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郭妍钰,张昌锁,张 玥. 高频导波检测锚固锚杆缺陷数值模拟研究[J]. 煤炭科学技术,2023,51(10):35−44

. DOI: 10.13199/j.cnki.cst.2022-1387
引用本文:

郭妍钰,张昌锁,张 玥. 高频导波检测锚固锚杆缺陷数值模拟研究[J]. 煤炭科学技术,2023,51(10):35−44

. DOI: 10.13199/j.cnki.cst.2022-1387

GUO Yanyu,ZHANG Changsuo,ZHANG Yue. Numerical simulation of high frequency guided wave testing for anchor bolt defects[J]. Coal Science and Technology,2023,51(10):35−44

. DOI: 10.13199/j.cnki.cst.2022-1387
Citation:

GUO Yanyu,ZHANG Changsuo,ZHANG Yue. Numerical simulation of high frequency guided wave testing for anchor bolt defects[J]. Coal Science and Technology,2023,51(10):35−44

. DOI: 10.13199/j.cnki.cst.2022-1387

高频导波检测锚固锚杆缺陷数值模拟研究

Numerical simulation of high frequency guided wave testing for anchor bolt defects

  • 摘要: 前期研究证实对于地下工程中广泛使用的锚固锚杆结构只有大于1 MHz的高频导波具有衰减最小的检测模态,但由于高频导波数值模拟复杂性其研究结果均集中于试验测试,这就使得对高频导波传播特性的研究十分受限。为探究高频导波传播规律并能将其应用于现场锚固质量的检测,采用ANSYS/LS–DYNA有限元软件通过参数优化实现了锚固锚杆数值模型的建立。通过分析不同锚固体厚度对波形的影响得到了能用数值模拟有限尺寸模型代替现场无限锚固厚度尺寸模型的最小外径;理论上导波主要沿钢杆内部向前传播,且锚杆径向体现波导结构形状,因此采用锚杆径向网格设置最密,锚固体径向与杆体轴向网格设置相对稀疏的方法实现了单元数目最小化;鉴于不同首波宽度的导波频散特性不同,对其在无缺陷及带缺陷锚杆中的传播过程进行研究,得到最优首波宽度为0.04 ms;基于上述优化后的3个参数分别建立完整锚固锚杆与带缺陷锚固锚杆数值模型,数值计算结果与文献中实验室测试结果高度吻合,证明所建立数值模型正确有效,真正实现了有限计算资源下高频导波在锚固锚杆传播应用中的准确模拟。在此基础上搭建含不同缺陷特征的锚固锚杆模型,对缺陷位置及深度进行研究,结果表明特定频率的高频导波能够对钢杆缺陷进行准确定位,同时依据缺陷回波幅值与底端回波幅值之比可大致确定缺陷面积。

     

    Abstract: Previous research has confirmed that only high-frequency guided waves larger than 1 MHz have the minimum attenuation detection mode for anchor bolt widely used in underground projects. However, due to the complexity of numerical simulation of high-frequency guided waves, the research results are concentrated on experimental testing, which makes the research on propagation characteristics of high-frequency guided waves very limited. In order to explore the propagation of high-frequency guided wave and apply it to the on-site inspection of anchorage quality, the numerical model of anchor bolt is established by using ANSYS/LS–DYNA finite element software through parameter optimization. By analyzing the influence of different anchor thickness on the wave shape, the minimum outer diameter that can replace the field infinite anchor thickness model with the numerical simulation finite size model is obtained; In theory, the guided wave mainly propagates forward along the interior of the steel rod, and the bolt radial reflects the waveguide structure shape. Therefore, the bolt radial grid is set the densest, and the anchor body radial grid and the bar axial grid are set relatively sparse, in order to minimize the number of elements; In view of the different dispersion characteristics of guided waves with different head wave widths, the propagation process of guided waves in non-defective and defective bolts was studied, and the optimal head wave width was 0.04 ms; Based on the above three optimized parameters, the numerical models of the complete anchor bolt and the anchor bolt with defects are established respectively. The numerical simulation results are highly consistent with the laboratory test results in the literature, which proves that the numerical model established is correct and effective, and truly realizes the accurate simulation of high-frequency guided waves in the propagation application of the anchor bolt under the limited computing resources. On this basis, the anchor bolt model with different defect characteristics is built, and the defect location and depth are studied. The results show that the high frequency guided wave with specific frequency can accurately locate the steel rod defects, and the defect area can be roughly determined according to the ratio of defect echo amplitude to bottom echo amplitude.

     

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