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Incremental sheet forming has been proposed as a flexible manufacturing technique to process thermoplastic resins characterized by a glassy state at room temperature. Specifically, poly(methyl methacrylate) (PMMA) sheets were formed. A controlled room was designed, and the sheets were heated, before starting the forming phase, to a temperature above the PMMA glass transition, but avoiding onset of internal stresses that may lead to significant material springback at elevated temperature. Therefore, the process parameters, such as forming temperature and punch speed rate, have to be kept in well-defined ranges to be able to optimize the forming process of thermoplastic components by ISF. Furthermore, different sheet thicknesses were formed. Indeed, this size affects the flexural strength of the processed polymer as confirmed by reported tests. Experiments were planned out for the aim to take into account various process variables, i.e. spindle speed, step depth, punch diameter and feed rate. A plan based on a design of experiments (DoE) method was applied for a robust analysis. Macroscale observations were carried out to evaluate the product soundness, highlighting influences of the monitored process variables, on the process temperature and on the accuracy error of the formed parts. Furthermore, microscopic analyses evidenced the integrity grade of the surface on the side in contact with the punch for various combinations of process parameters. The results proved the process feasibility also for thermoplastics, which need to be heated before their forming phase.

Arc welding processes represent an important category of fusion welding techniques. They are characterised by the use of an electric arc to create heat to melt and join metals. Submerged arc welding belongs to this process category. Its peculiarities are mainly related to the employment of a continuously fed electrode and of a powdered flux to cover the arc providing electrical conduction between electrode and metals to be connected and, at the same time, generating protective gas and slag shields. Current (I), voltage (V), and welding speed (v) are the main process variables, properly set, to guarantee the specific heat (SH) required to achieve sound weld beads. In this research, finite element models were built looking at the macrographs extracted by experimental tests performed in two steps in order to obtain the real area of each pass and setting different welding conditions. Different combinations of I, V, and v were proposed providing, however, a fixed SH to the welding zone according to the required industrial standards. Specifically, tests were executed increasing the ratio V to v (for a constant I) and the ratio I to v (for a constant V) and with a different combination of V and I maintaining constant their product (for a constant v). The influence of the investigated variables’ combination on the weld pool in terms of depth and width was discussed. Finally, the validated numerical models were employed to highlight precisely residual stresses and displacements trend on cross-sectioned weld beads connecting the shown tendencies to the investigated process conditions.

Aluminium sheets (EN AW-1050) have been worked by a friction stir process to allow forming pins to be used as joining elements, in a clinching-type solution, for assembling multi-material components. Two lines of pins of diameter 4 mm and 6 mm, respectively, have been formed experimentally at various process conditions. A process control, using the force-trend distribution, has been pursued for a full comprehension of the forming steps. The strength of the pins has been tested aiming at understanding the influence of all the analysed process parameters thoroughly. Additionally, a numerical model has been developed and compared with the experimental evidence. This model has been employed to investigate the material flow during the pin formation. The results demonstrate the feasibility of this innovative method and highlight the significance of the main parameters that have to be set carefully for an optimised implementation of friction stir forming based joining technique. Graphical abstract

Improving the capabilities of online condition monitoring systems, able to detect arising of catastrophic wear on cutting tools, has been an important target to be pursued for the metal cutting industry. Currently, different systems have been proposed, moved by the rising need of part quality improvements and production cost control. Despite this, cutter wear development, being related to several process variables and conditions, is still really difficult to be predicted accurately. This paper presents a detection wear method based on the time-domain analysis of vibro-acoustic signals. Specifically, cutter wear monitoring, using sound signals of a milling process, was performed at a laboratory level in a well-isolated working room. Sound signals were recorded at fixed main machining parameters, i.e., cutting speed, feed rate and depth of cut. The tests were carried out starting with a new set of inserts with significant wear conditions for the investigated process configuration. Results showed a consistent overlapping between the beginning of the catastrophic wear and an evident increment in the trend of the root mean square of the monitored acoustic signal, showing the potential of the methodology in detecting a suitable time to stop the milling process and to change the worn-out cutters.

Cranial reconstructions are essential for restoring both function and aesthetics in patients with craniofacial deformities or traumatic injuries. Titanium prostheses have gained popularity due to their biocompatibility, strength, and corrosion resistance. The use of Superplastic Forming (SPF) and Single Point Incremental Forming (SPIF) techniques to create titanium prostheses, specifically designed for cranial reconstructions was investigated in an ovine model through microtomographic and histomorphometric analyses. The results obtained from the explanted specimens revealed significant variations in bone volume, trabecular thickness, spacing, and number across different regions of interest (VOIs or ROIs). Those regions next to the center of the cranial defect exhibited the most immature bone, characterized by higher porosity, decreased trabecular thickness, and wider trabecular spacing. Dynamic histomorphometry demonstrated differences in the mineralizing surface to bone surface ratio (MS/BS) and mineral apposition rate (MAR) depending on the timing of fluorochrome administration. A layer of connective tissue separated the prosthesis and the bone tissue. Overall, the study provided validation for the use of cranial prostheses made using SPF and SPIF techniques, offering insights into the processes of bone formation and remodeling in the implanted ovine model.

