Destruction Of Material Research Articles

Physical Processes in the Thermal Vacuum System

Physical processes occurring during dehydration of heterogeneous materials in a thermal vacuum system have been analyzed. It has been demonstrated that the thermal-vacuum method provides dehydration and simultaneous wet-stock dispersion due to thermal diffusion, shock-wave and ionization effects, thereby leading to formation of novel-type nanodispersed material at minimum energy input. In recent years the intensification of production processes, as well as the solution of energy- and resource-saving problems have taken on great significance. For the sake of dehydration working-cycle improvement, combination of several process procedures in a single installation is used, resulting in both the intensification of the production process and the reduction in capital expenditures. There are the facilities, where the simultaneous use of mechanical grinding operation and the drying process is practiced. In this case, a preheated air is used as a drying agent, and this considerably increases the energy demands of the technological process. This phenomenon is attributed to the impact action and friction of material particles against grinding surfaces of the mill, to the appearance of new surfaces at crushing, and also, to the dust-gas mixture turbulence in the mill working area. That requires substantial power consumption and prevents from obtaining the product with desirable indicators, in particular, the with dispersion and moisture content, which substantially affect the quality of materials produced from fine-grained products. The analysis of fine grinding methods has shown that the most rational method of material grinding is the combination of impact loads. The impact loads facilitate the structure destruction of wet stock, while the abrasion loads acting in the field of high turbulent flows lead to the material destruction. The aim of the present work has been to define the physical processes in the thermal vacuum system, which can efficiently provide dehydration along with simultaneous dispersion of wet material, yielding a dried and ground feedstock in a short span of time.

Calculations difference of hight-speed working units depending on the kinematics of their working processes

High-speed working units are very widely used in modern construction, in the destruction of durable materials and soils and more. When calculating the power and energy parameters of dynamic working units take into account changes in the nature of the interaction of the cutting element with the environment and the emergence and propagation of soil stresses from the action on the boundary of the array of the cutting element. This leads to the emergence of a stress-strain state in the soil mass, which has an oscillatory-wave character.
 The nature of the stress-strain state is influenced by the state of the working environment and the speed of cutting (destruction) of the soil mass.
 An unsolved problem in the dynamic destruction of soils is to take into account the kinematic features and technology of work with high-speed peripheral and front-end working units. The design parameters of these working units must take into account not only the dynamic parameters of the fracture process, but also the phenomenon of accumulation of fatigue deformations in the working environment.

STRUCTURE FORMATION OF DISPERSED-REINFORCED BUILDING COMPOSITES

Abstract. The results of the study of the mechanism of structure formation of cement compositions reinforced with finely dispersed monofilament are presented in the article. The mechanism of microstructure organization of construction composites was studied on models of dispersed systems, with different qualitative and quantitative composition of linear and dispersed particles. At the same time, restrictions had been placed on particle size – fiber diameter and diameter of dispersed particles are proportional to each other. Study of cracking formation kinetics was carried out on disk-shaped samples made of water-clay and water-cement compositions. Physical and mechanical characteristics of dispersed-reinforced cement stone, including non-reinforced stone, have been defined on prisms-shaped samples of square section with size 40×40×160 mm. The analysis of physical models showed that cluster structures filling with particles of various nature and shape increases structural diversity of entire dispersed system. An inserting of linear particles changes nature of system structure formation. Depending on the characteristics, structural components of the system, substructures are formed, which differ in the periods of their formation and geometric parameters. It has been established that dispersed particles of different nature are structured in different ways into clusters with discrete fibers of different length. Linear particles were more active in the creation of structural aggregates (clusters) comparing to dispersed grains. The impact of highly dispersed fibers on the structure organization of the binder compositions was quantified by the damage coefficient determined on samples of different types. The presence of discrete fibers in the composition of the material leads to modify the qualitative characteristic of compositions cracking formation. Improvement of physical and mechanical properties of the dispersed-reinforced composite confirms the ability of the fiber to change a mechanism of material destruction due to a probable deposition of hydration products on monofilaments, to densify and strengthen the interfacial transitional zone.

