bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of yoghurt from fresh cow milk fortified with mango (Mangifera indica L.) pulp in Northern Nigeria
Authors: Achi N.P. , Achi J.N. , Mallam I.
Published: October 2024

Abstract. This study was conducted to evaluate the physicochemical properties, antioxidant content and the sensory attributes of fresh cow milk yoghurt fortified with mango pulp. Yoghurt samples were prepared from different proportions of yoghurt and mango pulp as follows: 100:0 (Control), 90:10 (10% MPY), 86:14 (14% MPY), 82:18 (18% MPY), 78: 22 (22% MPY) with sugar level maintained at 5 % (by weight) and was evaluated for physicochemical, antioxidant content and the sensory attributes of yoghurt from fresh cow milk fortified with mango pulp (MPY). The data collected for physicochemical, antioxidant content and the sensory attributes of the yoghurt were analyzed using the Statistical Package for Social Sciences (SPSS, 2016) version 16.0. The result for proximate composition of the yoghurt samples showed significant increase in total solids, ash and titratable acidity and was reported highest in 22% MPY while the pH, protein and fat content decreased with the increase in mango pulp concentration across the treatment combinations. The antioxidant capacity measured in the study was vitamin C, phenols and tannins. The vitamin C content significantly increased with addition of mango pulp recorded highest in 22% MPY ((4.97) while phenols and tannins decreased with increase in mango pulp concentration and reported highest in control yoghurt. The organoleptic results revealed more consumer acceptance for control yoghurt over the other treatments combinations and found higher in all the sensory parameters; aroma, appearance, texture and general acceptability except for the taste which reported highest in 14% MPY (3.80) and lowest in 10% MPY (2.80). In the case of physicochemical composition of the yoghurt samples, fat and protein content decreased with increase in mango pulp concentration to the yoghurt while the total solids, ash and titratable acidity increased. For enhancement of minerals, vitamins and antioxidant capacity of yoghurt drink, acceptable quality can be produced by blending yoghurt with 22% mango pulp combination there by promoting the health benefit of consumers.
Profitability of dairy goat farms in Bulgaria
Authors: Slavova S.
Published: October 2024

Abstract. The purpose of the present study was to establish the economic performance of dairy goat farms in Bulgaria by using the indicator profitability and the related indicators – total production, total revenues, total costs and profit per doe (before and after subsidy). Data for 2022 were provided by the owners of 8 farms within the survey and processed using a mathematical-statistical model and Excel program. The adopted production system was semi-intensive with indoor winter period and grazing (supplemented with cereals and hay) during most of the year. Profit before subsidies was found positive only for farm 5, and all other holdings were unprofitable based on the results of their own production. When subsidies were added, some of them reported a positive financial result, while others remained loss-making. Based on the results found within the study, it could be summarized that in the dairy sector the level of milk production is the leading factor for farm income. Оf great importance are also the sale of value-added dairy products, own feed production and optimization of labour costs. In most farms, subsidies (incl. for pastures) are extremely important for the viability of the farms. In addition, when analyzing the economic efficiency of dairy goats, an individual approach to farms is necessary. All elements of the production system, both biological and economic, should be taken into account in order to improve production and profits.
Influence of salting method on the chemical composition, yield, texture and sensory properties of Škripavac cheese
Authors: Ivaniš Matea , Tudor Kalit Milna , Rako Ante , Bendelja Ljoljić Darija , Kos Ivica , Dolenčić Špehar Iva , Kalit Samir
Published: October 2024

Lički Škripavac is a traditional Croatian cheese characterised by its soft and rubbery texture and the squeaky sound attained during chewing. Traditionally, it can be produced using two different salting methods: dry salting of curd grains and salting of milk before coagulation. The aim of this study was to determine the effects of the salting method on the chemical composition, yield, texture and sensory properties of Škripavac cheese. Five batches of Škripavac cheese were produced from 40 L of raw cow milk. Milk was divided into two equal parts and cheeses were produced applying the above-mentioned salting methods. Cheeses produced from milk salted before coagulation had significantly (p<0.05) higher water content, significantly (p<0.01) lower protein content and significantly (p<0.01) higher pH value compared to cheeses with salted curd grains. Also, these cheeses had a higher milk fat recovery (p<0.05) and a higher actual (p<0.0001) and adjusted yield (p<0.01). In terms of textural properties, the cheeses that were produced by adding salt to the curd grains were significantly (p<0.05) harder, less crumbly and less elastic than those produced by salting the milk. The method of salting had no significant effect on sensory characteristics of the Škripavac cheese.
Primjena izolata proteina pšeničnih mekinja kao suplementa u proizvodnji visoko proteinskih jogurta
Authors: Slavíková Zuzana , Smatana Igor , Diviš Pavel , Smilek Jiří , Slaninová Eva , Pořízka Jaromír
Published: October 2024

