Parameters Of Stress-strain State Research Articles

Investigation of the Efficiency of Roll Profiles and Technological Schemes of Deformation of Asymmetric Rolling in Relief Rolls of C11000 Copper Alloy by FEM Simulation

In this paper, finite element simulation of asymmetric rolling in relief rolls of C11000 copper alloy in order to analyze the effectiveness of possible roll profiles and technological schemes of deformation was performed. The scientific innovation of this work lies in determining the patterns of development of stress-strain state parameters for various configurations of rolls, as well as determining the effectiveness of metal processing using various technological schemes. It was found that the use of trapezoidal relief makes it possible to increase the level of metal processing by almost 5 times compared with the use of radial relief. Comparison of technological schemes of deformation showed that deformation with 180° workpiece turning between passes significantly reduces the influence of the asymmetry factor. Deformation without changing the workpiece position between the passes has the opposite effect, and such a scheme significantly increases the influence of the asymmetry factor. Deformation with a transverse workpiece shift for the relief period between passes has the effect of a “golden mean.” The conducted laboratory experiment for lead billet showed that the shape change of lead billet during computer simulation has a high level of convergence with real conditions. At each stage of deformation, the difference in the geometric parameters of the workpiece between the model and the experiment did not exceed 3-5%. When deforming a copper billet, the maximum difference level was 8%, which is the result of the low rigidity of the rolling cage with smooth rolls.

Nonlinear Deformation of Cylinders from Materials with Different Behavior in Tension and Compression

A new numerical-analytical method for solving physically nonlinear deformation problems of axisymmetrically loaded cylinders made of materials with different behavior in tension and compression has been developed. To linearize the problem, the uninterrupted parameter continuation method was used. For the variational formulation of the linearized problem, a functional in the Lagrange form, defined on the kinematically possible displacement rates, is constructed. To find the main unknowns of the problem of physically nonlinear cylinder deformation, the Cauchy problem for the system of ordinary differential equations is formulated. The Cauchy problem was solved by the Runge-Kutta-Merson method with automatic step selection. The initial conditions were established by solving the problem of linear elastic deformation. The right-hand sides of the differential equations at fixed values of the load parameter corresponding to the Runge-Kutta-Merson’s scheme are found from the solution of the variational problem for the functional in the Lagrange form. Variational problems are solved using the Ritz method. The test problem for the nonlinear elastic deformation of a thin cylindrical shell is solved. Coincidence of the spatial solution with the shell solution was obtained. Physically nonlinear deformation of a thick-walled cylinder was studied. It is shown that failure to take into account the different behavior of the material under tension and compression leads to significant errors in the calculations of stress-strain state parameters.

Assessing a natural field of rock mass stress by means of in-situ measurements within Vostochnaya Sary-Oba deposit in Kazakhstan

Purpose is to assess a natural field of rock mass stress within Vostochnaya Sary-Oba deposit using in-situ measurements. It will help identify stress distribution as well as high-stress areas that may be dangerous for mining operations. Methods. The research has applied a technique of well hydraulic fracturing to study parameters of the initial stress field within the deposit. For the purpose, two metering points in two measuring (horizontal and vertical) wells were used. Hydraulic fracturing has been tested at each installation location. Findings. The in-situ measurement results have helped obtain quantitative parameters of stress-strain state of the rock mass. It has been understood that the available tectonic disturbances may result from the shape of structural folds as well as from tectonic fissility. Operating azimuth of the maximum horizontal stress within the points coincides, it is equal to 70° ± 10. Originality is the use of a new approach to assess the stress rock mass state within Vostochnaya Sary-Oba deposit while applying in-situ measurements and well hydraulic fracturing. The abovementioned favours more accurate and reliable assessment of rock stress state at the field being quite important for mining safety and for the development of the efficient supporting procedures and ore extraction procedures. Practical implications. The research results are applicable to adapt project documents for the deposit mining, a supporting technique selection, and ore extracting. Moreover, they will help make the substantiated choice of a structure and geotechnical parameters taking into consideration safety of operations as well as quality of ore mining. In addition, the results help develop measures to prevent rock mass outburst and fall in mine workings.

