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The accurate prediction of part deformation due to solidification in automotive formed parts is important to help achieve an efficient production. Forming processes are those where a molten preform is deformed to take the shape of a mould cavity and subsequently solidified. Tolerance issues are critical in automotive applications and therefore part deformation due to solidification needs to be controlled and optimized accordingly. Formed parts can have a wide range of deformations according to the conditions of solidification. Both a small displacement and a large displacement formulation are developed for prediction of part deformation due to solidification. Experimental results obtained on a simple as well as complex automotive part are compared to determine whether the small displacement theory or the more complex approach is more appropriate.

A numerical simulation model for the prediction of fuel hydrocarbon permeation is presented in this work. The barrier layer thickness optimization for thermoplastic multilayer fuel tanks is also considered. The diffusion model is based on the continuum approach with steady-state permeation regime across the multilayer polymeric wall. The hydrocarbon flux through the multilayer wall is determined by assuming continuity in vapor pressure at the polymer-polymer interface. Since the pinch-off zone is known to be the major source of emission per unit area, a method has been developed to automatically detect this zone at the end of extrusion blow molding process. After then, an improvement to the diffusion model has been proposed in order to evaluate adequately the hydrocarbon permeation through this specific area. Finally, a gradient-based algorithm is applied to optimize the barrier layer thickness to satisfy the total hydrocarbon fuel emission constraint for a plastic fuel tank (PFT).

Blow moulding is one of the most important polymer processing method for producing plastic automotive parts. Yet, there are still several problems that affect the overall success of forming these parts. Among them, are thermally induced stresses, relevant shrinkage and part warpage caused by inappropriate solidification conditions. This work presents a finite element model that allows for predicting residual stresses and subsequent deformations that arise during the cooling stage of finished parts. It is expected that the virtual presence of the flash zone has an influence on the development of residual stresses in the numerical model. Deflashing is usually performed immediately after part removal from the mould, therefore, the numerical model is adapted to take this into account. Numerical results obtained with and without flash for a simple part, as well as a complex automotive part, are compared to determine accuracy and limitations of the model.