Iskanje po katalogu digitalne knjižnice

Opis: In order to reduce the overall mass of the product, an improved variant of the engine oil suction pipe in hybrid design is developed and analysed as part of this paper. The vibration fatigue analysis of a simple all-metal suction pipe and the new hybrid suction pipe variant is derived using computer FEA simulations and vibration measurements on the shaker. The hybrid design of the technical components makes it possible to combine different types of materials in order to achieve the best possible properties and behaviours for the components under the influence of external loads. In our case, we combine a suction pipe made of S235JR mild steel with a 3D-printed polyamide intake funnel featuring a grid designed to prevent particles from entering the engine’s lubrication circuit. This design reduces the mass and shifts the centre of gravity closer to the attachment point of the pipe, as well as to the engine crankcase, which has a positive effect on the values of natural frequencies and vibration amplitudes. The main objective of such a hybrid suction pipe is precisely to reduce vibrations, and thus extend the service life of the components.
Ključne besede: oil suction pipe, vibration fatigue, failure analyses, experimental testing, numerical simulations
Objavljeno v DKUM: 26.02.2024; Ogledov: 641; Prenosov: 641
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Opis: This research presents a new approach aiming to reduce gear vibration as well as its weight by modifying the gear body structure. The primary objective was to reduce vibration and noise emission of spur gears. For this purpose, a solid gear body was replaced by a cellular lattice structure, which was expected to raise the torsional elasticity of the gear body. The cellular lattice structure was designed and optimized by FE-based topology optimization software CAESS ProTOp, which is based on strain energy control. For experimental purposes, the optimized gear was produced from Titanium alloy Ti-6Al-4V ELI by using Selective Laser Melting technique. A polymer matrix was added to increase the damping of the structure. In order to test the gears, a new test rig with closed loop was conceived, designed and produced. The test rig is equipped with two gear pairs: with the tested one and with the driving one. The gears have been run and tested at different speeds and torque. The acceleration, strain and sound pressure of a running gear pair was measured. The final processing of the signal was done by a specially developed software based on LabView. By employing the fast Fourier transformation the time signal of acceleration, strain and sound pressure has been converted to the frequency spectrum and time frequency spectrogram. The results obtained by testing the solid and cellular lattice gear body were compared. It was experimentally confirmed that the cellular lattice structure of a gear body and addition of a polymer matrix may significantly reduce the vibration.
Ključne besede: Gear vibration, cellular lattice structure, topology optimization, test rig
Objavljeno v DKUM: 27.02.2018; Ogledov: 2496; Prenosov: 259
Celotno besedilo (13,76 MB)

Opis: The vibration behaviour of an emergency gate situated on a horizontal-shaft Kaplan turbine is studied. The analysis and transfer of the dynamic movements of the gate are quite complex. In particular the behaviour is examined of the emergency gate for the case when the power unit is disconnected from the system or there is a breakdown of the guide vane system at the moment when the maximal head and capacity are achieved. Experimental-numerical methods both in the time domain and in the frequency are employed. Natural vibrations characterize a first zone, corresponding to relatively small gate openings. As the gate opening increases, the vibration behaviour of the gate becomes increasingly dependent on the swirl pulsations in the draft tube of the turbine. Finally, the data transfer from the model to the prototype by use of the dinamic similitude law is discussed.
Ključne besede: water turbines, emergency gates, vibrations, vibration measurement
Objavljeno v DKUM: 15.06.2017; Ogledov: 1393; Prenosov: 367
Celotno besedilo (2,45 MB)
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Opis: A valve gear system is currently more or less a classical mechanical system in a majority of diesel engines. In our case, diesel engine durability test was carried out incorporating a conventional valve gear. After the 3000-hour engine test, the manifestations of an intensive wear detected on the exhaust side of the valve gear. The wear of the exhaust cam was particularly intensive right under the top. As evident from dynamical analysis and experimental data of the valve gear the loads are excessive mainly on the exhaust cam. The assessment of the minimum oil film thickness at the top of the exhaust cam does not provide any favorable results. As the largest loads are exerted at the top of the cam, where the highest wear was measured, it is necessary to reduce the normal stresses and improve the lubrication properties. Dynamic valve gear analysis was performed in order to estimate cam wear intensity and to compare the new cam designs with the existing ones. The model of the actual valve gear design can be represented by means of the partial differential equations. We used a vibrational system with three degrees of freedom. Partial differential equations were solved by means of finite differences and Runge-Kutta methods. Vibrational analysis allows studying kinematic and dynamic behavior of the nonlinear spring and nonlinearity of the damping forces in the valve gear system. The presented theory will be applied in the future research works for determining the conditions for chaotic behavior of the valve gear system. The dynamic model of the valve gear was used to analyze the causes of the excessive wear. Since the cam, designed in accordance with the polysine curve, offered too few possibilities for an optimum cam profile, we wanted to manufacture a completely new type of cam with more possibilities for an optimum adjustment. At the same time, we attempted to summarize some findings on the dependence of the cam design on the fuel consumption and valve gear noise. Thereby a new MULTICAM cam was developed. Contrary to the conventional theory of polysine cam, the motion in the MULTICAM cam can be written by means of seven curves. The analysis of Hertz pressures provides more favorable results for the MULTICAM cam profile. By using the new cam profile the Hertz pressures were substantially reduced. The top of the cam is subjected to the lowest loads with the MULTICAM curve shape. In spite of a higher contact force the normal stresses are lower mainly due to the higher radius of cam curvature. Dynamic analysis demonstrates that both newly designed cams exhibit lower stresses at the top of the cam and better lubrication properties, whereas the flow geometrical cross-sections and the other control values remain similar for all three cam versions.
Ključne besede: disel valve gear vibration, nonlinearity, cam design, valve gear dynamics
Objavljeno v DKUM: 05.06.2012; Ogledov: 2609; Prenosov: 43
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Opis: Accurate position tracking control of a linear belt-driven servomechanism can cause vibrations in the drive response due to compliance and elasticity introduced by force transmission through the belt. This paper proposes a new control algorithm that has been designed by Sliding Mode Control theory. Though it has been proved to assure robust and vibration-free operation, position error peaks still appear at velocity reversals due to nonlinear friction phenomenon. Thus, the control scheme has been extended by asymptotic disturbance observer. The experiments presented in the paper show improved position tracking error response while maintaining vibration suppression.
Ključne besede: motion control, disturbance observer, sliding mode control, timing-belt drive, vibration suppression
Objavljeno v DKUM: 31.05.2012; Ogledov: 2274; Prenosov: 111
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