Hongming GAO
,
Lin WU
,
Honggang DONG
材料科学技术（英文）
Up till now, most of the researchers believe that there are four kinds of forces in the weld pool convection, they are surface tension, electromagnetic force, buoyancy and gas shear stress. So electromagnetic force is very important, especially when large current is applied. In most of previous models, the electromagnetic force is calculated analytically, in which only the axial component of current is considered. Actually the radial component of current has the same effect, and may be advanced in some locations. In double-sided arc welding process, instead of the earth clamp, another torch is placed on the opposite side, the current will go from one torch, through the weld zone, to another torch. In this case, the current is more concentrated in the weld zone, the electromagnetic force will have significant effect compared with conventional welding process. In this paper, a new method of numerical calculation for electromagnetic force is developed, in which both axial and radial components are considered. And as an example, the distribution of electromagnetic force in double-sided arc welding is calculated. It demonstrates that this new method could give more accurate simulation of electromagnetic force, and is close to the actual process.
关键词:
Electromagnetic force
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Hongming GAO
,
Lin WU
,
Honggang DONG
材料科学技术（英文）
A three dimensional current density distribution in double-sided gas tungsten are welding (GTAW) proces is performed. The current density distribution field is evaluated by numerically solving Maxwell equations in the domain of the workpiece. In the boundary condition, the current density on the workpiece surface is assumed as Gaussian distribution. Results show that the current distribution in DSAW is different from single side are welding, it is more concentrated and the relative location of the two torches influence the current distribution greatly.
关键词:
Physical Review B
In a recent publication [S. Dong et al., Phys. Rev. Lett. 103, 127201 (2009)], two (related) mechanisms were proposed to understand the intrinsic exchange bias present in oxides heterostructures involving G-type antiferromagnetic perovskites. The first mechanism is driven by the Dzyaloshinskii-Moriya interaction, which is a spin-orbit coupling effect. The second is induced by the ferroelectric polarization, and it is only active in heterostructures involving multiferroics. Using the SrRuO(3)/SrMnO(3) superlattice as a model system, density-functional calculations are here performed to verify the two proposals. This proof-of-principle calculation provides convincing evidence that qualitatively supports both proposals.
关键词:
thin-films;weak ferromagnetism;superlattices;anisotropy;bifeo3;srruo3;model
