Showing papers in "Journal of Strain Analysis for Engineering Design in 1996"
TL;DR: In this paper, constitutive equations have been developed to describe the creep behavior of a 0.5Cr-0.25V ferritic steel under uniaxial and multi-axial states of stress, as well as over the temperature range of 600-675°C.
Abstract: Constitutive equations have been developed to describe the creep behaviour of a 0.5Cr-0.5Mo-0.25V ferritic steel under uniaxial and multi-axial states of stress, as well as over the temperature range of 600–675°C. This material has widespread application as the parent steam pipe in the power generation industry. An accurate description of creep behaviour has been achieved by formulating constitutive equations that describe the physical mechanisms of deformation and rupture. To this end, two state variables were introduced to model intergranular creep cavitation and the coarsening of carbide precipitates respectively. The influence of temperature on the constitutive equations is also considered and activation energies are identified for each of the material constants that show a notable temperature dependence.Numerical optimization methods are discussed for the determination of the material constants and of the corresponding activation energies. The constitutive equations provide a good representat...
126 citations
TL;DR: In this article, a deep hole method was used for measuring the through-thickness distribution of residual stresses in ferritic steel rectangular bars, and the distortion of a reference hole used in the method was interpreted using analytical techniques to determine the residual stresses present.
Abstract: The development of a deep hole method, based on earlier techniques, for measuring the through-thickness distribution of residual stresses is described. The distortion of a reference hole used in the method was interpreted using analytical techniques to determine the residual stresses present. The accuracy of the method was investigated using a 100 mm deep plastically deformed ferritic steel rectangular bar. The stresses in the bar were determined by surface strain gauges. The axial residual stresses through the depth of the bar, measured by the deep hole method, were found to be within ± 35 MPa of the stresses determined from the strain gauges in the central 80 mm of the bar.
123 citations
TL;DR: In this paper, the authors analyzed the fracture load of a sandwich beam as linear elastic bending of the top skin on a rigid-perfectly plastic foundation (the core), and the theoretical predictions of fracture load from this simple theory were shown to be in good agreement with experimental results from indentation tests on strips of sandwich panel, with glass-fibre-reinforced plastic skins and foam core, supported on rigid base.
Abstract: Indentation of a sandwich beam is analysed as linear elastic bending of the top skin on a rigid-perfectly plastic foundation (the core). The theoretical predictions of fracture load from this simple theory are shown to be in good agreement with experimental results from indentation tests on strips of sandwich panel, with glass-fibre-reinforced plastic skins and foam core, supported on a rigid base.
87 citations
TL;DR: In this article, mechanisms-based constitutive equations are proposed for the high-temperature behaviour of a class of titanium alloys, for which the deformation mechanisms include diffusional creep, grain boundary sliding, dislocation creep and grain growth.
Abstract: Mechanisms-based constitutive equations are proposed for the high-temperature behaviour of a class of titanium alloys, for which the deformation mechanisms include diffusional creep, grain boundary sliding, dislocation creep and grain growth A computational procedure has been developed for the determination of the constitutive equations from a material database The constitutive equations and the procedure for their determination have been validated by modelling the behaviour of the titanium alloy Ti-6Al-4V at 927°CIt is shown that the procedure developed for the determination of the mechanisms-based constitutive equations can be used to identify the important deformation mechanisms in operation for particular stress, temperature and strain rate conditions For the case of the Ti-6Al-4V material, the procedure developed correctly predicts the material hardening due to grain growth and indicates that an additional hardening mechanism operates In addition, the procedure is able to identify grain
84 citations
TL;DR: In this article, a finite volume formulation for discretizing and analysing plane elastostatic problems is described, where equilibrium equations which relate the displacements at the center of a general quadrilateral cell to those in neighbouring cells are developed.
Abstract: A finite volume formulation for discretizing and analysing plane elastostatic problems is described. Equilibrium equations which relate the displacements at the centre of a general quadrilateral cell to those in neighbouring cells are developed. After the application of suitable boundary conditions, an iterative method is employed to solve the resulting system of simultaneous equations and produce the displacement field, from which the strain and stress fields are derived subsequently. Stress distributions for a test problem, an elliptic plate pierced by an elliptic hole and loaded on the outer boundary, are determined for meshes of increasing refinement. The distributions are compared with those determined using triangular and quadrilateral finite elements and the analytical solution.