Yoghurts with increased protein content are becoming very popular and beneficial across all age groups. The economic growth of the high-protein yoghurt market contributes to the production and research of various alternatives for these products. In this study, plain yoghurt was fortified with 2 % and 5 % wheat bran protein isolate (WBPI) before fermentation. The influence of the addition of WBPI on nutritional and rheological characteristics, bacteria growth, and sensory properties of yoghurt samples was evaluated. Apart from the nutritional benefits of wheat bran proteins, which have a favourable amino acid profile, fortification also resulted in changes in the rheological properties of the yoghurts. The increase in dry matter led to an increase in water holding capacity and, consequently, the viscosity of the yoghurt samples. The presence of WBPI did not affect bacterial growth or the fermentation process. However, the natural bitter taste of WBPI persisted even after the fermentation process, negatively influencing the sensory acceptability of WBPI-fortified yoghurt samples.
ANALYSIS OF WASTEWATER QUALITY AND PERFORMANCE EFFECTIVENESS OF WASTEWATER TREATMENT PLANT ON VANAME SHRIMP (Litopenaeus vannamei) CULTURE IN BPIU2K KARANGASEM
Authors: Sumaryati Ni Putu , Sri Ayuni Ni Putu , Agung Suryaputra I Gusti Ngurah
Published: October 2024

Vaname shrimp (Litopenaeus vannamei) culture in BPIU2K Karangasem will produce waste from metabolism and leftover feed that contains organic material. This waste will cause environmental problems if not properly processed. This study aims to determine the quality of wastewater and the effectiveness of WWTP performance so that it can be used to generate policy recommendations for improvements in wastewater management. Water samples are taken in the morning using composite technique at five points in the IPAB inlet and outlet, each consisting of 1 liter with three repetitions.The results showed water quality of WWTP outlet from first week to third week have reached quality standard for physical parameters such as TSS and turbidity, and chemical parameters such as BOD and nitrate. However, did not reach quality standard for chemical parameters such as phosphate, H2S, nitrite, and ammonia. Removal efficiency in processing units can be used to determine the effectiveness of WWTP and will be effective if efficiency value is in the range of 60% < x = 80%. First week, WWTP in BPIU2K Karangasem showed its effectiveness on several parameters such as BOD and nitrate. Second week, the effectiveness was shown for BOD, phosphate, nitrate and ammonia. Third week, the effectiveness was shown for TSS, BOD, phosphate and H2S. The effectiveness of WWTP for each parameter differs every week due to the cultivation waste water coming from various activity units and the IPAB is still effective in treating wastewater because the five tested parameters still meet the quality standard.
Mruziya
Authors: Perry Charles
Published: October 2024

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Peter Brears: Ryedale Recipes
Authors: Davidson Alan E
Published: October 2024

Peter Brears: Ryedale Recipes: Hutton-le-Hole and Beverley, Yorkshire: Ryedale Folk Museum and Hutton Press, 1998: ISBN 1 872167 96 9: 80 pp,  b/w illustrations and photographs, notes, index of recipes, large format plb, £5.95.
Lynda Brown: The Shopper's Guide to Organic Food
Authors: Hourani Furugh
Published: October 2024

Lynda Brown: The Shopper's Guide to Organic Food: London, Fourth Estate, 1998: ISBN 1 85702 840-6: 370 pp, numerous useful lists, index, plb, £7.99.
Jeffrey M Pilcher: Que vi van los tamales: Food and the Making of Mexican Identity
Authors: Davidson Alan E
Published: October 2024

Jeffrey M Pilcher: Que vi van los tamales: Food and the Making of Mexican Identity: Albuquerque, University of New Mexico Press, 1998: ISBN 1 8263 1873 8: 155 pp, notes, glossary, bibliography, index, plb, $16.95.
CALCULATION OF THE TOOL SHAPE FOR TUBE MIDDLE PART DISTRIBUTION BY RIGID MATRIX
Authors: Bormotin K. S. , Potianikhin D. A , Hlaing Min Ko , Sinelshchikov A. A.
Published: October 2024

In modern mechanical engineering in general, and in the aircraft industry in particu-lar, a large number of parts are obtained by sheet stamping. For the manufacture of ele-ments of hydro-gas systems of aircraft, shaping operations are often used, in which liq-uids and rubber-like materials serve as a working medium that transfers the pressing force to a deformable workpiece. In this paper, we consider the process of expanding the middle part of a tubular billet made of titanium alloy OT4-1. The internal pressure on the tubular billet is determined by the action of the working fluid during compression. One of the significant disadvantages of cold sheet forming is the springback of the material after being removed from the tool-ing. Therefore, the shape of the die used for the technological process of expansion must set the proactive shape of the tubular billet, providing the desired residual shape after unloading. To determine such a matrix form, an inverse problem is formulated and solved. The implementation of the method for solving the inverse problem is carried out in the MSC.Marc system. For the axisymmetric shape of the part, a two-dimensional state-ment of the problem is used. In the case of thin-walled structures, the modeling of the shaping process is carried out under plasticity conditions, taking into account small deformations, but large displacements and rotations (general Lagrangian formulation). The solution of the inverse contact problem of shaping is found by the iterative method, which is based on the quasi-static variational principle. This solution algorithm is gener-alized to three-dimensional problems, when the part has a non-axisymmetric shape, in particular, ellipsoidal, tee, etc. As a result of solving the inverse contact problem of shaping a tubular workpiece by the iterative method, the required geometry of the rigid matrix was determined. Compari-son of the numerical results with the conducted full-scale experiment showed a satisfac-tory agreement. Thus, the presented method and its implementation in the CAE system makes it possible to design tooling at the pre-production stage.
DISPERSIONAL DEPENDENCES AND PECULIARITIES OF ENERGY TRANSFER BY FLEXIBLE WAVES IN A BEAM LYING ON A GENERALIZED ELASTIC BASE
Authors: Erofeev V. I. , Lenin A. O. , Lisenkova E. E. , Tsarev I. S.
Published: October 2024

