J. Dias-de-Oliveira

Analysis of Steel Phase Transformations Using a Multiscale Transient Model

Multiphase steels offer impressive mechanical properties. However, their characterization still represents a challenge. In a quenching processes, phenomena such as undesirable strains or residual stress are inevitable and can be the cause for non-admissible final parts. Microstructural phase transformations generally magnify the problem. This fact leads to the need of numerical tools capable of quantifying these residual stresses, due to the non-existence of efficient non-destructive experimental procedure capable of measuring them. In this work, a numerical multiscale transient model, that uses the Asymptotic Expansion Homogenisation (AEH) method combined with finite element method (FEM), is proposed. The implementation of the AEH method is carried out using the commercial program Abaqus, considering an uncoupled and quasi-static transient problem with implicit time integration. Within the homogenisation method, the existence of two distinct scales is assumed, defining a micro and a macroscale. Within the smaller scale, the evolution of a steel periodic microstructure is analysed in detail and an equivalent homogeneous material model is established for macroscopic use. However, the microstructural evolution leads to the need of new equivalent homogeneous models in order to predict the macro response. Consequently, several mechanical, thermomechanical and transient thermal homogenization procedures are carried in order to establish different equivalent homogeneous models.

A model for the effective engagement of all stakeholders in engineering education and its pilot implementation

ABSTRACT Methodologies for engineering learning and teaching (MELT) approach aims to enhance the attractiveness of education through science, technology, engineering and mathematics (STEM) among young people, while promoting awareness of future careers in these areas. To this end, students’ expectations are considered within university programmes, aiming to an increased engagement in STEM careers. To accomplish these goals, a new and integrated approach (MELT) is presented, involving the main stakeholders in both scientific education and society. An education framework is presented, providing guidelines for an improved collaborative approach to STEM education in the future. Results from the pilot implementation of MELT are presented, from a small-scale education parliament prototype. From these initial stage and results, it is seen that there is a need for a proper alignment of expectations from all involved stakeholders, concerning the engineering education towards society’s demands.

Heat Treatments Analysis of Steel Using Coupled Phase Field and Finite Element Methods

Steels are known for their remarkable mechanical properties being extensively used in industry. Furthermore, phase transformations in metals and alloys, particularly in steels, are widely studied due to their importance. The understanding of the microstructure evolution in this type of materials is vital to reproduce the thermomechanical behaviour and to create new materials. To analyse the thermomechanical behaviour of steel during phase transition of steels, a phase field model was coupled with a finite element model in order to simulate the heat treatment and microstructure evolution of austenite to pearlite/ferrite. The thermoelastoplastic constitutive equations for each phase were implemented through a user routine in commercial FE software. This procedure presents a more quantitative understanding of the phase transformation in steels and a deeper comprehension of the mechanical behaviour of these materials when subject to heat treatments.