Showing papers in "Journal of Strain Analysis for Engineering Design in 1994"
TL;DR: In this paper, a number of mechanisms-based constitutive equations were assessed in an effort to describe the creep behaviour of an aluminium alloy at 150°C, and it was found that a sinh function of stress, r...
Abstract: A number of mechanisms-based constitutive equations were assessed in an effort to describe the creep behaviour of an aluminium alloy at 150°C. It was found that a sinh function of stress, r...
171 citations
TL;DR: In this article, the authors investigated the three-dimensional nature of the state of deformation in a single-lap test specimen in a linear elastic finite element analysis in which the boundary conditions account for the geometrically nonlinear effects.
Abstract: The three-dimensional nature of the state of deformation in a single-lap test specimen is investigated in a linear elastic finite element analysis in which the boundary conditions account for the geometrically non-linear effects. The validity of the model is demonstrated by comparing the resulting displacement fields with those obtained from a moire inteferometry experiment. The three-dimensional adherend and adhesive stress distributions are calculated and compared with those from a two-dimensional non-linear numerical analysis, Goland and Reissner's solution, and experimental measurements. The nature of the three-dimensional mechanics is described and discussed in detail. It is shown that three-dimensional regions exists in the specimen, where the adherend and adhesive stress distributions in the overlap near (and especially on) the free surface are quite different from those occurring in the interior. It is also shown that the adhesive peel stress is extremely sensitive to this three-dimensiona...
49 citations
TL;DR: In this paper, the axial and torsional wire stiffnesses of helical cables are analyzed using a parametric approach with a wide range of cable diameters and lay angles, and the range of validity of various approaches used for analysing helical cable stiffnesses is examined.
Abstract: Using theoretical parametric studies covering a wide range of cable (and wire) diameters and lay angles, the range of validity of various approaches used for analysing helical cables are critically examined.Numerical results strongly suggest that for multi-layered steel strands with small wire/cable diameter ratios, the bending and torsional stiffnesses of the individual wires may safely be ignored when calculating the 2 × 2 matrix for strand axial/torsional stiffnesses. However, such bending and torsional wire stiffnesses are shown to be first order parameters in analysing the overall axial and torsional stiffnesses of, say, seven wire stands, especially under free-fixed end conditions with respect to torsional movements.Interwire contact deformations are shown to be of great importance in evaluating the axial and torsional stiffnesses of large diameter multi-layered steel strands. Their importance diminishes as the number of wires associated with smaller diameter cables decreases.Using a modifie...
37 citations
TL;DR: In this article, the authors considered the crushing which occurs in a spherical shell made of ductile material on striking a rigid wall and developed a static analysis which allows for strain hardening.
Abstract: This paper considers the crushing which occurs in a spherical shell made of ductile material on striking a rigid wall. A static analysis is developed which allows for strain hardening, whil...
34 citations
TL;DR: In this paper, the use of Creep Continuum Damage Mechanics (CDM) in design analysis has been discussed, and it is shown how this approach has the capability to model the deformation and rupture.
Abstract: The common theme of this paper is the use of Creep Continuum Damage Mechanics (CDM) in design analysis. It is shown how this approach has the capability to model the deformation and rupture...
33 citations
TL;DR: Experimental studies on the influences of orientation on the elastic behavior at 20°C and 950°C of the single crystal nickel base supera... as mentioned in this paper showed that the low cycle fatigue creep properties at 1000°C were affected by orientation.
Abstract: 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 supera...
32 citations
TL;DR: The application of numerical methods, particularly the Finite Element (FE) method, is widespread in the analysis and design of components operating at elevated temperatures as discussed by the authors, and a brief overview of the FE method and the Boundary Element (BE) method is presented.
Abstract: The application of numerical methods, particularly the Finite Element (FE) method, is widespread in the analysis and design of components operating at elevated temperatures. A brief overview of the FE method and the Boundary Element (BE) method is presented. To demonstrate the versatility and accuracy of FE solutions in modelling practical engineering problems, several examples are presented. The examples include indentation creep involving the reference stress approach, the use of damage mechanics, and creep crack propagation simulation. The FE solutions are shown to be in good agreement with analytical and experimental results.
32 citations
TL;DR: The scope and methodology of R5 are compared with those of existing and proposed high-temperature design codes and it is suggested that the R5 approach may be considered a generalization of existing methods.
