation of drilling a through-thickness hole was analysed. The plane stress condition and Tresca yield criterion were assumed for an elastic-perfectly plastic material. These hypotheses allowed the problem to be formulated by means of ordinary differential equations which were analytically solved. Within these particular conditions, the results gave indications of the effect produced by plasticity on the widely used hole-drilling method for residual stress measurement. In particular, the equality of final results with those obtained for a plate with a pre-existing hole loaded in an elastic-plastic regime gives useful indications for the experimental analysis of the effect of plasticity on residual stress measurement.
24 citations
TL;DR: In this paper, the authors describe the solution of crack problems by employing dislocation loops (or dipoles) as strain nuclei, and the relationship between this technique and dislocation density methods is outlined, the advantages of the former being illustrated by practical examples.
Abstract: 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.
16 citations
TL;DR: In this paper, the frictional behaviour of heavily loaded wire ropes bent over relatively small sheaves has been investigated with 6 × 36, 28 mm and 35 mm diameter, IWRC (independent wire rope core) and FC (fibre core), bright and galvanized ropes being tested, over sheaves with D/d ratios between 12 and 20.
Abstract: The frictional behaviour of heavily loaded wire ropes bent over relatively small sheaves has been investigated with 6 × 36, 28 mm and 35 mm diameter, IWRC (independent wire rope core) and FC (fibre core), bright and galvanized ropes being tested, over sheaves with D/d ratios between 12 and 20. The groove profiles used were plain U and undercut U, with groove diameters 2.5 per cent smaller than the rope nominal diameter. Some pilot studies were also run on high-strength synthetic fibre ropes. The measurements showed that the effective friction coefficient increased with decreasing line tension and increasing sheave diameter for unused surfaces but became almost constant for used surfaces. It was shown that the undercut U groove had a higher frictional hold than the plain U groove but gave rise to early erratic slip. Galvanized rope had a lower friction coefficient while increased speed of sliding decreased friction.
16 citations
TL;DR: In this article, the authors used Neutron strain scanning 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.
Abstract: 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, ...
15 citations
TL;DR: In this paper, a study on the determination of stress intensity factors in tubular joints in offshore jacket structures using finite elements was conducted. But the results were only applied to a simple T-joint, and the validity of the numerical models was established by comparing the results with existing experimental data.
Abstract: This paper reports a study on the determination of stress intensity factors in tubular joints in offshore jacket structures. Using finite elements, information on stress concentration factors and through-thickness stress distributions was first obtained from uncracked geometries. This was correlated with the stress intensity factors in joints containing semi-elliptical cracks which were modelled with line-spring elements. The validity of the numerical models was established, using a simple T-joint, by comparing the results with existing experimental data and results from three-dimensional finite element analyses. Various modelling assumptions used in previous numerical work were critically examined. The multi-planar effects in tubular joints were simulated by subjecting the out-of-plane braces to various loadings and restraints. It was found that a relationship exists between the stress concentration factor, the degree of bending and the stress intensity factor for the various loading and restraint cases considered, and that the stress intensity factors in multi-planar tubular joints can be estimated by suitably modifying an existing empirical equation for surface cracks in plain plates.
14 citations
TL;DR: In this paper, a 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.
Abstract: 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.
11 citations
TL;DR: In this article, a series of thick, wide, flat plates with oblique holes subjected to uniaxial tension and out-of-plane bending has been carried out using the finite element method and in some cases the boundary element method.
Abstract: Stress analysis of a series of thick, wide, flat plates with oblique holes subjected to uniaxial tension and out-of-plane bending has been carried out using the finite element method (FEM), and in some cases the boundary element method (BEM). Different plate thickness-hole diameter ratios, angles of hole obliquity and orientation have been considered to provide stress concentration factors at such holes. The work covers plate thickness-hole diameter ratios from 1.3 to 3.0, hole obliquity angles from 0 to 60° and orientation of the major axis of the surface ellipse relative to the applied load direction of 0 to 90°. The results for uniaxial tension have been compared with those determined using the photoelastic frozen-stress technique in order to verify the finite element models before proceeding to the bending cases, which provide new data.
TL;DR: In this paper, the authors examined flow and instability of a zinc-clad sheet used for the manufacture of car panels and derived the limiting uniform strain that is found to remain constant in regions exterior to local neck formation.