73 citations
TL;DR: In this article, the origin of the lack of symmetry in the earlier models has been identified and a symmetric model developed, which brings forth the much needed agreement between the global (strand) and the local (wire) responses which should help simplify considerably the analysis of multi-layer strands and multi-strand wire ropes.
Abstract: Among several mathematical models for predicting the mechanical response of a helical wire strand to axisymmetric tension and torque derived in the literature over five decades, purely tensile wire linear elastic models have the symmetry of a stiffness matrix. Curiously, in those models where wire bending and torsion terms were included there was a lack of symmetry. In this paper the origin of the lack of symmetry in the earlier models has been identified and a symmetric model developed. The correct generalized strains for this purpose were derived using Wempner's theory and verified using Ramsey's theory. The validity of this model has been verified by comparing its results with that of earlier models and experiments available. This linear elastic symmetric model brings forth the much needed agreement between the global (strand) and the local (wire) responses which should help to simplify considerably the analysis of multi-layer strands and multi-strand wire ropes.
68 citations
TL;DR: In this paper, the residual stress distribution around split-sleeve cold-expanded holes has been measured as a function of both position through the plate thickness and around the hole through novel use of the Sachs method.
Abstract: Cold expansion of fastener holes is an increasingly common way of improving the fatigue endurance of airframes Although a number of methods of cold expansion are possible, the split-sleeve cold-expansion process is the most widely accepted and is widely used in the repair and manufacture stages of both military and civil aircraft In the present work, the residual stress distribution around split-sleeve cold-expanded holes has been measured as a function of both position through the plate thickness and around the hole through novel use of the Sachs method It is found that the residual hoop stresses being generated at the mid-thickness of the plate at orientation 90° from the position of the split in the expansion sleeve It is suggested that this variation must be taken into account both in the implementation of the technology and in any potential model used for the prediction of fatigue life of cold-expanded holes
61 citations
TL;DR: An attempt has been made to identify the reason for loss of accuracy in evaluating the field parameters in stress concentration zones and the use of Jones calculus to understand these methodologies are brought out.
Abstract: The potential of digital image processing hardware to record intensity data at video rates has resulted in a new approach for data collection. Efforts were aimed at evaluating isochromatic ...
48 citations
TL;DR: In this paper, eight pairs of carbon and stainless steel, long and short radius welding elbows were tested under conditions of steady internal pressure and in-plane, resonant dynamic moments that simulated seismic excitations.
Abstract: Eight pairs of carbon and stainless steel, long and short radius welding elbows were tested under conditions of steady internal pressure and in-plane, resonant dynamic moments that simulated seismic excitations. The elbows had an outside diameter of 60.3 mm and thicknesses of 3.91 and 5.54 mm. The material properties are reported, and the testing procedure and experimental programme fully described. The dynamic response of the comonents indicates that the stainless steel elbows behave differently from the carbon steel elbows.The cyclic strain accumulation for each component is assessed and ratios of applied to limit moments of the elbows at onset of ratcheting are given for each material. While the gross deformation range increased with level of input in testing, no permanent overall swelling or ovalization was recorded; this is contrasted with similar results reported in the general literature.
42 citations
TL;DR: The integral equation method is the most suitable calculation procedure for the determination of non-uniform residual stresses by semi-destructive mechanical methods such as hole and ring-c....
Abstract: The integral equation method is the most suitable calculation procedure for the determination of non-uniform residual stresses by semi-destructive mechanical methods such as hole and ring-c...
25 citations
TL;DR: In this paper, the linearity of response was tested using a split Hopkinson pressure bar arrangement, and the results obtained illustrate the effectiveness of piezoelectric film strain gauges in the measurement of axial stress waves.
Abstract: Piezoelectric polymers have been used to form the basis of dynamic strain gauges for the detection of stress waves. The linearity of response was tested using a split Hopkinson pressure bar arrangement. The results obtained illustrate the effectiveness of piezoelectric film strain gauges in the measurement of axial stress waves.
