INVESTIGATION OF THE STRESS-STRAIN STATE OF THE NANOSATELLITE POLYITAN-2 UNDER QUASI-STATIC OVERLOAD ON THE STAGE OF ASCENT

The results of numerical modeling of the stress-strain state of the geomassif under the influence of natural technogenic forces are presented. To carry out computational experiments, a mathematical model was developed, in the constitutive relations of which the nonlinear relationship between stresses and deformations of rocks and their different resistance to tension or compression are taken into account. A computer program was developed, and an example is given in which the results of a nonlinear solution and a boundary value problem of the theory of elasticity are compared.

Introduction. The process of municipal solid waste (further MSW) generation is inextricably linked with the life of humanity. Every day each person generates some, a small amount of garbage. As a result millions of tons of MSW are generated daily in the world which are unsuitable for further use and require disposal. There are various ways of handling MSW including their treatment, recycling and disposal. In Russian Federation the vast majority of MSW are currently located on the specially equipped facilities –– waste landfills. To date the most common waste management strategy remains their placement in a landfill. Waste landfills are arrays of stored waste and are special engineering structures designed for the safe isolation of their contents from the environment. Landfill includes gas exhaust and leachate drainage systems, liner and cover systems. The main component of this structure is waste itself. Mechanical stability of landfills should be provided at all stages of waste storage as well as after it complete filling to designed capacity and at post-closure stage. As the result of deformation of unstable waste, all landfill systems can be destroyed up to the collapse of garbage array leading to the significant environmental and other consequences. One of the most common problems leading to the various incidents at landfills is an incorrect assessment of their stability. MSW landfill is a complex multiphase system in which various interacting processes occur simultaneously. The main factor in the calculation and design of landfills is the forecast of their settlements. Studies by many authors have established that biological decomposition has a significant impact on the properties of MSW after which the waste is considered as the landfill soil with a particle size of up to 20 mm. Materials and methods. The paper presents the methodology and the results of numerical modeling of stress-strain state of the designed object “Waste Landfill”. The facility is an array of municipal solid waste of 38 meters high. Waste is stacked in the layers of 1.75 m thick. Each waste layer is covered by the loam cover of 0.25 m thick. Stress-strain state of municipal solid waste including biological creep was modelled using well-known “Soft-Soil-Creep model” (SSC-model). Results. The results of numerical simulation of stress-strain state of the waste pile at all stages of the filling and in the post-closure period are presented. An assessment of the increase in the capacity of the landfill due to the compaction and biological creep has been performed. Stability analysis of the landfill and potential failure mechanisms at different stages of filling and operation are presented. Conclusions. Numerical modeling of stress-strain state of the MSW array using the “Soft-Soil-Creep model” allows to analyze the stability of the waste pile at any stage of landfill filling and evaluate the increase in landfill capacity due to the waste settlement taking into account the mechanical creep and biocompression during layer-by-layer filling.

The article presents calculation results for model elastic problem of defining stress-strain state of a deep beam preformed in 3D and 2D statements with the use of ANSYS software package. Geometric relations are taken in the form of Cauchy equations. The purpose of the study is to assess error in the results obtained for the two statements and to draw a conclusion on the possibility of using 2D statement for the deep beam under study. Based on 3D statement calculation results one may observe a short area near the support surface of a deep beam with the maximum load across the entire thickness. In this area the concentration of maximum stress values and maximum linear and angular deformations in the structure material are observed. The area is located on the axis of symmetry of the deep beam near the inner edge of support surface. It is found that the stress intensity values obtained for the two statements have considerable differences in this area, for that reason 3D statement shall be used when performing calculations for the deep beam. This way of solving the problem is illustrative of stress-strain state parameters distribution across the thickness of the structure, which is necessary for its strength evaluation.

Based on numerical modeling of stress-strain state of rocks and the in situ deformation monitoring of rocks mass surrounding underground excavations, the authors determine stability criteria for mine structural elements in terms of the Aikhal Mine where mining has been transferred under the worked-out open pit bottom. Using the determined criteria, the stress-strain state and subsidence of the crown pillar are assessed, considering current stage of the water table in the open pit. The article gives predictive estimate of the change in the stress-strain state and subsidence of the crown pillar upon the water level raising.

