Studies on the solution heat treatment, forming and in-die quenching process in the production of lightweight alloy components
File(s)
Author(s)
Elfakir, Omer
Type
Thesis
Abstract
A novel necking prediction model was developed and verified that could be utilised in finite element (FE) simulations for optimisation of high temperature forming processes parameters, such that a successful component could be formed. The temperature-dependent time-based model combines viscoplastic equations, the Hosford yield criterion and the Marciniak and Kuczynski formulation, and is able to capture the effects of varying temperature, strain rate and strain path on the formability of a material. The results of high temperature uniaxial tension tests and isothermal formability tests on the aluminium alloy AA6082 were used for calibration, although the developed model could be similarly calibrated for alternative aluminium alloys.
The capability of the model, which could also be run independently, was demonstrated by applying it in a simulation of the solution Heat treatment, Forming and in-die Quenching (HFQ) process for a complex-shaped stiffener component in the commercial FE software PAM-STAMP. The component depth at which severe necking would occur was successfully predicted, and was in agreement with the results of the experimental HFQ trials. The model was subsequently used for the blank shape optimisation of a door inner panel component; the final optimised blank shape was formed experimentally, with the resulting component being free of any cracks and incidences of necking.
By decoupling the necking prediction model from the process simulations, significant savings in computational time could be made by selecting only the critical regions in the component where the model would be run. Additionally, the computation could be spread across multiple work stations simultaneously to improve the efficiency of the calculations. The adopted simulation methodology could be expanded further by having multiple independent models that cover other aspects of a forming process such as friction and microstructural evolution.
The capability of the model, which could also be run independently, was demonstrated by applying it in a simulation of the solution Heat treatment, Forming and in-die Quenching (HFQ) process for a complex-shaped stiffener component in the commercial FE software PAM-STAMP. The component depth at which severe necking would occur was successfully predicted, and was in agreement with the results of the experimental HFQ trials. The model was subsequently used for the blank shape optimisation of a door inner panel component; the final optimised blank shape was formed experimentally, with the resulting component being free of any cracks and incidences of necking.
By decoupling the necking prediction model from the process simulations, significant savings in computational time could be made by selecting only the critical regions in the component where the model would be run. Additionally, the computation could be spread across multiple work stations simultaneously to improve the efficiency of the calculations. The adopted simulation methodology could be expanded further by having multiple independent models that cover other aspects of a forming process such as friction and microstructural evolution.
Version
Open Access
Date Issued
2015-10
Date Awarded
2016-03
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Balint, Daniel
Dear, John
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/I038616/1
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)