Journal of Engineering and Thermal Sciences
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The vibroisolation properties of the lattices containing the lumped inclusions
Get PDFThe vibroisolation and wave properties of the lattice consisting from the beam elements and lumped masses located in the lattice nodes are studied. The finite element method is used to obtain the lattice dynamic model and its dispersion equation in analytical form. It is shown that such a lattice is a bandpass mechanical filter, and the opacity bands of the harmonic signal depending on the direction of the wave propagation is found. The limiting minimum and maximum frequencies for the harmonic signal transmission are also obtained. It is shown that the addition of discrete inclusions to the lattice increases its vibroisolation properties in low-frequency range
Free vibration analysis of simply supported rectangular plates
Get PDFIn this paper, numerical analysis for free vibration of simply supported thin rectangular plates has been simulated using Ansys. The vibration of plate follows Kirchhoff plate theory. The natural frequency calculated using Ansys has been compared with Levy type solution results available in the literature. It is observed that the natural frequencies of the simply supported rectangular plate is in close agreement with exact solution results as reported in literature
Unknown input reconstruction in non-linear dynamical systems using homotopy optimization
Get PDFIn this work, a homotopy optimization method is proposed for reconstructing unknown inputs in non-linear dynamical systems. The unknown inputs are parametrized using a B-spline basis. This parameterization of inputs converts the unknown input identification problem into a parameter identification problem. The unknown parameters are identified through an optimization process. The proposed homotopy-based optimization method is designed to converge to the global optimal solution instead of a local minimum. The unknown parameters are obtained through a series of iterations guided by a homotopy parameter and an optimization algorithm
Level set medical image segmentation aided by cooperative quantum particle optimization with Lévy flights
Get PDFImage segmentation plays an important part of image processing, and is also the premise and basis of image analysis and image understanding and recognition. Among the level set based methods, the original Local Binary Fitting (LBF) algorithm is a successful deterministic algorithm that suffers from sensitization to size of the local minimum, image contours, shapes, and initial positions. Among them, Level Set method promotes the two-dimensional problem to the three-dimensional one and then solves it using implicit method to express closed curve of plane. In this article, a novel Level Set model aided by PSO was proposed to solve automated medical image segmentation. The experimental result of segmentations on the benchmark shows that our proposed method is effective to both simple and complex medical images
Linear forced-rotordynamics analysis for optimizing the performance factors of machine motorized spindle using design explorer method
Get PDFA machine-tool structure optimization is an important technique that improves the machining efficiency and saves materials and the energy resource. In this work, dynamic design optimization method for Machine-Motorized-Spindle (MMS) subjected to a number of rotating unbalanced forces effects is presented. Linear forced-Rotordynamic analysis with design explorer method has been used to simulate the output response. The Design Variables (DVs) and their limits were carefully chosen and applied to develop the Design-of-Experiment (DOE). The Box-Behnken Design (BBD) method, because of its good organization in providing much information in a minor number of required statistical experiments was used to generate the DOE. The influences of DVs on the dynamic of MMS and their levels optimization were evaluated by utilizing the Response-Surface (RS) method. The results showed that the spindle shaft inner diameter of the motor-rotor seat and its rotating unbalanced mass, and modulus of elasticity have the highest contribution in effect on the dynamic of MMHS. As well, it is found that the proposed optimization method not only improves the structural weight of MMS, but also the potential saving can be achieved in term material and energy resource
Vibration-based damage growth monitoring in beam-like structures
Get PDFDamage growth monitoring plays an important role in providing early warning of structural failure. The existing methods for damage growth monitoring are mainly local inspection methods, such as acoustic emission. These methods need a priori knowledge of accessible damage vicinity, which may not be realized in practice. Hence, vibration-based global approach is adopted to overcome these difficulties. Natural frequency, as a global modal parameter, can be measured easily and is used for vibration-based damage growth monitoring in this study. A concept of damage-induced relative natural frequency change (RNFC) curve is defined first and its relation with mode shape is then derived analytically, giving a good way to approximate RNFC curves. For monitoring damage growth, a damage growth indicator is proposed based on RNFCs between two damaged stages of a beam. The effectiveness of the indicator for damage growth monitoring is proved by both numerical and experimental cases in beam-like structures