Моделирование процесса прокатки слоистого композита АМг3/Д16/АМг3

Introduction. Over the past decades, laminated composites based on aluminum alloys have been increasingly used in the aerospace and automotive industries. Laminated composites are usually produced by accumulative roll bonding, which results in the metallurgical bonding of initially prepared sheets. Hence, the main task of accumulative roll bonding is to obtain a reliable bond between materials. However, at present, the process of joining similar or dissimilar materials by plastic deformation is still a poorly understood phenomenon. In this regard, in recent years, methods of finite element modeling of the processes of joining materials have begun to develop intensively. The purpose of the work is to establish a relationship between stress-strain state parameters and the formation of a stable bond between aluminum alloys of different compositions. To achieve this goal, the following tasks are formulated: 1. Simulation of the laminated composite “AMg3/D16/AMg3” rolling process using data corresponding to physical experiments carried out at the Institute of Engineering Science of the Ural Branch of the Russian Academy of Sciences; 2. Selection and analysis of the most important stress-strain state parameters of the laminated composite “AMg3/D16/AMg3” rolling process. Research methods. Process simulation system Deform-3D was chosen as the main research tool. Results and Discussion. An analysis of the coordinate grid distortion and velocity vectors of material flow of layers revealed that the deformation is distributed inhomogeneously in the cross section after rolling: the outer layers flow more intensively compared to the middle layer. The maximum scatter of strain intensity ei in the cross section, observed at a maximum reduction ratio of 75%, is 12%. This allows one to accept for analytical calculations in the first approximation the assumption of deformation uniformity. A relationship is established between the beginning of the formation of a bond between composite layers and the threshold expansion of the contact surface and normal pressure at the interlayer boundary. In the final part of the study, future directions for improving the approaches of simulation the laminated composites rolling processes are proposed.

Bending of Plates with Complex Shape Made from Materials that Differently Resist to Tension and Compression

A new numerical-analytical method for solving physically nonlinear bending problems of thin plates with complex shape made from materials that differently resist to tension and compression is developed. The uninterrupted parameter continuation method is used to formulate and linearize the problem of physically nonlinear bending. For the linearized problem, a functional in the Lagrange form, given on the kinematically possible displacement rates, is constructed. The main unknown problems (displacements, strains, stresses) were found from the solution of the initial problem, which was solved by the Runge-Kutta-Merson method with automatic step selection, by the parameter related to the load. The initial conditions are found from the solution of the problem of linear elastic deformation. The right-hand sides of the differential equations at fixed values of the load parameter corresponding to the Runge-Kutta-Merson scheme are found from the solution of the variational problem for the functional in the Lagrange form. Variational problems are solved using the Ritz method in combination with the R-function method, which allows to submit an approximate solution in the form of a formula – a solution structure that exactly satisfies the boundary conditions and is invariant with respect to the shape of the domain where the approximate solution is sought. The test problem for the nonlinear elastic bending of a square hinged plate is solved. Satisfactory agreement with the three-dimensional solution is obtained. The bending problem of the plate of complex shape with combined fixation conditions is solved. The influence of the geometric shape and fixation conditions on the stress-strain state is studied. It is shown that failure to take into account the different behavior of the material under tensile and compression can lead to significant errors in the calculations of the stress-strain state parameters.

