1994 年 60 巻 9 号 p. 1274-1278
This paper describes the crack formation process by a scratching on the surface of glass. The process is observed dynamically with a dynamic observation a.id recording system which was developed by the authors. The mechanism of the generation and growth of cracks is discussed based on the observation and the three dimensional structure of cracks. Furthermore, the influence of scratching conditions such as scratching speed or loading weight on the crack formation process is discussed. The main results obtained are as follows; (1) Cracks can be classified into three types, that is, cracks A, B, C in Fig. 10. (2) After a scratching indenter passed over, crack C grows in the lateral direction at the crack front of crack A which has been already formed. (3) Crack B is also a lateral crack, while it grows more puickly than crack C directly from the top of the indenter. (4) The crack formation process is significantly affected with scratching conditions.