scispace - formally typeset
Search or ask a question

Showing papers in "Journal of Strain Analysis for Engineering Design in 1975"


Journal ArticleDOI
TL;DR: In this paper, the problem of minimizing stress concentrations in machinery components is formulated as one of unconstrained minimization by incorporating all "side" constraints on design variables by use of penalty functions.
Abstract: The problem of minimizing stress concentrations in machinery components is formulated as one of unconstrained minimization by incorporating all ‘side’ constraints on design variables by use of penalty functions. Design parameters describing the transition are determined for an optimal fillet in a tension bar, as well as for a piston-rod ‘eye’. The procedure is generally applicable.

154 citations


Journal ArticleDOI
TL;DR: In this article, an iterative solution was proposed to determine velocities in plastic flow using a finite element formulation, by updating co-ordinates very large deformation can be followed.
Abstract: An iterative solution permits determination of velocities in plastic flow using a finite element formulation. By updating co-ordinates very large deformation can be followed.

66 citations


Journal ArticleDOI
TL;DR: A biaxial fatigue testing rig which employs cruciform specimens loaded by four double-acting hydraulic cylinders has been improved by the addition of a closed-loop servo-control system as mentioned in this paper.
Abstract: A biaxial fatigue testing rig which employs cruciform specimens loaded by four double-acting hydraulic cylinders has been improved by the addition of a closed-loop servo-control system. This system enables the loads or strains in the two principal directions to be varied independently of each other. The paper describes the modifications that were made to the system and the various problems then encountered. Further development work was then necessary before the rig operated satisfactorily. The details are published to be of assistance to others who may wish to construct specialist servo-controlled hydraulic testing equipment.

65 citations


Journal ArticleDOI
TL;DR: The fracture mechanics concept of stress intensity factor has proved particularly convenient for the analysis of fatigue crack growth data in a form which can be applied directly to engineering problems, and its use has led to a much better understanding of the fatigue behaviour of structures as discussed by the authors.
Abstract: The phenomenon of metal fatigue has been studied for a long time, but it has only relatively recently been appreciated that most structures, particularly welded joints, contain crack-like flaws, so that virtually the whole fatigue life is occupied by fatigue crack growth. The fracture mechanics concept of stress intensity factor has proved particularly convenient for the analysis of fatigue crack growth data in a form which can be applied directly to engineering problems, and its use has led to a much better understanding of the fatigue behaviour of structures. The effects of interaction between different load levels are not yet fully understood; this is not necessarily a serious drawback as servo-hydraulic fatigue testing equipment permits the application of virtually any load history to structures or fatigue crack growth specimens.

38 citations


Journal ArticleDOI
TL;DR: Some of the more useful methods of evaluating stress intensity factors are presented in a concise form as mentioned in this paper, and references are given to papers where the methods are more fully described and used to solve specific crack problems.
Abstract: Some of the more useful methods of evaluating stress intensity factors are presented in a concise form. The stress intensity factor is defined and compared with the more familiar stress concentration factor. The shape factor, the parameter which characterizes the shape of the crack, the orientation of the crack and the proximity of other boundaries, is introduced; the techniques for determining the shape factor are divided into theoretical and experimental. Each method is described with a minimum of mathematical detail; references are given to papers where the methods are more fully described and used to solve specific crack problems. The accuracy and usefulness of the methods is summarized.

33 citations


Journal ArticleDOI
TL;DR: In this article, a closed form solution is obtained for stresses in a rotationally symmetric, nonhomogeneous, anisotropic, annular disk of varying thickness and density, subjected to thermal loading.
Abstract: Closed form solution is obtained for stresses in a rotationally symmetric, nonhomogeneous, anisotropic, annular disk of varying thickness and density, subjected to thermal loading. Analysis is presented for a particular type of anisotropy, namely Polar Orthotropy, in which axes of anisotropy coincide with the principal axes of stresses at each point in the disk. The variations of homogenity, density and thickness are assumed to be hyperbolic. Numerical results in the form of graphs presented show the effect of nonhomogenity, density and degree of orthotropy on the stress distribution in a disk subjected to constant and varying temperature gradients. Homogeneous, varying density anisotropic rotating disk of varying thickness forms a special case of the analysis.

