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声发射源时差定位方法中波速的确定是定位准确的关键问题,根据模态声发射理论,声发射信号在薄板内的传播过程中具有频散现象和多模态特性.不同频率不同模态的声波其传播速度不同.基于Lamb波频散特性和声发射检测技术,采取时频联合分析方法对铝薄板中声波模式进行识别;利用低频段频散不明显的扩展波的波速和同一频率同一模态波到达两传感器的时间差来实现声发射源的准确定位;通过铝薄板中AE源定位实验表明,采用S0模式,即扩展波的波速进行定位计算,可以比较准确地确定声发射源的位置,而且理论值与实际值相差很小.
According to the theory of modal acoustic emission, the acoustic emission signal has the characteristics of frequency dispersion and multi-modal in the propagation of thin-plate, and the determination of the wave velocity in the method of acoustic emission source time-difference positioning is the key problem of accurate positioning. Based on the dispersion characteristics of Lamb wave and the acoustic emission detection technique, the acoustic wave modes in aluminum sheet are identified by the time-frequency joint analysis method. The wave velocity of the extended wave with the low frequency band dispersion is not obviously different from that of the same frequency The experimental results of AE source positioning in aluminum sheet show that using S0 mode, that is to say, the wave velocity of the extended wave can be used to locate and calculate the position of the acoustic emission source more accurately. And the theoretical value and the actual value of a small difference.