tailieunhanh - Influence of edge crack on frequencies of thin plate in bending

This paper investigates the influence of crack location and crack length on changes in natural frequencies of bending thin plate. To perform this analysis, a computing program called CRACK-PLATE, using the finite element method based on the RessnerMindlin' theory of plate is developed. | Vietnam Journal of Mechanics, VAST, Vol. 27, No. 2 (2005), pp. 107 - 117 INFLUENCE OF EDGE CRACK ON FREQUENCIES OF THIN PLATE IN BENDING NGUYEN THI HIEN LUONG AND VUONG QUANG G I ANG Ho Chi Minh City University of Technology Abstr act . This paper investigates the influence of crack location and crack length on changes in natural frequencies of bending thin plate. To perform this analysis, a computing program called CRACK-PLATE, using the finite element method based on the RessnerMindlin' theory of plate is developed. In order to achieve a high accuracy, an isoparametric element of Barsoum is combined with an 8-node quadrilateral isoparametric element. The numerical results show that the natural frequencies are very sensitive to the crack presence in the bending thin plate. This study is a basis for crack identification based on natural frequencies of plates. · Key words. Bending cracked plate, frequency, finite element method, Ressner-Mindlin' theory of plate, element of Barsoum. 1. INTRODUCTION Crack has great influence on load carrying capacity and lifetime of structures. The problem of exact determining the crack position and depth is very important, from there; one can predict the real capacity of structures and propose a timely solution to prevent damages. In recent years, several authors have carried out natural frequency analysis of cracked beams [1-2] to detect the presence of a crack in beams, and determine its location and size, based on experimental dynamic analysis results . Meanwhile, crack detection in plates has been little mentioned. Cawley and Adams [3] introduced an effective method of nondestructively assessing the integrity of structures using measurements of t he structural natural frequencies obtained from t ests on an ~·l uminum plate . Recently, Wu an:d Law [4] proposed a damage localization method for two-dimensional plate structures, based on changes in uniform load surface (ULS) curvature. However, these studies are .