Showing papers on "Stress concentration published in 1968"
TL;DR: In this paper, a total deformation theory of plasticity, in conjunction with two hardening stress-strain relations, is used to determine the dominant singularity at the tip of a crack in a tension field.
Abstract: D istributions of stress occurring at the tip of a crack in a tension field are presented for both plane stress and plane strain. A total deformation theory of plasticity, in conjunction with two hardening stress-strain relations, is used. For applied stress sufficiently low such that the plastic zone is very small relative to the crack length, the dominant singularity can be completely determined with the aid of a path-independent line integral recently given by rice (1967). The amplitude of the tensile stress singularity ahead of the crack is found to be larger in plane strain than in plane stress.
2,667 citations
TL;DR: In this article, the dominant singularity governing the plastic behavior at a crack tip is analyzed for conditions of plane stress and plane strain for cracks in both far tensile and far shear fields.
Abstract: Further details of the stress and strain fields associated with the dominant singularity governing the plastic behaviour at a crack tip are presented for conditions of plane stress and plane strain for cracks in both far tensile and far shear fields. Results are obtained for a power hardening material. Limiting cases for non-hardening materials are shown to correspond to certain perfect plasticity solutions.
700 citations
TL;DR: In this paper, the basic laws governing fatigue are derived theoretically for failure in both the high and low stress regions, and the material parameters controlling crack propagation determined, and a simple theory is developed to assess quantitatively the mechanism of fatigue crack propagation in metals.
Abstract: A simple theory is developed to assess quantitatively the mechanism of fatigue crack propagation in metals. The basic laws governing fatigue are derived theoretically for failure in both the high and low stress regions, and the material parameters controlling crack propagation determined. The theory is compared with that developed in recent years using linear fracture mechanics.
505 citations
TL;DR: Composite tensile-failure modes, failure load prediction, experimental data and statistical analysis of stress concentration effects are discussed in this article, where failure load and stress concentration effect are discussed.
Abstract: Composite tensile-failure modes, discussing failure load prediction, experimental data and statistical analysis of stress concentration effects
294 citations
TL;DR: In this paper, changes in electrical resistivity were observed as a function of compressive stress in a variety of crystalline rocks that were subjected to confining pressure of up to 5 kb and to pore pressure of water of 500 bars.
Abstract: Changes in electrical resistivity were observed as a function of compressive stress in a variety of crystalline rocks that were subjected to confining pressure of up to 5 kb and to pore pressure of water of 500 bars In the majority of the rocks, resistivity increased slightly up to about half the fracture stress; just the reverse effect has been noted elsewhere for rocks that were apparently partially saturated Beyond half and particularly within about 20 per cent of the fracture stress, resistivity dropped typically by an order of magnitude This sharp decrease corresponded closely to an increase in porosity, or dilatancy, which took place under compressive stress Detailed study of one rock, Westerly granite, showed that changes in resistivity and, hence, porosity with stress were insensitive to effective pressure, when stress was normalized with respect to fracture stress This suggests that fracture occurred at a critical crack porosity that was pressure independent The changes in resistivity with stress that accompany frictional sliding on a fault are insignificant when the measurement volume contains the fault, even though faulted rock under pressure can support high stress
237 citations
TL;DR: The major evidence bearing upon sub-critical flaw growth in structural materials is reviewed and discussed in this paper, focusing on the growth of pre-existing flaws at operating stresses less than the net section yield strength, from both the separate and combined effects of fatigue and aggressive environments.
217 citations
TL;DR: In this paper, a method is described to study subcritical crack growth in ceramic materials and large macroscopic size cracks were used and quantitative crack velocity measurements were made on glass and sapphire as a function of applied force, temperature and environment.
Abstract: A method is described to study subcritical crack growth in ceramic materials. Large, macroscopic size cracks were used and quantitative crack velocity measurements were made on glass and sapphire as a function of applied force, temperature and environment. The measured crack velocity was a complex function of stress and water vapor concentration in the environment and portions of the data could be adequately explained by the stress corrosion theory of Charles and Hillig.
198 citations
TL;DR: Theoretical study of plate thickness effect on bending stress distribution around slotted cracks is presented in this article, where the authors study the effect of the thickness of the plate on the stress distribution.
Abstract: Theoretical study of plate thickness effect on bending stress distribution around slotted cracks
157 citations
TL;DR: In this article, a model of fatigue crack growth is presented based on the analysis of plastic yield at a notch in terms of dislocations which has been given by Bilby et al. (1963).
