Acoustic emission monitoring for necking in sheet metal forming
Acoustic emission monitoring for necking in sheet metal forming
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DOI：
10.1016/j.jmatprotec.2022.117758
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发表时间：
2022
影响因子：
6.3
通讯作者：
M. Baral;Ali Al-Jewad;A. Breunig;P. Groche;J. Ha;Y. Korkolis;B. Kinsey
中科院分区：
文献类型：
--
作者：
M. Baral;Ali Al-Jewad;A. Breunig;P. Groche;J. Ha;Y. Korkolis;B. Kinsey
文献中有大量证据表明金属的塑性变形与声发射 (AE) 活动的增加有关。因此，AE 测量技术具有实时监控成形过程并提供反馈控制信号的潜力，以利用最佳的成形性。在这项工作中，采用压电晶体的定制 AE 传感器用于测量 AA6013-T4 铝板（1.5 毫米厚）的单轴拉伸和杯拉测试期间发出的声信号。单轴拉伸测试是通过将两个 AE 传感器夹在样本量具部分的两端进行的，并使用数字图像相关 (DIC) 技术进行全场表面应变测量。 AE 信号以及 DIC 图像的询问表明，最大 AE 振幅对应于扩散颈缩的开始，即当应变场开始变得空间不均匀时。有趣的是，这种现象发生在达到最大力之前。将这些观察结果与位错活动模型进行比较，支持了位错是 AE 活动的主要驱动因素的观点。根据这些发现，在拉深过程中进行 AE 测量，其中定制的 Marciniak 型冲头包含三个 AE 传感器。这些传感器用于根据到达每个传感器的信号的时间差进行三角测量并确定颈缩和突出断裂的位置。拉深试验结果表明，声发射信号可以识别颈缩的开始并准确预测颈缩和断裂的位置。
There is extensive evidence in the literature that plastic deformation of metals is associated with an increase in Acoustic Emission (AE) activity. Thus, AE measurement techniques have the potential to monitor a forming process in real time and provide a signal for feedback control, to exploit optimum formability. In this work, custom-made AE sensors employing piezoelectric crystals are implemented to measure the emitted acoustic signal during uniaxial tension and cup drawing tests of an AA6013-T4 aluminum sheet (1.5 mm thick). The uniaxial tension tests are conducted with two AE sensors clamped to each end of the specimen gage section, along with full-field surface strain measurement using Digital Image Correlation (DIC) techniques. The AE signals along with the interrogation of the DIC images reveal that the maximum AE amplitude corresponds to the onset of diffuse necking, i.e., when the strain field starts to become spatially inhomogeneous. Interestingly, this onset occurs before the maximum force is attained. Comparing these observations to a model of dislocation activity supports the notion that dislocation is the main driver of AE activity. With these findings, AE measurements are performed in a cup drawing process where a custom-made Marciniak-type punch incorporates three AE sensors. These sensors are used to triangulate and determine the location of necking and eminent fracture based on the time difference of arriving signals to each sensor. The results from the cup drawing tests show that AE signals can identify the onset of necking and accurately predict the location of necking and fracture.