Showing papers in "Journal of Strain Analysis for Engineering Design in 1974"
TL;DR: In this paper, a standard metal-to-metal adhesive-bonded lap joint is analyzed by a two-dimensional finite-element method and comparisons are made with previous analyses.
Abstract: Stresses in a standard metal-to-metal adhesive-bonded lap joint are analysed by a two-dimensional finite-element method and comparisons are made with previous analyses. Particular attention is paid to the stresses at the ends of the adhesive layer. Unlike previous work, which assumes the adhesive to have a square edge, the adhesive spew is treated as a triangular fillet. The highest stresses exist at the adherend corner within the spew. Linear elastic behaviour is assumed throughout.A rubber model is reported which confirms these results physically.Good agreement was also obtained between some practical results and the finite-element predictions.
507 citations
TL;DR: In this paper, Sneddon showed that if the punch has a continuous profile, it is not generally possible to determine the extent of the contact area from purely geometrical considerations, though it may be poss- ible to determine its shape from considerations of sym- metry as with the axi-symmetric punch.
Abstract: unit distance into the elastic solid. If the punch has a continuous profile, it is not generally possible to determine the extent of the contact area from purely geometrical considerations, though it may be poss- ible to determine its shape from considerations of sym- metry as with the axi-symmetric punch. For this latter case, Sneddon
52 citations
TL;DR: In this paper, the use of television equipment was used to detect and process the information contained in the speckle pattern and display the consequent interferogram, which is faster and more convenient and versatile than traditional photographic methods.
Abstract: The characteristic speckle pattern formed when imaging a scattering surface illuminated by laser light retains phase information, which can be used for interferometric measurement of surface displacement. The application of this principle to measuring in-plane strain resolved in one direction is described, together with the novel use of television equipment to detect and process the information contained in the speckle pattern and display the consequent interferogram. This is faster, and more convenient and versatile than customary photographic methods. Sources of practical error are analyzed, and some results are presented from investigations of strain distributions in fibre-composite tensile specimens.
35 citations
TL;DR: In this paper, the Young's fringe pattern was used to detect the in-plane displacements of tensile specimens and cracked specimens, and changes in length of aluminium crystals due to annealing.
Abstract: A photograph of a laser speckle pattern will diffract light, and a doubly exposed negative, which has been shifted between exposures, will produce a Young's fringe pattern with the fringe spacing inversely proportional to the displacement. This effect is used to detect the in-plane displacements of tensile specimens and cracked specimens, and changes in length of aluminium crystals due to annealing.
24 citations
TL;DR: In this paper, a laser interferometer system is used to record two mutually perpendicular diffraction gratings on a photoresist coated specimen, and when either grating is re-illuminated by the fringe pattern used to form it, real-time observations can be made of moire fringes corresponding to surface displacements which occur as a tensile load is applied to the specimen.
Abstract: A laser interferometer system is used to record two mutually perpendicular diffraction gratings on a photoresist coated specimen. When either grating is re-illuminated by the fringe pattern used to form it, real-time observations can be made of moire fringes corresponding to surface displacements which occur as a tensile load is applied to the specimen. The technique has been used to study the in-plane deformations of carbon-fibre composites, and typical results are given.
23 citations
TL;DR: Anisotropic slip-line fields have been developed in the flanges of drawn cups and used to predict the location of the ears and hollows at the onset of the drawing operation as discussed by the authors.
Abstract: Anisotropic slip-line fields have been developed in the flanges of drawn cups and used to predict the location of the ears and hollows at the onset of the drawing operation. The analysis is based on Hill's plane-strain theory of anisotropic metals. The material anisotropy is characterized by a lumped anisotropic parameter c.Deep-drawing tests were performed on circular blanks cut from anisotropic sheet and the actual deformation mode of particles in the flange was compared with the theoretical predictions. The correlation was found to be favourable.
