Calibration of brittle fracture models by sharp indenters and inverse analysis

In several engineering areas structural analyses concern also fracture processes of brittle materials and employ cohesive crack models. Calibrations of such models, i.e. identification of their parameters by tests, computer simulations of the tests and inverse analyses, have been investigated in the literature particularly with reference to non-destructive indentation tests at various scales. To this timely research, the following contributions are presented in this paper: a simple piecewise-linear cohesive crack model is considered for brittle materials (here glass, for example); for its calibration by “non-destructive” indentation tests novel shapes are attributed to instrumented indenters, in order to make fracture the dominant feature of the specimen response to the test; such shapes are comparatively examined and optimized by sensitivity analyses; a procedure for inverse analysis is developed and computationally tested, based on penetration versus increasing force only (no imprint measurements by profilometers) and is made “economical” (i.e. computationally fast, “in situ” by small computers) by model reduction through proper orthogonal decomposition in view of repeated industrial applications.