Papers by Keyword: Frequency

Abstract: There are many products that produce sound when external force is applied to metals and alloys, such as wind chimes, golf clubs, and metal bats. Previous studies have investigated the differences between acoustic properties and sound impressions of these products depending on the type of material. Sound is an element that influences the comfort in our daily lives and the sensation of players in sports. Therefore, it is important to clarify the differences in acoustic properties of different materials in order to design and improve products. However, the effects of changes in chemical composition in the same material on acoustic properties have not been sufficiently studied. The purpose of this study is to evaluate the change in acoustic properties due to the chemical composition of metals and to contribute to the acoustic design of products. In this study, six types of brass specimens with varying zinc content from 5% to 40% were prepared, and the differences in frequency and decay time of hitting sound were evaluated. As a result, it was confirmed that the frequency tended to decrease as the zinc content increased, and the decrease in frequency was particularly pronounced for the specimens with a zinc content of 40%. Attenuation time showed an increasing trend but decreased slightly for specimens with 40% zinc content. These results indicate that the chemical composition of brass has a significant effect on acoustic properties.

Abstract: In this study, we explored the potential of a compact acoustic control system using giant magnetostrictive actuators (GMAs) for application in ultracompact electric vehicles (EVs), which face significant challenges in maintaining interior acoustic comfort due to their structural limitations. A fundamental investigation was conducted to clarify how differences in the internal structure of GMAs affect their vibration and acoustic output performances. Two GMA prototypes with different internal configurations (Model A, featuring two shorter rods and multiple permanent magnets, and Model B, featuring a single long rod) were evaluated through driving experiments. The acoustic signals were measured using a wall panel setup simulating in-cabin conditions. Both models exhibited an increase in sound pressure level with an increase in the applied voltage. However, the frequency response characteristics differed between the models. Model A performed better in the low-frequency range, whereas Model B maintained consistent performance across a broader frequency range. These findings provide essential insights into the design of space-saving and energy-efficient acoustic systems for next-generation mobility solutions.

Abstract: The paper presents the results of the study of bodies movement on a rough surface, which carries out longitudinal and transverse oscillations. The design of the inertial conveyor for reducing dynamic loads has been proposed. The dependences of the acceleration of the longitudinal oscillations of the chute and the speed of the transverse oscillations of the chute walls on dimensionless time τ=ωt have been obtained. As a result of the kinematic analysis of the mechanism of the reciprocating movement of the chute, the dependences of the movement, speed and acceleration of the chute of the inertial conveyor on the angle of rotation of the crank and its rotation frequency have been obtained. As a result of the conducted theoretical studies, it has established that when the chute of the inertial conveyor is given transverse oscillations during periods of time and when the load slides along the surface of the chute, the productivity of this vehicle significantly increases. The obtained dependencies can be used in the design of inertial conveyors with given technical and economic indicators.

Abstract: SiC MOSFETs still suffers from some open issues, such as the high density of defects existing at the SiC/ SiO₂ interface. In order to characterize such interface, a non-destructive investigation technique should be employed. In this work, we investigate the measurement of Gate capacitance with biased Drain. More in detail, the effect of frequency on such curves is considered. The analysis is performed using both in experimental setup and numerical framework. Experimental and numerical results both exhibit a sharp capacitance peak in the inversion region which reduces its height as frequency increases.

Abstract: Laser Surface Texturing (LST) has demonstrated to be the most reliable technique for the micro-modification of surfaces, allowing to obtain taylored surfaces. These modifications, depending on the basic micro-geometry and its repetition pattern, can provide special functionalities to a surface, such as hydrophilicity, hydrophobicity, reflectance, anti-bacterial, ostheo-integrability, as well as custom aesthetic, among others.Nevertheless, when a laser irradiates metallic surfaces, the micro-structure can be modified due to the heat induced, changing the mechanical properties of the surface. To avoid these effects, cold or ultra-short pulsed lasers must be used.A cold laser emits optical pulses with a duration below 1 ps (ultra-short pulses), in the domain of femtoseconds (fs=10^-15 s). These ultra-short pulses, combined with high frequencies, in the megahertz region, leads to pulse trains with high repetition rates. This allows the sublimation of the material, keeping it relatively cold due to the short exposition time to irradiation.Ti6Al4V is the most used Ti alloy, thanks to its excellent weight/mechanical properties ratio. Nevertheless, its tribological behavior is very poor. Although there is intense research to improve it by using LST, the study of the influence of femtosecond laser parameters in the desired micro-geometries is still a gap in the scientific literature.In this research, a study of the influence of power (up to 50 W) and frequency (up to 2 MHz) in the fs-laser texturing of Ti6Al4V is presented. Local pulse repetition, linear and surface textures have been studied by combining power and frequency in these ranges, evaluating the geometry obtained by variable focus microscopy. The study carried out has allowed to determine the optimal set of parameters as a function on the target texture geometry, as well as the range in which the LST removal process changes from sublimation (for texturing) to melting (for micro-machining).

