In the past, brittle fracture of steel structure was reported rarely under earthquake. However, recent earthquakes, especially Northridge Earthquake (USA) and Hyogoken Nanbu earthquake (Japan), astonished engineers i...In the past, brittle fracture of steel structure was reported rarely under earthquake. However, recent earthquakes, especially Northridge Earthquake (USA) and Hyogoken Nanbu earthquake (Japan), astonished engineers in the field of construction. The experience from recent earthquakes of USA and Japan shows that brittle fracture of welded steel structure always starts from high stress zone with welded crack [1～5] . As backing bar for grooved weld on beam flange exists, artificial crack is formed because of lack of fusion at the root of flange weld. In this paper stress distribution of connection is computed with FEM, and stress concentration at the root of flange weld is also analyzed. Stress intensity factors (SIFs), K I, at the root of flange weld are computed in the method of fracture mechanics. The computation shows that stress intensity factor on bottom flange weld is obviously higher than that on top flange weld. It is proved by the fact that brittle fracture is liable to start at the root of bottom flange weld on actual earthquake [1,4] . Finally measures are brought forward to avoid fracture of weld structure against earthquake.展开更多
The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative stu...The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes.The effect of pulse parameters has been studied by considering their mean current and arc voltage.The arc characteristics studied by its root diameter,projected diameter and length,and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters.The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.展开更多
文摘In the past, brittle fracture of steel structure was reported rarely under earthquake. However, recent earthquakes, especially Northridge Earthquake (USA) and Hyogoken Nanbu earthquake (Japan), astonished engineers in the field of construction. The experience from recent earthquakes of USA and Japan shows that brittle fracture of welded steel structure always starts from high stress zone with welded crack [1～5] . As backing bar for grooved weld on beam flange exists, artificial crack is formed because of lack of fusion at the root of flange weld. In this paper stress distribution of connection is computed with FEM, and stress concentration at the root of flange weld is also analyzed. Stress intensity factors (SIFs), K I, at the root of flange weld are computed in the method of fracture mechanics. The computation shows that stress intensity factor on bottom flange weld is obviously higher than that on top flange weld. It is proved by the fact that brittle fracture is liable to start at the root of bottom flange weld on actual earthquake [1,4] . Finally measures are brought forward to avoid fracture of weld structure against earthquake.
文摘The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes.The effect of pulse parameters has been studied by considering their mean current and arc voltage.The arc characteristics studied by its root diameter,projected diameter and length,and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters.The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.
