R Sivaprasad^1,2, S Venkatesha¹, C S Manohar^1,3

CMC-Computers, Materials & Continua, Vol.9, No.3, pp. 179-208, 2009, DOI:10.3970/cmc.2009.009.179

Abstract The problem of identifying parameters of time invariant linear dynamical systems with fractional derivative damping models, based on a spatially incomplete set of measured frequency response functions and experimentally determined eigensolutions, is considered. Methods based on inverse sensitivity analysis of damped eigensolutions and frequency response functions are developed. It is shown that the eigensensitivity method requires the development of derivatives of solutions of an asymmetric generalized eigenvalue problem. Both the first and second order inverse sensitivity analyses are considered. The study demonstrates the successful performance of the identification algorithms developed based on synthetic data on More >

F. Cosmi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.3, pp. 187-196, 2008, DOI:10.3970/cmes.2008.027.187

Abstract The Cell Method is a recent numerical method that can be applied in several fields of physics and engineering. In this paper, the elastodynamics formulation is extended to include system internal damping, highlighting some interesting characteristics of the method. The developed formulation leads to an explicit solving system. The mass matrix is diagonal (without lumping) and in the most general case a time-dependent damping coefficient can be defined for each node. \newline Accuracy and convergence rate have been tested with reference to the classical problem of a particle free vibration with viscous damping.
An application More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.3, pp. 137-150, 2008, DOI:10.3970/cmes.2008.027.137

Abstract For the inverse vibration problem, a Lie-group shooting method is proposed to simultaneously estimate the time-dependent damping and stiffness functions by using two sets of displacement as inputs. First, we transform these two ODEs into two parabolic type PDEs. Second, we formulate the inverse vibration problem as a multi-dimensional two-point boundary value problem with unknown coefficients, allowing us to develop the Lie-group shooting method. For the semi-discretizations of PDEs we thus obtain two coupled sets of linear algebraic equations, from which the estimation of damping and stiffness coefficients can be written out explicitly. The present More >

Chein-Shan Liu¹, Jiang-Ren Chang², Kai-Huey Chang², Yung-Wei Chen²

CMC-Computers, Materials & Continua, Vol.7, No.2, pp. 97-108, 2008, DOI:10.3970/cmc.2008.007.097

Abstract For the inverse vibration problem a mathematical method is required to determine unknown parameters from the measurement of vibration data. When both damping and stiffness functions are identified, it is a rather difficult problem. In this paper we will propose a feasible method to simultaneously estimate both the time-dependent damping and stiffness coefficients through three mathematical transformations. First, the second-order equation of motion is transformed into a self-adjoint first-order system by using the concept of integrating factor. Then, we transform these two ODEs into two hyperbolic type PDEs. Finally, we apply a one-step group preserving More >

Pramod Kumar¹, Rakesh Chandra¹, S.P. Singh²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.2, pp. 67-72, 2007, DOI:10.3970/icces.2007.004.067

Abstract Polymers composite are modeled as fiber, interphase and matrix. Interphase properties are very crucial for bonding between fiber and matrix. Interphase can be strong and weak depending upon its properties. Damping of composite material depends on interphase properties and required damping can be obtained by varying the properties of interphase. In this paper three phase mathematical model has been proposed for the evaluation of damping incorporating the effect of fiber packing. Effect of interphase has been analysed for the longitudinal loss factor, transverse loss factor, transverse shear loss factor and longitudinal shear loss factor. Results More >

D. Moens¹, M. De Munck, D. Vandepitte

CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 129-150, 2007, DOI:10.3970/cmes.2007.022.129

Abstract Recently, an interval finite element methodology has been developed to calculate envelope frequency response functions of uncertain structures with interval parameters. The methodology is based on a hybrid interval implementation of the modal superposition principle. This hybrid procedure consists of a preliminary optimization step, followed by an interval arithmetic procedure. The final envelope frequency response functions have been proved to give a very good approximation of the actual response range of the interval problem. Initially, this method was developed for undamped structures. Based on the theoretical principles of this approach, this paper introduces a new… More >

A. H. Muhr¹

CMC-Computers, Materials & Continua, Vol.5, No.1, pp. 11-30, 2007, DOI:10.3970/cmc.2007.005.011

Abstract The mechanics of laminates of elastomer and shims of high modulus material are reviewed. Such structures are often built to provide engineering components with specified, and quite different, stiffnesses in different modes of deformation. The shims may either be rigid or flexible, flat or curved, but are usually close to inextensible, being made of a high modulus material such as steel. On the other hand, rubber has an exceptionally low shear modulus, about one thousandth of its bulk modulus, so that shear of the rubber layers and flexure of the high modulus layers (if thin)… More >

Asciutto¹ K, MC Rivera¹, ER Wright¹, D Morisigue², MV López³

Phyton-International Journal of Experimental Botany, Vol.75, pp. 115-123, 2006, DOI:10.32604/phyton.2006.75.115

Abstract Rhizoctonia solani damping-off and root rot diseases are frequent in impatiens crops in Buenos Aires. Their control is based in fungicide use. In a sustainable nursery production, beneficial microorganisms that develop in organic amendments may suppress diseases and promote plant growth. The aim of this work was to evaluate the effect of different proportions of vermicompost on the growth and health of patience-plant (Impatiens wallerana). The experiment was carried out in a polyethylene greenhouse. Treatments were defined as follows: infested substrate, substrate, sterilized substrate, vermicompost, and vermicompost mixed with infested substrate at 75, 50 and 25% by More >