The dynamics of a Bernoulli – Euler beam lying on an elastic foundation is consid-ered. A generalized model of an elastic foundation is selected, which includes two inde-pendent bedding coefficients: the stiffness of the foundation for tensile-compression deformation and for shear deformation. Unlike the classical elastic foundation model (Winkler's model), the generalized model takes into account the distribution capacity of the soil, i.e. its property to settle not only under the loaded area, under the foundation, but also near it. The beam is considered to be infinite. Such idealization is permissible if optimal damping devices are located on its boundaries, that is, the parameters of the boundary fixation are such that the perturbations falling on it will not be reflected. This makes it possible to consider the beam model without taking into account the boundary conditions, and consider vibrations propagating along the beam as traveling bending waves. The influence of a two-constant elastic foundation on the parameters of a bending wave propagating in a beam is studied. It is shown that with an increase in the shear stiffness of the elastic base, waves with the same wavenumber (i.e., waves of the same length) will have a higher frequency, higher phase and group velocities. For the system under consideration, the energy transfer equation is written in divergent form. It is shown that the average rate of energy transfer is equal to the group velocity of the flexural wave. The equality of these velocities serves as an additional factor indicating the internal physical consistency of the model of bending vibrations of a beam lying on a general-ized elastic foundation.
MACHINE LEARNING METHOD IN ELASTIC PLATE TOPOLOGY OPTIMIZATION PROBLEMS
Authors: Avdonyushkin D. V. , Matveeva A. I. , Novokshenov A. D.
Published: October 2024

In this article, as an alternative to traditional methods of topology optimization of deformable solids, an approach to topology optimization based on machine learning methods is proposed. The proposed approach significantly reduces the time spent on obtaining the optimal solution and allows to avoid the use of time-consuming finite element calculations at the stage of obtaining the optimal solution. All of time-consuming calculations are performed at the network training stage. A review of the world literature on the application of machine learning methods in the problem of topology optimization of an elastic deformable solid is given. Further, as an example, a square elastic plate is considered, fixed on one side and loaded with a force on the other. For a given plate, a series of topology optimization problems (maximizing stiffness under volume constraints) are solved using the method of moving asymptotes to build a training data set. A comparative study of a neural network with one custom nonlinear layer, based on the nature of the optimal topology, and a three-layer neural network built using the standard PyTorch library features is carried out. The input parameter of the neural network is the force application point, the output parameter is the optimal topology of the plate. The network is trained using the backpropagation method. The quadratic norm of the predicted design variable values deviations compared to the true values form last optimization is minimized during neural network learning. The considered example shows the possibility of applying the approach to other problems that differ in geometry, boundary conditions, etc. The results and unsolved problems of the method are also discussed.
BASE NEUTRAL SURFASE SELECTION FOR OPTIMAL DESIGN OF STRUCTURALLY-ANISOTROPIC AIRCRAFT PANELS MADE FROM COMPOSITE MATERIALS WITH REFINED BUCKLING THEORY RESTRICTIONS
Authors: Gavva L. M. , Mitrofanov O. V. , Firsanov V. V.
Published: October 2024

The aim of this study is the approach to the optimal design of structurally-anisotropic aircraft bearing surface panels with the restrictions according to the refined buckling theory for the optimal size-weight design implementation. The panels are subjected to the distributed constant compressive loading applied to the edges in the skin plane in the longitudinal direction. The panel contour boundary conditions are assumed to be the particular case with conformable boundary restrictions for the plane problem and problem of bending. The optimal design problem statement and analytical solution are formulated to determine the geometry parameters of a flat rectangular multilayer panel made from composite materials with the eccentric longitudinal and lateral stiffening set being of minimal mass. The equal-buckling condition is the optimal design base. The general bending mode of buckling and multi-wave torsion mode of buckling must have the same occurrence probability while the buckling margin tends to one. The optimal design problem is reduced to the mathematic conditional extremum investigation of the goal weight function with multiple variables using the analytical and numerical methods. New mathematic model relations for the buckling problem investigation of structurally-anisotropic composite panels are presented. The primary scientific novelty of this research is the further development of the thin-walled elastic rib theory related to the contact problem for the skin and rib with an improved rib model. The analytical solution is reduced to determine the displacements of a base neutral surface that may be select arbitrarily. The schematization of the panel as structurally-anisotropic one has been proposed as a design model when the critical forces of total bending mode of buckling are determined. For a multi-wave torsion buckling study, one should use the generalized function techniques for the discrete stringer stiffness. The solution of the strained surface differential equation of an eighth order is designed by a trigonometric series in the closed form. The results of the optimal design with the refined buckling restrictions based on refined buckling analysis calculations offer opportunities to reduce and optimize the weight characteristics of aircraft elements.
MODELING OF THE INITIATION CONDITIONS OF CRACKS IN A PIPE UNDER PRESSURE OF A HYDROGENOUS MEDIUM
Authors: Zinovieva T. V.
Published: October 2024

