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One of the current and widely used non-destructive testing methods for monitoring and determining the elastic properties of materials is nanoindentation. In this case, to interpret the test results, a non-trivial task arises of constructing an adequate mathematical model of the indentation process. As a rule, in many cases, analytical formulas are used that are obtained from an elastic linear formulation of problems about the introduction of a non-deformable stamp into a homogeneous elastic half-space. Currently, the numerical formulation of the problem makes it possible to obtain and use a numerical solution obtained taking into account the complete plastic nonlinear behavior of the material. In this work, a study of contact problems on the introduction of a spherical and conical indenter into an elastoplastic homogeneous half-space was carried out. To verify the numerical solution, the problem of introducing a spherical and conical indenter into an elastic homogeneous half-space was also solved and compared with known analytical solutions. Issues of convergence and tuning of numerical methods, the influence of plasticity and the applicability of analytical solutions are explored. Problems are solved numerically using the finite element method in the Ansys Mechanical software package.

Thermal contact damage is inevitable under the influence of friction. The frictional continuous contact model of the thermoelectric (TE) layer loaded by a rigid indenter is considered. Considering the complexity of friction and size effect, the nonlinear contact problem is reducedis transformed into solving the Cauchy singular integral equation (SIE) of the second kind by using the convolution formula and the superposition principle. The contact stress between the rigid indenter and the TE layer were affected by the external load, friction coefficient, TE material parameters. The results show that the softer TE layer can relieve the contact stress of the upper interface of TE. The change of friction coefficient and TE layer thickness can reduce the pressure at the rear end of the indenter. Properly adjusting these parameters can prevent the destruction and contact damage of the TE layer during the friction contact process. [ABSTRACT FROM AUTHOR]

Continuous contact models have been popular in representing contact forces between impacting bodies of a multibody system. These models consider the contact force to be the result of a logical spring-damper element between the contacting bodies that exists for a very short period. The simplified and approximated model for generating the contact force is then assumed to be a mass-spring-damper system. Therefore, three common parameters that these models require are the spring stiffness, damping coefficient, and the so-called effective mass. For systems containing one degree-of-freedom, classical methods based on the kinetic energy have commonly been used to determine the effective mass. However, for multiple-degree-of-freedom multibody systems that contain kinematic joints, the determination of the effective mass has not been adequately addressed in the literature. This paper proposes a simple method for computing the effective mass based on the concept of impulse–momentum balance. This approach is applicable to both constrained and unconstrained equations of motion regardless of the multibody system's number of degrees-of-freedom. [ABSTRACT FROM AUTHOR]

Analyzing the behavior of intelligent unconventional materials under diverse contact scenarios, in comparison to conventional materials, is a critical step in the initial design of engineering systems. This paper presents the development of analytical and numerical approaches for analyzing contact mechanics in a system comprising an orthotropic layer resting on a rigid foundation. Parametric analyses include the consideration of cylindrical and flat punch profiles. Analytical formulation utilizes integral transform methods to convert planar elasticity equations into a Cauchy-type singular integral equation of the second kind. A detailed description of the solution technique for the integral equation is provided, encompassing both the analytical formulation and the required discretization for obtaining the solution. Subsequently, a finite element approach (FEA) is employed to approximate contact bodies using a collection of finite elements, while contact boundaries are approximated by utilizing a set of polygons. Alternatively, the problem is addressed using the Multilayer Perceptron approach, a form of artificial neural network frequently applied in diverse machine learning applications, including scenarios involving contact problems. Finally, the resolution to the problem is achieved by employing the multilayer perceptron (MLP) method. The study yields determinations of contact stresses under the punch, the critical separation load resulting in the detachment of the orthotropic layer from the rigid foundation, and the corresponding separation distance. This analysis considers a range of dimensionless parameters and explored the behavior of diverse orthotropic materials. Comparisons between the results of the analytical method and computations from FEA and MLP reveal the exceptional accuracy attained by all three approaches. As the pioneer study employing three distinct approaches to examine continuous contact mechanics within an orthotropic layer under the influence of gravity, this research constitutes a valuable point of reference for upcoming scholars in the field. • Pioneers methods for orthotropic layer contact mechanics analysis versus conventional materials. • Finite element and Multilayer Perceptron methods show high accuracy in contact stress and separation load determination. • Parametric analyses explore cylindrical and flat punch profiles, revealing orthotropic material behavior under gravity. • Three distinct approaches provide comprehensive insights for future studies. • Insights from the study determine separation loads/distance, enhancing efficiency and reliability of structural designs. [ABSTRACT FROM AUTHOR]

