Showing papers in "Journal of Strain Analysis for Engineering Design in 1978"
TL;DR: In this article, a finite element analysis has been used to examine the effect of non-rigid adherends and a spew fillet in solid and annular butt joints for a range of geometries and adhesive properties.
Abstract: Axisymmetric butt joints are widely used as specimens for testing the response of adhesives to shear and tensile stresses. When analysing the results from these tests, the stress distributions must be accurately known. A finite-element analysis has been used to examine the effect of non-rigid adherends and a spew fillet in solid and annular butt joints for a range of geometries and adhesive properties. It has been shown that stress concentrations occur in butt joints loaded in tension; in the latter case, the stress concentration is directly due to the presence of the spew fillet.
77 citations
TL;DR: In this paper, a critical review of available information and models for crack propagation at elevated temperatures is provided, where the authors divide the behavior of crack propagation into brittle, ductile and plane stress conditions.
Abstract: The prediction of crack propagation rates at elevated temperatures is important and this paper provides a critical review of available information and models for behaviour. For simplicity, behaviour is divided into three situations. At one extreme, a brittle situation may exist in which the material is brittle and the degree of constraint high, so that substantially plane strain conditions exist and stress redistribution at the crack tip is small; in this situation, the fracture is a local crack tip event and the stress intensity may be of use in correlaiting creep crack propagation data. At the other extreme, ductile behaviour may result if the material is ductile and the constraint is low with plane stress conditions prevailing; in this case, stresses at and near the crack tip will redistribute quickly down to more even values and conventional creep analysis techniques using, say, the reference stress will be most useful, particularly for estimating times to rupture. It is postulated that there ...
67 citations
TL;DR: In this article, the authors determined the strain energy release rate for an edge crack in a uniformly stressed bar of circular cross-section using a finite-element representation of the bar.
Abstract: The strain-energy release rate is determined for an edge crack in a uniformly stressed bar of circular cross-section Values of the strain-energy release rate, obtained using a finite-element representation of the bar and by measuring the compliance of the bar experimentally, are shown to be in close agreement For crack depths of less than one-half diameter, the strain-energy release rates are found to be lower than existing results on rectangular bars having the same relative crack length
55 citations
TL;DR: In this paper, a three-parameter method for determining the stress intensity factor, K, from isochromatic fringe loops obtained from photoelastic models with sharp cracks is presented.
Abstract: Methods for determining the stress intensity factor, K, from isochromatic fringe loops obtained from photoelastic models with sharp cracks are briefly reviewed. A new three-parameter method is introduced which follows the two-parameter approach developed previously by Irwin. In the three-parameter method, three different terms in an analytical solution are adjusted to obtain a suitable match between the theoretical and experimental isochromatic loops. The three parameters are: K/√2πz, which describes the crack-tip singularity, (b) βK/√z, to account for variations in the stress field removed from the crack tip and (c) σoa = α1K/√2πa, which is added to the σx component of the stres field to account for the biaxiality of the far-field stresses.A relationship is derived for the maximum shear stress, τm, in terms of the three fitting parameters (K, α, and β) and the two geometric parameters (rm and θm) associated with the isochromatic fringe loops. A method of solution based on measurements of rm and θ...
47 citations
TL;DR: In this article, the authors extended Nadai's method for determining the shear stresses in solid cylindrical specimens subjected to torsional loads and proposed a simple approximation to this solution.
Abstract: Nadai's method for determining the shear stresses in solid cylindrical specimens subjected to torsional loads is extended to give the shear stresses in tubular specimens. A simple approximation to this solution is also proposed. Nadai's method may also be extended to anlyse the surface stresses of tubular specimens under combined axial and torsional loads.
39 citations
TL;DR: In this paper, the residual stresses in cold-formed, circular, steel tubes were analyzed on the basis of mathematical plasticity and the correlation between this analytical prediction and test results was satisfactory.
Abstract: Residual stresses in cold-formed, circular, steel tubes are analysed on the basis of mathematical plasticity. The correlation between this analytical prediction and test results is satisfactory.
36 citations
TL;DR: In this paper, the principles and development of the boundary integral equation (BIE) method for solving engineering problems are reviewed, with particular emphasis on applications in three-dimensional stress analysis.
