A bypass-current metal inert-gas welding-brazing technology has been developed to join aluminum/galvanized steel and aluminum/stainless steel. Microstructure, intermetallic compounds and hardness distribution of the joints were studied by optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis and microhardness tests. Comparative study on both types of joints was carried out. During aluminum to galvanized steel assembling, finer seam was obtained under a more stable process. A uniform interfacial reaction layer with a thickness of 2-4 μm was formed. During aluminum to stainless steel assembling, an uneven interfacial reaction layer with a thickness of 5-45μm was formed. Intermetallic compounds at the interface of aluminum/galvanized steel were identified as Fe-Al- Si-Zn complex phases, while Fe-Al-Cr-Ni complex phases were found at the aluminum/stainless steel interface. Microhardness of interfacial layer increases rapidly within reaction layer due to possible brittle intermetallic compounds.
Sheets of aluminum 6061 alloy were welded using bypass-current double-sided arc welding with Al-Si filler wire to investigate the effect of Al-Si intermetallic compounds on the microstructure, microhardness and corrosion behavior of weld joint. Experimental results indicated that the Al4.5FeSi phase in the topside of the weld joint was finer than that in the backside and newly formed phase of Al0.5Fe3Si0.5 was observed in the backside. The formation of reinforcing phases of Al-Fe-Si in the weld improved the microhardness of the weld by about 18%. The corrosion resistance of the weld zone was greater than that of the base metal, while the corrosion current displayed opposite, and the corrosion resistance of the weld region was better than that of the base metal.
Yu-Gang MiaoBen-Shun ZhangBin-Tao WuXiao-Xiao WangGuang-Yu ChenDuan-Feng Han
应用立体视觉三维测量系统对钢结构上若干待测标志点进行测量,测量前分两步对测量系统参数进行标定.首先应用基于平面模板的方法标定摄像机的固有参数,包括单个摄像机的内部参数和两个摄像机间的位置关系参数.其次使用单位四元数法对摄像机坐标系与设计坐标系之间的位置参数进行标定.为了验证标定结果的准确性,对摄像机内参数标定结果进行了重投影误差估算,重投影误差很小,满足系统测量误差要求.对标定结果进行重建试验,重建结果平均误差小于1 mm,最大误差小于2.5 mm.
应用立体视觉三维测量系统对钢结构上若干待测标志点进行测量,测量前分两步对测量系统参数进行标定.首先应用基于平面模板的方法标定摄像机的固有参数,包括单个摄像机的内部参数和两个摄像机间的位置关系参数.其次使用单位四元数法对摄像机坐标系与设计坐标系之间的位置参数进行标定.为了验证标定结果的准确性,对摄像机内参数标定结果进行了重投影误差估算,重投影误差很小,满足系统测量误差要求.对标定结果进行重建试验,重建结果平均误差小于1 mm,最大误差小于2.5 mm.
