How Hydrogen Dielectric Strength Forces the Work Voltage in the Electric Discharge Machining

• Type: Article in International Scientific Journal
• Date: 2018-05-15

Authors

José António Almacinha (Author) FEUP; António Mendes Lopes (Author) FEUP; Pedro Rosa (Author) Other; José Duarte Marafona (Author) FEUP

Journal

Title: Micromachines

Vol. 9 No. 5

Pages: 1-11

ISSN: 2072-666X

Publisher: MDPI

Indexing

ISI Web of Knowledge - 10 Citations

Scopus - 10 Citations

INSPEC

Scientific classification

CORDIS: Technological sciences > Engineering > Mechanical engineering

FOS: Engineering and technology > Mechanical engineering

Other information

Authenticus ID: P-00P-WGG

DOI: 10.3390/mi9050240

Abstract (EN): An electro-thermal model based on the Joule heating effect is proposed to simulate a single discharge in an electric discharge machining process. Normally, the dielectric strength of the hydrocarbons oil is approximately 20 MV/m, but it varies with both the thickness of the film and its decomposition. After the breakdown, the hydrocarbon oil has an average dielectric strength value of 2 MV/m. This value is close to the dielectric strength of the hydrogen, which is the main gas that results from the hydrocarbon oil decomposition, at temperatures between 6000 K and 9000 K. Therefore, the electric discharge occurs in a hydrogen atmosphere that imposes both the discharge gap and the work voltage. A 200 V voltage is associated to a 100 m discharge gap, leading to a 20 V work voltage. Therefore, the 3 V work voltage control corresponds to approximately 15 m. In other words, the increase of the discharge gap originates other discharge during the discharge pulse. The work voltage control, together with the multiple discharge method, is taken into account. The 100 m discharge gap corresponds to the higher value of the transitory discharge gap that over evaluates the material removal and the tool wear rates. The results of the numerical simulations are validated with experimental data.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11