The present study focuses on estimating material nonlinearity and consequently remaining useful life of fatigued specimens using the amplitude‐ and physics‐based material nonlinearity parameters evaluated for Lamb wave motion in plate specimens. The amplitude‐based nonlinearity parameter depends on amplitudes of the Lamb wave harmonics generated due to material nonlinearity. Here, it is employed to estimate the inherent and dislocation induced material nonlinearities for different stages of fatigue. The cumulative effect is obtained from the strict matching of phase and group velocities of the S₁ − S₂ mode pair. The physics‐based nonlinearity parameter is obtained from the higher order elastic coefficients, plastic coefficients, and substructural evolution parameters. It does not depend on wave propagation distance; however, it depends on percent fatigue life. Thus, it is used to construct a theoretical nonlinearity curve. A spectral amplitude normalization technique is given to systematically evaluate the material nonlinearity, once the Lamb wave data over different wave propagation distances are known either from experiments or from simulations. The values of amplitude‐based nonlinearity parameter thus estimated through the simulation and experiments for different fatigue stages are then plotted onto the obtained theoretical nonlinearity curve. A reasonably good agreement is seen between the fatigue life estimations given by both the nonlinearity parameters. Thus, the amplitude‐based nonlinearity parameter obtained from the Lamb wave response can be effectively used to estimate the remaining useful life of the fatigued plate specimens.

中文翻译：

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使用基于Lamb波的非线性参数估算疲劳板的剩余使用寿命

本研究着重于评估材料的非线性，从而使用针对板材样本中的兰姆波运动评估的基于振幅和物理的材料非线性参数来估计疲劳样本的剩余使用寿命。基于振幅的非线性参数取决于由于材料非线性而产生的兰姆波谐波的振幅。在这里，它被用来估计固有和位错引起的材料疲劳的不同阶段的非线性。累积效应是通过严格匹配S ₁  -  S ₂的相速度和群速度而获得的模式对。基于物理的非线性参数是从高阶弹性系数，塑性系数和子结构演化参数获得的。它不取决于波的传播距离。但是，这取决于疲劳寿命百分比。因此，它可用于构建理论非线性曲线。一旦从实验或模拟中获知了不同波传播距离上的兰姆波数据，就可以使用光谱幅度归一化技术来系统地评估材料的非线性。这样，通过仿真和不同疲劳阶段的实验估算出的基于振幅的非线性参数值将被绘制到获得的理论非线性曲线上。在两个非线性参数给出的疲劳寿命估计之间，可以看到一个相当好的协议。因此，从兰姆波响应获得的基于幅度的非线性参数可以有效地用于估计疲劳板样品的剩余使用寿命。