Modelling a Reinforced Sandy Pile Rheology when Reacting with Water-saturated Ground

The Paton Welding Journal, 2021, №08. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

The article presents modeling cellular concrete masonry reinforced with composite meshes. Local numerical models were verified by physical experiments. Using three-dimensional models, an assessment of impact on bearing capacity of reinforcing the masonry with composite polymer meshes was made. Subject: numerical modeling of stress-strain state for buildings made of cellular concrete masonry. Materials and methods: the research was carried out on numerical models in the LIRA-SAPR software using the finite element method in a physically nonlinear formulation Results: using local models, nonlinear characteristics were determined that allow reliable modeling of cellular concrete masonry. Then, using three-dimensional models, an assessment was made of the effect of the usefulness, type and degree of reinforcement of cellular concrete masonry with composite polymer meshes. Conclusions: cellular concrete masonry is a material that allows for an energy-efficient building. Reinforcement of masonry using composite polymer meshes allows to significantly increase the seismic resistance of the building's load-bearing system.

The paper presents the results of numerical modeling and analysis of stress-strain state of the epicentral zone of the strong earthquake in the north-east of China, which occurred on 27.07.1976 with Ms=7.8. Many present-day works continue to discuss the reasons for such a strong earthquake, which occurred in tectonic conditions ‒ far from interplate boundaries, inside the Tangshan tectonic block bounded by tectonic faults. However, published new geodynamic, seismological, geophysical and geodetic data provide confidence in the determining role of fault tectonics in this region. Based on the analysis of the results of modeling of the stress-strain state preceding the Tangshan earthquake with coseismic geophysical and geodetic data, we propose a model of earthquake rupture formation. The results of comparison of independent estimates of shear stresses with the results of modeling in the sources of strong earthquakes suggest that the areas of tectonic stress concentration are localized in the interfault rupture of the Tangshan fault, reaching maximum values at the termination of fault ruptures σi ≈ 50 MPa и τxy ≈ 20 MPa. The hypocenter of the main seismic event (taking into account the error of coordinate determination) is located in the region of stress intensity 35‒50 MPa and the ratio of main stresses σxx/σyy ≈ 8–10. It should be expected that these zones are the starting site of rupture, the extent of which depends on the amount of accumulated elastic potential energy of tectonic stresses in the adjacent region. For the Tangshan earthquake, this area corresponds to a high intensity of stresses exceeding 30 MPa in a band with a length more than 30 km and a width reaching 4.5 km.

Introduction. The article explores the stress-strain state of a distribution pair of aggregates of a volumetric hydraulic drive and the search for ways to increase its durability. Materials and Methods. In the process of studying, the generally accepted principles of the theories of friction, reliability, elasticity, mechanisms and machines, and mathematical modeling were used. To simulate the stress-strain state, an engineering analysis system ANSYS was used. Distribution pairs of hydraulic pumps 313.3.112, GST-112 and Sauer Danfoss 90R075 were chosen as objects of study. Results. As a result of the study there were obtained values of the real contact stresses and long-term current stress on the distribution of pairs of units of volumetric hydraulic drive: the 313.3.112 hydraulic pump is 26,93 MPa; for GTS-112 water pump is of 22.21 MPa for the Sauer Danfoss 90R075 hydraulic pump is 27,12 MPa. It is revealed that the area located on the discharge side is a subject to the greatest loads. This is the cause of one-sided wear of spherical surfaces, which is quite common in units decommissioned. The values of contact stresses in the joints hardened by the method of electric spark machining are on average 1.4 and 9.4 % lower than in not unhardened. In the process of electric spark machining there is a redistribution of stresses on the surface that leads to a decrease of the operating load in the connections. Conclusions. The study allowed modelling the stress-strain state in new and hardened distribution pairs of volumetric hydraulic drive units under operating conditions and suggesting ways to increase its durability. It was established that to increase the wear resistance of a resolving compound and the durability of the volumetric hydraulic drive aggregates, it is necessary to ensure that in distribution pairs the maximum bearing capacity is greater than the maximum long-term operating load in these connections. To solve this problem, it is proposed to create coatings with high tribotechnical properties by the method of electricspark machining. Keywords: resource-limiting compound, volumetric hydraulic drive, modeling, finite element method, bearing capacity, operating load, wear resistance, electrospark machining For citation: Ionov P. A., Senin P. V., Stolyarov A. V. Modeling of Stress-Strain State in Connection Resource Defines of Volumetric Hydraulic Drive. Vestnik Mordovskogo universiteta = Mordovia University Bulletin. 2018; 28(4):537–551. DOI: https://doi.org/10.15507/0236-2910.028.201804.537-551 Acknowledgements: The study was conducted with the financial support of the Ministry of Education and Science of the Russian Federation (state task, direction: development of competencies) project № 11.3416.2017/4.6 “Development of technologies and tools to improve the durability of parts, assemblies, machines and equipment by creating nanostructured coatings sources of concentrated energy”.

