stand the PA and expand the application range from the conventional PA. Measurement of Experimental System This experimental study relied on the analysis of the data from measurements of pressure and heat associated with the arc. Scientists around the world have made great progress in the measurement of arc pressure. The pressure of plasma arc has been measured by pendulum with rotary optical encoder, U-tube barometer, and piezoelectric pressure transducer (Refs. 21–23). The temperature field in the arc column was measured by infrared radiation (IR) and spectroscopy (Refs. 24 - –26). The current distribution was measured by a series of annular anodes and split anode method (Refs. 27, 28). In the previous study, the authors measured the distribution of pressure and heat of the completely separated arc plasma and electron flow. However, systematic measurements needed to study the properties of the partially separated arc plasma and electron flow were lacking. Such properties and degree of the partial separation were critical for free control on the pressure and heat. An experimental setup was thus established to provide the ability to study the partial separation. Figure 1A illustrates the principle of the test platform, which is based on a split anode. Figure 1B and C shows the systems for pressure and heat measurement. A PAW power source and a GTAW power source (that are represented by A and B power sources in Fig. 1) were used to provide the total current that flows through the PAW torch. The torch was vertically fixed on a test stand and driven by a travel mechanism to implement translational motion and connected to the negative terminals of the both power sources. The workpieces were replaced by two watercooled copper blocks. One of them served as the electron flow receiver. It was connected to the positive terminal of the GTAW power source and used to separate the electron flow from the arc plasma partly or completely. It also received heat from the separated electron flow. Another served as the arc plasma receiver, which was connected to the positive terminal of the PAW power source and used to receive the heat and pressure from the arc plasma, containing the electron flow varying from 0 to WELDING RESEARCH Table 1 — Major Experimental Parameters No. Experimental Type PAW Current (A) GTAW Current (A) Plasma Gas Flow Rate (L/min) Arc Length (mm) 1 Pressure 100–0 0–100 3.0 4 2 Pressure 50 50 3.0 4–8 3 Pressure 50 50 2.5–3.5 4 4 Heat 100–0 0–100 3.0 4 5 Heat 50 50 3.0 4–8 6 Heat 50 50 2.0–4.0 4 220-sWELDING JOURNAL / JUNE 2016, VOL. 95 Fig. 1 — Test platform. A — Schematic diagram; B — experiment system for pressure measurement; C — experiment system for heat measurement. A C B
Welding Journal | June 2016
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