The capability of accurately reproducing the microstructural features of polycrystalline materials is of fundamental importance for the correct simulation of the micromechanical behaviour of materials. This paper describes the development and the implementation of VorTeX algorithm for the generation of numerical models representative of real polycrystalline microstructures, and its integration within LS-PrePost. The method presented offers high control over the grain size distribution of the final structure by adopting the so-called Laguerre-Voronoi tessellation techniques. Additional features implemented allow constraints to be imposed on the structure such as symmetrical boundaries and enables the introduction of interface entities (i.e. contacts and cohesive elements) on the grain boundaries to model inter-granular crack propagation.
A customized solution enabling the mapping of fiber orientations represented by beam elements in organic sheet materials from one simulation phase to another of the product development cycle has been developed using python scripting language. The strategy implemented for the mapping of the fiber orientations is based on the modeling approaches used for the input models in both types of simulation. The thermoforming simulation model consists of beam and shell elements representing the fiber and polymer layers in an organic sheet respectively while in the structural simulation, the component is usually modeled using only shell elements. The thermoforming simulation results (a .d3plot mesh) and structural simulation model input mesh are provided as inputs to the so called “BETA Mapper script”. The script segregates elements from each model into discrete volumes enabling parallel processing of the mapping procedure. The centroid coordinates of the elements from each matching cuboid are used to identify element pairs by finding the shortest distance between two element centroids. During the thermoforming process, the fibers, in the warp and weft directions of an organic sheet undergo a relative scissoring motion. In order to take this effect into consideration and to capture non-orthogonal fiber directions, the script is developed to produce three solutions and provides the possibility for mapping various types of part geometries. Developable geometries, which can be unfolded as a flat surface and do not exhibit any relative fiber scissoring, are mapped according to “Solution 1” and the part can then be simulated using assigned orthotropic material properties. “Solutions 2” and “3” implemented in the script, provide a methodology to enable the mapping of fiber orientations in two non-orthotropic directions in a single mesh model, which is not feasible with the generic approach using only one definition of the keyword (*PART_COMPOSITE). Additionally, “Solution 2” implemented in the script provides the user with the flexibility to choose the number of individual parts to be generated during the mapping. The method facilitates the realization of correctly mapped fiber orientations of the warp and weft yarns of an organic sheet in a single mesh model. With its three solutions, the “BETA Mapper script” provides the required data integrity between the different phases of organic sheet virtual product development and enables overall improvement in product design.
New cars are continuously becoming safer thanks to improvements in crash test regulations and standards. Currently crash test regulations and standards assess the safety performance of vehicles in frontal impacts under the precondition that the vehicle’s supporting structure is hit in such a way that the crumple zone absorbs energy during the crash. The General German Automobile Club (ADAC) accident research data shows, however, that in a car-to-car impact, the vehicle’s supporting structures might not hit in the same way as in the standard frontal impact tests. In these cases, the crumble zone of the vehicle cannot be fully utilized and this can lead to severe injuries. In 2010, the ADAC introduced a new test to assess the compatibility of vehicles in a car-to-car impact. In this test, a special honeycomb-shaped barrier is used, and its surface is scanned for evaluation after the test. This test with a progressive deformable barrier was named ADAC compatibility test or MPDB test.
The simulations of virtual models hold a key role during the design process of a vehicle. The numerus different components in a CAE model make its assembly one of the most demanding tasks during the model buildup. Over the last years, the effort to achieve higher accuracy in crash test simulations has resulted in more detailed models. As a result, the FE representations used to connect the different parts vary a lot and get complex sometimes. To support effectively such time-consuming and error-prone modeling processes, the available tools should offer increased automation and standardization levels. A commonly used method is to simulate the area of these connections by using different material properties representing effectively not only the material of the connecting flanges but also the heat affected zones in each flange. Ford-Werke GmbH in cooperation with BETA CAE Systems has come up with a fully automated process within ANSA pre-processor that reads the CAE and its connection file, assigning the proper connectivity to each connection. Additionally, with the use of external files assigns the needed materials in the area of each spotweld using the respective LS-DYNA keywords. Finally reports to the user the results of the assembly procedure and the final status of each connection. The current paper explains the basic terms of the automated process mentioned above. Moreover, it presents the techniques used within ANSA to assembly a full analysis model in a fast and robust way combining different FE-representations and multi material assignment in the area of a connection.
Implementation of a Method for the Generation of Representative Models of Polycrystalline Microstructures in LS-PrePost