Welding processes are widely used technologies in the industrial context for creating permanent connections between mechanical components. This popularity is due to their versatility, which arises from the numerous available process variants and the multiple advantages they offer compared to other joining techniques. In the manufacturing context, where devices often operate in extreme conditions, the quality of welds becomes a critical factor in ensuring the safety and reliability of the manufactured products. Furthermore, a sound joint requires careful compliance with the increasingly stringent design specifications demanded by customers who require industry-standard conformity in order to achieve defect-free, robust, and durable welds. To address these needs and to define the optimal roadmap for the investigated process condition, an experimental investigation was conducted on the submerged arc welding process. The experimental trials involved butt joints of ASTM A516 Gr.70 carbon steel plates with different thicknesses in a flat position, utilizing a U-shaped chamfer and a multi-pass welding technique. For each weldment, the effects of the main process parameters on the qualitative characteristics of the manufactured products were evaluated from a metallurgical perspective. This evaluation included an in-depth metallographic analysis of the heat-affected zone of the carbon steel joint and involved both the measurement of the dimensions of these areas as well as the amount of ferrite and pearlite that resulted as the phases observed in the final microstructure of the steel joint following its solidification. Furthermore, the joint quality was assessed with regard to mechanical strength through hardness measurements. By analysing the experimental data, the paper provides a valuable contribution for increasing the productivity of the investigated welding process, while simultaneously meeting the specified industrial quality requirements for the products made of medium-thickness carbon steels.

Polymeric matrix composites (PMCs) have gained increasing relevance in different industrial applications and their employment results to be a necessity in the production of lightweight structures. The manufacturing solutions, which allow to properly shape PMC panels, need molds for shaping the material reducing the process flexibility. In this context, the single point incremental forming (SPIF) could be a valuable process solution if properly customized to the PMC properties. Herein, a possible process variant is introduced and its capability in forming long fiber–reinforced thermoplastics was evaluated. To achieve this aim, a numerical model was implemented focusing the attention, first, on the material properties that have to be considered for a proper model construction. The performed numerical simulations showed the applicability of SPIF to shape PMC sheets. Furthermore, the executed simulations pointed out the influences of some variables on the quality of the formed parts showing possible arising of defects, such as wrinkling and rippled surfaces, at different process conditions and providing a first proof of concept of the proposed working solution.

The production of prostheses is still not completely optimized, especially for those districts where both functional and aesthetic requirements have to be combined with the urgency of intervention. The prostheses manufactured by machining using CAD/CAM techniques represent the conventional way to obtain a \"custom-made\" part. However, the above-mentioned solutions are penalized by the too long manufacturing time. This limit can be overcome by using an innovative metal-forming process, i.e. the Incremental Sheet Forming (ISF), which also allows to obtain complex patient-specific geometries even if characterized by a lower precision compared to the conventional process. In this paper, alternative approaches to manufacture a skull prosthesis (i.e. conventional milling and ISF) are compared from technological and economical points of view.

Background Host inflammation contributes to determine whether SARS-CoV-2 infection causes mild or life-threatening disease. Tools are needed for early risk assessment. Methods We studied in 111 COVID-19 patients prospectively followed at a single reference Hospital fifty-three potential biomarkers including alarmins, cytokines, adipocytokines and growth factors, humoral innate immune and neuroendocrine molecules and regulators of iron metabolism. Biomarkers at hospital admission together with age, degree of hypoxia, neutrophil to lymphocyte ratio (NLR), lactate dehydrogenase (LDH), C-reactive protein (CRP) and creatinine were analysed within a data-driven approach to classify patients with respect to survival and ICU outcomes. Classification and regression tree (CART) models were used to identify prognostic biomarkers. Results Among the fifty-three potential biomarkers, the classification tree analysis selected CXCL10 at hospital admission, in combination with NLR and time from onset, as the best predictor of ICU transfer (AUC [95% CI] = 0.8374 [0.6233–0.8435]), while it was selected alone to predict death (AUC [95% CI] = 0.7334 [0.7547–0.9201]). CXCL10 concentration abated in COVID-19 survivors after healing and discharge from the hospital. Conclusions CXCL10 results from a data-driven analysis, that accounts for presence of confounding factors, as the most robust predictive biomarker of patient outcome in COVID-19. Graphic abstract