Showing papers in "Journal of Strain Analysis for Engineering Design in 1984"
TL;DR: In this paper, the influence of uniform residual stresses on measured hardness value was investigated experimentally, using samples containing a known cylindrical stress value, and it was shown that realistic v...
Abstract: The influence of uniform residual stresses on measured hardness value is investigated experimentally, using samples containing a known cylindrical stress value. It is shown that realistic v...
56 citations
TL;DR: In this article, an upper bound technique for the evaluation of the shakedown limit of thin cyclindrical shells subject to thermal loading is described. But this technique is based upon the upper bound kinematic shakedown theorem of Koiter.
Abstract: This paper describes an upper bound technique for the evaluation of the shakedown limit of thin cyclindrical shells subject to thermal loading. The method is based upon the upper bound kinematic shakedown theorem of Koiter. By suitable choice of displacement field, in a finite element form, and yield surface, the problem is reduced to a linear programming problem. A number of solutions are presented involving a tube subjected to a moving temperature front which indicates that the technique provides, in an efficient way, a complete description of the load levels at which ratchetting would occur and the corresponding modes of deformation. The technique seems therefore, to provide a useful intermediary between the use of the simple rules incorporated in design codes and full inelastic analysis.
33 citations
TL;DR: In this paper, the authors determined the stress and strain of circumferentially notched round bars having several specimen notch geometries representing different degrees of constraint and found that the notch to net-section radius ratio has a greater influence on the degree of constraint than the notch depth ratio.
Abstract: Stresses and strains occuring during creep were determined for circumferentially notched round bars having several specimen notch geometries representing different degrees of constraint. The specimen geometries and the material data used in the calculations were those pertaining to a parallel experimental investigation. It was found that, for the wide notch specimens, the notch to net-section radius ratio has a greater influence on the degree of constraint than the notch depth ratio. For the thin slit specimen, the small slit tip radius to net section radius ratio caused a big difference in stress distribution from that for the wide notch specimen of the same net-to-gross radius ratio. Global and local events were distinguished by the change of notch sharpness: for the relatively wide notch, creep was mainly a global process, whereas for the sharp slit, the creep process remained in a very local region near the slit tip. Various indicators for the degree of constraint are discussed, of which the t...
32 citations
TL;DR: In this paper, the merits of the various fracture criteria are reviewed and the biaxial loading effect on the parameter used in each criterion for the prediction of the fracture behaviour is studied.
Abstract: The angled crack problem has been of growing interest to both designers and researchers for the prediction of the structural integrity of components under complex loading conditions. In the study of angled crack growth behaviour, it is invariably of interest to predict the initial crack growth direction θ0 and the fractures stress σc at which crack initiation occurs.In this paper the merits of the various proposed fracture criteria are reviewed. The biaxial loading effect on the parameter used in each criterion for the prediction of the fracture behaviour is studied. It is observed that the popular testing method employing uniaxial loading of a test specimen is inadequate to demonstrate the suitability of fracture criteria in the prediction of θ0 and σc. It is suggested that with the biaxial loading of a test specimen with an angled crack, a better appraisal of the fracture criteria can be obtained. The experimental results obtained in this study seem to support the maximum stress criteria for bot...
26 citations
TL;DR: In this article, the authors compared various methods for the determination of stress intensity factors from photoelastic data obtained from models containing narrow slits, by reference to the case of a wide plate with a central crack.
Abstract: Various methods for the determination of stress intensity factors from photoelastic data obtained from models containing narrow slits, are compared by reference to the case of a wide plate with a central crack. The linear slope method is applied to a number of two-dimensional problems when cracks interact with free surfaces or with other cracks.
23 citations
TL;DR: In this article, the known elastic limits and shakedown limits for the problem of Hertzian contact with and without friction are reviewed for the case of a general elliptical contact with a frictional force applied parallel with one of the axes.
