Stress-strain State Of Structural Elements Research Articles

Design and development of undercarriage systems for agricultural tractors with replaceable half-tracks

The need to use such propulsion devices in mobile agricultural power units is substantiated. The relevance of this development based on global trends is shown. The purpose of the research is to develop the design, to evaluate strain-stress state and functional characteristics of undercarriages of agricultural tractors with replaceable half-tracks. An experimental design of the replaceable tracked undercarriage was developed and manufactured, modeling of loading modes was performed, calculations were carried out by the finite element method of the stress-strain state of structural elements according to 6 load schemes – tractor parking on a flat horizontal surface; movement with maximum traction force; parking across a 30° slope for the upper track; parking across a 30° slope for the lower caterpillar; driving into an obstacle with a deviation of 15°; driving over obstacles based on the central rollers. It was determined that the selected structural material, by the above mentioned loading modes ensure the operability of replaceable tracked undercarriage. Calculations were carried out to check the adequacy of the developed mathematical model using field tests in testing ground of FSAC VIM. It was determined that the maximum stress-strain state of the frame structure of a replaceable tracked undercarriage for all types of loading did not exceed 100 MPa. This provides a two-fold margin of safety in terms of fluidity of the structure, taking into account the characteristics of the selected material. In the maximum loaded state - parking across a slope of 30° - the highest stress on the upper track is 161 MPa, which corresponds to a safety margin of 1.45. The deformation of the bearing assembly was no more than 4 mm, which is allowed by the design of the drive assembly and the caterpillar.

Investigation of mechanical properties of composite materials reinforced with carbon fibers

Theoretical and experimental methods for obtaining and investigating effective thermomechanical characteristics - residual stresses and deformation in panels made of nanomodified materials with asymmetrical reinforcement scheme have been developed in this paper. The study of the residual stress-strain state of structural elements made of carbon plastic using the values of thermoelastic characteristics of composite monolayers identified on the basis of the developed methods meade it possible to reveal the possibility of reducing the residual stress-strain state in structures with asymmetric reinforcement schemes.

Application of a full-scale strain gauge to study the stress-strain state of structures subjected to the action of a liquid-metal coolant at high temperatures

A technique for studying the stress-strain state of structural elements exposed to an aggressive liquid metal with temperatures up to 500°C was developed. Strain gauges were used to solve the problem installed on the internal and external surfaces of the equipment. The operability of measuring instruments was checked during bench tests under conditions close to operational ones. An algorithm was proposed to determine the stresses at dangerous points of the structure. The developed technique was assessed during tests of a BN-type nuclear reactor.

ANALYTICAL AND NUMERICAL SIMULATION FOR THE FORCE OF ADHESION OF REINFORCING ROD WITH CONCRETE

The purpose of this article is to build a mathematical model for calculating the stress-strain state of structural elements of the road pavement. The model is based on the universal function parameter - the force of adhesion of the reinforcing rod to the concrete along their surface contact. It is proposed to define the specified adhesion force as the solution to the simulated boundary value problem. It is shown that it is expedient to use hyperbolic functions to solve such a problem. For the adhesion force, an analytical dependence is obtained, which is a nonlinear function. The proposed model of analysis of the stress-strain state of the reinforcement in comparison with other models is relatively simple. The results of modeling using Maple for the analytical dependence of the adhesion force on the length of the reinforcing rod are shown. It is established that the empirical parameter of the system significantly affects the distribution function of normal stresses. The developed theory will allow design engineers to solve the problem of optimizing pavement structures.

Implementation of the Lemaitre damage model with kinematic hardening in the ANSYS finite element complex

Currently, one of the most popular in fracture mechanics is taking into account damage and its effect on the stress-strain state of structural elements. In this work, the Lemaitre damage model was integrated taking, into account the combined hardening law, which combines the Armstrong - Frederick kinematic hardening law and the Voce isotropic hardening law, into the ANSYS finite element software. The model is implemented in the form of a dynamically linked library of user material for three-dimensional objects, which is tested on a cylindrical specimen with an external annular notch, both in an axisymmetric setting and in a three-dimensional one. The article presents model representations of the above-listed standard systems. This work demonstrates only one of the two stages of verification of the created program - comparison of damage fields under monotonic loading with data known in the literature - and doesn’t take into account the verification of cycle-by-cycle kinetics of plastic deformation accumulation with experimental data for low-cycle fatigue. The result of verification, consistent with similar experiments known in the literature, is confirmed in accordance with similar experiments. In addition, an analogy was found using the TSL law of the cohesive fracture mechanics approach. Despite the fact that two different types of constitutive equations are used in the cohesive model and Lemaitre, the physical meaning of these equations consists in one thing - visualization and identification of mechanisms and coordinates of damage.

