Surface quality of aluminium extrusion products

Abstract

Dit proefschrift is goedgekeurd door: de promotor: prof.dr.ir. D.J. Schipper de assistent promotor: dr.ir. M.B. de Rooij iv Summary performing split die extrusion experiments, where measurements of the sticking and slipping lengths on the split bearing show that the model is applicable to aluminium extrusion.The second part of the physical model concerns modelling the transfer of material between the bearing-extrudate surfaces and how they eventually detach to form pickup defects. The existing lump growth model is extended and modified to describe the behaviour of aluminium alloys. Further, this physical model is coupled to FEM calculations.Based on the developed physical model, a surface quality predictor has been developed that indicates the degree of surface damage of extrusion products as the number of "detached lumps". Based on this surface quality diagrams have been constructed. The surface quality predictor has been validated by split die extrusion experiments, in which surface defects on product surfaces were counted. The calculation results show good agreement with experiments.A case study is presented in this thesis to give an example of how such a surface quality predictor improves an extrusion process. Detailed procedures for implementing the surface quality predictor and integrating it into the complete designing process have been proposed. Some recommendations regarding industrial practice are given. xviii Table of contentsChapter 9 Conclusions, discussions and recommendations.