Ballistic impact response of resistance-spot-welded (RSW) double-layered (2 $\times$ 1.6 mm) plates (190 mm × 150 mm) for Q&P980 steel impacted by a round-nosed steel bullet (12 mm diameter and 30 mm length) was investigated by using gas gun and high-speed camera system. The RSW specimens were spot welded using a 6 mm diameter electrode face producing a 7.2 mm diameter fusion zone of the spot weld. The ballistic curve and energy balance for the tests of the spot weld of the RSW specimens at different velocity were analyzed to characterize the ballistic behavior of the RSW specimens under bullet impact. The fracture mechanisms of the RSW specimens under bullet impact were presented. For the tests below the ballistic limit, the cracks initiated from the notch-tip and propagated along the faying surface or obliquely through the thickness depending on the impact velocity. For the tests above the ballistic limit, the plug fracture in the front plate of the RSW specimen could be caused by the thinning-induced necking in the BM near the HAZ, while the plug fracture in the rear plate of the RSW specimens may be consist of the circumferential cracking from the rear surface and the bending fracture of the hinged part of material. The effects of the electrode indentation and the weld interfaces on deformation and fracture of the RSW specimens under bullet impact were revealed. For the tests above the ballistic limit, the circumferential fracture from the rear surface of the RSW specimens was always initiated along the interior periphery of the electrode indentation and the crack paths were along the FZ/CGHAZ or CGHAZ/FGHAZ interface. When the circumferential crack also formed outside the electrode indentation, the fracture on the BM/HAZ interface could be found. On the front plate of the RSW specimens, the shear/bending induced cracking from the notch-tip were observed and the crack paths were along the FZ/CGHAZ or CGHAZ/FGHAZ interface.

电阻点焊（RSW）双层（2$\times$使用气枪和高速摄像机系统研究了用圆头钢弹（直径 12 毫米，长 30 毫米）撞击 Q&P980 钢的 1.6 毫米）板（190 毫米 × 150 毫米）。使用直径为 6 mm 的电极面对 RSW 样品进行点焊，从而产生直径为 7.2 mm 的点焊熔合区。分析了不同速度下 RSW 试件点焊试验的弹道曲线和能量平衡，以表征 RSW 试件在子弹冲击下的弹道行为。介绍了 RSW 试样在子弹冲击下的断裂机制。对于弹道极限以下的测试，裂纹从缺口尖端开始，并根据冲击速度沿接合面或斜向扩展厚度。对于弹道极限以上的测试，RSW 试件前板的塞子断裂可能是由于 HAZ 附近 BM 的变薄引起的颈缩引起的，而 RSW 试件后板的塞子断裂可能是由后表面的环向开裂引起的以及材料铰接部分的弯曲断裂。揭示了电极压痕和焊接界面对 RSW 试样在子弹冲击下变形和断裂的影响。对于弹道极限以上的测试，RSW 试样背面的圆周断裂总是沿着电极压痕的内周边开始，裂纹路径沿着 FZ/CGHAZ 或 CGHAZ/FGHAZ 界面。当电极压痕外也形成环向裂纹时，可以发现BM/HAZ界面上的断裂。