Papers by Keyword: Dynamics

Abstract: The Component-Wise approach (CW) is a novel structural modeling strategy that stemmed from the Carrera Unified Formulation (CUF). This work presents an overview of the enhanced capabilities of the CW for the static and dynamic analysis of structures, such as aircraft wings, civil buildings, and composite plates. The CW makes use of the advanced 1D CUF models. Such models exploit Lagrange polynomial expansions (LE) to model the displacement field above the cross-section of the structure. The use of LE allows the improvement of the 1D model capabilities. LE models provide 3D-like accuracies with far fewer computational costs. The use of LE leads to the CW. Although LE are 1D elements, every component of an engineering structure can be modeled via LE elements independently of their geometry, e.g. 2D transverse stiffeners and panels, and of their scale, e.g. fiber/matrix cells. The use of the same type of finite elements facilitates the finite element modeling to a great extent. For instance, no interface techniques are necessary. Moreover, in a CW model, the displacement unknowns are placed along the physical surfaces of the structure with no need for artificial lines and surfaces. Such a feature is promising in a CAD/FEM coupling scenario. The CW approach can be considered as an accurate and computationally cheap analysis tool for many structural problems. Such as progressive failure analyses, multiscale, impact problems and health-monitoring.

Abstract: For stability and impact reaction forces assessment of a quadruped robot during walking, a dynamic analysis is considered. For this purpose, a variant of a quadruped robot based on Jansen mechanism is presented. For interpreting the influence of the reaction forces from the ground during walking, the analysis was conducted with help of ADAMS software using a 3D model of the robot. Material specifications, forces and moments acting in the robot structure were considered. Graphical results obtained regarding the ground reaction forces are displayed. Also a reduced mass moment of inertia at the crankshaft is taken into consideration based on Lagrange motion equation and generalized coordinates.

Abstract: Using the main author's researches on the energies of acceleration and higher order equations of motion, this paper is devoted to new formulations in analytical dynamics of mechanical multibody systems (MBS). Integral parts of these systems are the mechanical robot structures, serial, parallel or mobile on which an application will be presented in order to highlight the importance of the differential motion equations in dynamics behavior. When the components of multibody mechanical systems or in its entirety presents rapid movements or is in transitory motion, are developed higher order variations in respect to time of linear and angular accelerations. According to research of the main author, they are integrated into higher order energies and these in differential equations of motion in higher order, which will lead to variations in time of generalized forces which dominate these types of mechanical systems. The establishing of these differential equations of motion, it is based on a generalization of a principle of analytical differential mechanics, known as the D`Alembert – Lagrange Principle.

Abstract: This paper presents new formulations on the higher order motion energies that are applied in the dynamic study of multibody mechanical systems in keeping with the researches of the main author. The analysis performed in this paper highlights the importance of motion energies of higher order in the study of dynamic behavior of fast moving mechanical systems, as well as in transient phase of motion. In these situations, are developed higher order time variations of the linear and angular accelerations. As a result, in the final part of this paper is presented an application that emphasizes this essential dynamic aspect regarding the higher order acceleration energies.

Abstract: The rheological viscous flow model of deformable, irreversibly compressible, porous body based on mechanics of continua, and creep theory of crystalline materials, is used to describe quantitatively the sintering of powder materials with pressure in isothermal and nonisothermal conditions. Densification of the porous body occurs under action of Laplace pressure, generated by surface tension, and applied pressure. The densification kinetics of porous metals and crystalline compounds in initial and intermediate stages of sintering with static external pressure represent nonlinear steady-state creep controlled by a climb dislocation mechanism in solid matrix forming porous material. Activation energies of this mechanism are consistent with the bulk diffusion. A diffusional creep controls the pressure sintering kinetics in a later stage. The rheological models of deformable viscoelastic bodies and the associated dynamic strain theory for viscoelastic irreversibly compressible bodies, based on the energy conservation law, enable a quantitative description of their densification under dynamic loading. At the same time it is taking into account the internal energy of deformable body. The solutions of dynamic systems involve the mechanical interaction of compacting machine with this body. The simulation of impact sintering of porous metals shows that the viscosity of the matrix, that forms the porous body, and the activation energy of viscous deformation dramatically decrease with increasing initial impact velocity. This promotes the compaction of the material to practically nonporous state and enhances its mechanical properties.

Abstract: This paper presents the mathematical and structural model as well as the verificationof a designed and built underwater crawler robot. The underwater crawler robot is designed to inspect elements of the water supply infrastructure, including pools, reservoirs and pipelines with round or square cross-sections. The virtual prototyping process is described as well as the various possible uses (design adaptability) depending on the optional accessories added to the vehicle. A mathematical model is presented to show the kinematics and dynamics of the underwater crawler robot, essential for the design stage. The mathematical model was used for a number of simulations and subjected to verification on a real object in two test environments.

Abstract: The work deals with the dynamic modeling and simulation of a 4-wheel steering vehicle. The steering system for the front wheels is a classical one (with pinion & rack), while for the rear wheels, a new design with rotational cam & translational follower has been developed by considering the integral steering law. The virtual prototype of the vehicle was modeled - simulated by using the MBS software environment ADAMS of MSC. The results of the dynamic analysis prove the performance of the proposed solution, in terms of handling and stability.

Abstract: This work is devoted to modeling of nonlinear dynamics of the rotating drill-string taking into account initial curvature and finiteness of deformations. The drill-string is compressed by variable axial force. The case of flat bending of the drill-string with an initial curvature is studied, where drill-string considered as a one-dimensional rotating rod of a symmetric cross-section. A nonlinear model is developed on the basis of the variational principle Ostrogradsky-Hamilton and the theory of finite deformations. The numerical analysis of the model is carried out. The influence of bending forms and initial curvature of the drill-string on the amplitude of transverse vibrations is established.

Abstract: The aforementioned proves that the grease flow in mould treatment equipment can be regarded as a regulation system with the input quantity by medium pressure p₁ above the grease level and with the output quantity by the grease flow speed.The utilization of treatment equipment for die casting of metal enhances both the working environment and work culture during die casting of metals. Application of grease flow regulation results in better repeatability of die casting cycle which positively influences the quality of castings.

Abstract: The contribution deals with the issue of the experimental assessment of the dynamic behaviour of the gear drives. The objective is to design and to realize the experimental station for dynamic tests of gear drives in an accelerated mode. Described is the idea of the experimental station design, the procedure of creating its mathematical model and the model for computer simulation.