Papers by Keyword: Frequency

Abstract: This study proposes an experimental-numeric method to identify the viscoelastic properties of flax fibres reinforced composite laminate (flax/epoxide). The used method consists in identifying the evolutions of both loss factor and stiffness when vibrational frequency changes. In this way, several free-free symmetrically guided beams are excited on a dynamic range of 10 to 4000 Hz with sweep sine excitation focused around the 4-first’s modes. Fractional derivative Zener model is used to identify the on-axis ply complex moduli and describe the laminate dissipative linear behavior with the classical laminate theory. Results obtained on a quasi-isotropic laminate show that this model adequately predicts the vibrational behavior of the tested laminates.

Abstract: The paper analyses the vibratory motion of an electro-mechanical device acting medical equipment. The study is performed using the specific methods of the theory of the dynamical systems. The induced vibrations, their variation in time and the evolution of the system, as a function of the initial conditions, are studied, examining the fulfilment of the constraints prescribed in the literature, in order to achieve a maximal therapeutic benefit. The suitable operation ranges are determined, which establishes the starting point for the design of such equipment.

Abstract: In order to be used as food supplements, materials (medicinal and aromatic plants, other materials containing active principles, etc.) need to be chopped and sorted by size, depending on the field of use: herbal tea, suspensions, tinctures, etc. The paper presents the results of research on the sorting process of some materials containing active principles (yarrow, alfalfa and willow bark) using a sorting machine provided with 2 electro vibrators fitted on each side of the framework within which 3 sieves with a mesh size of: 2.15, 4 and 8 mm are fitted, changing the oscillation regime of the sieves by adjusting the angle of the electro vibrators, in order to identify the optimal sorting regime.

Abstract: Separation of materials is a fundamental technology for the production of machine parts. Division is involved in the overall use of the material and also impact on the overall production time. With the development of new materials increasing requirements for the construction, design and durability. This makes the development of new materials with higher mechanical, physical and chemical properties. These materials are difficult to machine, and this gives rise to the development of non-conventional technologies, which include water jet technology.

Abstract: AWJ abrasive water jet belongs to the unconventional methods of machining. Waterjet offers a number of advantages over other cutting methods. There is no heat or chemical material damage, high accuracy and precision, the ability to cut any material and others. Despite many advantages of AWJ has some technical elements that can be improved and optimized. This article deals with effect of vibration on the technological head and consequently wears. The aim of the experiments is to find the most appropriate feed rate, which extends the life of the technological head.

Abstract: Abrasive water jet technology is among the unconventional ways of machining. In today's modern and progressive era is often used for cutting and machining of various types of materials because of lower costs and environmental impact, as the cutting tool is water, in our case, with the addition of abrasives. Objective of the measurements was to evaluate the impact of vibration on the technological head in abrasive water jet technology in changing the selected technological parameters and the flow rate of technological head. In the given experiment, the used material - steel Hardox 500 with a thickness of 10 mm. The effort was to investigate the effects of changes in the speed rate of technological head (by speeds - 40, 200, 400 mm / min) on the size of the vibration acceleration amplitude and its frequency. Based on the measured values ​​of vibration to the technological head create the database and from it is evaluated the data in selected softwares (LabVIEW, SignalExpress and Microsoft Excel). Findings and conclusions are formulated on the basis of graphical dependencies, envelopes frequency spectra and comparison chart of envelopes.

Abstract: Anechoic chambers are widely used in performing EMC measurements according to the established EMC standards. As in space area, EMC measurement is critically important to ascertain all of electrical and electronic components in the satellite body will function correctly without fail during launching and operation mode. Recognizing the needs and importance of performing the EMC measurements, the shielding performance of the chamber should be prioritized to ensure the interference of electromagnetic wave from outside going to inside the constructed chamber does not exist. As to maintain the shielding element, periodic checking and inspection should be well planned by conducting a specific test. This paper outlines a series of procedures that are developed while running the test. The test will characterize the shielding performance at four (4) frequency ranges using different types of antenna set. Typical test results are gathered and presented at the measured frequencies. Based on the results, it is concluded that the shielding performance of anechoic chamber is standing in good condition at three (3) ranges of frequencies except for frequency of 10 kHz to 200MHz. Several steps are recommended to remove or eliminate the random noise.

Abstract: In recent years, very high cycle fatigue has become a major concern in design and durability of engineering components and structures such as railway wheels, rails, offshore structures, bridges, load bearings, etc. There are some factors which have been assumed to influence the fatigue behavior for metallic materials in VHCF regime. But most factors influencing the VHCF behavior have not been studied thoroughly. In order to deeply understand the essence of material fatigue, the experimental and theoretical aspects of the factors influencing on very high cycle fatigue for metallic materials should be studied further more. This paper deals with an overview on the effect of factors on the property in very high cycle fatigue regime. Research trends and some conclusions in this field are briefly discussed and obtained.

Abstract: The high temperature ultra-high cycle fatigue (UHCF) behaviors of DZ125 superalloy used in aero-engine turbine blades were systematically studied. The results show that the fatigue fracture still occurs above 10⁸ at the frequency of 20kHz, R=-1 and 700°C. There is a negligible frequency effect for the DZ125 superalloy, therefore, it is proposed that the ultrasonic fatigue testing could be expected as an accelerated fatigue testing method. Fatigue cracks originate from the subsurface of the specimens, where have no metallurgy defects or “fish eye” character. The crystal orientation change of the alloy is very little after fatigue.The maximum value changed for the elastic modulus of the alloy is about 30GPa after fatigue compared with that before fatigue.

Abstract: In this paper, APPJ (Atmospheric pressure Pules arc Plasma Jet) is used to generate a DC pulse source depositing GZO thin film under atmospheric pressure. Thus, no vacuum chamber needed leads to the cost downward. With scanning operation, makes single unit area into large size area. Several key process parameters have been studied, including the power supply voltage, DC pulse, the length of the nozzle extended head, and depositing gap to understand their relationship with the film quality and atmospheric plasma state.In this study, with adjusting DC pulse, the pulse frequency is found to have a great impact on the plasma state and the film quality. When the pulse frequency is near 25 kHz, lower sheet resistance can be retained. Besides, adjusting T_off time, the plasma and thin film quality are influenced more than T_on time. By changing the power supply voltage, the secondary-side voltage decreases with increasing of the instantaneous current; moreover, the plasma will become more intense.