Cultural Heritage of Lemkos as a Research Problem in the Humanities and the Topic of Discourse in Poland

Cultural Heritage of Lemkos as a Research Problem in the Humanities and the Topic of Discourse in Poland
 The cultural heritage of Lemkos is today one of those European values that have found themselves in danger. The reason for this is not only the project of political and economic unification of Europe, which will inevitably trigger far-reaching cultural unification and violate ethnic and national traditions in its area, but also an event from over 80 years ago – the displacement of Lemkos from their homeland and the dispersion and assimilation in a different ethnic environment, as well as the destruction of material and spiritual heritage on the territory of this homeland and its resettlement by newcomers inheriting an alien culture. Among the many issues that come with it, two are the subject of this review. The first are the attitudes of Poles towards the Lemko heritage, which are reflected in the public discourse understood here not only as statements, but also as initiatives. The importance of this issue stems from the fact that the fate of the Lemko heritage is decided primarily within the context of contemporary Polish culture, although it is justified to disagree with the common identification of Poland with the communist authors and performers of the action of 1947, which destroyed the Lemko region as a homogeneous cultural area. The second issue is the way of analyzing the fate of this heritage in the humanities, wchich is devoid of a comparative perspective. It dominates today, narrowing research horizons as well as exerting a tangible influence on the choice of strategies for rescuing and transmitting endangered cultural content. In this regard, attention should be paid to the need to learn about and compare analogous cultural catastrophes caused by communist totalitarianism, as well as the strategies of survival and rebirth of the destroyed cultures.

The Applied mechanical and mathematical model of grinding of a solid particle by static crushing

Now crushers are one of the most common types of crushing equipment using the principle of a mechanical method of material destruction (for example, rollers, jaws, cone crushers, etc.). To provide effective parameters of the crusher, it is necessary to take into account the correlation between the physical and mechanical characteristics of the material (sizes, shapes, strengths, fragility, uniformity, etc.) and the energy parameters of the crusher (operation and power) at the design stage. The existing theories describing the mentioned dependence and relying on different classical hypotheses allow obtaining a very approximate (inaccurate) result. Consequently, it is necessary to develop a detailed theory of crushing capable of an accurate description of the mechanical process of material destructions by working members of the crushers. Thus, the authors have developed the crushing theory as an original solution of a complex constructively nonlinear engineering and technical problem on the static contact of a spherical model of a comminuted brittle substance with absolutely rigid convex-concave surfaces of cylindrical rolls designed for coarse and medium grinding. The theory is based on the classical assumptions of the mechanics of an elastically deformable continuous medium, the fundamental analytical dependences of Hertz-Shtaerman and the Kirpichev-Kick volumetric energy hypothesis. During the quantitative assessment of the bearing capacity of the ball, we used the well-known physical and mathematical problem of Weber on the stress state of a sphere loaded by two equal forces applied at the poles, and the Kulon-Mor’s strength criterion, which describes the process of destruction of a wide class of brittle homogeneous materials. The developed theory of fragmentation has been brought to the design formulas and illustrated with a typical numerical example.

Mitigation of impact force through optimisation of three-phase locally resonant structures

This study explored a new impact protection method based on three-phase locally resonant structures (LRSs), and this method did not rely on large structural deformation and material destruction. The performances of three LRSs with a steel cylindrical oscillator (LSCYO), aluminium cylindrical oscillator (LACYO), and steel cubic oscillator (LSCUO) were studied. A design with an optimised topology with the goal of maximising the impact attenuation was introduced to further improve the performance. The nonlinearities of the material, geometry, and contact were simultaneously considered in the optimisation of the design. The analysis results indicated that these optimal LRSs were anisotropic and could efficiently attenuate the impact load and absorb the impact energy. The attenuation effects of these optimal LRSs were better than those of the original and LRS models. In addition, the mechanisms of the energy absorption and conversion in the impact attenuation process were analysed. The vibration modes and propagation behaviours of the waves of these optimal LRSs were also studied. The attenuation frequencies of the waves and natural frequencies of these optimal LRSs were in good agreement, and the attenuation frequencies of the waves were all within the spectral range of the impact loads. In addition, multiple optimal LRSs were applied simultaneously to study their impact response, and the attenuation effect of the impact force was demonstrated. In short, this study investigated the attenuation mechanism of LRSs from the perspective of energy conversion, explored the new application scenarios of LRSs, and provided a novel solution for the impact problem, which is of significance in the field of functional structure design and impact protection.

Catastrophic Optical Damage in Semiconductor Lasers: Physics and New Results on InGaN High‐Power Diode Lasers

Among the limitations known from semiconductor lasers, catastrophic optical damage (COD) is perhaps the most spectacular power‐limiting mechanism. Here, absorption and temperature build up in a positive feedback loop that eventually leads to material destruction. Thus, this is truly an ultimate mechanism, and its continued suppression is a manifestation of progress in device design and manufacturing. After an overview of the current state of knowledge, new investigations of COD using artificially micrometer‐sized starting points created within the active zone in the cavity of 450 nm GaN semiconductor lasers are reported on. Defect growth mechanisms and characteristics are studied during 800 ns current pulses. The defect growth follows the highest light intensity. Secondary defect patterns are studied: complete destruction of the active zone and generation of a point defect cloud at least ≈10 μm into the remaining surrounding material. Extremely large angles (>90°) of damage growth are traced back to the material properties and the aging scenario. The results are compared with former experiments with GaAs‐based lasers.

