44 research outputs found
Energy dissipation and storage in iron under plastic deformation (experimental study and numerical simulation)
The work is devoted to the experimental and numerical investigation of thermodynamic aspects ofthe plastic deformation in Armco iron. Dissipation and stored energies was calculated from processedexperimental data of the surface temperature obtained by infrared thermography. An original mathematicalmodel describing the process of mesoscopic defects accumulation was used for numerical simulation of thequasistatic loading of iron samples and for calculation of theoretical value of the stored energy. Experimentaland modeled values of the stored energy are in a good agreement
The study of a defect evolution in iron under fatigue loading in gigacyclic fatigue regime
The work is devoted to the study of the damage accumulation in iron under gigacyclic fatigue (VHCF) regime. The study of the mechanical properties of the samples with different state of life time existing was carried out on the base of the acoustic resonance method. The damage accumulation (porosity of the samples) was studied by the hydrostatic weighing method. The obtained results show the accumulation of porosity in the volume of the sample during fatigue loading and corresponding decrease of the elastic properties. A statistical model of damage accumulation was proposed in order to describe the damage accumulation process. The model describes the influence of the sample surface on the location of fatigue crack initiatio
Theoretical and Experimental Investigation of the Dissipated and Stored Energy Ratio in Iron under Quasi-Static and Cyclic Loading
The problem of energy storing (cold work accumulation) in metals was intensively investigated both theoretically and experimentally during all last century but a general theoretical conception of the process was not created. This work is devoted to an experimental investigation of energy dissipation in metals under plastic deformation and to the development of a thermodynamic model to study the cold work accumulation under plastic deformation and failure. The proposed model is based on a statistical description of collective properties of mesoscopic defects and on dividing the plastic deformation into two parts (dissipative and structural). The structural plastic strain was considered as an independent thermodynamic variable that allowed us to determine the thermodynamic potential of the system. The derived constitutive relations were applied for numerical simulation of tensile and cyclic tests. The numerical results demonstrate a good agreement with experimental data.ΠΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΎ ΡΠ°ΡΡΠ΅ΡΠ½ΠΈΠ΅ ΡΠ½Π΅ΡΠ³ΠΈΠΈ Π² ΠΌΠ΅ΡΠ°Π»Π»Π°Ρ
ΠΏΡΠΈ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ Π΄Π΅ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠΈ ΠΈ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠ΅ ΡΠ΅ΡΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΒΡΠ΅ΡΠΊΠΎΠΉ ΠΌΠΎΠ΄Π΅Π»ΠΈ Π΄Π»Ρ ΠΈΠ·ΡΡΠ΅Π½ΠΈΡ Π½Π°ΠΊΠΎΠΏΠ»Π΅Π½ΠΈΡ Π½Π°ΠΊΠ»Π΅ΠΏΠ° ΠΏΡΠΈ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ Π΄Π΅ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠΈ ΠΈ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΠΈ. ΠΡΠ΅Π΄Π»Π°Π³Π°Π΅ΠΌΠ°Ρ ΠΌΠΎΠ΄Π΅Π»Ρ ΠΎΡΠ½ΠΎΒΠ²Π°Π½Π° Π½Π° ΡΡΠ°ΡΠΈΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ ΠΎΠΏΠΈΡΠ°Π½ΠΈΠΈ ΠΊΠΎΠ»Π»Π΅ΠΊΒΡΠΈΠ²Π½ΡΡ
ΡΠ²ΠΎΠΉΡΡΠ² ΠΌΠ΅Π·ΠΎΡΠΊΠΎΠΏΠΈΡΠ΅ΡΠΊΠΈΡ