Abstract: The R5 procedure for assessing the high-temperature response of structures is described and recent progress highlighted. The scope and methodology of R5 are compared with those of existing and proposed high-temperature design codes. For defect-free components, R5 provides a shakedown approach intermediate between the elastic and inelastic routes in codes. As the codes give interaction diagrams based on shakedown concepts for particular loading circumstances, the R5 approach may be considered a generalization of existing methods. For defective components, the Reference stress methods recommended in R5 are described. Proposals for the incorporation of similar approaches in other codes are currently being considered, and these are also described.
31 citations
TL;DR: In this article, the effects of the clearance between pin and hole, the pin load magnitude, the contact condition, and the relative pin/lug rigidities etc. were investigated.
Abstract: Stress analyses are performed using the finite element method (FE) for a lug under various conditions. The effects of the clearance between pin and hole, the pin load magnitude, the contact condition, and the relative pin/lug rigidities etc. are investigated. The effect of some durability improvement techniques, such as interference fitting, bushing, and cold working are also investigated. Significant results are obtained which can improve both the understanding of the stress state in a lug and the design of a durable lug.
24 citations
TL;DR: In this paper, the limitations of traditional methods of providing long-term creep design data are discussed in relation to existing national and international testing standards, current parametric procedures for extrapolation of stress-rupture values and the factors affecting the high degree of scatter in conventional longterm property sets for widely-used structural steels.
Abstract: The limitations of traditional methods of providing long-term creep design data are discussed in relation to existing national and international testing standards, current parametric procedures for extrapolation of stress-rupture values and the factors affecting the high degree of scatter in conventional long-term property sets for widely-used structural steels. These deficiencies may be overcome by adopting an alternative data acquisition methodology based on the analysis of short-term high-precision constant-stress creep curves.
23 citations
TL;DR: In this paper, a review of fracture mechanics concepts required to describe high temperature components may fail by crack growth, net-section rupture, or some combination of both processes, and procedures are presented for evaluating relevant characterizing parameters using experimental, numerical and limit analysis methods.
Abstract: Cracked high temperature components may fail by crack growth, net-section rupture, or some combination of both processes. This paper reviews the fracture mechanics concepts required to describe this behaviour. Procedures are presented for evaluating relevant characterizing parameters using experimental, numerical and limit analysis methods. Models for predicting crack propagation rates from uni-axial creep data involving ductility exhaustion in a process zone at a crack tip are outlined. Both the influence of build-up of damage in the process zone and material deterioration in the uncracked ligament are considered. It is shown that the models give satisfactory correlations with experimental data.
TL;DR: In this article, a numerical study of the stress distribution in pin-loaded tubes was performed and it was found that there are considerable differences between the stresses at the inner and outer surfaces of the tube which arise because the region around the pin and towards the open end of the tubes ovalizes.
Abstract: This paper describes a numerical study of the stress distribution in pin-loaded tubes. The effects of (a) the distance from the pin to the open end, (b) the variation in pin diameter, (c) the variation of tube thickness and (d) the variation in pin fit on the radial and circumferential stresses around the pin hole have been found and discussed. It is found that there are considerable differences between the stresses at the inner and outer surfaces of the tube which arise because the region around the pin and towards the open end of the tube ovalizes. This ovalization is more pronounced for a small head distance, a smaller diameter pin, a thinner tube and a clearance fit. The results for the pin-loaded tube are compared with those for a pin-loaded lug and it is shown that there are many similarities in the stress patterns.
TL;DR: In this paper, the authors used neutron diffraction to map the local stress variation surrounding a 13 mm diameter blind hole defect in a section of pipeline subjected to an applied bending stress, and compared the experimentally measured results and local stress predictions based on a two-dimensional analytical model as well as on three-dimensional finite element calculations.
Abstract: Neutron diffraction was used to map the local stress variation surrounding a 13 mm diameter blind-hole defect in a section of pipeline subjected to an applied bending stress. Comparison was made between the experimentally measured results and local stress predictions based on a two-dimensional analytical model as well as on three-dimensional finite element calculations. The two-dimensional analytical model proved to be unsatisfactory, predicting very large local stress variations at the defect edge which were not observed experimentally. Conversely, the three-dimensional model reflected all of the significant trends observed experimentally, although predicted stress levels were lower than the measured values due to limitations with the finite element package.
