Main Mechanical Characteristics Research Articles

Minimization of the Negative Environmental Impact of Oil Sludge by Using it in the Production of Bitumen

Abstract In this paper, the prevention of negative technogenic impact on the environment of oil sludge by using it as a secondary resource is considered. Oil sludge from various objects of oil fields in Kazakhstan (Mangystau region) has been studied. The possibilities of using oil (after its separation from oil sludge by bioremidiation) as a partial substitute for bitumen base in the production of modified bitumen are considered. The main physical and mechanical characteristics of modified bitumen are determined. The results confirm that the modified bitumen prepared with oil sludge and oil separated by bioremiation method meets the requirements for polymer-bitumen binder to Kazakhstan standards and is suitable for the production of modified bitumen in its physico-chemical characteristics.

Technical Feasibility of the Use of Sandy Loam Soils in Concrete

In Mozambique, the task of providing infrastructural facilities for the rapidly growing population is enormous. Although the country has unique characteristics that present opportunities for timber construction to thrive, concrete continues to be one of the most used materials in modern construction. However, the concrete industry has a considerable impact on the environment due to production and the raw material consumed. Among the constituents of concrete, sand has been the one in which its exploitation causes the most damage to the environment. An alternative to solve this problem would be the use of fine sandy loam aggregate in the production of concrete. Thus, this research presents the study of the technical feasibility of using fine sandy loam aggregate in the production of concrete. The main study variables were the consistency and mechanical strength of concrete compression. For the production of concrete, two types of gravel of ¾ were used, sandy loam soil, sandy soil and Portland cement. Specimens were manufactured for 4 different mixes, with a reference mix containing cement, sand, gravel and water. To evaluate the performance of the mixes, tests of mechanical resistance to compression were carried out at 7, 14, 21 and 28 days of age. After determining the main physical and mechanical characteristics, promising results were obtained for the mixtures with 25% and 50% substitution, where the axial compressive strength test reached 26.3 MPa and 27 MPa, above the reference mixture of 25.6 MPa. The 100% mix of alternative soil reached an average strength of 25.2 MPa. This same mixture, although having low mechanical strength, has greater consistency, with a slump of ±10 cm. Keywords: concrete, cement, environment, fine aggregate, mechanical strength. DOI: 10.7176/CMR/14-1-02 Publication date: January 31 st 2022

Conceptual Approaches to Solving the Issue of Reinforcing the Rock - Cut Structures of Geghard Monastery Complex

The article presents a visual and instrumental research of the technical condition of the main rock-cut structures and their masonry additions, the documentation of their damages (cracks, crevices, destructions and erosions) and deformations, thorough complete laboratory studies of rock samples and their physical and mechanical characteristics, conceptual approaches to preventive and reinforcing measures necessary for the further safe survival of structures, as well as the comprehensive development and implementation of measures to prevent further damages (elimination of causes) and ensure the long-term existence of structures. Based on the analyses carried out, it is recommended to use a ready-made dry mixture mortar of the “Mapegrout'' brand produced by the Italian company “Mapei” to fill cracks if necessary. It is available in the market of the country and is successfully used in the reconstruction of tunnels and other underground structures. The issues of compatibility of reinforcing materials with sandstone rock are also considered on the basis of some averaged data of the main decisive physical and mechanical characteristics of the strength and deformation of sandstone.

INVESTIGATION OF THE PROCESS OF MODIFICATION OF PETROLEUM ROAD BITUMEN BY MALEIC ANHYDRIDE

The possibility of modification of oxidized petroleum bitumen 70/100 produced by JSC "Ukrtatnafta" (Kremenchuk, Ukraine) with maleic anhydride was studied. The influence of maleic anhydride amount, process duration, and temperature on the main physical and mechanical characteristics of modified bitumen was studied. The optimal amount of maleic anhydride introduction to bitumen was established. It is found that 2 wt. % maleic anhydride allows to increase the softening temperature of the modified bitumen (from 46 °C to 52 °C). Adhesion to crushed stone also increases (from 2.5 points to 4.5 points) and other indicators improve. Sufficient time to modify the bitumen with maleic anhydride was 30 minutes. The optimum modification temperature for obtaining the modified bitumen with maleic anhydride is 130 °C. Increasing the temperature of the modification has a negative effect on the final physical and mechanical properties of the binder.