Rainfall challenges and strategies to improve housing construction in Sub-Saharan Africa: the case of Ghana

Even though elsewhere in the Western world and the gulf regions, many studies explore the effect of extreme weather conditions on the construction of houses, little is known in sub-Saharan Africa. This study therefore engages homeowners and various construction workers in a qualitative study to analyze how rainfall affects the building of houses. A total of 75 participants, comprising 20 homeowners and 55 construction workers were purposively selected to share their experiences about the impact of rainfall on the construction of houses using in-depth interviews. The narratives of the participants made several revelations to deepen knowledge on the effect of climatic conditions such as rainfall on housing construction. The study revealed that rainfall causes financial losses to homeowners and creates hazardous work environments for construction workers. Financial losses are encountered through the destruction of building materials, increases in the cost of building materials in the wet season and extra labour costs incurred in carrying out reworks. This challenge posed by extreme rainfall has implications of hindering many prospective homeowners in achieving their aspiration of becoming homeowners.

Research of the parameters of acoustic emission signals during the destruction of the liner material and the power shell of a metal-composite high-pressure cylinder

To The article provides information on the results of studying the parameters of acoustic emission signals during the destruction of the liner material and micro-plastic of the power shell of a metal-composite high-pressure cylinder. B-200 within the framework of a complex of studies to create an acoustic-emission portrait of metal-composite high-pressure cylinders. It was found that the most informative parameter when carrying out technical diagnostics of a liner is the signal amplitude recorded in the private range of 60-80 kHz, and a sign of microplastic rupture is the emission of acoustic emission signals reaching 82 dB.

Acoustic emission control of tensile and compression defects for plastic carbon fiber samples reinforced with side girders

Tensile and compression tests of composite samples made of carbon fiber reinforced with side girders have been carried out. It was found that the area of active location of acoustic emission (AE) signals corresponds to the destruction of the composite, bolted and glued joints. Destruction of the carbon fiber-reinforced plastic material did not always occur in the area of the fasteners, but the sources of AE signals with the maximum total amplitude were registered in the destruction zones.

Research of the influence of the main parameters on the characteristics of an impact system with increased impact energy

A scheme of an impact mechanism for the destruction of strong materials is proposed, in which the reactive component is not transferred to the base machine. A system of differential equations is presented, the solution of which in the Matlab-Simulink environment is used to obtain regression equations that determine the influence of the main parameters on the characteristics of a system with increased impact energy. Keywords: impact mechanism, reactive component, destruction, impact energy. vzedgenizov@bk.ru

Experimental study of the destruction in CFRP laminates at the macro-level by acoustic emission method

The author conducted experiments using the method of acoustic emission under uniaxial tension of specimens of CFRP laminates with different stacking, geometry and stress concentration. The influence of a mutual arrangement of the material destruction zone and the extensometer installation site on the nonlinear deformation is revealed. It is shown that the damage accumulation process is highly informative when determining the energy of AE pulses. The possibility of visualizing the formation and development of destruction zones in orthogonal directions, as well as the possibility of determining the moment of crack start from the apex of the notch during splitting, is established. The mechanism of alternating stress relaxation in two developed zones of destruction is revealed. The paper shows a high degree of correlation between mechanic and acoustic-emission events. Finally, the author suggests assessing the mechanical state of material with the account of obtained damages by the degree of its integrity (one to zero) depending on the load history, its individual geometric features and stress concentration.

Discrete-continuous three-element model of impact device

There have been examined the mathematic model of the impact device provided for geological materials destruction. Basic elements of the impact device are variable cross-section tool, striker and impact device body. The interaction of these elements is described as a movement of two discrete mass and the rod in the presence of rigid and dissipative connections. One equation in partial derivatives and two ordinary differential equations associated by initial and boundary conditions represent the initial-boundary problem. The numerical method parameters of which are determined at tests problems solution by Fourier method is used for looking for solutions of mixed initial-boundary problem. Researches are made, and parameters determining the damping efficiency of tool, striker and impact device body oscillations are evaluated.

