Applied Mechanics and Materials Vol. 657

Abstract: The structural and parametric analysis presented in this work is understood as an inverse task of dynamics. The solution to this task is to obtain structure and parameters of a system meeting initial requirements. This synthesis may be used as a non-classical method of designing mechanical systems [1÷7]. The presented work extends this issue. Apart from designing a system consisting solely of passive elements, it also describes a subsystem, whose operation reduces undesired vibration of the primary system. The basic analysis which will be performed is to test the influence of applying electric elements on the primary mechanical set [1,3,6]. The analysis will be done on the example of system which were obtained while conducting the structural and parametric synthesis. In order to design a system including an active subsystem in the form of electric elements reducing vibration by means of a non-classical method of designing.

Abstract: For a centrifugal fan impeller the blade shape can be defined using two parameters: the blade angle and the blade width. There are different design methods depending on the assumption made on both the blade width and the blade angle. In this paper four design methods are presented: constant blade width and variable blade angle; hyperbolic blade width and variable blade angle; hyperbolic blade width and constant blade angle; linear blade width and variable blade angle. The sequential algorithm for solving the characteristic system of equations, which defines the blade geometry, is implemented in a MATLAB script file, for which principal code lines are explained. In the solving process of the characteristic system of equations for all four design methods considered, different relationships for relative velocity are obtained. The comparative graphical analysis of impeller blades obtained by all of the four design methods, as well as the blade geometry parameters is presented.

Abstract: The main objective of this work is to perform numerical analysis of an electromagnetic normally-closed direct-acting ball valve with cylindrical seat. A functional diagram is developed using the MATLAB/Simscape/SimHydraulics programming language. The principal elements of the functional diagram are: the fixed-displacement hydraulic pump, the ball valve which is driven by an electromagnetic actuator, the pressure-relief valve, pressure and volumetric flow rate measuring devices and the hydraulic pipes. Two sets of analyses are performed, the first one for an ideal case, without the effects that are associated with the hydraulic pipes and the second one for the real case, with these effects. The valve flow factor is presented, comparatively, for both cases, as well as the volumetric flow rates through the ball valve and the pressure relief valve, and finally the pressure drop in the valve.

Abstract: This paper presents a new type of actuator that uses the properties of a magnetorheological fluid. This actuator allows you to control the speed of a mechanical element and its positioning .The paper shows the conceptual model of the item, the schedule of experiments and their results. There are piston-cylinder type actuators that use magnetic fluid and have internal parts in relative motion. We propose an actuator does not have internal parts in relative motion and neither internal seals. There are shown the results obtained for the mechanical parameters of a new type of actuator with elastic elements, with linear motion. This actuator uses magnetorheological fluid properties. There are presented the constructive elements of the actuator, the properties of the magnetorheological fluid, the calculation procedure of the hydraulic and mechanical parameters and the obtained results. The results confirm the possibility of using it in various technical applications.

Abstract: The crash-boxes are thin-walled structural components with rectangular cross-section which are utilized in the construction of the resistance body structures in the auto industry. This components can be manufactured from various materials including homogenous steel sheet metals, tailor welded blanks (TWB) or even composite materials. The benefits of using TWB were shown in numerous studies before and they are not the main purpose here.This research focuses on the collapse behaviour of TWB thin-walled structures with rectangular cross-section subject of impact loadings. The main objective is to design a crash-box which allows the absorption and dissipation of great kinetic energy constituting better resistance structures for car bodies.After analysing the resulted data, a few aspects regarding the TWB crash-boxes were revealed and some conclusions could be suggested: the weld line generates a barrier like zone which delays in some manner the propagation of the progressive buckling levelling the mean crash load; no flange crash-boxes presented best results regarding the mean crash load even if the data were very close to the other crash-box types. Furthermore, the peak crash load was at maximum level comparing with the other crash-box types. This collapsing behaviour of the no flange crash-boxes could be assigned to the fact that the bonded sides of the structure work like double walls into the same cress-section and is not really affecting the asymmetric crash mode of the structure.

Abstract: This Paper Aims from the Simulation Tests to Highlight the Influence of the Diameter and Material Quality, Reflected by the Flow Limit of the Pipe and the Quality and Technological Parameters at the Bending under Pressure of the Pipes. from Literature, those Quality Parameters which Characterize a Correct Bending are: the Ovality of the Transversal Section, the Variation of the Wall Thickness or Eccentricity, the Lack of Whetstones, the Resistance in Function of the Bent Pipe. Pipe Material Characteristics Influence the Quality Parameters of the under Pressure Modeling Process, in the Sense that at the Materials with Small Flow Limit, Ovality or Variation of the Wall Thickness are Small. at Pipes under Pressure Modeling, Ovalities and Variation of the Wall Thickness are in Permissible Limits Valid Recommended for Domains without Special Precision Restrictions.

Abstract: The paper presents the use of synthesis methods to determine the parameters of passive vibration reduction in mechanical systems. Passive vibration reduction in a system is enabled by units called dampers whose values are determined on the basis of the method formulated and formalized by the authors. The essence of the method are, established at the beginning of a task, dynamic characteristics in the form of the resonance and anti-resonance frequencies, and amplitudes of displacement, velocity or acceleration of vibration.

Abstract: The paper presents an analytical investigation of the effect of the tooth wear on the dynamic transmission error of helical gear pairs with small number of pinion teeth. Firstly, the dynamic analysis is conducted to investigate only the effect of the time-varying mesh stiffness on the variation of dynamic transmission error along the line of action. Then, the tooth wear effect on the dynamics of helical gear with small number of pinion teeth is being researched. In the analysis, instantaneous dynamic contact analysis is used in wear depth calculations. A comparative study was performed to investigate the relation between total contact ratio, mesh stiffness and dynamic transmission error of helical gear pairs with small number of teeth.

Abstract: This paper presents two virtual devices made to determine the behavior of the bullet before, during impact and after the collision using different materials. First device was based on a pendulum and second was made with springs. The idea of making these virtual devices was to transform the kinetic energy of the projectile before the collision in a potential energy after impact. The difference between these two types of energies was going to deformations phenomena.

Abstract: The research of subsystems establishes the foundation to complex systems analysis with cascade structure. Analysing the diagrams of characteristics of confirmed system it has been determined that in case of approximate method the resonance frequencies cover with those which have been determined with exact method. However the values of the characteristic in other areas are different. The main aim of the paper is to study the dynamic characteristic of the discrete continuous mechatronic system determined by exact approximate, that means Galerkin's method for torsionally vibrating complex mechanical subsystems. The system composed from many subsystems having the same length and variable cross section, loaded by the focused moment was analysed. The main subject of deliberation was to determine the flexibility of the mechanic system with constant cross section using the exact and approximate Galerkin's method. Next the method comparison and the correction of approximate method where made. As far as the mechatronic system flexibility determinations concerned the Galerkin's method has been chosen. The analysis of subsystems of mechatronic and mechanic complex systems is however the introduction to the synthesis of torsionally vibrating mechatronic systems with assumed frequency spectrum.