Several Issues Of Ultrasonic Waves For Hypervelocity Impact Sensing And Identification Of Debris Cloud Induced Damage

Manned spacecraft,especially those large-scale,long-during,high-reliability spacecraft such as the Space Station,facing the threat of hypervelocity impact(HVI)from micrometeoroids/orbital debris(MMOD)during their on-orbit servicing.Among which,those dangerous MMOD at centimeter level which can neither be“avoided ” by orbital maneuvering nor “defensed ” by Whipple structures,as well as millimeter-scale MMOD with the risk of penetrating the Whipple structures and impacting the shell strucures,needs most urgent attention.Thus,to perceive the MMOD impact event,locate the impact position,and identify the damage modality and severity are important prerequisites for making remedial measures of spacecraft damage or astronaut escape strategies.For this practical engineering requirement,a variety of on-orbit sensing technologies(OSTs)have been developed up to now,which including three main functions: i.e.,“perceive”,“locate” and “identify”.Among them,the passive acoustic emission(AE)based OST has a good application prospect.However,due to the high transient characteristic and complexity of HVI,less research focus on the dynamic generation mechanism of HVI-induced AE waves.In addition,owing to the limitations of experimental conditions,projectile/target parameters,etc.,there are still a lack of works on the quantitative propagation characteristics of AE waves in the large-scale and complex special-shaped structures,as well as the disturbance effects of noise and temperature in the space environment.In particular to the manned spacecraft equipped with Whipple structures,identification of debris cloud HVI-induced multi-source distributed “clouding damage”in the shell structures of spacecraft confronts a big challenge at present,and related works are still blank.Based on the above background,this thesis aims at the development of OST for the typical manned spacecraft.Accordingly,this research gains insight into several key and changllenge issues of ultrasonic waves associated with OST,i.e.,the dynamic generation mechanism of HVI-induced AE waves,the propagation characteristics of AE waves in special-shaped structures,the characteristic identification of AE waves under noise disturbance,the disturbance effect of multi-source distributed clouding damage on the nonlinear ultrasonic waves(NUWs),and the environmental temperature effect on the NUWs-based identification,etc.Focusing on the above issues,this thesis intends to combine the advantages of “passive” AE waves and “active” NUWs,the former can rapidly response and online real-time detect,the latter can repeatably detect and is sensitivity to small damage,etc.,to carry out research on HVI sensing and debris cloud-induced damage identification technologies.The main works are as follows:A parameterized equivalent model of acoustic source force(EMAF)is proposed,which demonstrates the characteristics of HVI-induced AE waves.On this basis,the influence laws and mechanisms of the projectile/target parameters on the modal excitability and energy ratio of AE waves are explained.The “near-field”shock wave amplitude distribution characteristics reflecting the projectile/target parameters along the plate thickness direction are obtained by analyzing the dynamic process of spherical projectiles HVI the metal plates using numerical simulation.According to the destruction behaviour between projectiles and targets,combining with the propagation time delay characteristics of the shock wave front and the spherical wave characteristics,the geometric boundary of the elastic-plastic zone is obtained.Thus the distribution of the “far-field” acoustic source force on the boundary is determined.Accordingly,the EMAF at “far-field” is established,then the influence laws and mechanisms of the projectile/target paramet ers on the modal excitability and energy ratio of AE waves are obtained and explained.The results show that the HVI-induced AE wave is a kind of “far-field” elastic wave,which mainly includes five modes,i.e.,S0,A0,A1,S1 and S2.The symmetric modes S0,S1 and S2 are mainly generated by the EMAF along the in-plane direction.The antisymmetric modes A0 and A1 are mainly generated by the EMAF along the out-of-plane direction.The narrower the pulse width of the EMAF,the easier it is to excite high-frequency modes.The characteristic amplitude of the A0 mode is approximately proportional to the shock loading in the out-of-plane direction,and the S0 mode is approximately proportional to the in-plane direction shock loading.Thses achievements have laid a theoretical foundation for the quantitative analysis of AE wave propagation characteristics and the design of feature parameters in the process of guiding the development of “perceive” and “locate” modules.A parameterized attenuation model is established,which uses the amplitude of the fastest wave packet and the maximum energy of the coda wave as feature parameters,to characterize the variation of the AE waves with the projectile/target parameters,realizing the quantification of the attenuation charact eristics of the AE waves in the typical special-shaped structure of spacecraft.The propagation characteristics of each mode and frequency component of the AE wave in the special-shaped structure,such as scattering,mode conversion and attenuation,are obtained using numerical simulation.Thus,the parameterized attenuation model,reflecting the variation of impact velocity,propagation distance,stiffener form and quantity,etc.,is proposed and established.A series of experimental