An actual problem of modern engineering about destruction of a pipeline as a result of influence of hydrogen contained in the transported products is considered. Hydrogen changes the mechanical properties of metal, affecting the stress-strain state of the pipe, which, in turn, affects the distribution of hydrogen in the pipe. The hypotheses about the nature of this relationship accepted in the paper allowed to explain the reason of circum-ferential crack formation in the pipe under the influence of hydrogen. An algorithm for iterative calculation of the stress-strain state of a tube containing a hydrogen-containing mixture inside the tube has been developed. The coupled problem of the theory of elasticity and diffusion in the planar axisymmetric formulation is solved. Since the interaction process of hydrogen and metal is very slow, it is considered in sequential static formulations. First, the Lame-type problem for a tube with the modulus of elasticity depending on the radial coordinate is solved. By the finite difference method the stress and strain fields of the pressurized pipe are found. Further, the concentration of free hydrogen in the pipe caused by its content on the pipe surfaces and its stress state is determined. The accepted hypothesis about the condition of hydrogen atoms embedding into the crystal lattice of metal allows to estimate the influence of hydrogen on mechanical properties of the pipe material at the next stage of the calculation. The calculation of stress and concentration fields is repeated again with already modified mechanical properties. The iteration process is stopped when the stresses in the tube reach critical values according to Mises criterion or when the mechanical properties of the pipe mate-rial stop changing. The calculations show that at some combination of hydrogen concentration and pressure on the pipe wall, zones of plastic deformation arise in the pipe, which can lead to delamination of the material in the circumferential direction. This result is consistent with known experimental data.
NATURAL VIBRATIONS AND HYDROELASTIC STABILITY OF A PLATE WITH A PIEZOELECTRIC ELEMENT CONNECTED TO AN EXTERNAL RL-CIRCUIT
Authors: Lekomtsev S. V. , Matveenko V. P. , Senin A. N.
Published: October 2024

The possibility of passive damping of harmonic vibrations and controlling the stabil-ity boundary of the plate interacting with the flowing fluid is investigated. The key idea behind the applied vibration control method is to connect the piezoelectric element lo-cated on the surface of the structure to an external shunt circuit. The selection of parame-ters for such circuit, providing the highest rate of vibration damping or the maximum change in the critical velocity of the fluid flow, is performed by solving a series of eigen-value problems. Two mathematical formulations are considered. The first formulation is based on the three-dimensional equations of the linear theory of piezoelasticity, and the second one is a simplification of these equations with the aim of using them in conjunc-tion with the theory of thin plates. The dynamics of an ideal fluid in both cases is de-scribed by a wave equation formulated for the perturbation velocity potential. Together with the impermeability condition and the boundary conditions it is transformed to the weak form. The hydrodynamic pressure is calculated by the linearized Bernoulli formula. The developed finite-element algorithms are verified and their computational efficiency is compared. A change in the complex eigenvalues of the electromechanical system is ana-lyzed depending on the resistance and inductance of the electric circuit connected to the piezoelectric element. The values of these parameters providing the best damping of resonant vibrations of a rectangular plate interacting with the flowing liquid have been selected based on the solution of the optimization problem. The numerical studies have shown that the selected values lead to a smaller change in the frequency spectrum of the original system and provide a higher rate of vibration damping as compared to the val-ues found by the known analytical expressions. The numerical investigation has been performed for two variants of boundary conditions set at the edges of the structure. It is demonstrated that the use of a passive electrical circuit cannot affect the loss of stability by divergence, but is able to change the critical flutter velocity by a few percent
NUMERICAL AND EXPERIMENTAL STUDY ON CFRP STRUCTURE OPTIMIZATION FOR COEFFICIENT OF THERMAL EXPANSION
Authors: Pasechnik K. A. , Obvertkin I. V. , Vlasov A. Y.
Published: October 2024

