The quality of additive manufacturing (AM) components must be guaranteed to ensure wide applicability, and a nondestructive inspection technology is required in this regard. Therefore, this study examined a method for detecting subsurface defects using ultrasonic waves excited by a laser. Fundamental experiments showed that wideband ultrasonic waves can be excited with a suitable signal-to-noise ratio using high-repetition laser pulses. Images of subsurface defects were appropriately obtained using a scanning laser source (SLS) with broadband waves for an aluminum alloy flat plate with artificial defects. The imaging experiments showed that the acquisition condition depends on the local defect resonant (LDR) frequency in the defective part. The imaging technique also enabled to detect subsurface circular defects created by AM with the diameter below 1.0 mm that were undetectably small in our previous study using the SLS. Based on results of these experiments and a finite element analysis, the following guideline is proposed: the LDR frequencies of targeted defects must be included in the tested frequency range.

增材制造（AM）组件的质量必须得到保证，以确保广泛的适用性，这需要无损检测技术。因此，本研究研究了一种使用激光激发的超声波检测次表面缺陷的方法。基础实验表明，可以使用高重复激光脉冲以合适的信噪比激发宽带超声波。对于具有人工缺陷的铝合金平板，使用具有宽带波的扫描激光源 (SLS) 适当地获得了亚表面缺陷的图像。成像实验表明，采集条件取决于缺陷部分的局部缺陷共振 (LDR) 频率。成像技术还能够检测由 AM 产生的直径低于 1.0 毫米的地下圆形缺陷，这些缺陷在我们之前使用 SLS 的研究中无法检测到。根据这些实验的结果和有限元分析，提出以下指导原则：目标缺陷的 LDR 频率必须包括在测试频率范围内。