Π΄Π΅ΡΠ΅ΠΊΡΠΎΠ² ΠΈ Π½Π° ΡΠ°Π·Π΄Π΅Π»Π΅Π½ΠΈΠΈ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΉ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ Π½Π° Π΄Π²Π΅ ΡΠ°ΡΡΠΈ (Π΄ΠΈΡΡΠΈΠΏΠ°ΡΠΈΠ²Π½ΡΡ ΠΈ ΠΎΠ±ΡΡΡ). ΠΠ±ΡΠ°Ρ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠ°Ρ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΡ ΡΠ°ΡΡΠΌΠ°ΡΒΡΠΈΠ²Π°Π»Π°ΡΡ ΠΊΠ°ΠΊ Π½Π΅Π·Π°Π²ΠΈΡΠΈΠΌΠ°Ρ ΡΠ΅ΡΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΏΠ΅ΡΠ΅ΠΌΠ΅Π½Π½Π°Ρ, ΡΡΠΎ ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΠ»ΠΎ ΠΎΠΏΡΠ΅Π΄Π΅ΒΠ»ΠΈΡΡ ΡΠ΅ΡΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΏΠΎΡΠ΅Π½ΡΠΈΠ°Π» ΡΠΈΡΡΠ΅ΒΠΌΡ. ΠΠΎΠ»ΡΡΠ΅Π½Π½ΡΠ΅ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΡΡΠΈΠ΅ ΡΠΎΠΎΡΠ½ΠΎΡΠ΅ΒΠ½ΠΈΡ ΠΏΡΠΈΠΌΠ΅Π½ΠΈΠ»ΠΈ Π΄Π»Ρ ΡΠΈΡΠ»Π΅Π½Π½ΠΎΠ³ΠΎ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΒΠ²Π°Π½ΠΈΡ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠΎΠ² ΠΈΡΠΏΡΡΠ°Π½ΠΈΠΉ Π½Π° ΡΠ°ΡΡΡΠΆΠ΅Π½ΠΈΠ΅ ΠΈ ΡΠΈΠΊΠ»ΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΈΡΠΏΡΡΠ°Π½ΠΈΠΉ. Π§ΠΈΡΠ»Π΅Π½Π½ΡΠ΅ ΡΠ΅ΒΠ·ΡΠ»ΡΡΠ°ΡΡ Ρ
ΠΎΡΠΎΡΠΎ ΡΠΎΠ³Π»Π°ΡΡΡΡΡΡ Ρ ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΒΡΠ°Π»ΡΠ½ΡΠΌΠΈ Π΄Π°Π½Π½ΡΠΌΠΈ
Theoretical and Experimental Investigation of the Dissipated and Stored Energy Ratio in Iron under Quasi-Static and Cyclic Loading
The problem of energy storing (cold work accumulation) in metals was intensively investigated both theoretically and experimentally during all last century but a general theoretical conception of the process was not created. This work is devoted to an experimental investigation of energy dissipation in metals under plastic deformation and to the development of a thermodynamic model to study the cold work accumulation under plastic deformation and failure. The proposed model is based on a statistical description of collective properties of mesoscopic defects and on dividing the plastic deformation into two parts (dissipative and structural). The structural plastic strain was considered as an independent thermodynamic variable that allowed us to determine the thermodynamic potential of the system. The derived constitutive relations were applied for numerical simulation of tensile and cyclic tests. The numerical results demonstrate a good agreement with experimental data.ΠΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΎ ΡΠ°ΡΡΠ΅ΡΠ½ΠΈΠ΅ ΡΠ½Π΅ΡΠ³ΠΈΠΈ Π² ΠΌΠ΅ΡΠ°Π»Π»Π°Ρ
ΠΏΡΠΈ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ Π΄Π΅ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠΈ ΠΈ ΡΠ°Π·ΡΠ°Π±ΠΎΡΠΊΠ΅ ΡΠ΅ΡΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΒΡΠ΅ΡΠΊΠΎΠΉ ΠΌΠΎΠ΄Π΅Π»ΠΈ Π΄Π»Ρ ΠΈΠ·ΡΡΠ΅Π½ΠΈΡ Π½Π°ΠΊΠΎΠΏΠ»Π΅Π½ΠΈΡ Π½Π°ΠΊΠ»Π΅ΠΏΠ° ΠΏΡΠΈ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ Π΄Π΅ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠΈ ΠΈ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΠΈ. ΠΡΠ΅Π΄Π»Π°Π³Π°Π΅ΠΌΠ°Ρ ΠΌΠΎΠ΄Π΅Π»Ρ ΠΎΡΠ½ΠΎΒΠ²Π°Π½Π° Π½Π° ΡΡΠ°ΡΠΈΡΡΠΈΡΠ΅ΡΠΊΠΎΠΌ ΠΎΠΏΠΈΡΠ°Π½ΠΈΠΈ ΠΊΠΎΠ»Π»Π΅ΠΊΒΡΠΈΠ²Π½ΡΡ
ΡΠ²ΠΎΠΉΡΡΠ² ΠΌΠ΅Π·ΠΎΡΠΊΠΎΠΏΠΈΡΠ΅ΡΠΊΠΈΡ
Π΄Π΅ΡΠ΅ΠΊΡΠΎΠ² ΠΈ Π½Π° ΡΠ°Π·Π΄Π΅Π»Π΅Π½ΠΈΠΈ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΎΠΉ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ Π½Π° Π΄Π²Π΅ ΡΠ°ΡΡΠΈ (Π΄ΠΈΡΡΠΈΠΏΠ°ΡΠΈΠ²Π½ΡΡ ΠΈ ΠΎΠ±ΡΡΡ). ΠΠ±ΡΠ°Ρ ΠΏΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠ°Ρ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΡ ΡΠ°ΡΡΠΌΠ°ΡΒΡΠΈΠ²Π°Π»Π°ΡΡ ΠΊΠ°ΠΊ Π½Π΅Π·Π°Π²ΠΈΡΠΈΠΌΠ°Ρ ΡΠ΅ΡΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΏΠ΅ΡΠ΅ΠΌΠ΅Π½Π½Π°Ρ, ΡΡΠΎ ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΠ»ΠΎ ΠΎΠΏΡΠ΅Π΄Π΅ΒΠ»ΠΈΡΡ ΡΠ΅ΡΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΏΠΎΡΠ΅Π½ΡΠΈΠ°Π» ΡΠΈΡΡΠ΅ΒΠΌΡ. ΠΠΎΠ»ΡΡΠ΅Π½Π½ΡΠ΅ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΡΡΠΈΠ΅ ΡΠΎΠΎΡΠ½ΠΎΡΠ΅ΒΠ½ΠΈΡ ΠΏΡΠΈΠΌΠ΅Π½ΠΈΠ»ΠΈ Π΄Π»Ρ ΡΠΈΡΠ»Π΅Π½Π½ΠΎΠ³ΠΎ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΒΠ²Π°Π½ΠΈΡ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠΎΠ² ΠΈΡΠΏΡΡΠ°Π½ΠΈΠΉ Π½Π° ΡΠ°ΡΡΡΠΆΠ΅Π½ΠΈΠ΅ ΠΈ ΡΠΈΠΊΠ»ΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΈΡΠΏΡΡΠ°Π½ΠΈΠΉ. Π§ΠΈΡΠ»Π΅Π½Π½ΡΠ΅ ΡΠ΅ΒΠ·ΡΠ»ΡΡΠ°ΡΡ Ρ
