Search

Copyright of Journal of Vibration Engineering is the property of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work investigates the possibility of using the ratio of singular value for bearing fault detection. The existing simple time domain methods are affected by variation of sample points. Also, they have not been shown to be effective in presence of noise. The present work overcomes the above issues. Singular value decomposition of the bearing vibration signal is obtained under healthy and different fault conditions. The dominant singular values are selected based on the singular value plot. The ratio of these singular values is used as fault index which is found to be having a constant value for faulty bearing and another range of values for healthy bearing. The method is tested with experimental data obtained for different bearing fault types, with increasing fault severity and at various load. The effect of load, fault size, sample points and noise are studied on the fault index. The advantages of the proposed method are shown in comparison with the existing simple time domain techniques. [ABSTRACT FROM AUTHOR]

The moving vehicle loads on a bridge deck is one of the most important live loads of bridges. They should be understood, monitored and controlled before the bridge design as well as when the bridge is open for traffic. A MOM-based algorithm (MOMA) is proposed for identifying the time-varying moving vehicle loads from the responses of bridge deck in this paper. It aims at an acceptable solution to the ill-conditioning problem that often exists in the inverse problem of moving force identification. The moving vehicle loads are described as a combination of whole basis functions, such as orthogonal Legendre polynomials or Fourier series, and further estimated by solving the new system equations developed with the basis functions. A number of responses have been combined, some numerical simulations on single axle, two axle and multiple-axle loads, being either constant or time-varying, have been carried out and compared with the existing time domain method (TDM) in this paper. The illustrated results show that the MOMA has higher identification accuracy and robust noise immunity well as producing an acceptable solution to ill-conditioning cases to some extent when it is used to identify the moving force from bridge responses. [ABSTRACT FROM AUTHOR]

ABSTRACT: Computational methods are developed to simulate interactions of nonlinear waves with multi-structures through the finite element method based on second order and fully nonlinear theories. The three dimensional (3D) mesh with prism elements is generated through an extension of a two dimensional (2D) unstructured grid. The potential and velocity in the fluid field are obtained by solving finite element matrix equations at each time step using the conjugate gradient method with SSOR preconditioner. The combined Sommerfeld-Orlanski radiation condition and the damping zone method is used to minimize wave reflection. The regridding and smoothing techniques are employed to improve the stability of the solution and the accuracy of the result. The method is first used to simulate interactions of waves and an array of cylinders in the time domain based on the second order theory. Numerical simulations show that the influence of mutual interference between cylinders is highly significant. In particular, the first order and the second order results can become quite large when their corresponding wave number is close to the trapped mode. Simulations based on the fully nonlinear theory are also made for the 3D interactions between fixed multi-cylinders and waves generated by a piston type wave maker in a numerical tank with an artificial beach. Extensive results of practical importance have been obtained, which have been overlooked in many previous applications. The developed method is further employed to solve the 3D fully nonlinear radiation problems by multi-cylinders undergoing large amplitude oscillations in the open sea. All these different applications have clearly demonstrated the flexibility of the method. The simulations also show that the developed method is highly efficient and has great potential to be used for large scale calculation in the motions of floating structures in nonlinear waves. [Copyright &y& Elsevier]

Computational methods are developed to simulate interactions of nonlinear waves with multi-structures through the finite element method based on second order and fully nonlinear theories. The three dimensional (3D) mesh with prism elements is generated through an extension of a two dimensional (2D) unstructured grid. The potential and velocity in the fluid field are obtained by solving finite element matrix equations at each time step using the conjugate gradient method with SSOR preconditioner. The combined Sommerfeld-Orlanski radiation condition and the damping zone method is used to minimize wave reflection. The regridding and smoothing techniques are employed to improve the stability of the solution and the accuracy of the result.The method is first used to simulate interactions of waves and an array of cylinders in the time domain based on the second order theory. Numerical simulations show that the influence of mutual interference between cylinders is highly significant. In particular, the first order and the second order results can become quite large when their corresponding wave number is close to the trapped mode. Simulations based on the fully nonlinear theory are also made for the 3D interactions between fixed multi-cylinders and waves generated by a piston type wave maker in a numerical tank with an artificial beach. Extensive results of practical importance have been obtained, which have been overlooked in many previous applications. The developed method is further employed to solve the 3D fully nonlinear radiation problems by multi-cylinders undergoing large amplitude oscillations in the open sea. All these different applications have clearly demonstrated the flexibility of the method. The simulations also show that the developed method is highly efficient and has great potential to be used for large scale calculation in the motions of floating structures in nonlinear waves. [ABSTRACT FROM AUTHOR]