This paper introduces a method to simplify a non linear problem in order to use linear finite element analysis. This approach improves calculation time by two orders of magnitude. It is then possible to optimize the geometry of the components even without supercomputers. In this paper the method is applied to a very critical component: the aluminium alloy piston of a modern common rail diesel engine. The method consists in the subdivision of the component, in this case the piston, in several volumes, that have approximately a constant temperature. These volumes are then assembled through congruence constraints. To each volume a proper material is then assigned. It is assumed that material behaviour depends on average temperature, stress magnitude and stress gradient. This assumption is valid since temperatures varies slowly when compared to pressure (load & stress). In fact pressure propagates with the speed of sound. The method is validated by direct comparison with non linear simulation of the same component, the piston, taken as an example. In general, experimental tests have confirmed the cost-effectiveness of this approach.
optimization, simulation, CAD, geometry, FEA
 L. Piancastelli, G. Caligiana, Frizziero Leonardo, S. Marcoppido, “Piston Engine Cooling: an Evergreen Problem”, 3rd CEAS Air&Space Conference – 21st AIDAA Congress – Venice (Italy), 24th-28th October 2011.
 L. Piancastelli, L. Frizziero, E. Morganti, A. Canaparo: “Fuzzy Control System for Aircraft Diesel Engines”, edizioni ETS, Int. Jour. Of Heat and Technology, ISSN 0392-8764, Vol. 30, N.1, 2012
 L. Piancastelli, L. Frizziero, S. Marcoppido, E. Pezzuti, “Methodology to evaluate Aircraft Piston Engine Durability” edizioni ETS, Int. Jour. Of Heat and Technology, ISSN 0392-8764, Vol. 30, N.1, 2012.