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In this study, a new energy efficient welding method called flux bands constricting arc (FBCA) welding was presented. A real-time electrical signal acquisition system and a high-speed camera system were proposed to understand the arc stability in FBCA welding. In ultra-narrow gap groove, the arc voltage and welding current in gas metal arc welding and FBCA welding experiments with various groove gaps (4–10 mm) were acquired. The dynamic characteristics, probability distributions, scatter graphs, and coefficients of variations of voltage and current during welding were adopted to determine the arc stability. Results indicate that flux bands considerably improve the arc stability in the ultra-narrow gap (

A new energy-efficient welding method, flux bands constricting arc (FBCA) welding, is proposed to solve the fabrication of metal sandwich panels. This method is suitable for welding T-joints in special structures where the welding gun is unable to reach the welding position, such as welding thick face-plate metal sandwich panels. The characteristics of FBCA welding, key welding technologies, and corresponding defects and resolutions are discussed. Pull-out tests between T-joints welded by laser and FBCA welding were conducted. Results indicate that complete penetration and good fusion of three-sided T-joint can be produced by FBCA welding. The typical cross section morphology is unlike other common welding methods. T-joints without defects, such as weld asymmetry, root leakage, slag inclusion, and pores, show better ultimate tensile strength than T-joints welded by laser welding. The FBCA welding method can compensate for shortage of insufficient weld width of laser welding.

A new welding method, flux bands constricting arc (FBCA) welding, is proposed to compensate for the shortage of insufficient weld width of laser welding T-joints in high steel sandwich panels. The arc behavior (arc burning position, arc shape, arc heat, and arc stability) before and after sticking the flux bands (GMAW and FBCA welding) to the ultra-narrow gap groove was tested. Results indicate that flux bands have solid-wall constricting effect (SWCE) and thermo-compression effect (TCE) on the arc and self-producing slag and gas function in FBCA welding. In ultra-narrow gap groove, the arc burning position climbing up phenomenon (APCP) occurs without flux bands. The SWCE of flux bands on the arc effectively suppresses the APCP because of the insulation of flux bands. In the FBCA welding process, the effective heating area of the arc is increased by at least 5 mm2 compared with that in GMAW. When the groove gap decreases, flux bands not only compress the arc from an inverted bell shape to a rectangular shape, but also make the 660 &deg, C isotherm on the core-plate to increase from 3 mm to 8 mm. In the end, the proportion of unstable arc burning time is reduced by 86.85%, the fluctuation of arc voltage and welding current are also significantly reduced by the flux bands because of their SWCE on the arc.

For solving the problem of automated robot ultra-narrow gap welding, based on flux bands constricting arc ultra-narrow gap welding experiments, a robot ultra-narrow gap welding system and real-time arc signal acquisition system were established. The paper elaborates the effect of robot kinematic accuracy on the welding process, and through studying the arc signal in different groove types and with different welding wire position in the groove to put forward an arc characteristic that can be used for weld tracking in ultra-narrow gap welding. Results of this study indicate that robot kinematic accuracy should be controlled less than ±1mm in flux bands constricting arc ultra-narrow gap welding. The narrower the groove gap is, the higher the requirement of robot kinematic accuracy is. As the welding torch deviation distance from center of groove increase, the arcing voltage is significantly reduced, the voltage drop is also reduced, but the peak current and short-circuit transition frequency are significantly increased. The arc signal reflects the arc state and welding wire position in the groove. The difference in the arc signal when the welding torch is near to and away from the side-wall, which can be used to track the center of the groove.

This paper presents a detailed discussion of the bending properties of laser welded web-core steel sandwich plates and the influence of weld width on stiffness and strength. The over-hanging three point bending test was conducted on the laser welded web-core steel sandwich plates with various welds width by self-designed device, together with the finite element simulations. A good agreement is obtained between the 2D FE analyses and experiment results. The stiffness and strength of the sandwich plates increased with the increasing of weld width, especially for the weld width lower than 60% thickness of the core plate. It is necessary to consider the weld width in the design and evaluation of the stiffness and strength of the laser welded web-core sandwich plate. Base on the results, the FEM is the priority to analysis bending properties of laser welded web-core steel sandwich plates.

All steel laser welded sandwich plates have found their position in the marine and land vehicles. To implement such design accurately, knowledge about its strength properties and the influence of laser weld dimensions on strength is necessary. In this paper, the over-hanging three point bending tests were conducted on the laser welded web-core steel sandwich plate with various weld dimensions by self-designed device, together with the finite element simulations. The results show that the joint is formed on the first plastic hinge when the load is no longer a linear relationship with the deflection, and the joint cracking when the load reaches the maximum bearing capacity of sandwich plate. The joint yield load and the maximum bearing capacity of the sandwich plates increased with the increasing of weld width. Meanwhile, the mode of failure of sandwich plates also changed: When the weld width is smaller, the mode of failure is joint yield, When the weld width is greater than 3mm, the mode of failure is the combination of partial joint yield, face plate and core plate local yield, while the face plate and core plate yield exists in the whole weld joint. It is necessary to consider the weld width in the design and evaluation of the strength of the laser welded web-core sandwich plate.

This paper presents the influence of the weld widthroot gapand weld offset of the T-joint to the overall stiffness of sandwich plate with finite element simulations. From the results of finite element calculation and some of experimental verification we can see:(1) For this structure, welding joint damage occurs before the face plate buckling.(2) Among the factors weld widthgap and weld offset of the T-joint, the weld width affect the overall stiffness the most. (3) When root gap and weld offset lower 0.1mm and 0.12 mm, respectively, they have a little influence on the resistance of deformation ability for the sandwich plate, they can be ignore.

This paper uses the small punch test (SPT) to some performance of the materials, have put forward basic method to test the material tensile mechanics performance from an inverse FE method with SPT. The research shows that some tensile mechanics performance and stress of each district of welding seam can be accurate determined by small punch test. This research has offered the theoretical foundation for characterizing of the welded joint with mechanical heterogeneity