Vibration Characteristic Research Of Stochastic Damaged Stiffened Panel Based On Monte Carlo Stochastic FEM

As the ships and marine structures are very complicated and serving in the water, the damage caused by corrosion and fatigue under the heavy environment load and long service life will weaken global mechanics behavior of marine structures. Ocean environment loads include wind load, wave load and ocean current load etc., that are all stochastic. Therefore the damage caused by the loads is also stochastic. The study on mechanics behavior of stochastic damaged structures is significant in engineering.The modal parameters study of stiffened panel with stochastic damage in this thesis is discussed. FE equations of isotropic and orthotropic damage for stiffened panel are deduced. Basic theory of liner elastic mechanics is used for healthy zone, where the structure is not damaged. While, for unhealthy zone, where the structure is damaged, the element stiffness weakened after meshing. As the structure damage is stochastic, damage position is taken as damage parameters. According to the statistical data in engineering, normal distribution is assumed for the damage parameter. Modal parameters are then analyzed through stochastic FEM. This thesis is focused on the study of the effect of stochastic damage on modal parameters by defining a variation cofficent.Numerical study shows that the damage position has all influences on modal parameters, such as modal frequency and modal shape. The frequency chart of damaged structure, which also obeys normal distribution, descends. Further research for effect of stochastic damage to frequency, amplitude, phase, damping and resonance may introduce a kind of method to control structure damage development while controlling the dynamic response.