Bodies In Contact Research Articles

Brines in deep horizons of the Udachnaya kimberlite pipe

The study was focused on groundwaters sampled from boreholes drilled to deep horizons of the Udachnaya kimberlite pipe and the host sedimentary strata. Brines in the rocks significantly complicate underground mining. Analysis of the hydrogeological setting is required to ensure safety during mining to the design levels. The features of chemical composition and the geochemical evolution of brines in the crust can be clarified in a more detail on the basis of new reliable data on strong chloride saline solutions that formed in complex geological and tectonic conditions. Kimberlite and water samples were taken from the ore bodies and host sedimentary strata at the depth of 680–980 m. Conventional methods of quantitative and instrumental analysis were applied to study the chemical composition of brines. Mineral composition of kimberlite was determined by powder diffractography and X-ray fluorescence methods. Geological, structural and tectonophysical methods were used to reveal and describe the tectonic structure of the kimberlite pipe area. Groundwaters with salinity of 280–406 g/L are strong and very strong calcium chloride brines. The chlorine-bromine ratio has a small range of 48–57; the sodium-chlorine ratio varies from 0.11 to 0.18. According to their geochemical features, the studied groundwaters are metamorphosed brines that have analogues across the Siberian platform. Physical and chemical processes were simulated to investigate the degrees of saturation of strong brines relative to the minerals of water-bearing rocks. The simulation results show that the brines in the Western ore body of the Udachnaya pipe are strongly undersaturated in the deep horizons in comparison to carbonate, sulfate and chloride minerals. This suggests possible dilution of brines during their geochemical evolution. A detailed study of the tectonic structure identified structural elements that control the distribution and migration of groundwaters in the rocks. In the mining sites, brines occur mainly in the fault zones, fault junctions and intersections with the contacts of kimberlite bodies. Integration of hydrogeological and geostructural data can provide a basis for prediction and assessment of the sites with increased water inflow in the deep horizons involved in mining.

Influence of Compressible Intercontact Liquid on the Interaction of an Elastic Body with a Rigid Base Textured by Rectangular Grooves

We study the frictionless contact of an elastic body with a rigid base containing a periodic system of rectangular grooves in the presence of a compressible liquid in the interface gaps. The formulated contact problem is reduced to a singular integral equation (SIE) with Hilbert kernel for the derivative of the height of interface gaps, which is transformed into a singular integral equation with Cauchy kernel that can be solved analytically, and a transcendental equation for the pressure of liquid obtained from the equation of state of compressible barotropic liquid. We analyze dependences of the pressure of liquid, shape of the gaps, contact approach of the bodies, and their contact compliance on the applied load and the bulk modulus of elasticity of the liquid.

Model of the Contact Stresses and Endurance of Metal–Polymer Roller Bearings

A model of the appearance of the contact of stressed bodies with raceways in a roller bearing with a polymer coating, method and computer computation program of contact parameters, and contact stresses and endurance of a metal–polymer roller bearing were considered. Results of theoretical and experimental investigations of the contact parameters, distribution of load between rolling elements, and contact stresses and endurance of the metal–polymer roller bearings were presented. An increase of the contact area and redistribution of the load between rolling elements in the metal–polymer roller bearing is shown. This leads to a decrease in the contact stresses and, as a result, to an increase of its endurance as compared with the standard bearing.

Numerically accurate code synthesis for Gauss pivoting method to solve linear systems coming from mechanics

In numerical analysis of mechanical problems, we usually have to solve huge linear systems, which may be non-symmetric or ill-conditioned. For these reasons, it is necessary to develop original and domain specific approaches to treat these family of systems. In this work, we introduce a new methodology to synthesize numerically accurate programs for the Gauss pivoting method. The synthesis is based on program transformation techniques and it is guided in its estimation of accuracy by interval arithmetic that computes the propagation of roundoff errors. We apply our code synthesis to the resolution of systems coming from finite element method arising from problems of Mechanics. We test our synthesizer on two problems concerning the flexion of a beam and the sliding contact of a viscoelastic body on a rigid foundation. Our experimental results show that the specialized synthesized code to solve the families of systems given in input is far more accurate and faster than the standard implementation of the Gauss method.