This paper explores the optimization macrostructure to reach a stable low coefficient of thermal expansion αx of a composite with carbon fibers. To limit the search area, a necessary condition for the existence of αx local minima is proposed, expressed in terms of the radii of hyperspheres in the design space of the angular orientation of the layers transformed by the PСA algorithm. The analysis of the structure variants characterized by low αx shows different sustainability to lamina properties variability. Multi-criteria optimization was carried out. The objective functions are expectation E(αx) and variance Var(αx). The analysis of Pareto fronts and probability density functions make it possible to estimate the reachability of the calculated αx under given conditions of lamina properties variability. The reduction variance opportunity of αx distribution by modifying the polymer matrix with MWCNTs under conditions of reinforcing fibers disorientation and lamina properties variability is investigated. The microstructure modification of the polymer composite material allows to reduce the Var(αx) by 91.61 % with a volume ratio of MWCNTs up to 1 %. Requirement thermomechanical properties are reached by determining the orientation of anisotropic layers. Based on the obtained optimal structures, specimens of CFRP with 0, 1 and 2 vol.% MWCNTs were made. Scanning electron microscopy using FE–SEM Hitachi S–5500 was performed to check the uniformity of distribution and compatibility of the epoxy matrix and MWCNTs. The measurement of αx is determined using a TAInstrumentsQ400 thermomechanical analyzer. Measured αx of specimens is in the range from 6.2·10-8 to 1.98·10-7 1/K. The structure optimization approach proposed in this paper makes it possible to obtain a set of solutions with a consistently low αx in the range up to 1·10-7 1/K. The transformation of the design space of the layers’ orientation angles and the limitation of the search area allowed to reduce the range of solutions under consideration by 83.9 %.
MODELING OF AXIAL COMPRESSION OF V95/10% SIC ALUMINUM MATRIX COMPOSITE UNDER NON-STATIONARY THERMOMECHANICAL CONDITIONS
Authors: Kryuchkov D. I. , Nesterenko A. V. , Zalazinsky A. G.
Published: October 2024

Intensive deformation is necessary to obtain products made of aluminum-matrix composite materials (AMCM) with the required level of mechanical properties. To model the deformation behavior in non-stationary conditions of the thermo-deformation treatment, the identification of the AMCM model remains an urgent task. The use of the Johnson-Cook plasticity model is one of the approaches to describing the material fluidity. This paper aims at studying an AMCM made of granulated high-strength aluminum alloy V95 of the Al–Zn–Mg–Cu system, reinforced with SiC particles 10 % by weight. We investigate how non-stationary thermomechanical (pressure on the workpiece and heating temperature) deformation conditions influence the true deformation and deformation rate of the composite material, as well as identify the material model and verify its application to study the shape changes under certain pressure and temperature ranges. The precipitation process is studied under uniaxial compression of the sintered cylindrical samples of AMCM in the range of the initial pressures of 5.65–7.81 MPa when heated to 510, 530 and 550 °C. In this range, the dependences of the degree of deformation and the average deformation rate for the process are obtained. Identification of the rheological model of the material was carried out. A mode of the preliminary thermomechanical processing is proposed and a prototype is manufactured at an initial pressure of 6.7 MPa on the workpiece and heated to 550 °C in 84 minutes. The above mode provided a relatively uniform filling of the stamp cavities with the composite material. To confirm the possibility of applying the results of the parametric identification of the material model, we simulated the prototype manufacturing process.
EXPERIMENTAL AND THEORETICAL INVESTIGATIONS OF STRUCTURAL MECHANISMS AND PLASTIC STRAIN LOCALIZATION EFFECTS IN ALMG6 ALLOY UNDER DYNAMIC LOADING
Authors: Sokovikov M. A , Simonov M. Yu , Chudinov V. V , Uvarov S. V , Oborin V. A , Naimark O. B
Published: October 2024

This paper is concerned with substantiating one of the mechanisms of plastic strain localization under high rate loading associated with structural transitions in the defect structure of materials. For this purpose, a series of experiments were carried out to study the localization of plastic strain in skewed specimens of the AMg6 alloy subjected to loading in a split Hopkinson pressure bar. The temperature fields generated during the plastic deformation tests designed to identify the characteristic stages of strain localization were investigated "in-situ" using a high-speed infrared camera CEDIP Silver 450M. The values of temperatures in the strain localization zone indicate that in the AMg6 alloy under the implemented loading conditions the mechanism of strain localization caused by thermoplastic instability is not realized. Structure analysis of dynamically loaded specimens was carried out using the Olympus GX- 51 optical microscope and FEI PHENOM G2 ProX scanning electron microscope. It supports the structure-dependent regularities of the strain localization mechanism under dynamic loading. The experimental results of dynamic loading with a subsequent investigation of the temperature fields, the structural studies with an optical and electron microscope, as well as the data of the numerical modeling considering the kinetics of the mesodefect accumulation in the material suggest that one of the mechanisms of plastic strain localization in the AMg6 alloy under realized loading conditions is caused by structural transitions in the defect structure of the material.
APPLICATION OF THE FINITE ELEMENT METHOD IN COMBINATION WITH THE CONTACT LAYER METHOD TO DETERMINE THE STRESS-STRAIN STATE OF MULTILAYER BEAMS
Authors: Chepurnenko A. S , Turina V. S
Published: October 2024

