10:40

conference time (CEST, Berlin)

conference time (CEST, Berlin)

Smart Material Database Enrichment Using a Mixed Approach combining Data Science with Experimental Data and Virtual Testing

28/10/2021 10:40 conference time (CEST, Berlin)

Room: E

M. Salmi (MSC Software France - groupe Hexagon, FRA)

The current industrial context is highly challenging. More agility is expected and reduced time to market strategies are key for businesses to grow. One key technology for advancing the product innovation process is virtual testing. An efficient implementation of virtual testing requires efficient and accurate material models. This is particularly true in the framework of complex materials like reinforced plastics and plastics for additive manufacturing.
The classical workflow for generating virtual material laws is based on 3 main steps: First, costly experimental campaigns should be conducted. Second, post processing of the raw experimental data should be executed by dedicated human resources. Finally, the best suited material laws should be selected and implemented to be used in further virtual testing at part level. This process is labour intensive and time consuming. Consequently, it is not suited for today’s business pace.
The proposed approach aims at enriching material databases by leveraging the power of experimental data, virtual testing and data science through a 4 steps workflow: First, an optimal experimental campaign is designed and executed. This first step is conducted smartly through a well-chosen Design of Experiments (DoE). The Smart DoE is designed using data science tools like correlation matrices, advanced sampling techniques and computation of reliability indices. Second, data science algorithms and tools are applied for filling smartly the gaps that are lacking in the initial spare experimental material database. The key step is based on combined data science tools like correlation, interpolation, proper order decomposition and reduced order modelling. Third, multiscale material modelling is deployed for connecting the different length scales. This is performed for different microstructures and different conditions. Fourth, a second data science pass is implemented aiming at enriching the final material database for different scenarios of microstructures and conditions. This is performed through data science tools like meta-modelling.
The conducted work will report qualitative and quantitative results comparing the costing of classical approaches for building material databases to the proposed workflow. Considerable gains in time cost, data richness and overall Time to Market efficiency are reported and analysed.

data science, machine learning, ai, material database, experimental data, virtual testing, database enrichment

11:00

conference time (CEST, Berlin)

conference time (CEST, Berlin)

Application of the Finite Element Method to Modeling the Effective Mechanical and Thermomechanical Properties of Metamaterials of the 3D Lattice Structure

28/10/2021 11:00 conference time (CEST, Berlin)

Room: E

M. Yakovlev, P. Tanasevich (Fidesys LLC, RUS); A. Vershinin, V. Levin (Lomonosov Moscow State University, RUS); K. Zingerman (Tver State University, RUS)

Metamaterials are composite materials, the properties of which are determined primarily by their geometric microstructure, and not by the properties of the components included in their composition. Such materials have a cellular structure and are manufactured using a 3D printer. The report describes an approach to a numerical estimation of effective (averaged) properties of metamaterials, based on the calculations on the periodicity cell of the material.
Two types of metamaterials were studied. The first kind is metamaterials with negative Poisson's ratio (NPR), which when stretched in one direction expand in the other two. Such materials are used in medicine (stenting), in the manufacture of "smart" filters, to increase the strength of structures experiencing shock loads, in the manufacture of protective and damping materials. For NPR metamaterials, a numerical estimation of effective elastic properties was carried out - in particular, Poisson's ratios. Six boundary value problems of the elasticity theory with various periodic boundary conditions were solved at the periodicity cell of the material. Each problem corresponds to the particular case of effective strain tensor of a cell: three uniaxial tensions and three shear deformations. Distributions of stress tensors obtained as a result of solving problems were averaged over the volume. Effective elastic properties were estimated as a relation between the stress tensor and the strain tensor. We studied a dependence of the effective Poisson's ratios on the geometric parameters of the metamaterial cell. The parameters of cells, in which the Poisson's ratio comes to -1, were found.
In addition, metamaterials with a negative thermal expansion coefficient (NTE), which shrink when heated, were studied. Such structures are made of two components: a harder one with a smaller thermal expansion coefficient and a softer one with a larger coefficient. To be precise, the materials that, when heated and cooling, do not change their sizes are of practical interest. They can be used in microchip devices, adhesive fillings, dental fillings and high-precision optical or mechanical devices in environments with varying temperatures. For NTE metamaterials, a numerical estimation of the effective thermal expansion coefficients was carried out. We solved the boundary value problem of thermoelasticity on a periodicity cell with a given heating value and periodic boundary conditions, allowing the cell to deform arbitrarily strongly, while remaining a periodicity cell. The strain tensor field, obtained as a result of solving the problem, was averaged over the volume. The effective thermal expansion was estimated in the form of a linear dependence of the effective deformation tensor on the heating value of the cell. We studied the dependence of the effective thermal expansion coefficients on the geometric parameters of the metamaterial cell. The parameters of the cells, under which the effective thermal expansion coefficient is negative and maximized by the module, are found - as well as the parameters under which it is almost equal to zero. Calculations of the cell stability were performed with the obtained parameters to thermal deformation for deeper analysis.
The calculations of effective properties were carried out using the Fidesys Composite software module of CAE Fidesys. The report presents the results of calculations in the form of graphs of dependences of effective properties on the geometric parameters of the cell.
The work was supported by the Russian President's grant for young scientists - Ph.Ds MD-208.2021.1.1.