Drag, added mass and radiation damping of oscillating vertical cylindrical bodies in heave and surge in still water

Forced heave and surge motion of axisymmetric vertical cylindrical bodies with flat and rounded bases are simulated using the advanced CFD software STAR-CCM+ where the overset method is used so that the mesh local to the body moves within a stationary outer mesh. Viscous effects generating drag, and also influencing added mass and radiation damping, are determined. The Reynolds-Averaged Navier–Stokes (RANS) equations are adopted with different turbulence closure models and the water surface is captured by the volume of fluid (VOF) method. These results are of basic interest but the main motive is to assess appropriate drag coefficients for use with linear diffraction models of wave energy converters (WEC) and we have particular interest in the multi-body WEC M4. A basic dynamical model is set up so that drag, added mass and radiation damping coefficients may be obtained from the CFD results. Added mass and radiation damping coefficients were also obtained from the potential flow solver WAMIT for comparison. Mesh convergence studies were undertaken and while mesh independence was achieved for total force it was not possible for the very small shear force. In the laboratory a free heave decay test was undertaken without mechanical contact for bodies with rounded bases and the inferred drag and added mass coefficients were very close to those from CFD. Some general observations are possible for motion in heave. For the hemispherical base the drag coefficient Cd is very low for small amplitudes but this increases as amplitude is increased. For the rounded base with a flat central area the Cd is larger and for the wholly flat base it is larger again but with values less than 0.35. For a larger geometric scale (times 32) for the hemisphere and round base cases the Cd are generally somewhat reduced. For surge motion the Cd show less variation and are always greater than heave values by at least a factor of 2 which is indicative of effects due to separation and wake generation.

Peculiarities of mathematical modeling of contact interaction of massive bodies and shells

The limits of using a mathematical model of contact interaction of elastic bodies, based on the Hertz’s solution in engineering practice are defined. Numerical investigation of the contact of a massive body and a shell has been conducted when the parameters of the latter vary. Three-dimensional finite-element models of contacting bodies have been developed in the case of different curvatures and thicknesses of the shell walls. A solution of the normal contact problem is given by the force method for various configuration models of the shell. Ratios of the geometric parameters of models the finite-element schemes of the contacting bodies are ere determined where the problem is described with sufficient accuracy by the Hertz’s solution.

A numerical method for axisymmetric adhesive contact based on kalker’s variational principle

A numerical method for axisymmetric adhesive contact of elastic bodies is proposed. It allows computing the size of the contact spot, the force of interaction as well as the contact pressure distribution unrestricted to any particular form of the initial gap between the bodies. Therefore, compared to the existing analytical theories, it is a more versatile research tool that can be used to study such phenomena as adhesive strength of conjugate bodies and stability loss induced energy dissipation in oscillating contact. A variational principle that can be used to construct an approximate solution is proposed. The derived nonlinear equations of the discretized mini-max problem determine the unknown radius of the circular contact spot and the nodal values of the thought-for contact pressure. Unlike other numerical methods where contact domain is updated by subtracting or adding separate boundary elements of finite size, the proposed approach enables gradual continuous variation of the contact area. The arc-length method was implemented in the numerical routine in order to solve for the unstable sections of the adhesive interaction process. Besides the distance and force variables, the increment of the contact area is included in the control for the sake of convergence. The numerical error of the approximate method with respect to the known analytical solutions is evaluated. Linear convergence with mesh refinement in computed force and contact area is observed. Extension of the proposed approach for arbitrary three-dimensional shape of the contacting bodies is planned for the future. This is required to study the impact of the random surface roughness on their adhesive properties.

Modeling of normal contact of elastic bodies with surface relief taken into account

An approach to account the surface relief in normal contact problems for rough bodies on the basis of an additional displacement function for asperities is considered. The method and analytic expressions for calculating the additional displacement function for one-scale and two-scale wavy relief are presented. The influence of the microrelief geometric parameters, including the number of scales and asperities density, on additional displacements of the rough layer is analyzed.

