Anne-Marie Habraken

Single point incremental forming simulation with adaptive remeshing technique using solid-shell elements

Purpose – Numerical simulation of the single point incremental forming (SPIF) processes can be very demanding and time consuming due to the constantly changing contact conditions between the tool and the sheet surface, as well as the nonlinear material behaviour combined with non-monotonic strain paths. The purpose of this paper is to propose an adaptive remeshing technique implemented in the in-house implicit finite element code LAGAMINE, to reduce the simulation time. This remeshing technique automatically refines only a portion of the sheet mesh in vicinity of the tool, therefore following the tool motion. As a result, refined meshes are avoided and consequently the total CPU time can be drastically reduced. Design/methodology/approach – SPIF is a dieless manufacturing process in which a sheet is deformed by using a tool with a spherical tip. This dieless feature makes the process appropriate for rapid-prototyping and allows for an innovative possibility to reduce overall costs for small batches, since...

On the evaluation of the through thickness residual stresses distribution of cold formed profiles

The aim of this research is to evaluate the through thickness residual stresses distribution in the walls and in the corners of a cold‐formed open section made of a material presenting a non linear hardening behaviour. To get results as close as possible to the reality, the complete process is modeled, including coiling and uncoiling of the sheet before the cold bending of the corner itself. The elastic springback after flattening as well as after final shaping are also taken into account. In order to validate the model in predicting the residual stresses distribution, the presented results are confronted to experimental measurements and FE results collected from the literature.

A Novel Geometry for Shear Test Using Axial Tensile Setup

This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature), several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness.

Numerical Simulations of a Two Roll Round Bar Straightener

A finite element model of a two-roll round bar straightener has been developed to study the influence of key parameters on the straightening process. The present model already allows a better understanding of the process and the effects of straightening on the bar. A dedicated post-treatment is also proposed. It is particularly focused on the defect of the bar before and after straightening as well as rotation speed of the bar in order to validate the model. Other quantities are available : equivalent cumulated plastic strain and longitudinal stress for instance. This model is also the first step towards further analysis of the process such as, for example, parametric studies.

Application of an Advanced GTN Model

The present contribution consists of implementing an advanced GTN damage model as a “User Material subroutine” in the Abaqus FE code. This damage model is based on specific nucleation and growth laws. This model is applied to the prediction of the damage evolution and the stress state in notched specimens made of dual phase steel. By comparing numerical predictions with experimental results based on high-resolution X-ray absorption tomography, the numerical approach was improved and validated.Copyright