Ceramic-metal Plates Research Articles

Large size shielded metal-ceramic cathodes

The technology for manufacturing large size shielded metal-ceramic cold cathodes is described. It has been shown that the use of a shielded metal-ceramic cathode allows to significantly increase the impedance of the vacuum diode and to form an electron beam of constant cross-sectional size or of the required size (up to 400 mm wide) with a fairly uniform electron beam current density distribution (≤15%).It has been found that the emission decline of the shielded metal-ceramic cathode, like that of the metal-dielectric cathode operating at a high repetition rate (≥100 pps), is significant at the beginning of the process and then slows down, allowing continuous operation for up to 40 h. Both cathodes require periodic cleaning of the plates, which is more difficult for metal-ceramic plates.At the same time, a metal-ceramic cathode works better at low vacuum, allowing twice as much current to be generated (in the same geometry) as a metal-dielectric cathode, while reducing the accelerating voltage by ∼15%. However, metal-ceramic plates are about 100 times more expensive to manufacture than dielectric plates for a metal-dielectric cathode.Therefore, the choice of cathode type for vacuum diode accelerators is not a trivial problem, but depends on many factors that must be taken into account in each case and for each radiation technology.

Effects of graphene-platelets reinforcement on the free vibration, bending, and buckling of porous functionally-graded metal-ceramic plates

This paper presents a first investigation of the mechanical behavior of porous functionally-graded material (FGM) plates reinforced with graphene platelets (GPls) nanomaterial. As a main purpose, we extend the research on GPls incorporation from single-component matrix materials to porous metal-ceramic FGMs. Four different through-thickness distributions of GPls and porosities were investigated. The effective elastic modulus of GPls-reinforced FGM was calculated using the Halpin-Tsai homogenization model, and the effect of porosities on elastic properties was considered by an exponential model that is more accurate than the common rule of mixture. A recent hyperbolic higher-order plate theory that satisfies the traction-free boundary conditions and a parabolic variation of shear stresses was used to model kinematics. The influence of various parameters was studied after method validation, and it was revealed that GPls not only can improve the stiffness and mechanical response of FGM plates, but can also eliminate the inherent transverse anisotropy of FGMs and uncouple the static response when dispersed in proper distribution pattern. This effect will result in zero mid-plane extension in bending conditions, in a similar behavior to isotropic plates.

Numerical modeling of shaped charge jet penetration into ceramic–metal double-layered medium using smoothed particle hydrodynamics

The prediction of the damage effects of shaped charge projectile to ceramic–metal multi-layered target is a challenging task to address. In this paper, the smoothed particle hydrodynamics (SPH) method is applied to simulate the penetration of the metal jet generated by the shaped charge detonation into ceramic–metal double-layered plates. The presented SPH model incorporates different equations of states. Moreover, the elastic-perfectly plastic constitutive model and the Johnson–Holmquist-II material constitutive model were employed for modeling the mechanical behaviors of the solid materials in this study. Firstly, simulation of the high velocity impact process of a ceramic ball on a ceramic–metal double-layered plate was conducted to validate the presented constitutive model. After the validation of the numerical model, simulations of penetration of a shaped charge into a double-layered ceramic–metal plate by using millions of SPH particles were conducted. The simulation results (perforation diameter and debris cloud) are in good agreement with the available experimental data, which shows that our in-house SPH solver is capable of tackling the shaped charge detonation and its penetration into multi-layered structures very well. Furthermore, the presented SPH model can reproduce different types of fracture patterns observed in experiments and their dynamic formation processes.

РАЗРАБОТКА СПОСОБА ВОССТАНОВЛЕНИЯ И УПРОЧНЕНИЯ ЛЕМЕХОВ ПЛУГОВ МЕТОДОМ ПАЙКИ МЕТАЛЛОКЕРАМИЧЕСКИХ ПЛАСТИН

The main defect that occurs when using plows is an abrasive wear of its ploughshares, the greatest wear of which is observed in the nose. When renestoring worn plowshares in order to significantly increase their service life, it is advisable to use technical ceramics. A plowshare with soldered ceramic-metal plates was chosen as the investigation object. The proposed investigation methodology included the control of plate adhesion, as well as bench and operational tests of experimental plowshares in comparison with serial ones. It has been established that the proposed type of connection «metal-ceramic plates−ploughshare» has high reliability and can withstand exceeding design loads by 3.8—4.9 times. As a result of the investigation, a new service- life-saving technology has been developed for the restoration and hardening of ploughshares by soldering using a hydrogen-oxygen flame, which allows one to increase the resource by 2-3 times, as well as reduce costs by 30−35% instead of purchasing new serial ploughshares due to using a cheap hydrogen-oxygen gas mixture.

