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Session 21

Modeling of Cone Penetration Test Using SPH and MM-ALE Approaches
The American Society of Association Executives (ASAE) Soil Cone Penetrometer Standard (S313.2) is designed to characterize general soil mechanical conditions. Its results are used predominantly for comparative purposes. Variations of this test are used for in-situ determination of the geotechnical engineering properties of soils and delineating soil stratigraphy. This paper presents a comparison between experimentally obtained results of cone penetration test with results from LS-DYNA®/MPP simulations performed on a high performance cluster computer. The previously reported experiments (conducted by USDA-ARS National Soil Dynamics Laboratory, Auburn, AL, USA) were performed on Norfolk Sand. These experiments show the variation in results for test conducted under identical conditions. In the LS-DYNA simulations, the soil was modeled using the material model MAT_005 Soil and Crushable Foam. Two approaches were used to represent the soil: a hybrid approach that combined Lagrange and Smoothed Particle Hydrodynamic (SPH) methods and the Multi Material Arbitrary Lagrangian - Eulerian (MM-ALE) method. The vertical resistance force versus penetration distance of the penetrometer cone was compared to the experimental results. A close match between numerical results and experimental data was obtained in the study for the Norfork Sand. The response simulated using the two numerical approaches were almost identical. A sensitivity study revealed that the penetrometer force was most sensitive to the soil density followed by sensitivity to a failure surface parameter.
Simulation of charge and structural behaviour in an tumbling mill
For a long time discrete element methods (DEM) has been used as simulation tools to gain insight into particulate flow processes. Such a process may be grinding in tumbling mills, where the mechanical behaviour is complex. To include all phenomena that occur in a mill in a single numerical model is today not possible. Therefore, a common approach is to model milling charges using the DEM assuming a rigid mill structure. To close the gap between reality and numerical models in milling, more physically realistic methods must be used. In this work, the finite element method (FEM) and the smoothed particle hydrodynamic (SPH) method are used together to model a ball mill charge in a tumbling mill. The mesh free formulation and the adaptive nature of the SPH method result in a method that handles extremely large deformations and thereby suits for modelling of grinding charges. The mill structure consists of rubber lifter and liners and a mantel made of solid steel. It is modelled with the finite element method. For the elastic behaviour of the rubber, a Blatz-Ko hyper-elastic model is used. The supplier of the lining provided experimental data for the rubber. The deflection profile of the lifters obtained from SPH-FEM simulation shows a reasonably good correspondence to pilot mill measurements as measured by an embedded strain gauge sensor. This computational model makes it possible to predict charge pressure and shear stresses within the charge. It is also possible to predict contact forces for varying mill dimensions and liner combinations.
Application of LS-DYNA SPH Formulation to Model Semi- Solid Metal Casting
Semisolid metal alloys have a special microstructure of globular grains suspended in a liquid metal matrix. This particular physical state of the matter can be exploited to produce near-net-shape parts with improved mechanical properties. Indeed, semi-solid processes take advantage of a much higher apparent viscosity of the die cast materials by limiting the risk of oxide formed on the free surfaces to become incorporated into the casting when the material is injected into the die. Semi-solid processes that use billets as feedstock material are however tied up with an additional type of surface contamination. During the injection phase, the external-skin on the periphery of the billet, which has been in contact with air and lubricant during the transfer in the shot sleeve may be incorporated into the casting. This can be an important cause of reject for most structural parts in the automotive industry. In order to predict and control the occurrence of skin inclusion into cast parts during the injection phase of semi- solid processes, Lagrangian methods are appropriate. Indeed, the skin, composed of contaminated or even partially solidified metal, has different mechanical properties compared to the core of semi-solid aluminum. Abitrary- Lagrangian-Eulerian formulations, which can account for the coupling between the “solid” skin and the flow of “semi-solid” aluminum are promising but still necessitate a huge amount of computer power. On the other hand, particle based Smoothed Particle Hydrodynamics (SPH) approaches are particularly well suited to this kind of flows involving complex flow behavior and solidification. These methods are able to track accurately free surface flows with fragmentation and break up as well as to follow the advection of oxides through the flow. In this paper, a first analysis is performed in order to investigate the potential of the SPH solver of LS-DYNA to deal with the problem of skin inclusion in semi-solid die casting processes. Preliminary results show that the SPH approach is a very promising simulation tool to follow the skins during semi-solid injection casting.
Hypervelocity impact of aluminium sphere against aluminium plate : experiment and LS-DYNA correlation
High velocity impact of 3 mm diameter aluminium sphere against thin aluminium target plate has been performed at impact velocity of about 4000 m/s with the two stage light gas gun HERMES at Thiot Ingenierie laboratory. Impacts at normal incidence and with a 32° angle generate debris clouds that were collected by an aluminium witness plate. The visualization of the debris clouds generated after the impact has been realized by using an ultra high speed framing camera. LSDYNA 3D Smooth Particle Hydrodynamics and 2D&3D Multi- Material ALE solvers (MMALE) were used to reproduce debris clouds generation and expansion in the two angle configuration. Agreement between simulations and experimental frames are discussed.