Evaluation of fracture incubation time from quasistatic tensile strength experiment

Incubation time being the main characteristic parameter for dynamic fracture process is experimentally measured for PMMA utilizing optical methods. The specimen is quasistatically loaded in standard tensile testing machine until brittle fracture occurs when the sample is split into two parts. Normally this splitting of brittle materials is accompanied by the impact unloading of the sample. In considered tests tensioned samples were dynamically unloaded by stress drop wave, generated by fracture process and registered by photoelasticity technique at a certain distance from breaking line. The same experiment is simulated using ANSYS FEM software package and the incubation time is evaluated numerically. The simulation results are in a good coincidence with experimental measurements, proving the applicability of the proposed simple method for brittle fracture incubation time measurements.