The paper provides the strength analysis performed for POLYITAN-2 nano-satellite under quasistatic overload conditions arising at the ascent stage. An efficient solid-state model together with its corresponding finite element model has been developed for nano-satellite. The numerical investigation of the stress-strain state of nano-satellite has been performed using the ANSYS software package. The maximum relative displacements of structural elements, as well as safety factors, have been determined. Different strength criteria were analyzed for the strength assessment of nano-satellite structural elements made of composite materials. It is found the considered POLYITAN-2 structure satisfies the critical strength and stiffness requirements.

The paper proposes a variant of the algorithm for 3D numerical simulation of the rock mass stress-strain state in the vicinity of structural heterogeneities by the finite element method. Modeling of the stress-strain state is used, among other things, when analyzing the fractures in the rock mass, which can occur as a breakage or a shear along the weakening planes. The rock massif has a block structure, where the boundaries of various-scale blocks are structural disturbances of different orders. The surface planes of structural heterogeneities usually have complex geometry and spatial orientation, so the most adequate results can be obtained by 3D modeling of the disturbed rock mass. Besides, it is important to take into account the type of the stress-strain state, which can be not only gravitational, but also gravitational-tectonic, including horizontal loading of the rock mass. Accounting these features allows obtaining the most adequate geomechanical model of the studied object. For this purpose, the authors have studied and analyzed the existing approaches to modeling heterogeneities in the rock mass, including using the Goodman contact element, and developed its 3D modification. A mining engineer needs to have a handy tool that allows creating and editing a geomechanical model, taking into account mining plans and related sections. The model navigation, edition of its individual blocks to specify geology and creation of local sub-models make it necessary to use structured meshes of finite elements. Modification of the model with the introduction of contact elements entails the creation of an unstructured mesh, which complicates further manipulations with it. To solve this problem, a special zero element was developed, which allows saving a structured mesh format when implementing a contact element. This zero element, like the contact element, has zero thickness, and its nodes have averaged strength characteristics of adjacent blocks of the undisturbed rock mass. The result of these studies is a tool that allows creating 3D models of the rock mass stress-strain state, taking into account its structural heterogeneities and preserving the regular structure of the finite element mesh.

Improving ductility and bending features of poplar glued laminated beams by means of embedded carbon material

In order to study the strength of the proposed rope threaded joint for machine parts made of reinforced composite materials, a modeling of a stress-strain state was conducted using the software of finite-element analysis LS-DYNA. Stress-strain state modeling was conducted for a rope threaded joint, affecting on the main performance parameters considered to be p – thread pitch (p = 4 mm), and t – thread depth (t = 1 mm). The main thread parameters taken for the model were up to the metric thread М6 (ISO 724:1993) parameters.

Cyclic performance of in-plane shear cross-laminated timber panel-to-panel surface spline connections

Problem statement. The new solutions of hybrid constructions of multi-storey buildings are being developed, in which the main structural material is timber and reinforced concrete or steel is used to ensure spatial rigidity. The problem in developing such projects is a significant difference in the deformation characteristics and rheological properties of timber and concrete, which can significantly affect the load-bearing capacity and serviceability of the hybrid building. At present time the issues of joint work of these materials in the elements of structural systems are insufficiently studied. The purpose of the article is to investigate the stress-strain state of hybrid wood-reinforced concrete multi-storey buildings taking into account the influence of creep deformations. Conclusion.The method of taking into account the peculiarities of deformation and creep of timber and concrete in the calculation of hybrid multi-storey buildings is presented. Using the software complex "Lira" the modeling of the stress-strain state of multi-storey buildings of hybrid construction with columns and beams made of glued laminated timber and the reinforced concrete rigidity core. It is established that the characteristics of deformation and creep of materials significantly affect the value of displacement of the frame elements. The values of vertical displacements, taking into account the creep, are 1,57…1,66 times higher than those determined in the elastic stage. Non-uniform deformation of vertical structures causes skew of the storey cells, redistribution of forces between the elements of the frame and the appearance of additional longitudinal forces in the floor beams. Thus, for design multi-storey hybrid wood-reinforced concrete buildings, it is necessary to take into account the influence of deformation and rheological characteristics of wood and concrete on the parameters of the stress-strain state.