TL;DR: In this paper, the authors present a review of existing methods for creep life assessment with particular reference to those based on component strain measurement and conclude that consolidation of the substantial amount of information now available must be an objective for the next 5-10 years, whilst not curtailing innovative development.
Abstract: Over the past ten years significant progress has been made towards reliable methods for creep life assessment. Through development and application, methods are now at a stage at which their technical viability is established and the cost benefits are proven at the plant operation, maintenance, and strategic planning levels. This paper reviews creep life assessment methods with particular reference to those based on component strain measurement. It is concluded that, through validation, standardization, and data/knowledge banking, consolidation of the substantial amount of information now available must be an objective for the next 5–10 years, whilst not curtailing innovative development.
TL;DR: In this article, a simple technique to establish rate dependent stress-strain properties for metallic materials is presented, which takes account of the effects of strain, strain hardening, strain rate, inertia, and temperature.
Abstract: This paper outlines a simple technique to establish rate dependent stress-strain properties for metallic materials. The materials considered are commercially pure copper and mild steel. The deformation of materials at high strain rate leads to the conversion of mechanical energy into heat. The temperature rise produced during these processes can be significant and can lead to phase transformation. A combined experimental and numerical technique has been used to establish the one-dimensional constitutive equation, which takes account of the effects of strain, strain hardening, strain rate, inertia, and temperature.
TL;DR: In this article, the authors discuss the charcteristics of creep deformation and the requirements of any creep equation developed to quantify this behavior, and show how the Graham and Walles methodology fulfils the identified objectives and how the equations have been applied to simple and complex variable loading situations.
Abstract: The paper briefly discusses the charcteristics of creep deformation and the requirements of any creep equation developed to quantify this behavior. It is shown how the Graham and Walles methodology (1)† fulfils the identified objectives and how the equations have been applied to simple and complex variable loading situations.By reference to an appropriate blade alloy it will be shown that the approach can be extended to produce deformation maps and the results will be compared with theoretical creep models such as dislocation shearing of precipitate particles.Finally it is shown how the Graham and Walles model has been applied to single crystal materials to predict creep in randomly oriented crystals.
TL;DR: In this article, an automated fringe pattern analysis enables the full field of data to be used with the minimum of operator intervention, and is shown to be accurate to within 10 per cent.
Abstract: Electronic speckle pattern interferometry has been used to calculate KI and J for compact tension specimens. Automated fringe pattern analysis enables the full field of data to be used with the minimum of operator intervention. Measurements are shown to be accurate to within 10 per cent. The J-measurement procedure employed could form the basis of an automatic fault detection system.
TL;DR: In this paper, the deformation of three-dimensional elastic-plastic aluminium strips when they undergo symmetric rolling with a rigid body roller was studied, based on the theory of large deformation and large strain, using the updated Lagrangian formulation (ULF) and the incremental method.
Abstract: This study focuses on the deformation which occurs in three-dimensional elastic-plastic aluminium strips when they undergo symmetric rolling with a rigid body roller. This research is based on the theory of large deformation and large strain, using the updated Lagrangian formulation (ULF) and the incremental method to develop the analysis model of the three-dimensional elastic-plastic characteristic of aluminium strip rolling.As for the determination of the direction of tangential friction force, this study also develops a modification algorithm to adjust to the three-dimensional rolling process. In addition, another rule is devised to identify the neutral point in order to further develop the theoretical model and computer program for the large deformation finite element method with the two-order strain rate equation.Finally, this study uses the numerical analysis model developed in this research to simulate the deformation which occurs in aluminium strips when they undergo symmetric rolling, and...
TL;DR: In this paper, a finite element model is constructed, reversing the machining sequence, matching the increments in measured strain, and thus cumulatively arriving at the original distribution of residual stress.
Abstract: The aim of this work is to develop a procedure for determining the three-dimensional residual stress fields in forged cylindrical pressure vessels. The procedure involves the destructive machining of the cylinder. Strain gauges record the strain variation on the outer surface of the cylinder as the inner surface is machined. A finite element model is then constructed, reversing the machining sequence, matching the increments in measured strain, and thus cumulatively arriving at the original distribution of residual stress. Examples include a numerical simulation for a thick disk and a practical application to thick-walled forged cylinders.