Abstract: A model of fatigue crack growth is presented based on the analysis of plastic yield at a notch in terms of dislocations which has been given by Bilby et al. (1963). This analysis is extended to the case of relaxation of the applied stress, and the reverse plastic displacement at the crack tip is calculated. Reasons are given for equating this quantity with the amount of crack growth, and hence a growth law is obtained. The rate of growth for a specimen of finite width is similarly derived. In both cases, for low stresses, the growth per cycle is proportional to the square of the elastic stress intensity, while for higher stresses, terms involving the fourth and higher powers of stress enter. The model is expected to be applicable to the slip-band type of growth called stage I by Forsyth (1961) and to the ductile component of stage II growth. Although the model is developed only for shear cracks, there are indications that it may be at least approximately applicable to tension-compression fatigue,...
100 citations
TL;DR: In this article, the authors developed a new method for solving the two-dimensional stress problems using a digital computer and calculated the stress distribution of a rectangular plate subjected to symmetrical loading and the stress concentration factors of a semi-infinite plate having a circular notch or a V-notch under tension.
Abstract: In this paper, the author has developed a new method for solving the two-dimensional stress problems using a digital computer. As examples, he calculated the stress distribution of a rectangular plate subjected to symmetrical loading and the stress concentration factors of a semi-infinite plate having a circular notch or a V-notch under tension. The stress distributions of an infinite plate subjected to a point load are used as a fundamental solution in this method. To satisfy the boundary conditions, the body force distributed on the boundary curve imagined in an infinite plate is used.
79 citations
TL;DR: In this paper, the authors investigated the initiation of fatigue cracks in relation to the contact stresses caused by fretting and found that the reduction of fatigue strength is mainly attributed to the stress concentration caused by the frictional force due to fretting.
Abstract: It has been known that the fatigue strength related to fretting is significantly reduced and that non-propagating fatigue cracks are often observed in the superficial layer of fretted area. In order to clarify the causes of such phenomena, the initiation of fatigue cracks is investigated in relation to the contact stresses caused by fretting. The main results obtained are as follows. (1) The reduction of fatigue strength is mainly attributed to the stress concentration caused by the frictional force due to fretting. Fatigue cracks are located at the stress concentrated area. (2) The fatigue cracks show inclinations to the surface, and the direction can also be explained by the contact stresses.
TL;DR: In this article, the initial stages of crack growth within various arrays of elongate open flaws were studied in photoelastic models subjected to uniaxial compression, and the results suggest a possible mechanism for some of the seismic events associated with shallow-focus earthquakes.
TL;DR: Unreinforced circular cutouts effects on buckling behavior of circular cylindrical shells under axial compression, using photo-elastic plastic shells as discussed by the authors, have been shown to be effective in the case of rigid shells.
Abstract: Unreinforced circular cutouts effects on buckling behavior of circular cylindrical shells under axial compression, using photoelastic plastic shells
TL;DR: In this article, the true stress-true strain behavior of polyoxymethylene, n(-CH2O), as an example of a bulk semi-crystalline polymer, has been investigated for constant hydrostatic environmental pressures from 1 atmosphere to 8 kilobars with the principal objectives of elucidating the factors controlling flow and fracture.
Abstract: The true stress-true strain behavior of polyoxymethylene, n(-CH2O), as an example of a bulk semi-crystalline polymer, has been investigated for constant hydrostatic environmental pressures from 1 atmosphere to 8 kilobars with the principal objectives of elucidating the factors controlling flow and fracture. Experiments were conducted in uniaxial tension at room temperature and constant strain rate. The tensile observations were supplemented by measurements of bulk compressibility and stress relaxation behavior at pressure.
In contrast with metals and inorganic compounds, the modulus, yield stress and fracture stress of POM increase strongly with pressure by a factor of approximately three at 8 kilobars. The modulus increase is shown from the stress relaxation measurements to be associated with a pressure-induced increase in the β-transition temperature which points to the potential usefulness of the concept of pressure-temperature super-position of mechanical behavior. The characteristics of the pressure dependence of the yield stress demonstrate that yield criteria based on continum mechanics considerations, including the Mohr or Coulomb-Navier criterion, are not valid for general deformation (non-plane strain) conditions in this polymer. The concept of a critical volume change determining the initiation of yielding is suggested to be applicable to semi-crystalline polymers. Comparison with analogous changes in yield stress with temperature points to an increasing contribution to the control of yielding by the initially disordered regions with increasing pressure or decreasing temperature. The fracture behavior observed at pressure eliminates the concepts of a critical stress as a fracture criterion for POM and of a simple reduction in normal stress at points of stress concentration as the principal effect of the applied pressure on fracture.