Abstract: The known elastic limits and shakedown limits are reviewed for the problem of Hertzian contact with and without friction. Additional values are then derived where the literature is deficient, i.e., for the case of a general elliptical contact with a frictional force applied parallel with one of the axes. A new limit is then derived for the case when the residual stress is ‘cylindrical’ in nature.
21 citations
TL;DR: In this paper, matchstick and coin shaped specimens are used to determine the material strength consistency and mean fracture strength under five different stress rations, using Weibull statistics, and many practical loading modes of these simple shapes are assessed.
Abstract: Matchstick and coin shaped specimens are used to determine the material strength consistency and mean fracture strength under five different stress rations, using Weibull statistics.Many practical loading modes of these simple shapes are assessed. For the best, the necessary experimental work and results of the analyses are presented and illustrated for as-fired reaction-bonded silicon nitride (RBSN) tested at room-temperature.
15 citations
TL;DR: In this article, the two warped wavefronts generated in the moire interferometric system were separately sheared to produce two interference patterns, and the normal and shear contours were calculated by successively interrogating gratings in three directions and applying the strain rosette equation.
Abstract: Whole-field patterns of normal strains are produced by optical shearing. The two warped wavefronts generated in the moire interferometric system are separately sheared to produce two interference patterns. Superposition of these yields the normal strain contours. The shearing apparatus in an adjustable air wedge located near the common focal point of a telecentric lens system. By successively interrogating gratings in three directions and applying the strain rosette equation, the normal and shear strains over the entire surface can be calculated. Excellent experimental verification was obtained.
15 citations
TL;DR: In this article, the compliance method is used to determine strain energy release rates in mode I and II fracture of adhesive bonded joints, and a strong dependence of the strain energy-release rates upon the adhesive thickness is found.
Abstract: The compliance method is used to determine strain energy release rates in mode I and II fracture of adhesive bonded joints. A strong dependence of the strain energy release rates upon the adhesive thickness is found.Standard compact tension and compact shear specimens are used. It is found that the former are well suited to the investigation of mode I fracture, but that the latter are less well suited to mode II investigations.Attention is focussed on bond failures caused by cracks propagating between an adhesive and an adherend. Experimental and theoretical arguments are combined to determine the critical strain energy release rates at which such failures occur. The critical values are shown to be strongly dependent upon the method of surface preparation as well as upon the physical properties of the materials used.
14 citations
TL;DR: In this paper, the stress concentration factors due to axial loading applied to axisymmetric, internal projections on hollow tubes have been obtained by using the finite element method and a simple relationship between stress concentration factor and load position was also found.
Abstract: Stress concentration factors due to the axial loading applied to axisymmetric, internal projections on hollow tubes have been obtained by using the finite element method. A range of tube and projection dimensions and fillet radii have been covered by the investigation. It was found that all of the results could be presented on just two graphs. Hence the stress concentration factor, for any shape within the range investigated, can be quickly determined. A simple relationship between stress concentration factor and ‘load position’ was also found to exist.
10 citations
TL;DR: In this paper, a single fiber model is shown to overestimate the stresses at the fibre-matrix interface by about 20 per cent compared with a finite element solution for an infinite array of fibres.
Abstract: Two methods have been used to evaluate the transverse stresses when an aligned fibre composite is stressed in the fibre direction. A single fibre model is shown to overestimate the stresses at the fibre-matrix interface by about 20 per cent compared with a finite element solution for an infinite array of fibres. Using relatively few fibres in the finite element analysis, however, only gives very approximate stress distributions. With fibre volume fractions in the range 0-0.50 the average radial stresses across the fibre-matrix interface are always compressive, and can be represented by a relatively simple formula with an accuracy which is normally with in a few percent of the finite element value.
TL;DR: In this article, the internal forces and deflections of a segmented locking ring inserted in an annular slot in a cylindrical vessel, and supporting its bottom while the vessel is subjected to high internal pressure, are studied.
