Maintenance, Reliability and Condition Monitoring
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The longitudinal vibration characteristics and parametric analysis of a ship thrust bearing integrated with internal disc springs
Get PDFTo reduce the transmission of shafting longitudinal vibration in surface ships, a design of thrust bearing integrated with internal disc springs is proposed and the longitudinal vibration characteristics of the shafting are studied. According to the structural characteristics of thrust bearing and the deformation characteristics of disc springs, the specific size and combination forms of disc springs in the thrust bearing are designed, and the effective disc springs schemes are achieved according to the static and dynamic design requirements. With the integration of the disc springs into the thrust bearing, the peak of longitudinal displacement response at the base of thrust bearing can be reduced by 10 dB by two schemes of disc springs. The proposed design can effectively suppress the transmission of shaft longitudinal vibration to the hull, which has engineering significance for the longitudinal vibration control of the shafting of the surface ship
Effect of particle gradation on the triaxial test of soil using three-dimensional DEM analysis
Get PDFNumerical simulation of triaxial test are carried out for soil specimens with varying particle size by DEM analysis under the flexible boundary. For the purpose, soil state characteristics such as shear band formation, variation law and the difference between the global void ratio and the local void ratio are particularly focused. Results shows that the shear band of multi-graded specimen is more difficult to create, but it is thicker than that of single-graded specimen. Overall void ratio changes mostly due to particle movement at the shear band and independent to particle gradation. The shear strength of the multi-graded sample is better than that of the single-graded specimen
Effect of the temperature increase in oil-immersed electric reactor on the stress loss of the fastening rods of core limb
Get PDFThe noise and vibration of large oil-immersed reactor is usually controlled and reduced by using high-strength pretensioned steel rods to fasten iron cores. But the effect of uneven temperature increase in the reactor on the pretension relaxation of steel rods is rarely discussed in previous literatures. A combined fastening device of high-strength steel rod and disc spring is designed to conduct temperature experiment in this paper. And three-dimensional (3D) finite element model is developed to reproduce the experiment process. After the numerical simulation method is verified, finite element analysis of a real BKD-6700/20 oil-immersed reactor is performed. The prestress loss proportion of the high-strength pretensioned steel rods in the oil-immersed reactor under practical operating state is 17.91 % owing to its uneven temperature rise, which can result in significantly weakening of its vibration and noise reduction function
Frequency splitting approach using wavelet for energy management strategies in fuel cell ultra-capacitor hybrid system
Get PDFUsing frequency splitting, two energy management strategies (EMS) based on Haar wavelet decomposition and Fourier analysis for fuel cell hybrid vehicle (FCHV) are proposed to manage efficiently the power flow between components. The paper aims to discuss the performances of the proposed EMS in terms of dynamic behavior, robustness operation, real time application and fuel economy. For apply this methodology, two EMS approaches are elaborated and successfully tested for parallel Fuel Cell/UC: conventional approach using Fourier Transform analysis (FT) and Wavelet analysis approach allowing natural frequency splitting. Finally, and to evaluate the performance and relevance of the developed approach, a comparison analysis were conducted. The simulation results exhibit the effectiveness of both strategies. Indeed, Wavelet analysis leads to better results in terms of energy flow and dynamic behavior, excellent robustness and stability of system, as well as energy economy improvement. A very relevant strategy is proposed based on Wavelet analysis using digital filtering techniques, which enables a natural frequency splitting to ensure the best global performances. In addition, the approach remains simple and suitable for real time operation
Vertical vibration modeling for 2:1-roping traction elevator system
Get PDFThis paper presents a vertical vibration model for 2:1-roping traction elevator system. In this model, masses of suspension ropes are considered and their kinetic energy is calculated by applying Rayleigh method. Equations of motion for free vibration are derived. To verify the improvement of the model, an output dependent only modal test scheme using eigenvalue realization algorithm is conducted to obtain natural frequencies from a real elevator installation. The comparison of experimental results and numerical results of proposed model and previous similar models is presented on calculation of natural frequencies. The results show that proposed model is able to reflect the 5th natural frequencies more exactly under 0 % and 100 % load conditions
Study on magnetostriction characteristics under different measurement conditions under an externally compressive stress
