Vibro-acoustic optimization using discrete and continuous design variables

The vehicle development process demands quick evaluation of new designs. CAE and CAD tools are essential in order to perform these assessments in a very narrow time frame. New design variants with desired criteria should be quickly created and analysed. Geometry based topology and shape optimization can accelerate such a process when changes in body structure are automatically updated. A FE mesh generation during topology and shape optimization runs should not require any kind of user intervention. The above mentioned requirements are fulfilled by SFE CONCEPT TM. This paper describes the feasibility of a vehicle development process where geometry modifications lead to a reduction of the interior noise of a full-trimmed car model. In order to demonstrate this, a vibro-acoustic optimization is carried out for different types of bead patterns in the BIW. In the body structure development process, SFE CONCEPTTM has become an efficient tool to speed up the workflow. The process for a vibro-acoustic optimization of a full-trimmed car body, includes an automatic parameter-based geometry generation by SFE CONCEPTTM, an acoustic analysis by SFE AKUSMODTM and a new discrete-stochastic optimization algorithm especially adapted to the problem at-hand. The optimization algorithm modifies the topology and shape using standard ASCII interfaces in SFE CONCEPTTM. These interfaces include two different kinds of design variables. The first group of design variables are discrete ones like topology changes. The second group are continuous design variables used in well known shape optimization. The parametrical structure in SFE CONCEPTTM, allows an automatic consideration of both types in an optimization loop. After modifying the geometry, the FE-representation of the car structure will be generated. The FE mesh includes all connector elements such as spot welds, laser seams and adhesives. During the optimization loop the built-in finite element generator creates for all design variants a FE model which fulfils the quality criteria of the FE-Solver. SFE AKUSMODTM provides the data files for an execution of the vibro-acoustic analysis. The steps are closing the holes, generation of the cavity mesh and coupling the cavity mesh and the structure. The FE-solver calculates the SPL at driver’s ear for the objective function for the optimization method and a new value set of design variables is generated for SFE CONCEPTTM . During the iterations this loop will be repeated until the optimization criterions for objective and constraints are fulfilled.     «

The vehicle development process demands quick evaluation of new designs. CAE and CAD tools are essential in order to perform these assessments in a very narrow time frame. New design variants with desired criteria should be quickly created and analysed. Geometry based topology and shape optimization can accelerate such a process when changes in body structure are automatically updated. A FE mesh generation during topology and shape optimization runs should not require any kind of user interventi...     »