DYNAMIC ANALYSIS OF SHELLS

Shell structures are indispensable in virtually every industry. Howeve r, in the design, analysis, fabrication, and maintenance of such struc tures, there ave many pitfalls leading to various forms of disaster. T he experience gained by engineers over same 200 years of disasters and brushes with disaster is expressed in the extensive archival literatu re, national codes, and procedural documentation found in larger compa nies. However, the advantage of the richness in the behavior of shells is that the way is always open for innovation. In this survey, we pre sent a broad overview of the dynamic response of shell structures. The intention is to provide an understanding of the basic themes behind t he detailed codes and stimulate, not restrict, positive innovation. Su ch understanding is also crucial for the correct computation of shell structures by any computer code. The physics dictates that the thin sh ell structure offers a challenge for analysis and computation. Shell r esponse can be generally categorized by states of extension, inextensi onal bending, edge bending, and edge transverse shear. Simple estimate s for the magnitudes of stress, deformation, and resonance in the exte nsional and inextensional states are provided by ring response. Severa l shell examples demonstrate the different states and combinations. Fo r excitation frequency above the extensional resonance, such as in imp act and acoustic excitation, a fine mesh is needed over the entire she ll surface. For this range, modal and implicit methods are of limited value. The example of a sphere impacting a rigid surface shows that pl astic unloading occurs continuously. Thus, there are no short cuts; th e complete material behavior must be included. (C) 1995 John Wiley & S ons, Inc.