Get PDFThe measurement of magnetostriction characteristics of grain-oriented electrical steel strip under an external compressive stress has always been a main focus in the process of magnetostriction measurement. There are difficulties in the measurement of magnetostriction, especially under compressive stress, mainly because the thickness of test specimen is small, and the test specimen is very easy to deform under the compressive stress. A weight should be placed on the test specimen to prevent a deformation of the test specimen when the measurement of magnetostriction characteristics under an externally compressive stress according to the IEC/TR 62581:2010. But how much weight and how to place aren’t concerned in IEC standard. In this paper, different weights were placed on the grain-oriented electrical steel test specimen under external compressive stress and zero stress. Through analyzed the measured magnetostriction data under different weights to determine the optimal measurement method of grain-oriented electrical steel strip under compressive stress and zero stress. The purpose of this paper is to find the most accurate and high reproducibility measurement method of magnetostriction, which can truly reflect the magnetostriction performance of grain-oriented electrical steel
The relative merits of sediment transport formulas applied to the Nakdong Estuary, Korea using a coupled numerical modeling system
Get PDFThree sediment transport formulas by Lund-CIRP (2012), van Rijn (1998), and Soulsby (1997) were applied for this study with field data by Yoon (2008) and several sedimentary variables of Nakdong Estuary in a coupled numerical modeling system, CMS. CMS is adopted to compare the measured depth change data and the calculated depth change data. As a result, the Lund-CIRP formula with mean grain size (0.25 mm) and multi-bottom friction coefficients based on the mean grain size distribution had higher accuracy (1.6 %) than the other formulas. The Soulsby formula has higher accuracy for multi-grain size and 0.06 of bottom friction coefficients. The van Rijn formula has high accuracy at shallow water areas such as a river. In this study, it is judged that the accuracy of the van Rijn cases was low because the water depth of the Nakdong Estuary and the nearby sea area rapidly deepens
Productivity forecast with digital greenhouse automation system for sustainable agriculture
Get PDFGreenhouses are a popular agricultural production method by providing artificial climatic conditions. Providing optimum climatic conditions depends on the equipment of the greenhouse. Greenhouse equipment consists of systems such as heating, ventilation, shading, irrigation, and fertilization. In modern greenhouse cultivation, all these have become controllable with smart systems. These modern greenhouses, in other words smart greenhouses, can read the ambient conditions in real-time with their advanced sensor systems and enable processes such as irrigation, adjustment of ambient temperature, and ventilation to be carried out autonomously. In this study, the working principle, general structure, design, and types of equipment used in the greenhouse automation system are explained, and the system is designed and simulated on the Unity Engine
Determination of the amount of oil product vapours from the tank based on monitoring the operation of the breathing valve
Get PDFThe development of methods for calculating losses of oil and petroleum products vapours from the tank has been going on for a long time. Systems that allow for more accurate calculations are also being developed along the way. In each country, and sometimes in each company, there are their own methods for determining the loss of light hydrocarbon fractions from losses from the tank through the breathing valve. In addition, losses are divided into “working losses” and “standing losses”. In each technique, there are both pros and cons. The most characteristic disadvantage of each technique is its applicability only to the conditions in which it was developed, due to the presence of correction coefficients. This article proposes a new technique for determining the loss of hydrocarbons vapours from the tank through the breathing valve, both from “working losses” and from “standing losses”. In the course of the work, formulas were obtained for calculating the flow rate Q∆P,h through the breathing valve, which depends on the degree of opening of the pressure plate and overpressure. An experiment was conducted, instrumentally proving the application of the developed methodology. And also, the equipment is selected and recommendations on its installation and use are given
Study of skeletal changes in individuals with anterior open bite treated with JFO
Get PDFAnterior Open Bite (AOB) is a type of malocclusion that promotes severe esthetic aesthetic and functional impairment. Its etiology is multifactorial and may involve several etiological factors, such as deleterious oral habits, hypertrophic tonsils, mouth breathing, dental ankylosis and eruption abnormalities either associated with genetic factors or not. AOB is one of the most challenging treatments in any treatment protocol. A retrospective study of 21 patients with anterior open bite treated with Jaw Functional Orthopedics (JFO) with improvement in overbite was conducted with the aim of understanding mandibular behavior during the treatment. Using SPSS 11.0, using Shapiro-Wilk test all variables showed Normal distribution (p> 0.05), in the comparison between the means at T0 and T1, the t-test for paired samples was used. In order to verify whether cooperative patients had better results than the non-cooperative group, a variable was created. For all tests, a significance level of 5 % was used. A weak statistical correlation (P< 0,1) was found for Bimler’s Factor 8. Change resulted from AOB treatment with FOA in a short time. There was no statistical correlation of Bimler’s Factor 8 when cooperative patients were compared with the non-cooperative group. It could be concluded that in the studied sample there was a weak correlation between overbite improvement during AOB treatment with JFO and mandibular rotation. Further studies are necessary to understand the skeletal behavior of the maxillary bones in the treatment of AOB with FOA