5/27/2023 0 Comments Cargolifter cl160![]() ![]() As it is well known that the structures are most sensitive against imperfections in the shape of the lower buckling modes, they also give an idea of a conservative imperfection and can be applied to the ideal model as geometric (stress-free) modifications which is a simple function in the case of ANSYS. Load factors are estimates for an upper limit of the ultimate load buckling modes show, how the structure will buckle. The results are buckling modes and load factors. Limit load investigations of thin-walled structures are usually started with a linear buckling analysis. For the application considered in this paper this can be used to translate model and result data into formats to be read by external programs in addition to pre- defined interfaces. Last but not least the ANSYS command language (ANSYS Parametric Design Language APDL) includes a lot of elements of a higher programming language. Solutions of nonlinear equations are obtained by a Newton-Raphson method using both direct as well as iterative solvers for the sequence of linear systems of equations. Bonded contact can be used to tie together surfaces with different meshes. Unprecise discretization and not modeled gaps or interferences can be automatically accounted for by options and parameters. Penalty and Lagrange methods can be chosen to fulfil the contact conditions. Shell thicknesses (updated due to transverse contraction in large-strain analysis) are included. Contact analysis is implemented where the user must only specify the two potential contact surfaces. Shell elements can be used with a number of material models such as plastic, hyperelastic as well as creep behavior. Problems with large rotations as well as with large strains can be handled. Reduced Integration can optionally be chosen for in-plane stiffness. The behavior of low order Mindlin elements is improved by an „assumed strain“ formulation for the shear strains. The implemented bending theory is based on Mindlin kinematics or so-called Discrete Kirchhoff conditions. ANSYS is a general purpose FE-program for static, dynamic as well as multiphysics analysis and includes a number of shell elements with corner nodes only and with corner and mid-side nodes. Limit load analysis, stability problems, imperfections, quasi-static dynamic, explicit time integration, plastic material, shell structures, ANSYS, LS-DYNA, ANSYS/LS-DYNA ANSYS is a finite element system developed by ANSYS, Inc., Canonsburgh, PA., USA the finite ele- TM ment system LS-DYNA is developed by Livermore Software Technology Corporation (LSTC), Livermore, CA., USA the CAD-FEM GmbH is an engineering company with main competence in finite element method and is distributor of both ANSYS as well as LS-DYNA. Aspects of discretization, solution control, consideration of imperfections and methods of checking the results are outlined. Then we focus on the remaining benefits of implicit analysis and how a proper combination of ANSYS and LS-DYNA can be used to prepare the transient analysis by common preprocessing and static analysis steps. discussing general properties of implicit Finite Element analysis using ANSYS and explicit analysis using LS-DYNA it is shown when and how quasi-static limit load analyses can be performed by a transient analysis using explicit time integration. ![]()
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