Abstract
The continuous research for progressively lighter components moves the attention on the massive adoption of Al alloys. The achievement of such an ambitious goal passes through the definition of innovative manufacturing methodologies able to overcome some of the most hindering limitation of Al alloys, i.e. their poor formability at room temperature. A viable approach is based on the modification of the blank properties through a local heat treatment (to achieve an optimized spatial distribution of ductility/strength), so that the subsequent forming operation can be carried out at room temperature. The implementation of such approach relies on finite element simulations, where the use of a proper constitutive material model plays a fundamental role. In the present work an innovative methodology, already proposed by the authors in a previous research, is again adopted to enrich the characterization of a strain-hardenable Al alloy (AA5754), initially purchased in a pre-strained condition (H32), and locally annealed by means of a laser treatment: in particular, Thanks to the adoption of the DIC, the investigation of the anisotropy showed a strict correlation between the value of the Lankford parameter and the material condition reached at the end of the local treatment. The experimental data were fitted by a sigmoidal function and implemented in a modified Hill plasticity model for the simulation of the tensile test of a locally treated dogbone specimen, showing a good accordance with the experimental results.
Highlights
IntroductionThe environmental impact of the transportation sector, worsened by the development of the bigger urban centers, has been considered one of the main issues to be tackled over the last decade: different normative frameworks have been purposely defined in order to reduce the harmful emissions and keep the greenhouse effect under control [1,2]
The environmental impact of the transportation sector, worsened by the development of the bigger urban centers, has been considered one of the main issues to be tackled over the last decade: different normative frameworks have been purposely defined in order to reduce the harmful emissions and keep the greenhouse effect under control [1,2].Among the several solutions, the reduction of the vehicles’ masses has been indicated as the most promising one to address the mentioned problem, which can be achieved by replacing the “heavier” components with lighter structures made of Magnesium (Mg) or Aluminium (Al) alloys
The reduction of the vehicles’ masses has been indicated as the most promising one to address the mentioned problem, which can be achieved by replacing the “heavier” components with lighter structures made of Magnesium (Mg) or Aluminium (Al) alloys
Summary
The environmental impact of the transportation sector, worsened by the development of the bigger urban centers, has been considered one of the main issues to be tackled over the last decade: different normative frameworks have been purposely defined in order to reduce the harmful emissions and keep the greenhouse effect under control [1,2]. In the light of this scenario, the scientific research has put lots of effort to overcome such a limitation: the adoption of an increased working temperature can both improve the formability [3,4] and reduce the springback phenomena [5]; the adoption of a flexible medium for deforming the material represents another viable solution [6], which can be efficiently combined with the warm forming approach [7]; in the last years, a new methodology has been proposed, mainly based on splitting the process into two separate moments [8]: at first the blank initial properties are modified by short-term local heat treatment (a favorable distribution of strength-ductility can be obtained according to the component to be manufactured) so that the subsequent forming operations can be carried out at room temperature. As a follow up of the proposed methodology, the attention has been focused on the anisotropy investigation, aiming at evaluating how the normal anisotropy of locally heat-treated blanks is dependent to the percentage of annealing achieved
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