4th Workshop on Structural Analysis of Lightweight Structures


Session 1: Markets & Products

Time: 9:45 - 12:00

9:45 - 10:15
Structural design optimization under transient nonlinear mechanical behavior: Optimal structure topology for automotive crashworthiness

E.J. Wehrle (TU Munich)

The use of structural design optimization to ascertain optimal topology of structures under transient nonlinear behavior, exemplified by automotive crash, remains a challenge. This is due to both computational effort of the simulation and handing of the system responses. Developments in efficient optimization algorithms as well as increased computer speed and capacity has now enabled the examination of optimal topology of structures undergoing crash and impact. Different methods are currently be investigated for varying loading and degrees of nonlinear behavior. These can be categorized in two general families:

  1. efficient optimization algorithms to reduce the number of nonlinear simulations needed
  2. single or multiple linear elastostatic replacement loads to approximate the true system

In this presentation, methods being analyzed and expanded at the Associate Professorship of Computational Mechanics (Prof. Duddeck) of the Technical University of Munich will be shown. For the former, structural design optimization using hybrid cellular automata will be introduced and results shown. For the latter, three methods to represent a transient nonlinear structural model with a linear elastostatic model and their application in topology optimization will be addressed: single replacement loads, multiple replacement loads and multiple replacement loads with updating. To conclude, a comparison will be drawn in addition to providing an outlook to these methods.

10:20 - 10:50
Finer-scale characterization and modeling at UIBK - Application to optimization of FRC components

R. Lackner (University of Innsbruck)

The benefits of incorporating finer-scale information into material modeling are threefold:

  1. Chemical and physical processes within the material can be considered at the scale of their occurance, enabling a more realistic description of the underlying processes.
  2. As the finer-scale information is linked to the macroscopic material behaviour via homogenization techniques, quantification of the effect of the aforementioned chemical and physical processes on macroscopic properties becomes accessible.
  3. Finally, with this link between finer scales and the macroscale being established, goal-oriented optimization of materials and structural members becomes possible.

The basis of this so-called multiscale approach in material modeling is the proper characterization of material properties at various length scales. The respective experimental results may either serve as input data describing the behaviour of material phases at finer length scales or provide experimental data for validation of underlying homogenization schemes. Accordingly, the first part of this presentation is devoted to the NanoLab at University of Innsbruck, installed as Core Facility of the University of Innsbruck in 2008, exclusively serving the purpose of multiscale characterization. Within this presentation, available experimental equipment and techniques will be addressed.

Within the second part of the presentation, a recently started joint research project on the optimization of FRC components is presented. This project, covering several lenght scales in material modeling strongly benefits from the available infrastructure at the NanoLab. This presentation will provide first insight into the obtained research results as regards both experimental characterization and multiscale modeling & simulation of FRC.

10:55 - 11:25
Determination of stable and robust material properties for the assessment of thermomechanically loaded components of rocket engines with viscoplastic constitutive equations

T. Seifert, I. Rekun (Offenburg University of Applied Science)Components of rocket engines as actively cooled combustion chambers must withstand high pressure as well as severe and complex thermal transients. To assess the mechanical behaviour of such components during design via finite-element calculations, constitutive models are necessary that describe the time and temperature dependent plasticity of the material appropriately.

Advanced models account for viscoplastic deformations including isotropic and kinematic hardening, recovery and ratcheting. However, the models contain a relatively large number of temperature dependent material properties that must be determined on the basis of data of material tests. The determination of the properties is a non-trivial task because it is not clear which loading history must be applied in the tests for a certain material to obtain stable and robust (i.e. objective) material properties. Thus, methods for the assessment of the stability and robustness of the properties are presented and results obtained in a project funded by the European Space Agency ESA are shown for material data of copper in the temperature range from 300 to 700 Kelvin.

11:30 - 12:00
Statistical Optimization and Structural Analysis:Design of handmade custom Snowboards
B. Caillaud