Explicit Finite Element Method for Transparency Impact Analysis

摘要

This report documents new analytical methods for the solution of soft-body impactproblems, including birdstrike. The approach is based on explicit finite element techniques which allow for very detailed material modeling and make efficient use of the current generation of supercomputers. The most important improvements in the present work over previous efforts are in the areas of soft-body impact loading, material modeling, and treatment of layered wall constructions. Impact loads are obtained directly by including the impacting body in the finite element model, eliminating the need for ad hoc loading models. Both the transparency and the soft body materials may be rate-sensitive, exhibit nonlinear bulk behavior, and may fail during the finite element solution. Methods have been developed to make commercial graphics software (PATRAN) deal correctly with failed elements for results output. An improved model of laminated shells is included in the plate and shell element so that each layer of a multilayered transparency need not be modeled with distinct elements, even when soft interlayers are present. The methods described have been implemented in an explicit finite element code X3D. User and programmer information are included in the report as appendices. Applications described in the report include two standard test problems and an F-16 birdstrike simulation.