The purpose of this article is to develop a method for calculating multilayer beams using the finite element method in combination with the contact layer method. The contact layer is an elastic anisotropic medium, consisting of rigid short bars, working only in tension-compression in the vertical direction and shear. The contact layers model the connections through which the layers of multilayer beams interact. To determine the stress-strain state of the beam, it is represented as a set of beam finite elements (FE) of each layer connected by finite elements of contact layers. As beam elements, modified FEs are used, in which horizontal displacements along the upper and lower edges, as well as deflection, act as degrees of freedom in the node. An example of the calculation of a three-layer beam hinged at the ends under the action of a uniformly distributed load is presented. The outer layers of the beam are made of carbon fiber, and the middle layer is made of the syntactic one based on glass spheres. The calculation is performed with and without taking into account the deformations of the transverse shear of the layers. The meshing of the beam along the length into finite elements is assumed to be non-uniform with a thickening in the near-support zone in order to be able to catch the edge effects. The solution is implemented in the MATLAB environment. As a result of the calculation, it was found that there is a range of change in which the stiffness of the contact layers does not have a noticeable effect on the deflections of the structure. For the considered example, a significant difference was revealed in the values of maximum displacements, as well as in the character of the diagrams of bending moments and shear forces in the outer layers when calculating with and without taking into account transverse shear deformations. At the same time, transverse shear deformations do not have a noticeable effect on the stresses in the contact layers.
GRADIENT MODELS OF DEFORMATION OF COMPOSITE ELECTROELASTIC BODIES
Authors: Vatulyan А. О. , Nesterov S. А.
Published: October 2024

The stress-strain state of layered electroelastic bodies is studied taking into account largescale effects. To account for the scale effects, a gradient model of electroelasticity with one mechanical and one electrostatic parameters is used. As examples, the problem of deformation of a composite electroelastic rod, the antiplane problem of deformation of an electroelastic strip with a coating, the problem of deformation of a solid piezocylinder with a coating are considered. On the basis of the variational principle of gradient electroelasticity, refined equations of equilibrium and electrostatics are obtained, as well as an expanded list of boundary conditions and interface conditions for the tasks set. Several simplified formulations of gradient electroelasticity problems for composite bodies are considered, when only one of the gradient effects, mechanical or electrostatic, is taken into account. The dimensionalization was carried out and analytical solutions of simplified problems were obtained. Calculations of displacements and stresses of composite electroelastic bodies are carried out on specific examples. Solutions of problems in classical and gradient formulations are graphically presented; a comparative analysis of the solutions obtained is carried out. It is found out that if the scale parameters are taken into account in the vicinity of the conjugation of layers, the following is observed: 1) a smoother distribution of displacements and electric potential compared to classical theory; 2) a jump of components of the Cauchy stress tensor and components of the electric induction vector; 3) a continuity of some components of the moment stress tensor and quadrupole moment; 4) a continuity of total stresses. The jump of the components of the Cauchy stress tensor and the components of the electric induction vector is explained by the continuity of the displacements, the electric potential and their first derivatives. The dependence of displacements and electric potential on the magnitude of mechanical and electrostatic scale parameters is investigated. It was found out that with an increase in the scale parameters both the displacement and electric potential decrease.
VARIATIONAL FORMULATION OF GRADIENT IRREVERSIBLE THERMODYNAMICS
Authors: Belov P. A. , Lurie S. A.
Published: October 2024

This work proposes the elaboration of the variational principle of L.I. Sedov for modeling dissipative processes. The formulated variational principle makes it possible to propose the dissipative models using the known model of a reversible process (the known Lagrangian), adding the required number of dissipation channels. Dissipation channels are non-integrable variational forms that are linear in the variations of the ar-guments. The arguments of the dissipation channels are the generalized variables of the corresponding bilinear terms of the Lagrangian. Variational models of heat transfer pro-cesses are considered as examples. The paper introduces the thermal potential, which is taken as the main kinematic variable. The temperature and heat flux are determined from the expression of the possible work done on variations of the first derivatives of the thermal potential, by analogy with continuum mechanics, where internal forces do the possible work on the strain variations. The equations of heat conduction laws of the considered heat transfer models are obtained as compatibility equations by eliminating the thermal potential from the equations of constitutive relations for temperature and heat flow. It is shown that the proposed procedure for elaboration of the dissipative models makes it possible to obtain the laws of thermal conductivity of Fourier, Maxwell – Catta-neo, Gaer – Krumhaksl, Jeffrey and more general laws of thermal conductivity. For the simplest heat transfer model, a single dissipation channel was introduced, which made it possible to obtain a heat transfer equation containing the second and first time deriva-tives. This model takes into account the wave properties and dissipation by the diffusion mechanism. In a particular case, it is reduced to the classical model of heat conduction. For more general gradient models of heat transfer, additional dissipation channels are sequentially introduced. In accordance with the differential order of the heat balance equation, the variational method makes it possible to formulate a consistent spectrum of boundary conditions at each non-singular point of the surface. In addition, for a bounda-ry value problem in time, the variational principle determines pairs of alternative condi-tions at the initial and final times of the process under consideration.
DEFORMATION OF A THIN FILM AFTER CONTACT LOSS WITH A CYLINDRICAL BASE AXIAL DELAMINATION
Authors: Ustinov K. B. , Gandilyan D. V.
Published: October 2024

