Papers by Keyword: Damping

Abstract: Paralleling SiC MOSFETs in high-power modules introduces overvoltage and oscillation risks due to parasitic capacitances and inductances. This study presents a 200 kW EV inverter module co-designed at the device and packaging level to ensure switching reliability under harsh automotive conditions. At 800 V, the planar SiC MOSFET maintained stable gate voltage, while a benchmark trench device module experienced severe ringing and failure. Kelvin-source structures and internal gate resistors mitigated parasitic turn-on, and device-level optimizations—including a 0.5 µm foundry technology, silicide gate, and hexagonal cell layout—improved body-diode performance, together with the channel mobility, blocking voltage, and minimized on-resistance and switching losses. The resulting AEPR25B12C1STJN module demonstrated effective resonance damping, matched the performance of commercial trench module FS03MR12A6MA1B in static and dynamic tests, and achieved 98% AC efficiency with over 200 kW output at 150 °C junction temperature.

Abstract: This research developed a performance improvement of power transmission system to enhance performance during line disturbance using model Predictive control (MPC) control scheme. This research work was implemented using MATLAB 2023a. However, the parameters of these controllers are usually adjusted based on a linearized model of the power system, which typically depends on the system's operating point or state. To assess the performance of the developed scheme, multiple simulation studies were carried out under conditions where the voltage magnitude of the infinite bus and the transmission line reactance changed due to faults at the infinite bus and sending terminals. The results from the waveform analyses indicate that the dynamic characteristics of the system under investigation have significantly improved. settling time, at post fault of the transmission and from fault recovery settled time to its stable state value of 1.8sec compared to 2.8sec with minimal control effort that fluctuated between faults and system stability before settling time at the shortest time value of 2. 6305s in 2.42s compared to 4.28, in 1.92s compared, and 3.32s.

Abstract: The article is devoted to the development of the composition of a thixotropic magnetorheological fluid and a laboratory setup for determining the properties and characteristics of magnetorheological fluids. The magnetorheological fluid was developed on the basis of copolymers of methyl methacrylate and n-butyl methacrylate, a mixture of diethylbenzenes, dioctylphthalate, oleic acid, and carbonyl iron of the P-10 grade. To impart thixotropic properties to the magnetorheological fluid, a 1% solution of modified urea is added. For the study of magnetorheological materials, a laboratory setup was developed that allows one to measure the yield stress, plastic viscosity, flow curves, magnetorheological characteristics and the magnetization curve. The setup includes two hydraulically connected cylindrical vessels and one external cylindrical vessel filled with the investigated magnetorheological fluid between two poles of a powerful magnet. The shear stress is determined through the magnitude of the viscous friction force that occurs when a load immersed in the liquid is evenly lifted, and the strength and induction of the magnetic field are determined by means of two Hall sensors.

Abstract: The motion of a rigid sphere located at tissue-mimicking material interface in response to a dynamic force of short duration for the purpose of the determination of material viscoelastic properties was investigated in this study. The experiments were performed using a rigid sphere located at tissue-like material (gelatin phantom) interfaces. An electromagnet was used to apply the desired dynamic force to the sphere and a high-speed camera was used to track the movement of the sphere. Using the experimentally measured response of the sphere and the dynamic response of the sphere predicted by a sophisticated analytical model of the sphere located at a medium interface, the shear modulus, density and damping of the tissue-mimicking material were determined. The procedure followed in this study successfully produced the shear modulus, density and viscous damping ratio of the 20% (and 30%) gelation phantom as 1320 Pa, 1040 kg/m³ and 0.12 (and 2580 Pa, 1180 kg/m³ and 0.2), respectively. As the sophisticated theoretical model that is valid for small and large sphere displacements includes many parameters for the system such as the mass and size of the sphere, the inertia force of the medium involved in motion and the radiation damping due to shear waves and the experimental setup is very straightforward, it is believed that the procedure proposed in this study can be widely exploited to identify accurate material viscoelastic properties in practice.

Abstract: It is evident that the response of linear structures under dynamic loads depends to two important dynamics parameters of structures, namely, the natural periods and structural damping. These parameters always characterize the oscillation and the energy dissipation of buildings. In fact, the values of these parameters differ significantly, before, during and after an earthquake from values selected during the design phase. This phenomenon, among other, introduces uncertainty into the building simulation process, which remarkably influences the structural response and associated performance of the structure under dynamic loads. This paper develops a new methodology to estimate the maximum absolute response for linear structures with uncertain damping using the Artificial Neural Networks (ANN) and the Monte Carlo method. The proposed method is illustrated using the target design response spectra corresponding to the EC8 for linear structures exposed to seismic loads. The numerical results revealed the practical applicability of the proposed methodology and the crucial influence of accounting the damping uncertainty in structural dynamics. Additionally, the method can be used in practice, mainly for important and special structures where uncertainty could lead to significant changes in structural response.

