Study On Dry-coupling Method For Quality Detection Of Multilayer Adhesive Structure Of Solid Rocket Motor

Solid rocket motor bonding quality directly affects the overall performance of the rocket motor.Therefore,the solid rocket motor interface bonding quality detection method has important research significance.At present,the detection technology of interfacial bonding quality of solid rocket motors are various,and ultrasonic testing is the most widely used non-destructive testing method favored by many researchers.Traditional ultrasonic testing requires the use of water or oil as the coupling agent,but it is difficult to clean once it is used.In particular,the new solid rocket motor widely adopts the composite shell structure.The coupling agent is easy to contaminate the structure,what’s more,it may affect the physical structure and chemical properties as well,thus which can affect the structural integrity.Therefore,it’s necessary to find an ultrasonic detection method for a solid rocket motor housing structure which does not require a coupling agent.Ultrasonic detection of the solid rocket motor housing structure will excite Lamb waves.This paper studies the Lamb wave propagation mechanism.Lamb’s dispersion equation is obtained.In addition,the principle of vibration of the tri-laminate vibrator of the main transducer element of the detection probe has been explored.According to the thin plate theory,the Hamiltonian principle is used to derive the series and parallel differential equations of the tri-laminate vibrator.Determining the connection conditions and boundary conditions,solving the equation through Matlab software,and obtaining the effect of the material of the tri-laminate vibrator element on the vibration.And using ANSYS software to simulate and obtain the vibration characteristics of tri-laminate vibrator.Finally,two-dimensional models and three-dimensional models of single-layer and double-layer thin plates are established using COMSOL software,and defects are analyzed by echo method,standard transceiving method,and time reversal method.A dry-coupled ultrasound imaging detection system is established and constructed,moreover a Lamb wave defect imaging detection method based on time reversal is proposed.In this paper,the multimodal characteristics of Lamb wave propagation are defined by Lamb wave dispersion curve,which provides an accurate theoretical basis for detection signal selection and defect identification.Then the vibration characteristics of the tri-laminate vibrator are clarified.It is showed that the resonant frequency increased with the increase of the metal sheet’s thickness;Hard-aluminum is the best metal material;The best choice for piezoelectric ceramics is PZT-5;When the thickness is equal to the thickness of the piezoelectric ceramic,the electromechanical coupling coefficient is the largest and the piezoelectric transducer has the highest energy conversion efficiency.It’s find that the echo method and standard transceiver method have better recognition effects for single-layer thin plates by the simulation of those defects.However,it is difficult to identify double-layer thin plates.Then a defect recognition method based on time reversal method is proposed.The defect is evaluated by DI_sp damage factor.It is indicate that the damage factor increased with the increase of defect size.A six-probe detection network is constructed and a damage-based imaging method based on time reversal method is used.The simulation and experiment of damage imaging for the simulated debonded multi-layer composite specimens are performed.Both of them are able to distinguish the defects and the good regions.