ABSTRACT:

The sound emitted during the arc welding process is closely related to the welding phenomenon, and sometimes it provides useful information for monitoring and controlling the welding process. It is important to use different kinds of information's to control the welding process to improve the quality of controlling system, especially for underwater welding. Because the recovery process of weld defects is a time and money consuming matter, and sometimes it is difficult to monitor the arc condition by a visual system. The fundamental analysis of acoustic "signals and their relations with the other parameters such as arc voltage, arc current and a vibration of weld plate had been carried out in order to understand the feature of acoustic signals and to develop effective signal processing algorithm. All of the data were recorded by the cassette recorder. After the experiment was completed, the analysis of recorded data was carried out by using of a signal processor and a computer system. Generally, welding arc sound is not so loud, because the turbulence of shielding gas and arc column is small. A big noise is generated by the sudden change of welding condition. When the droll let of the electrode touches the weld pool, rapid decrease of voltage causes the decrease of the pressure on the arc. On the contrary, the pressure becomes high, when the arc is regenerated. Both of these pressure vibration durations are short. These features are easily detected by the monitoring of arc voltage and current In the case of burn through condition, the changes of arc voltage and amperage are not much enough to detect the situation clearly, but the arc sound becomes loud and it continues until the burn through condition will be finished. In this case, the usage of acoustic signals is useful.

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