Residual Stress in Friction Stir Welding and Laser-Assisted Friction Stir Welding by Numerical Simulation and Experiments

The friction stir welding (FSW) has become an important welding technique to join materials that are difficult to weld by traditional fusion welding technology. In this technique, the material is not led to fusion, and the joint is the result of the rotation and movement along the welding line of the tool that causes softening of material due to frictional heat and the stirring of the same. In FSW, the temperature does not reach the fusion value of the materials, and this helps to decrease the residual stress values. However, due to the higher force involved in the weld and, thus, the rigid clamping used, the residual stresses are not low in general in this technique. As the presence of high residual stress values influences the post-weld mechanical properties, e.g. fatigue properties, it is important to investigate the residual stress distribution in the FSW welds. In this chapter, two numerical models that predict temperatures and residual stresses in friction stir welding and laser-assisted friction stir welding will be described. Experimental measurements of temperatures and residual stress will be carried out to validate the prediction of the models

Application of Optical Methods to Electronic Component Stress Analysis

Increasing electronic component reliability is, nowadays, a hot topic both in most advanced applications as well as in electronic devices of common use in everyday life. In fact, requirements in terms of miniaturization of electronics components introduce issues connected with heat dissipation management. Materials, packaging, heat dissipator, and even positioning of the component on the board should be optimized in order to reduce thermal stresses generated in the components, which are one of the most important failure mechanisms of electronics. Thermal stress evaluation is, however, a difficult task due to the size of the elements under testing and to the necessity of measuring small amount of strains. At the same time, any contact with the object under measurement should be avoided not to alter heat capacity of the component itself. In this work, some results of experimental stress analysis gathered using electronic speckle pattern interferometry will be described; it will be pointed out how this approach allows to put in evidence inhomogeneous stress fields undergone by the electronic components and how it is possible to highlight the presence of bad functioning and defects

Electrophysiological study of visual pathways in nevoid basal cell carcinoma syndrome patients

Introduction: Gorlin-Goltz syndrome (GGS) also known as nevoid basal cell carcinoma syndrome (NBCCS) is a complex rare genetic disorder characterized by a wide range of clinical and radiological manifestations. Ophthalmological alterations have always been reported, but no study on the eventual pattern visual evoked potentials (pVEPs) abnormalities has yet been published.Purpose: The purpose of the study was to evaluate the functionality of the optic pathways in a group of NBCCS patients through pattern reversal VEPs, after a thorough exclusion of subjects with preexisting ocular and optic pathways pathologies.Methods: Nineteen NBCCS patients (31 eyes) and 20 healthy controls (40 eyes) have been recruited for this study. All subjects underwent an evaluation of the functionality of the optic pathways through pVEPs with small (120'), medium (60'), and large (15') check size stimulation.Results: NBCCS patients showed a statistically significant alteration in the transmission of the macular pathway function when compared to controls. PVEPs analysis confirmed a reduced amplitude and an increased latency of the P100 component, suggesting an involvement of the visual pathway even in the absence of ocular clinical manifestations.Conclusion: Visual pathways may have been affected both by a subclinical myelination deficit, determined directly by the genetic alteration, as well as by neurological abnormalities typical of this syndrome. Further studies are warranted

New professional roles and patient satisfaction : evidence from a European survey along three clinical pathways

Project is funded by the European Commission, Grant Agreement no: 305467.Peer reviewedPostprin

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy

Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force

Mechanical Behaviour of ABS-Fused Filament Fabrication Compounds under Impact Tensile Loadings

In the Fused Filament Fabrication (FFF) process, the part is built as a layer-by-layer deposition of a feedstock filament material. The continuous improvements of the FFF have changed the main purpose of this technique from rapid prototyping to a rapid manufacturing method. Then, it is fundamental to determine the material properties of FFF parts as a function of the service load. The impact loads and, in particular, a high strain rates tensile impact can be a critical issue in FFF part and, in general, for plastic materials. The aim of the present work is to characterise the mechanical behaviour of FFF parts under tensile impact loads. To this purpose, three different orientations (i.e., 0°, 45° and 90°) both single- and multilayer specimens, have been printed. Finally, the influence of the impact speed on the mechanical behaviour has also been tested under three different values of speed (3.78 m/s, 3.02 m/s and 2.67 m/s). The results show that the FFF parts are influenced by the raster orientation, confirming the orthotropic behaviour also under dynamic loads, while the variation of impact speed, on peak force and absorbed energy, is limited