CALCULATION OF GAS-DYNAMICS PARAMETERS AND STRESS-STRAIN STATE OF CELSIAN CERAMICS PRODUCTS

In the work using the finite element method, an analysis of the behavior of nose fairings made of radio-transparent ceramic materials of celsian composition was carried out. Determination of parameters of gas dynamics and stress-strain state was carried out using licensed ANSYS software. SSG Reynold Stress turbulence model was chosen for accurate air flow simulation. Geometric and finite element models were used to calculate strength and temperature fields. The analysis of the results of gas-dynamic calculations shows that at the point of transition of the conical part of the rocket into the cylindrical part, there is a sharp change in the flow conditions and a disruption of the flow in the range of speeds of 100-1100 m/s. As a result of modeling the distribution of temperature fields with the stated task, it was established that the temperature on the inner surface of the fairing differs from the temperature on the outer surface by no more than ±1 °C on average, and the maximum surface heating temperature does not exceed 550 °C. According to the results of calculations of the stress-strain state under temperature regimes that simulate the conditions of their operation, it was concluded that under the considered conditions the equivalent (≤ 69.3 MPa) and main (≤ 40 MPa) stresses occurring in the nose fairing are not exceed the bending strength limit for celsian ceramics (290 MPa). It can be observed that the maximum temperature difference in thickness corresponds to the part of the fairing with the minimum radius. Movements on the surface of the fairing do not exceed 0.25 mm, which is acceptable according to the specified parameters. The parametric model provides advantages in justifying rational technical solutions. Ultimately, the nose fairing, made of celsian ceramics, will maintain its integrity in real operating conditions. Keywords: radiotransparent celsian ceramics; nose fairing; finite element method; gas dynamics; thermophysical calculations; strength; stress-strain state

Investigation of a stress-strain state of a rubber-cable rope with cables of different tensile rigidity

Purpose. Establishment of dependences for stress-strain state parameters in a rubber-cable rope with cables of different tensile rigidity and cable breakage. Research methodology. Construction and development of an algorithm for solving a model of a stress-strain state of a rubber-cable rope with ropes of different tensile rigidity and breakage of one cable by using the methods of mechanics of layered composite materials with soft and hard layers. Findings. Analytical expressions are constructed, which allow determining the main stress-strain state indicators in a rope with an odd number of cables, while the middle cable is damaged, and tensile rigidity of the middle cable is half the tensile rigidity of the other cables. Analytical dependencies are established for determining the extreme angles of rubber shear between the cables, what allows determining the most dangerous tension states of a rope with a damaged cable, which has a different rigidity from the other cables. The level of reliability of the developed algorithm for solving the model of a stress-strain state of a rubber-cable rope with cables of different rigidity is confirmed by determining the maximum tensile forces of a rope made of three cables, in which the middle cable has a tensile rigidity half that of the other two. The force distribution coefficients between cables adjacent to the damaged one are equal to 1.25 per unit load on each cable, which corresponds to the only possible case of force distribution between parallel elements under the presented conditions. Scientific novelty. The character of influence of different rigidity and damage of the reinforcing cables on the main parameters of stress-strain state in a rubber-cable rope are established. Practical significance. An algorithm for determining the stress-strain state indicators of a rubber-cable rope, which has an odd number of reinforcing cables, its middle cable is damaged, and the tensile rigidity of the middle cable is different (lower) than the rigidity of the other cables, is developed. This makes it possible to increase the operational safety of rubber-cable ropes in hoisting and transporting machines, in particular when operating at significant lifting heights, and also contributes to justifying the use of a rope design as a stay rope in capital structures.

Plasticity Resource of Cast Iron at Deforming Broaching

The contact interaction mechanics of deformation broaching in low-plasticity materials is studied. Particular attention is paid to the study of the stress–strain state parameters and the plasticity margin in the deformation zone during the machining of gray cast iron EN-GJL-200. The stress–strain state was analyzed using a finite-element model of the deforming broaching process for each area of the deformation zone. The model parameters of the machined material were determined experimentally by compressing specimens of gray cast iron EN-GJL-200. The changes in the parameters of accumulated strain, stress tensor components, stress triaxiality ratio, hydrostatic stress, and plasticity margin at different deformation zones along the machined specimen depth are analyzed. It is shown that there is a zone of local plastic deformation in conditions of critical contact stresses. This leads to the appearance of tensile stresses that reduce the plasticity margin in the surface layer. The impact of tool geometry on the stress–strain state of the surface layer is also discussed, and recommendations for the optimal working angle of the deforming element are provided based on plasticity margin minimization.

