Mysteries of the arc cathode spot: a retrospective glance

Hantzsche, E.

doi:10.1109/tps.2003.818412

Cited by 82 publications

(44 citation statements)

References 17 publications

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“…The rapid movement of the cathode spot in vacuum and gaseous arc has not been elucidated yet and is called as random walk. Presence of impurities and work function variations is believed to be the causes of this random walk [23,24]. Since electrons are intensively emitted from a cathode spot, it is natural that arc plasma is concentrated on the spot.…”

Section: Discussionmentioning

confidence: 99%

Heat input analysis of variable polarity arc welding of aluminum

Cho

Lee

Bae

2015

Int J Adv Manuf Technol

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Influence of direct current electrode positive (DCEP) duty ratio in variable polarity (VP) arc welding of aluminum has been investigated in the current work. VP arc adopts alternate current (AC) of DCEP and direct current electrode negative (DCEN) as power source, and the duty ratio indicates the polarity's durational portion in the current pulse. Experimental results showed proportional relationship between heat input and DCEP duty ratio although there was a fluctuation due to the arc instability increase caused by wearing of the tungsten electrode tip. This observation violates the conventional arc theory of anode heating, and therefore, a new theoretical approach combining the tunneling effect and random walk of cathode spot has been proposed. During DCEP duration, arc is concentrated on thinner oxide cathode spot, which further melts and breaks the oxide layer of the spot. This process is repeated at another cathode spot at a high frequency. Therefore, the higher the DECP duty ratio, the more cathode spots are generated and the longer was the arc concentration time. This in turn resulted in a higher heat input for longer DCEP polarity duration. The proposed mechanism combining the tunneling effect and random walk of cathode spot can not only explain the anomalous results of the current research but also could address the ambiguous result of deeper penetration in thicker oxide in the past research.

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Section: Discussionmentioning

confidence: 99%

Heat input analysis of variable polarity arc welding of aluminum

Cho

Lee

Bae

2015

Int J Adv Manuf Technol

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“…The aim of the present Appendix is to study this question using as an example a cylindrical arc. An expression for the entropy production per unit length of the discharge may be found by applying equations (12) and (13) to the particular case of a cylindrical arc;…”

Section: Discussionmentioning

confidence: 99%

“…This principle has been extensively invoked in investigations of many gas discharge phenomena, in particular cylindrical arcs [4], effect of normal current density on glow cathodes [5], cathode spots in arc discharges [6]. Steenbeck's principle has still been used in the literature, e.g., [7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

What is the mathematical meaning of Steenbeck's principle of minimum power in gas discharge physics?

Benilov¹,

Naidis²

2010

J. Phys. D: Appl. Phys.

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It is shown that Steenbeck's principle of minimum power, or voltage, for discharges with fixed current is a not a corollary of the principle of minimum entropy production, in contrast to what is frequently assumed; besides, the latter principle itself does not provide a reasonable approximation in gas discharge physics. Similarly, Steenbeck's principle is not a corollary of mathematical models of gas discharges. Hence, this principle contradicts the mathematical models. A methodically correct evaluation of the error caused by the use of Steenbeck's principle requires a comparison of a solution obtained with the use of this principle with an exact solution to the same problem, rather than with experimental results or results deemed reasonable from the point of view of common sense. Such comparison is performed for two examples from the theory of a cylindrical arc column. The examples show that the error incurred by the usage of Steenbeck's principle is uncontrollable and may be unacceptably high.

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“…Therefore, basic research activities focus on discharge related phenomena on metallic probes under vacuum conditions [1,2], but also experiments where the gap between the electrodes is filled with a gas at atmospheric or higher pressure are of high importance [3,4]. The aim to reduce degradation effects caused on electrodes during operation is not only restricted to metals, but also to semi-conducting materials.…”

Section: Introductionmentioning

confidence: 99%