Papers by Keyword: Amplitude

Abstract: In the era of the manufacturing industry which is developing very rapidly, a manufactured product must have high product quality, especially machining products such as turning products. AISI 1045 steel is a type of low carbon steel with a carbon content of (0.43% – 0.50%) which is often used on the market because it has many advantages and the price is quite affordable. Vibrations that occur in the turning process cause undesirable effects; such as discomfort, inaccuracies in measurements and non-optimal turning results. Roughness really depends on the type of tool and tool geometry. In this study, carbide chisels were used with cutting variations, namely: variations in cutting angle (Kr) selected 80⁰, 85⁰ and 90⁰, spindle rotation (n) 200 rpm, feeding (f) 0.3 mm/put , feeding depth (a) 1 mm and load mass (m) 150 grams, 300 grams and 450 grams. When turning, the amplitude value is measured using the Vibxpert toolII and After turning each set of machining variables, the roughness is measured using a machine Laser 3D Measuring Laser Microscope OLS4100. The measurement data obtained is graphed with the relationship of Load Mass & cut angle with roughness and amplitude value. The purpose of this research is to find out the effect of passive mass reduction and the cutting angle of AISI 1045 Steel on the roughness and amplitude values. From the results of the analysis, it was found that the most optimal load mass is 450 grams and the cutting angle (Kr) the most optimal is 80° with a roughness value of 4.07 µm and an amplitude value of 0.15 mm/s².

Abstract: The article presents some new theoretical and experimental solution of a scientific and applied problem of technological support for vibratory centrifugal processing of complex-profiled parts in a bulk abrasive environment. This solution aims to increase productivity while ensuring the desired quality of the processed surfaces. The authors have developed a mathematical model that describes the action of abrasive particles on the surface of the parts, taking into account the parameters of the granular abrasive medium based on Voigt’s law. This allows the description of dynamic processes in the processing environment for a wide range of material types. The natural frequencies of oscillations of the processed medium layer have been determined, which depend on the amplitude of its vibrations for different densities of soft and hard materials of the processed medium and the medium with linear-elastic properties. The methodology includes the use of test equipment to conduct experimental research on the process, which involves determining changes in specific metal removal rates and surface roughness using the frequency converter Altivar 71 with the PowerSuite v.2.5.0 software.

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.

Abstract: The aim of this study was to characterize the fatigue life of the SAE 1541 carbon steel. The fatigue life was predicted based on the strain-life approach through the application of constant and variable strain data with negative, zero, and positive mean values. Each strain data was developed at amplitude range of 200 με, 400 με, 600 με, 800 με, 1,000 με, 1,200 με, 1,400 με, 1,600 με, 1,800 με, and 2,000 με. The results showed there was no significant difference in the fatigue life for negative, zero, and positive mean strain amplitudes using the Coffin-Manson model. This is due to the non-consideration of the mean strain effect by the Coffin-Manson model. However, according to the Morrow and SWT models, negative mean strain data gave a longer fatigue life while positive mean strain data gave a shorter life. In addition, variable strain data gave a longer fatigue life since they contain low and high amplitudes, with the low amplitudes contributing to minimum fatigue damage.

Abstract: In analytical form, formulas are obtained for the amplitude of forced harmonic longitudinal vibrations of reinforced concrete and fiber-reinforced concrete columns with fixed edges. In order to verify the proposed approach, columns were simulated in the ANSYS program and calculated by the finite element method. Analysis of the calculations shows that a significant raise in the amplitude of the forced vibrations is observed only in the region of the first resonant frequency. It has been established that the value of the maximum amplitude of the vibrations of the fiber reinforced concrete column is 16% less than that for a reinforced concrete column.

Abstract: The known methods of calculation of oscillation amplitudes of massive foundations of machines taking into account damage are analyzed in the article. It is established that the method set out in the building codes allows to determine the amplitudes of the foundation oscillations at any point of the foundation, approximately enough. This technique does not take into account the interaction with the soil of the deepened foundations, but takes into account only the physical and mechanical characteristics under the sole of the foundation. The authors propose a finite element method (FEM) calculation using the Plaxis 7 software package installed on a personal computer and a vibrometer. The result is the oscillation amplitude of the massive foundation. The presence of cracks and damage increases the magnitude of the oscillation amplitudes from the dynamic impact. If you make timely planned repairs to the foundations, the amplitude of the oscillations can be reduced.

Abstract: In the paper presented are given oscillation amplitude threshold compaction and vibrating platform, stiffness and viscosity of the concrete, and the frequency and amplitude of movement on compacting concrete.

Abstract: The relationship of oscillations amplitude of the granular medium-elastic screw system whilst passing over resonance at different values of the bulk mass per unit length at different motion velocity has been studied. The relation of resonance oscillations of the granular medium-elastic screw system described by ratio α(t) and ν(t) has been shown. Based on these ratios, we plotted time variations of amplitude against quick passing over resonance.

Abstract: The objective of this study is to give the designer an appreciation of the heat transfer enhancement in turbulent flows through corrugated channels in a heat plate exchanger. Precisely, the influence of a new technic named the artificial roughness is probed on corrugated walls, with their variable wall amplitudes for assessing the effectiveness of the heat exchange. For that purpose, a numerical simulation approach is adopted. The rectangular, triangular, trapezoidal and sinusoidal corrugated wall and artificial roughness wall shapes are investigated, in order to determine the optimal wall profile resulting in significance increase in the heat exchange process with a minimum friction loss. The numerical results are presented in the form of isotherms, streamlines, contour, Nusselt number (Nu) and friction coefficient (Cf ) using commercial software ANSYS- Fluent where the Reynolds number is in the range from 3 000 to 12 000. Our simulations reveal that the sinusoidal-corrugated channel has the highest heat transfer enhancement followed by rectangular, triangular and trapezoidal-corrugated channel. In addition, introduction of artificial roughness in the wavy channel induces stronger secondary flow which makes the flow three-dimensional and improve the heat transfer by a maximum 40% at a Reynolds number equal to 12 000. This may indicate benefits for designing heat plate compact exchangers capable of higher performances in the turbulent flow regimes.

Abstract: In the current scenario, there is a continuous need for increasing the efficiency of the aerodynamics of wind turbine blades through research studies. Vibration in a wind turbine blade has lot to do on its performance. An effective approach is required by wind mill including to control the vibration to achieve better results. The objective of this research is to investigate the vibration characteristics of the prototype horizontal axis wind turbine blade developed by using 3D modelling software. Shape memory alloys with their variable material properties offer an alternative adaptive mechanism hence it is used as a damping material. A prototype blade with S1223 profile was manufactured and the natural frequency was found over the surface of the blade. Similarly, results were studied by increasing the number of alloys wires over the blade up to three. Results showed that the embedment of shape memory alloys over the blade’s surface increases the natural frequency and reduce the amplitude of vibration because of super elastic nature of alloys. Also it was observed that the natural frequency increased by 6% and reduced the amplitude by about 93% where three wires of 0.5mm diameter were kept for the length of 720mm.