Finite Element Simulation And Optimization Of Geogrid Manufacture

As a new type of geosynthetics introduced into China within recent years, geogrid has been widely used in various civil engineering projects such as highway, airport, dam, etc, because of its excellent mechanical property and low cost. Although both geogrid and its manufacturing equipments have already been successfully produced by Chinese manufacturers, the fundamental research on the manufacturing of geogrid has just begun. In this paper, the finite element code ABAQUS has been applied in the simulation of geogrid manufacture. And based on the simulation analysis, a new means of optimizing the geogrid manufacture has been proposed.This paper begins with an introduction of some basic concepts in the geogrid manufacture such as the manufacturing equipments, national standards and characterization of geogrid, which is followed by a summary of the recent development of the international research on geogrid manufacturing. Some theories of oriented polymer and its strengthening effect are also included in this paper, such as the mathematical models describing the molecular orientation. Experiments were also carried out to investigate the performance of polymer during stretching at various strain rates. Based on the experimental data, the strain strengthening effect, as well as the strain rate sensitivity of polymer materials, was analyzed.Some key problems involved in the modeling of geogrid manufacture using ABAQUS are also studied in this paper, for instance, the building of solid model, boundary condition setting, meshing, multiple step analysis as well as the constitutive model of polymer materials.The finite element simulation of the manufacture process of uniaxial geogrid has been implemented with ABAQUS in order to study the distribution of stress and strain during stretching as well as its relationship with the dimension of the holes punched on the extruded plastic plates. In this paper, the influence of the hole's fillet radius on strain and stress is studied. And it is found that by increasing the fillet radius the maximum strain during stretching decreases, while deformation along the stretch direction is reduced. Besides, the effect of drawing rate on the stretching process is also analyzed and it is found that drawing rate has different effect on different parts of geogrid. High speed drawing can increase the deformation of geogrid's rib while the stretching deformation of geogrid's node is increased by reducing the stretch rate.Based on the previous finite element simulation, a new means of optimizing the geogrid manufacture has been proposed. By modifying the size and the shape of the holes punched on the plastic plate, the distribution of strain and stress during stretching can be improved so that the probability of various defects can be minimized. A new pattern of holes has also been designed for the uniaxial geogrid stretching and its feasibility has been examined through finite element simulation.