AI 中文总结
本研究提出利用超声波热调制测定材料声学非线性参数的方法与理论框架，通过热应变激发材料非线性响应，经曲线拟合得到参数，经多材料样本验证精度良好，装置简单且应变场更均匀稳定。
AI 中文摘要
本研究提出了一种利用超声波热调制测定材料声学非线性参数（$α,β,δ$）的测试方法及其理论框架。温度变化引发的热应变激发材料的非线性响应，并对在其中传播的超声波进行调制。实验结果表明，相对波速变化与温度变化之间存在强相关性。研究采用二次多项式模型，通过对实验曲线进行曲线拟合，由多项式系数得到声学非线性参数，并讨论了这些参数对热致波速变化的影响。参数$α,β,δ$分别决定相关曲线的滞后间隙、平均斜率和曲率。该理论在铝、钢、完好及受损混凝土样本上得到了验证，所得非线性参数与文献报道的数值具有合理的一致性。与其他采用振动或声激励的非线性声学方法相比，热调制方法在测试样本中产生的应变场更均匀、变化更缓慢且应变值更大。该方法将热效应作为非线性的驱动力而非不良影响因素，仅需简单的超声测试装置，就能以良好的精度测量$α,β,δ$的绝对值。
英文摘要
This study presents a test method and its theoretical framework to determine the acoustic nonlinearity parameters ($α,β,δ$) of material using thermal modulation of ultrasonic waves. Temperature change induced thermal strain excites the nonlinear response of the material and modulates the ultrasonic wave propagating in it. Experimental results showed a strong correlation between the relative wave velocity change and the temperature change. With a quadratic polynomial model, the acoustic nonlinearity parameters were obtained from the polynomial coefficients by curve fitting the experimental curves. Their effects on thermal-induced velocity change were discussed. The parameters $α,β,δ$ govern the hysteretic gap, average slope, and curvature of the correlation curve, respectively. The proposed theory was validated on aluminum, steel, intact and damaged concrete samples. The obtained nonlinear parameters show reasonable agreements with values reported in the literature. Compared to other nonlinear acoustic methods using vibration or acoustic excitation, the thermal modulation method generates more uniform, slow changing, and larger strain field in the test sample. Employing thermal effect as the driving force for nonlinearity instead of an undesired influencing factor, this method can measure the absolute values of $α,β,δ$ with good accuracy using a simple ultrasonic test setup.
CommentsPublished in Applied Physics Letters 116, 241901 (2020), DOI: 10.1063/5.0014975
Journal refAppl. Phys. Lett. 116, 241901 (2020)