Abstract: Experimental studies magnetorheological elastomer specimens dynamic properties under the magnetic fields action on the vibrostend are carried out. Amplitude-frequency characteristics have been obtained. The magnetic field effect on the silicone magnetoreactive elastomers deformation properties and damping coefficients experimentally is established.

Abstract: In the present study, the microstructure, martensitic transformation and damping characteristics of Fe-17Mn-xNb (x = 0, 0.5, 1, 2, 4 wt. %) alloys were investigated. Nb addition leads to the variation in both the volume fraction and the size of ε martensite, in addition, the formation of Fe₂(Nb, Mn) precipitates. The martensitic transformation exhibits a tiny dependence on the content of Nb. The addition of Nb helps to enhance the damping capacity of Fe-17Mn. The maximum value of tan δ = 0.054 is achieved in Fe-17Mn-1Nb alloy, which is increased by 42% over Fe-17Mn. The damping mechanism caused by adding Nb is discussed in terms of the volume fraction and the size of ε martensite. Besides, the role of Fe₂(Nb, Mn) is also taken into account.

Abstract: Retracted paper: In high speed machining, performance is generally influenced by the dynamic behaviour of the machine tool structures. The machine tool structure is required to be rigid in order to remove the undesirable vibration and to improve the work piece quality. The most conventional material used in machine tool structure is cast iron which has both stiffness and dynamic characteristics to perform at varying speeds. The objective of this work is to improve damping capacity of vertical machining centre column. The damping capacity of column can be increased further by using passive damping method of ball packing. Damping capacity is a crucial factor which makes the dissipation of vibration happens at faster rate. As compared with cast iron established studies shows that epoxy granite a composite material improves damping capacity. Epoxy granite though could be a good choice for improving the machine tool performance at high speeds but is poor in static stiffness compared to cast iron. In this investigation it was observed that, the static stiffness of epoxy granite composite vertical machining centre column could be increased by using steel reinforcements. The final results reveal that, steel balls with epoxy granite provide faster dissipation time of 15ms at 70% packing ratio as compared to glass balls that showed dissipation time of 35ms. Also it was seen that, the steel balls offer the better damping capacity at optimum packing ratio of 50% mainly due to its specific gravity and mass of the balls.

Abstract: In scientific work is presented the solution of scientific and practical task – the development and evaluation of the possibility of using difficult combustible epoxyurethane (EU) mastic with increased vibration-damping properties and the necessary physical and mechanical properties for cladding the internal metal surfaces of railway rolling stock bodies. The compositions of the developed mastic based on the mixture of oligester cyclo-cab (OCC) and epoxidian (ED) oligomers with the addition of flame retardant – ammonium polyphosphate (APh), as well as hydrophobic filler methylaerosil AM-1-300 to give the composition thixotropic properties. As a result of dynamic-mechanical and viscoelastic researches, it was found that the mastic composition ED: OCC with the content of fire-retardant additive and thixotropic filler has high damping properties (tgδ = 0.45-0.47) in highly elastic field, and therefore, from practical point of view, this the material can work both at low (from -60°C) and moderate temperatures (to +60°C). A comprehensive fire hazard assessment showed that the developed mastic belongs to the group of difficult combustible and difficult flammable materials with slow flame spread and moderate smoke generating ability, as well as moderately hazardous in terms of toxicity. The achieved level of characteristics of the difficult combustible vibration damping mastic testifies about the prospects of its further use for facing the internal metal surfaces of bodies of railway rolling stock in order to ensure their fire safety and acoustic comfort.

Abstract: Currently, significant part of advanced air transport structural elements is made of fiber-reinforced polymer composite materials (PCM), in particular, carbon plastics. In order to increase the resistance of these materials to static electricity and lightning discharges while air transport passes through lightning fronts, lightning protection coatings in the form of copper grids are incorporated into PCM structure . For load-bearing structures and aircraft shells, the influence of dynamic loads in the form of low-cycle high-amplitude loading and hitting by solid objects is typical. The presence of inbuilt metal structure introduces additional uncertainty into the anisotropic PCM perception of these loads. Studies of the strength of carbon-fiber-reinforced plastics with built-in LPC at low-cycle loading and their perception of shock load has been carried out. It is established that short-term processing in the microwave electromagnetic field leads to an increase in the strength of the samples under low-cycle loading by 210%. CFR with LPC absorbs a part of the shock impulse and does not transfer it completely to subsequent structures. The microwave electromagnetic field helps to improve the damping properties of materials by 19.5% in average with a low impact energy. With an increase in the impact force energy, the effect of the microwave electromagnetic field is manifested to a less extent; further improvement of the damping properties does not occur. It increases the elastic characteristics of the material and practically does not lead to cracking and exfoliation of the surface layer in the impact area. The results can be used in the development of technologies for final processing of the products made of PCM in order to increase their resistance to dynamic loads.