Abstract: This paper examines flow and instability of a zinc-clad sheet used for the manufacture of car panels. Three forming properties are reported from off-axis tensile testing: (a) anisotropy in the plane of the sheet, (b) tensile instability and (c) homogeneity of deformation. The analysis correlates the directional flow behaviour using the Hill yield function (1)† as a basis for equivalence. This function explains satisfactorily the linear plastic strain paths and the variation in r values observed but does contract flow behaviour to a single curve. A subtangent is derived for the off-axis testpiece in terms of its orientation and two strain ratios referred to its axis. This is used to derive the limiting uniform strain that is found to remain constant in regions exterior to local neck formation. A condition is established for which the principal axes of stress and plastic strain remain coincident. It is shown, from the measured rotations of the principal material axes, that deformations conform to st...
TL;DR: In this paper, a generalized experimental method for measuring mixed-mode stress intensity factors is described for use in orthotropic materials, where the displacement fields around the crack tip are used to record the whole field surface displacements of double edge cracked specimens made from unidirectional laminated composites.
Abstract: A generalized experimental method for measuring mixed-mode stress intensity factors is described for use in orthotropic materials. Moire interferometry has been used to record the whole field surface displacements of double-edge cracked specimens made from unidirectional laminated composites. The moire 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.
TL;DR: In this article, the theoretical analysis of a large-diameter strand wire rope with a fibre core is presented, using results from a previously reported orthotropic sheet model for analysing the behaviour of its constituent helical strands.
Abstract: The theoretical analysis of a large-diameter stranded wire rope with fibre core, using results from a previously reported orthotropic sheet model for analysing the behaviour of its constituent helical strands, is reported. The present model is (unlike previously available theories for stranded wire ropes) capable of catering for the effects of interwire friction and contact deformations.The proposed theory provides a fairly simple means of obtaining the upper (no-slip) and lower (full-slip) bounds to rope effective stiffness coefficients under axial/torsional coupling with encouraging correlations found between the theoretical predictions for the axial stiffness under full-slip conditions and experimental data for some realistic stranded wire ropes with fibre cores.
TL;DR: In this article, the stress and stiffness analyses of modified double-containment corner joints were carried out, in which plates are bonded at a right angle into slots of a corner support.
Abstract: In this study, the stress and stiffness analyses of modified double-containment corner joints, in which plates are bonded at a right angle into slots of a corner support, were carried out u...
TL;DR: In this paper, the effect of the variations of material combinations on the fracture behavior of an arbitrarily inclined crack terminated at a bimaterial interface was investigated by using the complex variable method, a comprehensive analysis of the state of stress and stress intensity factors (SIFs) was performed.
Abstract: In this paper, the effect of the variations of material combinations on the fracture behaviour of an arbitrarily inclined crack terminated at a bimaterial interface was investigated. By using the complex variable method, a comprehensive analysis of the state of stress and stress intensity factors (SIFs) was performed. The digital photoelastic technique was also employed to verify the analytical results. To ensure the accuracy in the process of determining SIFs, a visual check between experimentally obtained images and theoretically reconstructed images was performed. It was concluded that far-field effects usually found in the homogeneous case had to be included in the stress equations.
TL;DR: In this article, the authors used the concept of configuration factor for notches, similar to that used to calculate crack-tip stress field intensity factors, 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.
Abstract: 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
TL;DR: In this article, a simplified model of the plastic tibial plateau of a typical unicondylar knee prosthesis is presented, which allows the parametric study of contact stresses experienced by the plastic component during relatively severe loading conditions.
Abstract: The purpose of this investigation was to produce a simplified model of the plastic tibial plateau of a typical unicondylar knee prosthesis that would allow the parametric study of contact stresses experienced by the plastic component during relatively severe loading conditions. This involved the design, production and testing of a three-dimensional axisymmetric embedded strain gauge model of the tibial plateau and the application of a suitable theoretical analysis. The principal feature of the strain gauge model was the possibility of varying the thickness during the experimental procedure while keeping the maximum number of embedded gauges active. The Hertzian contact theory was used as a basis for the prediction of integration errors associated with placing strain gauges in locations subject to large strain gradients. A theoretical analysis that took the layered nature of the contact model into account was carried out which provided full field data for comparison with Hertzian and experimental results. Good agreement was obtained between theoretical and experimental values along the model axis, while at off-axis locations theoretical results based on the layered analysis compared reasonably with embedded strain gauge data. Very slight discrepancies between the experimental and idealized boundary conditions present in the initial stages of testing resulted in significant differences between embedded strain gauge and theoretical data.
TL;DR: In this article, the authors examined the dependence of J-R curves on size of test piece for fully plastic DNB tests on HY130 steel, taken to large amounts of ductile crack growth (60 per cent of the ligament) for a range of initial widths at 20 mm thick and one geometrically similar size, 50 mm thick.
