Pei Ning, Bond Leonard J
Department of Aerospace Engineering and Center for Nondestructive Evaluation, Iowa State University, Ames, Iowa 50011, USA.
J Acoust Soc Am. 2016 Nov;140(5):3834. doi: 10.1121/1.4967756.
Modeling and experiments are used to investigate Lamb wave propagation in the direction perpendicular to an applied stress. Sensitivity, in terms of changes in velocity, for both symmetrical and anti-symmetrical modes was determined. Codes were developed based on analytical expressions for waves in loaded plates and they were used to give wave dispersion curves. The experimental system used a pair of compression wave transducers on variable angle wedges, with set separation, and variable frequency tone burst excitation, on an aluminum plate 0.16 cm thick with uniaxial applied loads. The loads, which were up to 600 με, were measured using strain gages. Model results and experimental data are in good agreement. It was found that the change in Lamb wave velocity, due to the acoustoelastic effect, for the S mode exhibits about ten times more sensitive, in terms of velocity change, than the traditional bulk wave measurements, and those performed using the fundamental Lamb modes. The data presented demonstrate the potential for the use of higher order Lamb modes for online industrial stress measurement in plate, and that the higher sensitivity seen offers potential for improved measurement systems.
通过建模和实验来研究兰姆波在垂直于外加应力方向上的传播。确定了对称模式和反对称模式在速度变化方面的灵敏度。基于加载板中波的解析表达式开发了代码，并用于给出波的色散曲线。实验系统在一块0.16厘米厚的铝板上使用了一对可变角度楔块上的压缩波换能器，换能器之间有固定间距，并采用可变频率的脉冲串激励，铝板上施加单轴载荷。使用应变片测量高达600με的载荷。模型结果与实验数据吻合良好。研究发现，由于声弹性效应，S模式的兰姆波速度变化在速度变化方面比传统的体波测量以及使用基本兰姆模式进行的测量灵敏度高约十倍。所呈现的数据表明了使用高阶兰姆模式进行板材在线工业应力测量的潜力，并且所观察到的更高灵敏度为改进测量系统提供了潜力。
