Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205, Berlin, Germany.
Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205, Berlin, Germany.
Ultrasonics. 2022 Feb;119:106612. doi: 10.1016/j.ultras.2021.106612. Epub 2021 Oct 22.
Air-coupled ultrasonic (ACU) testing has proven to be a valuable method for increasing the speed in non-destructive ultrasonic testing and the investigation of sensitive specimens. A major obstacle to implementing ACU methods is the significant signal power loss at the air-specimen and transducer-air interfaces. The loss between transducer and air can be eliminated by using recently developed fluidic transducers. These transducers use pressurized air and a natural flow instability to generate high sound power signals. Due to this self-excited flow instability, the individual pulses are dissimilar in length, amplitude, and phase. These amplitude and angle modulated pulses offer the great opportunity to further increase the signal-to-noise ratio with pulse compression methods. In practice, multi-input multi-output (MIMO) setups reduce the time required to scan the specimen surface, but demand high pulse discriminability. By applying envelope removal techniques to the individual pulses, the pulse discriminability is increased allowing only the remaining phase information to be targeted for analysis. Finally, semi-synthetic experiments are presented to verify the applicability of the envelope removal method and highlight the suitability of the fluidic transducer for MIMO setups.
空气耦合超声（ACU）测试已被证明是一种提高非破坏性超声测试速度和研究敏感样本的有效方法。在实施 ACU 方法时，一个主要障碍是在空气-样本和换能器-空气界面处存在显著的信号功率损耗。可以使用最近开发的射流换能器来消除换能器和空气之间的损耗。这些换能器使用加压空气和自然流动不稳定性来产生高声功率信号。由于这种自激流动不稳定性，单个脉冲在长度、幅度和相位上存在差异。这些幅度和角度调制脉冲为使用脉冲压缩方法进一步提高信噪比提供了很好的机会。在实践中，多输入多输出（MIMO）设置减少了扫描样本表面所需的时间，但需要高脉冲可分辨性。通过对单个脉冲应用包络去除技术，可以提高脉冲可分辨性，只允许针对剩余的相位信息进行分析。最后，提出了半合成实验来验证包络去除方法的适用性，并强调了射流换能器在 MIMO 设置中的适用性。
