Parallel finite element methods for the simulation of parachute dynamics and control

Computer simulation of parachute dynamics can significantly reduce parachute design costs. However, existing finite element models are incomplete and time-consuming because parachute modeling is very complex and computationally intensive. The goal of this research is to develop efficient and accurate parallel finite element methods for computer simulation of parachute dynamics and control. It includes development of parallel finite element algorithms, a geometrically nonlinear anisotropic constitutive model and a model for pneumatic muscle actuators. ^ Parallel computation techniques were developed and incorporated in a finite element code to simulate the nonlinear dynamic behavior of flexible structures. Parallel procedures were developed for nonlinear time integration based on the HHT method. The procedures for generating the tangent stiffness matrix and the effective force vector, solving the linearized system equations and other miscellaneous operations were implemented in parallel. By using parallel finite element algorithms, the computation time for the structural dynamics simulations is reduced tremendously. ^ A new anisotropic constitutive model was presented to simulate the geometrically nonlinear dynamic behavior of general anisotropic membranes experiencing large deformations. This model relates the 2nd Piola-Kirchhoff stress with the Green-Lagrange strain in a 3-D convected curvilinear coordinate frame. The construction of the anisotropic constitutive law from the predefined principal material coordinate system to the final convected curvilinear coordinate system using coordinate transformations was presented. Several numerical examples were given for validation. ^ A new finite element model for simulating pneumatic muscle actuator was also developed. Anisotropic membrane elements are used in this model to simulate the pneumatic muscle actuator\u27s nonlinear behavior. Application of pneumatic muscle actuators for parachute control and the validity of the model were demonstrated by numerical examples.