Wed, 09 Jul 2008 16:36:01 BST CiteULike: norris structural http://www.citeulike.org/user/norris/tag/structural CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/norris/article/898254 <i>The Journal of the Acoustical Society of America, Vol. 99, No. 6. (1996), pp. 3481-3487.</i><br /><br />The modal density of a structural component is a key parameter in high-frequency vibration prediction techniques such as statistical energy analysis (SEA). A study of the literature reveals that the standard method of computing the modal density of a two-dimensional component, such as a plate or shell, is restricted to orthotropic components. This method (which is usually referred to as Courant's method) is extended here to a generally anisotropic component by considering initially the case of periodic (or Born–von Kármán) boundary conditions. It is then shown that the resulting modal density is independent of the nature of the actual boundary conditions which act on the component. On a related issue, doubts have been expressed in the literature as to whether the results yielded by Courant's method are applicable to general boundary conditions if the component exhibits degeneracy of the dynamic edge effect; the present analysis demonstrates that the method is in fact valid in such cases. The developed technique is applied to the bending vibrations of an anisotropic plate, and good agreement is found with empirical results for the modal density derived from natural frequency computations. ©1996 Acoustical Society of America. The modal density of anisotropic structural components RS Langley doi:10.1121/1.415218 The Journal of the Acoustical Society of America, Vol. 99, No. 6. (1996), pp. 3481-3487. 2006-10-15T13:45:25-00:00 1996 The Journal of the Acoustical Society of America 99 6 3481 3487 ASA anisotropy random structural http://www.citeulike.org/user/norris/article/898253 <i>The Journal of the Acoustical Society of America, Vol. 117, No. 1. (2005), pp. 85-95.</i><br /><br />This analysis is concerned with the derivation of a "diffuse field" reciprocity relationship between the diffuse field excitation of a connection to a structural or acoustic subsystem and the radiation impedance of the connection. Such a relationship has been derived previously for connections described by a single degree of freedom. In the present work it is shown that the diffuse–field reciprocity relationship also arises when describing the ensemble average response of connections to structural or acoustic subsystems with uncertain boundaries. Furthermore, it is shown that the existing diffuse–field reciprocity relationship can be extended to encompass connections that possess an arbitrary number of degrees of freedom. The present work has application to (i) the calculation of the diffuse field response of structural–acoustic systems modeled by Finite Elements, Boundary Elements, and Infinite Elements; (ii) the general calculation of the Coupling Loss Factors employed in Statistical Energy Analysis (SEA); and (iii) the derivation of an alternative analysis method for describing the dynamic interactions of coupled subsystems with uncertain boundaries (a generalized "boundary" approach to SEA). ©2005 Acoustical Society of America. On the reciprocity relationship between direct field radiation and diffuse reverberant loading PJ Shorter RS Langley doi:10.1121/1.1810271 The Journal of the Acoustical Society of America, Vol. 117, No. 1. (2005), pp. 85-95. 2006-10-15T13:40:18-00:00 2005 The Journal of the Acoustical Society of America 117 1 85 95 ASA anisotropy random structural http://www.citeulike.org/user/norris/article/812843 <i>Applied Stochastic Models in Business and Industry, Vol. 16, No. 4. (2000), pp. 249-278.</i><br /><br />This paper contains an overview of recent development in asymptotic analysis of fields in multi-structures. We begin with simple examples of scalar dynamic problems in two dimensions, and then present analysis of time-dependent fields in 1D-3D multi-structures. The asymptotic results, presented here, are based on the method of compound asymptotic expansions. Copyright © 2000 John Wiley & Sons, Ltd. Dynamic singular perturbation problems for multi-structures VG Maz'ya AB Movchan doi:10.1002/1526-4025(200010/12)16:4<249::AID-ASMB418>3.0.CO;2-C Applied Stochastic Models in Business and Industry, Vol. 16, No. 4. (2000), pp. 249-278. 2006-08-22T16:17:12-00:00 2000 Applied Stochastic Models in Business and Industry 16 4 249 278 structural http://www.citeulike.org/user/norris/article/808491 <i>The Journal of the Acoustical Society of America, Vol. 119, No. 4. (2006), pp. 2141-2149.</i><br /><br />Through two complementary approaches, using modal response and wave propagation, the analyses presented here show the conditions under which a decaying impulse response, or a nearly irreversible energy trapping, takes place in a linear conservative continuous system. The results show that the basic foundation of near-irreversibility or apparent damping rests upon the presence of singularity points in the modal density of dynamic systems or, analogously, in the wave-stopping properties associated with these singularities. To illustrate the concept of apparent damping in detail, a simple undamped beam is modified to introduce a singularity point in its modal density distribution. Simulations show that a suitable application of a compressive axial force to an undamped beam placed on an elastic foundation attenuates its impulse response with time and develops the characteristics of a nearly irreversible energy trap. ©2006 Acoustical Society of America Near-irreversibility in a conservative linear structure with singularity points in its modal density A Carcaterra A Akay IM Koc doi:10.1121/1.2179747 The Journal of the Acoustical Society of America, Vol. 119, No. 4. (2006), pp. 2141-2149. 2006-08-19T20:55:17-00:00 2006 The Journal of the Acoustical Society of America 119 4 2141 2149 ASA acoustics structural