Abstract: The principles and development of the boundary integral equation (BIE) method for solving engineering problems are reviewed, with particular emphasis on applications in three-dimensional stress analysis. Its use in problems of this type is illustrated with the aid of three examples, one a classical stress concentration problem, the other two involving cracked components. Compared with a finite-element method, the BIE approach is shown to be capable of being both more accurate and more economical to use in terms of competing resources required and the cost of data preparation. These advantages may, however, be less clear-cut when predictions of stresses and displacements at a large number of points within a component are required, or when the component concerned has a relatively high surface-to-volume ratio.
23 citations
TL;DR: In this paper, experimental techniques for investigating general yield surface behavior were described, and illustrative results for a 2 1/4 per cent Cr, 1 per cent Mo pressure-vessel steel.
Abstract: The Mises shear strain energy model has long been accepted as satisfactory for defining initial yield in the general three-dimensional stress state. For materials which strain-harden after initial yield, the situation is complex and subsequent yield surfaces will depend on the direction and level of pre-stress. This paper describes experimental techniques for investigating general yield surface behaviour, and presents illustrative results for a 2 1/4 per cent Cr, 1 per cent Mo pressure-vessel steel.
17 citations
TL;DR: In this paper, the numerical representation and differentiation of experimental information are extended to full-field capability involving two independent variables using Bicubic spline, regression analysis and finite element concepts.
Abstract: The numerical representation and differentiation of experimental information is extended to full-field capability involving two independent variables. Bicubic spline, regression analysis and finite-element concepts are employed. Smoothing of the experimental data is accomplished mathematically. The technique are demonstrated by analysing loaded plates.
13 citations
TL;DR: In this paper, a series of fatigue crack growth tests have been conducted on sheet specimens of thicknesses 3, 6, 16 and 22 mm under both random and constant amplitude loading for a number of different mean stress levels.
Abstract: A series of fatigue crack growth tests have been conducted on sheet specimens of thicknesses 3, 6, 16 and 22 mm. These tests have been under both random and constant amplitude loading for a number of different mean stress levels.The results from these tests have shown that the resistance to fatigue crack growth increases as the thickness increases at low growth rates. In contrast, at high growth rates this behaviour is reversed. Both random and constant amplitude data showed this feature. Crack-closure measurements have been used in an attempt to explain these differences in behaviour for high and low growth rates.The random and constant amplitude test results have been correlated successfully for square-mode growth, using a ‘weighted’ average range approach.
12 citations
TL;DR: In this paper, a detailed study of a turbine disc design is presented, based on a statistical approach using the Weibull probability distribution, and requires the evaluation of a stress integral over the volume or suface area of the component.
Abstract: A general procedure for the assessment of the failure probability of a stressed ceramic component is illustrated by a detailed study of a proposed turbine disc design. The procedure is based on a statistical approach using the Weibull probability distribution, and requires the evaluation of a stress integral over the volume or suface area of the component. The stress distributions in this case are obtained from a three-dimensional analysis of a photelastic model of the disc. The proposed design is critically appraised in the light of the derived stress integrals. The variation of failure probability with speed is illustrated and the effects of changes in the material properties of the prototype disc are quantitatively assessed.
TL;DR: In this article, the effect of a decrease in stress range on fatigue crack propagation behavior in mild-steel plate is investigated and an experimentally determined equation relating the threshold stress intensity factor to stress intensity history is introduced and is seen to be a function of specimen thickness, which determines the crack tip stress.
Abstract: The effect of a decrease in stress range on fatigue crack propagation behaviour in mild-steel plate is investigated.An experimentally determined equation relating the threshold stress intensity factor to stress intensity history is introduced and is seen to be a function of specimen thickness, which determines the crack tip stress—strain state. The delay period between the arrest of a stage II crack and its re-propagation is also a function of stress history and specimen thickness. The effect of increasing the initial high values of stress intensity is to cause the delay period and the threshold stress intensity to increase, both of which are beneficial, i.e. they increase fatigue lifetime.
TL;DR: In this article, the Berger method was applied to the large thermal bending of sandwich plates, and the governing field equations were derived by the variational calculus for a thermal stress field when reduced strain energy was used, and they were formulated quasi-linearly with respect to the deflection and the differences of inplane displacements on each face.
Abstract: In order to apply the Berger method to the large thermal bending of sandwich plates, a modified method which employs average face strains is presented. The governing field equations are derived by the variational calculus for a thermal stress field when reduced strain energy is used, and they are formulated quasi-linearly with respect to the deflection and the differences of in-plane displacements on each face. As in the case of elastic plates, we may analyse sandwich plates that undergo thermal effects as well as mechanical loading with relative ease by the present method.