Metamaterials, Lattice Structures, Theory of Elasticity, Thermoelasticity, Auxetics, Negative Thermal Expansion, Effective Properties, Finite Element Method

11:20

conference time (CEST, Berlin)

conference time (CEST, Berlin)

Creep Modelling of a Short Glass Fiber Reinforced Thermoplastic

28/10/2021 11:20 conference time (CEST, Berlin)

Room: E

B. Schneider, E. Moosbrugger (Robbert Bosch GmbH, DEU)

In this contribution the mechanical behavior of a short glass fiber reinforced thermoplastic under creep loading is modeled. To do this, an elastic-plastic-viscoplastic model is taken and its parameter are adapted on quasistatic as well as creep experiments.
As starting constitutive model, an isotropic one is chosen. It consists of a linear elastic model and a rate-independent plastic model with piecewise linear isotropic hardening. In order to account for the creep flow, the elastic-plastic model is supplemented by a vicoplastic (creep) model with power law stress dependency of the flow and isotropic strain hardening. In the next step, the isotropic model is enhanced by anisotropy. This is done to account for the characteristic anisotropic behavior of short fiber reinforced thermoplastics that comes from the orientation of the fibers developing during the injection molding process.
In order to adapt the parameter of the constitutive model, uniaxial tensile quasistatic and creep experiments on dog bone shaped specimen are performed. The specimen are cut out of 120 mm x 80 mm x 2 mm injection molded plates: on the one hand aligned with the main flow direction (0°) and on the other hand transversal to the main flow direction (90°). First, 0°- and 90°-specimen are tested under quasistatic loading showing the typical higher stiffness and strength in the stress-strain response of the 0°-samples compared to the 90°-ones. Second, both types of specimen are tested under creep loading where the prescribed force is applied within seconds and then kept constant over many hours. This is done for several different load levels where the typical stress dependency of the creep flow is observed. As expected, creep flow appears at lower load levels for the 90°-samples.
Finally, the capability of the model with the adapted parameter is tested on creep experiments of a semi-complex bottle-type demonstrator part at different load levels.

Creep, short fiber reinforced thermoplastics, viscoplasticity, anisotropy

11:40

conference time (CEST, Berlin)

conference time (CEST, Berlin)

Simulation of Adhesive Squeezing in Car Body Assembly

28/10/2021 11:40 conference time (CEST, Berlin)

Room: E

E. Husser (Simufact Engineering GmbH - Part of Hexagon, DEU); L. Jusufi (Audi AG, DEU)

Adhesive bonding is a widely applied joining method in car body assembly processes. Up to now, the application of adhesive joints is still based on empirical experience and investigation studies. A numerical simulation tool could drastically improve the process understanding and optimize the manufacturing process in an early stage of development. In addition, the simulation tool can serve as a time and cost saving alternative to expensive prototype testing. This requires a robust and efficient simulation method including a valid material model.
During the assembly, the adhesive is not cured and behaves like a non-Newtonian fluid. The measured viscosity curves can be highly non-linear, i.e., the viscosity depends strongly on the local shear rate. In the present work, a material model, which can take arbitrary nonlinearities in the viscosity curve into account, is developed. The numerical model is validated by experimental squeeze flow tests which are conducted at different squeezing velocities. The flow behaviour is qualitatively compared by means of cross section pictures from which the velocity profile can be estimated. For comparison, the classical power law relation is considered in the simulations. It is shown that for highly non-linear viscosity curves, this simple approach results in a high error, especially at high shear rates.
The validated viscosity model is then applied to an exemplary assembly process of automotive body parts. In this feasibility study, two sheet parts, connected to other car body parts, are bonded together. During this process, the adhesive bead is squeezed into a thin layer. The simulation provides information about the final distribution of the adhesive, the squeezing force, and the extent of distortions in the joined and connected parts. The obtained results can be considered in subsequent joining processes. This is illustrated by the example of an automotive assembly process involving resistance spot welding as a subsequent assembly operation.

Joining, non-Newtonian flow, squeeze flow, finite element method