Winklberger Markus, Kralovec Christoph, Humer Christoph, Heftberger Peter, Schagerl Martin
Institute of Structural Lightweight Design, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria.
Ro-Ra Aviation Systems GmbH, Gewerbepark 8, 4861 Schörfling am Attersee, Austria.
Sensors (Basel). 2020 Dec 23;21(1):44. doi: 10.3390/s21010044.
This contribution investigates fatigue crack detection, localization and quantification in idealized necked double shear lugs using piezoelectric transducers attached to the lug shaft and analyzed by the electro-mechanical impedance (EMI) method. The considered idealized necked lug sample has a simplified geometry and does not includes the typical bearing. Numerical simulations with coupled-field finite element (FE) models are used to study the frequency response behavior of necked lugs. These numerical analyses include both pristine and cracked lug models. Through-cracks are located at 90∘ and 145∘ to the lug axis, which are critical spots for damage initiation. The results of FE simulations with a crack location at 90∘ are validated with experiments using an impedance analyzer and a scanning laser Doppler vibrometer. For both experiments, the lug specimen is excited and measured using a piezoelectric active wafer sensor in a frequency range of 1kHz-100kHz. The dynamic response of both numerical calculations and experimental measurements show good agreement. To identify (i.e., detect, locate, and quantify) cracks in necked lugs a two-step analysis is performed. In the first step, a crack is detected data-based by calculating damage metrics between pristine and damaged state frequency spectra and comparing the resulting values to a pre-defined threshold. In the second step the location and size of the detected crack is identified by evaluation of specific resonance frequency shifts of the necked lug. Both the search for frequencies sensitive to through-cracks that allow a distinction between the two critical locations and the evaluation of the crack size are model-based. This two-step analysis based on the EMI method is demonstrated experimentally at the considered idealized necked lug, and thus, represents a promising way to reliably detect, locate and quantify fatigue cracks at critical locations of real necked double shear lugs.
本论文研究了在理想化的颈缩双剪切耳片中，使用附着在耳轴上的压电传感器并通过机电阻抗（EMI）方法进行分析，以实现疲劳裂纹的检测、定位和量化。所考虑的理想化颈缩耳片样本具有简化的几何形状，不包括典型的轴承。使用耦合场有限元（FE）模型进行数值模拟，以研究颈缩耳片的频率响应特性。这些数值分析包括原始耳片模型和有裂纹的耳片模型。贯穿裂纹位于与耳轴成90°和145°的位置，这些是损伤起始的关键位置。通过使用阻抗分析仪和扫描激光多普勒测振仪进行实验，验证了裂纹位置为90°时的有限元模拟结果。对于这两个实验，耳片试样在1kHz - 100kHz的频率范围内使用压电有源晶片传感器进行激励和测量。数值计算和实验测量的动态响应显示出良好的一致性。为了识别（即检测、定位和量化）颈缩耳片中的裂纹，进行了两步分析。第一步，通过计算原始状态和损伤状态频谱之间的损伤指标，并将所得值与预定义阈值进行比较，基于数据检测裂纹。第二步，通过评估颈缩耳片的特定共振频率偏移来识别检测到的裂纹的位置和尺寸。寻找对贯穿裂纹敏感的频率以区分两个关键位置以及评估裂纹尺寸均基于模型。基于EMI方法的这两步分析在考虑的理想化颈缩耳片上进行了实验验证，因此，是一种在实际颈缩双剪切耳片关键位置可靠检测、定位和量化疲劳裂纹的有前途的方法。