Mathematical Apparatus for the Synthesis of Composite Materials with Specified Properties

The meaning of the creation and functioning of the system is defined as the achievement of extreme values of goals that unite the individual elements of the system into a single whole. Based on this, the main system attributes of composite materials are indicated. It is assumed that the systemic effect is generated by the systemic properties of quality criteria. The implementation of the technical task is initially determined at the stage of cognitive modeling with the establishment of intensive and extensive properties with the allocation of control parameters. Based on the cognitive map, hierarchical structures of quality criteria are determined, and in accordance with the selected quality criteria, the corresponding structural schemes of the system (for each selected scale level). Further, the system's quality criteria are formalized, and mathematical models are developed in accordance with each of the criteria. The main purpose of using system analysis is to apply the general principles of decomposition of the system into individual elements and establish connections between them, in determining the research goal and stages to achieve this goal (based on solving single-criterion optimization problems using the found optimal values). The formalization of the multicriteria problem and its solution are made based on the required operational values, the type of kinetic processes of the formation of the physical and mechanical characteristics of the material (determine its structure and properties). The problem of materials synthesis is reduced to the choice of the order and type of the differential equation; parametric identification within the chosen model; comparison of experimental and model kinetic processes at a given accuracy; adjusting the model (if necessary). Therefore, it is important to interpolate the kinetic processes of the formation of the main physical and mechanical characteristics of composite materials. The technological process is considered as a complex system consisting of elements of various levels of detail: from atomic to a separate process. Decomposition of the technological process consists in dividing it into basic operations (elements): preparation of materials, mixing of components, molding of a semi-finished product, heat treatment and additional operations. The effectiveness of this approach was confirmed in the development of chemically resistant sulfur composites, epoxy composites for radiation protection, etc. The initial prerequisite was the required operational values of the material and the type of kinetic processes. The results of effective use of interpolation models (including splines) of compressive strength, heat release, and shrinkage of composite epoxy materials are presented.

Representative Volume Element (RVE) Analysis for Mechanical Characterization of Fused Deposition Modeled Components.

Additive manufacturing processes have evolved considerably in the past years, growing into a wide range of products through the use of different materials depending on its application sectors. Nevertheless, the fused deposition modelling (FDM) technique has proven to be an economically feasible process turning additive manufacture technologies from consumer production into a mainstream manufacturing technique. Current advances in the finite element method (FEM) and the computer-aided engineering (CAE) technology are unable to study three-dimensional (3D) printed models, since the final result is highly dependent on processing and environment parameters. Because of that, an in-depth understanding of the printed geometrical mesostructure is needed to extend FEM applications. This study aims to generate a homogeneous structural element that accurately represents the behavior of FDM-processed materials, by means of a representative volume element (RVE). The homogenization summarizes the main mechanical characteristics of the actual 3D printed structure, opening new analysis and optimization procedures. Moreover, the linear RVE results can be used to further analyze the in-deep behavior of the FDM unit cell. Therefore, industries could perform a feasible engineering analysis of the final printed elements, allowing the FDM technology to become a mainstream, low-cost manufacturing process in the near future.

Longitudinal-transverse coupled vibrations of variable-height asymmetric beams: Modeling, analysis, and case study

In general, the cross-sectional centroids of the variable-height asymmetric beam change in the height direction. The Timoshenko beam theory does not consider the influence of the varying cross-sectional centroids and cannot accurately reveal the vibration of variable-height asymmetric beams. Considering that the cross-sectional centroids are dislocated, we propose a novel dynamic model for the variable-height asymmetric beam element. The proposed dynamic model is based on the rigid-plane assumption and can reflect its main mechanical characteristics. The non-collinear axial forces produce the complementary moment. The rotational radiuses of the two ends of longitudinal fibers are not equal. After retaining the main mechanical characteristics, the variable-height element is roughly treated as a constant-height element to simplify the governing differential equations. A bonded-type piezoelectric transducer with variable-height asymmetric beams is taken as an example to verify the developed dynamic model. The theoretical and experimental resonant frequencies are 39338 Hz and 38704 Hz, respectively, with a difference of 634 Hz and a relative error of 1.638%. The calculated displacement vibration shapes are consistent with the experimental results. Finally, the modeling differences between variable-height symmetric and asymmetric beams are clarified from three aspects.