Abstract: The process of quickly removing abrasive particles of silica and ceria slurries is important in the use of CMP equipment. Megasonic cleaning of nozzle injection type is one of a variety of post-CMP cleaning methods and its performance including cleaning efficiency and erosion was explored experimentally with parametric studies. In the cleaning process, it is favorable to achieve both high efficiency and low damage. The cleaning efficiency was defined by particle removal efficiency (PRE) with a glass sample spin-coated with small silica particles; the damage was detected from mass loss of aluminum foils after the cleaning. The cleaning tests show that the performance of nozzle injection megasonic cleaning depends significantly on ultrasound frequency and water temperature. Toward more efficient and less erosive cleaning, the nozzle injection angle is also expected to play a key role.

Abstract: In order to expand the possibilities of practical application of polymeric materials we studied syndiotactic 1,2-polybutadiene (1,2-SPB). The experimental procedure and the MV-002 device for determining the breakdown voltage and electrical breakdown of a polymer are described in detail. Mathematical models of the dependence of the breakdown voltage of the polymer on the frequency and magnitude of the electrical breakdown of the polymer on the thickness of the sample have been built and studied. Regression analysis was used for mathematical data processing. The reliability of the results obtained is proved by the methods of test statistics.

Abstract: The article describes the behavior of a fresh concrete exposed to the effects of vibration. The individually deposited layers of concrete mix are able to migrate in the vertical and horizontal direction in the specimen or structure. This phenomenon is simulated using successively deposited layers of colored concrete of defined height. The specimens were exposed to vibrations of variable frequency and amplitude. The degree of interconnection between the layers is determined by using regular sections across the specimens to observe the differences in the movement and interconnection of the layers for different consistencies of the concrete mix. The results summarized in this paper present new results of continuous research aimed at a more detailed description of the vibration behaviour of fresh concrete, as this phenomenon is relatively marginally addressed in the current standards.

Abstract: Optimization on Porous Asphalt Pavement is based on noise reduction capacity. The influence factors of sound absorption properties of porous asphalt mixture were studied by using standing wave ratio method.The results indicate that: The peak absorption coefficient of porous asphalt mixture increases with the increase of porosity and the peaks are concentrated in the frequency range from 800Hz to 1000 Hz. The peak moves to high frequency as the porosity increase. It is better to use smaller nominal maximum aggregate size to reduce the noise level. With the pavement thickness increases, the average absorption coefficient of porous pavement in the high frequency band will decreases. The recommended thickness of Porous Asphalt Pavement range is 40-60mm.

Abstract: In order to achieve optimal physical and mechanical properties of hardened concrete, it is necessary to determine the right intensity and vibration time of fresh concrete during casting. Since concrete is considered as a polydisperse substance and various aggregate grains move randomly during vibration, it is very difficult to describe this stochastic phenomenon using exact physical equations and it is more advantageous to apply an experimental approach to verify the effects of vibration on fresh concrete. The effect of vibrations on fresh concrete increases the speed gradient of individual grains and thus reduces the viscosity of the cement paste. The intensity of vibration is determined mainly by the frequency, amplitude and centrifugal force of the eccentric of the vibrating machine. The optimal vibration time is generally considered to be the "minimum required". Insufficient vibration caused by an unsuitable vibrating machine or a short vibration time can result in insufficient compaction of the aggregate grains, non-release of accumulated air from the fresh concrete mixture, formation of cavities or poor-quality casting of parts of the structure with a higher degree of reinforcement. Vibration with excessive intensity or time can also be considered dangerous. The over-compaction of concrete is most often demonstrated by segregation of aggregates. The presented research deals with the determination of the optimal time and intensity of vibration of fresh concrete mixture to achieve the required physical properties of concrete, i.e. high compressive strength and modulus of elasticity of hardened concrete while reducing the negative effects of vibration, especially segregation of aggregates.