results of HVI on typical special-shaped structures show that the fitting accuracy of the proposed model to is higher than 91%,when the amplitude of the fastest wave packet is taken as the feature parameter.In addition,the fitting accuracy of the proposed model is higher than 93% for various stiffened plates,when the maximum energy of the coda wave is taken as the feature parameter,while the fitting accuracy for other structures are poor.These findings have laid a technical foundation for guiding the layout of sensor networks on spacecraft and the designing of feature parameters of “perceive”and “locate” modules,and realizing the development of functional modules such as rapid “perceive” and accurate “locate”.A simple and fast identification algorithm based on a single c haracteristic parameter and a multi-source classification and identification algorithm based on artificial intelligence(AI)are developed for engineering requirements.AE wave signals are obtained by carrying out a series of HVI and noise simulation experiments,then appropriate feature parameters are designed and optimized.On this basis,a simple and fast identification algorithm with low computational efficiency requirement is developed,as well as the AI-based multi-source classification algorithm.The results show that the simple and fast identification algorithm has a success rate of over 90% for the identification of two types of AE events,such as HVI and noise interference,and the risk false alarm rate is 2.22%.But its ability to classify multi-source AE events is poor.The AI-based identification method can accurately classify multi-source AE events,and the success rate is as high as 99%,which effectively improves the identification success rate and reduces the risk of missed reports.These achievements provide a technical support for further improving the “perceive” module and promoting its engineering application.Based on the perturbation effect of the various types of clouding damage sources and their distribution characteristics on NUWs,an “active” evaluation method is proposed to quantitatively evaluate the multi-source distributed clouing damage severity and spatial distribution characteristics in the plate-like structure.Through material characterization,theoretical analysis and numerical simulation,the macro-and micro-damage source types and distribution characteristics of clouding damage are obtained,then the semi-analytical model and finite element model of their effect on NUWs disturbance are established,as well as the nonlinea r danage index(NDI).Furthermore,combining with the RAPID,an active evaluation method is proposed to quantitatively evaluate the severity and spatial distribution characteristics of clouding damage in plate-like structure.The results show that the pixel values in the reconstructed damage images can intuitively and quantitatively characterize the location,morphology and severity of damage caused by the normal and oblique impacts,which are in good agreement with the experimental photos.These findings have laid a theoretical foundation for the active evaluation of debris cloud-induced damage and the development of the “identify” module.Based on the perturbation effect of ambient temperatures on the NUWs,an“active” evaluation method is proposed to improve the identification accuracy of clouding damage status by temperature control.By theoretical analysis the macroscopic elastic modulus,Poisson’s ratio,density of the material medium,etc.,as well as the perturbation characteristics of microscopic interatomic potential under temperature,then the temperature sensitivity coefficients of the second-order and third-order elastic constants of the material are obtained,as well as the propagation and accumulation effect of nonlinear second harmonics,and the nonlinear temperature sensitivity factor TSI.On this basis,combining with the RAPID,an active evaluation method is proposed to improve the identification accuracy of clouding damage severity and distribution characteristics through temperature control,realizing the identification and intuitively quantitative characterization of the accumulated damage induced by debris cloud multiple impacts.The results show that with the increase of temperature,the greater the TSI value obtained on the path with more severe clouding damage,the changing of TSI is easily highlighted,and the reconstructed damage images are more consistent the experimental photos.This method improves the clouding damage identification accuracy and reliability by temperature control when other nonlinear sources interference.These findings provide technical support for promoting the engineering application of the “identify”module.In summary,this research gains insight into several key and changllenge issues of ultrasonic waves associated with HVI sensing and debris cloud-induced damage identification,and the main achievements as follows: proposed a parameterized EMAF,established a parameterized attenuation model of AE waves,developed a method to quantitatively evaluate the severity and spatial distribution characteristics of multi-source distributed clouding damage in plate-like structure,and proposed an active evaluation method to improve the identification accuracy of clouding damage status by temperature control.These achievements lay a foundation for further deepening and improving the OST integrating “detect”,“locate” and “assess”,which has important guiding significance for future engineering application in typical manned spacecraft,high-value satellites,and pressure vessels and other important parts and components of spacecraft,etc.