26 citations


Journal ArticleDOI
TL;DR: In this paper, the use of triangular elements in finite-element analyses was considered and a strain energy function was proposed to enable solutions to be obtained at strains well beyond those of linear classical elasticity theory.
Abstract: For a highly incompressible material the use of triangular elements in plane-strain finite-element analyses restricts the number of degrees of freedom. A computer programme is developed which uses quadrilateral elements, and various methods of reducing computation time are employed. A strain-energy function is proposed which will enable solutions to be obtained at strains well beyond those of linear classical elasticity theory.

16 citations


Journal ArticleDOI
C. W Bert1
TL;DR: In this paper, the problem of bending-stretching coupling of thin, laminated, anisotropic elastic plates is formulated as one in the linear theory of thin and laminated elastic plates.
Abstract: The problem is formulated as one in the linear theory of thin, laminated, anisotropic elastic plates. A direct force-and-moment formulation is used, simplifying approximation is introduced and a closed-form solution is obtained. This solution exhibits bending-stretching coupling if the plate is asymmetrically laminated with respect to mass or stiffness or both. Numerical results typical of certain composite materials of current interest are presented. Specific laminates considered as examples include (1) glass—epoxy/steel, (2) cross-ply graphite—epoxy, and (3) various quasi-isotropic layups of organic fibre—epoxy.

14 citations


Journal ArticleDOI
TL;DR: In this article, a solution for the steady-state thermal stress and displacement field in an infinite elastic solid containing an insulated penny-shaped crack is given, which is reduced to a mixed-boundary-value problem for the half-space.
Abstract: A solution is given for the steady-state thermal stress and displacement field in an infinite elastic solid containing an insulated penny-shaped crack. The problem is reduced to a mixed-boundary-value problem for the half-space, making use of Green's isothermal solution for the thick elastic plate in complex harmonic potentials and a particular thermoelastic solution due to Williams. In the axisymmetric case, the complex potential reduces to the real harmonic function used by Shail in his solution for the external crack.To illustrate the use of the method in both axisymmetric and non-axisymmetric problems, complete solutionsare given for (1) a uniform heat flow and (2) a linearly varying heat flow disturbed by an insulated penny-shaped crack.

14 citations


Journal ArticleDOI
K Tanaka1
TL;DR: In this paper, the authors describe results of several recent studies, carried out in Japan, on metal fatigue problems using X-ray diffraction techniques, including the effect of residual stress on fatigue strength, non-destructive detection of fatigue damage from information supplied by X-Ray diffraction, and Xray microbeam analysis of stress and strain near the tips of fatigue cracks and fracture surfaces.
Abstract: This paper describes results of several recent studies, carried out in Japan, on metal-fatigue problems using X-ray diffraction techniques. The subjects covered are the effect of residual stress on fatigue strength, non-destructive detection of fatigue damage from information supplied by X-ray diffraction, and X-ray microbeam analysis of stress and strain near the tips of fatigue cracks and fracture surfaces. The usefulness of the X-ray approach to fatigue problems is emphasized and possible future developments are suggested.

13 citations


Journal ArticleDOI
TL;DR: In this paper, the crack opening displacement, Δ, and the J contour integral are proposed for describing the stresses and deformation at the tip of a sharp crack embedded in a region of yielding material.
Abstract: Yielding fracture mechanics seeks to find a relationship between applied stress, crack size and material toughness that is independent of the geometry of a component when fracture occurs after significant degree of yielding. The crack opening displacement, Δ, and the J contour integral are two proposals for describing the stresses and deformation at the tip of a sharp crack embedded in a region of yielding material. The concepts can be related in the form J = M σ YΔ where σY is the uniaxial yield stress, and M a factor with a value between about 1 and 2.5. The concepts are still under development. Either term can be chosen as a measure of the severity of crack tip deformation in a given material with the onset of crack growth in monotonic loading occurring at a critical value, Δc or Jc, for a given thickness. Experimental evidence so far is in broad support of this picture but there remains uncertainty over the degree to which Δc or Jc is independent of geometry and the extent to which stable crac...

