Harold Thomas

PROGRESS IN TOPOLOGY OPTIMIZATION WITH MANUFACTURING CONSTRAINTS

Topology optimization has been show n to be an extremely powerful tool in generating efficient design concepts in the early stage of a design process. Unfortunately, very often designs suggested by topology optimization turn out to be infeasible for certain manufacturing process. At such occ asions, it is often very difficult, if not impossible, to transform a design proposal to a manufacturable design. In this paper, design requirements for casting and extrusion production are addressed for topology optimization.

Crashworthiness design using structural optimization

Consideration of the crashworthiness of a design requires nonlinear structural analysis. Analysis codes for such problems are based on explicit integration schemes. Parameter changes are derived from the results of the analysis to improve the design in order to meet the requirements of regulations and design goals. Today, the usual approach is a trial-and-error search that is very expensive with respect to labor costs. Optimization methods can be used to automate the search for the optimum design. Closed loop software for the optimization of structures with nonlinear behavior such as known for linear statics is not available currently. Usually addons to the non-linear codes based on response surface methods or finite difference sensitivity analysis are used. The paper discusses the incorporation of optimization into the crashworthiness design of automotive structures. A very efficient response surface method is presented. Some examples show practical applications of structural optimization in the development of motor vehicles. The use of structural optimization reduces the manual effort to search for an optimal design considerably.

Global optimization using accurate approximations in design synthesis

The design variable space of a design synthesis problem may contain multiple local optima. In the approximation concepts approach to design synthesis, the design objective and constraint functions are approximated in order to reduce the overall cost. If the approximations accurately capture the actural behavior of the objective function and constraints, then the approximate design variable space may also contain local optima. In this work, a multistart optimization algorithm is used to search for the global optimum of the actual design using just a few design cycles. Example problems are presented to illustrate the methodology set forth.

Structural -Acoustic Optimization using CMS Super Elements

It is very important for automobile manufacturers to design automobiles with low levels of noise in the passenger compartment. Noise is generated from the tires, engine, transmission, and exhaust system and transmitted through the body structure to the air in the passenger compartment. Coupled structure -acoustic frequency response analysis is used to dete rmine the sound levels at the driver’s and passenger’s ears at different driving speeds and engine speeds. The passenger compartment noise can be reduced by correct sizing of structural components such as suspension bushings and dampers, motor mounts, exh aust system hangers, etc., as well as by applying sound absorbing materials to the metal structures of the automobile. In addition, the structural design itself can be modified to change vibration load paths to reduce the noise levels. These design decis ions are usually made by trial and error. In this work we look at applying optimization design concepts to the reduction of the noise level in the passenger cabin. Topology Optimization as well as sizing and material optimization can be used to reduce th e sound levels to specified levels at different frequencies. A single coupled structure -fluid frequency response analysis of a typical automobile finite element model containing over 10 million DOF can take many hours on a modern computer. The significan t new aspect of this work is the use of a sub structuring technique to reduce the optimization run time. With these techniques, the non design portion of the structure does not have to be reanalyzed during the design iterations. Substructuring is perform ed to create a combined structure -fluid (air) Super Element using the Component Mode Synthesis (CMS) method. The use of these Super Elements can reduce the run times from hours to minutes.

Automatic Integration of Topology and Shape Optimization

In this paper, an approach for the automatic integration of topology and shape optimization is proposed with the goals of increasing the degree of automation and therefore increasing the efficiency in engineering development cycles. A numerical example of engine bracket is illustrated as a typical application. Address the integration of topology and shape optimization to provide a full picture about the geometric representation of mechanical products.