Модель стенда для дослідження конструкцій з листового скла

The use of sheet glass as a structural material capable of bearing significant loads is complicated by the lack of regulatory documents for calculating the stress-strain state. This is primarily due to the variability of the strength characteristics of sheet glass. In practice, these necessary indicators are obtained by conducting full-scale research. A large number of factors that affect the strength of glass makes the test results statically heterogeneous, which leads to a high cost of research. The use of the capabilities of modern 3D modeling software systems can significantly reduce the cost of testing by virtually simulating the impact on the model of the structural element. The glass plate model is free of production defects, so its study allows for determining the general direction of the influence of structural factors on the structure's performance and its optimization. This paper presents a stand model developed in the SOLIDWORKS environment for the study of sheet glass structures under the action of uniformly distributed pressure. Analyzing the model in the SOLIDWORKS Simulation module according to the proposed settings allows to study of the stress state of flat glass depending on the parameters of the rubber gasket and to justify the design of the support unit. The model allows to estimate of the stress-strain state of structural elements based on the Mohr-Coulomb failure criterion (for a glass plate), and stresses (according to Mise, and others) for support elements. The above settings of the program ensure its conflict-free operation with low machine resource consumption. There is a possibility of variations in the design of the support unit, including taking into account the conditions of fixing (friction) elements. The localization of critical stresses in the glass plate coincides with the data from field experiments, which indicates the adequacy of the model. The developed model of the stand allows for the investigation of the stressed state of sheet glass under uniform load conditions, depending on the parameters of the rubber gasket.

Numerical and Analytical Modeling of Permanent Deformations in Panels Made of Nanomodified Carbon Fiber Reinforced Plastic with Asymmetric Packing

In this paper, a mathematical model of a multilayer panel made of nanomodified carbon fiber reinforced plastic with asymmetric packing is proposed. The introduction of nanosized particles into the composition of the composite or its components (fiber or binder) allows not only to increase its physical and mechanical properties, but also to improve the picture of the residual stress-strain state. The paper investigates the effect of nanomodification of carbon fiber reinforced plastic on the residual stress-strain state after molding using numerical and analytical methods. Numerous results of computational experiments have been obtained. The results of numerical and analytical modeling are compared with experimental data. Conclusions are drawn about the possibility of reducing the residual stress-strain state in structures with asymmetric reinforcement schemes when using a matrix containing carbon nanoparticles. A mathematical model of a multilayer panel made of nano-modified carbon fiber with asymmetric packing has been built. Investigation of the residual stress-strain state of structural elements made of carbon fiber reinforced plastic made it possible to reveal the possibility of reducing the residual stress-strain state and leash in structures with asymmetric reinforcement schemes when using a matrix containing carbon nanoparticles.

COMPUTATIONAL DESIGN OF NONLINEAR STRESS-STRAIN OF ISOTROPIC MATERIALS

The article deals with the problems of numerical modeling of nonlinear physical processes of the stress-strain state of structural elements. An elastoplastic medium of a homogeneous solid material is investigated. The results of computational experiments on the study of the process of physically nonlinear deformation of isotropic elements of three-dimensional structures with a system of one- and double-periodic spherical cavities under uniaxial compression are presented. The influence and mutual influence of stress concentrators in the form of spherical cavities, vertically located two cavities and a horizontally located system of two cavities on the deformation of the structure are investigated. Numerical algorithms have been developed for solving the problems of physically nonlinear deformation of structures made of structural materials, which make it possible to effectively use the capabilities of computer technology. The optimal parameters of computational experiments on the construction and calculation of structures made of fibrous composite materials using a specialized software package have been determined.

Obtaining of Carbon Fibers Based Composite Materials and Study of Their Mechanical Properties

In this work, theoretical and experimental methods have been developed for obtaining and studying effective thermomechanical characteristics - residual stresses and deformations in panels made of nanomodified materials with an asymmetric reinforcement scheme. The study of the residual stress-strain state of structural elements made of carbon fiber reinforced plastic using the values ​​of thermoelastic characteristics of composite monolayers identified on the basis of the developed methods made it possible to reveal the possibility of reducing the residual stress-strain state in structures with asymmetric reinforcement schemes.