Vibration analysis of reconditioned high-speed electric motors
Get PDFThis paper discusses the issue of assessing the condition of three-phase induction motors (which are used as power units for tools on manufacturing lines in the furniture industry) following major repairs. These high-speed motors differ from standard motors in higher frequency power input, more durable bearings and reinforced structure of the terminal part of the rotor shaft. The rotational speed of the rotor is 10,000-18,000 rpm. Such high values of rotational speed trigger a situation in which exceeding the allowable limit of residual unbalance for the rotor unit damages the motor. The damage might necessitate a comprehensive repair. Such cases are frequent. The conducted studies resulted in designing a vibration analysis for assessing the condition of reconditioned high-speed motors (a method for controlling the quality of repairs). Both high- and low-frequency analyses with a signal selection module and the basic general measurements were applied. The analysis provides the possibility of verifying the efficacy of reconditioning in relation to the mechanical validity of the repaired motors
Free vibration of circular annular plate with different boundary conditions
Get PDFThis paper deals with the numerical simulation of free vibration analysis of a thin circular annular plate for various boundary conditions at the outer edge and inner edge. Classical plate theory is used to derive the governing differential equation for the transverse deflection of the thin isotropic plate. The finite element method is used to evaluate the first six natural frequencies and mode shapes of the thin uniform circular annular plate with radius ratios (r1/r2) for different boundary conditions. These natural frequencies results are compared with those available in the literature. The results are verified with classical plate theory with our Abaqus results and checked with the previous research literature on the topic
Optimization of the longitudinal-torsional ultrasonic step-like horn design for milling tool applications via the tool load account
Get PDFUltrasonic horns are used in the ultrasonic-assisted milling and cutting tools. However, the interaction with tool end vibrations deteriorates the horn performance. In this study, the amplification coefficients and vibration node locations of an ultrasonic horn were determined via the 1D wave theory and optimized by the tool load effect account. By arranging spiral grooves at the straight part of the ultrasonic horn, a longitudinal-torsional modal converter was introduced. This made it possible to convert longitudinal vibrations into longitudinal-torsional coupled ones by the superposition of incident and reflected longitudinal waves with reflected transverse ones at grooves. Orthogonal L9 (33) tests with parameters of spiral grooves as variables were designed and conducted, and longitudinal-torsional ratios (LTR) of the milling tool end under different conditions were assessed using the commercial ANSYS software package. The in-depth analysis of simulation results implies that the LTR values are controlled by the following influence factors in the decreasing order: helical angle, number of grooves, and groove width. Single-factor tests indicate that LTR exhibits an initial drop and a further rise with the helical angle, attaining its minimal value at 30°; it drops with the number of grooves n, and remains practically unchanged with the groove width variation. Finally, the vibration tests of the proposed horn with the optimized parameters corroborated its feasibility and demonstrated its excellent performance in the ultrasonic-assisted milling tool application
Mini Review: Is fluoroquinolone drug or poison?
Get PDFQuinolones are a class of broad-spectrum antibiotics with valuable pharmacological properties due to their improved pharmacokinetic properties, particular mechanism of action and broad and potent activity; being one of the fastest growing class antibacterial growths in terms of therapeutic use and overall benefit. Because of their effectiveness, spectrum of activity, and generally good safety profile, fluoroquinolones were used widely for multiple clinical indications throughout the world. Although still clinically valuable, fluoroquinolone use has become limited in some clinical situations, as bacterial resistance has emerged over time. In the sections that follow we review the range of molecular mechanisms that motivate quinolone resistance