0,00 1,00 2,00 3,00 4,00 5,00 6,00 0,5 1 1,5 2 KI/KIc ; KII/KIIc µ=0,25 Al HMG KI/KIC KII/KIIc thickness y/a K/Kc 0,00 0,01 0,02 0,03 0,04 0,05 0,06 0,5 1 1,5 2 KI/KIc ; KII/KIIc µ=0,25 Al FGM KI/KIC KII/KIIc thickness y/a K/Kc (a) (b) Figure 6. KI/KIc and KII/KIIc for µ=0.25 and aluminium: (a) TiN HMG, (b) TiN FGM. In Fig. (6) is possible to see that for TiN film HMG over aluminium substrate, the fracture mode I is more importante than the mode II and the values are significativelly higher compared with TiN steel cases. For TiN film FGM over aluminium substrate, the mode of fracture II is more important than the mode I, although the values are not high compared with TiN HMG Al and similar to TiN FGM steel cases. 4. Conclusions From the theoretical analysis using ANOVA variance study to investigate the influence of factors such as friction, thickness, substrate material and film structure and the relationship between microcracks and failure criteria for fracture modes I and II in coating films, the following conclusions can be drawn. For both fracture failure modes I and II, the material factors, substrate and film structure, have higher significance than other factors analyzed. Film thickness is a significant factor, but not at the same level as material factors. Aluminium substrate with homogeneous structure, HMG, coating has a higher risk level than steel substrate. The functionally graded structure, FGM, films reduce drastically the fracture failure risk mode I and II, when compared with HMG films, for both substrate. On FGM films, and HMG thin films over steel substrate, the mode II is more important than the mode I, although the values are not high. For other cases, the mode I is more significant. The friction, altough is an important factor, has not the same significance level when compared with the others investigated. Acknowledgements Prof. Dr. José D. Bressan, for his contributions on Fracture Mechanics. Prof. Dr. Luis César Fontana, for his contributions on thin films. University of Santa Catarina State – UDESC, PGCEM, FAPESC and CNPq for financial support.
RkJQdWJsaXNoZXIy MjM0NDE=