The elastic, strength and thermophysical characteristics modeling of mono- and polycrystalline aluminum Al

Temperature dependences of mechanical and thermophysical properties of the material are the initial data for estimating the stress-strain state of structural elements. However, when designing, the amount of this data is usually not enough. Under these conditions, the problem of modeling these properties arises. This problem is solved by taking into account the forces of interatomic interaction in the crystal structure on the example of a single crystal and polycrystal of aluminum. The results of calculating the elastic modulus, elastic limit and yield strength, Poisson’s ratio, coefficients of thermal conductivity, thermal expansion and material density are presented. A satisfactory convergence with the available reference data is obtained. The results obtained can be used as input data for the construction of compositions and alloys based on aluminum.

Determination of the natural oscillation frequency of the structural unit of covering by the action of the shock load

The article presents the results of experimental studies of the wood-metal spatial structural unit-TTMBF-18.6. We should monition, that wood attracts designers both by its resistance to aggressive media, and by its physical properties and strength characteristics. This material has a high deformability and specific viscosity, which allows it to absorb shocks and vibrations, making it an excellent material for use in regions with increased seismic activity. The aim of the work is to obtain the frequencies of natural vibrations for the subsequent study of the dynamic characteristics of the structure. The article describes the advantages of wooden structures. The methodology of the full-scale experiment and the results of research are given. Our data obtained allow us to study the nature of the stress-strain state of structural elements during dynamic loading and in the future to obtain a dynamic design coefficient, which will help to develop a methodology for calculating structures for dynamic effects.

LVL–structures made as combined section with small-compliance connections, consistent with stress-strain state of structural elements

The use of composite structures of LVL elements of I-beam and box-shaped cross-section is the most expedient from an economic point of view. Applications for connecting the individual parts of the cross-section of ductile connections - self-tapping screws, allows you to assemble such structures at a construction site. The use of self-tapping screws installed in accordance with the direction of the tensile internal forces of the structure makes it possible to force self-tapping screws to work mainly in tension. At the same time, the most rational work of the joints is achieved — minimum work on bending and maximum work on stretching. According to the results of tests, manufactured and designed beams of composite section, it was concluded that box-shaped beams have greater load-bearing capacity and less deformability. The ratio of actual and calculated bearing capacities of composite box-section beams is higher, the required value of the safety factor, and the destruction of the test beams occurred wood, which indicates the safety margin of the connection of the elements of the composite section on the stretched self-tapping screws.

MATRIX-STRUCTURAL ANALYSIS OF THE STRESS-DEFORMED STATUS OF THE FLEXIBLE INTERFACES AND MEMS COMPONENTS

The designs of modern electronic technology are complex mechanical systems with many rigid bonds, and their microminiature in many cases has reached the physical limit of the dimensional, charge and energy quantization of components. For such mechanical systems, with non-classical methods for mechanics of fastening of separate structural elements, it is difficult to build a design model, simple enough and at the same time one that well reflects physical and dynamic properties. To ensure mechanical strength of interconnects and ultra-thin electronic components, it is necessary to determine the stress-strain state of structural elements. These reasons necessitate the use of numerical methods to calculate the dynamic parameters of the design of electronic equipment interconnections, which will improve the reliability of the developed tools that meet the requirements of regulatory technical documentation on mechanical characteristics, shorten the time and cost of their creation. Subject matter of this work is the study of beam deformation of constant cross section under the action of axial forces, bending moments and torque relative to the longitudinal axis. Goal this work is to determine the deformation of the elements of the structure of the devices using the stiffness matrix with a known vector of external forces. To achieve this goal, it is necessary to solve the following tasks: to consider the existing methods of description and analysis, which take into account the specificity of the structures and technological processes used to manufacture specific structures MEMS; explore the nature of these methods; calculate displacements and deformations using the finite element method; using the stiffness matrix to determine the deformation of the structural elements of the devices; to calculate the deformation of the beam of constant cross-section under the action of axial forces, bending moments and torque relative to the longitudinal axis. Conclusions: stiffness matrix, constructed using functional analysis, allows for the calculation of deformation of MEMS elements and electronic interconnect flexible.

