Geometric Nonlinear Analysis Of Fabric Material Based On UMAT Subroutine

The deformation of fabric, whose simulation is widely used in many fields, such as CAD for garments and virtual reality, is a hot topic in the field of fabric mechanics. Since the eighties of the twentieth century, fabric was modeled as the orthotropic continuum, whose simulation was studied with FEM method. Through many compare work, it was found that the simulations did not well agree with the experiment observations, and some deformations could not even been predicted. Finally Y T Zhang founded fabric constitution, which was widely used later.ABAQUS is one of the most capable software especially for simulating nonlinear problems, which does not confine the symmetry of constitution relationship. It provides an open interface and some user subroutines that allow users to expand the main function in the form of code. Although many kinds of material constitutions are given in ABAQUS, the constitutive model of fabric material needed in this research is not provided and it is necessary to redevelop it by user-defined material subroutine interface.Based on ABAQUS software, the UMAT of fabric material is developed with FORTRAN. The UMAT subroutine shows correctness and accuracy by element tests for isotropic and anisotropic material under tension. With geometric nonlinear algorithm, the stress field and U3 displacement field of fabric sheet draping for two boundary conditions, fixed to free and fixed to sliding, are given. The draping of fabric over a rectangular desk is simulated. Through many results'comparing, the interface developed is of feasibility and accuracy and the simulation is credible.