Contact Interaction Of Bodies Research Articles

Particular Strength Criteria for Microstructural Analysis of Masonry

This study presents a set of "particular" strength criteria of the constituent elements of masonry as a composite material constituted by homogeneous fragments of heterogeneous materials (brick and mortar) and contact interface (shear and normal adhesive strength). This paper proposes the expressions for calculate the values of each particular strength criterion used for the discrete modelling of masonry. The results were obtained based on the experimental study of stresses and failure modes in masonry specimens, mortar samples and brick units. There are determined a set of 8 particular strength criteria, which correspond to the actual work of the masonry constituent elements. Their use in the structural micromodelling of masonry allows to determine the body contact interactions, track the gradual accumulation of local stresses, exclude from the calculation model the elements in which a particular strength criterion has been exceeded, and modelling the degradation process.

CONTACT INTERACTION OF SIMILAR SHAPE BODIES AT SMALL DISTURBANCE OF INITIAL GAP DISTRIBUTION

In this work, on the development of previous research, a model of contact interaction of similar shape bodies is built. Contact in the system "punch - stamped material - matrix" is considered. A gap is set between the material to be stamped and the matrix, which varies in circular coordinate. The regularities of the change of contact pressure and contact areas with variation of the law of distribution of the initial gap are determined. The influence of the load level on these parameters is also determined. In particular, the analysis of the influence of the number of waves in the distribution of the initial gap in the circular direction on the nature of the distribution of contact areas and contact pressure. It is established that at low level of loads significant non-uniformity of the contact pressure distribution along the circular coordinate is realized. In the future, with increasing load levels, this unevenness decreases. The distribution of contact pressure tends to the case of contact with nominally coincident surfaces of the matrix and the material to be stamped, i.e. at zero gap. Thus, an analytical-numerical method for studying the contact interaction of closely shaped bodies with low perturbation of the initial gap distribution has been developed. Regularities of influence of constructive and technological parameters on contact interaction of these bodies on an example of elements of stamp equipment are also established. Keywords: contact interaction; stress-strain state; elements of stamps; contact area; contact pressure

NEW PHYSICAL FACTORS IN CONTACT INTERACTION OF ELASTIC BODIES OVER CLOSELY MATCHED SURFACES

The paper contains generalization and development of approaches, models and research methods for contact interaction of complex shaped bodies. In the case of contact along the surfaces of a close shape there are a number of problems. Firstly, analytical methods are not universally applied. Secondly, with a small gap between the surfaces of the contacting bodies the contribution of the deformation of the intermediate and surface layers to the balance of displacements becomes substantial. Thirdly, the application of traditional numerical methods also sharply increases the contribution of errors in contact surface shape approximation. All these factors bring on the need to develop new approaches, models and methods for the analysis of contact interaction of complex shaped bodies. For this purpose, the apparatus of the theory of variational inequalities is applied to deliver Kalker’s variational principle. In addition, a new principle for deriving multiple models of contact interaction of complex shaped bodies has been developed. It consists in gradually increasing the number of physical factors that are taken into account when building these models. This makes it possible to form a sequence of varied parametric models by taking into account new factors while naturally avoiding conflict situations. Furthermore it ensures inheritance in the sequence of models of different levels. The proposed improved approaches, models and methods are illustrated by the case study of the contact interaction of bodies with the intermediate layers located between them. Keywords: contact interaction, complex shaped body, finite element method, boundary element method, Kalker’s variational principle, variational inequalities

Mathematical Modeling of the Contact Interaction of the Fuel Element Section, Including up to 100 Pellets, Taking into Account Creep

An algorithm for solving axisymmetric contact problems of thermoelasticity taking into account creep processes is considered. To account for the contact interaction of bodies, the mortar method was used, and the modified Jacobi method was used to solve the resulting system of linear equations. For the numerical solution of the problem simulating the creep process, time discretization based on the implicit Euler method was applied, and the Newton method was used to linearize the resulting system of equations. An algorithm with automatic step selection based on obtaining an estimate of the local error of the method is proposed. The results of applying the proposed algorithm to a demonstration problem simulating thermomechanical processes in a section of a fuel element comprising from 1 to 100 fuel pellets are presented.