Foamed gypsum for multipurpose applications in building

Gypsum plasterboards are nowadays very appreciated in buildings, mainly due to their lightness, thermal insulation and suitable sound transmission loss when used in double walls. However thermal and acoustic features of gypsum plasterboard can be enhanced. In the present study an innovative method, consisting in the direct addition of a pre-manufactured foam to gypsum pastes is used to increase the gypsum porosity improving sound absorption, lightness and thermal insulation features. In this aim, the role of both different amounts and dilutions of a vegetal foaming agent on the main physical, mechanical and microstructural characteristics of the gypsum was experimentally investigated. Moreover, also X-ray computed micro tomography technique (Micro-CT) was carried out in order to investigate the 3D internal microstructure of the materials. The results confirmed the effectiveness of the foaming agent in increasing the gypsum porosity, with a linear correlation between densities and mechanical strengths. Moreover, the presence of large bubbles, mainly connected each other, involved in a strong reduction of the thermal coefficient (λ), from 0.57 W/m∙K of REF sample to 0.25 W/m∙K of LG10_5% sample, and in a strong increase of the normal sound absorption coefficient (α0), from 0.06 of REF sample to 0.20 of LG10_5% sample. Finally, in the light of the results obtained by the present research, the use of a pre-whipped vegetal foaming agent represents a suitable way to obtain lightweight gypsum-based materials with enhanced thermal and acoustic properties.

Influence of angle of laying of layers of composite material on the basis of carbon on its mechanical characteristics at pure tension

The paper presents the results of experimental studies to determine the mechanical characteristics (Poisson's ratio, modulus of elasticity, tensile strength) of carbon-based composite materials with different compositions according to the number of layers and the direction of the fibers in it. A mathematical model is proposed, which allows, in the first approximation, to determine the main mechanical characteristics of the composite material and takes into account its structure (the maximum number of layers of composite material, which was considered in this work - 7). The parameters of the model were determined by the conducted regression analysis. The results of analytical calculation according to the proposed model are compared with the experimentally obtained values of mechanical characteristics. It is shown that the maximum error does not exceed 12%.

Copolyesters based on 3,5-dibrom-4-hydroxybenzoic acid chloranhydride

Modified copolyesters using 3,5-dibromo-4-hydroxybenzoic acid chloride have been synthesized by the method of low-temperature polycondensation (acceptor-catalytic polycondensation). The main laws governing the synthesis of copolyesters have been studied. It was found that the presence of bromine atoms reduces the reactivity of the hydroxyl group due to the steric effect, as well as due to the possible formation of a weak hydrogen bond between the bromine and hydrogen atoms of the hydroxyl group. The main physical and mechanical characteristics of the synthesized copolyesters have been investigated. Copolyesters are heat- and fire-resistant high-strength polymers that can be used in various industries as non-combustible heat-resistant structural polymer materials.

Fast-setting concrete with increased hydrophobicity

The article discusses the influence of chemical additives such as: Glenium 850, Sika ViscoCrete EWR100 and JV Relamix T2 on the main physical and mechanical characteristics, such as the strength and water resistance of concrete.

Comparison between Modelled Influence of GMAW Parameters and Corresponding Mechanical Properties of Group 1 and 2 According to ISO/TR 15608 Steel T Joints

Reproducibility in respect to welded structures realization is one of the main requirements for a wide variety of industrial applications. One of the international tendencies regarding the use of the steel is the replacing, in critical areas, of structural steels with high performance steel, e.g. with HSLA steels. The paper presents the results of a factorial designed experimental program focused on determining mathematical correlations between the GMAW process parameters for T joints of 4mm thick steel plates of structural (S235JR+AR according to SR EN 10025-2) and hot-rolled, high-strength low-alloy (HSLA) steel plates (S420MC according to EN 10025-4), respectively. A comparison between the obtained mathematical correlations that connect the welding parameters and the main mechanical characteristics is presented. The correlations can be used for applying the optimal combination of welding process parameters for realizing the T-joints of welded products.

Industrial Heat Treatment of Wood: Study of Induced Effects on Ayous Wood (Triplochiton scleroxylon K. Schum)

High-temperature treatment of wood is a useful method for improving certain physical characteristics, ensuring durability without biocides, and improving the performance of wood when exposed to degradation agents. This work aims to determine the effects induced by a heat treatment performed industrially on ayous wood (Triplochiton scleroxylon K. Schum) from Cameroon, through the study of the main physical and mechanical characteristics. The heat treatment at 215 °C for three hours with a slight initial vacuum determined a reduction of the mechanical characteristics (compression strength 26%, static bending 46%, Brinell hardness 32%) and some physical properties (dry density 11%, basic density 9%), while it improved the behaviour towards variations of environment moisture. The anti-shrinkage efficiency was 58.41 ± 5.86%, confirming the increase of the dimensional stability. The darkening (ΔE 34.76), clearly detectable (L* 39.69 ± 1.13; a* 10.59 ± 081; b* 18.73 ± 1.51), was supported almost equally by both the lightness parameter (L*) and the a* chromatic parameter. The data collected during the laboratory tests were then subjected to statistical analysis to verify correlations between the characteristics examined. Statistical differences were highlighted between each physical and mechanical properties of ayous wood modified or not.