The force-controlled end-effectors for industrial robots usually face the problems of low output force, poor control accuracy, or slow dynamic response. This paper presents a pneumoelectric force-controlled end-effector (PFE) for industrial robots to perform continuous contact operations. The end-effector possesses the advantages of both the pneumatic drive having large force-mass ratio and the electric direct drive having high force control accuracy and fast dynamic response. Through dynamic modeling and analyses, a force coordination control method based on impedance control is proposed for the PFE. The pneumatic cylinder is actuated by a semi-closed loop, while the voice coil motor (VCM) is controlled through a closed loop to improve the output force, accuracy, and dynamics. Impedance controller is utilized to reduce the impact caused by the critical contact between the tool and workpiece. Simulation analyses show that the force-mass ratio has increased, while the friction influence and overshoot has been reduced. In addition, prototype experiments verify the effectiveness of force control method and demonstrate that the PFE is able to achieve good performances such as control accuracy, step response, and dynamic bandwidth. Compared with the traditional pneumatic end-effector, the force control hysteresis is almost reduced from 41.9 to 0% without apparent creeping phenomenon. The rise time of the step response also decreases from 435 to 6.5 ms, and the bandwidth reaches 47 Hz. The PFE with force coordination control shows great potential in robotic deburring, grinding, and polishing applications. [ABSTRACT FROM AUTHOR]

Bu çalışmada, elastik yarı sonsuz düzlem üzerine oturan ve rijit iki blok ile yüklenmiş homojen tabakada sürekli temas probleminin karşılaştırmalı analizi yapılmıştır. Elastisite çözümden elde edilen sonuçlar, sonlu elemanlar yöntemi (SEM) kullanılarak elde edilen sonuçlarla kıyaslanmıştır. Problemde bütün yüzeylerin sürtünmesiz olduğu kabul edilmiştir. Problemin iki boyutlu SEM analizi ANSYS paket programı kullanılarak gerçekleştirilmiştir. Bloklar üzerindeki Q ile P yüklerinin farklı yükleme koşullarında analizleri yapılmıştır. Homojen tabaka ile elastik yarı sonsuz düzlem arasındaki ilk ayrılma yükü ve ilk ayrılma uzaklıkları (xcr, λcr) ile σy normal gerilmeleri elde edilmiştir. Elde edilen sonuçlar grafik ve tablo halinde gösterilmiştir.

Bu çalışmada, elastik yarı sonsuz düzlem üzerine oturan ve rijit iki blok ile yüklenmiş homojen tabakada sürekli temas probleminin karşılaştırmalı analizi yapılmıştır. Elastisite çözümden elde edilen sonuçlar, sonlu elemanlar yöntemi (SEM) kullanılarak elde edilen sonuçlarla kıyaslanmıştır. Problemde bütün yüzeylerin sürtünmesiz olduğu kabul edilmiştir. Problemin iki boyutlu SEM analizi ANSYS paket programı kullanılarak gerçekleştirilmiştir. Bloklar üzerindeki Q ile P yüklerinin farklı yükleme koşullarında analizleri yapılmıştır. Homojen tabaka ile elastik yarı sonsuz düzlem arasındaki ilk ayrılma yükü ve ilk ayrılma uzaklıkları (xcr, λcr) ile σy normal gerilmeleri elde edilmiştir. Elde edilen sonuçlar grafik ve tablo halinde gösterilmiştir.

A kinematic model is proposed for the interaction of two robots in synchronized operation with complex motion of an object. The inverse kinematic problem is solved for two manipulators connected by the object being manipulated. Formulas are derived for the controllable generalized coordinates in group control, with constraints corresponding to parallel manipulator operation. [ABSTRACT FROM AUTHOR]

Abstract In this study, the fundamental formulation for the continuous and discontinuous contact problems of a functionally graded (FG) layer lying on a rigid substrate are obtained without using superposition technique. The general expressions for the stresses and the displacements are derived in the presence of body forces using elasticity theory and Fourier integral transforms. As an application, the continuous and discontinuous contact problems of FG layer indented by a rigid cylindrical punch are considered. The contact problems are solved under the boundary conditions and the plane contact problems are reduced to the singular integral equations both in the case of continuous and discontinuous contact. The singular integral equations are solved numerically using Gauss-Chebychev integration formula and an iterative scheme is employed to obtain the correct contact width and critical load that satisfy the related conditions. Numerical results for critical load P cr , initial separation distance, the separation region in the discontinuous contact, contact width under the punch, contact stress distributions between the layer-punch and the layer-substrate are given. Highlights • Fundamental formulations for the continuous and discontinuous contact problems are derived without superposition technique. • The discontinuous contact problem including cylindrical punch is investigated first time in literature. • The critical loads that causes the separation are obtained for various parameters. • As the rigidity of the layer decreases bottom to the loaded top surface critical load increases. • The separation region increases when the flexibility of the layer and external load increase. [ABSTRACT FROM AUTHOR]