Experimental and Analytical Determination of the Coefficient of Dynamic Loading in the Contact Interaction of Bodies

The calculation of the coefficient of dynamism of the contact interaction of bodies (lead balls and wheat grains with a moisture content of 11.5%) was carried out based on the hypothesis of equality of the work consumed during static and dynamic deformation of bodies, according to the formula:Θ=(So+Su)/(Sod+Su),where So – residual deformation of the body under static loading;Sod – residual deformation of the body under dynamic loading;Su – elastic deformation under static and dynamic loading.The components of the formula were determined on specially designed devices:– on an electromechanical press with static interaction of bodies, at a deformation rate of 0,055 m/s, the following values were determined from the load – discharge diagrams: the value of elastic deformation Su and the maximum residual deformation of bodies So.– on a vertical copra (at a contact interaction speed of 1-2 m/s) and a shock stand (at an impact speed of 11-15 m/s), the residual Sod deformation was determined by the size of the contact spot on the bodies after the impact.The calculated values of the dynamism coefficient were:for lead balls – 1,4-2,1;for wheat grains – 1,3-1,45.The results obtained indicate that the value of the dynamism coefficient increases with increasing impact velocity, with the same work spent on deformation, since the proportion of residual deformation in the total deformation of bodies decreases (bodies are strengthened).It is advisable to continue experiments to determine the coefficient of dynamism of bodies depending on the impact velocity, the configuration of the impact surface and the physical properties of the contacting bodies.

CONTACT INTERACTION OF BODIES WITH SURFACES OF SIMILAR SHAPE

The contact interaction of bodies with surfaces of similar shape is investigated in the work. Cases of bodies with contact surfaces, the gap between which is a function of two coordinates, are considered. On the example of semi-matrices of molds the regularities of contact pressure distribution are established. The effect of geometry variation away from the nominal shape as well as the properties of the intermediate layer on contact pressure distribution is evaluated. The contact of bodies whose surfaces coincide in the nominal state along one line is also investigated. The influence of perturbations of the gap shape between these bodies along the lines of incidence was investigated on the example of rollers. The influence of such perturbation on the contact pressure distribution is demonstrated. The influence of the perturbation of the crossing angle between the rollers and the properties of the intermediate layer on the contact pressure distribution is also investigated. It was established that ultimate performance of machine units that contain parts in conforming contact are determined not by the nominal shape of the working surfaces but rather by the actual shape due to the deformations under the loads.

Математическое моделирование контактного взаимодействия элементов твэла с учетом ползучести на основе mortar-метода

An algorithm for solving axisymmetric contact problems of the theory of thermoelasticity with creep processes is considered. To take into account the contact interaction of bodies, the mortar method was used, a modified method of over relaxation was used to solve the obtained system of linear equations. For the test task, the resulting numerical solution is compared to the analytical solution. The results of application of the proposed algorithm for the demonstration problem simulating thermomechanical processes in the fuel element section including from 2 to 10 fuel pellets are presented..

Original equations of a geometrically nonlinear dynamic problem of essential deformation for axisymmetric and flat bodies

Widely used in various fields of technology are the elements and details that are in the process of manufacturing or operating in conditions of significant plastic deformation. This is typical of sealing ring gaskets, rivets in connecting operations, blanks in metal processing, etc. As a rule, the mechanical processes under consideration occur under the influence of intense dynamic loads. Significantly, deformation is also influenced by the condition of their interaction with the contacting parts of the instrument. Further improvement of the constructive decisions of a significant number of responsible nodes and technological processes largely depends on the completeness and reliability of the information on the peculiarities of changing the pattern of the stress-strain state of the selected class of objects in the process of deformation.In recent years, the requirements for the construction of mechanical models for the study of the processes of manufacturing and operating components and equipment has grown significantly, which is determined by increasing the level of accuracy and reliability of the results, prompting the use of more and more detailed calculation schemes. In addition, the difficulties of studying the behavior of structures in the presence of dynamic loads is multiplied by comparison with static analysis.In this connection, the importance of developing effective methods for studying the processes of plastic molding of bodies, taking into account geometric nonlinearity and contact interaction under the action of dynamic loads, increases.The paper considers the original equations of a geometrically nonlinear dynamic problem for the study of processes of significant plastic deformation. The problem statement is given under the condition of contact interaction of bodies. The equations of state are presented in the reference initial, changeable and actual coordinate systems.