17 citations
TL;DR: In this paper, the authors used a combination of live and double-exposure techniques to investigate the bending moment along an axial surface generator of a pipe joint, and obtained the surface strain using speckle photography.
Abstract: Holographic interferometry was used to investigate the behaviour of a plastic pipe joint when subjected to internal pressure. By a combination of ‘live’ and double-exposure techniques the variation of bending moment along an axial surface generator of the joint can be evaluated. To obtain the surface strain, an interferometric technique using speckle photography was used. An important practical factor is the method of mounting the object. For the measurement of much larger surface movements, such as occur when a cantilever is loaded, simple speckle photography, with subsequent point-by-point analysis of the recorded image, is used.
16 citations
TL;DR: In this paper, the fatigue lives of variously notched plates have been determined theoretically and experimentally by invoking a crack propagation law, and a safe prediction of fatigue life has been made for a complex profile subjected to non-simple loading conditions.
Abstract: The fatigue lives of variously notched plates have been determined theoretically and experimentally. Theoretical predictions of fatigue lives involved the determination of stress-intensity factors from finite-element analyses. By invoking a crack propagation law, fatigue-life predictions were made for four specimens.Fatigue experiments were conducted on four notched plates subjected to end load plus bending. Comparison with theoretical results shows that the experimental lives were greater by factors of 1.30 to 1.54. These results are most satisfactory since (1) a safe prediction of fatigue life has been made for a complex profile subjected to non-simple loading conditions, and (2) a theoretical elastic analysis has sufficed for a situation involving plastic strains.
15 citations
TL;DR: In this paper, a new experimental technique based on the method of caustics is presented for the measurement of the distance between the lips of a crack near the crack-tip, where two parts of the caustic formed by reflections from the front and rear faces of the specimen lie at a distance from each other.
Abstract: A new experimental technique based on the method of caustics is presented for the measurement of the distance between the lips of a crack near the crack-tip. The two parts of the caustic formed by reflections from the front and rear faces of the specimen lie at a distance from each other. The gap between these parts depends on the total c.o.d. (crack-opening displacement), that is the initial opening and the opening due to loading, as well as on the optical and mechanical characteristics of the material By increasing the external loading of the cracked plate, the gap between the parts of the caustic was changed and this gap measured the instantaneous c.o.d. due to loading. The method was applied to the measurement of small c.o.d.s. due to small-scale loading, with satisfactory results. Therefore it can certainly be used to measure c.o.d.s at large loading steps, up to fracture, because the gap between the parts of the caustic becomes significant and easy to measure. Measurements with cracked plate...
13 citations
TL;DR: In this paper, fracture-toughness tests were conducted on Araldite CT 200, in order to obtain K1c, the plane-strain, mode 1 critical stress-intensity factor.
Abstract: Fracture-toughness tests were conducted on Araldite CT 200, in order to obtain K1c, the plane-strain, mode 1 critical stress-intensity factor. Two essentially different methods were used, namely the photoelastic method and the quasistatic energy method.In the photoelastic method, stress fringe patterns were analysed at load intervals up to failure and the stress-intensity coefficients obtained were compared with those from the boundary collocation method. In the energy method, two types of specimen geometry were tested, resulting in stable crack propagation. Good correlation was obtained between the two methods.
12 citations
TL;DR: In this article, the behavior of a rapidly moving crack around a small hole in p.m.a. (polymethylmethacrylate) has been investigated, by the use of ultra-high-speed photographic techniques, to measure the changes in dynamic stressintensity factor and crack velocity.
Abstract: The behaviour of a rapidly moving crack around a small hole in p.m.m.a. (polymethylmethacrylate) has been investigated, by the use of ultra-high-speed photographic techniques, to measure the changes in dynamic stressintensity factor and crack velocity. Cracks were initiated by explosively driven wedge impact, and penetrated holes of diameters of 1/16 in (1.56 mm) and 1/8 in (3.12 mm). The cracks propagating after the hole show a higher velocity than those prior to the hole, though the dynamic stress-intensity factor decreases. There is no general relation between the dynamic stress-intensity factor and the surface roughness for the higher-velocity crack.
