Materials selection for optimal environmental impact in mechanical design

Abstract

In engineering design, material selection is carried out in a number of ways. There are many factors affecting material choice for a particular application such as cost, weight and processability, but some of the most important are those of mechanical performance. Many methods exist for optimising parameter values in mechanical design allowing activities such as minimum weight design, design for minimisation of thermal distortion and minimum cost design. These considerations are important but in recent years environmental factors have played an increasing role in the selection of materials and technologies. The inclusion of realistically complex environmental criteria in the design process necessitates the development of methodologies and tools to assist designers. This paper looks at one particular method of material selection in mechanical design: material selection charts by Ashby, and shows how this methodology can be extended to take environmental factors into account. The method for calculating both air and water pollution indices is explained and it is shown how these values may be used to plot charts. By producing material selection charts, along the lines of Ashby's method, which deal with air or water pollution, mechanical design for optimal environmental impact may be structured and accelerated. The limitations of the charts presented in this paper are discussed.