B¯(*)B¯(*) interactions in chiral effective field theory

In this work, the intermeson interactions of double-beauty $\bar{B}\bar{B}$, $\bar{B}\bar{B}^\ast$, and $\bar{B}^\ast\bar{B}^\ast$ systems have been studied with heavy meson chiral effective field theory. The effective potentials are calculated with Weinberg's scheme up to one-loop level. At the leading order, four body contact interactions and one pion exchange contributions are considered. In addition to two pion exchange diagrams, we include the one-loop chiral corrections to contact terms and one pion exchange diagrams at the next-to-leading order. The behaviours of effective potentials both in momentum space and coordinate space are investigated and discussed extensively. We notice the contact terms play important roles in determining the characteristics of the total potentials. Only the potentials in $I(J^P)=0(1^+)$ $\bar{B}\bar{B}^\ast$ and $\bar{B}^\ast\bar{B}^\ast$ systems are attractive, and the corresponding binding energies in these two channels are solved to be $\Delta E_{\bar{B}\bar{B}^\ast}\simeq -12.6^{+9.2}_{-12.9}$ MeV and $\Delta E_{\bar{B}^\ast\bar{B}^\ast}\simeq -23.8^{+16.3}_{-21.5}$ MeV, respectively. The masses of $0(1^+)$ $\bar{B}\bar{B}^\ast$ and $\bar{B}^\ast\bar{B}^\ast$ states lie above the threshold of their electromagnetic decay modes $\bar{B}\bar{B}\gamma$ and $\bar{B}\bar{B}\gamma\gamma$, and thus they can be reconstructable via electromagnetic interactions. Our calculation not only provides some useful information to explore exotic doubly-bottomed molecular states for future experiments, but also is helpful for the extrapolations of Lattice QCD simulations.

Mathematical model of plowing forces to account for flank wear using FME modeling for orthogonal cutting scheme

This article develops a model simulating the formation of the tension condition on the flank surface of a tool’s tooth in orthogonal cutting based on the example of face milling and using the plastic theory of contact interaction of bodies. A calculation was performed in the ANSYS/LS-DYNA program using the finite element method. The model allows us to determine the stress value on the cutting tool’s flank surface for various cutting modes. Analysis of the orthogonal cutting process has been carried out using the simulation model that allows the following to be defined: the flank surface stress diagram model, introducing the flank wear value defined by the processes of the shear zone, and contact interaction of the cutting tool’s flank surface and the workpiece. The basic and normal cutting force components in the cross section perpendicular to the cutting edge were obtained. Our main result is the mathematical model of the force in the orthogonal cutting scheme, introducing the force components on the front surface conditioned by the processes of the shear zone and on the flank surface of the cutting tool, introducing the flank wear value.

Stress response, gut microbial diversity and sexual signals correlate with social interactions.

Theory predicts that social interactions are dynamically linked to phenotype. Yet because social interactions are difficult to quantify, little is known about the precise details on how interactivity is linked to phenotype. Here, we deployed proximity loggers on North American barn swallows (Hirundo rustica erythrogaster) to examine intercorrelations among social interactions, morphology and features of the phenotype that are sensitive to the social context: stress-induced corticosterone (CORT) and gut microbial diversity. We analysed relationships at two spatial scales of interaction: (i) body contact and (ii) social interactions occurring between 0.1 and 5 m. Network analysis revealed that relationships between social interactions, morphology, CORT and gut microbial diversity varied depending on the sexes of the individuals interacting and the spatial scale of interaction proximity. We found evidence that body contact interactions were related to diversity of socially transmitted microbes and that looser social interactions were related to signalling traits and CORT.

