Deviation of a needle from its intended path can be minimized by using a robotic device to steer the needle towards its target. Such a device requires information about the interactions between the needle and soft tissue, and this information can be obtained using finite element (FE) analysis. In this study, we present an FE analysis that integrates the Johnson–Cook damage model for a linear elastic material with an element deletion-based method. The FE analysis is used to model a bevel-tipped needle interacting with gel. The constants for the damage model are obtained using a compression test. We compare simulation results with experimental data that include tip–gel interaction forces and torques, and three-dimensional (3D) in situ images of the gel rupture obtained using a laser scanning confocal microscope. We quantitatively show that the percentage errors between simulation and experimental results for force along the insertion axis and torque about the bevel edge are 3% and 5%, respectively. Furthermore, it is also shown qualitatively that tip compression is observed at the same locations in both experimental and simulation results. This study demonstrates the potential of using an FE analysis with a damage model and an element deletion-based method to accurately simulate 3D gel rupture, and tip–gel interaction forces and torques.

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The design of extrusion dies depends on the experience of the designer. After the die has been manufactured, it is tested during an extrusion process and machined several times until it works properly. The die is designed by a trial and error method which is expensive interms of time consumption and the amount of scrap. Research is going on to replace the trial pressing with finite element simulations that concentrate on material and tool analysis. In order to validate the tool simulations, an experiment is required for measuring the deformation of the die. Measuring the deformation of the die is faced with two main obstacles: high temperature and little free space. To overcome these obstacles a method is tried, which works by applying a laser beam on a reflecting surface. This cheap method is simple, robust and gives good results. This paper describes measuring the deformation of a flat die used to extrude a single U shape profile. In addition, finite element calculation of the die is performed. Finally, a comparison is performed between experimental and numerical results.

Finite element analysis in aluminum extrusion is faced by several problems such as number of degrees of freedom, calculation time, large deformation and flow conservation. The problem of large deformation is overcome by applying the Eulerian formulation. The problems concerning number of degrees of freedom, calculation time can be overcome by simplifying the model especially at the bearing corner. On the one hand, detailed modeling of the bearing corner will increase the complexity of the analysis. On the other hand, simplified modeling of the bearing corner will face problems such as locking of the bearing corner node and loss of flow conservation. A sharp corner and modified corner geometry are examples of the simplified modeling. Moreover, boundary conditions will be applied at the bearing corner node in order to solve the problem of its locking and to satisfy the flow conservation condition. These boundary conditions include specifying a normal or formulating a constraint equation. This paper focuses on the calculation of the normal or constraint equation that can be applied either at a sharp corner or after modifying the corner geometry. Different elements are checked in this study such as plane strain, axisymmetric and tetrahedron elements. Finally, the extrusion force and average exit velocity are investigated and compared with a reference model. In the reference model a round corner with 0.5mm radius is built, contact boundary condition is applied between the die and aluminum, and Arbitrary Lagrangian Eulerian formulation is applied. The finite element analysis is performed in the in-house implicit finite element code "DiekA".

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