To avoid complicated material constants calculation of conventional analysis approaches, in this paper, a work is conducted on evaluation the feasibility of ultrasonic characteristic parameters in in-situ wireless monitoring of fatigue crack propagation process in a structure. An aluminum central cracked specimen was fabricated to simulate a damaged thin plate structure. A fatigue crack growth test was conducted on the specimen under uniaxial cyclic tensile load with a constant amplitude, and the crack was vision-based regularly detected. Simultaneously, the crack propagation was monitored in real time by a self-developed wireless ultrasonic sensing device. Based on a crack growth behavior analysis, a relationship is established between crack length and loading cycles. Meanwhile, the evolvement of ultrasonic signals with the crack growing is investigated, and a relationship was established between the crack length and the ultrasonic characteristic parameter. Ultimately, a connection is established between the loading cycles and the ultrasonic characteristic parameter, which contains the length information of the cracks. The proposed model shows a good agreement with experimental data with correlation coefficients all higher than 0.96, which indicates the proposed method has a great potential in evaluating fatigue cracks in thin plate structures.

中文翻译：

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使用无线超声传感装置的薄板结构疲劳裂纹扩展评估

为避免传统分析方法复杂的材料常数计算，本文开展了超声特征参数在结构疲劳裂纹扩展过程现场无线监测中的可行性评估工作。制作了一个铝中央开裂试样来模拟损坏的薄板结构。对试样在等幅单轴循环拉伸载荷下进行疲劳裂纹扩展试验，并通过视觉定期检测裂纹。同时，通过自主研发的无线超声波传感装置对裂纹扩展进行实时监测。基于裂纹扩展行为分析，建立了裂纹长度和加载周期之间的关系。同时，研究了超声信号随裂纹扩展的演变规律，建立了裂纹长度与超声特征参数之间的关系。最终，加载循环与包含裂纹长度信息的超声特征参数之间建立了联系。该模型与实验数据吻合良好，相关系数均高于0.96，表明该方法在评估薄板结构疲劳裂纹方面具有巨大潜力。