Abstract: The dependence of J-R curves on size of test piece is examined for fully plastic deep notch bend (DNB) tests on HY130 steel, taken to large amounts of ductile crack growth (60 per cent of the ligament) for a range of initial widths at 20 mm thick and one geometrically similar size, 50 mm thick. The object is to understand the cause of the widely different patterns of behaviour that have been reported in the literature, even within the DNB type of configuration. In the present tests, the proportion of shear lip is the same for the geometrically similar pair but the J-R curve for the 50 mm thick piece is much lower than for the similar piece, 20 mm thick. The rate of change of displacement, dq/da, is analysed using the factor, r * , that defines the instantaneous centre of rotation at each step of growth, to give a measure of crack tip opening angle (CTOA), α g . After an initial transient regime of small growth, α g and r * remain constant. The normalized load, L, rises due to work hardening during crack growth by amounts that depend on size while α g and r * vary mildly with initial width to give an appreciable variation of the combined term Lα g /r * , which is the factor that controls the behaviour of the J R curves. It is speculated that CTOA and its variation with configuration (as seen in the literature) may, for large growth, assume the role of the two parameters suggested in recent literature as controlling the variation of toughness with constraint.
TL;DR: In this paper, 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).
Abstract: 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 fur 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.
TL;DR: In this article, the Lagrange multiplier method is used for the application of displacement constraints to surface Gauss points of a contacting body to prevent mesh overlap, which allows the effective modelling of two-and three-dimensional contact problems, with or without friction, using higher order elements.
Abstract: This study deals with the development of a specialized finite element algorithm suitable for a non-linear contact stress analysis of a model of a plastic tibial plateau of a typical unicondylar knee prosthesis. The principle feature of the contact algorithm is the use of Lagrange multiplier methods for the application of displacement constraints to surface Gauss points of a contacting body to prevent mesh overlap. This allows the effective modelling of two- and three-dimensional contact problems, with or without friction, using higher order elements. Through the selection of suitable benchmark tests, the performance and accuracy of the algorithm was assessed prior to the model analysis. Good agreement was obtained between the finite element results for the contact model and existing theoretical and experimental data. It was found that the Hertzian theory failed to accurately predict localized stresses at the contact interface when the indenter was much stiffer than the model.
TL;DR: In this article, the shakedown behavior of a CT (compact tension) specimen consisting of St52 steel under cyclical loading was investigated, and experiments were carried out for determining the limit load. Satisfactory agreement has been achieved between the results from these different methods.
Abstract: The paper deals with the shakedown behaviour of a CT (compact tension) specimen consisting of St52 steel under cyclical loading. Experiments have been carried out for determining the shakedown limit load. For comparison, the analytical and numerical methods are used to study the same problem. Satisfactory agreement has been achieved between the results from these different methods.
TL;DR: In this article, a contact mechanics approach based on the implementation of the boundary element method is used to analyse the stress distribution and frictional slip behaviour around spherical inclusions and cylindrical fibres embedded in infinite dissimilar matrices.
Abstract: A contact mechanics approach, based on the implementation of the boundary element method, is used to analyse the stress distribution and frictional slip behaviour around spherical inclusions and cylindrical fibres embedded in infinite dissimilar matrices. A comparison between the boundary element and the corresponding finite element solutions shows good agreement between the two approaches. A range of inclusion/matrix elastic material properties is covered in the analysis together with a mismatch in thermal properties and thermal cooling.
TL;DR: In this paper, the authors performed burst tests on closed-ended thin wall tubes with axially aligned, external, semicircular, crack-like flaws and found that the crack surfaces exhibited a smooth mirror-like appearance near the crack initiation site, followed by a mist region and then a hackle region.
Abstract: Burst tests have been performed on closed-ended thin wall tubes with axially aligned, external, semicircular, crack-like flaws. The tubes were made of Araldite CT200 with HT907 hardener. Dynamic crack propagation rates between 0.14c 1 and 0.30c 1 were measured, c l being the velocity of longitudinal waves in the walls of the tubes. The fracture surfaces exhibited a smooth mirror-like appearance near the crack initiation site. This was followed by a mist region and then a hackle region. The roughness in the hackle region becomes progressively greater with distance from the initiation site and crack branching can eventually occur. The K ID /K IC (where K ID is the applied dynamic stress intensity factor and K IC is the plane strain fracture toughness) value at which the hackle region begins is about 3.34 and the K ID /K IC value at which branching begins is about 8.75. Previously reported work only contains results for K ID /K IC up to about 5. The present work contains results for K ID /K IC up to about 14, which correlate with previous work for K ID /K IC values less than about 4. However, previous work has indicated that a unique relationship may exist between υ/c 1 and K ID /K IC . The present work indicates that although this is a good approximation, a systematic variation with load (pressure in this case) has been detected.
