基于声发射技术的金属烧伤监测

Metal Burn Monitoring Based on Acoustic Emission

  • 摘要: 机床加工过程中冷却液无法及时带走磨削热量导致零部件表面产生金属烧伤,造成强度降低、残余应力增加等性能改变,产生巨大安全隐患。声发射(AE)技术具有对微弱信号敏感、可监测高频信号等优势而广泛应用于机床磨削烧伤监测。由于磨削过程中存在金属颗粒剥落、摩擦等强干扰信号,同时金属烧伤信号特征不明确,因此磨削烧伤监测精度不理想。为了提高烧伤信号识别准确率,有必要单独对金属烧伤声发射信号的特性进行研究。为获取纯净金属烧伤信号,设计并开展了激光实验模拟磨削烧伤过程。通过调整激光能量产生了四种程度的金属表面烧伤并获得相应的声发射信号。实验发现随着烧伤程度增加,声发射信号频谱产生向高频跃迁现象。根据这一现象,利用小波包变换(WPT)提取烧伤信号主导频带并进行特征提取。将提取出的特征向量输入主成分分析(PCA)算法,对不同程度金属烧伤信号进行聚类与识别。

     

    Abstract: In the process of grinding processing, grinding heat results in metal surface burn on parts, leading to reduced strength, increased residual stress, and other performance changes with significant security risks. Acoustic Emission (AE) technology is widely employed for monitoring grinding burn in machine tools due to its sensitivity to weak signals and ability to detect high-frequency signals. However, the accuracy of grinding burn monitoring is not ideal due to strong interference signals such as metal particle spalling and friction during the grinding process. Meanwhile, the characteristics of metal burn signal is unknown. To improve the accuracy of burn signal recognition, it is necessary to investigate the characteristics of metal burn AE signals independently. Therefore, a laser experiment was designed and conducted to simulate the grinding burn process in order to obtain pure metal burn signals. By adjusting laser energy levels, four degrees of surface metal burns were generated. It was observed that as the metal burn degree increased, the spectrum of AE signals moved to higher frequency bandwidth. Based on this phenomenon, Wavelet packet transform (WPT) was utilized to extract dominant frequency bandwidths of metal burn signals. The extracted feature vectors were then input into Principal Component Analysis (PCA) algorithm for clustering and identification metal burn signals.

     

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