University of Twente Student Theses


A solid-shell element for use in sheet deformation processes and the EAS method

Quak, Wouter (2007) A solid-shell element for use in sheet deformation processes and the EAS method.

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Abstract:Sheet deformation processes can be simulated by using the finite element method. The used finite elements for simulation of these processes in 3 dimensions are mostly shells. These elements are suited for situations in which in-plane dimensions are considerably larger than the thickness dimension. Recently a new group of elements has been introduced named ‘solidshells’. These elements are a mixture between solid bulk elements and shells and try to take the benefits of both sides. Goal of this research is investigating and developing a solid-shell element for use in the in-home developed software package DiekA of the Mechanics of Forming Processes group at the University of Twente. First the general background of the solid-shell is investigated. The locking phenomena that prevent the use of standard solid bulk elements in thin walled geometries are treated. These locking phenomena can be especially present in low thickness geometries. One of the most important methods to alleviate several types of locking is the EAS (Enhanced Assumed Strain) method. To get familiar with the EAS method, an element was programmed. This 2d linear quadrilateral contains extra internal modes of deformation due to the EAS method. Several tests were performed in which the element shows very good performance in bending and incompressible situations with respect to the standard quadrilateral. Finally a non-linear simulation of a ‘freebending’ deformation process showed that less EAS elements could be used to give the same performance as would be the case with standard not-enhanced quadrilaterals. Scanning literature revealed an interesting solid-shell element, named ‘RESS’. The base of the element is a 3d linear 8 node hexagonal. Several methods are used to get good shell performance of this element. These are: reduced integration in in-plane directions accompanied by a physical stabilization procedure, the EAS method and a B-bar method. The element was programmed both linear and geometric non-linear in C++ with aid of the FeaTure toolbox. The element is tested first in a geometric linear thin walled problem. The performance is very good especially in incompressible situations. Secondly the geometric non-linear situation is tested. A simulation of the bending of a strip shows good comparison with shell elements. Both the 2d EAS programmed element and the 3d RESS element can be very beneficial for use in sheet deformation processes.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
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