Applied Mechanics and Materials Vol. 772

Abstract: The paper describes possibilities to use industrially adhesive gripping elements in automatized handling processes especially for flat objects but also for objects slightly dissected according to height (e.g. sheets of glass, plastics, metals, plastic products etc.) which have dry, relatively clean, and smooth contact surfaces. It begins by analyzing results obtained in the field of designing combined vacuum-adhesive gripping elements, and the exclusively adhesive (passive) ones being suitable for technologically difficult handling conditions, e.g. in vacuum, as well. Furthermore, problems of the maximum carrying capacity of individual gripping elements being arranged parallel on a frame of a multi-element gripping head. A new concept of a compensation module of the gripping element position is presented as well, namely in relation to the head frame and to the handling object contact surface dissected according to height.

Abstract: It starts from a structural scheme of a mechanism with a triad and two successive conductive elements, and a kinematic scheme with ternary element and another element with void lengths is made. The relations to calculate the positions by contour method are written and the nonlinear algebraic system is solved by the method of successive elimination of the unknowns. There are determined the successive positions, the paths of some points and the variations of lifts, for different correlations between the laws of motion of the two conductive elements. It appears that there result paths and interesting laws.

Abstract: The functional constructive variants of the Hyprex and Comprex compressors with pressure wave built until the present are reduced in number. Starting from this ascertainment, the paper proposes to highlight the optimization on joint functioning of existing pressure wave supercharger models with internal combustion engines. This is possible due to the efficiency of the supercharging process, realized with such superchargers, which depends on the correlation grade between the rotational speed of the supercharger and the pressure of the exhaust gasses that enter in the compressor's channels, reason due to, a single supercharger model can be capable to supercharge efficiently engines with different characteristics, if the optimal values for the driving speed of the pressure wave supercharger are identified (according to the method proposed in the work) and adapted (according the level of energetic and/or ecologic performances that the engine should achieve) for each type of engine apart.

Abstract: Detection of damage in rails can be achieved by using ultrasonic guided waves. It is practical that these waves can propagate as lengthy as possible along the rail structure. In this work, the generation of adequate guided waves is considered by performing pertinent laser irradiation of the rail head. Special laser spots were applied through out-of-phase masks collocated on both sides of the rail. Simulation of this excitation configuration was performed by means of the finite element method. It was found that the proposed method enables to trigger sufficiently high stress pulses and generate adequate pattern of waves from a lot of other modes that are likely to exist for a common rail. These waves were found to be sensitive to small localized transverse like defects in the rail system.

Abstract: In this paper there are presented a series of methods and algorithms for signal processing (A-scan) and image processing (B-scan) which allow an easier and more accurate interpretation of the inspection results. The methods and the algorithms were tested for detection of a buried pipe, made of glass fiber polyester composite with a diameter of 1.3m, first when the survey conditions allowed only the scanning along the pipe, the most disadvantageous situation, but it has imposed by the configuration of the examined zone. After a few days of construction works, the site was prepared for inspection, orthogonally on the first scan direction.

Abstract: The detection of rotor position plays an important role in the motor speed-adjustment system. By analyzing the back-EMF method and its improved methods, we know the amplitude of back-EMF is too small to be detected when the motor run at low speed. A new detection method of rotor position has been proposed in this paper. It detects the zero crossing point of line terminal voltage difference to acquire the rotor position signal after a 90 degrees mechanical angle delay. The amplitude of line terminal voltage difference is large in wide speed range, so the rotor position signal can be accurately acquired in most situations. Simulation results proved that the new method can obtain the rotor position signal exactly in both high and low speed. It meets the wide speed range of motor.

Abstract: The present study deals with the application of the Magneto-Rheological (MR) fluid assisted semi-active damper as a replacement to the conventional suspension system in Maruti 800 car (source vehicle). MR fluid damper is designed, fabricated and automated with a microcontroller. This experimentation is carried out with real time instrumentation on the selected road profile as a vehicle dynamic approach. Results obtained from the travel imply that MR fluid suspension suppresses the vibrations more effectively than the existing passive damper system. The MR fluid dampens the acceleration and displacement of the piston to a greater extent thereby controlling the ride comfort.

Abstract: This study presents dynamic modeling and simulation of an air vehicle consisting of a body, gripper and a claw. This model is inspired from birds’ aerial hunting, while considering the extra degree of freedom associated with the claw. For a manipulator like a gripper, additional degree of freedom creates more flexibility for grasping. The main contribution of this paper focuses on the development of a model that is suitable for trajectory optimization in grasping phase. Mathematical representation of the system is developed based on the Newton-Euler approach in MATLAB-Simulink environment, considering the motion in vertical plane. The dynamic behavior of the system is evaluated by simulation in variety situations and sensitivity analysis is carried out to determine and characterize the parameters having the most and least effects on grasping. It is shown that the initial position of the gripper and the claw as well as the additional mass that is added to the system in grasping phase make considerable changes in the dynamics that necessitates the use of the control system. In addition, smooth trajectories and controls are obtained by adding friction to the system in order to avoid dynamic divergence.

Abstract: The purpose of this paper is to present some aspects regarding the computational model and simulation for three stage launch vehicle (LV) used to inject in orbit small size payload. The computational model consists in numerical simulation of LV evolution for imposed start conditions. The launcher model presented will be with six degrees of freedom (6DOF) and variable mass. The results analysed will be the flight parameters and ballistic performances. The discussions area will focus around the technical possibility to realize a small multi-stage launcher, end evaluate his performance using the developed model. From technical point of view, the paper is focused on ESA project “Study – concept, to achieve a Small Orbital Launcher through zonal cooperation - SOL

Abstract: In this paperwork we are studying the performance of a combustion process into a jet engine combustion chamber, more specifically the relations between excess of air, overall pressure ratio and inlet turbine temperature for a combustion reaction based on a jet A fuel. The study present a method of calculating the excess of air for a generalized combustion reaction based on Jet A fuel indicated by the general formula , for different temperatures of air, different temperatures of fuel and different inlet turbine temperatures. The result of this study is to achieve diagrams in which are presented the variation of air excess with engine parameters who participate in combustion process and to performed a computing program in which it is calculated the exactly value of excess of air for any outlet compressor temperatures, any inlet turbine temperatures and different fuel temperatures.