Influence of porosity on the hygro-thermo-mechanical bending response of an AFG ceramic-metal plates using an integral plate model

In this project, the hygro-thermo-mechanical bending behavior of perfect and imperfect advanced functionally graded (AFG) ceramic-metal plates is analytically investigated using an integral plate model for the first time. The plate is assumed to be supported by a two-parameter elastic foundation. Because of the technical problems encountered in the manufacture of AFG, porosities and micro-voids can occur in AFG specimens, which can result in reduced density and strength of materials. Thus, due to the presence of porosity, a modified rule of mixture is adopted to predict the material properties of the AFG plates. The governing equations are deduced by adopting the principle of virtual and an integral plate model. The analytical Navier's method is considered to solve the obtained differential equations for simply supported AFG porous plate. The results obtained are checked by comparing them for non-porous and porous AFG plates with those available in the open literature. Finally, this work will help us to design advanced functionally graded materials to ensure better durability and efficiency for hygro-thermal environments.

An integral four-variable hyperbolic HSDT for the wave propagation investigation of a ceramic-metal FGM plate with various porosity distributions resting on a viscoelastic foundation

This work studies the dispersion relations of wave propagation in infinite advanced functionally graded (FG) ceramic-metal plates. A simple integral hyperbolic higher-order shear deformation theory (HSDT), with undetermined integral terms and only four unknowns, is used to formulate a solution for the waves’ dispersion relations. The effective functionally graded materials’ (FGM) properties follow the power-law with three different types of uneven porosity distributions. The effect of foundation viscosity is investigated by considering the damping coefficient in addition to Winkler’s and Pasternak’s parameters. The wave propagation’s governing equations are derived based on the present integral hyperbolic HSDT using Hamilton’s principle. The eigenvalue problem describing the porous FG plate dispersion relations resting on a viscoelastic foundation is analytically determined. The theory accuracy is validated by numerically comparing the results with previously published works. Finally, the influences of gradation power, porosity parameters, and the viscoelastic foundation parameters on wave propagation in an FG plate are examined and discussed.

Hygro-thermo-mechanical bending behavior of advanced functionally graded ceramic metal plate resting on a viscoelastic foundation

In this work, the bending behavior of an advanced functionally graded ceramic–metal plate subjected to a hygro-thermo-mechanical load and resting on a viscoelastic foundation is studied using a simple higher-order integral shear deformation theory. The power-law function in terms of volume fraction is used to vary the elastic material constituents through the plate's thickness. The in-plane displacement field uses a sine shape function which changes linearly through the plate thickness to calculate the out-of-plane shear deformation. Both the linear and nonlinear influence of temperature and moisture concentration on the bending response are investigated. For the first time, a three-parameter viscous foundation model is used to study the bending response utilizing the damping coefficient in addition to Winkler’s and Pasternak’s parameters. The governing equations are derived using the principle of virtual displacement, and the analytical solution is obtained by the Navier method. Non-dimensional numerical results is validated by existing results in the literature. A parametric investigation is established to discuss the effects of the power-law gradient index, temperature rise and moisture concentration, elastic foundation coefficients, and the viscoelastic damping coefficient on the FGM plate's bending response.

Development of device for extrusion of metal-ceramic plates

The article is devoted to the issues of production of thin-walled plates from metal-ceramic powders, including the development of special equipment for extrusion of nanoscale powder materials exposed to subsequent sintering. The original device is proposed for production by direct extrusion of thin-walled plates from metal-ceramic powder blend by the radial expansion upsetting method, which improves the quality of the parts structure through the formation of additional lateral shear deformations on the contact of the workpiece with the walls of the rectangular die.

