Dynamic Characteristics Analysis Andexperimental Study Of The Ultrasonic/Sonic Driller/Corer (USDC)

With the development of space technology,deep space exploration has become the main field of human space activities.Among them,the sampling of the extraterrestrial bodies is a key part of the deep space exploration mission.The ultrasonic/sonic driller/corer(USDC)based on the acoustic / ultrasonic energy coupling because of its unique advantages(light weight,simple mechanical structure,low energy consumption,etc.)has broken through the limitation of the outer space severe environment(low gravity,large temperature difference,radiation,etc.),detector carrying capacity and working platform space.So it can be easily installed unmanned detectors,to achieve the unmanned sampling task on the outer space Planet.The research of the USDC has become a hotspot in deep space exploration.In this paper,the theoretical analysis and experimental study on the dynamic characteristics of the USDC are carried out.The specific research contents are as follows:Based on the one-dimensional wave theory,the longitudinal vibration equation of the drill bit is solved to analyze the influence of the exciting force characteristic on the dynamic characteristics of the sonic / ultrasonic drill bit.The result is used to study the dynamic characteristics of ultrasonic sampling drilling system.The results show thatthe amplitude of the displacement of the drill string increases with the increase of the length,and its maximum dynamic stress is almost constantunder the excitation force whose amplitude does not changes with frequency change.The amplitude of the displacement and the maximum dynamic stress of the drill string decreases with the increase of the resonant mode.However,the amplitude of the displacement field and the maximum dynamic stress of the drill string decrease with the increase of the lengthunder the excitation force the amplitude changes with the frequency change.Considering the special working principle of the USDC,the factors that affect the working performance of the USDC are analyzed theoretically,including the structure parameters of drill bit,the free mass and the connection method.And drilling experiments are carried out to analyze the influence of the length parameter of drill bit on the drilling effect and the influence of the weight of free mass on the energy coupling.The results show thatthe natural frequency of the longitudinal vibration of the drill bit is the same as or similar to the resonant frequency of the ultrasonic actuator.In other words,the drill bit is designed according to the half wave oscillator.Whilethe free mass can significantly improve the performance of the ultrasonic sampling drill,with an increase of up to 48% under the same conditions.Andthe weight of the free mass has a certain influence on its drilling effect.The free mass has an optimal energy coupling for a particular length of drill bit.Based on the above research,the theoretical basis for further study of the USDC is provided.And it is used to lay a foundation for the study of the mechanism of rock fragmentation by the USDC and the application of sonic/ultrasonic technology.