The metal transfer behavior is one of the most pivotal links of gas metal arc welding (GMAW) for improving the welding quality. Arc impacts the current path and heat input on the droplet surface, in reverse, the metal droplet detachment makes the arc to flicker. It is hard to make the metal transfer process clear with only experimental methods since the limited measuring space and high temperature in the welding region. In this work, with the help of computational fluid dynamics software ANSYS FLUENT, a magnetohydrodynamic model including argon arc plasma and steel wire and the droplet is constructed by using two independent governing equations of gas and metal phase for the mass, momentum, and energy balance. Comparing the magnetic field controlled GMAW with conventional GMAW, the temperature field, current density distribution, electric potential field, static pressure field and also metal vapor mass fraction distribution are highlighted. It is shown that the metal transfer frequency decreases and droplet diameter increases with 180 A welding current when applying an external constant axial magnetic field 0.002 T. So, the arc length decreases before the detaching moment, the current density expands in the arc region and the voltage decreases. The centrifugal movement impedes the downward flow and transfers heat from the droplet center to the outside region.

Porous asphalt pavement can reduce noise and improve road safety and driving comfort on rainy days. The seepage model derived from the one-way gradient flow theory cannot truly reflect the seepage process of rainwater inside the drainage layer. In this study, the drainage performance of porous asphalt pavement with different designs was evaluated using a three-dimensional seepage finite element method (FEM), and the drainage capacity of porous asphalt pavement was calculated using short-term rainfall intensity. The results indicated that the drainage capacity of porous asphalt pavement can be effectively improved by increasing cross slopes, the surface course layer thickness, and the permeability coefficient of porous asphalt mixture. Moreover, the pavement width had a significant impact on the drainage performance of porous asphalt pavement.

Magnetic field has been used in welding technology for many years because of its good control effect and easy installation. The different mass and heat transfer behaviors of magnetic field control ...

For gas metal arc welding (GMAW), increasing the welding current is the most effective way to improve welding efficiency. However, much higher current decreases the welding quality as a result of metal rotating-spray transfer phenomena in the high-current GMAW process. In this work, the external axial magnetic field (EAMF) was applied to the high-current GMAW process to control the metal transfer and decrease the welding spatters. A unified arc-droplet coupled model for high-current GMAW using EAMFs was built to investigate the metal rotating-spray transfer behavior. The temperature fields, flow fields in the arc, and droplet were revealed. Considering all the heat transferred to the molten metal, the Joule heat was found to be the dominant factor affecting the droplet temperature rise, followed by the anode heat. The conductive heat from the arc contributed less than half the value of the other two. Considering the EAMFs of different alternating frequencies, the arc constricting effects and controlled metal transfer behaviors are discussed. The calculated results agree well with the experimental high-speed camera observations.

This study aimed to clarify the influence of a longitudinal external magnetic field (EMF) on arc characteristics, metal transfer behavior, and weld bead formation in metal-cored arc welding (MCAW) process. The work focused on comparing two distinct conditions: without EMF (0 mT) and with EMF applied at a magnetic flux density (MFD) of 6 mT, evaluated by high-speed video observations and numerical simulation models for a welding current of 320 A. Experimental results indicated negligible changes in droplet transfer frequency between the two conditions, but significant differences were observed in arc behavior and weld pool characteristics. The application of EMF intensified arc brightness and increased weld penetration depth from 3.7 mm (no EMF) to 4.2 mm (EMF 6 mT). Simulation results revealed that EMF induced rotational plasma flow and reduced pressure at the arc column center, which resulted in an increased plasma velocity directed toward the weld pool surface. Consequently, a depression was observed at the weld pool surface to enhance the weld bead penetration. The findings highlight the potential of EMF as a valuable tool to optimize MCAW processes, particularly when precise penetration control and improvement of weld quality are required.