Journal of Engineering and Thermal Sciences
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The application of coordinate transformation matrix into the multi-degree of freedom vibration control
Get PDFThis paper describes the application of the coordinate transformation matrices into the multi-degree of freedom vibration control. An example with an aluminum beam supported by dual actuators is used to derive how to create both the input transformation matrix and the output transformation matrix. In order to achieve the synchronous movement of the dual actuators, the direct actuator control test and 2DOF control test have been performed. By comparing with the results of the direct actuator control test without using the transformation matrix, the 2DOF control test proves that the transformation matrix is a powerful tool for a significant improvement in test control accuracy
Determining the vibration behavior of metal matrix composite used in aerospace industry by FEM
Get PDFAA2124/SiC/25p material is metal matrix composites (MMCs) reinforced with particles and homogeneous distribution, which are used especially in the aerospace industry. Vibrations of the material was evaluated by the finite element analysis (FEM). First, it analyzed as a plate 130×50×3 mm the natural frequency of the material was found in the 0-5000 Hz range. Also frequency modes of the material were determined. In order to determine the reaction against the load material, the point has implemented and forced damped vibrations. Finally, the reaction spread by forced vibration damping materials was examined
Simulation of optimal control of industrial corporations that produce complex dynamic systems engineering
Get PDFIn the article economic models to improve management efficiency by industrial corporations on the basis of scenario planning, management hierarchies Corporation. The role of business process reengineering in the formation of the integrated structures as a tool for the restructuring of the system of material, financial and information flows, aimed at reforming the organizational structure, optimizing the use of resources, improving the quality of products
An improved homotopy analysis method with accelerated convergence for nonlinear problems
Get PDFIn this paper we propose an accelerated convergence method, which is combined with the homotopy analysis method (HAM), to solve nonlinear problems. The HAM is applied to obtain approximate expressions. According to the numbers of terms in the approximations, some ratio-control parameters are introduced in the solution expressions. By solving simultaneous algebraic equations, all artificial parameters can be optimally identified, including the so-called convergence-control parameter ℏ. Twoexamples are given to illustrate the validity of the new method. Comparison with L-P perturbation method and Runge-Kutta method reveals that the improved HAM is better than the standard HAM and applies especially to the problems with complicated nonlinear terms
Rapid early damage detection using transmissibility with distance measure analysis under unknown excitation in long-term health monitoring
Get PDFAccurate and efficient damage detection in long-term health monitoring for structures still encounters many difficulties due to the effect of environment. Furthermore, recorded big data requires efficient damage detection algorithm. In this study, an efficient and effective damage detection algorithm is proposed using transmissibility along with Mahalanobis distance and Hotelling T-square. A numerically simulated beam and an experimentally tested laboratory structure are used to validate the proposed algorithm. Results demonstrate good performance of the proposed technique in damage detection
Kineto-dynamic optimization of seat-suspension
Get PDFA kineto-dynamic model of a cross-linkage air seat-suspension system is formulated to obtain relations for effective vertical suspension stiffness and damping characteristics. A two-stage optimization methodology is proposed to derive vehicle-specific optimal designs considering different classes of earthmoving vehicles. The results show that optimal air spring coordinates can yield nearly constant natural frequency during the deflection cycle, irrespective of the seated body mass and driver-selected seated height. Vehicle-specific optimal damping characteristics, identified in the second stage, provided substantial reductions in seat effective amplitude transmissibility (SEAT) and vibration dose values (VDV) for all classes of earthmoving vehicles considered in the study. The proposed kineto-dynamic model and optimization method could thus serve as an important tool for designing vehicle-specific suspension seats
Fault severity assessment of rolling element bearings based on bicoherence spectrum
Get PDFThe condition monitoring and fault diagnosis of rolling element bearings not only depend on fault type but also fault severity which is also essential for making proper maintenance decision. Aiming at fault severity assessment of rolling element bearings, a new indicator based on the bicoherence spectrum is proposed. The quadratic phase coupling (QPC) which is one of the most important nonlinear characteristics of fault-related signals can be detected by the bicoherence spectrum. The deepening fault severity usually results in more frequency components involving in coupling. In order to quantify the coupling degree which is closely related to fault severity, we choose the mean value of the bicoherence spectrum as an indicator. Experiments results showed that the quantitative trend prediction of different fault severities of bearing is realized
Study on three axis vibration measurement technology of roller bearing
Get PDFTo evaluate vibration level of a tapered roller bearing fully, a new measuring method is proposed, which can cover the vibration acceleration in three directions simultaneously. In the paper, a concept of primary vibration will be presented for three axis vibration picked up from an outer ring of bearing, and the corresponding vibration acceleration measuring system will be introduced. Experimental data will be given to illustrate the advantage of the new measuring technology in the evaluation of bearing vibration level. The research results show that the presented measuring method will be more valuable in evaluating the vibration level of tapered roller bearing used in a precision machine system
Modeling and analysis of performance degradation of bolted composite lap geometries subjected to shock load
Get PDFAn analytical model and 3D finite element analysis (FEA) is completed to determine the effect of shock loading on vibration characteristics and stiffness of composite laminates. The bolted carbon composite lap geometry is prepared by varying number of bolts from 1 to 3 in a 500 mm width of plate. Analytically, it is a mass-spring based model where bolt(s), laminates and the clamped region are represented by a series of springs and masses. The obtained equations of motion contain information about geometrical parameters such as length, width, thickness and mass properties of composite plates. The frequency response acquired from mathematical model is compared and validated with FEA results acquired through ANSYS. Conclusions reveal that the main contributing factors to cause changes in stiffness and reduction in frequency are presence of bolts, increase in number of bolts and regions of stress concentration. Moreover, the acquired frequency response may act as a means of detecting changes in structural stiffness and the applied methodologies might be used to model larger mechanical and aerospace structures
Rolling bearing fault diagnosis using modified K-means cluster analysis
Get PDFRolling bearing is essential component of most rotating machinery, fault diagnosis of rolling bearing is significant for enhance the reliability of mechanical device. It is becoming a hot research topic recent years. There are some disadvantages for existing methods, like computing complex, long spending time and so on. In order to overcome these shortcomings of existing methods, this paper present a modified K-means cluster analysis which is used to bearing fault diagnostics. And the data of Case Western Reserve University are used to validate effectiveness of the proposed method