Longitudinal wave propagation in an extended cylindrical body with external Coulomb friction

The propagation of elastic longitudinal waves in an extended cylindrical body located inside an unstrained body and interacting according to the Coulomb law is considered in the article. The problem is studied in a two-dimensional statement; therefore, the friction force (i.e., the interaction conditions) is included in the system of equations as a boundary condition. The Coulomb friction force arises due to the deformation of a cylindrical body. The reliability of numerical calculations is substantiated by solving test cases and comparing the calculations with experimental results. The numerical results obtained are presented in the form of graphs and analyzed. It is shown that the parameters (stresses and strains) of waves propagating in an elastic cylindrical body with external Coulomb dry friction decay with distance. The mechanism for reducing the stress-strain state and wave parameters is explained by the consumption of elastic energy to overcome the friction force that occurs on the contact surface. The results of the two-dimensional problem are also compared with the results of a similar problem in the one-dimensional theory, where the friction force enters directly into the equations of motion. The deviations of the results of the one-dimensional theory are up to 8-15% depending on the accepted values of the friction coefficient, i.e. the violation of the plane section hypothesis taken in one-dimensional calculations amounts to 15%. With a decrease in the radius of a cylindrical body, these deviations are reduced.

Engineering methodology for calculation of corrugated beams for bending and torsion. Flat bend form stability

An engineering design procedure for calculating bending with torsion in corrugated beams, including finding the critical load of general stability, implemented in the commonly used MS Excel spreadsheet and verified in the LIRA-SAPR software package, has been proposed. The method makes it possible to take into account the beams section variability and corrugation parameters, to estimate the loading eccentricity effect, availability of supporting ribs and reinforcements of the compressed chord from the bending plane. Calculation results of particular design solutions for corrugated beams with definition of critical loads at transverse bending are given. Results of test calculation of a bent channel beam with calculation of stress-strain state parameters and its verification with the LIRA-SAP software package are given.

Interaction of Stress-Strain State of the Reinforced Soil Mass and Vertical Shaft Mouth Lining with the Mine Surface Building’s Foundations

Introduction. The mining of mineral deposits is related to the construction of sophisticated technological complexes on the surface being a liaison between underground operations and above-ground systems. During construction of the mining companies’ buildings and structures of the above-ground technological complexes there arise problems related to the complicated engineering, geological and hydrogeological conditions, as well as emerge difficulties caused by the presence of underground workings (mining, transport, ventilation, auxiliary) affecting the construction and operation of surface facilities. In this article a study was made of the stress-strain state (SSS) of a complex system comprising a mine surface building, a vertical shaft mouth with a ventilation duct under conditions complicated by the presence of subsiding soils and the need of reinforcement thereof.Materials and methods. In the study there were used: the analysis of existing methods of soil bases reinforcement as applied to the specific engineering and geological conditions of construction, subject to the interdependence of aboveground and underground structures; the mathematical modeling of the system "a vertical shaft mouth with a ventilation duct - a subsiding soil mass reinforced with soil piles - a mine surface building’s foundations"; the study of SSS features on models, determination of the main factors affecting the design decisions on enforcement of soil bases and building foundations receiving a compound combination of operational loads.Results. It has been found that the above-ground loadbearing structures, foundations and soil bases should be calculated taking into account the interdependence with the vertical shaft and the adjacent ventilation duct, based on the SSS parameters definition. The monolithic concrete mouth lining has a significant impact on the SSS of the foundation slab, increasing rigidity at the points of contact between the slab and the lining. The minimum vertical settlement of the slab is observed above the shaft mouth lining, the maximum - in the central part of the building, in the points of maximum load application.Discussion and Conclusions. The results of the stress-strain state study of a reinforced soil mass and a vertical shaft mouth lining in interaction with the mine surface building’s foundations are formulated, and recommendations are given on considering the affecting factors when designing such facilities.