Abstract: The internal forces and deflections of a segmented locking ring inserted in an annular slot in a cylindrical vessel, and supporting its bottom while the vessel is subjected to high internal pressure, are studiedThe behaviour of the ring sectors is described in terms of a curved beam of rectangular cross section resting on elastic foundationsA closed form solution is obtained The results presented show that the reaction force between the ring sectors and the cylindrical vessel exhibits peaks at the sector ends, and that the maximum value of the bending moment for the ring sectors is moticeably higher than that for a complete ring
TL;DR: In this article, a radial crack at the edge of a circular hole subjected to a localized radial or tangential force on its perimeter is evaluated for determining the stress intensity factor when an arbitrary load distribution acts on the hole perimeter.
Abstract: Stress intensity factors are evaluated for a radial crack at the edge of a circular hole subjected to a localized radial or tangential force on its perimeter. These factors can be used as Green's functions to determine the stress intensity factor when an arbitrary load distribution acts on the hole perimeter. Both the accuracy and ease-of-use of this Green's function technique are demonstrated by comparing some test cases with known results. The strong dependence of the stress intensity factor for short cracks upon the detailed load distribution on the perimeter of the hole is discussed, and the importance of fricitional forces is demonstrated in the determination of fatigue lifetimes in the presence of fretting
TL;DR: In this paper, the maximum stresses in screw and block always occur near the start of contact, not on the block cross-section, and the RMS values of these variations are doubled by making the block unsymmetric and quadrupled by introducing bending.
Abstract: Unsymmetric shapes and loadings were studied using four frozen-stress photoelastic models. Pure tension was applied to all bolt heads. All the bolt shanks were necked. Three of the blocks were rectangular in cross-section, one was circular with a flat. Two tests represented clamping only; two tests modelled clamping and an offset separating force on a bolted joint causing bending. Results from two previously published tests with axisymmetric blocks are included as a basis for comparisons.The maximum stresses in screw and block always occur near the start of contact. Their values depend on thread configuration at the start of contact, not on the block cross-section.Using pitch-average curves as datum allowed analysis of the maximum variations from these curves. In the tests carried out, RMS values of these variations are doubled by making the block unsymmetric and quadrupled by introducing bending.
TL;DR: In this article, the C∗ parameter was used to predict the growth rate of a crack in a pre-fatigued, compact tension specimen made from a model material, which exhibits similar macroscopic behaviour to some high temperature materials.
Abstract: Five, pre-fatigued, compact tension specimens made from a model material, which exhibits similar macroscopic behaviour to some high temperature materials, have been subjected to steady loads. The results of these tests indicate that the ‘crack tip opening displacement’ governs the intiation of crack propagation. The subsequent creep crack growth rates are accurately predicted by the C∗ parameter.‘Moving crack’ finite element calculations have shown that accurate predictions of creep crack growth rates are possible even with relatively coarse meshes. However, the predictions are very sensitive to both the critical crack tip opening displacement used for initiation and to the magnitude of the load. Also, although the C∗ parameter is strictly only applicable to stationary state stresses at stationary cracks, predictions of crack growth were found to be accurate when using C∗ under non-stationary stress and moving crack situations.
TL;DR: In this paper, the effect of biaxial stress on the stress intensity factor and rivet loads has been determined for a single crack in a reinforced sheet, and it is shown that for a sheet reinforced by intact orthogonal stiffeners the stressintensity factor is unaffected by the stress applied parallel to the crack.
Abstract: The effect of biaxial stress on the stress intensity factor and rivet loads has been determined for a single crack in a reinforced sheet. It is shown that for a sheet reinforced by intact orthogonal stiffeners the stress intensity factor is unaffected by the stress applied parallel to the crack. In this respect its behaviour follows that of a crack in a unstiffened sheet but is contrary to conclusions drawn from previous results in the literature on biaxially stressed stiffened sheets. However, a re-analysis of these existing results shows them to be consistent with the present finding that the stress intensity factor is independent of the stress applied parallel to the crack in a sheet stiffened by orthogonal intact stiffeners. For a sheet in which a stiffener is broken across the crack line a tensile stress parallel to the crack is shown to reduce the stress intensity factor compared to that which exists for a uniaxial tensile stress only, applied perpendicular to the crackline. The opposite eff...
