Abstract
This paper proposes the advancement of residual stress evaluation technology, utilizing the ultrasonic acoustoelastic theory by detecting the variation of wave speed under different stress conditions. The target structure for nondestructive evaluation task is a typical multilayer, viscoelastic composite shell of a solid rocket motor. By carrying out an in-depth theoretical analysis with Finite Element Modeling (FEM), the sensing sensitivity of the probing ultrasonic wave characteristics are studied systematically. The effective generation of interface guided wave modes is investigated, where the pure wave mode excitation is accomplished. To monitor the residual stress state, a theoretical model is established by considering the stress gradient in each layer, indicating the current stress condition inside the testing object. Consequently, via the comprehensive consideration of transducer dimensions, center frequency, and the signal attenuation, the most effective residual stress monitoring setup is established and the sensing signals are recorded by piezoelectric wafer active sensors (PWAS) placing on the object. Finally, different values of prestress are applied to the object, while the nonlinear constitutive law of the layered materials is implemented. The pattern between the sensing signal and the residual stress state is identified. The amplitude and the Time of Flight (TOF) of sensing signals could provide indicative information for evaluating the residual stress state based on the acoustoelastic effects, including the change of wave speed under various prestress loading conditions. The findings of this research possess superb application potential for the evaluation of residual stresses in multilayer composites for enhancing manufacturing quality and avoiding unexpected failures in solid rocket motor industry. This paper finishes with summary, concluding remarks, and suggestions for future work.