TL;DR: In this article, analytical solutions for the deformations of and stresses in two-material, two-bar structures, beams in bending and thick cylinders, under creep conditions, were presented.
Abstract: Analytical solutions are presented for the deformations of and stresses in two-material, two-bar structures, beams in bending and thick cylinders, under creep conditions. Results obtained using these solutions were compared with corresponding single-material solutions and were used to assess the applicability of reference stress and other simple design rule concepts, established for single-material structures, to two-material components and structures.
TL;DR: In this paper, the stress state in a circular ring under two opposite forces on its outer boundary was analyzed by using the complex variable method and the principle of superposition, and stress concentration factors were calculated for the ratio of inner and outer radii in the range 0.95 and are presented in tabular form.
Abstract: This paper analyses the stress state in a circular ring under two opposite forces on its outer boundary. The solution is obtained by using the complex variable method and the principle of superposition. Stress concentration factors are calculated for the ratio of inner and outer radii in the range 0–0.95 and are presented in tabular form.
TL;DR: In this article, three forms of bonded "gauge" are described which can be used for the determination of separate stresses on the surface of a stressed body from thermoelastic data only, without recourse to supplementary experimental or computational techniques.
Abstract: Three forms of bonded ‘gauge’ are described which can be used for the determination of separate stresses on the surface of a stressed body from thermoelastic data only, without recourse to supplementary experimental or computational techniques. The dimensions of the gauge, the gauge material and the form of bonding between the gauge and the stressed body are such that the thermoelastic signal from the gauge, in conjunction with that from the adjacent surface of the stressed body, allows the determination of the surface stresses in the stressed body in two orthogonal directions (e.g. parallel and normal to the ‘length’ direction of the gauge). The use of these gauges for the determination of the magnitudes and directions of the principal strains and stresses on the surface of the stressed body is also described.
TL;DR: In this article, two methods were developed for determining the stress intensity factors arising at the tip of a crack growing from a semicircular surface notch, based on the dislocation density method and boundary estimation.
Abstract: Two methods are developed for determining the stress intensity factors arising at the tip of a crack growing from a semicircular surface notch. The dislocation density method and boundary e...
TL;DR: For the dynamic inelastic response of structures subjected to impact, most work is concerned with the global response while little information is available about stresses and strains as mentioned in this paper, which is a limitation of our work.
Abstract: For the dynamic inelastic response of structures subjected to impact, most work is concerned with the global response while little information is available about stresses and strains. Furth...
TL;DR: In this article, the effects of collared versus collarless prostheses on cement mantle stresses in a model analysis of the proximal femur were investigated, showing that the collar causes an increase in proximal medial compressive longitudinal stresses, with other proximal stresses significantly reduced.
Abstract: Experimental and finite element analyses have attributed considerable significance to the role of the prosthetic collar in load transfer to the proximal femur ; however, some clinical evidence suggests that collar/calcar contact is unnecessary and detrimental. This study investigates the effects of collared versus collarless prostheses on cement mantle stresses in a model analysis of the proximal femur. Three-dimensional embedded strain gauging is used in a three-times full-size model of an implanted left femur. Tensor stresses in the cement mantle are derived for a collarless Exeter stem, a small and a large medial-collared stem and a full-collared prosthesis. Results show that the collar causes an increase in proximal-medial compressive longitudinal stresses, with other proximal stresses significantly reduced. Subsidence of the stem in the cement mantle is prevented, inducing unfavourable pivoting of the prosthesis about the calcar into varus. The collar type produces only minor additional effects in the mechanism of load transfer. The analysis suggests that collars may inhibit the prosthesis from attaining long-term secondary stability, by preventing the stem subsidence evident with cemented collarless implants. Derived stresses also illustrate the considerable variation in the mechanism of load transfer between collared and collarless prostheses in both the proximal and distal regions.
TL;DR: In this article, the large strain deformation behavior of particle-filled PET (polyethylene terephthalate) film has been investigated numerically in a parametric study employing the ABAQUS finite element solver.
