Papers by Keyword: Damping Ratio

Abstract: The damping property is a material's energy dissipation capacity, indicating its ability to resist vibrations. The parameters of damping characteristics can be evaluated using the traditional Fast Fourier Transformation (FFT) technique, which suffers from the loss of time. Therefore, Hilbert Transform (HT) and Wavelet Transform (WT) have been developed to overcome such problems and help comprehend damping properties precisely with time and frequency. This study evaluates and compares damping ratio assessment using HT, WT, and Log Decrement in linear and non-linear viscoelastic material models. To test the adapted HT and WT methods, we developed a homemade MATLAB code to evaluate the damping ratio of two data sets. Analytical data obtained from solving a linear viscoelastic material model and numerical data attained from the FE-model of a non-linear viscoelastic material were both subjected to vibration. The error percentages of the damping ratio estimated by HT and WT were 6.1 and 11.75, respectively, compared to 43 for Log Decrement. These results confirm that HT and WT can accurately predict the damping ratio of non-linear viscoelastic material models.

Abstract: Fiber reinforced polymer composites made with glass fibers are among the oldest and most popular kinds of composites in use today. Glass fiber reinforced composites' key benefits are their adaptability for specific material applications, which allows them to give a number of design advantages relating to strength, chemical stability, impact damage tolerance, heat insulation, and low cost. The focus of this research is to investigate the role of hybridized ramie fibers in the assessment of enhanced vibrational damping capabilities in fiber glass reinforced composites, as well as in the initial assessment to verify their acceptability for real-time applications. Composite molding employing the hand layup technique was used to fabricate hybrid epoxy composites with ramie to glass fiber weight ratios from 0 to 50%. A free vibration test was performed to determine the hybrid composite's vibration dampening capabilities as a function of the ramie fiber filler content. The results demonstrated that the damping ratio was reduced when the percentage of ramie fiber in the GFRP composite was raised from 10% weight to about 50% weight. But adding up to 40% wt of ramie fiber to the hybrid composite had the biggest effect on the damping ratio, natural frequency, storage modulus, and loss modulus. This means that using ramie fiber in hybrid composites will be cost-effective and good for the environment.

Abstract: The mechanical properties of epoxy granite composite are extensively influenced by the structure of porosity. The aim of this research work is to establish a mathematical model to estimate the correlation among damping and porosity. Also to estimate the correlation among flexural strength and porosity for given epoxy granite composites using experimental methods. The theoretical porosity of epoxy granite in terms of their component properties and volume fraction were determined and verified. Taguchi design of experiments was applied to plan the number of experiments to be carried out. The experimental results obtained from different test were plotted on graph over analytical results. Regression analysis was applied to establish the empirical relation between inherent properties and mechanical properties. Comparison between the analytical model and experimental results was carried out to validate the mathematical model

Abstract: The aim of the present paper is to study the vibration behavior of a sandwich structure with honeycomb core experimentally and numerically with different design parameters. The natural frequency and damping ratio were obtained. Core height, cell angle and face thickness were considered as design parameters. Finite element models for the honeycomb sandwich were developed and analyzed via ANSYS finite element analysis (FEA) software. Response Surface Method (RSM) is used to establish numerical methodology to simulate the effect of the design parameters on natural frequency and damping ration. The employment of (RSM) provides a study of the effect of design parameters on natural frequency and damping ratio, numerical modeling of them in term of design parameters and specifying optimization condition. The experimental tests were conducted on sandwich specimens for the validity goal of the previous models created via the finite element analysis. The obtained results show that the natural frequency is directly proportional to the core height and face thickness, while it is inversely proportional to cell angle, Vice versa for damping ratio. Moreover, the optimum value of natural frequency (209.031 Hz) as minimum and damping ratio (0.0320) as maximum were found at 4.8855 mm of core height, 26.770 cell angle and 0.0614 mm face thickness.

