Immersive training weeks in doctoral education

Ph.D. training worldwide, including Doctoral education in Marketing or Engineering fields, has been in trouble for some time. These last turbulent times (pandemic, energy, inflation, and war crises) have only increased the problems previously reported by the 3rd cycle students and early career researchers, including chronic lack of support and poor-quality supervision, with senior researchers rarely trained in mentorship. It is also reported that Ph.D. candidates are inadequately prepared for the cross-disciplinary working and large teams that characterize cutting-edge science today. In the last two decades, opposite decisions took place in Europe concerning the curricula of Doctoral programs. In the 2010s, a large number of classes was added to the Ph.D.s, contributing to almost residual time for thesis research in the first year of the programs. However, ten years later, an abrupt change took place and almost all classes were removed from the Ph.D. curricula, creating a void in (hard and soft skills) training and leaving all the responsibility of training to the supervisor. Ph.D. students reported guidance and isolation issues in the first year. Moreover, today’s little Ph.D. training is fully dedicated to the obtention of their Ph.D. and not to their role in society after the Ph.D. defense. This work discusses a new approach to doctoral education which started first at a professional doctorate implemented at University of Aveiro, Portugal, where few classes take place. This approach considers a novel Ph.D. training, both hard and soft skills development, through special intensive weeks, called Immersive Weeks. In these, distributed during the first year, Ph.D. students exclusively participate in several workshops, acquiring the tools for accomplishing both a successful Ph.D. and a future job. Pilots of this approach took place at the University of Aveiro with large success, while some improvement suggestions have also been pointed out by students.publishe

Integrated Design in Welding and Incremental Forming: Material Model Calibration for Friction Stir Welded Blanks

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Incremental forming of friction-stir welded aluminium blanks: an integrated approach

This study deals with an experimental investigation of the influence of friction stir welding parameters on the subsequent formability during incremental forming of aluminium alloy 6082-T6 blanks. Five welding conditions are considered, based on different combinations of rotational speed and feed rate. Truncated cones are chosen as benchmarks for single point incremental forming and tested up to their rupture limits. Formability is inferred measuring the cone height values, together with strain distributions, as recorded on the outer surface. The results clearly highlight the detrimental influence of a high feed rate of 100−1at the friction stir welding stage, leading to a significantly reduced formability in incremental forming. Regarding other parameters, formability levels are similar to those of the unwelded blanks. Local mechanical properties are investigated by means of hardness measurements, to assess the evolution through the weld, and conventional tensile tests. Digital image correlation is used to properly capture the highly heterogeneous strain field and as a result, to estimate the local yield stress levels. The stress mismatch between the heat affected zone and the nugget zone presents the same trend as the formability. Finally, scanning electron microscopy observations of the fractured samples in tension highlight more differences between the base material and the welded specimen than between the different welded ones. This study therefore emphasises the importance and relevance of an integrated mechanical design approach, considering both welding and forming processes as a whole

A finite element approach to the integrated modelling of the incremental forming of friction stir welded sheets

Thin sheet components are increasingly used in several advanced industries, such as aerospace and automotive. In these sectors, improved mechanical and surface properties are highly demanded meeting, in several cases, also weight and aesthetical requirements. The industrial routes typically involved in the manufacturing of this kind of components are based on the combination of joining, forming and cutting technologies, whereas efficient production strategies are planned adopting modelling and simulations based on an integrated approach. The present work deals with the development of an integrated numerical model able to simulate the manufacturing route for formed thin sheets, rolled, welded by friction stir welding (FSW) technology and finally shaped by means of a single point incremental forming (SPIF) process. In concept, the approach is based on the link between two submodels simulating the two consecutive processes. The first submodel, taking as input the geometry and the mechanical properties of the anisotropic rolled aluminum foil, simulates in the ABAQUS environment, the FSW process. Tool geometry and path, rotational velocity, advancing speed, and other material parameters are defined as input values, providing, as output, the mechanical properties of the welded sheet, the affected zones, and the residual stress-strain fields. This output feeds the SPIF sub-model that evaluates the deformation of the sheet according to a defined process planning, allowing for the simulation of the entire manufacturing chain

Optimal low-order fully integrated solid-shell elements

This paper presents three optimal low-order fully integrated geometrically nonlinear solid-shell elements based on the enhanced assumed strain (EAS) method and the assumed natural strain method for different types of structural analyses, e.g. analysis of thin homogeneous isotropic and multilayer anisotropic composite shell-like structures and the analysis of (near) incompressible materials. The proposed solid-shell elements possess eight nodes with only displacement degrees of freedom and a few internal EAS parameters. Due to the 3D geometric description of the proposed elements, 3D constitutive laws can directly be employed in these formulations. The present formulations are based on the well-known Fraeijs de Veubeke–Hu–Washizu multifield variational principle. In terms of accuracy as well as efficiency point of view, the choice of the optimal EAS parameters plays a very critical role in the EAS method, therefore a systematic numerical study has been carried out to find out the optimal EAS parameters to alleviate different locking phenomena for the proposed solid-shell formulations. To assess the accuracy of the proposed solid-shell elements, a variety of popular numerical benchmark examples related to element convergence, mesh distortions, element aspect ratios and different locking phenomena are investigated and the results are compared with the well-known solid-shell formulations available in the literature. The results of our numerical assessment show that the proposed solid-shell formulations provide very accurate results,without showing any numerical problems, for a variety of geometrically linear and nonlinear structural problems

Development of a one point quadrature EAS solid-shell element

A correct reproduction of thickness effect can be accurately described by the use of three-dimensional solid elements. In addition to convenient formulation for constitutive law, solid element provides a straightforward extension to geometrically non-linear problems, particularly in the presence of large rotations, since only translational degrees of freedom are involved. Also, compared with shell elements, it is valid to consider double-sided contact because of real physical nodes on top and bottom surfaces without any further modification. However, for low order elements, as thickness/length ratio value tends to zero, the transverse shear-locking phenomenon becomes more evident. Also, plasticity leads to isochoric deformation, which is the main source of the volumetric locking phenomenon. Concerning bending dominant problems, it is difficult to use a single layer of solid elements due to the limitation of integration points along thickness direction. Multi-layered solid element increases the CPU time dramatically. In order to overcome these drawbacks, a new single layer solid-shell element is developed based on a one-point quadrature scheme, but allowing multiple integration points along thickness. A physical stabilization scheme, based on convective coordinate system, is used to control hourglass modes efficiently. To avoid thickness and volumetric locking behaviors, the formulation applies Simo and Rifai's Enhanced Assumed Strain method. The background theory for this element and numerical simulations for validation purposes are presented. Assessments show that the present formulation is efficient for linear and nonlinear shell applications