TL;DR: In this paper, a matrix method using integral equation of beams and the Newton Raphson procedure has been adopted for the analysis of clamped annular sector plates with lateral loads.
Abstract: Thin annular sector plates undergoing large deflections due to lateral loads are considered in this paper. For such plates exact solutions are not available. A matrix method using integral equation of beams and the Newton Raphson procedure has been adopted for the analysis of clamped annular sector plates. Numerical values for the deflection, the membrane and the bending stresses at the interior of the plate, and the bending stresses at the edges of the plate are obtained. A parametric study has been carried out by varying the sector angle from 30 to 90 degrees in steps of 30 degrees, and the ratio of the inner and outer radii from 0 to 0.6 in steps of 0.2. The results are presented in non-dimensional graphical format.
TL;DR: The results of an experimental stress analysis of the intersection region of two straight cylindrical shells are presented in this paper, where two models were used; in the first model the two axes were inclined at 30 degrees while for the second case, this angle was 60 degrees.
Abstract: The results of an experimental stress analysis of the intersection region of two straight cylindrical shells are presented Two models were used; in the first model the two axes were inclined at 30 degrees while for the second case, this angle was 60 degrees In each case, the main shell was 6625 in in diameter and 0198 in thick, while the attached shell was 35 in in diameter and 0226 in thick The intersection region was subjected to in-plane and out-plane moments applied to the attached shell and the measurements were made using foil resistance rosette gauges These measurements demonstrate that the local stress concentration in the intersection region of the main shell increases with the increase of the acute angle between the axes of the two shells; thus for a given moment loading on the attached shell, the stress concentration will be the largest when the two axes are normal to each other
TL;DR: In this article, the stress field around the tip of a crack propagating with constant velocity depends on the dynamic stress intensity factors KId and KIId if both of them are operative.
Abstract: The stress field around the tip of a crack propagating with constant velocity depends on the dynamic stress intensity factors KId and KIId if both of them are operative. These factors may be defined by their corresponding static values KIS and KIIS multiplied by convenient correction factors depending mainly on the crack propagation velocity c and on the longitudinal (c1) and shear (c2) was velocities of the material of the specimen. In this way a quantitative relation between dynamic and static components of the stress intensity factors is established. The dependence of this relation on the various components of velocities is investigated in this paper. It is also shown that the experimental method of reflected caustics gives an evaluation of this relation for various crack velocities and angles of inclination of the propagating crack.
TL;DR: In this article, the compounding method of evaluating stress intensity factors is used to calculate the stress intensity factor as a function of crack length, hole spacing, and row separation, and fatigue growth-rates are calculated for the particular case of a periodic array of holes with two cracks of equal length at each hole.
Abstract: The presence of cracks at more than one fastener hole in a row of fastener holes limits the safe use of a component more than if cracks exist at the edge of one hole only, since the stress intensity factor is greater, the crack growth-rate is faster, and the fatigue lifetime is less. The limitations can be made less severe if the component is made with alternate fastener holes in the row displaced to form another parallel row. The compounding method of evaluating stress intensity factors is used to calculate the stress intensity factor as a function of crack length, hole spacing, and row separation. Fatigue growth-rates are calculated for the particular case of a periodic array of holes with two cracks of equal length at each hole.
TL;DR: In this article, numerical contour integrations of the creep crack C∗ integral were carried out for two types of specimen and the results agree reasonably well with C ∗ evaluations using limit analysis methods.
Abstract: Numerical contour integrations of the creep crack C∗ integral were carried out for two types of specimen. The results agree reasonably well with C∗ evaluations using limit analysis methods; path-independence of C∗ is shown. A realistic definition of the creep pseudo-stationary state is proposed and various forms of creep data input are discussed.
TL;DR: In this article, the deformation of a circular membrane during a bulge test is considered as resulting from the superposition of a main, large displacement field, having a simple analytical form, and of an additional, small displacement field.