FSDT-Based Isogeometric Analysis for Free Vibration Behavior of Functionally Graded Skew Folded Plates

In this paper, an isogeometric analysis (IGA) approach for free vibration analysis of functionally graded skew folded (FGSF) plates is presented for the first time. This method uses non-uniform rational B-splines (NURBS) as basis functions to provide a flexibility in refinement process. Furthermore, the IGA is able to exactly regenerate the geometry in comparison with the finite-element method (FEM), even at a coarse level of discretization. It is assumed that the mechanical properties of the FG metal–ceramic plates vary continuously through the thickness according to a power-law distribution. Also, the effective mechanical properties are captured by conventional rule of mixture. Regardless of the commonly used plates, the skew folded plates need to be modeled using two NURBS patches. The simple first-order shear deformation theory (S-FSDT) is employed to derive the equations of motion for each patch. After assemblage of the element matrices within each patch, the mass and stiffness matrices are modified and transformed to the global coordinates by employing an appropriate coordinate transformation. Subsequently, the bending strip method is utilized to accomplish the continuity conditions along the interface of the patches. The accuracy and reliability of the proposed IGA model are checked through comparison of the computed results with the available solutions in the open literature. The comparative study exhibits that the presented S-FSDT-based isogeometric formulation is promising to precisely predict the natural frequencies of FGSF plates with a low computational time. Eventually, a parametric study is performed and the variations of the natural frequencies with respect to the effective parameters such as crank angle, skew angle, length-to-thickness ratio, volume fraction and boundary conditions are examined.

Three-Dimensional Solution of the Free Vibration Problem for Metal-Ceramic Shells Using the Method of Sampling Surfaces

The possibility of using the method of sampling surfaces (SaS) for solving the free vibration problem of threedimensional elasticity for metal-ceramic shells is studied. According to this method, in the shell body, an arbitrary number of SaS parallel to its middle surface are selected in order to take displacements of these surfaces as unknowns. The SaS pass through the nodes of a Chebyshev polynomial, which improves the convergence of the SaS method significantly. As a result, the SaS method can be used to obtain analytical solutions of the vibration problem for metal-ceramic plates and cylindrical shells that asymptotically approach the exact solutions of elasticity as the number of SaS tends to infinity.

Bending analysis of FGM plates using a sinusoidal shear deformation theory

The response of functionally graded ceramic-metal plates is investigated using theoretical formulation, Navier's solutions, and a new displacement based on the high-order shear deformation theory are presented for static analysis of functionally graded plates. The theory accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The plates are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity of the plate is assumed to vary according to a power-law distribution in terms of the volume fractions of the constituents. Numerical results of the new refined plate theory are presented to show the effect of the material distribution on the deflections, stresses and fundamental frequencies. It can be concluded that the proposed theory is accurate and simple in solving the static and free vibration behavior of functionally graded plates.

An assessment of a non-polynomial based higher order shear and normal deformation theory for vibration response of gradient plates with initial geometric imperfections

In the present study, a new non-polynomial based higher order shear and normal deformation theory is proposed and implemented for the vibration response of geometrically imperfect functionally graded material (FGM) plates. The present theory accounts for nonlinear variation in the in-plane and transverse displacements, respectively in the thickness coordinate. This theory contains the trigonometric shear strain shape functions and having only four unknowns in the displacement field. It is variationally consistent and accommodates thickness stretching effects without employing shear correction factor. Two micromechanics models (Mori-Tanaka and Voigt) have been employed to determine the effective material properties of the plate, and are graded continuously through the thickness direction according to a simple power law and exponential law. The accuracy and efficiency of the proposed theory have been conferred by comparing the results with an existing 3D exact solution and various higher order theories. Frequency parameters with various side-to-thickness ratios, boundary conditions, imperfection sizes, volume fraction indexes and exponential indexes have been computed for perfect and imperfect FGM plate. It is found that the proposed theory is not only accurate but also simple in predicting the free vibration responses of functionally graded ceramic-metal plates.