TRANSFORMATION AND SCATTERING OF SURFACE WAVES ON THE ACOUSTIC LOAD TO ULTRASONIC EVALUATION AND MEASUREMENTS. Part 1. The boundary of acoustic contact is sliding

for the enhancement and improvement of ultrasonic methods evaluation and measurements. The purpose of this work is to determine the influence of the geometric parameters of the acoustic load body and its position on the coefficients of reflection and propagation of the Stoneley and Rayleigh waves and to identify the possibility of using the results of the study for practical applications.Based on the analysis of the acoustic path and the experimental data, the relationship between the measured amplitude parameters and the coefficients of the propagation and reflection of surface waves, as well as the reflectivity of the contact region of the load body in the form of a prism through the sliding boundary, which reaches up to ≈ 32–34 дБ, is established. For the first time, the dependence of these coefficients on the inclination angle of one of the prism lateral faces in the range of 0 ± 45°, dimensionless thickness of the contact layer (0–0,05) and its orientation relative to the acoustic axis.It is established that these coefficients are mainly maximal when the prism is rectangular. The coefficient of reflectivity in the hard contact of bodies is more than an order of magnitude less, and the coefficients of wave propagation – comparable in magnitude. The prospects of using the results of the study to evaluate the quality of adhesion of materials during welding, soldering, gluing, detection of defects in hardto-reach places, as well as to determine the physical and mechanical properties of metals by the proposed method of creating a reference signal are shown.

EHD Effects in Lubricated Journal Bearing

This paper presents a numerical analysis of the influence of deformation of infinite parallel cylindrical solids in partial journal bearing on the oil film characteristics. The stationary elastohydrodynamic EHD problems for three design models of bearings are considered: (1) The bearing in which the basic contribution to the elastic displacement of the surface brings the thin elastic liner; (2) The elastic cylinder and the elastic bushing which is modeled by the elastic space with a cylindrical cut; (3) The elastic cylinder and the elastic bushing in the presence of the thin elastic liner with a small module of elasticity. It is shown that when the minimum film thickness is fixed and deformations of the elastic solids increase, then the load capacity increases, reaches a maximum, and then decreases. The deformation of solids can raise load capacity many times over. When the deformation of solids increases from zero, the pressure distribution changes from the distribution of pressure in the case of rigid bodies to the distribution of pressure which takes place with the dry contact of elastic bodies.

Design of a computational model for multi-body contact of deformable bodies in the flowing fluid

The article deals with the design and testing of a computational model for multi-body contact of deformable bodies in the flowing fluid. The computational model will be designed to allow easy modify the impact area of deformable bodies and their shape. The computational model must allow the application of an endless cycle of bodies impact with the possibility of restarting and calculating the following time intervals for collision of bodies.

Comprehensive ensuring of quality of surfaces of details at centrifugal-planetary volume processing

The results of the system analysis of the set of input factors of the volumetric centrifugal-planetary processing, allowing to implement a comprehensive approach to the provision of quality processing parameters, are considered. A sequence of modeling processes ensuring the quality of surfaces during bulk processing is given. The results of modeling the contact of an abrasive working body with the surface of a workpiece with a microrelief are shown. The factors determining the stability of reliable achievement of qualitative indicators are noted. A dependence has been developed to determine the parameter of the surface roughness to be reduced, based on the results of modeling the contact between the surfaces of the working fluid and the workpiece by the finite element method. The experience of designing volumetric centrifugal processing operations on the basis of modeling is generalized. Methodical methods of technological preparation of manufacture for volumetric processing are offered.

Convergence Results and Optimal Control for a Class of Hemivariational Inequalities

The present paper deals with new results in the study of a class of elliptic hemivariational inequalities in reflexive Banach spaces. We start with an existence and uniqueness result. We complete it with a convergence result which describes the dependence of the solution with respect to the data. To this end, we use the notion of Mosco convergence for the set of constraints. Next, we formulate an optimal control problem for which we prove the existence of optimal pairs and state a convergence result. Finally, we exemplify the use of our results in the study of a two-dimensional boundary value problem which describes the frictionless contact of an elastic body with two reactive foundations.