TL;DR: In this article, the finite element method has been used to obtain stress concentration factor data for flat ‘T’ shaped components, subjected to axial and shear loading, with both remote and local restraints being applied.
Abstract: The finite element method has been used to obtain stress concentration factor data for flat ‘T’ shaped components, subjected to axial and shear loading, with both remote and local restraints being applied. The ratio of length to depth (or slenderness ratio) of the shank region is generally less than 3:1. For these short components under shear (or bending) loads, primary bending stresses are no longer dominant and transverse shear is an important secondary effect.Comparisons are made between the predictions with remote and local restraints in order to quantify the effect of localizing the restraints (or load).
TL;DR: In this paper, the notched beam in asymmetric four-point bending has been analyzed using the finite element method and the results show that for brittle materials a stress concentration at or near the notch tip will cause the specimens to fail in the original configuration.
Abstract: A reliable test in which the stress state approximates that of pure shear is necessary in order to establish a valid failure criterion for brittle materials. One of the possible tests, the notched beam in asymmetric four-point bending, has been analysed using the finite element method. The results show that for brittle materials a stress concentration at or near the notch tip will cause the specimens to fail in the original configuration. A modified version of the test has been developed, which involves the enlargement of the notch angle and the rotation of the beam so that it is loaded with the notches lying in the direction of the loads. The new configuration was applied to graphite specimens which showed a distinctive mode of fracture.
TL;DR: In this paper, the mechanical properties necessary to characterize non-linear component behaviour are defined and presented for some chill-cast lead alloys at 20°C, when normalized, they are shown to be sufficiently similar to structural steels to allow the prediction of prototype response from model tests.
Abstract: The objective of this paper is to show that there are model materials which can be used to develop better assumption to improve theories, to verify the applicability of theories, or to get creep information which is otherwise unobtainable.The mechanical properties necessary to characterize non-linear component behaviour are defined and presented for some chill-cast lead alloys at 20°C. When normalized, they are shown to be sufficiently similar to structural steels to allow the prediction of prototype response from model tests. This paper also describes the methods used to make lead alloy models for the experimental study of creep of components.
TL;DR: In this article, a portabe system is constructed to demonstrate the use of an electro-optic heterodyne technique on a single point, single component of strain basis, and the prospect of expanding the setup to enable whole-field strain tensor evaluation is also discussed.
Abstract: Moire interferometry is increasingly being applied to investigations in experimental mechanics. The present work seeks to address the problem of automated ‘real-time’ analysis of interferometric Moire fringe patterns to obtain strain values. To this end, a portabe system is constructed to demonstrate the use of an electro-optic heterodyne technique on a single point, single component of strain basis. The prospect of expanding the setup to enable whole-field strain tensor evaluation is also discussed.
TL;DR: A model based on continuum theory for describing the cyclic deformation behavior of grey cast iron under multi-axial loading is presented and compared with test results obtained from strain-controlled tension/torsion tests as mentioned in this paper.
Abstract: A model based on continuum theory for describing the cyclic deformation behaviour of grey cast iron under multi-axial loading is presented and compared with test results obtained from strain-controlled tension/torsion tests. The unsymmetrical stress-strain response of cast irons under tension and compression is modelled by taking into account the opening and closing of graphite flakes, the bulk stress of cast iron being directly related to the internal stress acting on the steel matrix. Predictions are compared with experimental results obtained from proportional and non-proportional biaxial tests. The method is simple yet able to describe the essential features of the deformation of grey cast iron, and can be easily integrated with existing elasto-plastic constitutive models.
TL;DR: In this paper, the difference in the fatigue behavior of non-load-carrying and loadcarrying fillet welded cruciform joints was studied, theoretically, and the results showed that the non-loading fillet joints gave 5 per cent higher fatigue life than the load-carving fillet.
