A Fuzzy Material Selection System for Mechanical Design

Abstract

This paper concentrated on two types of material-related reasoning that occurs in engineering design: selection and substitution. Selection is based on criteria set out by the designer and is often associated with the process of designing new artifacts from scratch. Substitution, on the other hand, is done when new designs are created by adapting and re-using parts of previous designs. This involves re-evaluating the reasons for a particular material that was used in the base design, and determining whether the same, or new criteria are relevant in the target design. Once the new criteria are established, appropriate materials are selected and substituted. The substitution step, hence, subsumes the selection task. We present a material selection/substitution system that is used as part of a larger case-based design environment. The material selection system helps the designer adapt a previous designs by suggesting material substitutions that better suit the target application. The system is intended to provide support, right from the conceptual to the detailed stages of design, and can reason about material properties expressed in both numerical and qualitative terms. The system relies on the material selection charts developed by Prof. Ashby of Cambridge University. To enable qualitative reasoning about the charts, we have developed an encoding based on fuzzy set theory. This allows access of materials using specifications expressed in terms of fuzzy orders of magnitude.