TL;DR: A computer program has been developed to solve for torsion of solids of revolution by numerical solution of an exact boundary integral equation which is valid for any shape and any degree of connectivity as mentioned in this paper.
Abstract: A computer programme has been developed to solve for torsion of solids of revolution by numerical solution of an exact boundary integral equation which is valid for any shape and any degree of connectivity. The programme gives solutions directly at the boundary and requires only simple boundary data defining the contour to be input. The basic integral equation has been differentiated to give internal stresses directly, when required.The computed results have been checked experimentally by photoelastic techniques and are compared with analytical solutions for the circular cylinder and the cone.Comprehensive charts are given for stress concentrations in stepped shafts with circular fillets and fillets constructed of two blending radii. Fillets giving stress concentrations close to unity have also been investigated.
TL;DR: In this paper, the displacement equations for principal displacements in a uniformly pressurized thin-walled cylinder having an elliptic median line were developed from a knowledge of the expressions for tension and bending moment at a general position in the cylinder wall.
Abstract: Equations for principal displacements in a uniformly pressurized thin-walled cylinder having an elliptic median line are developed from a knowledge of the expressions for tension and bending moment (1) at a general position in the cylinder wall. Displacements derived from these equations are compared with the simple expressions presented by Bresse (2) and MacAlpine (3).The results of a detailed experimental study in which displacements were measured by a laser interferometer are used to assess the validity of the new displacement equations and to compare these with the predictions due to Bresse and MacAlpine.It is shown that the equations developed here give good agreement with experimentally measured displacements and furthermore the predictions made in (2) and (3) grossly overestimate the displacement values and are also very much in error when stating that the minor-diameter expansion is of the same order as the major-diameter contraction. In the investigation reported here (ellipse with mean a...
TL;DR: In this paper, a plane-stress slip-line field analysis has been made of the possible plastic deformation modes of a built-in cantilever beam of rectangular cross-section subjected to a shear force at the free end with or without an axial load.
Abstract: A plane-stress slip-line field analysis has been made of the possible plastic deformation modes of a built-in cantilever beam of rectangular cross-section subjected to a shear force at the free end with or without an axial load Plastic-collapse loads for the several types of deformation patterns suggested are computed and the results presented in detail in the form of curves Some simple upper- and lower-bound estimates to the collapse load have also been determined and are compared with both the plane-stress slip-line results and those presented by Green (1), plane-strain conditions being assumed The agreement between the plane-stress slip-line fields and the assumed lower-bound results is found to be excellent
TL;DR: In this article, a testing machine for the study of the deformational behaviour of plastics under bending loads complements high-accuracy tensile-creep testing machines and provides a more appropriate means for the testing of brittle fiber-plastics composites and plastics sandwich structures.
Abstract: A testing machine developed for the study of the deformational behaviour of plastics under bending loads complements high-accuracy tensile-creep testing machines and provides a more appropriate means for the testing of brittle fibre-plastics composites and plastics sandwich structures. The machine is suitable for applying constant loads and automatically recording the deflections of specimens at several points over periods of up to three months.
TL;DR: In this article, the authors used a ruby pulsed laser as the coherent light source, applied to the study of a longitudinal transient stress induced in a rectangular bar by an axial impact of a second bar.
Abstract: The paper reports on the technique of holographic interferometry, using a ruby pulsed laser as the coherent light source, applied to the study of a longitudinal transient stress induced in a rectangular bar by an axial impact of a second bar. Reasons for using a holographic technique are given together with ways of alleviating some of the associated problems. Some qualitative results are presented on the work done to date.
TL;DR: In this paper, the problem of interpreting holographic and speckle-pattern interference fringes is discussed and a general theory is described and it is shown how plane strain may be measured by use of holographic interferometry.
