Strain Modal-Based Damage Identification Method For Thin-Walled Structure

Thin plates and shells structures are widely used in the aerospace fields, such as rocket tanks, wings and fuselage. These thin-walled structures, as main bearing structure, have to carry complex loads in the service process. These loads would thus easily lead to performance degradation or produce structural damage. Therefore, developing damage identification methods for thin-walled structures is important to ensure the structural integrity. Strain modal analysis is used to estimate the stress distribution of composite plate and metal barrel under free vibration. We try to use method of damage identification based on strain modal analysis to estimate composite plate and metal barrel with single damage or multi-damage. As the inherent nature of structure, strain modal can be analysed and processed for status information. Comparing with displacement modal, strain modal is more sensitive to local or tiny damage of structure on non-modal nodes. So it’s high practical significance to research structure damage identification using strain modal theory. Works of this paper are as follows:(1) This article discusses a method based on strain modal analysis to identify damages, three different methods are used to deduce strain modal calculation formula of thin-walled structure, and strain modal is obtained using different physical quantities. Preliminary exploration of the sensor network layout method is used to obtain relevant physical quantities. Free vibration problem is studied and a formula is derived to calculate the analytical solution of free vibration of the fundamental frequency.(2) ANSYS is used in simulation tests of damage identification. Damage indicator and order of strain modal are key factors. These two factors were analysed in simulation tests in single damage and multi-damage situations. We built different damage indicators using strain modals gotten from sampling points pre-determined, and see what’s the difference in damage identification. The result demonstrates that the damage indicators based on strain modal are sensitive to damages and they performed differently on single damage and multi-damage situations. Damage indicators based on modal information from different orders have different performances, too. We can identify damages on composite plate and metal barrel using information of lower order based on strain modal method.