Pronuclear pattern does not predict morphokinetics behavior in human embryos

The purpose was to investigate the correlation between pronuclei (PN) morphology and morphokinetic behaviors of derived embryos with time lapse monitoring (TLM) in assisted reproduction setting. Over time, PN morphology from PN appearance (PNA) to PN fading (PNF), PNF according to size, contact, number and position of nuclear precursor bodies (NPBs) within each PN and morphokinetics variables, including absolute time points, relative timing parameters, cleavage patterns and arrest rate, were evaluated using TLM. There were insignificant relationship between morphokinetics variables including tBP2, tPNA, tPNF, t2, t3, t4, t5, t6, t7, t8, S1, CC2, S2 and Z scoring according Z1 to Z4 (p > .05). Also, an insignificant relationship was noticed between uneven blastomeres, reverse cleavage embryos and Z scoring (p > .05). However, there were significant correlations between the rates of direct and arbitrary cleavage as well as arrested embryos and Z scores. Combined PN morphology and embryo kinetic evaluation were suggested in assisted reproduction programs.

Microbial barrier permeability and thermophysiological and mechanical properties of static dissipative woven fabric system

Some of the most significant properties of static dissipative woven fabric systems, in applications where contact of textile material and human body is present, beside antistatic properties are definitely microbial barrier permeability and thermophysiological properties. Application of such materials with associated properties is of great importance in bedding upholstery and comfortable apparel. Based on the conducted relevant tests, according to standardized and newly developed methods, it can be concluded that the such static dissipative woven fabric fulfils all the highly set criteria’s, resulting in a system that can, with certainty, provide the necessary health protection and comfort.

An investigation into the contact between soft elastic and poroelastic bodies rotating under load

This paper explores the contact of soft elastic and poroelastic bodies rotating under load and inspects the differences in load carrying capacity between the two types of material. Both materials have been widely used to describe the behaviour of biological systems such as articular cartilage in mammalian joints, however, we demonstrate here that there are fundamental differences between the responses generated in which the poroelastic response has an additional fluid contribution to the solid structural response. In order to produce the same load carrying capacity it is shown that the poroelastic material must deform more than an incompressible soft elastic material with the same stiffness and that the solid load generated by a poroelastic material is the same as a soft elastic material with a zero Poisson’s ratio.

Combined effect of surface microgeometry and adhesion in normal and sliding contacts of elastic bodies

In this study, models are proposed to analyze the combined effect of surface microgeometry and adhesion on the load–distance dependence and energy dissipation in an approach–separation cycle, as well as on the formation and rupture of adhesive bridges during friction. The models are based on the Maugis–Dugdale approximation in normal and frictional (sliding and rolling) contacts of elastic bodies with regular surface relief. For the normal adhesive contact of surfaces with regular relief, an analytical solution, which takes into account the mutual effect of asperities, is presented. The contribution of adhesive hysteresis into the sliding and rolling friction forces is calculated for various values of nominal pressure, parameters of microgeometry, and adhesion.

Influence of tangential displacement on the adhesion strength of a contact between a parabolic profile and an elastic half-space.

The adhesion strength of a contact between a rotationally symmetric indenter and an elastic half-space is analysed analytically and numerically using an extension of the method of dimensionality reduction for superimposed normal/tangential adhesive contacts. In particular, the dependence of the critical adhesion force on the simultaneously applied tangential force is obtained and the relevant dimensionless parameters of the problem are identified. The fracture criterion used coincides with that suggested by Johnson. In this paper, it is used to develop a method that is applicable straightforwardly to adhesive contacts of arbitrary bodies of revolution with compact contact area.

Influence of viscoelastic coatings on the contact of lubricated bodies

The contact of elastic bodies with viscoelastic coatings is considered, in the presence of lubrication. The one-dimensional Kelvin model is employed for the viscoelastic coatings. The pressure distribution in the lubricant layer and the layer thickness are investigated on transition from low to large loads.

Oblique collisions of baseballs and softballs with a bat

Experiments are done by colliding a swinging bat with a stationary baseball or softball. Each collision was recorded with high-speed cameras from which the post-impact speed, launch angle, and spin of the ball could be determined. Initial bat speeds were in the range 63–88 mph, producing launch angles in the range 0°–30° and spins in the range 0–3,500 rpm. The results are analyzed in the context of a ball-bat collision model, and the parameters of that model are determined. For both baseballs and softballs, the data are consistent with a mechanism whereby the ball grips the surface of the bat, stretching the ball in the transverse direction and resulting in a spin that was up to 40% greater than would be obtained by rolling contact of rigid bodies. Using a lumped parameter contact model, baseballs are shown to be less compliant tangentially than softballs. Implications of our results for batted balls in game situations are presented.