TL;DR: In this paper, the effects of mean stresses on the initiation of minute fatigue cracks in superficial layer and on their propagation to complete fracture, under controlled conditions of fretting slip amplitude, are investigated using the fretting fatigue testing machine described in the previous paper.
Abstract: A series of investigations is proceeding to clarify the phenomena of fretting fatigue. In the present paper, the effects of mean stresses on the initiation of minute fatigue cracks in superficial layer and on their propagation to complete fracture, under controlled conditions of fretting slip amplitude, are investigated using the fretting fatigue testing machine described in the previous paper. Annealed specimens and induction hardened specimens made of carbon steel are employed in the experiment. The following are the main results obtained. (1) The range of alternating stress amplitude at which no fatigue cracks initiate is not affected by the mean stresses, but is a constant value depending on the materials. The fatigue limit can be raised by induction hardening. (2) A fatigue limit against propagation of minute cracks (maximum alternating stress amplitude at which the minute fatigue cracks do not propagate) is cosiderably affected by the mean stresses, and it decreases with the increase of mean stress.
TL;DR: In this paper, the interaction between two parallel cracks with a variable overlap distance in a tensile stress field was investigated and the principal stress trajectory patterns and the curves of constant shear stress for the interacting crack tips were presented.
Abstract: The interaction between two parallel cracks with a variable overlap distance in a tensile stress field was investigated. The principal stress trajectory patterns and the curves of constant shear stress for the interacting crack tips are presented. It was found that a) the stresses at the interacting crack tips are smaller than the noninteracting or outer crack tips and b) when there was a substantial overlap, the two cracks acted as one, i.e. the stresses at the outer tips were greater relative to those of either crack present by itself. Also, the propagation paths for the interacting crack tips are discussed for both conchoidal and cleavage fracture.
01 Jan 1968
TL;DR: Composite tensile failure modes, failure load prediction, experimental data and statistical analysis of stress concentration effects are discussed in this article, where failure load predictions and failure load models are discussed.
Abstract: Composite tensile failure modes, discussing failure load prediction, experimental data and statistical analysis of stress concentration effects
TL;DR: In this paper, the authors extended the Dugdale model to include the influence of the stress-strain curve on the plastic-zone size and subsequently on the fracture strength of the plate.
TL;DR: The microhardness measurements of Magnesia-stabilized zirconia indicate both solution hardening and solute segregation and help to explain the physical behavior of this system as the amount of MgO is varied as discussed by the authors.
Abstract: Stabilized zirconias exhibit pronounced photoelastic effects when viewed with transmitted polarized light. Thin sections reveal stress concentrations around pores and inclusions and at grain boundaries. The yield point of these materials, at some high temperature, is exceeded and plastic deformation tends to relieve these stress concentrations. The microhardness measurements of magnesia-stabilized zirconia indicate both solution hardening and solute segregation and help to explain the physical behavior of this system as the amount of MgO is varied.
TL;DR: In this article, a solution of the basic equations for notches and cracks in shear strained prisms is derived in closed form, valid for the same form of boundary for all possible nonlinear stress-strain-laws and all loading intensities.
Abstract: I n order to investigate the mechanism of physically nonlinear stress concentration and crack propagation, a solution of the basic equations for notches and cracks in shear strained prisms is derived in closed form, valid for the same form of boundary for all possible nonlinear stress-strain-laws and all loading intensities. The boundary consists of two parallel straight flanks and a cycloid.
TL;DR: In this paper, a dislocation model which is appropriate for discussing the propagation of fatigue cracks from notches of elliptical or V-shaped profiles is presented, and the principal conclusion is that the rate of crack growth is proportional to the fourth power of the stress intensity factor, deduced from the notch geometry.
Abstract: A dislocation model which is appropriate for discussing the propagation of fatigue cracks from notches of elliptical or V-shaped profiles is presented. The principal conclusion is that the rate of crack growth is proportional to the fourth power of the stress intensity factor, deduced from the notch geometry. Detailed predictions are made about the variation of the rate of crack growth with the parameters governing the notch shape.