TL;DR: In this paper, the anisotropy of flexural stiffness has been examined at low strain using ASTM bar and 3mm and 6mm thick edge-gated disc injection mouldings for two glass-fibre-reinforced thermoplastics (GFTP).
Abstract: 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.
TL;DR: A series of tests was performed in which short lengths of square thin-walled steel box section to a model scale were tested to failure under combined bending and compression in a stiff loading rig as discussed by the authors.
Abstract: A series of tests was performed in which short lengths of square thin-walled steel box section to a model scale were tested to failure under combined bending and compression in a stiff loading rig. The design of the rig, the method of manufacture of the specimens, and the nature of the instrumentation are all discussed. The results illustrate the weakening effect of local buckling at large width/thickness ratios, and are compared with an approximate theoretical analysis recently presented by the author. A surprising result is that ten of the twenty-two specimens tested were stronger than predicted by simple plastic theory.
TL;DR: In this paper, a new grid-transferring technique is introduced that allows the strain analysis of flat or curved surfaces of single or double curvature, which is specially suitable for the solution of problems of finite deformation of flexible structures.
Abstract: A new grid-transferring technique is introduced that allows the strain analysis of flat or curved surfaces of single or double curvature. The technique consists of transferring a grid from the structure to a flat surface by means of a thin, adhesive, transparent ribbon. Information is obtained along a strip, or point-by-point when circles or rosettes are used. The technique is specially suitable for the solution of problems of finite deformation of flexible structures, and its threshold strain is about 0.004. As a verification of the new method, strains obtained on a disc under diametral compression are compared with results already given in the literature. As a general example of application, strains on the anticlastic surface of tubes with and without perforation, and turned inside out, are determined. The method is not influenced by rigid-body motions.
TL;DR: In this paper, a set of influence functions is developed for the complete, uniform, circular ring, subjected to concentrated forces or moments, and equilibrium is satisfied by the introduction of fictitious supports that are self-cancelling when the applied force system is in equilibrium.
Abstract: A set of influence functions is developed for the complete, uniform, circular ring, subjected to concentrated forces or moments. Equilibrium is satisfied by the introduction of fictitious supports that are self-cancelling when the applied force system is in equilibrium. The method provides a general solution for the circular ring on a statically determinate support.
TL;DR: In this article, an attempt is made to obtain photoelastically the stress distribution in the near vicinity of singular points, when a punch is indenting an elastic half-plane.
Abstract: An attempt is made to obtain photoelastically the stress distribution in the near vicinity of singular points, when a punch is indenting an elastic half-plane. The punch is to be assumed flat and rough so that friction is developed between the contact surfaces. By expanding the complex stress function into a Taylor series, an extrapolation law is obtained, which allows the calculation of stresses at the vicinity of the singular points by means of photoelastic measurements at positions remote from these points. The error limits of this technique are defined and, finally, a relation between the order of singularity and the parameters of the photoelastic pattern is established.
TL;DR: In this paper, a new experimental method is presented for determining trajectories of flow for non-steady-state processes which exhibit geometric similarity (quasisteady state processes (1)∗).
Abstract: A new experimental method is presented for determining trajectories of flow for non-steady-state processes which exhibit geometric similarity (quasi-steady-state processes (1)∗). One process that is normally regarded as quasi-steady-state (plane strain wedge indentation) is investigated using this method. It is shown that this process satisfies the requirements of geometric similarity within experimental accuracy. Results are presented for wedge angles of 30°, 60° and 90° and a range of indentation depths up to approximately 3 mm.Finally, it is suggested how this method can be combined with well-known orthogonal-grid techniques to provide information for the calculation of effective strains throughout the deforming region.
TL;DR: In this article, the authors used dynamic relaxation to analyse square plates at large deflections according to the Foeppl and Von Karman theories and quantified their asymptotic nature and the effect of variable thickness.
Abstract: Dynamic relaxation is used to analyse square plates at large deflections according to the Foeppl and Von Karman theories. The results quantify their asymptotic nature and the effect of variable thickness.
TL;DR: In this article, a method of quasistatic energy analysis for characterizing the fracture behavior of a slender D.C.B. specimen having two parallel beam arms of low bending stiffness was presented.
Abstract: 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 dG/da. Negative dG/da was attained by contaminating portions of an uncracked specimen, and unstable crack propagation was observed experimentally in the contaminated regions.
TL;DR: In this article, brittle-lacquer and strain-gauge methods and finite element analysis were used to determine stress distributions in a simplified model and an actual centrifugal fan impeller.
