CAE-Companion-2018-2019

Engineering WISSEN CAE

(Non parametric) Structural Optimization

Introduction The challenging topic of new conceptual designs requires appropriate optimization methods to ensure price competi- tiveness as well as best-in-class structural performance. The best result is achieved by an early and consequent use of optimization and a seamless integration of the procedures in the design process. Different optimization methods can be used to improve the design of new components or existing parts and assemblies. Parametric methods modify geometric parameters of a CAD or FEMmodel and are mostly used in the improvement phase or when considering aspects from different disciplines simultaneously. Non-parametric methods use the full design flexibility of CAE (simulation) models and do not require any additional time-consuming parametrization. The most striking advan- tage of the non-parametric approach is the ability to generate high quality concepts in an early phase of the design process - in particular to derive completely new innovative design topologies leading to improved product quality (simulation driven design, i.e. the simulation gives concept ideas to CAD-designers).

and simulation tools and eliminates manual, time-consuming, trial-and-error procedures. Depending on the type of modification performed at the component non-parametric methods are classified as topolo- gy, shape, sizing and bead optimization respectively. Topology Optimization Topology optimization is used in the initial design phase in or- der to generate new design suggestions. The design process starts with a maximum design space in which the structure is allowed to be placed. At this point geometric details can be disregarded as they are developed by the optimizer. Nevertheless existing contact regions, geometric and material nonlinearities should be considered as they can influence the solution significantly.

Figure 2: Process of topology optimization – design space, intermediate stage with different element densities, optimization result with “hard” remaining elements Based on the FEA results, the layout of the structural compo- nent is changed in a continuously repeated, fully autonomous process until an optimal design is obtained. In topology optimization the finite elements are possible design elements which are ‘added to’ or ‘removed from’ the structure. The adding and removing is controlled by a change of material properties - only elements of high density form the final supporting structure. Objective and constraint values for topology optimization can be chosen from: „ „ volume, mass, center of gravity, moments of inertia „ „ compliance, nodal displacements, rotations, reaction

Figure 1: Process of Structural Optimization The non-parametric optimization approaches are com- mercially available as tools which highly integrate into an automated optimization process in direct interaction with standard CAE and CAD programs. The optimization modules autonomously interact with the analysis results of CAE pro- grams such as Abaqus, Nastran and ANSYS. Results of static, dynamic, thermal or fatigue analysis and well-established technology including nonlinearities as contact, plasticity and large deformations can be considered during the optimiza- tion. Additionally, the optimization provides the results in suitable formats for an easy transfer into CAD. This allows the designers to use their existing knowledge concerning models

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