The Study On Secondary Development & Large Deformation Of ANSYS

POWER-FEM is a general purpose finite element analysis software developed by China Agricultural University, which is applicable to such as static, dynamic, linear, nonlinear problems etc. especially geometric non-linear ones. While solving geometric non-linear problems, POWER-FEM elements are designed by finite deformation theory, and precise computations are performed. ANSYS is a widely used finite element analysis software. It has powerful functions in pre-process and post-process, and sharing data with other softwares. It provides three developing tools for users.In order to let POWER-FEM to share the merits of ANSYS in pre-process and post-process and data communication, the secondary development of ANSYS was introduced in this paper. ANSYS' function in creating user element was expanded by dynamic linking library. The independence of user elements was strengthened in ANSYS. The subroutine library of POWER-FEM was added to ANSYS as user element. So POWER-FEM can be fully utilized by ANSYS.In this paper the TL method in finite deformation theory was briefly introduced, by which the definition of strain, the relationship between computation stress and true stress, the concept of reference configuration and the computation of unbalance force were analyzed. We found that the definition of strain in ANSYS is only approximate, without consideration the changing of configuration. Furthermore the relationship between stress and strain does not satisfy the work conjugate principle, which leads to the incorrect of the equilibrium equation. Besides, ANSYS cannot provide the transformation relationship between the stress calculated by ANSYS and the Cauchy stress. The comparing results of rod, 2D and 3D examples show that geometric non-linear computation in ANSYS is only approximate, and true displacement solution can be approached by more loading steps only when the deformation is not large. So it is suggested and realized that geometric non-linear elements of POWER-FEM based on the precise finite deformation theory replace the homologous elements in ANSYS.