TL;DR: In this paper, the problem of determining the opening mode (mode I) stress intensity factor (SIF) from the photoelastic isochromatic fringe pattern associated with a surface crack located in the ligament region between two radial nozzle-cylinder junctions of pressure vessel has been investigated.
Abstract: In this paper, the problem of determining the opening mode (mode I) stress intensity factor (SIF) from the photoelastic isochromatic fringe pattern associated with a surface crack located in the ligament region between two radial nozzle-cylinder junctions of pressure vessel has been investigated. The objective is to determine the influence of geometry, size and location of the surface flaw with respect to the radial nozzles. Starting from the crack tip stress field formulation of Etheridge and Dally using three parameters (1)† a new method suited to the analysis of photoelastic data obtained from a single isochromatic fringe loop to extract the SIF has been introduced. This new method has been used to predict SIFs for a range of pressure vessel nozzle spacings when photoelastic models are subjected to internal pressure loading.
TL;DR: In this article, the problem of cracked plates stiffened by three-dimensional stringers was investigated using transmission photoelasticity, and models were produced of the hole-in-the-plate geometry stiffening by a combination of stringers transverse and/or parallel to the applied tensile load.
Abstract: The problem of cracked plates stiffened by three-dimensional stringers is investigated using transmission photoelasticity. Models were produced of the hole-in-the-plate geometry stiffened by a combination of stringers transverse and/or parallel to the applied tensile load. Cracks of different lengths emanating from one edge of the hole and approaching a stringer were examined. These cases represent geometry and loading conditions for which it would normally be very difficult to obtain results using analytical methods. The stringer-stiffened plates show a consistent reduction in the non-dimensional stress intensity factor of about 20 per cent irrespective of the arrangement of stringers.
TL;DR: In this article, it was shown that the burst pressure for the cylinders, with different depths of crack, can be predicted from the corresponding 3PB apparent fracture toughness data, and that the notches in the cylinders and 3PB specimens must be very sharp, and manufactured in a similar way, for the predictions to be accurate.
Abstract: Three-point-bend (3PB) specimens with real cracks and very sharp notches have been manufactured from Araldite CT200 with HT907 hardener. The plane strain fracture toughness, KIC, has been obtained from cracked specimen tests and the apparent plane strain fracture toughness, KAppIC, has been obtained for various very sharp notched widths. A systematic variation of apparent fracture toughness with notch width has been observed.Burst tests have also been performed on cylinders with similar, very sharp, axially aligned, external, semi-circular notches. It has been shown that the burst pressure for the cylinders, with different depths of crack, can be predicted from the corresponding 3PB apparent fracture toughness data. The notches in the cylinders and 3PB specimens must be very sharp, and manufactured in a similar way, for the predictions to be accurate. Therefore, by loading model components containing very sharp crack-like flaws to obtain the failure loads, the failure loads of similar actual compo...
TL;DR: In this article, the interlaminar strength of woven carbon/epoxy composite laminates in tension and in combined tension with minor transverse tractions was analyzed using an analytical solution for the stress distribution within the C-shaped test specimens.
Abstract: ‘C’-shaped test specimens have been used to find the interlaminar strength of woven carbon/epoxy composite laminates in tension and in combined tension with minor transverse tractions. An analytical solution for the stress distribution within the “C” specimen, of arbitrary lay-up, is developed to permit a rigorous interpretation of the results, which confirm that the presence of relatively minor through-thickness stresses will have a profound influence on the strength of the component.
TL;DR: In this paper, the steady state flexural behavior of rotating cantilever beams with two orthotropic facings and an isotropic inner core was analyzed by using the variational principle.
Abstract: Governing equations for predicting the steady state flexural behaviour of rotating sandwich cantilever beams with two orthotropic facings and an isotropic inner core are formulated by using the variational principle. Those for describing the steady state deformation and displacements of an orthotropic beam are also formulated by using the same method. The effect of the curing temperature of the orthotropic material upon steady state stress distributions is also included in this analysis. Exact solutions of these differential equations are obtained to calculate displacements and stress distributions in both symmetric and non-symmetric sandwich beams subjected to uniformly distributed loads. Steady state stress values for an orthotropic beam loaded with a flatwise tip force are calculated so that they can be compared to dynamic measurements for the type of beam reported in the literature. The present analysis also predicts both the lateral and the transverse inertio-elastic instabilities due to the ...
TL;DR: In this article, two methods used to satisfy the boundary conditions in the case of an open complete rotating ring are considered and it turns out that for smaller ratios of radii the collocation method yields better results than the moment method.
Abstract: In this paper two methods used to satisfy the boundary conditions in the case of an open complete rotating ring are considered. It turns out that for smaller ratios of radii the collocation method yields better results than the moment method.