Simulation of contact interaction of piezoelectric engine elements

In the article the results of a new type of piezo-electric step-engine research are presented. The original construct of piezo-electric step-engine is contained in special engineering lever called grab device that can organize back and forward rod’s motion with only one piezo element activity. To choose the effective process of piezo-electric step-engine work the mathematical model was created. This mathematical model describes inner piezo-electric step-engine process with features of contact and electroelastic deformation. Using the ANSYS application package, а finite element model of the piezo-electric step-engine has been developed. This finite element model allows estimate the stress-strain state of structural elements of the piezo-electric step-engine and determine the effective step-by-step operation mode of the piezo-electric step-engine. Using the finite element model, the influence of the piezo-electric step-engine operating mode parameters on the amount of displacement of the rod is studied. According to results of experimental studies, the proposed numerical model allows to simulate the dynamic process of step-operation of a piezo-electric step-engine with an error of no more than 6 %. This finite element model include the external load on piezo-electric step-engine and can be used to design piezo-electric step-engine of various fields of application.

Damage Contribution to the Assessment of the Stress-Strain State of Structure Elements

Engineering calculation methods for stresses and strains in the concentration zones under elastoplastic deformation of structural elements are presented and analyzed. The Makhutov-modified Neuber equation is shown to be of the most reasonable accuracy for the assessment of kinetics of effective coefficients for stress and strain concentrations. The concept of scattered damage is introduced. The effect of scattered damages on the assessment of the stress-strain state of structural elements is demonstrated by the example of elastoplastic deformation of a hole-containing plate.

The Resistance of Structural Elements to Impact and Shock-Wave Load

The ability of structural elements withstanding impact and shock-wave loading has been considered. The dynamic stress-strain state of structural elements at the stage of occurrence of large elastic-plastic deformation and fracture has been investigated, and different criteria of the structure strength has been used. The numerical and experimental results have been compared.

Experimental researches of dynamics of rope of one-end lift

Established method for determining the stress-strain state of structural elements – methodelectrical tensometry where sensitive to deformation element is a strain gauge attached on therespective scheme to the recording equipment. Describes an experimental model one-end lift installation consisting of a hoist, hoistingrope, cage models with load, damping device, a measuring plate with active strain gauges andADC/DAC ZET 210 module, a recording stress-strain state of the object.Obtained results of experimental studies that suggest about the accuracy of laws, obtainedtheoretically, and the proposed construction of a damping device with rubber elements is effective.Coefficient of dynamic rope considering only dissipative forces rope is in the range 1,94 application devicereduces the dynamic damping ratio to an average of 1,345, depending on the weight of the cargo terminal.

Sensitivity of high strain rate of structural elements in relation to dynamics properties of material

Protective structures such as process chambers, protective boxes, facing elements of vehicles, personal protection equipment, motors cases etc. widely used in modern technology has been tested in the following project. Under the influence of impact loads, the three-dimensional dynamic stress-strain state with finite dynamic displacements and deformations has arised. The deformations occur in the elastic- plastic stage. In the analysis of the high-rate deformations, the dynamic properties of the materials, which are determined based on experimental data should be taken into account. The dynamic stress state of structural elements depends essentially on the dynamic properties of the materials used. The problem is solved using the finite element method, which takes into account the specifics of the process. Boundary conditions in the element nodes must satisfy the equality movement as well as derivatives. The formed function allows to describe continuous and smooth stress changes. The numerical analysis of the dynamic stress-strain state of structural elements under impact loads, takes into account different dynamic properties of the materials. A series of numerical calculations allows to reveal the features of high-rate deformation elements of protective structures and makes recommendations to improve their dynamic strength under different loading conditions.

Analysis of the stressed state of bodies with multilayer thin coatings

We develop a procedure for the analysis of the stress-strain state of structural elements with thin multilayer coatings based on the simulation of these coatings by shells with the corresponding geometric and mechanical characteristics. In this approach, the influence of coatings on the mechanical state of the entire body-coating system is described by special generalized boundary conditions. The efficiency of the proposed approach is demonstrated by comparing the results obtained by using the developed approximate procedure with the exact solution of a Lame test problem of loading of a solid cylinder with n-layer coating.

Nondestructive monitoring of the stress-strain state of structural elements on the basis of solution of the problem of the genesis of strain anisotropy

Nondestructive monitoring of the stress-strain state of structural elements on the basis of solution of the problem of the genesis of strain anisotropy