A more accurate definition of water characteristics in stone materials for an improved understanding and effective protection of cultural heritage from biodeterioration

The water associated with cultural heritage materials is the most important factor before initiation microbial colonization and subsequent biodeterioration processes to occur. Since moisture or water in such materials is the key to life, a more refined characterization of water is needed to advance the basic understanding of the fundamental mechanisms, especially for the accurate assessment of bio-susceptibility or bio-receptibility of different materials. Water can be categorized to free, gravitational, capillary, and hygroscopic to account for the physical states and sorption strength with the materials. Material porosity or water-holding capacity are fundamental criteria used in characterization of various types of materials on a common ground and basis, but pore connectivity has been largely ignored and must be addressed to establish the methods for assessment and also its relationship to bio-colonization and biodeterioration. When a threshold value of water in the relevant physical categories is available, microbial life can colonize and establish colonies as biofilms on materials surfaces to carry out the biochemical reactions leading to biodeterioration, from appearance of discoloration to physical damage of the materials. Microbial destruction of inorganic materials is mainly carried out by the biochemical reactions through carbon, nitrogen and sulfur cycles. Among material porosity characteristics, available water and microorganisms, mobility and movement of soluble salts under wet and dry cycles have significant impact on the durability of materials. Uptake of soluble salts and supersaturated salts in water into materials can result in crystallization and mineral formation under evaporation condition to initiate the internal stress and cracks, which eventually result in surface delamination and damage. From an architecture design point of view, it is clear that management of water is a basic and important strategy to prevent development of microbial issues in the long-term protection of cultural heritage.

Methods for calculation and experimental evaluation of nucleation and development of the fatigue damages in tin based babbitt and babbitt lining of plain bearings

Fatigue damage to babbitt layers of plain bearings is often manifested during operation. The goal of the study is to develop a model for accumulation of the fatigue damage and destruction of antifriction materials and layers of plain bearings. A generalized fatigue diagram of tin-based babbitts including the main stages of fatigue damage and a diagram of the fatigue damage development in the antifriction layer of plain bearings are presented. The generalized model of V. V. Bolotin for damage accumulation and destruction is modified with regard to antifriction materials containing rather large structural elements. An explicit (direct) modeling of damage processes appeared possible for such materials. The model describes dissipated accumulation of microcracks (interpreted as destruction of the elements of the material structure), initiation and development of a system of short cracks, initiation and development of macro-cracks up to the limit state of the object. The model suggests discretization of the volume into sections with constant levels of complex stress state and discretization of the time axis into the intervals (blocks of loading cycles). The problem of identifying the parameters of a multistage model of the fatigue damage accumulation in the alloy is solved proceeding from the analysis of the results of testing babbitt specimens. We used the simplest optimization procedure, i.e., the method of deformable polyhedron. The parameters of the power function in the dependence of the rate of microdamage accumulation on the level of stresses are obtained. The parameters of the initiation and development of the crack system in the babbitt layer are obtained from the analysis of experimental results of studying steel-babbitt samples. The problem of calculating the durability of antifriction babbitt layers required the development of a new software. The program is examined by comparing calculated and experimental values of the durability of fatigue-tested bearing specimens forced against a rotating shaft by varying cyclic load. The calculated values of the durability match the experimental which confirms the performance of the calculated model.

Exploring oxidation mechanism of graphene for insight into its outstanding corrosion resistance in sulfur-containing atmosphere

Sulfur and its compounds could accelerate the corrosion and destruction of metallic materials, while the novel graphene would provide an effective means to protect those facilities in sulfur-containing atmosphere. Therefore, it is of great significance to study oxygen diffusion so as to explore the corrosion mechanism of graphene in sulfur-containing atmosphere. In this paper, the thermodynamic and kinetic behaviors of oxygen on intrinsic graphene, defective graphene and fluorinated graphene in sulfur-containing atmosphere were systematically studied by first principles calculations. The results show that the presence of sulfur would increase the adsorption energy of oxygen and reduce the diffusion energy barrier of oxygen, thereby accelerating the oxidation failure of graphene. Furthermore, the oxidation resistance of defective graphene in sulfur-containing atmosphere was even worse. Surprisingly, it was found that the fluorinated defective graphene could possess a relatively small adsorption energy of O in sulfur-containing atmosphere, and it also have the higher diffusion energy barrier of O on defective graphene. As a result, the fluorinated graphene has a great potential as protective materials with superior oxidation and corrosion resistance in sulfur-containing atmosphere.