Abstract: In this paper the problem of interpreting holographic and speckle-pattern interference fringes is discussed. A general theory is described and it is shown how plane strain may be measured by use of holographic interferometry. Certain limitations inherent in holographic interferometry are elucidated and it is demonstrated how these are eliminated if speckle-pattern interferometry is used. In the final section of the paper a technique is described in which holographic or speckle-pattern interferometry is used to determine accurate values of Poisson's ratio and Young's modulus.
TL;DR: In this paper, the influence of optical retarders on the isochromatic and isopachic fringes obtained by holographic photoelasticity is studied, and it is shown that the fringes are distorted for both light and dark field configurations.
Abstract: In this paper the influence of inaccuracies of the optical retarders on the isochromatic and isopachic fringes obtained by holographic photoelasticity is studied.For the single-exposure hologram it is shown that the isochromatic visibility decreases as for light- and dark-field configurations, whereas the isochromatic fringes are distorted only for the dark-field configuration.For the double-exposure hologram it is shown that the isopachic fringes are generally distorted; with the isochromatics there is a decrease of fringe visibility.Experimental results confirming the theory are reported.
TL;DR: In this paper, it was shown that the filling of polypropylene with glass spheres instead of fibres results in smaller but still significant increases in shear stiffness, which are comparable to the relative increases in tensile stiffness.
Abstract: Inclusion of glass fibres in plastics has been thought to produce little improvement in their stiffness in shear compared with that in tension but results obtained with polypropylene filled with fibres show that they increase in shear stiffness to a significant extent and in some directions more than its tensile stiffness.The filling of polypropylene with glass spheres instead of fibres results in smaller but still significant increases In shear stiffness, which are comparable to the relative increases in tensile stiffness.In both cases the experimentally determined values of shear stiffness fall within the bounds derived from energy considerations and correlate closely with the results obtained from a simple model of a composite material
TL;DR: In this article, the development of a simple, inexpensive power supply for strain-gauge applications, with a long-term voltage stability of better than 1 part in 1000, is described.
Abstract: The development of a simple, inexpensive power supply for strain-gauge applications, with a long-term voltage stability of better than 1 part in 1000, is described.
TL;DR: In this paper, a theoretical analysis was carried out to determine the distribution of stresses and radial deflections due to internal pressure in the limpet of a limpet-coil pressure vessel.
Abstract: A theoretical analysis was carried out to determine the distribution of stresses and radial deflections due to internal pressure in the limpet of a limpet-coil pressure vessel. A computer programme was developed to carry out the complete calculations. Theoretical results for a vessel having the dimensions of a test vessel were compared with the corresponding experimental values obtained from strain-gauge and deflection-gauge measurements on the test vessel itself.
TL;DR: In this paper, an alternative series solution using powers rather than exponentials of time was found, which provides not only rapid convergence but simple closed forms for bounds on the maximum deflection.
Abstract: A solution to the problem of buckling of a viscous strut with eccentrically applied end loads has been found previously as an infinite trigonometric series having poor convergence for small values of time. An alternative series solution has been found, using powers rather than exponentials of time, which provides not only rapid convergence but simple closed forms for bounds on the maximum deflection.
TL;DR: In this article, a lower bound analysis for the upper bound of the limit pressure for the oblique intersection of a flush cylindrical nozzle and the torus of a cylinear vessel with a torispherical end is presented.
Abstract: A lower-bound limit analysis is presented for the calculation of the limit pressure for the oblique intersection of a flush cylindrical nozzle and the torus of a cylindrical vessel with a torispherical end. A rotationally asymmetric formulation of stress resultants is specified in assumed plastic regions in terms of an independent set of variables and the limit pressure is computed for a limited number of geometric parameters by a non-linear programming method.
