Finite Element Analysis of R-Curve Behavior in Ceramics Using the Damage Model Based on the Cohesive-Zone Relationship

The evaluation of the R-curve behavior of ceramics, which is characterized by an increase in crack resistance with crack propagation, is crucial for advancing their implementation in engineering applications that require high reliability. In this study, we investigated the applicability of a finite element analysis (FEA) approach that implements a continuum damage model embedded with a cohesive-zone relationship to predict crack occurrence and the subsequent increase in crack resistance (toughness) of ceramics. Specifically, by employing a compliance-based method, the R-curve behavior was systematically examined under a bending load to assess the impacts of fracture stress and toughness on diverse chevron-notched specimens. The output critical stress intensity factors were found to increase with the crack length, eventually converging nearly to the input fracture toughness. Subsequently, the stable crack growth behavior obtained from the FEA and experiment under a three-point bending test of high-purity alumina was compared. A consistent result was confirmed in the force–displacement relationships. Furthermore, the R-curve behavior of the target material could be indirectly evaluated using the present approach. The results support the effectiveness of the present approach, highlighting the quantitative assessment of not only crack initiation but also R-curve behavior under arbitrary boundary conditions.