Computer Modeling as Evaluation Method of Column Base Bearing Capacity in Tower Buildings

This paper is devoted to computer modeling of composite structure the column base under question is contact interaction of bodies, which, when taken into account, allows to simulate the interaction of their constituent elements undergoing deformation.In modern tower buildings with braced framing, column structural design for compression is usually done taking into account random eccentricities. To attain a relatively uniform load transmission from a column to a foundation, the column base has to be made of high-strength metal. The required height of the column base can be composed of single individual plates, without reducing the design strength of metal.The strain state in contact zones and distribution patterns of contact pressure are extremely diverse. It depends on a number of factors affecting cohesion. That is why we considered the system of approximating models, which allows to find out to what extent their complication is necessary with the view to modern computers’ potential.We used design diagram with “soft” loading, which evaluates the upper bound of structure bearing capacity and the diagram with “stiff” loading, which evaluates the lower bound.

Computationally Efficient Magnetic Resonance Imaging Based Surface Contact Modeling as a Tool to Evaluate Joint Injuries and Outcomes of Surgical Interventions Compared to Finite Element Modeling

Joint injuries and the resulting posttraumatic osteoarthritis (OA) are a significant problem. There is still a need for tools to evaluate joint injuries, their effect on joint mechanics, and the relationship between altered mechanics and OA. Better understanding of injuries and their relationship to OA may aid in the development or refinement of treatment methods. This may be partially achieved by monitoring changes in joint mechanics that are a direct consequence of injury. Techniques such as image-based finite element modeling can provide in vivo joint mechanics data but can also be laborious and computationally expensive. Alternate modeling techniques that can provide similar results in a computationally efficient manner are an attractive prospect. It is likely possible to estimate risk of OA due to injury from surface contact mechanics data alone. The objective of this study was to compare joint contact mechanics from image-based surface contact modeling (SCM) and finite element modeling (FEM) in normal, injured (scapholunate ligament tear), and surgically repaired radiocarpal joints. Since FEM is accepted as the gold standard to evaluate joint contact stresses, our assumption was that results obtained using this method would accurately represent the true value. Magnetic resonance images (MRI) of the normal, injured, and postoperative wrists of three subjects were acquired when relaxed and during functional grasp. Surface and volumetric models of the radiolunate and radioscaphoid articulations were constructed from the relaxed images for SCM and FEM analyses, respectively. Kinematic boundary conditions were acquired from image registration between the relaxed and grasp images. For the SCM technique, a linear contact relationship was used to estimate contact outcomes based on interactions of the rigid articular surfaces in contact. For FEM, a pressure-overclosure relationship was used to estimate outcomes based on deformable body contact interactions. The SCM technique was able to evaluate variations in contact outcomes arising from scapholunate ligament injury and also the effects of surgical repair, with similar accuracy to the FEM gold standard. At least 80% of contact forces, peak contact pressures, mean contact pressures and contact areas from SCM were within 10 N, 0.5 MPa, 0.2 MPa, and 15 mm2, respectively, of the results from FEM, regardless of the state of the wrist. Depending on the application, the MRI-based SCM technique has the potential to provide clinically relevant subject-specific results in a computationally efficient manner compared to FEM.

Evaluation of quality indicators contacting the surface of the tribological system «Wheel – Rail»

Purpose. Modern ideas about the contact interaction of bodies in friction are based on models that take into account the geometric parameters of the surface layers constituting tribosystems. These models provide a high level of adequacy to describe the features of the relief of the surfaces of parts and their impact on the performance characteristics of friction in the elastic stresses. However, the possibility of plastic deformations in the surface layers, particularly before using friction systems, these models do not account for. The aim of this work is the development of new mathematical approaches previously applied accounting strains and their effect on the performance of tribosystems. Methodology. Using the contact mechanics approaches analyzed the influence of preload on contacting a flat rough surfaces using a model based on the assumption of normal distribution of heights and roughness of plastic deformation at the first load. Findings. Analytically determined that under moderate pressure reduction from baseline, the actual contact area is proportional to the pressure in the 2/3 power. Originality. It is found that the contact patch size is proportional to the pressure of the first load. Practical value. It is established that at pressures lower than originally applied to the contact surfaces, the high values of the actual surface contact, the number of patches of actual contact are typical, than for the same pressure at the first load.

