Tang Yan, Mao Hanying, He Chunhua, Mao Hanling, Bi Yiwen, Huang Zhengfeng, Li Xinxin, Lin Yongchuan
School of Mechanical Engineering, Guangxi University, Nanning 530004, China; Light Alloy Research Institute, Central South University, Changsha 410000, China.
School of Mechanical and Transportation Engineering, Guangxi University of Science and Technology, Liuzhou 545006, China.
Ultrasonics. 2024 Mar;138:107240. doi: 10.1016/j.ultras.2024.107240. Epub 2024 Jan 6.
Ultrasonic techniques have been widely used to detect the percentage of vermicular graphite, defects, etc. in vermicular graphite cast iron. The linear ultrasonic velocity method is the main ultrasonic method for characterizing vermicular graphite rate and tensile strength in the current study, however, it is often easy to misjudge the vermicular graphite rate due to its insignificant variation. This study explores the feasibility of using the nonlinear ultrasonic technique (NUT) to characterize the vermicular graphite rate and tensile strength. Based on the longitudinal critically refracted (LCR) wave detection model, an experimental study to detect the vermicular graphite rate and tensile strength of vermicular graphite cast iron is carried out using the nonlinear ultrasonic harmonic method, and compared with the ultrasonic velocity method. The experiment results show that the relative nonlinear parameter of the LCR wave decreases along with the increase of vermicular graphite rate and increases along with the increase of tensile strength, and it has higher detection sensitivity and resolution than ultrasonic velocity by analyzing the obtained data. The increase in the acoustic nonlinearity parameter (ANP) is related to the increase in the number of grain boundaries in the microstructure. Therefore, the relationship among microstructure, ANP, and mechanical properties of vermicular graphite cast iron can be established, and it's promising that a new approach might be developed for quickly detecting the vermicular graphite rate and corresponding tensile strength with the NUT.
超声技术已被广泛应用于检测蠕墨铸铁中的蠕虫状石墨百分比、缺陷等。线性超声速度法是当前研究中表征蠕虫状石墨率和抗拉强度的主要超声方法，然而，由于其变化不明显，往往容易误判蠕虫状石墨率。本研究探讨了使用非线性超声技术（NUT）表征蠕虫状石墨率和抗拉强度的可行性。基于纵向临界折射（LCR）波检测模型，采用非线性超声谐波法对蠕墨铸铁的蠕虫状石墨率和抗拉强度进行了检测实验研究，并与超声速度法进行了比较。实验结果表明，LCR波的相对非线性参数随蠕虫状石墨率的增加而减小，随抗拉强度的增加而增大，通过对所得数据的分析，其检测灵敏度和分辨率高于超声速度。声非线性参数（ANP）的增加与微观结构中晶界数量的增加有关。因此，可以建立蠕墨铸铁微观结构、ANP和力学性能之间的关系，有望开发出一种利用NUT快速检测蠕虫状石墨率和相应抗拉强度的新方法。