ΠΎΡΠΎΡΠΎ ΡΠΎΠ³Π»Π°ΡΡΡΡΡΡ Ρ ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΒΡΠ°Π»ΡΠ½ΡΠΌΠΈ Π΄Π°Π½Π½ΡΠΌΠΈ
Theoretical Approach for Developing the Thermographic Method in Ultrasonic Fatigue
AbstractIn the last years, several approaches were developed in literature for predicting the fatigue strength of different kinds of materials. One approach is the Thermographic Method, based on the thermographic technique. This study is devoted to the development of a theoretical approach for modeling of surface and undersurface fatigue crack initiation and temperature evolution during ultrasonic fatigue test. The proposed model is based on the statistical description of mesodefect ensemble and describes an energy balance in materials (including power of energy dissipation) under cyclic loading. The model allows us to simulate the damage to fracture transition and corresponding temperature evolution in critical cross section of a sample tested in very high cyclic fatigue regime
Energy dissipation and storage in iron under plastic deformation (experimental study and numerical simulation)
The work is devoted to the experimental and numerical investigation of thermodynamic aspects of the plastic deformation in Armco iron. Dissipation and stored energies was calculated from processed experimental data of the surface temperature obtained by infrared thermography. An original mathematical model describing the process of mesoscopic defects accumulation was used for numerical simulation of the quasistatic loading of iron samples and for calculation of theoretical value of the stored energy. Experimental and modeled values of the stored energy are in a good agreement
Collective Modes in the Microshear Ensemble as a Mechanism of the Failure Wave
Results of theoretical and experimental study of failure wave phenomena are presented. A description ofthefailure wavephenomenon wasproposed in terms ofa self-similar solutionfor the microshear density. The mechanisms offailure wave generation andpropagation were classified as a delayedfailure with the delay time corresponding to the time ofexcitation ofself-similar blow-up collective modes in a microshear ensemble. Experimental study of the mechanism of the failure wave generation andpropagation was carried out using afused quartz rod and included the Taylor test with high-speed framing. The results obtained confirmed the "delayedβ mechanism of the failure wave generation and propagation.ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΡΠ΅ΠΎΡΠ΅ΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΈ ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΡΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ ΡΠ²Π»Π΅Π½ΠΈΡ Π²ΠΎΠ»Π½Ρ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΡ. ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ΠΎ ΠΎΠΏΠΈΡΠ°Π½ΠΈΠ΅ ΡΠ²Π»Π΅Π½ΠΈΡ Π²ΠΎΠ»Π½Ρ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΡ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ Π°Π²ΡΠΎΒΠΌΠΎΠ΄Π΅Π»ΡΠ½ΠΎΠ³ΠΎ ΡΠ΅ΡΠ΅Π½ΠΈΡ Π΄Π»Ρ ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΠΈ ΠΌΠΈΠΊΡΠΎΒΡΠ΄Π²ΠΈΠ³ΠΎΠ². ΠΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΡ Π²ΠΎΠ·Π½ΠΈΠΊΠ½ΠΎΠ²Π΅Π½ΠΈΡ ΠΈ ΡΠ°ΡΒΠΏΡΠΎΡΡΡΠ°Π½Π΅Π½ΠΈΡ Π²ΠΎΠ»Π½Ρ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΡ ΠΊΠ»Π°ΡΡΠΈΡΠΈΒΡΠΈΡΠΎΠ²Π°Π»ΠΈ ΠΊΠ°ΠΊ Π·Π°ΠΌΠ΅Π΄Π»Π΅Π½Π½ΠΎΠ΅ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΠ΅, ΠΏΡΠΈΒ ΡΠ΅ΠΌ Π²ΡΠ΅ΠΌΡ Π·Π°Π΄Π΅ΡΠΆΠΊΠΈ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΎΠ²Π°Π»ΠΎ Π²ΡΠ΅ΠΌΠ΅Π½ΠΈ Π²ΠΎΠ·Π±ΡΠΆΠ΄Π΅Π½ΠΈΡ Π°Π²ΡΠΎΠΌΠΎΠ΄Π΅Π»ΡΠ½ΡΡ
