ABSTRACT Nondestructive testing for internal defects is necessary owing to the extensive application of metal balls in different industrial fields. The flat-bottom holes (FBHs) are used as the reference standards for the detection of internal defects. An ultrasonic measurement model with spherical-focused transducer based on multi-Gaussian beam is proposed to describe the detection of FBHs inside the metal ball. The comparison between the predicted signals and the pulse-echo responses of FBHs is given to certify the accuracy of the model. The distance-amplitude-correction (DAC) curves are provided to evaluate the equivalent size and depth magnitude of the defects inside the balls. The experimental results indicate that the model can predict and evaluate the internal defects accurately and efficiently. Finally, the method of spiral fully unfolding of ball surface based on orthogonal clamping is developed and successfully applied to the automatic ultrasonic testing system for internal defects of bearing balls combining with the model-based DAC curves.

中文翻译：

---

金属球内部缺陷无损检测方法及应用

摘要 由于金属球在不同工业领域的广泛应用，对内部缺陷进行无损检测是必要的。平底孔 (FBH) 用作检测内部缺陷的参考标准。提出了一种基于多高斯光束的球面聚焦换能器超声测量模型来描述金属球内部FBHs的检测。将预测信号与 FBH 的脉冲回波响应进行比较，以证明模型的准确性。提供距离幅度校正 (DAC) 曲线以评估球内部缺陷的等效尺寸和深度幅度。实验结果表明，该模型能够准确、高效地预测和评估内部缺陷。最后，