基于压电陶瓷片的Lamb波单模态激励及缺陷检测的实验研究

摘要

To excite single S0 mode and single A0 mode of Lamb waves,two same piezoelectric ceramic wafers of which diameter is 14 mm and thickness is 0.8 mm bonded in the PMMA plate symmetrically are applied as actuators,and a piezoelectric ceramic wafer of the same size arranged in another position is applied as the sensor.In the frequency range of below 100 kHz,according to pitch-catch arrangement,the actuator excites Lamb waves alone or two actuators excite Lamb waves in parallel symmetrically or antisymmetrically.And then the change of mode components in the signals received by the sensor is analyzed.Based on the experimental result,three Lamb wave excitation methods are applied to detect the simulated defect in the plate.Experimental results show that in a certain frequency range,the method of exciting piezoelectric ceramic wafers in parallel symmetrically can suppress A0 mode effectively,and acquire single S0 mode relatively,and meanwhile the method of exciting piezoelectric ceramic wafers in parallel antisymmetrically can suppress S0 mode effectively and acquire single A0 mode relatively.The fewer the modes of Lamb waves excited are,the easier it is to identify the echoes from the defects.%为了激励Lamb波单一模态的S0和A0,采用2个相同的直径14 mm、厚0.8 mm的压电陶瓷片对称粘贴在2 mm厚的有机玻璃板上作激励传感器,在另一位置布置同一尺寸的压电陶瓷片作接收传感器.采用一发一收法,在低于100 kHz的频段内,激励传感器在板中分别单片、2片对称和反对称并联激励Lamb波,分析接收信号中模态成分的变化.并在此基础上,采用3种不同的激励Lamb波的方式对板中模拟缺陷进行了检测.实验结果表明,在一定频段内,对称并联激励压电陶瓷片可以有效抑制A0模态,得到较为单一的S0模态,而反对称并联激励压电陶瓷片能有效抑制S0模态,得到较为单一的A0模态;激励的Lamb波信号中模态越单一,缺陷回波越易识别.