Applied Mechanics and Materials Vols. 592-594

Abstract: In this paper, the crack identification using smart technique (by several hybrid membership functions in a fuzzy controller) has been developed for inverse analysis of the vibration signatures (like modal frequencies, mode shapes) and crack parameters (like crack depth, crack location and crack inclination) of an inclined edge crack cantilever beam. The modal frequencies are obtained from finite element (using ANSYS) and experimental analysis which are used as inputs to the hybrid fuzzy controller. The hybrid fuzzy system is designed by taking different types of membership functions (MF) to determine the crack parameters. The calculated first three modal frequencies are used to create number of fuzzy rules with the three output crack parameters. Finally, the proposed hybrid technique is validated by comparing the results obtained from trapezoidal and Gaussian fuzzy controllers, FEA and experimental results. The outcomes obtained from hybrid fuzzy controller are in good agreement with experimental results. Nomenclature

Abstract: Vibration signal of a defective bearing carries fault related information. The aim of this paper is to develop a signal processing methodology that identifies the presence of defect from bearing vibration signal subjected high background noise. A simulated vibration signal considering inner race defect in a deep groove ball bearing with low signal to noise ratio has been generated and investigated. A technique involving CWT of vibration signal and post-processing though FFT has been adopted to analyze the signal. Results show that proposed methodology can yield the presence of inner race defect prominently from a noisy vibration signal.

Abstract: A magneto rheological damper is a damper filled with magneto rheological fluid, which is controlled by a magnetic field. This allows the damping characteristics of the shock absorber to be continuously controlled by varying the force of the electromagnet. This type of shock absorber has several applications, most notably in semi-active vehicle suspensions which may adapt to road conditions, as they are monitored through sensors in the vehicle. This paper presents magnetic saturation analysis of non-parametric model of magnetorheological (MR) damper using ANSYS for improvement of the higher force with optimal current and MATLAB/Simulink simulation for quarter car model equipped with MR damper to conduct dynamic studies of the system using skyhook controller and comparative study for passive and semi-active system.

Abstract: This paper focuses on the calculation of modal frequencies and corresponding mode shapes of Gun Barrel by analytical method and the Finite Elements Method. Modal analysis is used to find out natural and succeeding two modes frequencies for transverse vibration. Barrel is considered as a cantilever beam. Recoil of Gun Barrel is incorporated as variation in the length cantilever beam. Increase in modal frequencies due to gun barrel recoil is observed. It is concluded that the transverse vibration of gun barrel coupled with the recoil produces a band of frequencies in each modes. The analysis and results discussed can be used for design and performance evaluation, selection of accessories and attachments of gun systems.

Abstract: Vibration-based inspection is an area of active research. This task is performed by estimating the effects of structural damage on the eigen parameters of structures. The problem of detecting, locating, and quantifying the extent of damage was under study for several decades. In order to investigate the prevailing effects of damage present in the structure under examination, a mathematical model of the damage must be introduced into the model of the structure at the location of the fault. While focusing on transverse vibrations, a simple stiffness reduction of the damaged region was used. In the present work the vibration parameters (relative first three natural frequencies) of the cracked structure are treated in a controller. The controller is designed using fuzzy logic & genetic algorithm. Here the fuzzy rules are optimized by using genetic algorithm. Using the controller, the crack locations can be determined.

Abstract: This paper presents an investigation methodology for detection of size and location of open edge transverse crack on a rotating beams using continuous wavelength transform. Generally, vibration characteristic of abeam like structure changes significantly due to the presence of crack. However when the crack is relatively small, it is difficult to identify the presence of the crack from the vibration response data only. In the present case, vibration parameter, such as, mode shapes of damaged beams are obtained using the finite element method. The CWT is implemented with different scales on mode shape of the rotating beam to evaluate crack size and its location. It is also shown that this method can produce satisfactory results with some limitation based on mode shape profile. In addition to the the profile quality, other determining factors are scale and resolution of the detection signal

Abstract: Suspension system of an automobile not only supports the body of the vehicle, engine and passengers but also absorbs shocks arising from the roughness of the road. Most of the present day cars are provided with independent suspension for the front wheels and conventional suspension for the rear wheels. Such a suspension system is referred in this paper as semi-independent suspension system. When the automobile is moving, the roughness of the road keeps giving excitations to the suspension system through tyres. The frequency of excitation is directly proportional to the velocity of the vehicle and inversely proportional to the distance between two undulations of the road. The knowledge of natural frequency is important because the designer would prefer to keep the lowest natural frequency much higher than the frequency of excitation. In this paper, an attempt is made to study the effect of centre of mass of the main body on the natural frequencies of the system.

Abstract: The reduction of noise and vibration is a major requirement for performance of any vibratory system. Passive damping technology using viscoelastic materials is classically used to control vibrations. Viscoelastic material among the damping materials is widely used to dissipate the structural vibration energy. Three-layer sandwich beams, made of two elastic outer layers and a viscoelastic layer sandwiched between them, are considered as damping structural elements. This paper presents the effect of thickness of constrained damping material on modal loss factor of vibrating structures. Measurements are performed on sandwich beam structure. In order to understand the effectiveness of the sandwich structures, the dynamics of beam with constrained viscoelastic layers are investigated. Comparisons of the experimental and the Numerical results confirm that the damping levels and the natural frequencies of damped structures are well corroborated.

Abstract: In structural applications, plates with cut-out or holes are commonly used. The structure will deteriorate dynamically due to presence of cut-out and experiences amplification in vibrations. This paper presents an experimental study on effect of position of vibratory flap on dynamic response of a clamped rectangular plate with cut-out subjected to harmonic excitation. Vibratory flap is an auxiliary plate attached on the main plate as a cantilever plate and acts as a dynamic vibration absorber, which is used to reduce the vibration of the plate at first and second frequencies. Investigation has been carried out for different combinations of flap location and orientation through experimental sine sweep test. From the test it is found that, there is an optimum position where vibration suppression is more effective with improved dynamic response of the plate with cut-out in the presence of flap. The experimental results have shown good agreement with the published finite element analysis results.

Abstract: In this study, free vibration responses of a carbon nanotube reinforced composite beam are investigated. The governing differential equations of motion of a carbon nanotube (CNT) reinforced composite beam are presented in finite element formulation. The validity of the developed formulation is demonstrated by comparing the natural frequencies evaluated using present FEM with those of available literature. Various parametric studies are also performed to investigate the effect of aspect ratio and percentage of CNT content and boundary conditions on natural frequencies and mode shapes of a carbon nanotube reinforced composite beam. It is shown that the addition of carbon nanotube in fiber reinforced composite beam increases the stiffness of the structure and consequently increases the natural frequencies and alter the mode shapes.