Bending analysis of an imperfect FGM plates under hygro-thermo-mechanical loading with analytical validation

Flexural bending analysis of perfect and imperfect functionally graded materials plates under hygro-thermo-mechanical loading are investigated in this present paper. Due to technical problems during FGM fabrication, porosities and micro-voids can be created inside FGM samples which may lead to the reduction in density and strength of materials. In this investigation, the FGM plates are assumed to have even and uneven distributions of porosities over the plate cross-section. The modified rule of mixture is used to approximate material properties of the FGM plates including the porosity volume fraction. In order the elastic coefficients, thermal coefficient and moisture expansion coefficient of the plate are assumed to be graded in the thickness direction. The elastic foundation is modeled as two-parameter Pasternak foundation. The equilibrium equations are given and a number of examples are solved to illustrate bending response of Metal-Ceramic plates subjected to hygro-thermo-mechanical effects and resting on elastic foundations. The influences played by many parameters are investigated.

Computer modeling of processes penetration of metal and metal-ceramic plates

Numerical parametric simulation of penetration of aluminum plate by steel bullet is done. A three-dimensional model is constructed, the deformation of the plate is considered to be elastic-plastic. Further is modeling a projectile impacting on a ceramic layer backed by a metal plate. Is studied the two-layer metal-ceramic target with a different ratio of the thickness of the ceramic and steel. Is constructed a two-dimensional axisymmetric finite element Lagrangian model. The Johnson-Holmquist model of brittle fracture is used. Is simulated real boundary conditions of the system during penetration. Finite element models are prepared in Ansys, and key file is generated in the LS-DYNA. To locate the damaged section on impact is using thickening finite element mesh. To study the main stages of the bullets penetration into metal and metal-ceramic targets are used models, which provide visibility penetration.The main stages of bullet penetration and damage to a target are studied by analysis of plastic deformation and bullet velocity versus time. Also is studied absorption energy by the metal and metal-ceramic target. A comparison of the results of finite element solutions ANSYS / LS-DYNA with data reported in the literature is done.

Thermal stresses and deflections of functionally graded sandwich plates using a new refined hyperbolic shear deformation theory

A new refined hyperbolic shear deformation theory (RHSDT), which involves only four unknown functions as against five in case of other shear deformation theories, is presented for the thermoelastic bending analysis of functionally graded sandwich plates. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory presented is variationally consistent, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The sandwich plate faces are assumed to have isotropic, two-constituent material distribution through the thickness, and the modulus of elasticity, Poisson's ratio of the faces, and thermal expansion coefficients are assumed to vary according to a power law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic ceramic material. Several kinds of sandwich plates are used taking into account the symmetry of the plate and the thickness of each layer. The influences played by the transverse shear deformation, thermal load, plate aspect ratio and volume fraction distribution are studied. Numerical results for deflections and stresses of functionally graded metal-ceramic plates are investigated. It can be concluded that the proposed theory is accurate and simple in solving the thermoelastic bending behavior of functionally graded plates.

Geometrically nonlinear analysis of functionally graded plates using isogeometric analysis

Purpose – The purpose of this paper is to propose an efficient and accurate numerical model that employs isogeometric analysis (IGA) for the geometrically nonlinear analysis of functionally graded plates (FGPs). This model is utilized to investigate the effects of boundary conditions, gradient index, and geometric shape on the nonlinear responses of FGPs. Design/methodology/approach – A geometrically nonlinear analysis of thin and moderately thick functionally graded ceramic-metal plates based on IGA in conjunction with first-order shear deformation theory and von Kármán strains is presented. The displacement fields and geometric description are approximated with nonuniform rational B-splines (NURBS) basis functions. The Newton-Raphson iterative scheme is employed to solve the nonlinear equation system. Material properties are assumed to vary along the thickness direction with a power law distribution of the volume fraction of the constituents. Findings – The present model for analysis of the geometrically nonlinear behavior of thin and moderately thick FGPs exhibited high accuracy. The shear locking phenomenon is avoided without extra numerical efforts when cubic or high-order NURBS basis functions are utilized. Originality/value – This paper shows that IGA is particularly well suited for the geometrically nonlinear analysis of plates because of its exact geometrical modelling and high-order continuity.

