利用红外热成像技术分析搅拌摩擦焊隧道型孔洞形成机制

Analysis of tunnel defect formation procedure by using infrared thermography

隧道型孔洞是搅拌摩擦焊焊接厚板的过程中最为典型且危害性最大的一种缺陷,并贯穿于整个焊缝。研究隧道型孔洞的形成机制,通过红外热成像仪拍摄摩擦焊接过程中无轴肩搅拌针温度实时变化情况,分析搅拌针附近金属的流动情况和隧道型孔洞形成位置,利用倒锥形搅拌针急停实验验证隧道型孔洞形成位置。根据红外热成像仪拍摄数据分析搅拌针前进侧后端温度最低,说明此处金属流动性最差,隧道型孔道易在此处形成,并结合急停实验对上述推论进行实验验证。同时实验发现在搅拌摩擦焊搅拌针旋转一周这个周期内,金属温度的传递可为三种形式:摩擦产热、流动传热与扩散传热。在前端半个周期内进行摩擦产热,在后端半个周期内进行温度的传递。

Tunnel defect is one of the most typical and harmful defects during welding plate,which runs through the whole process of welding.This paper is to analysis the tunnel defect formation procedure ,and the creative point is that the temperature field of the nonshoulder pin was obtained by using infrared video camera.The flow pattern around the pin and the tunnel defect formation procedure were analyzed.The experiment of rapid stopping during FSW using tapered pin proved it.The temperature field result showed that metal temperature is the lowest at the advancing side,so the tunnel defect tends to be formed in there.There were three types of temperature transmission：friction heat production,flow heat loss,diffusion heat loss.The friction heat was produced in the front half of period, and the heat transmission was in the another half of period.