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The fracture energy of 12Cr1MoV steel specimen with V-shaped, U-shaped and I-shaped notches under impact loading was measured and analysed. The results were described using three common approaches to ductile-brittle fracture: force-based, energy-based and strain-based. Within the stage-wise approach of physical mesomechanics of materials, the rate of increase/decrease of load at the stage of initiation and propagation of a macroscopic defect was evaluated, providing a good correlation with the work of fracture. The excitable cellular automata technique was applied to simulate the deformational behaviour of the specimens with different shape of notches. It was demonstrated that in the case of the blunted notch, the maximum impact toughness is facilitated by a more uniform distribution of the load along the notch, which hinders brittle fracture at lower testing temperature. For the specimen with the sharp I-notch, the bands of localised shear are oriented normally to the loading axis, inhibiting macroscopic localisation of strain and crack propagation. For this reason, the impact toughness of the specimen with the I-notch appeared to be higher than that of the V-notched one. Using the fractographic analysis and the size of shear lips as a quantitative fracture parameter, a physical-mechanistic scheme of fracture was suggested for the case of enhanced localised plasticity near the stress riser. [ABSTRACT FROM AUTHOR]

We reveal the physicomechanical regularities of the accumulation of surface defects on the basis of the computer analysis of photographic images of the surfaces of deformed specimens. The main laws of the pore formation in D16cht alloy are established by the method of strain measurements. We also demonstrate the existence of a physicomechanical relationship between the deformation of loosening and the accumulation of defects on the surface of the material. [ABSTRACT FROM AUTHOR]

Impact loading curves and fracture energy of the notched 12Cr1MoV ductile steel specimens are analysed. The qualitative description and quantitative parameters are obtained for major stages of ductile and brittle fracture depending on the shape of the notch and the stress stiffness ahead. It was shown that a zone with enhanced plasticity forms in the vicinity of V-, U- and I-shaped notches at 20 °C testing temperature, giving rise to ductile fracture. The stress stiffness at the notch tip increased with testing temperature reduced to −40 °C. We demonstrated that the size of shear lips on a fracture surface is a quantitative characteristic of fracture. Using this approach, which is close by nature to non-linear fracture mechanics, together with the quantitative description of fracture surfaces, a physical-mechanical scheme of the specimen fracture was suggested for the case of enhanced and localized (constrained) plasticity near the stress concentrator tip. [ABSTRACT FROM AUTHOR]

The evaluation of crack initiation and growth at microscopic scale is a crucial issue for the safety assessment of macroscopical fractures. In the present paper, the crack propagation in 17Mn1Si steel macroscale is investigated by taking into account the microstructural damage accumulation in polycrystalline solids. The revealed regularities are in good agreement with the concept of physical mesomechanics, which allows obtaining a generalized view of the material deformation and the failure process in the vicinity of the concentrator, which fulfills the limiting, initial and physical conditions and allows obtaining the generalized regularities in deformation and failure of 17Mn1Si steel. [ABSTRACT FROM AUTHOR]

The main features of crack initiation in main gas pipeline steel after forty years of operation with impact loading are studied. The energy capacity of gas pipeline material breakdown is studied for different directions of specimen cutting. Each stage of the impact loading diagram is specified by self-organization of deformation levels, and the shape of the diagram makes it possible to describe the stages of breakdown. [ABSTRACT FROM AUTHOR]

Features of statically deformed steel 17G1S strain hardening after forty years of operation are studied. Physicomechanical interpretation is proposed for use of indentation data in order to evaluate steel 17G1S deformation properties at different scale levels. It is demonstrated by experiment that sensitivity of indentation methods depends on participation of different material structural levels in deformation, and also presence of scattered damage. [ABSTRACT FROM AUTHOR]

We study the impact toughness of three batches of Charpy specimens cut out from the rollers of continuous-casting machines. We determine the stages of dynamic deformation and fracture of bimetallic and monometallic specimens on the micro-, meso-, and macrolevels. With the help of scanning and transmission microscopies, we study the specific features of the micromechanisms of plastic deformation and fracture for steels with ferrite-pearlite (35G2) and ferrite-martensite (18Kh11MNFB) structures. In addition, we analyze their impact toughness with regard for these features. [ABSTRACT FROM AUTHOR]

The effect of multiple cracking for steel 25Kh1MF on its deformation behavior is analyzed. Fractal theory is used to develop new methods of digital diagnosis of deformation in material with multiple defects. It is established that the fractal dimension of multiple cracking increases uniformly with an increase in cracking damage area. Physical features of these principles are analyzed. [ABSTRACT FROM AUTHOR]

The problems of engineering diagnostics of the state of rollers of continuous-casting machines are analyzed. We separately consider the problems of evaluation of the degradation of 25Kh1M1F steel (material of the rollers) after thermal cycling and establish the physicomechanical characteristics most sensitive to the influence of in-service factors. By the methods of destructive and nondestructive testing, we study the deformation behavior of steel in the intact state and after thermal cycling. The conformity of plastic yield of the material on different structural levels is demonstrated. The method for estimation of the degradation of materials according to the dispersion of the main chemical element is improved. [ABSTRACT FROM AUTHOR]

It is shown that the impact toughness of 25Kh1M1F ferritic-pearlitic steel increases as testing temperature increases from 20 to 375°C. This is connected with the increase in its plasticity promoting the increase in the crack resistance of the material at 375°C. This is why this type of steel can be used under high-temperature conditions. [ABSTRACT FROM AUTHOR]

Abstract: It was found that under the thermal cycle loading two interrelated process take place. In the material inner layers redistribution of dislocation and formation of sufficiently stable structure with the less dislocation density take place. Thus, the level of micro-stresses in the metal on the specimens surface and micro-hardness increases, which results in the elasticity exhaustion decrease of the metal micro-plastic deformation resistance. Localization of the micro-plastic deformations causes accumulation of the damage and initiation of microcracks. [Copyright &y& Elsevier]