Mechanism Analysis of Magnetic Control High-Speed Welding Undercuts Disappear

2013 ◽  
Vol 774-776 ◽  
pp. 1127-1131 ◽  
Author(s):  
Lin Lu ◽  
Yun Long Chang ◽  
Ying Min Li ◽  
Feng Gao
Keyword(s):  
Magnetic Field ◽  
Liquid Metal ◽  
Molten Pool ◽  
High Speed ◽  
Flow Direction ◽  
Internal Flow ◽  
Effective Diameter ◽  
Magnetic Control ◽  
Mechanism Analysis ◽  
Welding Arc

Direction of flow of the liquid metal in the weld pool have important implications for weld. The liquid metal to weld edges near the point of internal flow in molten pool and the undercut could emerge when the liquid metal was freezing, by contrast, is not prone to undercut. The external magnetic fields could change the distance of surface tension of liquid metal, which may lead to the change of flow direction of molten pool. Article compares the different magnetic field under the condition of weld cross section of the timing of the welding arc. Results show that magnetic arc anode spots, TIG welding arc anode spot diameter greater than when there is no magnetic field effectively effective diameter, which will help reduce the undercut.

Liquid-metal flow in a system of electrically coupled U-bends in a strong uniform magnetic field

1995 ◽  
Vol 299 ◽  
pp. 73-95 ◽  
Author(s):  
Sergei Molokov ◽  
Robert Stieglitz
Keyword(s):  
Magnetic Field ◽  
Pressure Drop ◽  
Liquid Metal ◽  
Uniform Magnetic Field ◽  
Flow Direction ◽  
Metal Flow ◽  
Three Dimensional ◽  
Recirculatory Flow ◽  
The Magnetic Field ◽  
Very High

Liquid-metal magnetohydrodynamic flow in a system of electrically coupled U-bends in a strong uniform magnetic field is studied. The ducts composing the bends are electrically conducting and have rectangular cross-sections. It has been anticipated that very strong global electric currents are induced in the system, which modify the flow pattern and produce a very high pressure drop compared to the flow in a single U-bend. A detailed asymptotic analysis of flow for high values of the Harmann number (in fusion blanket applications of the order of 103−104) shows that circulation of global currents results in several types of peculiar flow patterns. In ducts parallel to the magnetic field a combination of helical and recirculatory flow types may be present and vary from one bend to another. The magnitude of the recirculatory motion may become very high depending on the flow-rate distribution between the bends in the system. The recirculatory flow may account for about 50% of the flow in all bends. In addition there are equal and opposite jets at the walls parallel to the magnetic field, which are common to any two bends. The pressure drop due to three-dimensional effects linearly increases with the number of bends in a system and may significantly affect the total pressure drop. To suppress this and some other unwelcome tendencies either the ducts perpendicular to the magnetic field should be electrically separated, or the flow direction in the neighbouring ducts should be made opposite, so that leakage currents cancel each other.

Performance improvement of a high-speed aero-fuel centrifugal pump through active inlet injector

2020 ◽  
pp. 095441002096096
Author(s):  
Jia Li ◽  
Xin Wang ◽  
Wancheng Wang ◽  
Yue Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Turbulence Model ◽  
High Speed ◽  
Flow Direction ◽  
Active Flow Control ◽  
Turbulence Models ◽  
Internal Flow ◽  
Geometrical Parameters ◽  
Centrifugal Pumps

This paper presents a high-speed aero-fuel centrifugal pump with an active inlet injector for an aero-engine aiming at regulating the internal flow field and improving overall hydraulic performance. Unlike most of the existing centrifugal pumps for aero-engines, an injector is designed and integrated with the pump to accomplish the active flow control. Firstly, by employing the energy equation in the pump, reasonable geometrical parameters of the injector are calculated. Then, a validation study is conducted with three known turbulence models, showing that simulations with the RNG κ- ε turbulence model can accurately predict the head and efficiency of the experimental pump. Finally, simulation results with the determined turbulence model are discussed. The results show that the static pressure is uniformly distributed inside the impeller, the volute and the injector. The flow field is significantly ameliorated by improving the pressure inside the suction pipe and controlling the flow direction via the injector. Furthermore, the head and efficiency of the designed pump with an active inlet injector are improved compared to the one without an injector.

scholarly journals Influence of the Longitudinal Magnetic Field on the Formation of the Bead in Narrow Gap Gas Tungsten Arc Welding

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1351 ◽  
Author(s):  
Xiaoxia Jian ◽  
Hebao Wu
Keyword(s):  
Magnetic Field ◽  
Arc Welding ◽  
Molten Pool ◽  
Longitudinal Magnetic Field ◽  
Side Wall ◽  
Experimental Results ◽  
Narrow Gap ◽  
Welding Arc ◽  
Maximum Value ◽  
Side Walls