Sintering and properties of materials based on nanosized silicon nitride powder

A high-density material (ρ = 3.28 g / cm3, porosity 1.4% by volume) based on nanosized silicon nitride powder was obtained by the method of liquid-phase sintering. The effect of compacting pressure on the density of sintered silicon nitride materials is shown. The process of material structure formation during sintering has been studied. The main physical and mechanical characteristics were determined: density, porosity and grain size of the solid phase, elastic modulus, flexural and compressive strength, crack resistance coefficient, Vickers hardness.

On ways to increase protection of special structures from impact action

The technique of research of dynamic processes of elements of engineering constructions of special purpose from explosive action of projectiles is developed. Elastically reinforced beams with hinged ends were chosen for the physical model of elements of engineering structures. It is assumed that the elastic properties of the latter satisfy the nonlinear technical law of elasticity. A mathematical model of the process of a series of impact actions of projectiles at different points of the element of the protective structure is constructed. The latter is a boundary value problem for a partial differential equation. Its peculiarity is that the external dynamic action is a discrete function of linear and time variables. To determine the dynamic effect of a series of impacts on the object under study, and thus the level of protection of the structure, the basic ideas of perturbation theory methods are extended to new classes of systems. This allowed to obtain an analytical dependence of the deformation of the elastically reinforced element on the basic physical and mechanical characteristics of the material of the protective element, its reinforcement and the characteristics of the external action of the projectiles. It is shown that the most dangerous cases, given the security of the structure, are those when the impact is repeated at equal intervals, in addition, the point of impact is closer to the middle of the protective element. The obtained theoretical results can be the basis for selection at the stage of designing the main physical and mechanical characteristics of the elements of engineering structures and their reinforcement in order to reliably protect personnel and equipment from the maximum possible impact on it of the shock series of projectiles. The reliability of the obtained results is confirmed by: a) generalization of widely tested methods to new classes of dynamical systems; b) obtaining in the limit case the consequences known in scientific sources concerning the linearly elastic characteristics of the elements of protective structures; c) their consistency with the essence of the physical process itself, which is considered in the work.

Influence of soil characteristics on working dynamics mining tral authority

The safest way to clear mines and barriers, in terms of saving human life and health, is to clear them at the site. Minesweepers are being used for this purpose, and in recent years they have gained extensive research, which is aimed at the use of large-scale explosion technology. Existing minesweepers in the Armed Forces of Ukraine, as a rule, are old-fashioned, and have certain shortcomings that affect the efficiency of their direct use. These include, first of all, insufficient survivability and different efficiency of their use during demining of minefields with different types of soils: from sandy, loamy and gravel. The range of physical and mechanical properties of the latter is very wide, and therefore - for the operation of an explosive device (mine) requires different amounts of action on the soil surface. The modernized mine trawl neutralizing device in the form of a system of U-shaped rockers with disks at the end is proposed in the work. They, acting directly on the mine, or through a small layer of soil, cause it to explode, provided that the force on the latter is not less than the minimum value required for its disposal. The advantage of this type of mine trawl is that even if one of the working disks fails during the explosion, it is structurally relatively easy to replace it with another. The magnitude of the deepening of the neutralizing disks into the soil (at a constant weight of the mounted part of the trawl), as well as their dynamic action through the soil on the mine depends on the physical and mechanical properties of the soil. Therefore, for the case of, for example, clay or sandy soils during the movement of the trawl, it will be sufficient for the operation of the explosive device, at the same time for the coating of gravel - insufficient. In addition, the amount of deepening of the working disks in the soil depends on its humidity.
 The study of the influence of the main physical and mechanical characteristics of soils on the dynamics of the modernized mine trawl neutralizing device during movement along the minefield (before and after the mine explosion) is the subject of research, hence their relevance.

Glass Foam Made with Silicon Nitride and Manganese Oxide by Microwave Irradiation

A high mechanical strength (6.1 MPa) glass foam was produced by sintering/foaming at 830 ºC in an experimental 0.8 kW-microwave oven. The basic raw material was a colorless flat glass waste and the foaming agent was Si3N4 powder (2 wt.%). As an oxygen supplying agent, a MnO2 powder (3.1 wt.%) was used. The main physical, mechanical, thermal and morphological characteristics of the optimal sample were: apparent density of 0.47 g/cm3, porosity of 77.6%, thermal conductivity of 0.105 W/m·K, compressive strength of 6.1 MPa and pore size between 0.15-0.40 mm. The optimal glass foam sample has the required characteristics of a thermal insulation material usable under mechanical stress conditions in civil engineering. The originality of the paper is the application of the unconventional microwave heating technique, faster and more economical, unlike the other papers in the same area published in the literature, followers of the traditional conventional heating technique.