Abstract: The deformation of a circular membrane during a bulge test is considered as resulting from the superposition of a main, large displacement field, having a simple analytical form, on one hand, and of an additional, small displacement field, on the other The numerical problem pertaining to the determination of the additional displacements is posed and solved Reasonably accurate results are obtained with a restricted amount of computation
TL;DR: In this paper, the behavior of swivel ring flanges was investigated using both finite element and photoelastic and finite element methods of analysis, and it was found that taper and reduced thickness can result in significantly reduced stresses for the same bolt loads.
Abstract: Photoelastic and finite element methods of analysis were used to study the behaviour of swivel ring flanges. The use of tapers on the ‘back faces’ of flanges or of small, local reductions in flange thickness, to control the ‘load position’ and hence reduce the stresses, were investigated. The effectiveness of these techniques was assessed by comparing results with those for the more usual lapped joints between the flanges and rings. It was found that the taper and ‘reduced thickness’ techniques can result in significantly reduced stresses for the same bolt loads. However, the largest stress, which occurs in the fillet regions of the flanges, is not reduced by as much as the design codes predict. The friction conditions between the flange and ring were also found to have a significant effect on the stresses
TL;DR: In this article, the authors investigated the notch sensitivity of carbon composite angle-ply laminates and found that they are notch insensitive for almost all ply angles, except in those cases when the fibres are inclined at more than 70 degrees to the loading axis.
Abstract: The notch sensitivity of carbon composite angle-ply is investigated experimentally. It is found unexpectedly that these laminates are notch insensitive for almost all ply angles, except in those cases when the fibres are inclined at more than 70 degrees to the loading axis.
TL;DR: In this article, a biaxial test system and a method to achieve well defined damage to material in a purely mechanical way have been developed to study creep crack growth at elevated temperatures.
Abstract: In order to study creep crack growth at elevated temperatures, a biaxial test system and a method to achieve well-defined damage to material in a purely mechanical way have been developed Results from two preliminary tests are reported
TL;DR: In this paper, a method of measuring the flexural stiffness properties of anisotropic thin plates is presented, where three rhombic plates cut at different orientations from the test sheet are loaded in bi-axial bending, and the resulting deflections are recorded as fringe patterns using optical holography.
Abstract: A method of measuring the flexural stiffness properties of anisotropic thin plates is presented Three rhombic plates cut at different orientations from the test sheet are loaded in bi-axial bending, and the resulting deflections are recorded as fringe patterns using optical holography Curvatures determined in the chosen coordinate system and related to the bending moments are used to calculate the flexural stiffness terms The results of tests on cross-ply carbon fibre reinforced plastic material are in good agreement with laminated plate theory
TL;DR: In this paper, it was shown that the fixed-end displacement of a prismatic shaft of square cross-section in torsion is not equal to zero, but rather is a function of the interferometry.
Abstract: Holographic interferometry is used to obtain the interior displacement (warping) at different planes of a prismatic shaft of square cross-section in torsion. It can be shown that the fixed-end displacement is not equal to zero.
TL;DR: The premature fracture of a jack body during pressure testing drew attention to the need to examine the integrity of the body in the presence of defects, from the point of view of fracture and fatigue, and to re-examine the adequacy of existing inspection measures as discussed by the authors.
Abstract: The premature fracture of a jack body during pressure testing drew attention to the need to examine the integrity of the body in the presence of defects, from the point of view of fracture and fatigue, and to re-examine the adequacy of existing inspection measures. This assessment was based on fracture mechanics, and the methods used and conclusions drawn are described in the present paper.
TL;DR: In this paper, a method for the solution of in-plane stresses and displacements in quadrilateral plates under thermal loads is proposed, which employs eigenfunctions for angular regions together with a least squares technique.
Abstract: A method is proposed for the solution of in-plane stresses and displacements in quadrilateral plates under thermal loads. The procedure employs eigenfunctions for angular regions together with a least squares technique. An electronic computer is a necessary adjunct to the proposed method of solution. Numerical results are given.