On the behaviour of obsidian under scratch test

This study deals with the mechanical characterization of three types of obsidian with scratch tests. These obsidians have been selected for their archeological interest and, in particular, they have been taken in three different sites in Turkey: Bingöl, Nenezi Dag and Kayirli. Known as being brittle, the mechanical analysis of such material requires a special attention. The porosity is measured by optical method. The incremental scratch test is used to determine the critical normal load and the constant scratch test is used to determine the toughness. Two types of indenters, conical and spherical, have been used. Three regimes of damage have been observed, the micro-ductile, the micro-cracking and the micro-abrasive regimes. It has been found that the obsidian from Nenezi Dag is more tough than the two others and, in the same time, that it has a lower porosity than the others.