NANOSTRUCTURING A SURFACE LAYER AND ITS INFLUENCE ON THE WEAR RESISTANT CHARACTERISTICS OF A SINTERED ALLOY IN METALL CUTTING

The paper displays the results of experimental research of nanostructuring of a surface layer of titanium carbide – nickel sintered alloy at electron-beam exposure of its surface. Data on characteristics of nanostructuring of a surface layer of metal ceramic alloy exposed to electron beam of plasma gas discharge containing argon (argon and nitrogen) and (xenon and nitrogen and their influence on friction coefficient on the surface of metal ceramic alloy and wear resistant properties of metal ceramic plates during cutting are given.

Elastic-friction side bearer for freight car bogie

Purpose. One should clarify the issues concerning the wear reduction of details of freight car side bearers, costs reduction for the worn details reconstruction, improvement the dynamic characteristics of railway vehicles and the increase of their movement safety. Methodology. Wear-resistant elements of the side bearers are made in the form of removable metal-ceramic plates, entrenched on friction planes. Findings. During operation due to pollution, wear of friction surfaces and other causes the power characteristics of side bearer may significantly vary, which adversely affects the dynamic qualities of bogies, and as a result the train traffic safety. Therefore, the solution proposed by the authors concerning the operation improvement of elastic frictional side bearers by means of their modernization is an urgent one. Originality. The design of the bogie side bearer of freight car was improved. Friction wedge was set on the spring; its inclined surface interacts with a support inclined platform of a plate through the plate with the durable elements in the form of metal-ceramic inserts. Practical value. The use of wear-resistant elements in the form of interchangeable metal-ceramic inserts will reduce the wear of connection joints of bogie and a freight car frame, improve its dynamic qualities. It will also decrease the costs for restoration of worn side bearers by friction.

Elasticity Solution for Bending Response of Functionally Graded Sandwich Plates Under Thermomechanical Loading

The thermomechanical bending response of functionally graded sandwich plates has been investigated by the use of the new four variable refined plate theories. The plate properties are assumed to be varied through the thickness following a simple power law distribution in terms of volume fraction of material constituents. The theory presented is variationally consistent, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The no symmetric sandwich plate faces are made of isotropic, two-constituent (ceramic–metal) material distribution through the thickness. The core layer is still homogeneous and made of an isotropic metal material. Several kinds of no symmetric sandwich plates are presented. The validity of the present theory is investigated by comparing some of the present results with those of the classical, the first-order, and the other higher-order theories. Field equations for functionally graded sandwich plates whose deformations are governed by either the shear deformation theories or the classical theory are derived. Displacement and stress functions of the plate for different values of the power-law exponent and thickness to-side ratios are presented. Numerical results for deflections and stresses of functionally graded metal–ceramic plates are investigated.

Bond strength of restoration materials used for dental ceramics repair

Aim. To assess the bond strength of composite material to ceramic surface of metal-ceramic-fixed dental prosthesis depending on the type of restoration systems used for chipped porcelain restorations. Methods. Bond strength of restoration material to porcelain coating surface were studied according to ISO 10477 issued at 01.10.2004. The surface of the ceramic-metal plates was polished by different methods depending on the restoration system used. Restorative material was applied using a template. Prepared samples were placed in a testing machine and loaded at a constant crosshead speed of 1±0.3 mm/min before separation, the load F at break was registered by an automatic recorder. Results. Similar bond strength results were revealed for restoration systems not requiring acid pickling of porcelain surface («Cimara», «Ceramic Repair») and restoration system including 9.5% hydrofluoric acid «Porcelain etch silane»: 17.993, 17.774 and 17.896 MPa respectively. Bond strength was much higher (25.278 MPa) if restoration system with 4% hydrofluoric acid was used. «Vertise™ Flow» restorative single-component material also provided significant bond strength - 24.315 MPa. Conclusion. The study showed the possibility of using a single-component restorative material to repair chipped porcelain tile coating metal-ceramic-fixed dental prostheses. For longer life of chipped porcelain tile coating restoration of dental prostheses, the use of restoration systems including 4% hydrofluoric acid is recommended.