Π²Π·ΡΡΠ²Π½ΡΡ
ΠΊΠΎΠ»Π»Π΅ΠΊΡΠΈΠ²Π½ΡΡ
ΠΊΠΎΠ»Π΅Π±Π°Π½ΠΈΠΉ Π²ΠΎ ΠΌΠ½ΠΎΠΆΠ΅ΡΡΠ²Π΅ ΠΌΠΈΠΊΡΠΎΡΠ΄Π²ΠΈΠ³ΠΎΠ². ΠΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΠΎΠ΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΒΠ²Π°Π½ΠΈΠ΅ ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΠ° Π²ΠΎΠ·Π½ΠΈΠΊΠ½ΠΎΠ²Π΅Π½ΠΈΡ ΠΈ ΡΠ°ΡΠΏΡΠΎΒΡΡΡΠ°Π½Π΅Π½ΠΈΡ Π²ΠΎΠ»Π½Ρ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΡ ΠΏΡΠΎΠ²ΠΎΠ΄ΠΈΠ»ΠΎΡΡ Ρ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ ΡΠ°ΡΠΏΠ»Π°Π²Π»Π΅Π½Π½ΠΎΠ³ΠΎ ΠΊΠ²Π°ΡΡΠ΅Π²ΠΎΠ³ΠΎ ΡΡΠ΅ΡΠΆΠ½Ρ ΠΈ Π²ΠΊΠ»ΡΡΠ°Π»ΠΎ ΠΈΡΠΏΡΡΠ°Π½ΠΈΠ΅ ΠΏΠΎ ΠΌΠ΅ΡΠΎΠ΄Ρ Π’Π΅ΠΉΠ»ΠΎΡΠ° Ρ Π²ΡΡΠΎΠΊΠΎΡΠΊΠΎΡΠΎΡΡΠ½ΡΠΌ ΡΠΎΡΠΎΠ³ΡΠ°ΡΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ. ΠΠΎΠ»ΡΡΠ΅Π½Π½ΡΠ΅ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΏΠΎΠ΄ΡΠ²Π΅ΡΠ΄ΠΈΒ Π»ΠΈ βΠ·Π°ΠΌΠ΅Π΄Π»Π΅Π½Π½ΡΠΉβ ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌ Π²ΠΎΠ·Π½ΠΈΠΊΠ½ΠΎΠ²Π΅Π½ΠΈΡ ΠΈ ΡΠ°ΡΠΏΡΠΎΡΡΡΠ°Π½Π΅Π½ΠΈΡ Π²ΠΎΠ»Π½Ρ ΡΠ°Π·ΡΡΡΠ΅Π½ΠΈΡ
Combined lock-in thermography and heat flow measurements for analysing heat dissipation during fatigue crack propagation
During fatigue crack propagation experiments with constant force as well as constant stress intensity lock in thermography and heat flow measurements with a new developed peltier sensor have been performed. With lock in thermography space resolved measurements are possible and the evaluation allows to distinguish between elastic and dissipated energies. The specimens have to be coated with black paint to enhance the emissivity. The thickness of the coating influences the results and therefore quantitative measurements are problematic. The heat flow measurements are easy to perform and provide quantitative results but only integral in an area given by the used peltier element. To get comparable results the values measured with thermography were summarized in an area equivalent to that of the peltier element. The experiments with constant force show a good agreement between the thermography and the heat flow measurements. In case of the experiments with a constant stress intensity some differences become visible. Whereas the thermography measurements show a linear decrease of the signal with rising crack length, the heat flow measurements show a clearly nonlinear dependency. Obviously the measured energies in thermography and peltier based heat flow measurement are not comparable
MODEL OF GEOMEDIA CONTAINING DEFECTS: COLLECTIVE EFFECTS OF DEFECTS EVOLUTION DURING FORMATION OF POTENTIAL EARTHQUAKE FOCI
This paper describes the statistical thermo-dynamical evolution of an ensemble of defects in the geomedium in the field of externally applied stresses. The authors introduce βtensor structuralβ variables associated with two specific types of defects, fractures and localized shear faults (Fig. 1). Based on the procedure for averaging of the structural variables by statistical ensembles of defects, a self-consistency equation is developed; it determines the dependence of the macroscopic tensor of defects-induced strain on values of external stresses, the original pattern and interaction of defects. In the dimensionless case, the equation contains only the parameter of structural