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Abstract

Owing to the distinguished properties Metal Matrix Graphite Hybrid Composites (Al/SiC-MMC-Gr) are used in various applications. This paper deals with the utility of Taguchi and response surface methodologies for the prediction of surface roughness in tuning of these materials with PCD tool. The cutting parameters effect on surface quality is analyzed and an empirical model with respect to turning parameters is established using response surface method. The most important parameter that influences the turning Al/SiC-MMC-Gr is feed. The measured and predicted results are approximately equal, which proves that, model is to be used for predicting surface finish in turning of these composites. Validation experiments have been used to confirm the predicted results.

Abstract

The swash plate type compressor utilized in car air conditioning devices and cooling system was analyzed in this study. Proper dynamic behavior of the components in such a compressor affected the correct functioning of the whole system. The aim of the study was to identify the characteristics of the main motion components in the swash plate–slippers–piston assembly of the compressor and to estimate the friction torques in its bearings. Some models of this assembly are elaborated and presented in the paper. The main components of slipper complex motion were identified, such as reciprocal motion along the axis of piston, rotation around piston axis, and short-time rotation around its own axis. Friction torque in axial bearing was higher than in journal bearing and varied with the rotational angle. Friction torques in journal bearings varied with the rotational angle and had different courses for two bearings of the compressor.

Abstract

The article presents an energy analysis of a real suction-pressure unit of a high-efficiency radial piston pump. This pump can be used in small hydropower plants, where, together with a variable displacement hydraulic motor, it would form a hydrostatic transmission. The main advantage of this solution is the possibility of a stepless, automatic change of gear ratio during its operation, which allows an increase of the efficiency of power generation in a hydropower plant. Mathematical models of friction and resistance of flow through self-acting and geometrical deformations of chambers and piston under stress field are presented. In addition, mass, volume, and energy balance calculations were computed for the ideal unit and pressure losses were determined. Derived indicator diagrams for each chamber of the ideal suction-pressure unit served to analyze the technical work of occurring processes. The paper also presents the formulation of total efficiency of the unit. Lastly, the experimental procedure is presented, according to which it is possible to register the most important parameters of the proposed model.

Abstract

The paper presents the results of experimental determination of the Surface Geometrical Structure (SGS) parameters and tool wear during turning the polymer concrete. Until now, all literature reports have shown that the smoothness and roughness of the mineral cast surface was obtained directly from the mold. However, new applications of polymer concrete, even for some parts of the machine tools, forced the producers to carry out machining, which would improve the parameters of the surface layer. The topic of machining ceramic-based composite materials is a new chapter in the field of machining, which has not been sufficiently researched so far. The article describes the process of experimental determination of dependence of surface layer and tools wear parameters from cutting parameters during longitudinal turning of polymer concrete. The turning was carried out using plates made of a cubic boron nitride (CBN). After machining, the surface roughness and the maximum width of the flank wear were measured. On this basis, the mathematical model of the surface layer and tools wear parameters versus cutting parameters were defined. The authors also attempted to explain the phenomena occurring in the machining zone using variable cutting parameters. Microscopic pictures of CBN plates after machining were also performed. After the study, the final conclusions about the machining of mineral cast material were formulated.

Abstract

An active method of vibration control of a smart sandwich plate (SSP) using discrete piezoelectric patches is investigated. In order to actively control the SSP vibration, the plate is equipped with three piezoelectric patches that act as actuators. Based on the classical plate theory, a finite element model with the contributions of piezoelectric sensor and actuator patches on the mass and stiffness of the sandwich plate was developed to derive the state space equation. LQR control algorithm is used in order to actively control the SSP vibration. The accuracy of the present model is tested in transient and harmonic loads. The applied piezoelectric actuator provides a damping effect on the SSP vibration. The amplitudes of vibrations and the damping time were significantly reduced when the control is ON.

Abstract

The article presents an original method of communication and data exchange in a robotic machining station consisting of two robots, a positioner and a 3D optic scanner. The task of one of the robots, equipped with a 3D optic scanner, was to receive point cloud of a detail (mould) attached to the positioner table. After detail digitalisation, the received point cloud was adjusted to (compared with) a model detail in the form of a CAD file in the Atos Professional software. In the software, casting material excesses were received in places selected on the detail. Values of the excesses and their coordinates were saved in the script and sent to the robot controller using TCP/IP protocol. The other of robots, equipped with the force control addition and the option of obtaining various processing tools, received sent excess and its coordinates. The other robot adjusted the processing parameters to random excesses, the value of which was received from measurements of the optic scanner of the first robot.

Abstract

The focus of this paper is the design of a self-maintenance orbit using two natural forces against each other. The effect of perturbations due to Earth's oblateness up to the third order on both the semi-major axis and eccentricity for a low Earth orbit satellite together with the perturbation due to air drag on the same orbital parameters were used, in order to create self-maintenance orbits. Numerical results were simulated for a low earth orbit satellite, which substantiates the applicability of the results.

Abstract

The synthetic jet actuators are one of the most investigated types of actuators used in heat transfer and active flow control. The energetic efficiency of actuators is a key parameter determining the possibility of device use. The actuators with two or more diaphragms have higher efficiency than the actuators with only one. The paper presents the investigations of the acoustic synthetic jet actuator with two opposite diaphragms. In the paper, synthetic jet velocity, Reynolds number and the energetic efficiency as a function of oscillating actuator frequency, for a different cavity, orifice configuration and one real input power P 0 = 2 W were studied. The possibility of theoretical calculation of first and second resonance frequency were checked. The coupling ratio for actuators was calculated. The maximum energetic efficiency was η = 8.67% and Reynolds number Re = 8503. The possibility of using the same dependencies and rules during the design of actuators with two opposite diaphragms as in the case of actuators with one diaphragm was demonstrated. The results may be useful in the design of the actuators of the two membranes.

Abstract

Chatter is a self-excited vibration which depends on several parameters such as the dynamic characteristics of the machine tool structure, the material of the work piece, the material removal rate, and the geometry of tools. Chatter has an undesirable effect on dimensional accuracy, smoothness of the work piece surface, and the lifetime of tools and the machine tool. Thus, it is useful to understand this phenomenon in order to improve the economic aspect of machining. In the present article, first the theoretical study and mathematical modeling of chatter in the cutting process were carried out, and then by performing modal testing on a milling machine and drawing chatter stability diagrams, we determined the stability regions of the machine tool operation and recognized that witch parameter has a most important effect on chatter.

Abstract

The study of reliability is an important part of engineering design process which forms the basis of analysis and judgment on future performance of the product. Since the future couldn’t be predicted with an absolute certainty, the nature of reliability would lead us to probability theory and uncertainty modeling. The quantitative calculation of this parameter for mechanical systems within different steps of production requires an analytical and systematic approach which has been focused in this paper. The proposed approach has been applied for calculating reliability of a clutch system as a case study. The system reliability in this work is determined based on the block diagram method as a function of individual component reliabilities which are calculated by statistical analysis of life test results. Using Weibull model, reliability of a typical clutch system has been formulated based on durability bench test and results has been interpreted to estimate field reliability.