Journal ArticleDOI
R N Parkins1
TL;DR: In this paper, the authors recognize the importance of such factors as environment composition, especially within the confines of a pit or crack, and of plasticity, especially in relation to the rate at which deformation presents bare metal at the tips of cracks, is vital if reproducible data are to be obtained.
Abstract: The interdependence of material structure, electrochemical parameters and the response of a material to the application of stress can produce slow crack growth by a number of different mechanisms. The recognition of the importance of such factors as environment composition, especially within the confines of a pit or crack, and of plasticity, especially in relation to the rate at which deformation presents bare metal at the tips of cracks, is vital if reproducible data are to be obtained.

Journal ArticleDOI
TL;DR: In this paper, the mechanical and optical properties of a transparent epoxy are described, the response of which can be ‘locked-in’ at a critical temperature, which is closer to the Poisson's ratio of common engineering materials than is that of the commonly used epoxies.
Abstract: The mechanical and optical properties of a transparent epoxy are described, the response of which can be ‘locked-in’ at a critical temperature. The Poisson's ratio of this material is about 0.4, which is closer to the Poisson's ratio of common engineering materials than is that of the commonly used epoxies. Since the material is compressible, strain measurements on relaxed slices permit the complete determination of the stress field. Examples of applications to a solid and hollow sphere and to a tube, subjected to diametral compression, are given. The method permits the solution of three-dimensional problems by use of (1) photoelastic data only, (2) the moire method only, or (3) mechanically obtained data only, or different combinations of them.

Journal ArticleDOI
TL;DR: In this paper, the problems in applying LEFM to the fracture of metals are discussed and the fracture toughness values for cleavage and fibrous modes are related to the micromechanics of fracture.
Abstract: Problems in applying LEFM to the fracture of metals are discussed. Fracture toughness values for cleavage and fibrous modes are related to the micromechanics of fracture.

Journal ArticleDOI
D J Hayes1
TL;DR: In this paper, the development of energy balance approach to fracture is traced, and the justification for its application to practical problems is indicated, and limitations of the approach are discussed and the rationale for its use in practical problems are discussed.
Abstract: The development of energy balance approach to fracture is traced. Limitations of the approach are discussed and the justification for its application to practical problems is indicated.

Journal ArticleDOI
TL;DR: In this article, a method for the determination of the absolute retardation families in photoelasticity was proposed, which used real-time holographic interferometry, and required only one hologram for the observation of absolute retardations over the whole model.
Abstract: A method for the determination of the absolute retardations families in photoelasticity.The method, which use real-time holographic interferometry, requires only one hologram for the observation of the absolute retardations over the whole model.This is achieved by viewing in the reconstruction process the loaded model through a polarizer. Where the polarization direction is parallel to one of the principal stresses, only the corresponding family of absolute retardations is observed.As an example of application the absolute retardations and stresses in a deep beam centrally loaded are determined.

Journal ArticleDOI
TL;DR: The situation with respect to non-standard tests is reviewed in this paper, where fracture toughness parameters under this heading include JIc, equivalent energy values, fracture propagation energy values and R-curve analysis.
Abstract: Recommended methods for measuring fracture toughness parameters are discussed. The relevant Draft British Standards are: (a)Draft for Development 3:1971 ‘Methods for Plane Strain Fracture Toughness (KIc) Testing’.(b)Draft for Development 19:1972 ‘Methods for Crack Opening Displacement (COD) Testing’.These documents are being revized and updated for publishing as full British Standards and any significant additions and alterations are noted.The situation with respect to non-standard tests is reviewed. The fracture toughness parameters under this heading include JIc, equivalent energy values, fracture propagation energy values and R-curve analysis. Particular attention is paid to the influence of strain rate on testing procedures and a crack monitoring technique is discussed.