PROPERTIES OF BOILER FUEL COMPOUNDED BY NARROW FUEL FRACTIONS

In order to improve the performance properties, in particular viscosity-temperature, of boiler fuel, it is proposed to combine them with narrow fuel fractions obtained by thermal destruction of secondary polymer raw materials (low pressure polyethylene and polypropylene).
 When compounding grade 100 fuel oil with narrow fuel fractions, the values ​​of density are reduced to 865 (873) kg / m3, conditional viscosity to 2.50 (2.63) deg. um., pour point up to 8 (13) °C), sulfur content up to 0.17 wt%. and the lower heat of combustion increases to 43606 (43850) kJ / kg. At the same time, there is a gradual decrease in the value of the flash point to 114 (127) °C.
 This reduction is a negative point, which leads to increased fire safety of fuel oil during its use, storage, pumping and transport. However, the values of the flash point, according to the requirements of regulatory documentation, are within acceptable limits. That is, the value of this indicator can limit the content of fuel oil in narrow fuel fractions.
 It is determined that the rational concentration of narrow fuel fractions in the composition of fuel oil grade 100, is within 30% of the mass. Within these limits, there is a permissible decrease in flash point values – an indicator that characterizes the fire hazard of fuel oil during its use, storage, pumping and transportation against the background of improving other performance properties of fuel oil.
 The production of the proposed compound boiler fuel on the one hand allows to expand the raw material base of the process by involving in the production process secondary polymer raw materials – solid waste subject to mandatory disposal, on the other – to meet existing demand for boiler fuel by increasing its production.

THE INFLUENCE OF THE STORAGE CONDITIONS OF RAW MATERIALS ON THE PRESERVATION OF THE PROPERTIES OF THE FUR SEMI-FINISHED PRODUCT

This article deals with the problem of preserving the properties of a semi-finished fur product under the influence of a biological factor during the storage of raw materials. The characteristic features of the biodegradation of untreated rabbit skins during storage at elevated temperature and relative humidity are identified and described. A complex characteristic of a semi-finished fur product developed from raw materials of various degrees of microbiological spoilage is given. The author offers a point scale of assessment dynamics of the processes of destruction of fur raw materials and a point assessment of the organoleptic indicators of the semi-finished product was developed. As a result of comprehensive studies, it was found that the degree of damage to the fur raw materials being processed affects the decrease in the stability of the structure and strength properties of the finished semi-finished product.

ОБҐРУНТУВАННЯ ТРАНСПОРТНИХ ПАРАМЕТРІВ ТА МОДЕЛЮВАННЯ ПРОЦЕСУ РУЙНУВАННЯ ПРУЖНО-ПЛАСТИЧНОГО СЕРЕДОВИЩА

Purpose. The substantiation of the mathematical model of mechanical deformation of the elastic-plastic medium and the modeling of the transport process of the expansion assemblies. Methodology. Mathematical and theoretical studies were based on the fundamental theory of continuum mechanics and general positions of engineering mechanics. Analytical and graphical analysis of mathematical models carried out on a PC in a specialized software complex. Results. In the current conditions of economic development of the country, considerable attention should be paid to the development and modernization of certain sectors of the economy. Significant amounts of work, which are accompanied by the development of soil of different properties, which can be defined as an elastic-plastic material. These studies will solve a number of problems that are acute not only in agriculture but also in construction, in the open pit mining, reclamation, one of which is an imperfect process of loosening the soil during its cultivation. Therefore, the urgent problem is to establish rational parameters of the transport surface of the unit for loosening the elastic-plastic material. The developed mathematical model allows determining the emerging stress, which in turn determines the boundary of the destruction of the elastic-plastic material. In the design of lining assemblies, it is advisable to have a radius of the outlet section R = 0.18 m or more. Originality. The mathematical models for the process of destruction of elastic-plastic material and forecasting of optimal transport parameters for designing of expansion assemblies are obtained. Practical value. The developed mathematical model will provide an improvement in the process of loosening elastic-plastic material, and engineering calculations during the design of the rutter can prevent unwarranted increase in resistance, with displaced materials on the cutting surface. References 10, figures 8.

REW Application Possibilities for the Production of Combined Metal - Plastic Joints

In this paper, innovative resistance element welding (REW) technology for joining galvanized steel sheets to thermoplastics (PMMA) is introduced. The essence of the innovation is in the use of a special bimetallic joining element consisting of the core made of a Sn60Pb solder, and the sleeve made of a Cu tube. During resistance heating, the solder melts, thus allowing the formation of a metallurgical joint with galvanized steel sheet. Since Sn60Pb solder melting occurs at temperatures (from 183 to 190 °C) be-low the thermal decomposition temperature of most thermoplastics (for PMMA above 300 °C), there is no thermal destruction of the PMMA material around the joint. The mechanical fixation of the thermo-plastic material at the overlap joint is provided by the sleeve made of Cu tube which has a substantially higher strength than a Sn60Pb solder.