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1.
V. M. Tikhomirov 《Journal of Applied Mechanics and Technical Physics》2008,49(5):864-871
Crack propagation under alternating loading is investigated. Relations between the growth rate of a fatigue defect and loading
parameters and the expression for the stress intensity factor are derived for compression of a cracked solid taking into account
the possible contact of the crack faces. A model for the deformation of a small region near the crack tip is proposed which
allows one to formulate the conditions of residual opening of a growing fatigue crack. The experimental data obtained in tests
of steel samples are compared with the results of calculation using the developed procedure.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 5, pp. 190–198, September–October, 2008. 相似文献
2.
A. N. Guz 《International Applied Mechanics》2011,47(2):121-168
Major results on the mechanics of crack propagation in materials with initial (residual) stresses are analyzed. The case of
straight cracks of constant width that propagate at a constant speed in a material with initial (residual) stresses acting
along the cracks is examined. The results were obtained, based on linearized solid mechanics, in a universal form for isotropic
and orthotropic, compressible and incompressible elastic materials with an arbitrary elastic potential in the cases of finite
(large) and small initial strains. The stresses and displacements in the linearized theory are expressed in terms of analytical
functions of complex variables when solving dynamic plane and antiplane problems. These complex variables depend on the crack
propagation rate and the material properties. The exact solutions analyzed were obtained for growing (mode I, II, III) cracks
and the case of wedging by using methods of complex variable theory, such as Riemann–Hilbert problem methods and the Keldysh–Sedov
formula. As the initial (residual) stresses tend to zero, these exact solutions of linearized solid mechanics transform into
the respective exact solutions of classical linear solid mechanics based on the Muskhelishvili, Lekhnitskii, and Galin complex
representations. New mechanical effects in the dynamic problems under consideration are analyzed. The influence of initial
(residual) stresses and crack propagation rate is established. In addition, the following two related problems are briefly
analyzed within the framework of linearized solid mechanics: growing cracks at the interface of two materials with initial
(residual) stresses and brittle fracture under compression along cracks 相似文献
3.
When a nonhomogeneous solid is melting from below, convection may be induced in a thermally–unstable melt layer. In this study,
the onset of buoyancy-driven convection during time-dependent melting is investigated by using similarly transformed disturbance
equations. The critical Darcy–Rayleigh numbers based on the melt-layer thickness, Ra
H,c, are found numerically for various conditions. For small superheats, the present predictions show that Ra
H,c is located between 27.1 and 4π
2 and it approaches the well-known results of the original Horton–Rogers–Lapwood problem. However, for high superheats, it
is dependent on the phase change rate λ and the relation of Ra
H,c λ = 25.89 is shown. 相似文献
4.
I. Miklashevich 《Theoretical and Applied Fracture Mechanics》2005,43(3):360-368
The problem of crack trajectory stabilization in composite material is investigated. The equation for a crack path is found from the variational principle. It is considered as a path along which the extreme amount of energy is generated during the destruction. This statement corresponds to the variational problem analogous to the Lagrange–d’Alembert principle of classic mechanics and to the Fermat principle in optic and acoustic. For a crack path in inhomogeneous medium, nonlinear differential equation is obtained. Stability of the crack propagation in the inhomogeneous medium is considered. In particular, a 2D crack propagating in a composite material is considered. The path of propagation is assumed to cross layers or fibres. For layered and piece-wise continuous composites, the resulting governing equation corresponds to different kind of Duffing’s equation. The bifurcations of the trajectory and instability of crack path are investigated numerically. Conditions of crack trajectory stabilization are found. Properties of the materials that stabilized the crack trajectory are found. 相似文献
5.
V. M. Mirsalimov 《Journal of Applied Mechanics and Technical Physics》2007,48(5):723-733
A mathematical model is constructed for crack nucleation in an isotropic fuel cell (heat-releasing solid material) attenuated
by a biperiodic system of cooling cylindrical channels with a circular cross section. Cracks are assumed to appear with increasing
heat-release intensity in the bulk of the material. The solution of the problem on equilibrium of an isotropic perforated
fuel cell with crack nuclei reduces to the solution of a nonlinear singular integral equation with a Cauchy-type kernel. The
solution of the latter equation yields the forces in the band of crack nucleation. The condition of crack nucleation is formulated
with allowance for the criterion of ultimate extension of bonds in the material.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 121–133, September–October, 2007. 相似文献
6.
Stress intensity factors and crack deviation conditions in a brittle anisotropic solid 总被引:1,自引:0,他引:1
S. A. Nazarov 《Journal of Applied Mechanics and Technical Physics》2005,46(3):386-394
For arbitrary anisotropy in the linear manifold of singular solutions generating square-root singularities of the crack tip
stress, a special basis is introduced that possesses the same properties as in the isotropic case and provides simple integral
representations for the attributes of the energy fracture criterion, in particular, the conditions of crack deviation from
a straight path.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 98–107, May–June, 2005. 相似文献
7.
