Abstract: Acoustic emission technique has many advantages because it is noninvasive and relatively inexpensive.A set of apparatus was built to measure the velocity of different-sized glass beads impacting upon a steel plate and the arising acoustic emission signal by use of a broadband piezoelectric transducer simultaneously.The impact velocity was measured by optical cross correlation velocimetry.The Welch method was used to analyze the characteristics of power spectrum of acoustic emission signal.Power spectrum mainly focused on the frequency band of 50—400 kHz and its peak moved to the lower frequency band as the particle size of glass beads was larger.Based on the Hertz-Zener theory and analytical approximation of acoustic emission spectrum, a least squares method was used in the frequency domain with the goal of calculating particle size from the experimental data.The results of the glass beads with diameters over the range of 300—400 μm and 400—600 μm agreed well with the respective results of sizing by CAMSIZER.It also provided a new way to measure particle size distribution.

Key words: acoustic emission, Hertz-Zener theory, particle size distribution, Welch method, cross-correlation velocimetry

摘要： 搭建了一套可同时测量碰撞速度和声发射信号的装置,利用宽带声发射传感器高速采集5种不同粒径玻璃微珠碰撞钢板的声发射信号,经Welch算法计算功率谱发现声发射信号均主要集中在50～400 kHz频段,且随着粒径增大,频谱分布往低频区域迁移;基于Hertz-Zener理论并引入频谱估算近似式,利用光学互相关法测量碰撞速度,将理论估算频谱和实测信号功率谱作归一化处理后,采用最小二乘法估算出玻璃微珠的粒径,3^#(300～400 μm)和4^#(400～600 μm)玻璃微珠的粒径估算结果和CAMSIZER仪器测得值吻合较好,并分析了导致其他粒径估算产生偏差的原因。实验证实了该方法的可行性和有效性,同时为实现颗粒粒径分布测量提供了新思路。

关键词: 声发射, Hertz-Zener理论, 粒径分布, Welch算法, 互相关测速