Surface Phenomena in the Deformation and Fracture of Metals

Likhtman, V. I.; Shchukin, Eugenii D

doi:10.1070/rc1960v029n10abeh001255

Cited by 11 publications

(7 citation statements)

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“…Sub-micromechanical tests by method of continuous indentations using Berkovich indenter [5] have shown the anomalous adsorption reduction of strength at the grain boundaries of the Al alloy. The tendency towards considerable decrease in strength is caused by the presence of the so-called "Rehbinder effect" [6]. The distinctions of the indenter prints on Al alloy at the initial stage of diffusion are shown on Figure 10.…”

Section: Resultsmentioning

confidence: 97%

Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Khoklova

2013

MSF

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Peculiarities of formation of solid-state joining of the parts for bimetallic heat exchanger are considered. For solid-state activation of the surfaces, being joined, the layer-activator (liquid gallium) is used. Inter-granular segregation of an activator along the grain of the alloy-matrix is rapid and deep, which leads to polygonal structure in the diffusion zone. A negative fact for such joints is the brittleness of materials after intermetallic phase transformation of the chemical elements of alloy-matrix with gallium. The joint formed with an increasing of volume of the diffusion zone after rotation of newly formed phases at growth. Rotation of grains leads to emergence of high local internal stresses. Excess of an activator may be a reason for generation and distribution of main cracks. Indentation allows recording an abnormal decrease of the micro-hardness in grain boundary area. Obtained data of the Young's modulus, micro-hardness and coefficient of plasticity, with spectral mapping of chemical elements and phase analysis are allowed to exactly specify structural components that are the initiators of the materials stress state and are the reason for local cracks.

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Section: Resultsmentioning

confidence: 97%

Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Khoklova

2013

MSF

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“…7. The efficiency of determination of the influence of a medium significantly depends on the strain rate [24]. For highstrength materials of shrouds, the optimum strain rate is 250-300 %/min.…”

Section: A Procedures For Investigation Of Heat Release Under Strain Amentioning

confidence: 99%

Two methods of investigation of the influence of hydrogen on the propagation rate of a crack and behavior of fracture of high-strength steels

Balyts’kyi¹

1998

Mater Sci

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We present two methods for the investigation of the influence of hydrogen on the propagation rate of a crack and behavior of fracture of high-strength steels. The method for investigation of the influence of electrolytic hydrogenation on a subcritical growth of a crack in high-strength steels is based on the use of simple beam specimens of a certain geometry and on the application of lateral loading in such a way that the stress intensity factor can be constant at the tip of a preliminary induced crack. The method is of great importance for the performance of comparative experiments in evaluating the influence of active media and structural anisotropy of specimens made of high-strength steels with limited sizes on their corrosion crack resistance. Typical examples of the application of the method to investigation of the role of electrolytic hydrogenation in subcritical propagation of cracks and their branching in highstrength steels are given. The method for investigation of heat release under strain and fracture of hydrogenated specimens involves the use of microcalorimetric devices, which allow one to study the influence of hydrogenation on peculiarities of the kinetics of elastic and plastic strains of high-strength steels. We illustrate the efficiency of the method proposed by plotting the "load--elongation" curves and corresponding (in time) characteristics of heat release power in the process of strain and fracture of specimens made of a high-strength steel.Under actual service conditions of a structure with nonpropagating cracks, a long-term influence of the medium together with the action of mechanical stresses can lead to the start and growth of cracks that result in fracture of highly loaded components.In this connection, methods for investigation of the influence of aggressive media at the initial and subcriticalgrowth stages as well as behavior of fracture of high-strength steels in the range of significant plastic strains (up to the creation of large areas of newly made surfaces) are of great importance. The possibility of simultaneous electrolytic hydrogenation of materials is extremely important because, in many cases, it simulates actual service conditions of highly loaded components made of high-strength materials. A Method for Investigation of the Influence of Electrolytic Hydrogenation on the Subcritical Growth of Cracks in High-Strength SteelsWhile investigating corrosion cracking, we consider the method according to which the stress intensity factor becomes stable due to a designed loading scheme and the corresponding choice of an optimum geometry of a specimen as a promising one.Limited thickness of actual highly loaded components (in particular, shrouds of turbogenerators) makes it impossible to use other types of specimens, e.g., disk specimens [1], which would ensure a given constant value of the stress intensity factor. For this reason, we take prismatic rectangular specimens with lateral cracks which are simple to produce and involve small material consumption.As a theoretical foundatio...