A crack is represented as a continuous set of linear dislocations. Simple analytical expressions are obtained for the potential
and kinetic energies of the environment of moving cracks and the attached mass of cracks for an arbitrary form of the stress
applied to the crack P(x). It is shown that the indicated analytical expressions are bilinear integrals of the functions P(x)
and ∂P(x)/∂x. These integrals are calculated in explicit form for a constant stress over the entire crack length and the stress
due to the action of molecular adhesion forces in a narrow region near the crack openings. It is shown that the calculation
results does not depend on the form of molecular adhesion forces. The proposed approach to describing cracks and calculations
based on it has made it possible for the first time to obtain a complete analytical expression for the limiting crack propagation
velocity in elastic materials as a function of the main mechanical characteristics of such materials.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 4, pp. 158–166, July–August, 2009. 相似文献
8.
L. A. Tkacheva 《Journal of Applied Mechanics and Technical Physics》2008,49(5):853-863
Unsteady crack propagation is studied in the beam approximation. The Euler and Timoshenko models of beam theory are used.
Crack propagation is described using an energy balance equation.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 5, pp. 177–189, September–October, 2008. 相似文献
9.
A. M. Meirmanov 《Journal of Applied Mechanics and Technical Physics》2008,49(4):614-628
The problem of the nonisothermal joint motion of an elastic porous body and the fluid filling the pores is considered for
the case where the duration of the physical process is fractions of a second. A rigorous derivation of averaged equations
(equations not containing fast oscillating coefficients) based on the Nguetseng two-scale convergence method is proposed.
For various combinations of physical parameters of the problem, these equations include anisotropic nonisothermal Stokes equations
for the velocity of the fluid component and the equations of nonisothermal acoustics for the displacements of the solid component
or anisotropic nonisothermal Stokes equations for a single-velocity continuum.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 4, pp. 113–129, July–August, 2008. 相似文献
10.
E. V. Vtorushin 《Journal of Applied Mechanics and Technical Physics》2007,48(5):737-742
A homogeneous two-dimensional body with a crack of variable length is considered. At the crack edges, conditions are formulated
in the form of inequalities that describe mutual nonpenetration of the edges. The derivative of the elastic-energy functional
with respect to the length of the curvilinear crack is analyzed. It is shown that the derivative is independent of the crack
path, provided that the curve along which the crack propagates is reasonably smooth.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 138–145, September–October, 2007. 相似文献
11.
V. V. Ostapenko 《Journal of Applied Mechanics and Technical Physics》2007,48(6):795-812
A method for modeling the propagation of discontinuous waves over a dry bed using the first approximation of shallow water
theory is proposed. The method is based on a modified conservation law of total momentum that takes into account the concentrated
momentum losses due to the formation of local turbulent vortex structures in the fluid surface layer at a discontinuous-wave
front. A quantitative estimate of these losses is obtained by deriving the shallow water equations from the Navier-Stokes
equations with allowance for viscosity, which has a rapidly increasing effect in the turbulent flow regions described by discontinuous
waves. The stability of the discontinuous waves admitted by the modified system of conservation laws of shallow water theory
is examined. As an example, a comparative analysis is performed of the solutions of the dam-break problem obtained for the
classical and modified shallow water models.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 6, pp. 22–43, November–December, 2007 相似文献
12.
V. V. Mykhas’kiv N. D. Grilitskii I. O. Butrak 《Journal of Applied Mechanics and Technical Physics》2006,47(4):556-563
A three-dimensional wave field formed owing to diffraction of low-frequency waves on a curved crack in an infinite elastic
solid at a large distance from the defect is studied by the method of boundary integral equations. Direction diagrams of the
scattered field versus the excentricity of the crack surface and wavenumber are obtained for different directions of incidence
of planar longitudinal waves onto a gently sloping spheroidal crack.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 4, pp. 115–123, July–August, 2006. 相似文献
13.
The prediction of fluid-driven crack propagation in deforming porous media has achieved increasing interest in recent years, in particular with regard to the modeling of hydraulic fracturing, the so-called “fracking”. Here, the challenge is to link at least three modeling ingredients for (i) the behavior of the solid skeleton and fluid bulk phases and their interaction, (ii) the crack propagation on not a priori known paths and (iii) the extra fluid flow within developing cracks. To this end, a macroscopic framework is proposed for a continuum phase field modeling of fracture in porous media that provides a rigorous approach to a diffusive crack modeling based on the introduction of a regularized crack surface. The approach overcomes difficulties associated with the computational realization of sharp crack discontinuities, in particular when it comes to complex crack topologies including branching. It shows that the quasi-static problem of elastically deforming, fluid-saturated porous media at fracture is related to a minimization principle for the evolution problem. The existence of this minimization principle for the coupled problem is advantageous with regard to a new unconstrained stable finite element design, while previous space discretizations of the saddle point principles are constrained by the LBB condition. This proposed formulation includes a generalization of crack driving forces from energetic definitions towards threshold-based criteria in terms of the effective stress related to the solid skeleton of a fluid-saturated porous medium. Furthermore, a Poiseuille-type constitutive continuum modeling of the extra fluid flow in developed cracks is suggested based on a deformation-dependent permeability, that is scaled by a characteristic length. 相似文献
14.
