【摘要】 采用有限元素法 ,分别数值计算了平底孔道、台阶式孔道和尖劈状孔道等 3种孔眼模型中不同中心频率 (10 0 k Hz、5 0 0 k Hz、1MHz)的散射超声脉冲波。计算结果表明 ,无论选用哪一种孔底模型 ,均可以得到较为明显的对应于孔底的声波信号。但是 ,孔道越不规则 ,使用的超声信号的主频越高 ,则孔底信号越差。为了兼顾孔底信号质量和信号采集、传输的代价 ,在未来的检测仪器中应采用尽可能低的测量频率 (低于 5 0 0 k Hz)更多还原

【Abstract】 In this paper, numerical computations are made on the scattering of ultrasonic pulse waves with different centroid frequencies of 100 kHz,500 kHz and 1 MHz in fluid filled finite length perforation by using Finite Element Method(FEM),where three kinds of models of perforation bottom, i.e., flat bottom, stepped bottom and acuminated bottom,are assumed to simulate the practical bottoms of perforation. The numerical simulations show that no matter what geometrical shapes of the perforation are there always exists the scattering signal corresponding to the bottom of perforation, while the more irregularity of perforation shape and the higher the centriod frequency, the much more degrade of the bottom signal.Giving attention to both the quality of bottom signal and the cost of data acquisition and transmission, the lower measuring frequency(lower than 500 kHz) of future instruments should be chosen.更多还原