Abstract: An attempt has been made to study, theoretically, the difference in the fatigue behaviour of non-load-carrying and load-carrying fillet welded cruciform joints. In the former case, the pre-existing flaws produced during the welding process will always propagate from the weld toe. Accurate stress analysis using the boundary element method on the load-carrying fillet welded cruciform joints shows that the weld throat, h, should not be less than 1.414T, or the weld leg length, w, should not be less than 2.0T, where T is the main plate thickness, for the cracks to initiate from the weld toe. Furthermore, the values of Mk, the correction factor to take into account the presence of the weld, are found to decrease when the weld size is increased for the load-carrying fillet welded joints. The Paris crack propagation law is then computed numerically to obtain the S/N (signal-to-noise) curves for the two welded joints. The non-load-carrying fillet welded joints give 5 per cent higher fatigue life than the ...
TL;DR: In this paper, a destructive procedure for the determination of longitudinal residual stress distribution in a thin layer in the vicinity of the running surface of a rail head and the neighbouring area of rail cross-section is presented.
Abstract: This paper presents a destructive procedure for the determination of longitudinal residual stress distribution in a thin layer in the vicinity of the running surface of a rail head and the neighbouring area of rail cross-section. Wheel passages on the track produce plastic deformation in the running surface layer and thereby create a strong compression with a sharp stress gradient in the layer. This longitudinal stress distribution is a very important component of the stress pattern and strongly influences crack propagation in the rail head.
TL;DR: Creep constitutive equations are discussed in their role as material descriptions forming one of the governing conditions of an inelastic stress analysis, and some hints are given for the analyst who may be faced with performing this task for materials of interest.
Abstract: Creep constitutive equations are discussed in their role as material descriptions forming one of the governing conditions of an inelastic stress analysis. The view taken is that they must not only give an adequate picture of the material behaviour itself, but must also be suitable from the numerical point of view. Furthermore, in practical engineering contexts, constitutive equations must be principally aimed at giving information for structural assessment under realistic loading conditions and subject to various uncertainties. The choice of model is, therefore, not aimed at an exact material description, and the practial choice may be problem-dependent for a given material.Both the classical formulation and the more recent unified formulation are outlined, with discussion of advantages and disadvantages. Some unified formulations are regarded as practically useful but great use is still to be expected of classical forms in which creep and plasticity are regarded as separate. In the latter class d...
TL;DR: In this paper, an axisymmetric, bar-type specimen, which contains conical, "crack-like" external flaws, is described and used to obtain mixed-mode (I, II, and III) fracture data.
Abstract: An axisymmetric, bar-type specimen, which contains conical, ‘crack-like’, external flaws, is described. The specimen can be used to obtain mixed-mode (I, II, and III) fracture data. These ‘crack-like’ flaws can be created in metallic and non-metallic materials by incorporating metal or ceramic shims in moulds used to cast the components.Mode I and mode II crack tip conditions are created in the specimen by subjecting it to an axial load, while mode III crack tip conditions are produced by applying a torsional load. Finite element analyses are performed and results are presented which enable the KI, KII, and KIII values to be determined from the axial load, the torque, the bar diameter, the crack length, and the crack inclination.
TL;DR: In this article, internal pressure tests were conducted over several hundreds of cycles at pressures up to and in excess of the calculated proof test pressure on two nominally identical, stainless steel type 316 flush 90 degrees pressure vessel nozzles, designed and manufactured to BS 5500.
Abstract: Cyclic internal pressure tests were conducted over several hundreds of cycles at pressures up to and in excess of the calculated proof test pressure on two nominally ‘identical’, stainless steel type 316 flush 90 degrees pressure vessel nozzles, designed and manufactured to BS 5500. Prior to this pressure cycling, one vessel was subjected to the required proof test of 1.25 times the design pressure. Significant incremental straining was recorded in the non-proof tested vessel during cycling at all pressures above the first yeild pressure (0.336 × design pressure). For the proof tested vessel significant incremental straining was not recorded during cycling until 15 percent above the design pressure.
TL;DR: In this paper, a number of programmes that were undertaken by the Central Electricity Generating Board to ensure the continued safe operation of welded pipework components in such plant were described.
Abstract: The integrity of components operating in steam generating plant at elevated temperatures and pressures must be assured as they approach their design lives, of if they are found to contain defects. This paper describes a number of programmes that were undertaken by the Central Electricity Generating Board to ensure the continued safe operation of welded pipework components in such plant. The work described examines the behaviour of nominally sound and defective welded pipework as well as a specific case involving the testing of a component removed from fossil-fired plant. In each case, the results arising from the work are discussed in terms of the assessment and appraisals that may be applied to operating plant.