A. P. Shabanov 《Journal of Applied Mechanics and Technical Physics》2009,50(4):684-690
A model for crack growth is proposed based on studies of the variation in the curvature radius at the crack tip during cyclic
loading. Relations are obtained between mechanical material characteristics, crack geometry, and the rate of crack growth
in a structure under cyclic loading.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 4, pp. 167–175, July–August, 2009. 相似文献
15.
D. N. Gorelov 《Journal of Applied Mechanics and Technical Physics》2007,48(2):184-191
A general formulation of a nonlinear initial-boundary problem of an unsteady separated flow around an airfoil by an ideal
incompressible fluid is considered. The problem is formulated for a complex velocity. Conditions of shedding of vortex wakes
from the airfoil are analyzed in detail. The proposed system of functional relations allows constructing algorithms for solving
a wide class of problems of the wing theory.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 48–56, March–April, 2007. 相似文献
16.
Mihaela Popescu 《Acta Mechanica Sinica》2009,25(3):311-318
This paper presents a computational model for the fluid dynamics in a fractured ductile pipe under high pressure. The pressure profile in front of the crack tip, which is the driving source of crack propagation, is computed using a nonlinear wave equation. The solution is coupled with a one dimensional choked flow analysis behind the crack. The simulation utilizes a high order optimized prefactored compact-finite volume method in space, and low dispersion and dissipation Runge-Kutta in time. As the pipe fractures the rapid depressurization take place inside the pipe and the propagation of the crack-induced waves strongly influences the outflow dynamics. Consistent with the experimental observation, the model predicts the expansion wave inside the pipe, and the reflection and outflow of the wave. The model also helps characterize the propagation of the crack dynamics and fluid flows around the tip of the crack. 相似文献
17.
The effect of contact between the sides of a rectilinear crack in the planeR
2={x: x3=0} on the characteristics of the fallure mechanics is studied for the case in which the crack is affected by harmonic tensile-compression
waves and shifts. The surfaces of the crack may assume any orientation relative to the direction of propagation of the waves.
The presence of friction in the zone of contact of the sides of the crack is taken into account. The method of solving the
problem stated is iterative in nature and is based on the solution of a sequence of boundary integral equations for the Fourier
coefficients of the displacement discontinuity vector and the contact force vector. It is also corrected at each step of the
solution so as to satisfy one-sided restrictions in the zone of contact.
Kharkov Highway Technical Institute, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 2, pp. 70–75, February,
1999. 相似文献
18.
O. P. Alekseenko A. M. Vaisman A. F. Zazovskii 《Journal of Applied Mechanics and Technical Physics》1998,39(3):454-461
An algorithm that permits one to find a solution of the Perkins-Kern-Nordgren problem for standard regimes of hydraulic fracturing
is suggested. The universal qualitative specifics, of the behavior of a crack is shown; in particular, the asymptotics of
crack opening at the tip is found, and it is shown that the character of the crack is determined by the rate of increase or
decrease in the crack size.
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 149–157, May–June, 1998. 相似文献
19.
A. I. Khromov A. A. Bukhan'ko O. V. Kozlova S. L. Stepanov 《Journal of Applied Mechanics and Technical Physics》2006,47(2):274-281
Based on the theory of an ideal rigid-plastic body, an approach is formulated for determining fracture constants on the basis
of standard mechanical tests on uniaxial extension of plane and cylindrical samples. Instead of the experimentally determined
characteristics of fracture of materials (dimensionless elongation and constriction of the sample during its fracture), two
invariant tensor characteristics of the degree of sample deformation are introduced, which correspond to the moment of origination
of a macrocrack and critical strain at the crack tip determining the process of crack propagation.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 147–155, March–April, 2006. 相似文献
20.
A. A. Dolzhkovoi N. N. Popov V. P. Radchenko 《Journal of Applied Mechanics and Technical Physics》2006,47(1):134-142
The physically and statistically nonlinear problem of steady-state creep for a thick-walled tube loaded by internal pressure
is solved in the third approximation using the small-parameter method. The variances of random creep strain rates and displacements
are calculated. The results obtained are compared with the solution of the same problem in the first and second approximations.
A reliability assessment method for the tube using the strain failure criteria is proposed.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 161–171, January–February, 2006. 相似文献