Journal ArticleDOI
TL;DR: In this paper, a method based on the Moire-fringe technique was developed to measure the related rotation of the flanges of a thin-walled tubular specimen during a torsion test.
Abstract: A method has been developed to measure the related rotation of the flanges of a thin-walled tubular specimen during a torsion test. The method, which is based on the Moire-fringe technique, is capable of use at the high rates of strain encountered during a Hopkinson-bar test, as well as at low rates of strain. In the application described, the specimen gauge length is very short, but the method could be used for specimens of considerably longer gauge length.Direct calibration of the system is easily carried out at low angular velocities. The method can then be used to measure directly the specimen strain during a Hopkinson-bar test, and thus to check the value derived from measuremets of torsional waves in the elastic bars. Results of such comparisons are given, and it is found that the values given by the two method agree well, the differnce being attributable largely to inaccuracies in the torque measurement. The new method permits the determination of specimen deformation during the later stage...

Journal ArticleDOI
TL;DR: In this paper, the holographic determination of stress levels in a defect-free tube and in the sound section of a tube containing defects was performed using thin cylinder theory, and the tube surface area adversely affected by the defects was visualized.
Abstract: The holographic determination of stress-levels in a defect-free tube and in the sound section of a tube containing defects. A comparison with stress values using thick cylinder theory is given, and the tube surface area adversely affected by the defects is visualized, Size of defects detectable are also given.

Journal ArticleDOI
TL;DR: In this paper, the authors defined the classical procedure and improvements described, basic experimental results and calibration methods demonstrated, as well as the basic procedure and improvement described, and basic results and methods demonstrated.
Abstract: Equidensity techniques used increasingly in photoelasticity are based on pseudo-solarization effects. These and related photographic phenomena are defined, the classical procedure and improvements described, basic experimental results and calibration methods demonstrated.

Journal ArticleDOI
D J Hayes1
TL;DR: In this article, the basic philosophy of the stress intensity approach to fracture is scrutinized and the limitations of the approach are discussed and its application to the solution of practical problems is indicated.
Abstract: The basic philosophy of the stress intensity approach to fracture is scrutinized. The limitations of the approach are discussed and its application to the solution of practical problems is indicated.

Journal ArticleDOI
TL;DR: In this article, a modified form of the dynamic relaxation method is used to deal with problems involving beams or plates which deflect until contact is made with internal restraints, and three particular problems are examined.
Abstract: Problems involving beams or plates which deflect until contact is made with internal restraints are examined using a modified form of the dynamic relaxation method. Three particular problem...

Journal ArticleDOI
TL;DR: In this paper, an ultrasonic crack follower which continuously monitors the position of a fatigue crack in a 36 mm thick C.K.S. type specimen is described, where an open-bottomed tank containing a mobile immersion probe is mounted on the top surface of the sample; as the crack grows the probe is automatically advanced to keep the reflected signal intensity constant.
Abstract: The design of an ultrasonic crack follower which continuously monitors the position of a fatigue crack in a 36 mm thick C.K.S. type specimen is described. An open-bottomed ‘tank’ containing a mobile immersion probe is mounted on the top surface of the sample. The probe is used to measure the position of the crack tip by normal ultrasonic techniques; as the crack grows the probe is automatically advanced to keep the reflected signal intensity constant. The probe drive mechanism is geared to two potentiometers, one of which produces an output proportional to the probe position, the other is used to attenuate the load control signal so as to keep the stress intensity range constant. The unit was capable of detecting crack growth increments of 450 μm. The automatic nature of the measurement greatly simplified the collection of fatigue crack growth data.

Journal ArticleDOI
TL;DR: In this paper, an approach using a continuous representation in the region local to the fillet and a finite-element representation in regions where stress gradients are small is proposed for two-dimensional problems of elasticity.
Abstract: The stress analysis of cut-outs or notches involving fillets with constant curvature is considered for two-dimensional problems of elasticity. An approach using a continuous representation in the region local to the fillet and a finite-element representation in regions where stress gradients are small is proposed. The plan is shown to be effective in both accuracy of results and computer economy. A square cut-out with filleted corners is examined to illustrate the method. The versatility of the approach is then utilized to examine a class of U-notch (or slot) problems with only trivial changes in programming.