The continuous and discontinuous contact problem of a homogeneous layer loaded with three rigid flat blocks and resting on the elastic semi-infinite plane was investigated in this study by using the finite element method (FEM). All surfaces are assumed to be frictionless. The homogenous layer was loaded by means of three rigid flat blocks whose external loads are Q and P (per unit thickness in z direction). Two dimensional finite element analysis of the problem was performed using ANSYS package program. Analyzes were performed for loading conditions which are Q=P, Q=2P, Q=4P, Q=8P and Q=10P, and different values of block widths, distances between blocks and shear modulus. The initial separation loads and initial separation distances (λcrχcr) between the homogeneous layer and the elastic semi-infinite plane were determined for continuous contact condition. The length of the separation zone was obtained for discontinuous contact condition. In addition to these, normal stress distributions between the layer and the semi-infinite plane were determined for continuous and discontinuous contact conditions. As a result of the study, the analytical results, and the results of the finite element method were shown by comparing as graphs and tables. [ABSTRACT FROM AUTHOR]

In this paper, continuous and discontinuous contact problems for an elastic layer loaded by symmetrical distributed loads whose lengths are 2a on an elastic semi-infinite plane is solved using finite element method. The elastic layer also subjected to uniform vertical body force because of effect of the gravity. Thickness in z direction is taken to be unit. It is assumed that the contact surfaces are frictionless, only normal tractions can be transmitted through the contact areas. The contact along the interface between elastic layer and half plane is continuous if the value of load factor is less than a critical value. In continuous and discontinuous contact cases, the stress distribution on the contact interface are plotted for different dimensionless quantities. The finite element model of the problem is constituted using ANSYS software and analysis of the problem is carried out. Finally, the results obtained from the finite element solution are verified by comprasion with the analytical results. [ABSTRACT FROM AUTHOR]

The unilateral contact between an elastic rod and a rigid surface is encountered in numerous biological and engineering applications. Along continuous contacts, the centerline of the rod reflects the geometry of the constraining surface. This restriction of the rod axis to surface bound configurations enters its local equilibrium through a reaction pressure which ensures the compatibility between the deformation and the restraint geometry. The classic equations governing the static equilibrium of elastic rods are particularized to surface bound configurations by (i) specifying the location of the rod axis in terms of its coordinates in the parameter space associated with the constraining surface parameterization, and (ii) characterizing the orientation of its material frame through its rotation with respect to the surface normal. This formulation, which emphasizes the relations between the rod configuration and the geometry of the constraint, also leads to an expression for the reaction pressure. This approach is then validated on a spherical surface by comparing with known solutions for elastic curves, i.e., inextensible and twist free rods. [ABSTRACT FROM AUTHOR]

In this paper, continuous and discontinuous cases of a contact problem for two elastic layers supported by a Winkler foundation are analyzed using both analytical method and finite element method. In the analyses, it is assumed that all surfaces are frictionless, and only compressive normal tractions can be transmitted through the contact areas. Moreover, body forces are taken into consideration only for layers. Firstly, the problem is solved analytically using theory of elasticity and integral transform techniques. Then, the finite element analysis of the problem is carried out using ANSYS software program. Initial separation distances between layers for continuous contact case and the size of the separation areas for discontinuous contact case are obtained for various dimensionless quantities using both solutions. In addition, the normalized contact pressure distributions are calculated for both cases. The analytic results are verified by comparison with finite element results. Finally, conclusions are presented. [ABSTRACT FROM AUTHOR]

he contact problem for an elastic layer resting on an elastic half plane is considered according to the theory of elasticity with integral transformation technique. External loads P and Q are transmitted to the layer by means of two dissimilar rigid flat punches. Widths of punches are different and the thickness of the layer is h. All surfaces are frictionless and it is assumed that the layer is subjected to uniform vertical body force due to effect of gravity. The contact along the interface between elastic layer and half plane will be continuous, if the value of load factor, λ, is less than a critical value, λcr. However, if tensile tractions are not allowed on the interface, for λ > , λcr the layer separates from the interface along a certain finite region. First the continuous contact problem is reduced to singular integral equations and solved numerically using appropriate Gauss-Chebyshev integration formulas. Initial separation loads, λcr, initial separation points, xcr, are determined. Also the required distance between the punches to avoid any separation between the punches and the layer is studied and the limit distance between punches that ends interaction of punches, is investigated. Then discontinuous contact problem is formulated in terms of singular integral equations. The numerical results for initial and end points of the separation region, displacements of the region and the contact stress distribution along the interface between elastic layer and half plane is determined for various dimensionless quantities. [ABSTRACT FROM AUTHOR]