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“…Due to the limitation of the conventional water-based fluids, the use of non-aqueous fracturing fluids (e.g., super-critical CO 2 ) instead of water has received a great deal of attention in the stimulation operation. − The injection of CO 2 into shale reservoirs leads to CO 2 sequestration that can help reduce the current emissions of CO 2 gas to the atmosphere. When shale absorbs CO 2 , CO 2 will move along the shale fracture systems, replacing naturally existing CH 4 because of the higher chemical potential. , Moreover, the clean-up of the CO 2 gas-based fluid after hydraulic fracturing is more convenient compared to slick-water and polymer-based fluids …”

Section: Introductionmentioning

confidence: 99%

Experimental Assessment of Fracture Initiation and Wettability in Low and High Brittle Shales by CO₂ Foam Fracturing Fluids

et al. 2022

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CO2 foam fracturing fluid has received significant attention because of its versatility in water-sensitive formations. However, the mechanisms of hydraulic fracturing of shale reservoirs by CO2 foam fracking fluid, in terms of fracture initiation and propagation remain unclear. In this paper, an experimental study was conducted to correlate the fluid interaction and fracture propagation in various shale formations having brittleness indices of 0.43, 0.50, and 0.74 to the rock-fracking fluid wettability. The shale wetting state in the presence of the CO2 foam fracturing fluid was determined from contact angle measurements through the Krüss drop shape analyzer (DSA 100), and the hydraulic fracturing was conducted via a tri-axial fracking system. A specific concentration of polyacrylamide (500 ppm) is used as a drag-reducing agent and selected for the hydraulic fracturing experiments. CO2 foam fracturing resulted in low fracture initiation pressure in the shale, having a high brittleness index of 0.74 BIm, and it remains the same at high temperatures. The length and aperture of the hydraulic fracture were then correlated with fracturing fluid–shale contact angles. The Mancos shale is sand-rich (with 21 wt % calcite and 52 wt % quartz), and it remained strongly water-wet on the interaction with the fracking fluid, and the net breakdown pressure was found to be lower in the fracturing tests of the Mancos shale. The Marcellus shale (with 31 wt % calcite and 22 wt % quartz) was intermediately wet (with a contact angle of 93.1°), whereas the Eagle Ford shale with high clay content (77 wt % calcite and 11 wt % quartz) was CO2-wet (with a contact angle of 109°) at 80 °C. Marcellus and Eagle Ford shales demonstrated higher fracture initiation pressures during the fracking experiments than the Mancos shale. The study suggests that fracking fluid–shale wettability has an essential role in the fracking of shale formations and should be considered in optimizing hydraulic fracturing fluid.

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Surface Phenomena in the Deformation and Fracture of Metals

Cited by 11 publications

References 0 publications

Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Two methods of investigation of the influence of hydrogen on the propagation rate of a crack and behavior of fracture of high-strength steels

Experimental Assessment of Fracture Initiation and Wettability in Low and High Brittle Shales by CO₂ Foam Fracturing Fluids

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Surface Phenomena in the Deformation and Fracture of Metals

Cited by 11 publications

References 0 publications

Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Inter-Granular Phase Formation during Reactive Diffusion of Gallium with Al Alloy

Two methods of investigation of the influence of hydrogen on the propagation rate of a crack and behavior of fracture of high-strength steels

Experimental Assessment of Fracture Initiation and Wettability in Low and High Brittle Shales by CO2 Foam Fracturing Fluids

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Product

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Experimental Assessment of Fracture Initiation and Wettability in Low and High Brittle Shales by CO₂ Foam Fracturing Fluids