Development of an expert system for materials selection in mechanical design

Abstract

Materials selection is an important issue in the design and manufacture of any component. With the proliferation of engineering materials, diminishing natural resources, and interdependence of materials and their processing, there is need to develop a procedure that will aid engineers in the selection of materials. A number of commercial selection tools for materials have been developed. However, most of these tools are expensive and thus not easily accessible to local design engineers. Furthermore, the materials specifications in their databases are different from those in Kenya. This makes it necessary for the databases to be customized by adding the materials used in Kenya or simply indicating equivalent specifications where that is possible.

The objective of this study was to develop a material selection procedure and implement it as an information processing routine on digital computer. A case study was undertaken that involved selection of a material in the design of a rope drum for a manual winch. The critical characteristics of the rope drum material were identified to be buckling, strength, contact pressure, wear rate and cost. The material properties that provide for these characteristics were then used to formulate indices that were used to rank several materials based on how well they scored in those characteristics. The formulation of the indices was done such that the most suitable material for each characteristic ranked highest. An overall index was obtained by summing the values of the indices for all the characteristics for each material. Using this selection criterion, AISI 1055 cold rolled