scaling, i.e. the ratio of specific structural scales, including the size of defects and an average distance between the defects.The self-consistency equation yields three typical responds of the geomedium containing defects to the increasing external stress (Fig. 2). The responses are determined from values of the structural scaling parameter. The concept of non-equilibrium free energy for a medium containing defects, given similar to the Ginzburg-Landau decomposition, allowed to construct evolutionary equations for the introduced parameters of order (deformation due to defects, and the structural scaling parameter) and to explore their solutions (Fig. 3).It is shown that the first response corresponds to stable quasi-plastic deformation of the geomedium, which occurs in regularly located areas characterized by the absence of collective orientation effects. Reducing the structural scaling parameter leads to the second response characterized by the occurrence of an area of meta-stability in the behavior of the medium containing defects, when, at a certain critical stress, the orientation transition takes place in the ensemble of interacting defects, which is accompanied by an abrupt increase of deformation (Fig. 2). Under the given observation/averaging scale, this transition is manifested by localized cataclastic deformation (i.e. a set of weak earthquakes), which migrates in space at a velocity several orders of magnitude lower than the speed of sound, as a βslowβ deformation wave (Fig. 3). Further reduction of the structural scaling parameter leads to degeneracy of the orientation meta-stability and formation of localized dissipative defect structures in the medium. Once the critical stress is reached, such structures develop in the blow-up regime, i.e. the mode of avalanche-unstable growth of defects in the localized area that is shrinking eventually. At the scale of observation, this process is manifested as brittle fracturing that causes formation of a deformation zone, which size is proportional to the scale of observation, and corresponds to occurrence of a strong earthquake.On the basis of the proposed model showing the behavior of the geomedium containing defects in the field of external stresses, it is possible to describe main ways of stress relaxation in the rock massives β brittle large-scale destruction and cataclastic deformation as consequences of the collective behavior of defects, which is determined by the structural scaling parameter.Results of this study may prove useful for estimation of critical stresses and assessment of the geomedium status in seismically active regions and be viewed as model representations of the physical hypothesis about the uniform nature of deveΒlopment of discontinuities/defects in a wide range of spatial scales
Experimental study of heat dissipation at the crack tip during fatigue crack propagation
This work is devoted to the development of an experimental method for studying the energy balance during cyclic deformation and fracture. The studies were conducted on 304 stainless steel AISE and titanium alloy OT4-0 samples. The investigation of the fatigue crack propagation was carried out on flat samples with different geometries and types of stress concentrators. The heat flux sensor was developed based on the Seebeck effect. This sensor was used for measuring the heat dissipation power in the examined samples during the fatigue tests. The measurements showed that the rate of fatigue crack growth depends on the heat flux at the crack tip