The ultrasonic nonlinearity parameter $\beta$ defined by the ratio of the second-order harmonic amplitude to the square of fundamental frequency amplitude, has been considered as a potential index to evaluate material degradation. However, the yield strength obtained from destructive tensile testing is still widely adopted for this purpose since it is a more intuitive concept to the field engineer than the parameter $\beta$. Therefore, this study proposes a nondestructive method to evaluate the yield strength directly from the ultrasonic measurements. In this regard, the tensile stress–strain curve is represented in the form of a quadratic nonlinear stress–strain equation within the elastic range, which includes the linear elastic modulus and the second-order nonlinearity parameter ${\beta }_t$. The linear elastic modulus is obtained by measuring the propagation velocity of longitudinal and transverse waves using a traditional ultrasonic pulse-echo method, and the second-order nonlinearity parameter is obtained by measuring the Murnaghan constants using acoustoelastic effects. Then, the tensile stress–strain curve is reconstructed to estimate the 0.01% offset yield strength. To demonstrate the application of the proposed algorithm, the experiments were performed for heat-treated SA508 specimens. The results indicate that the 0.01% offset yield strength obtained using the proposed algorithm exhibit a good agreement with that obtained via destructive tensile testing.

超声非线性参数 $\beta$由二阶谐波幅度与基频幅度的平方之比定义的定义被认为是评估材料退化的潜在指标。但是，从破坏性拉伸试验获得的屈服强度仍被广泛用于此目的，因为对于现场工程师而言，它比参数更直观$\beta$。因此，这项研究提出了一种非破坏性方法，可以直接从超声测量中评估屈服强度。在这方面，拉伸应力-应变曲线以弹性范围内的二次非线性应力-应变方程形式表示，其中包括线性弹性模量和二阶非线性参数${\beta }_{Ť}$。线性弹性模量是通过使用传统的超声脉冲回波方法测量纵向和横向波的传播速度而获得的，而二阶非线性参数是通过使用声弹性效应来测量Murnaghan常数而获得的。然后，重建拉伸应力-应变曲线，以估计0.01％的偏移屈服强度。为了证明所提出算法的应用，对热处理过的SA508标本进行了实验。结果表明，使用所提出的算法获得的0.01％偏移屈服强度与通过破坏性拉伸测试获得的偏移具有很好的一致性。