Research On Ultrasonic Testing Method Of Adhesive Quality Of Multilayer Structure Based On COMSOL

Multilayer bonded structure(steel structured shell-insulator rubber-lining rubber)is an important part of the solid rocket motor.It is easy to debond in the bonding process,which will damaage the integity of the bonding structure and affeect the safety of the engine.Thus,it is quite important to realize thee debonding detection of each layers to improve the stability of the engine.In the actualual debonding detection,the change of detection parameters will directly affect the final debonding distinguish.too deal with the issue,the finity element method is used to simulate the ultrasonic testing of multi-layer debonding model with different parameters in this paper.In this paper,according to the industrial requirements of shell insulation lining bonding quality,the bonding components are designed,the propagation principle of ultrasonic wave on each bonding surface is studied,and the detection effect of different modes of ultrasonic(longitudinal wave,transverse wave)detection methods on each debonding interface is compared through actual experiments.The echo signal is analyzed to verify the influence of ultrasonic testing parameters such as ultrasonic mode,excitation frequency and pulse width period on the echo amplitude.Then,combined with the finite element method,the steel rubber bonding model is established by using COMSOL simulation software.The propagation law of ultrasonic wave in the bonding model is simulated from three aspects of mesh mass,boundary constraint conditions and excitation signal,which verifies the effectiveness of the simulation.The effectiveness of the simulation.Finally,in view of the changes in the amplitude of the ultrasonic echo,simulation studies of different ultrasonic modes,Different defect sizes,different excitation frequencies,different bandwidth periods,and different incident angles are designed.By testing and analyzing the simulation experiment data we have acquired,the optimal detection effect of multilayer adhesive structure is achieved.The experimental results show that,in the choices of ultrasonic mode,the longitudinal wave is better than the transverse wave in the detection of one interface,and The transverse wave is better than the longitudinal wave in the detection of the two interfaces and can detect the debonding area of φ3mm.In the choice of excitation signal,2.5MHz is better than 1MHz and 5MHz.In the choice of pulse width cycle,3 cycles are better than 1 cycle and 5 cycles.In the choice of incident angle,When the steel thickness is 2mm,22±0.3° is the best detection angle.When the steel thickness changes within the range of 6mm,the detection angle decreases by 1±0.3° compared with the previous one for every 2mm thickness increase.This conclusion provides a numerical reference for further improving the efficiency of ultrasonic debonding detection.