VIBRATION ANALYSIS ON A COMPOSITE BEAM TO IDENTIFY DAMAGE AND DAMAGE SEVERITY USING FINITE ELEMENT METHOD

摘要

The objective of this paper is to develop a damage detection method in a composite cantilever beam with an edge crack has been studied using finite element method. A number of analytical, numerical and experimental techniques are available for the study of damage identification in beams. Studies were carried out for three different types of analysis on a composite cantilever beam with an edge crack as damage. The material used in this analysis is glass-epoxy composite material. The finite element formulation was carried out in the analysis section of the package, known as ANSYS. The types of vibration analysis studied on a composite beam are Modal, Harmonic and Transient analysis. The crack is modeled such that the cantilever beam is replaced with two intact beams with the crack as additional boundary condition. Damage algorithms are used to identify and locate the damage. Damage index method is also used to find the severity of the damage. The results obtained from modal analysis were compared with the transient analysis results.The vibration-based damage detection methods are based on the fact that changes of physical properties (stiffness, mass and damping) due to damage will manifest themselves as changes in the structural modal parameters (natural frequencies, mode shapes and modal damping). The task is then to monitor the selected indicators derived from modal parameters to distinguish between undamaged and damaged states. However, the quantitative changes of global modal parameters are not sufficiently sensitive to a local damage. The proposed approach, on the other hand, interprets the dynamic changes caused by damage in a different way. Although the basis for vibration-based damage detection appears intuitive, the implementation in real structures may encounter many significant challenges. The most fundamental issue is the fact that damage typically is a local phenomenon and may not dramatically influence the global dynamic response of a structure. For example, it is a common view that the frequency reduction has significant limitations for damage indication although the sensitivity varies from one structure to another. Therefore, damage may be difficult to detect until it becomes significantly severe.