Journal ArticleDOI
TL;DR: In this paper, it is demonstrated that the Bauschinger effect can be eliminated by cycling down to zero stress and zero strain using progressively decreasing strain amplitudes, and that when the strain range is small, the structural strainhardening effect is not noticeably reduced.
Abstract: When copper is cycled between fixed limits of strain it ends towards a settled cyclic state. The two curves which form the tension-compression stress-strain loop will have the same shape but, no matter what point is chosen on the loop for the return to zero stress, the material will not be left with symmetrical tension-compression properties. This is because of the Bauschinger effect. It is demonstrated that the Bauschinger effect can be eliminated by cycling down to zero stress and zero strain using progressively decreasing strain amplitudes. Relatively few cycles suffice and, when the strain range is small, the structural strain-hardening effect is not noticeably reduced. Even with the largest range investigated (± 1 per cent plastic strain) the structural resoftening is slight. The significance of the subsequent tension and compression stress-strain curves is discussed.

Journal ArticleDOI
TL;DR: In this paper, the authors presented results on the plastic collapse behavior of an axisymmetric rotating shell, obtained by limit analysis and the Finite Element Method, in good agreement with experimental data.
Abstract: Results on the plastic collapse behaviour of an axisymmetric rotating shell, obtained by Limit Analysis and the Finite Element Method, are in good agreement with experimental data. The Finite Element Method, though computationally rather costly, permits, however, a more complete analysis of elasto-plastic behaviour. For the present case, the Limit Analysis has the advantage of greater computational simplicity and leads to a quite satisfactory forecast of collapse speed from the engineering point of view.

Journal ArticleDOI
TL;DR: In this article, the plotting of idealized torsional charatertics for spring steels in the form of stress-ratio diagrams is presented, showing that a single diagram closely represents the basic stress vs strain curve.
Abstract: The plotting of idealized torsional charatertics for spring steels in the form of stress-ratio diagrams shows that a single diagram closely represents the basic stress vs strain curve. It is also shown how corrections may be made to allow for the effect of the knee of the stress vs strain diagram.

Journal ArticleDOI
TL;DR: In full- or reduced-scale tests on skeletal structures, several cross-sections are usually strain-gauged to enable strain distributions to be obtained and stress resultants to be deduced.
Abstract: In full- or reduced-scale tests on skeletal structures, several cross-sections are usually strain-gauged to enable strain distributions to be obtained and stress resultants to be deduced This paper explains how such measurements are best analysed, with special emphasis on the proper inclusion of longitudinal stresses associated with warping Two examples are included

Journal ArticleDOI
TL;DR: In this paper, the condition of perfect clamping is discussed and it is shown that even for a reinforcing ring having a depth equal to one half the cylinders' diameter, it is still necessary to make some allowance for radial displacement at the oblique edge.
Abstract: The condition of ‘perfect clamping’ is discussed and it is shown that even for a reinforcing ring having a depth equal to one half the cylinders' diameter it is still necessary to make some allowance for radial displacement at the oblique edge. Reasons are suggested for the lack of symmetry in circumferential and axial stress profiles over the range ‘intrados’ to ‘extrados’.

Journal ArticleDOI
H E Enahoro1
TL;DR: A short graphical method is developed from the existing standard graphical technique for the solution of problems on shrunk-fit pressure-vessel design with great saving in time as compared with both the tedious anlytical solutions readily available in text books and the existing graphical method with its complex pattern of lines.
Abstract: A short graphical method is developed from the existing standard graphical technique for the solution of problems on shrunk-fit pressure-vessel design. Examples are provided to illustrate the versatility of the new method and the great saving in time as compared with both the tedious anlytical solutions that are readily available in text books and the existing graphical method with its complex pattern of lines.