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Structural Engineering and Mechanics
  Volume 30, Number 2, September30 2008, pages 177-190

Simulation of material failure behavior under different loading rates using molecular dynamics
Kunhwi Kim, Jihoon Lim, Juwhan Kim and Yun Mook Lim

    Material failure behavior is generally dependent on loading rate. Especially in brittle and quasi-brittle materials, rate dependent material behavior can be significant. Empirical formulations are often used to predict the rate dependency, but such methods depend on extensive experimental works and are limited by practical constraints of physical testing. Numerical simulation can be an effective means for extracting knowledge about rate dependent behavior and for complementing the results obtained by testing. In this paper, the failure behavior of a brittle material under different loading rates is simulated by
molecular dynamics analysis. A notched specimen is modeled by sub-million particles with a normalization scheme. Lennard.Jones potential is used to describe the interparticle force. Numerical simulations are performed with six different loading rates in a direct tensile test, where the loading velocity is normalized to the ratio of the pseudo-sonic speed. As a consequence, dynamic features are achieved from the numerical experiments. Remarkable failure characteristics, such as crack surface interaction/crack arrest, branching, and void nucleation, vary in case of the six loading cases. These characteristics are interpreted by the energy concept approach. This study provides insight into the change in dynamic failure mechanism under different loading rates.
Key Words
    dynamic fracture mechanics; rate dependency; molecular dynamics; energy concept approach.
Kunhwi Kim, Jihoon Lim, Juwhan Kim and Yun Mook Lim:
School of Civil and Environmental Engineering, College of Engineering, Yonsei University 134, Sinchon-dong, Seodaemun-gu, Seoul 120-749, Korea

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