超声波在BT20钛合金中的传播特性及熔池中超声场的分布研究

Propagation Characteristic of Ultrasonic in BT20 Titanium Alloy and Research on Distribution of Ultrasonic Field in Molten Pool of Laser Deposition Repair

通过ANSYS有限元软件数值模拟和实验相结合，研究了超声波在BT20钛合金修复件和熔池中的传播特性。结果表明，在变幅杆做纵向振动的前提下，当与其耦合的修复件长度小于变幅杆上纵波波长的23％时，修复件表面振动为纵向振动；当修复件长度大于波长的28％时，其表面变为弯曲振动；随着修复件长度的增加，其谐振频率也在纵波波长的23％～28％范围内出现跳跃并重新分布；且在两种不同类型的振动中，随着修复件长度的增加，谐振频率都出现递减的趋势；在熔池中施加频率为19．56kHz、振幅为0．2μm的超声振动后，其内部出现周期性交替变化的正负声压，负压值可达到几十万帕。

The propagation characteristic of ultrasonic in repaired components of BT20 titanium alloy and molten pool is investigated by using ANSYS finite element simulation and experimental test. Under the circumstance that the horn vibrates longitudinally, the results show that when the length of repaired component coupled with horn is less than 23% of the longitudinal wavelength, the type of ultrasonic vibration on the surface of repaired component belongs to longitudinal vibration; however, when the length of repaired component is more than 28 % of longitudinal wavelength, the type of ultrasonic vibration belongs to bending vibration; With the length of repaired component increasing, resonant frequency changes a lot and redistributes when the length of repaired component is between 23% and 28% of the longitudinal wavelength. In the two different kinds of vibrations, as the length of repaired component increases, the resonant frequency declines. When ultrasonic vibration is loaded at a frequency of 19.56 kHz, with amplitude of 0. 2 μm, the positive and negative acoustic pressure in the molten pool changes alternatively and the negative pressure reaches hundreds of thousands of pascals.