Automated Design of Major Load Carrying Members and Selection of Optimum Stiffness Properties to Meet Specific Performance Targets

The objective of the present paper, is to present the methodology and results of an ongoing work related to automated sizing of beam cross sections of major load carrying members and selection of optimum joint stiffness properties of an automobile to meet static bending and torsion, first bending and torsion frequency targets with minimum weight.

In an automobile body design, initial selection of cross sectional properties of major load carrying members and selection of optimum joint stiffness properties will essentially define its characteristic behavior. Past experience shows that any further design modifications of the panels in terms of additional stiffeners, upgaging etc., will not appreciably improve the characteristic behavior in terms of tactile and acoustic response. The cost effectiveness in terms of performance and design changes, results mainly from the changes to the major load carrying members and optimum joint stiffness characteristics.

To this extent this paper presents a methodology for automated sizing of beam cross sections of major load carrying members and selection of optimum joint stiffness properties for a given topology of an automobile. The computer code LOHITSA/AUTOSIZE is being developed for this purpose. It uses simplified mathematical model with primarily beam and spring elements. Existing MSC/NASTRAN models can also be used directly. Constraints are performance targets, cross section properties, joint stiffness and manufacturability.