Description
Multiscale discrete element modeling (DEM) was employed to investigate microscopic mechanisms behind time effects in sand. A static-fatigue hypothesis was adopted, which suggests that delayed fracturing of grain-surface textural features is the key cause behind time effects in sand. A microscopic DEM model of a single contact between two grain surfaces was constructed. Each of two surfaces at the contact was simulated by an assembly of subparticles bonded together. The parallel-bonded stress corrosion model (PSC) was used to mimic time-dependent fracturing of surface textural features. Atomic force microscopy (AFM) measurements were used to characterize the texture of the surfaces of silica sand grains. The grain surface geometry in the numerical model was generated conforming to the statistical distribution of elevations of asperities from AFM measurements. The mechanical parameters of the model were calibrated with grain-to-grain physical load tests. Numerical load tests, both normal and shear, were conducted on the contact model. Time-dependent increase in normal convergence and gradual increase in the number of contact points between the two surfaces followed from the simulations. The stiffness and shear resistance of the contact in the numerical simulations were found to increase over time. The contact properties tested at the single-contact scale were later used to simulate the behavior of grain assemblies. The results indicated that the contact fatigue is a plausible cause of time-dependent changes in sand. These results are consistent with the static-fatigue hypothesis.
Recommended Citation
Wang, Z., & Michalowski, R. (2014). Investigation of mechanisms responsible for time effects in sand using multiscale discrete element modeling. In A. Bajaj, P. Zavattieri, M. Koslowski, & T. Siegmund (Eds.). Proceedings of the Society of Engineering Science 51st Annual Technical Meeting, October 1-3, 2014 , West Lafayette: Purdue University Libraries Scholarly Publishing Services, 2014. https://docs.lib.purdue.edu/ses2014/mss/mmpm/10
Investigation of mechanisms responsible for time effects in sand using multiscale discrete element modeling
Multiscale discrete element modeling (DEM) was employed to investigate microscopic mechanisms behind time effects in sand. A static-fatigue hypothesis was adopted, which suggests that delayed fracturing of grain-surface textural features is the key cause behind time effects in sand. A microscopic DEM model of a single contact between two grain surfaces was constructed. Each of two surfaces at the contact was simulated by an assembly of subparticles bonded together. The parallel-bonded stress corrosion model (PSC) was used to mimic time-dependent fracturing of surface textural features. Atomic force microscopy (AFM) measurements were used to characterize the texture of the surfaces of silica sand grains. The grain surface geometry in the numerical model was generated conforming to the statistical distribution of elevations of asperities from AFM measurements. The mechanical parameters of the model were calibrated with grain-to-grain physical load tests. Numerical load tests, both normal and shear, were conducted on the contact model. Time-dependent increase in normal convergence and gradual increase in the number of contact points between the two surfaces followed from the simulations. The stiffness and shear resistance of the contact in the numerical simulations were found to increase over time. The contact properties tested at the single-contact scale were later used to simulate the behavior of grain assemblies. The results indicated that the contact fatigue is a plausible cause of time-dependent changes in sand. These results are consistent with the static-fatigue hypothesis.