Measurement and calculation of plasma drag force in arc welding based on high-speed photography technology and particle dynamics

• A method employing particle dynamics to measure plasma drag force is proposed.
• The magnitude of plasma pressure is 103 Pa by experimental measurement.
• Increasing currents will reduce droplet size, mass, gravity.
• Increasing currents will increase droplet acceleration and arc plasma pressure.

To investigate the plasma drag force acting on the droplet in gas metal arc welding (GMAW), we used a high-speed photography system to image the metal transfer process, and proposed a method employing particle dynamics to measure the plasma drag force. Experimental results of the droplet diameter, mass, acceleration, plasma drag force and gravity acting on the droplet are presented. The results indicate that, with the increase of welding current, the droplet diameter, mass and gravity decrease, the droplet acceleration and plasma pressure increase, while the plasma drag force and the gravity acting on the droplet decrease. Moreover, we find that the plasma drag force is 10 and near 100 times the gravity acting on the droplet. The experimental values of plasma drag force and plasma pressure show good agreement with the theoretical value by fluid theory; their order of magnitudes are 10− 4 N and 103 Pa, respectively, which demonstrates that it is an effective method to analyze the plasma drag force of welding arc.

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