Abstract: Brittle-lacquer and strain-gauge methods and a finite-element analysis are used to determine stress distributions in a simplified model and an actual centrifugal fan impeller.
TL;DR: In this paper, the authors examined the residual shear stress in scragged torsion bars and found that the thickness of the layer removed is restricted if the "mean stress at mean radius" assumption is to be valid.
Abstract: 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.
TL;DR: In this paper, a unified interpretation of interferometric and holographic fringe patterns obtained from birefringent materials is presented by using physical concepts only, and the two fundamental fringe systems, corresponding to the individual stress-optical retardations along the principal stress directions, are considered to recombine mechanically for the formation of isochromatic and isopachic fringe patterns.
Abstract: A unified interpretation of interferometric and holographic fringe patterns obtained from birefringent materials is presented by using physical concepts only. The two fundamental fringe systems, corresponding to the individual stress-optical retardations along the principal stress directions, are considered to recombine mechanically for the formation of isochromatic and isopachic fringe patterns. This mechanical interference is shown to be more pronounced only when certain conditions concerning the position and the spatial frequencies of the original systems are satisfied. It is shown that only one of the isochromatic and isopachic fringe patterns, corresponding to the shorter diagonals of the individual quadrangles, formed by the two initial fundamental fringe systems, is obtained under normal experimental conditions, and that it is possible to have in one region of the pattern one system and in another region the other. Both isochromatics and isopachics can be obtained only when special precauti...
TL;DR: In this paper, the effect of additional notches or holes in relieving the maximum concentration of stress in notched machine elements was investigated for bars and shafts of circular cross-section subjected to tensile, bending and torsional loadings.
Abstract: In many designs, it is desirable to economize in weight and minimize stress concentration. After a general demonstration of the effect of additional notches or holes in relieving the maximum concentration of stress in notched machine elements, extensive quantitative investigations were made for bars and shafts of circular cross-section subjected to tensile, bending and torsional loadings.
TL;DR: In this article, the influence of nonhomogeneity and density on the normal stresses and shear stresses developed due to the acceleration of a disc, of varying thickness, at any particular instant, are analysed.
Abstract: The influences of non-homogeneity and density on the normal stresses and shear stresses developed due to the acceleration of a disc, of varying thickness, at any particular instant, are analysed. Yield loci, on the basis of von Mises' criterion, are found for discs of varying thickness and uniform thickness with a bore ratio (a/b) of 0.25 and also for linearly varying (p = 1.0, q = 1.0) and nonlinearly varying (p = 0.5, q = 0.5) density and homogeneity. A homogeneous, uniform density and uniform thickness disc forms a special case of the analysis.
TL;DR: In this article, a correlation study has been made to evaluate the effectiveness of finite-element modelling for the stress analysis of composite-material laminates, and a quadratic strain traingular (QST) finite element has been used for the analysis.
Abstract: A correlation study has been made to evaluate the effectiveness of finite-element modelling for the stress analysis of composite-material laminates. The specific problems studied are: a boron—epoxy composite laminate with a circular hole under axial tension; a boron—epoxy composite laminate with an elliptical opening under axial tension; a glass-fibre-reinforced plastic plate subjected to line load; and a glass-fibre-reinforced plastic annular disc under diametrical compression. Correlations of finite-element predictions are made with analytical solutions and experimental data. The study has demonstrated the accuracy of finite-element modelling employing a quadratic strain traingular (QST) finite-element for the stress analysis of composite-material laminates.
TL;DR: The Tokyo International Conference on Pressure Wessels as mentioned in this paper attracted 400 delegates from all over the world, and more than 100 papers were presented in parallel sessions on a wide variety of pressure-wessel topics; there were also "panel sessions" for the discussion of specific topics.
Abstract: This conference, held in Tokyo in April 1977 and organized by the Japanese Organizing Committee, with the support of A.S.M.E., I. Mech E. and a European Participation Committee, attracted 400 delegates from all over the world. More than 100 papers were presented in parallel sessions on a wide variety of pressure-wessel topics; there were also ‘panel sessions’ for the discussion of specific topics. The classification of the numerous and diverse topics covered in the papers was not easy and there were inevitably omissions and misfits in the contents of the sessions. This review covers the papers presented in the sessions on Analysis and Design, Seismic Analysis and Dynamics, and Creep; some of the original groupings have been retained, but an attempt has been made to bring the papers more effectively together into well-defined sets.