Ya. L. Ivanyts’kyi

Methods for the Construction of the Kinetic Diagrams of Fatigue Fracture for Steels Under the Conditions of Trаnsverse Shear with Regard for the Friction of Crack Lips

We propose the design of a specimen for the investigation of the fatigue fracture of steels under transverse shear. A formula for the determination of the stress intensity factor with regard for the friction of crack lips is obtained with the use of the finite-element method. The methods aimed at the construction of the kinetic diagrams of fatigue fracture under the conditions of transverse shear are developed and tested on specimens of 65G structural steel. We plot the kinetic diagram of fatigue fracture and approximate its middle segment by a linear dependence in the established parameters.

Influence of the Stress-Strain State on the Distribution of Hydrogen Concentration in the Process Zone

We propose a theoretical-experimental approach to the determination of the concentration of hydrogen in the process zone. The plots of the dependences of the concentration of hydrogen on the mechanical characteristics of the material and external load are constructed.

Determination of the Local Strains Near Stress Concentrators by the Digital Image Correlation Technique

We analyze the specific features of determination of the local strains in materials in the vicinity of stress concentrators of different radii by the digital image correlation method. The dependences of the critical local strains on the spacing used for their measuring in smooth specimens and specimens with stress concentrators and fatigue cracks are established. Recommendations concerning the choice of the optimal spacing for measuring local strains are presented. The stress-strain diagrams of 65G steel are constructed on the “true-stress–local strain” coordinates.

Investigation of the Kinetics of Fatigue Macrocracks Under Transverse Shear

We study the kinetics of shear macrocracks under the conditions of fatigue fracture by transverse shear of thermally hardened 65G steel with a troostite-sorbite structure for low-, middle-, and high-amplitude cyclic loads. We plot the kinetic diagrams of fatigue fracture with regard for the friction of the faces of a shear crack within the range of its growth rates covering up to six orders of magnitude. On the basis of the constructed dependence, we determine the principal and additional characteristics of cyclic crack resistance. We also study the contact interaction of the faces of fatigue cracks and the fractographic features of fracture under the conditions of low- and high-amplitude deformation by cyclic transverse shear.

Optical-Digital Method for the Determination of Strain Fields in Local Areas of Reinforced-Concrete Bridges

By using the procedure of digital correlation image processing, we develop a portable optical-digital correlator for the determination of the distribution of strains in reinforced-concrete beams under static loading. We present the distributions of strains for a longitudinal beam in the region of the joint obtained in the course of experimental investigations of a model of the bridge.

Determination of the Parameters of Crack Resistance for 17g1s Steel Under Transverse Shear

We determine the static crack resistance of compact Richard’s specimens made of 17G1S steel and the critical crack opening displacement under the conditions of transverse shear (mode II). The specimens are tested under cyclic loading. Richard’s specimens are modernized with an aim to improve the conditions for the initiation and growth of mode II cracks. By using the digital image correlation method, we determine the distribution of strains near the notch tip.

Investigation of the Deformation and Fracture of Composites with the Help of Electronic Speckle Interferometry

We develop a procedure for the experimental investigations of the deformation and fracture of specimens of coal-plastic composites. A schematic diagram of the experimental installation is presented and the results of investigations are analyzed. We also show the efficiency of electronic speckle interferometry for the detection of defects in coal-plastic composites and estimation of their critical stress-strain state.

Determination of the Durability of Ferroconcrete Bridge Beams Reinforced by Composite Strips

We propose a procedure for the evaluation of the service life of ferroconcrete beams reinforced by composite strips based on the energy approach and develop technical tools for measuring displacements over the height of the beam with the use of the method of digital image correlation. An algorithm of image processing for the determination of local strains is proposed. We performed experimental investigations of a reinforced ferroconcrete beam under cyclic loading and established the number of cycles to its fracture.

Acoustic Investigations of the Strained State of Hydrogenated 09G2S Steel

We study the acoustic properties of inhomogeneous plastically deformed specimens made of 09G2S steel. The specimens with residual strains were successively subjected to heat treatment and hydrogenation from the gas phase. After each procedure, we measured the space distributions of the velocity of longitudinal acoustic waves. We also analyzed the mechanisms of changes in the velocity in the course of hydrogenation in the region of the specimen with residual strains.

Determination of the Durability of Elements of Power-Generating Equipment with Regard for the Influence of Working Media

We propose an engineering approach to the analysis of the strength and durability of structural elements of power-generating equipment with regard for the influence of hydrogen-containing media, high pressures, and elevated temperatures. We study the stress-strain state of a boiler drum made of 22K steel, under the operating conditions with regard for the hydrogenation of its wall and the actual geometry of the drum. We compute the parameter of accumulated damage to the drum metal for different operating conditions. It is shown that hydrogen accelerates the accumulation of defects and reduces the operating time of the metal by 20–30% in the case of a scheduled shutdown of the boiler and by 30–40% in the case of its emergency shutdown.