垂直载荷下湿玻璃珠样品的声速和衰减测量及非线性声学响应

为了分析垂直载荷下颗粒物质的声速、声衰减系数、谐波非线性等特性,本工作采用飞行时间法测量了不同含水量下声速随压强的变化规律,并利用傅里叶变换法分析了干、湿玻璃珠样品的声衰减和非线性声学特性。结果表明:干、湿玻璃珠样品中的声速、声衰减系数以及谐波非线性均随压强呈幂律变化;湿颗粒样品中随着液体含量增多,声速逐渐增加,超声波透过湿颗粒样品时的能量耗散和非线性逐渐减小。分析原因表明,压强和孔隙流体改变了颗粒之间的接触分布,使得颗粒体系的声速、声衰减以及谐波非线性等特性都随之发生变化。

Measurements of sound speed,attenuation and nonlinear acoustic response of wet glass bead samples under vertical loads

In this work, sound speeds with different pressures and different water contents are measured by using the time-of-flight method. Acoustic attenuation and nonlinear acoustic characteristics of dry and wet glass bead samples are analyzed with Fourier transform method. The results show that sound speed, acoustic attenuation coefficient and harmonic nonlinearity in the dry and wet glass bead samples vary with the pressure in the form of power law, and sound speed gradually increases with the increasement of liquid content in wet samples, and the energy dissipation and nonlinearity of ultrasonic waves through the wet samples gradually decrease. Pressure and pore fluid change the inter-particle contacts distribution, resulting in changes in elastic modulus, energy dissipation, as well as the number of internal weak contacts in the granular systems. The above results clarify the obvious effects of both pressure and pore fluid on the sound speed, attenuation and harmonic nonlinearity of wet granular systems.