| Composite structures have been widely used in aerospace,ship and automobile fields due to their low specific gravity,high specific strength and large specific modulus.However,the composite structures are susceptible to low velocity impact which can cause delamination and fiber fracture.Such damages can lead to the mechanical properties reduction of composite structures.Thus it is great necessary to monitor impact of composite structures.Nevertheless,Lamb waves are commonly influenced by external factors because of the complex service environment of composite structures.This paper mainly studies the impact location methods in time-varying environment,such as vibration,varying temperature and stress.The main research work includes the following aspects:(1)The experiments of vibration environment(constant vibration and inconstant vibration),varying temperature environment(constant temperature environment and inconstant temperature environment)and stress environment(tensile environment and deformation environment)are designed to study the environmental effects on array signals.This work provides the research foundation for improvement of follow-up algorithms.(2)To deal with the problem that the sensor array signals are commonly polluted by noises in the vibration environment,an adaptivefilter enhanced multiple signal classification method is proposed for impact localization of composite structures in vibration environment.(3)Since the sensor array signals phase drift are induced by varying temperature environment,the multiple signal classification method based on phase correction is developed to improve the localization accuracy in varying temperature environment.(4)Aim at the problem that sensor array signals are easily disturbed by stress environment,the impact source localization method based on Toeplitz approximation method and multiple signal classification is presented to locate impact quickly of composite structures in stress environment. |
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