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Dietmar Schroeder - One of the best experts on this subject based on the ideXlab platform.
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Physical Foundation of a Recently Proposed Schottky-Contact Model
IEEE Transactions on Electron Devices, 2011Co-Authors: Dietmar SchroederAbstract:The goal of this correspondence is to supplement the Schottky-Contact Model proposed in “A Generalized Drift-Diffusion Model for Rectifying Schottky Contact Simulation,” IEEE Transactions on Electron Devices, vol. 57, no. 7, July 2010, with a solid physical foundation by rigorously rederiving it from an analytical solution of Boltzmann's equation in the boundary layer.
Matthew R W Brake - One of the best experts on this subject based on the ideXlab platform.
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an analytical elastic plastic Contact Model with strain hardening and frictional effects for normal and oblique impacts
International Journal of Solids and Structures, 2015Co-Authors: Matthew R W BrakeAbstract:Abstract Impact between metallic surfaces is a phenomenon that is ubiquitous in the design and analysis of mechanical systems. To Model this phenomenon, a new formulation for frictional elastic–plastic Contact between two surfaces is developed. The formulation is developed to consider both frictional, oblique Contact (of which normal, frictionless Contact is a limiting case) and strain hardening effects. The constitutive Model for normal Contact is developed as two contiguous loading domains: the elastic regime and a transitionary region in which the plastic response of the materials develops and the elastic response abates. For unloading, the constitutive Model is based on an elastic process. The normal Contact Model is assumed to only couple one-way with the frictional/tangential Contact Model, which results in the normal Contact Model being independent of the frictional effects. Frictional, tangential Contact is Modeled using a microslip Model that is developed to consider the pressure distribution that develops from the elastic–plastic normal Contact. The Model is validated through comparisons with experimental results reported in the literature, and is demonstrated to be significantly more accurate than 10 other normal Contact Models and three other tangential Contact Models found in the literature.
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The effect of the Contact Model on the impact-vibration response of continuous and discrete systems
Journal of Sound and Vibration, 2013Co-Authors: Matthew R W BrakeAbstract:Abstract Impact is a phenomenon that is ubiquitous in mechanical design; however, the Modeling of impacts in complex systems is often a simplified, imprecise process. In many high fidelity finite element simulations, an impractically large number of elements are required to Model the constitutive properties of an impact event accurately. As a result, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, an artificially large penalty stiffness, or a single degree of freedom constitutive Model for the impact dynamics that is specific to the type of materials involved (elastic, plastic, viscoelastic, etc.). In this paper, the effect of the Contact Model on the prediction of a system's dynamics is analyzed. In order to understand the effect of the impact Model on the system's dynamics, simulations are conducted to investigate a single degree of freedom system, a two degrees of freedom system, and a continuous system, each with rigid stops limiting the amplitude of vibration. Five different Contact Models are considered: a coefficient of restitution method, a penalty stiffness method, two similar elastic–plastic constitutive Models, and a dissimilar elastic–plastic constitutive Model. Frequency sweeps and parametric studies show that simplified Contact Models can lead to incorrect assessments of the system's dynamics. In the worst case, periodic behavior can be predicted in a chaotic regime. Additionally, the choice of Contact Model can significantly affect the prediction of wear and damage in the system, as is evidenced by the prominence of chatter and high amplitude responses.
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The Effect of the Contact Model on the Design of Mechanical Systems.
Volume 4: Dynamics Control and Uncertainty Parts A and B, 2012Co-Authors: Matthew R W Brake, Dannelle Sierra Aragon, Douglas J. Vangoethem, Hartono SumaliAbstract:Impact is a wide-spread phenomenon in mechanical systems that can have a significant effect on the system’s dynamics, stability, wear, and damage. The simulation of impact in complex, mechanical systems, however, is often too computationally intensive for high fidelity finite element analyses to be useful as design tools. As a result, rigid body dynamics and reduced order Model simulations are often used, with the impact events Modeled by ad hoc methods such as a constant coefficient of restitution or a penalty stiffness. The consequences of the choice of Contact Model are studied in this paper for a representative multiple-degrees of freedom mechanical system. Four Contact Models are considered in the analysis: a constant coefficient of restitution Model, two similar elastic-plastic constitutive Models, and one dissimilar elastic-plastic constitutive Model. The predictions of wear, mechanical failure, and stability are assessed for each of the Contact Models, and the subsequent effect on the system design is investigated. These results emphasize the importance of choosing a realistic Contact Model when simulations are being used to drive the design of a system.
