1,263 research outputs found
COMPUTATIONAL MODELS FOR THE SIMULATION OF THE FORMING PROCESS OF CARTON PACKAGES
No full textThis paper synthetically describes new numerical tools developed for the simulation of the mechanical process of forming carton packages for beverages.
Two topics are here considered: the simulation of the folding process of the paperboard along pre-formed crease lines and the simulation of the interaction between the container and the filling liquid. For the first topic, an interface finite element and constitutive model is proposed to simulate the presence of crease lines in a paperboard. The proposed model, formulated in terms of axial forces and bending moments, accounts for progressive plasticity and damage in the creased material, showing a good correspondence with the results of bending tests for varying initial crease characteristics.
For the second topic, a fully Lagrangian finite element method for fluid-structure interaction problems is proposed. The method is inspired to the so called particle finite element method, first introduced by Idelsohn and O\~{n}ate and is based on a continuous Delaunay re-triangulation of the mesh. The method is providing good results for 2D problems, while extension to 3D problems and to the interaction with shell structures is currently in progress
Selective mass scaling for distorted solid-shell elements in explicit dynamics: optimal scaling factor and stable time step estimate
No full textThe use of solid-shell elements in explicit dynamics has been so far limited by the small critical time step resulting from the small thickness of these elements in comparison with the in-plane dimensions. To reduce the element highest eigenfrequency in inertia dominated problems, the selective mass scaling approach previously proposed in [G. Cocchetti, M. Pagani and U. Perego, Comp. \& Struct. 2013; 127:39-52.] for parallelepiped elements is here reformulated for distorted solid-shell elements. The two following objectives are achieved: the critical time step is governed by the smallest element in-plane dimension and not anymore by the thickness; the mass matrix remains diagonal after the selective mass scaling. The proposed approach makes reference to one Gauss point, trilinear brick element, for which the maximum eigenfrequency can be computed analytically. For this element, it is shown that the proposed mass scaling can be interpreted as a geometric thickness scaling, obtaining in this way a simple criterion for the definition of the optimal mass scaling factor. A strategy for the effective computation of the element maximum eigenfrequency is also proposed. The considered mass scaling preserves the element translational inertia, while it modifies the rotational one, leading to errors in the kinetic energy when the motion rotational component is dominant. The error has been rigorously assessed for an individual element, and a simple formula for its estimate has been derived. Numerical tests, both in small and large displacements and rotations, using a state-of-the-art solid-shell element taken from the literature, confirm the effectiveness and accuracy of the proposed approach. Copyright {\copyright} 2014 John Wiley \& Sons, Ltd
EXPLICIT BACKWARD DIFFERENCE-OPERATORS AND CONSISTENT PREDICTORS FOR LINEAR HARDENING ELASTIC-PLASTIC CONSTITUTIVE LAWS
No full textA variationally consistent generalized variable formulation for enhanced strain finite elements
No full text
Solution of Large Eigenproblems on a Microcomputer
No full textA microcomputer program is presented for determining
the lowest eigenfrequencies of large structural
systems by using the finite element method.
The solution procedure is based upon the subspace
iteration technique. Householder's tridiagonalisation
and the Q L method are used in order to solve
the eigenproblem in the reduced space at each
iteration. The computer code has been implemented
in BASIC and its present version is suitable
for the solution of eigensystems with 1000-2000
degrees of freedom. The features of the program
are pointed out and numerical tests are presented.
It is shown that very accurate results can be obtained,
although the computer system we have
used sets a few constraints which often imply very
long computing times (particularly when large
bandwidth systems are given)
Stima dell'errore per l'integrazione temporale di tipo 'backward-difference' in plasticità computazionale, Una
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