EFFECTIVENESS OF STRENGTHENING OF REINFORCED CONCRETE BEAMS WITH THE USE OF COMPOSITE MATERIALS

Wide spread of RC structures in construction projects indicates the necessity of their service life prolongation. Perspective possibility to increase strength of RC structures is use of external composite tapes. The article presents theoretical research on the effectiveness of strengthening of RC bended elements with the use of composite tapes. Work also includes comparative analysis on the basis of calculations, according to normative regulations. With the use of developed algorithm parameters of stress-strain state and deformability of RC beams, strengthened with composite tapes were obtained. Study identified, that the most critical parameter was the steel bars` strain and yield point. Interesting finding of the study is the no-linearity of the strength growth of the studied elements with the increase of additional reinforcement amount. Consistent literature review was conducted, which identified the necessity to take into account different external factors and failure mode.

Особенности динамики напряженно-деформированного состояния перед землетрясением M7.1 Риджкрест 2019 г. по результатам численного моделирования

The paper is concerned with the analysis of the simulated stress-strain state (SS) parameters of the earth's crust over the four-year period preceding the M7.1 2019 Ridgecrest earthquake in Southern California. SS parameters have been calculated using a detailed geomechanical model, taking into account an ongoing weak seismicity catalog data. Cyclic patterns are identified in the observed shear strain anomalies, with estimation of their spatial and temporal characteristics, and an attempt is made to track the influence of the local displacement direction and periodic migration of shear strain anomalies in the upper crust on the earthquake preparation. Finally, we discuss the role of the observed regularities in terms of existing models describing the earthquake preparation process.

Deformation Mechanics of Fiber-Reinforced Plastic Specimens in Tensile and Compression Tests 1. Theoretical and Experimental Methods for Determining the Mechanical Characteristics and the Parameters of Stress-Strain State

Deformation Mechanics of Fiber-Reinforced Plastic Specimens in Tensile and Compression Tests 1. Theoretical and Experimental Methods for Determining the Mechanical Characteristics and the Parameters of Stress-Strain State

Stress state of the grinding tool loaded with tangential force

Purpose. Determining the interaction mechanism of discrete grains through material that binds them in a tool for abrasive material processing in the case of its loading with a tangentially directed cutting force. Methodology. Development and analytical solution to a mathematical model formulated on the basis of static equilibrium of an abrasive grain as a system element of tool grains bound with a material with excellent mechanical characteristics. Findings. A mathematical model has been developed and an algorithm has been formulated to analytically determine the stress-strain state parameters of a tool for abrasive processing of materials, which is loaded with a discrete cutting force, tangential to its working surface. The nature of the dependence of stresses and deformations on mechanical parameters, the quantity of grains and the material binding them in an abrasive tool, loaded with a unit tangential force, has been determined. Originality. The loading of the extreme grains leads to greater displacements, tangents of the shear angles of the material binding the grains. They decrease with increasing quantity of grain rows in the tool or with increasing quantity of grains to the nearest tool edge. Practical value. The distribution of interaction forces of grains and stresses in the material binding them has been determined. The found distribution allows one in the process of developing the tool and technology, in which it is involved, to comprehensively assess the influence of tangential load value of the tool working grain on its stress state and the material containing the grains. The determined stress state makes it possible to predict the number of loading cycles until the simultaneous rational wear of the grain and the destruction of that part of the material that contains it. The linear formulation of the problem makes it possible to take into account the mutual influence of the tangential loads of several grains on the stress-strain state of the tool as a whole.

Evaluation of the self-induced vibrations modes of bridge superstructure during monitoring