Abstract: This paper designed and completed the different polymer dosage of recycled concrete, was prepared by adding amount was 7%, 14%, 21%, 14% styrene butadiene latex recycled concrete, recycled rubber powder recycled concrete and ordinary concrete block, the cube compressive strength and damping performance test. The cube compressive strength of concrete test according to the ordinary concrete mechanics performance test methods, specimen is 150×150×150 mm cube specimens, pressure testing machine loading speed is 0.5 MPa per second. The concrete damping performance test is carried out according to the free attenuation method, with the hammer vibration test device, the test piece is T type. Based on the damage form of specimens, the compressive strength and damping performance analysis, and compared with ordinary concrete as the benchmark analysis test results show that the polymer recycled concrete cube compressive strength failure process and failure pattern basic consistent with common concrete. In the water/cement ratio, sand ratio, and amount of material per unit volume is the same, under the condition of polymer recycled concrete cube compressive strength is lower than normal concrete, damping performance is higher than that of ordinary concrete, the compressive strength is inversely proportional to the damping sexual relations.

Abstract: This paper designed and completed the different polymer dosage of recycled concrete, was prepared by adding amount was 7%, 14%, 21%, 14% styrene butadiene latex recycled concrete, recycled rubber powder recycled concrete and ordinary concrete block, the cube compressive strength and damping performance test. The cube compressive strength of concrete test according to the ordinary concrete mechanics performance test methods, specimen is 150×150×150 mm cube specimens, pressure testing machine loading speed is 0.5 MPa per second. The concrete damping performance test is carried out according to the free attenuation method, with the hammer vibration test device, the test piece is T type. Based on the damage form of specimens, the compressive strength and damping performance analysis, and compared with ordinary concrete as the benchmark analysis test results show that the polymer recycled concrete cube compressive strength failure process and failure pattern basic consistent with common concrete; In the water/cement ratio, sand ratio, and amount of material per unit volume is the same, under the condition of polymer recycled concrete cube compressive strength is lower than normal concrete, damping performance is higher than that of ordinary concrete, the compressive strength is inversely proportional to the damping sexual relations.

Abstract: This paper aims at evaluating the prediction accuracy of macroscopic static and dynamic mechanical properties, including damping properties, of glass fiber reinforced thermo plastics (GFRTP) obtained via computer simulations. The prediction procedure is based on the Eshelby-Mori-Tanaka approach using fiber orientation tensor. The prediction accuracy of mechanical properties depends on the fiber orientation tensor. In this paper, we compare that prediction accuracies obtained using measured fiber orientation tensor and using simulated fiber orientation tensor by resin flow analysis. Additionally, we propose a linearized damping model based on the Eshelby-Mori-Tanaka approach and modal strain energy method to predict damping property, as well as a method for evaluating the contribution of the elastic modulus in order to quantitatively comprehend the anisotropic characteristics of GFRTP.

Abstract: The track vertical irregularities are the originator of the vertical vibrations in the wheelset. These vibrations are further conveyed to the suspended masses of the vehicle, thus generating and maintaining their vibrations. The study of the vibrations behavior of the wheelset plays an important role in the research dealing with the improvement of the vehicle dynamic performance, mainly at high velocities. This paper examines the vibrations behavior of the wheelset during running at speed of up to 200 km/h on a track with stochastic vertical irregularities, which are mathematically represented via the power spectral density. As underlain on numerical simulations, a series of basic features of the wheelset vertical vibrations will stand out, in correlation with the velocity, track quality and its damping. The observations herein prove that the maximum level of vibrations is visible at the frequency resonance of the wheelset on the track. Similarly, it is evident that the wheelset vibrations behavior increases during the running at high velocities on a track with weak damping and low quality.

Abstract: This study investigates the performance of a new lead rubber damper (LRD), which is more advanced than existing lead-rubber based isolation devices. In contrast to the existing devices, multiple lead cores are installed in the LRD in order to optimize the behavior of the laminated rubber and lead. It is able to perform effectively under the application of shear force. An experiment was performed to investigate its dependency on the level of shear strain and frequency. The damping ratio, energy dissipation capacity and effective stiffness of the device were also evaluated.

Abstract: There are many ways to model and to analyze discrete event systems. In general these systems lead to a non-linear characteristic equation description in linear algebra. This paper presents an analytical method for solving the characteristic equation of higher order, which arise when solving ordinary differential equations of motion of rigid body systems with 2 ≤ p° ≤ 10 degrees of freedom. The objective of this work was to express the characteristic equation in the form of product quadratic polynomial, from which the modal components could be found. To validate the model, the modal parameters extraction technique – Ibrahim Time Domain (ITD) – was used to extract modal parameters from artificial data developed in MATLAB environment. The extracted modal components were compared to those obtained from the analytical model.