Advances in understanding of damage formation during laser-assisted milling of ZnO-based varistor ceramics

Muženič, David (author), Kramar, Davorin (author), Pušavec, Franci (author)

Zinc oxide (ZnO)-based varistor ceramic is a hard-to-machine material. Its microstructure, developed for its electrical properties, results in extremely low fracture toughness. Therefore, the current state-of-the-art in machining this material is lapping. In the present work, laser-assisted milling (LAMill) of ZnO ceramics was evaluated with a systematic approach to allow for new insights and advance the understanding of damage formation during machining of this material. A machining strategy to machine ceramic workpieces along the edge was studied. Additionally, a new transient analytical thermal model was developed to accurately predict laser-induced temperatures near the edge of the workpiece without excessive use of computational power, and the model predictions were experimentally verified. A novel approach to evidence machining-induced damage with the mathematical description of the ideal machined surface was also designed and tested. It was found that at higher temperatures the propagation of intergranular fractures is inhibited. Another mechanism based on the material porosity and contributing to more instances of intergranular crack initiation has been identified. To reliably predict the extent of damage on the machined surface, the analysis has been extended by covering the effects of the two identified influential process parameters: feed per tooth, f$_z$, and the temperature of the to-be-cut material, T. By adjusting these parameters, surface damage was successfully controlled and the extent of damage was minimized at f$_z$ = 0.18 mm and T = 380 °C, achieving a 44 % reduction compared to the conventional process with the same machining parameters.

• Language: English
• Keywords: laser-assisted milling, ZnO ceramics, thermal model, damage formation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2022
• Number of pages: Str. 1478-1491
• Numbering: Vol. 84
• PID: 20.500.12556/RUL-143838
• UDC: 621.7
• ISSN on article: 1526-6125
• DOI: 10.1016/j.jmapro.2022.11.008
• COBISS.SI-ID: 130224387
• Publication date in RUL: 13.01.2023

Record is a part of a journal

• Title: Journal of manufacturing processes
• Shortened title: J. manuf. process.
• Publisher: Elsevier, Society of Manufacturing Engineers
• ISSN: 1526-6125
• COBISS.SI-ID: 1281557

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: lasersko rezkanje, ZnO keramika, toplotni modeli, nastanek poškodb

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P2-0266
• Name: Napredne izdelovalne tehnologije za visokokakovostno in trajnostno proizvodnjo

• Funder: ARRS - Slovenian Research Agency
• Project number: L2-1836
• Name: Razvoj in implementacija inovativne tehnologije obdelave ZnO keramike z definirano rezalno geometrijo v serijsko proizvodnjo za povečanje kakovosti varistorjev kot končnih izdelkov