The paper deals with the problem of a coating section delaminated from a cylindrical base due to compressive stresses. It has been studied using the theory of cylindrical shells with boundary conditions of the type of generalized elastic clumping. We obtained distributions of the components of the coating displacements and the energy release rate for the delamination growth along the rectilinear and curvilinear boundaries. We compared the values of the energy release rate and components of the dis-placement calculated with and without the influence of transverse forces. The depend-ences of the energy release rate, mode I of the stress intensity factor, the angle of rota-tion at the clamping point, and the coating displacement components on the relative compliance of the substrate and its curvature have been studied. It is shown that with an increase in the compliance of the substrate, the magnitude of the delamination buckling and the energy release rate increase significantly. The positive curvature also leads to an increase in the energy release rate. Several reasons have been identified, according to which the delamination stops developing along its rectilinear boundary and the tunneling effect occurs. It is shown that for sufficiently compliant substrates there is a certain critical width of a delamination, at which the development in the axial direction becomes ener-getically more favorable. Besides, it follows from the presented data, that positive curva-ture and an increase in the compliance of the substrate lead to a decrease in this critical width. According to the analysis of the results for the angle of rotation at the clamping point and the separation mode of the stress intensity factor, the observed effect of tunnel-ing can be caused not only by the difference in the energy release rates during the prop-agation of delamination due to expansion and elongation (tunneling), but also by the prohibition of overlapping of the coating and substrate faces
ENERGY CONDITIONS DETERMINING SIZE RANGE IMPACTING FORMATION OF MAGNESIUM HYDRIDE
Authors: Aptukov V. N. , Skryabina N. E. , Fruchart D.
Published: October 2024

Hydrogen, one of the most abundant elements in nature, is potentially suitable to produce, store and consume clean energy, namely for various industrial uses. The safest technique for hydrogen storage is metal hydride, e.g. as MgH2, with safe facilities to store and transport. A critical indicator of a metal-hydrogen system is the kinetic of hydrogen sorption, which is known particularly low for magnesium. However, under given thermodynamic conditions, the kinetics of magnesium/hydrogen reaction is especially sensitive to the particle size i.e. specific surface, crystallite/grain size i.e. boundary extension and nature of potential additives as catalysts. The present calculations aimed at determining the occurrence of hydride nucleation are based on a new energy ratio, as proposed at first time, which takes into account both physicschemical and mechanical factors. The calculations of the energy ratio are based on the minimum total energy of the system, which correctly reflects the processes occurring during hydride formation in magnesium. The critical size of a nucleus at the phase formation (hydride) in magnesium is controlled by the ratio of the volume and surface area of the emerging component, similarly to a crystallization process from a solution. The influence of the mechanical response of the system to the formation of hydride allows one to propose an interpretation of some phenomena regularly recorded during such experiments, i.e. the influence of special additives and mechanical texture, which lead to the acceleration of hydride formation. The results obtained suggest a mechanism favoring oriented nucleation of the hydride in a textured magnesium matrix thanks to the anisotropy of the elastic characteristics of the newly formed phase.
METHOD OF ESTIMATING PLASTIC DEFORMATION DISTRIBUTIONS AT THE FATIGUE CRACK TIP BASED ON THE SOLUTION OF LINEAR ELASTICITY THEORY
Authors: Vshivkov A. N. , Iziumova A. Yu. , Panteleev I. A. , Plekhov O. A.
Published: October 2024

In this paper, an experimental study of the strain fields at the fatigue crack tip was carried out. The strain fields were measured by an optical camera based on the digital image using the correlation method. Images were recorded using a Basler acA2440-75uc optical camera with a TC23007 OptoEngineering lens to achieve a spatial resolution of at least 3 μm. Recording frequency was 100 Hz. The possibility of using the solution of the linear singularity problem of elasticity theory to estimate the distribution of plastic strain at the fatigue crack tip was shown. Mechanical tests of uniaxial cyclic deformation with simultaneous registration of the strain field at the crack tip of different lengths were carried out on flat specimens of titanium alloys Ti Grade 2, Ti-1.1Al- 0.9Mn, Ti Grade 9. The specimens were loosened by means of a lateral semicircular notch in order to localize the crack. The solution of the problem of a specimen with a notch in the elastic formulation was carried out numerically in the finite element modelling package Comsol Myltiphysics. The peculiarity of the work is the use of the hypothesis of the functional relationship between real deformations and the elastic solution and the value of the secant modulus of the material to estimate the plastic deformation at the crack tip. The size of the zone of intense plastic deformations at the fatigue crack tip for different crack lengths was determined experimentally and numerically. By comparing the calculated and experimental data we showed the possibility of using the proposed dependence to estimate the distribution of the plastic strain field at the crack tip. The results obtained allow the analysis of the irreversible strain fields at the crack tip for mixed mode loading.
METHOD FOR CALCULATING SPHERICAL DOMES FOR STRENGTH AND BUCKLING
Authors: Karpov V. V. , Semenov A. A.
Published: October 2024