In the last 20–30 years, bridge condition monitoring during the operational cycle has become increasingly common on the Russian highway network. The monitoring ensures control of the bridge on an ongoing basis in a continuous mode. The task facing the monitoring systems developers is to expand the range of the parameters that can be used in real-time to monitor the bridge’s condition and the safe conditions for its operation. One way is to use indirect parameters obtained as a direct data processing result. Appropriate algorithms for converting information recorded by the system sensors and obtaining new parameters are needed. The most important design characteristics are dynamic characteristics, which include the frequencies and amplitudes of the self-induced vibration modes, and vibration decrements. This article discusses a technique for estimating the dynamic bridge characteristics, namely, the self-induced vibration modes frequencies and amplitudes using experimental data. A dynamic system mathematical model that performs self-induced vibration is considered in the system form with one input signal and n output signals. Formulas for the model frequency response and its components are given: the amplitude and phase response of the system. To calculate the frequency response, power spectra and cross-power spectra are needed, which are obtained using the Fourier transforms of the signal. The article shows how, to reduce the random error, to estimate the mutual spectrum by dividing the realizations into several adjacent intervals (segments) of length T each. The final spectrum (periodogram) is obtained as the arithmetic mean of the segment spectra. Monitoring systems using accelerometers that measure the structure linear accelerations of the record the output signals. One of the accelerometers is considered an input signal source. According to the proposed mathematical model, the self-induced vibration frequency response of the system characterizes the amplitudes and signs of the structure displacements at the accelerometers’ location at different frequencies. The mathematical apparatus considered by the authors is applied to the data obtained on a real object: a bridge crossing over the Volga river on the highway Nizhny Novgorod-Shakhunya-Kirov in the Nizhny Novgorod region — Borsky Bridge. The monitoring of the bridge state stream crossing the Volga by its purpose is control and research, in terms of the form of information presentation over time — continuous, in terms of the speed and synchronism of polling sensors — dynamic. The monitoring purpose is to monitor the bridge structure operation and its operating conditions, including the technical control of the stress-strain state (SSS) parameters. The bridge characteristics and the current monitoring system are given. The results of numerical calculations of the arch span for vibrations are presented. The authors performed periodogram calculations using the mathematical package MathCad using the signals of two accelerometers. To estimate the frequencies and amplitudes of the span structure vibration modes using monitoring data, periodogram calculations were performed using the SpektrKatKross program that implements the proposed algorithm. The correspondence results of the program to the results of the calculations by the program MathCad are shown. The calculated and experimental vibration modes of the span are close. As a result of using the proposed mathematical model, the reliability of this comparison is ensured both in terms of frequencies and in terms of amplitudes.

ОСЛІДЖЕННЯ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ ЗАЛІЗОБЕТОННОЇ МОНОЛІТНОЇ ПРОГОНОВОЇ БУДОВИ МОСТУ ПІСЛЯ ТРИВАЛОЇ ЕКСПЛУАТАЦІЇ

Introduction. The vast majority of reinforced concrete bridges built in Ukraine until the 1950s were mostly monolithic. Spans were built of monolithic concrete with a length of 2, ..., 6 m and ribbed structures with a length of 8, ..., 15 m. Monolithic spans were provided with good spatial work and considerable durability. Problems Statement. The main disadvantage of reinforced concrete monolithic spans of bridges built before the 50s of the last century was the low design strength of concrete, which over time led to defects and thus reduce their durability. In addition, the vast majority of such bridges with monolithic spans were built according to technical standards of 1962 and earlier, and at this time the load capacity does not meet the requirements of modern regulations. The need to study the stress-strain state, to determine the bearing capacity of the spans of bridges after long-term operation, given the above, is an important factor in deciding on the feasibility of their repair. Purpose. Research of the stress-strain state of the structures of the monolithic spans of the bridge after its long operation. Materials and Methods. A survey of the monolithic reinforced concrete span of the bridge, built in 1940, was carried out. It was established that the span of the bridge, in accordance with the identified defects, is in a limited working condition (condition 4). And given the low load capacity of the span, condition 5 (inoperable) was finally adopted. The main defects found during the inspections of the span significantly reduce its durability and bearing capacity. Destruction of the protective layer of beams of the span with exposure and intensive corrosion of reinforcement with weakening of the area by more than 10% was revealed. Based on the data from the inspection of the bridge, it was decided to conduct additional tests to determine the stress-strain state of the spans, the availability of strength reserves and the possibility of strengthening them or the need for replacement. Results. Based on the test of the bridge, the parameters of spatial work and stress-strain state of the span were determined by measuring the absolute deformations (deflections) under the action of static load. According to the test results, the value of the design coefficient k, which is in the range of 0.1… 0.79, was determined. The values of the transverse distribution coefficients (CRC) for each beam were experimentally determined and the numerical analysis of the field and analytical spatial work of the span of the bridge on the transverse distribution coefficients was performed. Conclusion. The results of the analysis of experimentally and analytically obtained test data of the bridge indicate the normal spatial operation of the bridge spans, which corresponds to the nature of the idealized finite element scheme, good spatial rigidity and the presence of strength reserves in the bridge spans. Key words: bridges, span, tests, deformability, technical condition.