TL;DR: In this paper, the effects of size on the fatigue limits and the branch points of electropolished notched specimens were investigated, and the effect of work hardened layers due to machining was also investigated.
Abstract: The effects of size on the fatigue limits and the branch points of electropolished notched specimens were investigated. To clarify the effect of work hardened layers due to machining, the specimens having work hardened layers were also investigated. The main results obtained are as follows. 1) The necessary condition of non-propagating cracks is to take the root radius of a notch under a critical value ρ0 which is a material constant. ρ0 is about 0.5 mm for the 0.23% carbon steel. 2) The repeated maximum stress at the root of a notch at the fatigue limit based on crack initiation is determined only by the stress gradient x=(1/σ) (dσ/dx) at the root of the notch. 3) The size effect of the fatigue limits based on fracture in the range of existing of nonpropagating cracks is explained by the fact that the fatigue limits are determined from the stress concentration factor at the branch point α|ρ=ρ0.
TL;DR: In this paper, the authors found that the susceptibility of polycrystalline zinc to embrittlement by liquid mercury is markedly increased by alloying with as little as 0.05 or 0.2 at.r.s.
TL;DR: In this article, the authors used a piezoelectric crystal to convert the elastic stress wave into an electrical signal, which can be used to detect the onset of crack growth.
TL;DR: In this paper, a model for crack nucleation based on this conclusion was developed quantitatively and a simple relationship between the number of cycles to nucleate a crack and the applied, plastic, strain range was predicted.
Abstract: From previous observations of the surfaces of metals cycled in high strain fatigue, the mechanism of crack nucleation is considered a plastic instability phenomenon. A model for crack nucleation based on this conclusion is now developed quantitatively and a simple relationship between the number of cycles to nucleate a crack and the applied, plastic, strain range thus predicted. Since the model is valid for any material capable of plastic deformation, plasticine has been cycled in reversed bending to test its prediction. Cracks were observed to form in the plasticine by puckering of the surface at stress concentrations, in direct confirmation of the model. Moreover, the crack nucleation measurements on the plasticine and data on metals, taken from the literature, are considered to be in reasonable agreement with the prediction of the model.
TL;DR: In this paper, the response of a penny shaped crack embedded in an infinite, isotropic elastic medium to an incident plane harmonic shear wave is considered and the singular behavior of the stress components at the edge of the crack is discussed.
TL;DR: In this article, the authors investigated the subcritical crack growth behavior during the fracture toughness testing of several structural alloys and compared with the crack propagation characteristics observed under fatigue loading conditions.
TL;DR: In this article, two sets of equations have been derived which describe the internal stress distribution within reinforced plastics subjected to a force normal to the direction of its internal filaments, and each set is applicable over a complete range of loading which includes both elastic and plastic stresses.
Abstract: Two sets of equations have been derived which describe the internal stress distribution within reinforced plastics subjected to a force normal to the direction of its internal filaments. One set of equations is applicable to reinforced plastics with less than 68% filament by volume and the other to reinforced plastics with more than 68% filament. Each set is applicable over a complete range of loading which includes both elastic and plastic stresses. It is found that when reinforced plastics have less than 68% filament by volume only one plastic zone develops in a generic section before the cross section becomes entirely plastic. Additional plastic zones develop when reinforced plastics have more than 68% filament by volume. A simple expression for the elastic stress concentration factor was also found.
TL;DR: In this article, a method of successive approximations utilizing analytic stress functions of the complex variable z, in the manner of the Schwartz Alternating Method, has been used to obtain the solution of the stress distribution around two circular holes of unequal radii in an equal biaxial stress field of an infinite plate.
Abstract: A method of successive approximations utilizing analytic stress functions of the complex variable z, in the manner of the Schwartz Alternating Method, has been used to obtain the solution of the stress distribution around two circular holes of unequal radii in an equal biaxial stress field of an infinite plate. The stress functions up to a third approximation are obtained in all detail for one numerical example and a chart for a wide range of hole and distance parameters is developed for practical use. It is believed that this basic solution for two holes is a preliminary attempt toward the solution of stress concentration problems in the perforated components in pressure vessels in the area of reactor structures. It is also believed that this solution may be used to obtain solutions to more complicated hole patterns.