TL;DR: In this article, the large deflections of rectangular plates and beams obeying a non-linear stress-strain law are examined and solutions are obtained by use of dynamic relaxation, a numerical finite-difference technique.
Abstract: The large deflections of rectangular plates and beams obeying a non-linear stress-strain law are examined. Solutions are obtained by use of dynamic relaxation, a numerical finite-difference technique. Comparisons are made with alternative solutions and experimental results. The effects of varying parameters in the non-linear expressions are considered.
TL;DR: In this paper, the stress and strain distribution in a large plate containing a reinforced circular hole when loaded monotonically in uniaxial tension beyond the elastic range is investigated, where the hole is reinforced with a cylindrical member which is symmetrical with respect to the plate to which it is continuously joined.
Abstract: This investigation deals with the stress and strain distribution in a large plate containing a reinforced circular hole when loaded monotonically in uniaxial tension beyond the elastic range. The hole is reinforced with a cylindrical member which is symmetrical with respect to the plate to which it is continuously joined. Consideration is given to various degrees of plastic deformation of plate and reinforcement corresponding to various uniaxial tension loads. Whole-field analyses of the reinforcement in cylindrical co-ordinates and of the plate in plane polar co-ordinates are obtained by the finite-difference method in which the governing equilibrium equations are expressed in terms of displacements and plastic strains. Deformation theory of plasticity is employed. Limitations of the ‘compact’ reinforcement assumption result from the subsequent whole-field investigation.Results are obtained for material of a specific stress-strain curve so that strain-gauge results could be compared with the stra...
TL;DR: In this article, photoelastic tests have been carried out to determine stress-concentration factors for spherical and elongated dimples which may be machined into the bearing surfaces of crankshafts to remove cracks or inclusions.
Abstract: Photoelastic tests have been carried out to determine stress-concentration factors for spherical and elongated dimples which may be machined into the bearing surfaces of crankshafts to remove cracks or inclusions. The shapes and sizes are based on the proposed British Standard.The effects of proximity of dimples to one another and to a radiused shoulder are also studied. The results show that the stress concentrations at dimples are much smaller than those at circumferential grooves on which the proposed British Standard is based.
Abstract: It is often suggested that splitting a specimen and machining grid lines on one of the exposed planes to study flow patterns during plastic deformation interferes with the flow process under investigation. A procedure is described here for flow-function analysis of extrusion specimens in which artificial grid lines are not required. The procedure is restricted to situations in which the microstructure exhibits line segments produced by deforming grains or second-phase particles as they flow through the die. These segments represent partial-flow lines according to the assumptions of flow-function analysis. From numerical analysis of their slopes it is possible to construct the complete flow function. From this, all the kinematic quantities of the deformation can be determined.
TL;DR: In this article, the authors used Diametral extensometers for tension-compression testing and found that indentation of the surface of the specimen by the contacts, which is an ef...
Abstract: Diametral extensometers are often used in tension-compression testing. When very small strains are being recorded, indentation of the surface of the specimen by the contacts, which is an ef...
TL;DR: In this article, a brief report is given on the detection of fine cracks in concrete cubes and cylinders by holographic interferometry, and a detailed description of the method is given.
Abstract: A brief report is given on the detection of fine cracks in concrete cubes and cylinders by holographic interferometry.
TL;DR: In this paper, a rectangular finite-element model was developed for thermal stress analysis of shallow shells and the elemental equations were obtained from a two-field variational principle which employed equilibriating stress fields within the elements and compatible displacement fields along inter-element boundaries.
Abstract: A rectangular finite-element model has been developed for thermal-stress analysis of shallow shells. The elemental equations are obtained from a two-field variational principle which employs equilibriating stress fields within the elements and compatible displacement fields along inter-element boundaries. The extremization of the variational functional tends to satisfy the compatibility requirements within the elements and equilibrium conditions along inter-element boundaries. The element is employed for thermal-stress analysis of several examples and the numerical results obtained are compared with some analytical results.