Justifying the parameters of ore fields underground mining with goaf backfilling

Relevance. Manmade deposits have a major impact on environmental ecosystems in mining. Therefore, the priority direction of comprehensive research is the creation of technologies and technical means based on minimizing production waste. Research objective is to justify the parameters of ore fields underground mining with goaf backfilling using mathematical modeling and multi-criteria minimization of mining waste based on the results obtained by the regression analysis and planning of an experiment, ensuring economic efficiency and environmental safety growth, as well as subsoil rational use and protection. Methods of research. The parameters of technogenic deposit formation when extracting ore by traditional and alternative technologies were determined. The earth’s surface and underground working stress-strain state parameters were calculated. The technologies of converting inactive reserves of technogenic deposits into active ones by influencing them by physicochemical processes were studied. Parameters and regression dependences were calculated using the Maple 9.5 mathematical software package. The presented graphs were built in Maple 9.5 or Microsoft Excel using standard and new methods. Results. It is shown that the preservation of the rock mass implies the possibility of controlling the main stresses by limiting their deformations by filling technogenic voids with hardening mixtures of different composition and strength from 1.2 to 6.0 MPa. The structural weakening coefficient increases towards the periphery to 0.15, which means a decrease in strength in comparison with the undisturbed massif from 1.5 to 6.0 times. Conclusions. The regression dependences of profit on the coefficients of losses and dilution, indicators of soil excavation, total processing costs, as well as damage (economic consequences) from dilution of ore in the vicinity of the optimum point are obtained. The profit dependence is a convex monotonically decreasing function, where the profit value is the smaller, the greater the ore dilution coefficient. With an increase in the ore dilution coefficient to 0.6, the profit value will fall to 50.5 rubles/t, i.e. more than 20%. The main directions of modernization of technologies for underground mining of mineral deposits are recommended, taking into account their combination within a single mine field.

Investigation of fracture of ‘PEEK-CF-prepreg’ US-consolidated lap joints

In this paper, the effect of ultrasonic welding (USW) parameters on the tensile strength of the polyetheretherketon (PEEK) lap joints is reported. The adhesion levels between the joined parts were varied due to different thicknesses and properties of prepreg, as well as some features of the implemented USW procedures. To identify the key resulting factors, computer simulation of the process was applied. The stress-strain state parameters in the lap joints under tension were determined by the author’s software package based on the flat statement of the elasticity theory solved using the finite element method. Changes in the properties of the materials and their delamination were taken into account in the applied algorithms. It was shown that the main parameters influencing the tensile strength of the US-welds were the adhesion level and the number of contact points at the interface. Both macro- and micro-bending of the lap-joints were revealed. Their values depended on the thickness and properties of the interfaced layers (adherends) and affected the tensile strength of the US-welds.

Development of methods and software algorithms for state forecast of the ultimate stressed rock massif

The article covers a live scientific problem consisting in development of new and improving of existing digital technologies for forecasting a stress-strain state of ultimate stressed rock massif. The analysis of the researches has shown that the approaches based on the synthesis of mine monitoring methods and analytical forecasting methods are promising for assessing the state of ultimate stressed rocks. The existing hazard indicators can be beaded by the integral indicators of the stress-strain state of the rock massif determined with the help of geo-information systems. However, there are no methods, algorithms and software for figuring these indications. As a result of the research, methods of implementation and functions of software elements have been developed for determining integral indicators characterizing the state of an ultimate stressed rock massif. The “Methodological recommendations …” have been developed, which describes specificity of using the information system for forecast integral parameters of the rock massif stress-strain state and assessing the conditions for the rock destruction. The use of the designed methods, algorithms and software decreases geomechanical risks of gas-dynamic phenomenon occurrence, reduces cost of breakdown elimination and increases economical efficiency of the mining enterprises.