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an analytical elastic perfectly plastic Contact Model
International Journal of Solids and Structures, 2012Co-Authors: Matthew R W BrakeAbstract:Abstract A new formulation for elastic-perfectly plastic Contact in the normal direction between two round surfaces that is solely based on material properties and Contact geometries is developed. The problem is formulated as three separate domains: the elastic regime, mixed elastic–plastic behavior, and unconstrained (fully plastic) flow. Solutions for the force–displacement relationship in the elastic regime follow from Hertz’s classical solution. In the fully plastic regime, two well supported assumptions are made: that there is a uniform pressure distribution and there is a linear force–deflection relationship. The force–displacement relationship in the intermediate, mixed elastic–plastic regime is approximated by enforcing continuity between the elastic and fully plastic regimes. Transitions between the three regimes are determined based on empirical quantities: the von Mises yield criterion is used to determine the initiation of mixed elastic–plastic deformation, and Brinell’s hardness for the onset of unconstrained flow. Unloading from each of these three regimes is Modeled as an elastic process with different radii of curvature based on the regime in which the maximum force occurred. Simulation results explore the relationship between the impact velocity and coefficient of restitution. Further comparisons are made between the Model, experimental results found in the literature, and other existing elastic–plastic Models. The new Model is well supported by the experimental measurements of compliance curves for elastic–plastic materials and of coefficients of restitution from impact studies, and in elastic-perfectly plastic regimes is demonstrated to be more accurate than existing Models found in the literature.
David E Orin - One of the best experts on this subject based on the ideXlab platform.
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a compliant Contact Model with nonlinear damping for simulation of robotic systems
Systems Man and Cybernetics, 1999Co-Authors: D W Marhefka, David E OrinAbstract:Contact Modeling is an important aspect of simulation of many robotic tasks. In the paper, a compliant Contact Model with nonlinear damping is investigated, and many previously unknown characteristics of the Model are developed. Compliance is used to eliminate many of the problems associated with using rigid body Models with Coulomb friction, while the use of nonlinear damping eliminates the discontinuous impact forces and most sticky tensile forces which arise in Kelvin-Voigt linear Models. Two of the most important characteristics of the Model are the dependence of the coefficient of restitution on velocity and damping in a physically meaningful manner, and its computational simplicity. A full mathematical development for an impact response is given, along with the effects of the system and Model parameters on energy loss. A quasistatic analysis gives results which are consistent with energy loss characteristics of a more complex distributed foundation Model under sustained Contact conditions. A foot Contact example for a walking machine is given which demonstrates the applicability of the Model for impact on foot placement, sustained Contact during the support phase, and the breaking of the Contact upon liftoff of the foot.
Louis Gagnon - One of the best experts on this subject based on the ideXlab platform.
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Influence of Tyre–Road Contact Model on Vehicle Vibration Response
Vehicle System Dynamics, 2015Co-Authors: Peter Múčka, Louis GagnonAbstract:The influence of the tyre–road Contact Model on the simulated vertical vibration response was analysed. Three Contact Models were compared: tyre–road point Contact Model, moving averaged profile and tyre-enveloping Model. In total, 1600 real asphalt concrete and Portland cement concrete longitudinal road profiles were processed. The linear planar Model of automobile with 12 degrees of freedom (DOF) was used. Five vibration responses as the measures of ride comfort, ride safety and dynamic load of cargo were investigated. The results were calculated as a function of vibration response, vehicle velocity, road quality and road surface type. The marked differences in the dynamic tyre forces and the negligible differences in the ride comfort quantities were observed among the tyre–road Contact Models. The seat acceleration response for three Contact Models and 331 DOF multibody Model of the truck semi-trailer was compared with the measured response for a known profile of test section.
Dong Sun - One of the best experts on this subject based on the ideXlab platform.
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A two-dimensional Contact Model between a multilayered solid and a rigid cylinder
Surface and Coatings Technology, 2019Co-Authors: Jingjing Zhang, Tingjian Wang, Chuanwei Zhang, Liqin Wang, Longcheng Yin, Liwei Zhan, Dong SunAbstract:Abstract Multilayer coatings are often reported in the papers on surface engineering and have been proved to be able to enhance the toughness, anti-wear and bonding strength, while an understanding of their mechanical behavior is essential to their optimal design and tribological application. In this paper, a two-dimensional Contact Model of a multilayered solid in line Contact with a rigid cylinder is developed based on a semi-analytical method. The frequency response functions, which are essential to producing the influence coefficients of the displacements and stresses components in the Contact Model with a conversion method based on the fast Fourier transform, are obtained by solving a system of linear equations concerning the unknown constants in the elastic field general solution of layered materials with a numerical method. The present Model is validated by comparisons of the Contact pressure and von Mises stress between the solutions of the present Model and those of the Hertz theory and the finite element Contact Model. The effect of the elasticity modulus changing mode as well as the layer number of the multilayered solid is further studied by utilizing the present Model.