A numerical investigation is used to design test geometries and loading histories that are suitable for probing the mode II bridging effect of through-thickness reinforcement at high strain rates. The bridging effects are represented by a cohesive law and tests are sought that will determine any rate dependence in its parameters. The End Notched Flexural test is used as reference test, because it allows easy application of time dependent loading and has proven to be an information-rich test in the quasi-static case. Information content in the dynamic case is addressed by focusing on regimes within the full computed solution space where crack growth is approximately steady state, the crack sliding speed is constant, and the crack profile is at least partially linear. These conditions simplify the inverse procedure for identifying model parameters, allowing quick insight into the information content of experiments. The estimates of information content are conservative, in that analysis of the total solution regime will necessarily contain more information than analysis of the regimes of simple behavior alone. Numerical analyses are performed to verify if hypothetical rate-dependence in the cohesive law causes strong and measurable changes in the regimes of simple behavior when the tests are properly selected to vary the crack sliding speed.
The design of dynamic tests to infer rate dependence in large-scale crack bridging
MASSABO', ROBERTA;
2009-01-01
Abstract
A numerical investigation is used to design test geometries and loading histories that are suitable for probing the mode II bridging effect of through-thickness reinforcement at high strain rates. The bridging effects are represented by a cohesive law and tests are sought that will determine any rate dependence in its parameters. The End Notched Flexural test is used as reference test, because it allows easy application of time dependent loading and has proven to be an information-rich test in the quasi-static case. Information content in the dynamic case is addressed by focusing on regimes within the full computed solution space where crack growth is approximately steady state, the crack sliding speed is constant, and the crack profile is at least partially linear. These conditions simplify the inverse procedure for identifying model parameters, allowing quick insight into the information content of experiments. The estimates of information content are conservative, in that analysis of the total solution regime will necessarily contain more information than analysis of the regimes of simple behavior alone. Numerical analyses are performed to verify if hypothetical rate-dependence in the cohesive law causes strong and measurable changes in the regimes of simple behavior when the tests are properly selected to vary the crack sliding speed.
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