SHORT-CRACK TOUGHNESS AND ABRASIVE MACHINING OF SILICON-NITRIDE

Citation
Hhk. Xu et al., SHORT-CRACK TOUGHNESS AND ABRASIVE MACHINING OF SILICON-NITRIDE, Journal of the American Ceramic Society, 79(12), 1996, pp. 3055-3064
Citations number
32
Categorie Soggetti
Material Science, Ceramics
ISSN journal
00027820
Volume
79
Issue
12
Year of publication
1996
Pages
3055 - 3064
Database
ISI
SICI code
0002-7820(1996)79:12<3055:STAAMO>2.0.ZU;2-M
Abstract
Hardness and toughness are often used to analyze the abrasive machinin g behavior of ceramic materials, However, toughness values of silicon nitride ceramics with microstructures containing elongated grains incr ease with crack extension, The present study investigates the effect o f toughness on the process of abrasive machining to determine which va lue of toughness should be used in the analysis. The toughness curves (i.e., toughness as a function of crack length) of ten different silic on nitride materials are characterized by an indentation-strength tech nique and an indentation technique, The forces in surface grinding are measured as a function of the depth of cut, Examination of ground sur faces by scanning electron microscopy indicates that the material-remo val processes in grinding follows the formation of short cracks (i.e., microcracks) and grain-scale material dislodgement. An indentation fr acture model for material removal in abrasive machining is used to cor relate the grinding forces with toughness and hardness of the material s. An agreement is obtained between the experimental results and the i ndentation model only when the toughness associated with short cracks is used. This study shows the importance of using appropriate toughnes s values corresponding to the microfracture processes in analyzing abr asive machining results for materials possessing rising toughness curv es.