The paper considers new applications of the models, algorithms, software and methods developed by the authors to study shell structures of spherical shells (domes). For this type of structures, a method has been proposed to bypass the singularity at the top of the dome by choosing modified approximating functions. The mathematical model is geometrically nonlinear; it takes into account transverse shears, and is presented as a functional of the total potential strain energy. To reduce the variational problem to solving a system of algebraic equations, the Ritz method was used. The resulting system is solved by the method of continuing the solution using the best parameter with an adaptive mesh selection. The algorithm is implemented in the Maple analytical computing environment. A steel dome was estimated using different methods of border fixing, the values of the critical buckling load and the limit stress load were obtained. A graph of the load – deflection relationship and the deflection fields in the subcritical and supercritical stages were constructed. Fields are shown in the local and global Cartesian coordinate systems. The convergence of the Ritz method in terms of the critical load value is demonstrated. The methodology was verified by comparing the solution to the test problem with the known solution obtained by E.I. Grigolyuk and E.A. Lopanitsyn. The comparison results demonstrate the reliability of the data obtained. It was revealed that for the dome under consideration, the loss of strength occurs much earlier than the buckling, and therefore it can be recommended to select a steel grade with a higher yield strength for its design. A simply support border condition in this case gives a higher value of the maximum permissible load.
NUMERICAL SIMULATION OF THE INTERACTION BETWEEN A WAVE IN HYDROGEN AND A BARRIER IN A MODEL CHANNEL
Authors: Seregina M. A. , Babushkina A. V. , Modorskii V. Ya. , Cherepanov I. E. , Mikryukov A. O.
Published: October 2024

The paper considers the influence of physical and mechanical characteristics (PMC) of materials of the constructions to propagate acoustic waves in gas at a model channel. The research of the influence of PMC materials, pipelines, in particular, on the propagation of wave processes is associated with the problem of noise that arises during the transportation of natural gas and hydrogen- containing mixtures. The problem of noise is especially relevant given the forecasts for the development of the hydrogen energy transportation and storage industry. Modeling of acoustic processes is often associated with the sources of occurrence and propagation in the simulated environment. In this case, the possible occurrence of the resonance phenomena or processes of attenuation of acoustic waves in the dynamic gas-structure system are not taken into account. The boundary value problem is formulated in a bidirectional interaction statement (2-way Fluid-Structure Interaction or 2FSI) between the deformable structure and the hydrogen flow. Predicting the behavior of the pipeline structure in a model representation under the influence of gas during transportation will make it possible to select the optimal PMC material to reduce the acoustic impact both inside and outside the channel. The research presented in this work is carried out using the ANSYS engineering analysis system, which allows modeling the processes under consideration in the 2FSI statement. The paper analyzes the behavior of a wave generated by a unimodal sound source interacting with a barrier clamped in a rectangular pipe. The main results of the research are presented in the form of dependencies of the pressure amplitude versus time at characteristic points; the dependence of displacement versus time of the model barriers made of different PMC materials; the dependencies of changes in pressure and displacement for different working fluids.
INFLUENCE OF VARIABLE YOUNG’S MODULUS ON RESIDUAL STRESSES INDUCED BY ROTATIONAL AUTOFRETTAGE OF A TUBE WITH FIXED ENDS
Authors: Prokudin A. N.
Published: October 2024

Autofrettage processes are designed to strengthen hollow cylindrical and spherical parts and usually consist of one load-unload cycle. At the first stage, the workpiece is loaded to cause either partial or complete plastic deformations. During unloading, residual compressive stresses are formed in the vicinity of the inner surface of a part. The present work is devoted to a theoretical study of the process of rotational autofrettage of a hollow cylinder with fixed ends. The formulation of the problem is based on the theory of infinitesimal elastoplastic deformations, the Tresca plasticity condition and the flow rule associated with it. It is assumed that at the loading stage the cylinder material follows the linear-exponential law of isotropic hardening, and when unloaded it behaves as purely elastic body. The effect of a decrease in Young's modulus during unloading as a result of preliminary plastic deformation and its influence on residual stresses caused by rotational autofrettage of the cylinder are studied. To quantitatively describe the variation in Young's modulus, an exponential model with saturation is used. For the load stage, an exact analytical solution is obtained based on the Lambert W-function. Calculation of residual stresses in the cylinder is performed using the Runge-Kutta method. As an example, materials with significant decrease in Young's modulus are considered, namely aluminum alloy AA6022, steel DP980 and manganese steel. It has been established that taking into account the variable Young's modulus can lead to a significant reduction in the calculated level of residual stresses. This effect is especially important for the calculation of thick-walled cylinders and fairly high autofrettage velocities.