43,651 research outputs found
A comparison of three Algorithms for Tracing Nonlinear Equilibrium Paths of Structural Systems
The relative efficiencies of the Riks/Wempner, CrisïŹeld, and normal flow solution algorithms for tracking nonlinear equilibrium paths of structural systems are compared. It is argued that the normal flow algorithm maybe both more computationally efficient and more robust compared to the other two algorithms when tracing the path through severe nonlinearities such as those associated with structural collapse. This is demonstrated qualitatively by comparing the relative behaviors of each algorithm in the vicinity of a severe nonlinearity. Quantitative results are presented for the collapse a blade stiffened panel
Closed form solution of the return mapping algorithm in elastoplasticity
In the present work a return mapping algorithm is discussed for small strain elastoplasticity boundary value problems with an exact closed form solution of the local constitutive equations. Nonlinear kinematic hardening rules are adopted in modelling kinematic hardening behavior of ductile materials. The local solution of the constitutive equations is expressed by only one nonlinear scalar equation which is subsequently reduced to a single variable algebraic equation. Due to the straightforward form of the nonlinear scalar equation the analytical solution of the algebraic equation is found in exact closed form. A remarkable advantage of the present approach is that no iterative solution method is used to solve the local constitutive equations in three-dimensional elastoplasticity. Numerical applications and computational results are reported in order to illustrate the robustness and eïŹectiveness of the proposed algorithmic procedure
Eulerian method for multiphase interactions of soft solid bodies in fluids
We introduce an Eulerian approach for problems involving one or more soft
solids immersed in a fluid, which permits mechanical interactions between all
phases. The reference map variable is exploited to simulate finite-deformation
constitutive relations in the solid(s) on the same fixed grid as the fluid
phase, which greatly simplifies the coupling between phases. Our coupling
procedure, a key contribution in the current work, is shown to be
computationally faster and more stable than an earlier approach, and admits the
ability to simulate both fluid--solid and solid--solid interaction between
submerged bodies. The interface treatment is demonstrated with multiple
examples involving a weakly compressible Navier--Stokes fluid interacting with
a neo-Hookean solid, and we verify the method's convergence. The solid contact
method, which exploits distance-measures already existing on the grid, is
demonstrated with two examples. A new, general routine for cross-interface
extrapolation is introduced and used as part of the new interfacial treatment
Geometric Convolutional Neural Network for Analyzing Surface-Based Neuroimaging Data
The conventional CNN, widely used for two-dimensional images, however, is not
directly applicable to non-regular geometric surface, such as a cortical
thickness. We propose Geometric CNN (gCNN) that deals with data representation
over a spherical surface and renders pattern recognition in a multi-shell mesh
structure. The classification accuracy for sex was significantly higher than
that of SVM and image based CNN. It only uses MRI thickness data to classify
gender but this method can expand to classify disease from other MRI or fMRI
dataComment: 29 page
Limit-point buckling analyses using solid, shell and solidâshell elements
In this paper, the recently-developed solid-shell element SHB8PS is used for the analysis of a representative set of popular limit-point buckling benchmark problems. For this purpose, the element has been implemented in Abaqus/Standard finite element software and the modified Riks method was employed as an efficient path-following strategy. For the. benchmark problems tested, the new element shows better performance compared to solid elements and often performs as well as state-of-the-art shell elements. In contrast to shell elements, it allows for the accurate prescription of boundary conditions as applied to the actual edges of the structure.Agence Nationale de la Recherche, France (ANR-005-RNMP-007
Exact finite element method analysis of viscoelastic tapered structures to transient loads
A general method is presented for determining the dynamic torsional/axial response of linear structures composed of either tapered bars or shafts to transient excitations. The method consists of formulating and solving the dynamic problem in the Laplace transform domain by the finite element method and obtaining the response by a numerical inversion of the transformed solution. The derivation of the torsional and axial stiffness matrices is based on the exact solution of the transformed governing equation of motion, and it consequently leads to the exact solution of the problem. The solution permits treatment of the most practical cases of linear tapered bars and shafts, and employs modeling of structures with only one element per member which reduces the number of degrees of freedom involved. The effects of external viscous or internal viscoelastic damping are also taken into account
- âŠ