Dresden 2006 – wissenschaftliches Programm
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MM: Metall- und Materialphysik
MM 23: Mechanical Properties I
MM 23.4: Vortrag
Mittwoch, 29. März 2006, 14:45–15:00, IFW B
Investigation of crack formation in single-crystal sapphire due to combined normal and lateral forces — •Maksim Karniychuk1, Thomas Chudoba2, Volker Linss2, and Frank Richter1 — 1Chemnitz University of Technology, Institute of Physics, 09107 Chemnitz, Germany — 2ASMEC Advanced Surface Mechanics GmbH, Bautzner Landstr. 45, 01454 Radeberg, Germany
One difficulty in contact mechanics is the detection of crack formation and the evaluation of the critical tensile stresses responsible for this effect. Nanoindentation is a non-destructive method for in situ detection of mechanical failures for instance by the observation of pop-in events in normal force-displacement curves. However, a direct observation of indentation induced pop-in events for many materials such as single-crystal sapphire is often very difficult. Another problem is that there exist ambiguous failure reasons without application of additional methods for the investigation of the failure.
The failure formation in single-crystal sapphire was detected in situ during combined normal and lateral force-displacement measurements by using a new Lateral Force Unit together with a commercial UMIS-2000 nanoindenter. Further analysis allows to conclude that crack opening is the first failure after pure elastic deformation. Thus, the knowledge of the critical lateral and normal forces can be used for the calculation of the critical tensile stress for crack formation with the help of a theoretical model for elastic deformation. The critical tensile stress value was estimated 9.5-10.5GPa.