Theoretical exploratory investigation on reliability of advanced ceramics by discrete element simulation

The increasing application of silicon nitride in biomedical and other engineering fields has elevated the necessity to understand its reliability. Due to the complexity of producing pure material researchers have been analyzing the behavior of the material with flaws. In this thesis several scenarios are simulated with the support of PFC2D to analyze microcrack propagation depending on the position, quantity and size of the voids to understand the effect each of the cases have on the material. A four point bending test was applied to each case twice recording the loading force. Having two runs allows doing a statistical analysis in Minitab using ANOVA to make the proper conclusions based on the p-value. According to the first case subsurface defects have a significant effect on the loading force, which lead us to simulate several positions with a void closer to the lower surface in the y-axis or x-axis. The position of the void along the y-axis starting closer to the lower wall of the silicon nitride showed a significant effect on the loading force. In contrast with the y-axis, the voids located along the x-axis with a separation from the lower wall of 20 microns did not show any effect on the loading force. A new comparison was made with two voids of different radius, on this case there was no significant effect on the strength of the material with the parameters selected by the user, but it matched the crack initiation from experimental data starting at the void with the bigger radius. Another case simulated was adding clusters to the silicon nitride which showed a significant improvement on the reliability of the silicon nitride and matched real life sample. The learning experience of using the software to conduct simulations is the accordance it has with real life experiments; it is a good alternative to understand the reliability and the possible failures of a heterogeneous silicon nitride on real life application such as implants, bearings among others