Role of vortex-like motion in contact loading of strengthening coating. Movable cellular automaton modeling

Movable cellular automata (MCA) is an efficient numerical method in particle mechanics, which assumes that any material is composed of elementary objects interacting among each other according to many-particle forces. In this paper MCA method is applied to modeling deformation of 3D coating-substrate system under its contact loading by rigid indenter. Main attention of the research is focused on the role of vortex-like structures in the velocity fields in deformation of the strengthening coating and substrate. The mechanical properties of model coating correspond to multifunctional bioactive nanostructured film (TiCCaPON) and the properties of substrate, to nanostructured titanium. Loading is performed by hard conical indenter. The peculiarities of velocity vortex formation and propagation, as well as its interaction with structural elements are studied. One of possible application of the study is non-destructive technique for detecting nanoscale defects in surface layer of a material using frequency analysis of the force resisting to sliding of a small counter-body on the material surface, known as tribospectroscopy. Possibilities of this technique are studied based on 3D modeling by MCA method for the above mentioned coating with nano-pores. It is shown that specific peaks at the friction force spectrum correspond to different geometrical characteristics of the nano-pores

Modeling hydrodynamic self-propulsion with Stokesian Dynamics. Or teaching Stokesian Dynamics to swim

We develop a general framework for modeling the hydrodynamic self-propulsion (i.e., swimming) of bodies (e.g., microorganisms) at low Reynolds number via Stokesian Dynamics simulations. The swimming body is composed of many spherical particles constrained to form an assembly that deforms via relative motion of its constituent particles. The resistance tensor describing the hydrodynamic interactions among the individual particles maps directly onto that for the assembly. Specifying a particular swimming gait and imposing the condition that the swimming body is force- and torque-free determine the propulsive speed. The body’s translational and rotational velocities computed via this methodology are identical in form to that from the classical theory for the swimming of arbitrary bodies at low Reynolds number. We illustrate the generality of the method through simulations of a wide array of swimming bodies: pushers and pullers, spinners, the Taylor=Purcell swimming toroid, Taylor’s helical swimmer, Purcell’s three-link swimmer, and an amoeba-like body undergoing large-scale deformation. An open source code is a part of the supplementary material and can be used to simulate the swimming of a body with arbitrary geometry and swimming gait

Modeling and Control of the Automated Radiator Inspection Device

Many of the operations performed at the Kennedy Space Center (KSC) are dangerous and repetitive tasks which make them ideal candidates for robotic applications. For one specific application, KSC is currently in the process of designing and constructing a robot called the Automated Radiator Inspection Device (ARID), to inspect the radiator panels on the orbiter. The following aspects of the ARID project are discussed: modeling of the ARID; design of control algorithms; and nonlinear based simulation of the ARID. Recommendations to assist KSC personnel in the successful completion of the ARID project are given

Dynamic simulation of task constrained of a rigid-flexible manipulator

A rigid-flexible manipulator may be assigned tasks in a moving environment where the winds or vibrations affect the position and/or orientation of surface of operation. Consequently, losses of the contact and perhaps degradation of the performance may occur as references are changed. When the environment is moving, knowledge of the angle α between the contact surface and the horizontal is required at every instant. In this paper, different profiles for the time varying angle α are proposed to investigate the effect of this change into the contact force and the joint torques of a rigid-flexible manipulator. The coefficients of the equation of the proposed rotating surface are changing with time to determine the new X and Y coordinates of the moving surface as the surface rotates

Modeling the kinematics and Dynamics of Compliant Contact

In this paper, we discuss the modeling of the kinematics and dynamics of compliant contact between bodies moving in Euclidean space. First, we derive the kinematic equations describing the motion of the contact point when two rigid bodies are rolling on each other. Secondly, we extend these results to describe the motion of the closest points between two rigid bodies moving freely in space. Then, we use these results to model compliant contact between bodies, using a spatial spring and a damper to model energy stored and dissipated during contact