Cracks’ closure in 3-D fracture dynamics: the effect of relative location of two coplanar cracks

In this paper, the problem of two equal coplanar cracks with allowance for the crack faces contact interaction was investigated. The problem of the cracks located in homogeneous, isotropic, and linearly elastic solid subjected to normally incident tension–compression wave is solved by the boundary integral equations method. The influence of the distance between two cracks on the stress intensity factors (opening mode and transverse shear mode) is studied for a range of wave numbers. The results are compared with those obtained neglecting cracks’ closure.     

Stress-intensity factors for materials with interface cracks under harmonic loading

The paper studies the distribution of the mode I, II, and III stress-intensity factors (SIFs) for a penny-shaped interface crack in a bimaterial under normal harmonic loading. The dependence of SIFs on the type of a wave (compression–dilatation or shear), loading frequency, and the mechanical properties of the bimaterial is analyzed     

Mechanics of crack propagation in materials with initial (residual) stresses (review)

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     

Analysis of the vibrationally induced dissipative heating of thin-wall structures containing piezoactive layers

A strongly non-linear dynamic problem of thermomechanics for multilayer beams is formulated based on the Kirchhoff–Love hypotheses. In the case of harmonic loading, a simplified formulation is given using a single-frequency approximation and the concept of complex moduli to characterise the non-linear cyclic properties of the material. As an example, the problem of forced vibrations and dissipative heating of a roller-supported layered beam containing piezoactive layers is solved. Different aspects of thermal, mechanical and electric responses to the mechanical and electric excitations are addressed. Dissipative heating due to electromechanical losses in the three-layer beam with piezoelectric layers is studied. It is assumed that the structure fails if the temperature exceeds the Curie point for piezoceramics. Using this criterion, the fatigue life of the structure is estimated. Limitations of the approximate monoharmonic approach are also specified.     

On dynamical fracture mechanics in the case of polyharmonic loading by SH-waves

We solve a fracture-mechanics problem for a cracked material under polyharmonic loading (waves of various lengths propagating through an elastic material). The frictional contact interaction of the finite crack edges in a plane is analyzed for the case of normal incidence of two harmonic shear waves with different frequencies. The forces of contact interaction and displacement discontinuity are determined. The effect of the wave frequency on the stress intensity factor for different normalized wave numbers is examined     

7-Aryl-3-(hydroxymethyl)-5-oxo-1,2,3,5-tetrahydro[1,2,4]triazolo[1,5-a]pyridine-6,8-dicarbonitriles: Synthesis and Predicted Biological Activity

Russian Journal of General Chemistry - Aminomethylation of 1,6-diamino-4-aryl-2-oxo-1,2-dihydropyridine-3,5-dicarbonitriles under the action of excess of formaldehyde in ethanol has led to the...     

Effect of contact interaction of the crack faces for a crack under harmonic loading

This paper is concerned with dynamic problems in fracture mechanics for elastic solids having cracks with contacting faces. The contact problem for a penny-shaped crack with a nonzero initial opening under normally incident harmonic wave is solved by the method of boundary integral equations. The solutions are compared with those that neglect the contact interaction of the crack faces. Results are presented for different values of the initial crack opening Presented at the 6th International Conference on Modern Practice in Stress and Vibration Analysis (Bath, United Kingdom, September 5–7, 2006). Published in Prikladnaya Mekhanika, Vol. 43, No. 7, pp. 125–131, July 2007.