The oscillation arc assisted by an extra alternating longitudinal magnetic field (LMF) in narrow gap tungsten arc welding is proved to be effective in avoiding welding defects due to insufficient fusion at the side walls in joining thick wall plates. The behavior of the welding arc and molten pool under the LMF is simulated to reveal the influence of the LMF on the formation of a uniform penetration weld bead. A unified mathematical model was developed for the narrow gap tungsten arc welding including the plasma arc, molten pool, electrode, and their interactions. Under the LMF, the whole welding arc is deflected and oscillates between the two side walls. When the magnetic-field strength is larger than 6 mT, the axis of the arc deflects to the side wall; the maximum value of heat flux at the bottom decreases by one-half, and the maximum value at the side wall is increased by a factor of ten. On the other hand, under the LMF, the forces acting on the molten pool are changed; the fluid flow pattern is helpful to increase the heat transferred to the side walls. The model is validated by experimental results. Both the percentage deviations of the simulation weld penetration at the side wall and at the bottom from the experimental results are lower than 10%.

Magnetic Control of Biologically Inspired Robotic Microswimmers

2011 ◽  
Author(s):  
U. Kei Cheang ◽  
Jun Hee Lee ◽  
Paul Kim ◽  
Min Jun Kim
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
High Speed ◽  
Low Reynolds Number ◽  
Rotating Magnetic Field ◽  
Power Supplies ◽  
Magnetic Control ◽  
Function Generator ◽  
Flagellar Filament ◽  
Low Reynolds

Bacterial flagella have been employed as nanoactuators for biomimetic microswimmers in low Reynolds number fluidic environments. The microswimmer is a dumbbell-like swimmer that utilizes flagellar hydrodynamics to achieve spiral-type swimming. Flagellar filaments from Salmonella typhimurium are harnessed and functionalized in order to serve as couplers for polystyrene (PS) microbeads and magnetic nanoparticles (MNPs) using avidin-biotin chemistry. The MNP have an iron oxide core that will allow us to actuate the microswimmer under a rotating magnetic field. Using a micromanufacturing process, microswimmer of different configurations can be created to mimic mono- and multi-flagellated bacteria. A magnetic control system consists of electromagnetic coils arranged in an approximate Helmholtz configuration was designed, constructed, and characterized. In conjunction with a LabVIEW input interface, a DAQ controller was used as a function generator to generate sinusoidal waveforms to the power supplies. AC current outputs were supplied from the power supplies to the coils in order to generate a rotating magnetic field. A rotating magnetic field will induce rotation in the flagella conjugated MNP which in term will rotate the flagellar filament into a spiral configuration and achieve propulsion, as in polarly-flagellated bacteria. A high-speed camera provided real-time imaging of the microswimmer motion in a static fluidic environment inside a closed PDMS (Polydimethylsiloxane) chamber. The microswimmers exhibited flagellar propulsion in a low Reynolds number fluidic environment under a rotating magnetic field, which demonstrates its potential for biomedical applications.

Numerical and experimental investigation of magnesium/aluminum laser welding with magnetic field

2021 ◽  
Author(s):  
Jiafu Zhou ◽  
Dianwu Zhou ◽  
Jinshui Liu
Keyword(s):  
Magnetic Field ◽  
Liquid Metal ◽  
Laser Welding ◽  
Molten Pool ◽  
Three Dimensional ◽  
Flow Region ◽  
Metal Vapor ◽  
Element Distribution ◽  
Welding Pool ◽  
Metal Vapor Plasma

Abstract A three-dimensional numerical model for thermal-fluid-metallurgical coupling was established to inspect the effect from a stable longitudinal magnetic field on molten pool of magnesium/aluminum laser welding. Magnetic field-assisted laser welding platform was built to test the morphology and spectrum of the metal vapor/plasma. The scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) were used to determine the morphology and element distribution of molten pool cross section. Simulation results showed that temperature gradient of molten pool was reduced, heat distribution became uniform, and keyhole area was enlarged. In addition, the flow velocity of molten pool was increased, the vorticity of molten pool was improved, and the flow region of liquid metal was enlarged. Experimental results showed that penetration of molten pool was deeper, the shape of welding pool tended to be symmetrical and the density of Al element distribution in welding pool was increased by magnetic field. Thus, heat and mass transfer in welding pool was promoted due to the application of magnetic field, the elements exchange and the convection of liquid metal were accelerated, and the distribution of Mg-Al compounds should be dispersed under the agitation of Lorentz force. It’s predicted that the distribution of Mg-Al compounds in magnesium/aluminum laser welding would be positively affected by magnetic field, which was beneficial to control the weld quality. Hence, numerical results and experimental verification shared good consistency.

Sign in / Sign up

Export Citation Format

Share Document