Fractional quantum Hall states of a Bose gas with a spin–orbit coupling

We study the fractional quantum Hall phases of a pseudospin-1/2 Bose gas in an artificial gauge field. In addition to an external magnetic field, the gauge field mimics an intrinsic spin–orbit coupling of the Rashba type. While the spin degeneracy of the Landau levels is lifted by the spin–orbit coupling, the crossing of two Landau levels at certain coupling strengths gives rise to a new degeneracy. We therefore take into account two Landau levels and perform exact diagonalization of the many-body Hamiltonian. We study and characterize the quantum Hall phases which occur in the vicinity of the degeneracy point. Notably, we describe the different states appearing at the Laughlin fillings, ν = 1/2 and ν = 1/4. While for these filling factors incompressible phases disappear at the degeneracy point, we find gaps in the spectra of denser systems at ν = 3/2 and ν = 2. For filling factors ν = 2/3 and ν = 4/3, we discuss the connection of the exact ground states to the non-Abelian spin singlet states, obtained as the ground states of (k + 1)-body contact interactions.

Contact interaction of bodies with a periodic relief during partial slip

The two-dimensional contact problem for two elastic half-spaces of identical materials with a periodic system of grooves, in the surface of one of them is considered when partial slip is taken into account. It is assumed that there is initially complete contact between the surfaces of the bodies under the action of a normal load and that a tangential load is then added to them with the resultant appearance of frictional slip zones within each groove. The stress-strain state of the bodies is represented in terms of a specified function of the groove height and an unknown function of the relative displacement of the boundaries of the bodies in the slip zones. To determine the latter, a singular integral equation with a Hilbert kernel is obtained and solved analytically. The width of the slip zones is found from the condition that the contact shear stresses are limited. The dependences of the contact parameters on the applied load and the groove width are analysed.

Wear resistance of bodies protected by a thin composite coating

The mechanical contact interaction of bodies with a thin composite coating is investigated with account of wear. The thermal effects are not considered. The coating is modeled by a thin plate. Between the body and the coating is an interlayer, which is modeled by a Winkler body with one modulus of subgrade reaction. Under the action of a rigid stamp on the coating, the process of abrasive wear proceeds. The contact interaction of the coating with the base is described by using the model of an intermediate layer. To determine the stress-strain state of the coating, equations of the generalized theory of plates including the shear strains and the compression of normal are utilized. For the contact wear problem formulated, the basic integral equation with a Fredholm-type kernel is derived, and its solution algorithm is proposed. Numerical results are presented.

Thermoelastic contact interaction of bodies in the presence of surface thermophysical irregularities

We study the thermoelastic contact interaction (in the absence of friction) of half-spaces under conditions of planar deformation in the presence of thin surface thermophysical irregularities that are taken into account by means of generalized conditions of thermal contact with one another. The problem is reduced to solving a system of singular integrodifferential equations with respect to the jumps of temperature and heat flow on the boundary of a section. We analyze the influence of a nonuniform thermal resistance distributed periodically along the surface or localized in one region of it on the distribution of temperature and stresses in the bodies and on their boundary. Four figures.

Rocking gesture as communicative behavior in the wild pygmy chimpanzees in Wamba, central Zaire

The pygmy chimpanzee rocks its upper body in a variety of contexts, while the common chimpanzee rocks in only 3 situations; courtship, charging display and frustration. In the pygmy chimpanzee, behaviors involving rocking except for charging display are intentional communicative behaviors which bring about various body contact interactions. Each interaction pattern corresponds to each information set consisting of participant age-sex combination, additional signal and group situation. Rocking without any other gestures functions as a sign of tolerance or appeasement to access. This suggests that communicative behaviors involving rocking have a kind of segmentive structure, i.e., rocking represents access while other additional information sets represent the interaction pattern, the character of which is analogous to linguistic communication. Rocking in most interactions possibly derived from rocking in courtship behavior which appears to be a ritualized form of frustrated rocking, while other forms of rocking may possibly be of different origins.

Energy bands in nonlinear schrödinger equations

Energy bands are shown to arise in the Hartree approximation to the Schrödinger equation for ( p + 1)- and (2 p + 1)- body contact interactions. The exact wave functions are solutions of nonlinear Schrödinger equations similar to envelope solitons.