SUMMARYA new three-node triangular shell element is developed by combining the optimal membrane element and discrete Kirchhoff triangle (DKT) plate bending element, and is modified for laminated composite plates and shells so as to include the membrane-bending coupling effect. Using appropriate shape functions for the bending and membrane modes of the element, the 'inconsistent' stress stiffness matrix is formulated and the tangent stiffness matrix is determined. Non-linear analysis of thin-walled structures with geometric non-linearity is conducted using the corotational method. The new element is thoroughly tested by solving few popular benchmark problems. The results of the analysis are compared with those obtained using existing membrane elements.
Vibration suppression of laminated composite beams using the smart structures concept is presented in the present work. The smart system consists of a laminated composite beam as the host structure and piezoceramic and PVDF patches as the actuation and sensing elements. To treat the material and geometric inhomogeneities through the thickness of the laminated smart structure, a finite element model based on the layerwise displacement theory which incorporates the electro-mechanical coupling effects has been developed. The state space model of the active laminated beam is then used to design the control system. A linear quadratic regulator (LQR) controller is designed to achieve vibration suppression of the laminated smart beam. The effects of the laminate configuration and locations of sensors/actuators on controlled response are investigated. An experimental set-up has been developed to determine the natural frequency and damping factor of the smart laminated beam. The experimental measurements are then used to design a control mechanism with LQR to suppress the vibration response of the system. Open-loop and closed-loop responses of the system have been obtained experimentally and compared with the corresponding simulation results to demonstrate the accuracy and efficiency of the present approach in the vibration control of laminated smart structures.
The objective of this paper is the development of an efficient intelligent diagnostic procedure that considers several diagnostic indices for the quantification of developing faults and for monitoring machine condition. In this procedure, the condition monitoring is performed based on the on-line vibration measurements, and further, the fault quantification is formulated into a multivariate trend analysis. Self-organizing neural networks are then deployed to perform the multivariable trending of the fault development. The attributes for the disordering of “knots” in the trend analysis are determined. The disordering of neural network units is then eliminated by suitably altering the self-organizing neural network algorithm. Applications of this diagnostic procedure to the condition monitoring and life estimation of a bearing system are fully developed and demonstrated. The efficiency and advantages of the intelligent diagnostic procedure in precisely monitoring and quantifying the fault development are systematically brought out considering this bearing system.
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