Materials selection with several sizing variables taking environmental impact into account

In two recent papers by the authors in Materials and Design it was shown how efficient materials optimisation can be performed in realistic design cases with several sizing (geometrical) variables. In the present paper this analysis is expanded to take environmental impact into account. Two approaches are considered for the materials optimisation. In the first one, the environmental impact is considered as a constraint and the solution in found with the help of a control area diagram (CAD). In the second approach trade-off values for the environmental impact are used. The approaches are applied to a pressure vessel where the geometry is defined by four geometrical variables. Four pressure vessel steels and three aluminium alloys are used in the analysis. Merit indices and merit exponents are systematically used to solve the material optimisation problem. As expected the optimum material is strongly dependent on the chosen target functions and constraints. It is demonstrated that the two approaches for materials optimisation give identical results.