An insight into the precipitate evolution and mechanical properties of a novel high-performance cast Al-Li-Cu-Mg-X alloy

High-performance cast Al-Li alloys are highly desirable for a wide range of weight-critical and stiffness-critical applications. This work was undertaken to investigate the microstructural evolution, coarsening kinetics of main precipitates and related mechanical characteristics of a newly-developed cast Al-Li-Cu-Mg-X alloy during aging at 150, 175, 200 and 225 °C. The as-aged alloys studied primarily comprised of δ′ (Al3Li), T1 (Al2CuLi), S′ (Al2CuMg) and core-shell Al3(Li, Sc, Zr) phases. δ′ phases exhibited the relatively lowest thermal stability. The increasing aging temperature led to the greatly enhanced coarsening rate of δ′. It was found that the coarsening of metastable δ′ was a diffusion-controlled process and a linear relationship of cube average particle radius (R̅3) against aging time t was revealed. The activation energy for the δ′ coarsening was estimated to be ~98.7 kJ/mol, which was somewhat lower than those in wrought Al-Li alloys. Besides, the activation energy for the growth of T1 plate was measured to be ~95.6 kJ/mol, which was close to that of grain boundary diffusion of Cu in α-Al (~105 kJ/mol), indicating that the growth of T1 should be governed by the diffusion rate of Cu toward T1 plates. With the successively increased aging temperature and prolonged aging time, the number density and volume fraction of δ′ particles were significantly reduced, primarily contributing to the significant strength reduction. The relatively best combination of strength and ductility was achieved in the studied alloy aged at 175 °C for 32 h.

EXPANSION OF APPLICATION OF AUSTENITE STEEL PRODUCTS IN THE FOOD INDUSTRY

The article considers the increase of machinability of austenitic steels by combining preliminary cold plastic deformation with the use of environmentally friendly lubricating and cooling fluids based on rapeseed oil. It is shown that by fusing plastic steels with a large amount of chromium, nickel and manganese, the Curie point can be reduced to room temperature. State diagrams of Fe - Mn and Fe - Cr - Ni systems after such transformations are considered. In the latter case, steels become suitable for products and technologies of the food industry, but they are difficult to process in mechanical technologies. The study of steels 12Х15G9ND (AISI 201) is given; 08X18H10 (AISI 304); 110G13L (A128). A mathematical model of the object of study was developed, where the process factors were cold plastic deformation (COD), lubricating and cooling fluid (MPC) and cutting speed. The optimization parameters were the shrinkage of the chips and the length of contact of the latter with the front surface of the tool. The equation of the mathematical model is given. A number of modern installations and methods of process research are described. Among the research methods, new ones are noted, in particular, methods of transverse compression, determination of the number of dislocations, spectral analysis, cutting of steels using MPAs of plant origin. The optimal brand of ecologically pure vegetable MPA is determined. It is rapeseed oil together with anti-emergency and anti-wear additives. The main physical and mechanical characteristics of cutting austenitic steels in the context of the impact of HPD together with MPA are presented: friction force, normal force, contact stress, contact pressure, contact length, coefficient of friction, angles of action and shear. It is shown that HPD with coolant reduces the cutting temperature by 30 - 50 ºC, and the components of the cutting forces by 30 – 50%. The effect of selected three main factors of the process on growth is studied. It is shown that the stress-strain state of the system "machined material - tool - chips" from the action of these factors approaches the specified state. That is, the intensity of growth decreases. The relationship between the main phenomena in the cutting of austenitic steels obtained in the study is presented. It is established that medium temperature tempering in a protective environment should be recommended to restore the initial performance properties of austenitic steels. The final finishing operation can be processing with an elastic tool made of superhard materials.

Identification of Analytical Dependencies of the Operational Characteristics of the Workpiece Clamping Mechanisms with the Rotary Movement of the Input Link

Abstract The research is devoted to the problem of determining the efficiency of the workpiece fixing mechanism operation. Improving characteristics of workpiece fixing is one of the required conditions to increase the cutting modes, which may help to enhance the machining productivity. The study investigates the main characteristics and general features of a new structure of clamping mechanisms with electromechanical actuators for fixation of rotation bodies. The main advantages of using electromechanical clamping actuators with self-braking gear are presented. Two simplified dynamical models for the description of different stages of the clamping process are developed. The calculation scheme was formulated to find out how the mass-geometric parameters of mechanism elements should influence the main characteristics of the clamping mechanisms of this type.