Author(s): Jie Gu; Zhenyu Lei; Hang Yin; Guoping Zhang
Linked Author(s):
Keywords: Finite element modeling; Hyperelasticity; Marine flocs; Mechanical properties; Nanocompression
Abstract: Naturally formed marine flocs collected from the Atchafalaya Bay in the Gulf of Mexico were tested under nanocompression in a nano universal testing machine (Nano UTM) mounted with a specially designed environmental cell. With the assumption that the initial deformation of a spherical floc under compression is fully elastic and follows the Hertzian elastic contact theory, the reduced modulus and yield shear strength of the floc were obtained. Finite element modeling with a trial-and-error approach was employed to analyze inversely the stress-strain behavior of the floc material by simulating the experimental nanocompression load-displacement curves. The floc was modeled with 4-node bilinear, axisymmetric quadrilateral, hybrid elements and the loading platens were modeled as a rigid body. Contact pairs were established between the tip and the floc. Owing to the large deformation, a hyperelastic model was selected to describe the small-strain elastic behavior, while an elasto-plastic model with an isotropic hardening rule with yield shear strength from experiments was used to account for the mechanical response after yielding. Comparison between the experimental and numerical results indicates that a combination of the above two models can account for the mechanical behavior of very soft tenuous floc material. This integrated experimental and numerical investigation can shed light on future studies focusing on the mechanics and transport behavior of cohesive marine sediments.
Year: 2013