Laboratoire d'Imagerie Paramétrique, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7623, Université Pierre et Marie Curie, Paris, France.
J Acoust Soc Am. 2011 Dec;130(6):3583-9. doi: 10.1121/1.3652871.
Dynamic acoustoelastic testing provides a more complete insight into the acoustic nonlinearity exhibited by micro-inhomogeneous media like granular and cracked materials. This method consists of measuring time of flight and energy modulations of pulsed ultrasonic waves induced by a low-frequency standing wave. Here pulsed ultrasonic head waves were employed to assess elastic and dissipative nonlinearities in a region near the surface of a solid. Synchronization of the ultrasound pulse sequence with the low-frequency excitation provided instantaneous variations in the elastic modulus and the attenuation as functions of the instantaneous low-frequency strain. Weak quadratic elastic nonlinearity and no dissipative nonlinearity were detected in duralumin. In limestone, distinction between tensile and compressive behaviors revealed an asymmetry in the acoustic nonlinearity and hysteresis in both the elastic modulus and the attenuation variations. Measured nonlinear acoustical parameters are in good agreement with values obtained by different techniques. Reversible acoustically induced conditioning modified the acoustic nonlinearity both quantitatively and qualitatively. It reduced tension-compression asymmetry, suggesting a nonequilibrium modification of the sources of acoustic nonlinearity. Additionally to the metrology of the acoustic nonlinearity, head wave based dynamic acoustoelastic testing may be a useful tool to monitor changes in the microstructure or the accumulation of damage in solids.
动态声弹性测试为研究颗粒状和裂纹状等微不均匀介质表现出的声非线性特性提供了更全面的认识。该方法通过测量由低频驻波引起的脉冲超声波的飞行时间和能量调制来实现。在该方法中，我们采用脉冲超声波首波来评估固体表面附近区域的弹性和耗散非线性。通过将超声波脉冲序列与低频激励同步，可以获得作为瞬时低频应变函数的弹性模量和衰减的瞬时变化。在硬铝中检测到了较弱的二次弹性非线性和无耗散非线性。在石灰石中，拉伸和压缩行为的区分揭示了声非线性的不对称性以及弹性模量和衰减变化的滞后。测量得到的非线性声学参数与通过不同技术获得的值吻合良好。可恢复的声致调制在定量和定性两方面都改变了声非线性。它降低了拉伸-压缩的不对称性，表明声非线性源的非平衡调制。除了对声非线性的计量外，基于首波的动态声弹性测试也可能是监测固体中微观结构变化或损伤累积的有用工具。