Abstract: The large strain deformation behaviour of particle-filled PET (polyethylene terephthalate) film has been investigated numerically in a parametric study employing the ABAQUS finite element solver. The behaviour of PET has been modelled by Mooney-Rivlin rubber elasticity theory. The results of the parametric study show that small variations in the particle characteristics lead to significant differences in the surface characteristics, which are likely to change the friction and manufacturing properties of the film material.A simple methodology has been established for relating the particle characteristics to the surface properties. Process design rules have been developed, from which the surface characteristics can be determined from a knowledge of the particle characteristics. Good comparisons have been achieved between surface characteristics obtained numerically and those obtained from the simple design rules.
TL;DR: In this paper, the authors compared finite element predictions of strain and strain range for short flat bars with projections and values estimated using simple notch stress-strain conversion (NSSC) rules.
Abstract: This paper compares finite element predictions of strain and strain range for short flat bars with projections and values estimated using simple notch stress-strain conversion (NSSC) rules. Results of six geometries, associated with local and remote restraints and under both axial and shear loading conditions, are presented. Also, some previously published experimental and numerical results for other two-dimensional problems are compared with NSSC rule estimates and the findings discussed in association with the findings from the current work.The comparison has indicated that the choice of the most suitable NSSC rule is both geometry and load dependent. It is suggested that the intermediate rule with an m value of ∼ 0.6 may be more appropriate under extreme conditions of large stress concentration factor (generally associated with local restraints or loading) and high load.
TL;DR: In this paper, a novel testing technique has been employed to study the creep properties of ferritic steel weldments under shear loading, which allows examination of microstructurally distinct regions, such as the type IV region of the heat-affected zone, in relative isolation from adjacent material.
Abstract: A novel testing technique has been employed to study the creep properties of ferritic steel weldments under shear loading. The technique allows examination of microstructurally distinct regions, such as the type IV region of the heat-affected zone, in relative isolation from adjacent material. When results from the shear tests are compared with uniaxial data an appropriate stress for determining creep rupture under multi-axial loading may be deduced. The stress rupture behaviour of shear and uniaxial tests as a function of stress and temperature are consistent. It is suggested that this test technique deserves wider application for the examination of the creep properties of materials that are microstructurally inhomogeneous.
TL;DR: In this paper, the effects of the transverse joint load component in a model analysis of the proximal femur were investigated using three-dimensional embedded strain transducers in a three-times full-size model of an Exeter™ total hip replacement.
Abstract: Clinical studies have attributed considerable importance to the torsional loading of prosthetic femoral implants; however, the effect of this load has frequently been neglected in load simulations of the hip. The objective of this study, therefore, is to investigate the effects of the transverse joint load component in a model analysis of the proximal femur.Cement mantle stresses in a three-times full-size model of an Exeter™ total hip replacement were investigated using three-dimensional embedded strain transducers. Six sites were analysed for two separate loading configurations, namely the two-dimensionally loaded single-legged stance and the ‘toe off’ phase of gait which represents a three-dimensional hip reaction. Results showed a considerable variation in stem/cavity contact conditions due to the application of the transverse load component. Furthermore, large distal bending stresses are induced in the sagittal plane, with considerable shearing stresses due to torsion evident at all sites.The...
TL;DR: A method for finding crack tip stress intensity factors for cracks emanating from circular holes, and subject to arbitrary remote loading, is described in this article, where cases of single and multiple cracks are treated using the distributed dislocation approach.
Abstract: A method for finding crack tip stress intensity factors for cracks emanating from circular holes, and subject to arbitrary remote loading, is described. Cases of single and multiple cracks are treated, using the distributed dislocation approach.
TL;DR: In this article, the boundary integral equation (BIE) was used for three-dimensional shape design optimization with Coon's patches in order to represent continuously changing design surfaces, and two examples, a perforated plate under biaxial stresses and a cantilever beam with end shear loading, were demonstrated for smoothing of stress peaks and stress levelling.
Abstract: Three-dimensional shape design optimization is demonstrated using the boundary integral equation method. Design sensitivities are obtained directly by differentiating the boundary integral equations with respect to normals to the surfaces at the design variable points. Coon's patches are employed in order to represent continuously changing design surfaces. The Broyden-Fletcher-Goldfarb-Shanno (BFGS) method which requires first-order derivative information has been adopted for the optimization part of the problems. Two examples, a perforated plate under biaxial stresses and a cantilever beam with end shear loading, are demonstrated for the smoothing of stress peaks and stress levelling.
TL;DR: A detailed survey of the variations in crown curvature, knuckle curvature and thickness of a number of thin torispherical pressure vessel ends has shown that actual dimensions may differ significantly from nominal dimensions.
Abstract: A detailed survey (1-4)† of the variations in crown curvature, knuckle curvature and thickness of a number of thin torispherical pressure vessel ends has shown that actual dimensions may differ significantly from nominal dimensions.Numerical stress analysis using the finite element method has been carried out to assess the effects of these shape imperfections on the stresses in some of the thin torispherical pressure vessel ends considered in reference (4). The results have been compared with those for the corresponding perfect ends. In several cases significant increases in stress levels are predicted due to thickness and especially curvature variations.
TL;DR: In this article, four circular bolted joints with blank flanges were tested under static tension forces under different tension forces and preloads, and they were applied to the joints and bolt forces.
Abstract: Four circular bolted joints with blank flanges have been tested under static tension forces. Different tension forces and bolt preloads have been applied to the joints and bolt forces, disp...
TL;DR: In this paper, the three-dimensional problem concerning the transient thermal stress is theoretically analyzed by considering the thermomechanical coupling effect by means of the Laplace transformation and the generalized Fourier transformation.
Abstract: In this paper, the three-dimensional problem concerning the transient thermal stress is theoretically analysed by considering the thermomechanical coupling effect by means of the Laplace transformation and the generalized Fourier transformation. Numerical evaluation is carried out for the temperature distribution and the thermal stresses in an infinite plate heated by a local heat source that moves with constant velocity on the surface.
TL;DR: In this article, the ideas of continuum damage mechanics are incorporated into a model, based on the Cosserat theory of plates and a multi-axial version of Norton's creep law, which has been used recently to calculate the steady state creep strain rates in a weldment.
Abstract: Understanding more fully the behaviour of weldments is important since they can reduce the lifetime of structures at high temperatures, but performance factors are omitted from most existing design codes (with the exception of the high temperature fast reactor codes). Simple mathematical models which produce approximate solutions quickly are useful since they allow the design engineer to carry out rapid simulations. In this paper the ideas of continuum damage mechanics are incorporated into a model, based on the Cosserat theory of plates and a multi-axial version of Norton's creep law, which has been used recently to calculate the steady state creep strain rates in a weldment. Failure results are calculated numerically for a ferritic plate of constant thickness subject to uniaxial loading, the plate containing parent and weld metals, type IV material and a high-temperature heat-affected zone (HAZ). Results obtained for various material parameters and weldment configurations show that rupture times depend strongly on the choice of generalized stress in the damage evolution equation. The results also reveal that changes to the material strength of a region cannot be made in isolation if physically realistic results are to be obtained and, further, that early failures can occur if there are large differences in strength between the various parts of the weldment.
TL;DR: In this article, the strand constructions dealt with have almost invariably involved only wires which are circular in cross-section and there are, however, instances when shaped wires are used.
Abstract: In published literature, the strand constructions dealt with have almost invariably involved only wires which are circular in cross-section. There are, however, instances when shaped wires ...
TL;DR: In this article, the elastic-plastic behavior of short flat bars with projections subjected to monotonic and cyclic axial loading using finite element analysis was studied and the results were complementary to similar results for (a) shear loading and (b) combined axial and shear loads.
Abstract: This paper describes the results of a study of the elastic–plastic behaviour of short flat bars with projections subjected to monotonic and cyclic axial loading using finite element analysis. The results are complementary to similar results for (a) shear loading and (b) combined axial and shear loading. Six geometries are considered and elastic–plastic stress and strain data for both local and remote restraints are presented. These geometries and associated restraints result in elastic stress concentration factors in the range 1.69–4.96. A simple bilinear elastic–plastic material model is assumed and the results are normalized with respect to material properties so that they can be applied to geometrically similar components made from other materials which can be represented by the same material models.
TL;DR: In this article, explicit equations for the state of stress arising in an elastic solid when a frictionless conical indenter is pressed into the surface are given for the case where the indenter does not have an indenter.
Abstract: Explicit equations are given for the state of stress arising in an elastic solid when a frictionless conical indenter is pressed into the surface.