Experimental analysis and modeling of the recrystallization behaviour of a AA6060 extruded profile

The microstructure of Al-Mg-Si alloys is gaining nowadays an increasing industrial interest because it influences the strength, crash, corrosion and esthetic properties of the extruded profiles. In order to investigate and predict the recrystallization behaviour in the extrusion of 6XXX aluminum alloys, experimental and numerical activities are still needed. In this work, the extrusion of an industrial-scale AA6060 aluminum alloy hollow profile was carried out. An innovative recrystallization model was developed and optimized by comparing the microstructural data experimentally acquired with the outputs of the simulation performed using the Finite Element commercial code Qform Extrusion. A good correlation between numerical prediction and experimental data was found, thus proving the reliability of the proposed AA6060 recrystallization model

Advancements in extrusion and drawing: a review of the contributes by the ESAFORM community

The present review paper would celebrate the 25 years anniversary of the ESAFORM association by summarizing the studies performed by the delegates of the ESAFORM conference series within mini-symposium “Extrusion and Drawing” and of the papers published in the International Journal of Material Forming in the same fields. The 160 analyzed papers have been divided in four main categories corresponding to the paper main chapters (Hot Metal Extrusion, Cold Metal Extrusion, Polymer Extrusion and Drawing) then further divided in sub-chapters in order to group them in more specific research subjects. The aim of this review paper is then to provide to the reader a complete overview of the investigated topics and of the research trends over the years within the ESAFORM associate researchers

Investigation on the topological optimization of cooling channels for extrusion dies

During the extrusion process, high temperatures are generated, due to friction and deformation works, potentially leading to profile and die defects. Among the suggested solutions aimed at controlling the thermal field of the process, the most accredited one involves the manufacturing of cooling channels at the mating face between the die and a third plate. Despite the proven efficiency of well-designed channels, the main drawback lies in the managing of the many variables involved that strongly affect the cooling efficiency and balancing. In this frame, aim of the work is to investigate the applicability of the topological optimization tool, proposed by COMSOL Multiphysics software, for the design of cooling channels in extrusion dies. To validate the tool, an industrial case study has been selected and results compared between not optimized and optimized cooling solutions

Effects of Ti6Al4V mechanical and thermal surface modification on the adhesion of a chitosan-bioactive glass coating

Biomedical implants interact with human tissues introducing significant perturbation into the body. Implant surfaces can be then functionalized enabling better biocompatibility. At the same time, the additional use of a coating provides further functions such as corrosion protection, osteointegration, and drug delivery. In this context, a composite made of chitosan and bioactive glass nanoparticles has been used for coating Ti6Al4V alloy samples processed beforehand using different processes, i.e., polishing, milling, grit blasting, and electrical discharge machining. Experiments have been carried out to correlate substrate surface conditions and coating effectiveness in terms of scratch resistance with the final aim to obtain suitable guidelines to improve substrate-coating performances

Investigation of the skin contamination predictability by means of QForm UK extrusion code

The paper presents an innovative approach implemented in QForm UK Extrusion FEM software to analyse one of the core defects encountered in profile extrusion known as billet skin defect. The validation of the algorithm has been performed based on a number of experimental case studies taken from the literature [1,2]. Additionally, the sensitivity of the accuracy of the results to the variation in initial parameters has been analysed for both types of profile shapes: solid and hollow. Based on this, practical recommendations have been formalised for the successful industrial use of the presented algorithm

Wetting Characteristics of Laser-Ablated Hierarchical Textures Replicated by Micro Injection Molding

Texturing can be used to functionalize the surface of plastic parts and, in particular, to modify the interaction with fluids. Wetting functionalization can be used for microfluidics, medical devices, scaffolds, and more. In this research, hierarchical textures were generated on steel mold inserts using femtosecond laser ablation to transfer on plastic parts surface via injection molding. Different textures were designed to study the effects of various hierarchical geometries on the wetting behavior. The textures are designed to create wetting functionalization while avoiding high aspect ratio features, which are complex to replicate and difficult to manufacture at scale. Nano-scale ripples were generated over the micro-scale texture by creating laser-induced periodic surface structures. The textured molds were then replicated by micro-injection molding using polypropylene and poly(methyl methacrylate). The static wetting behavior was investigated on steel inserts and molded parts and compared to the theoretical values obtained from the Cassie-Baxter and Wenzel models. The experimental results showed correlations between texture design, injection molding replication, and wetting properties. The wetting behavior on the polypropylene parts followed the Cassie-Baxter model, while for PMMA, a composite wetting state of Cassie-Baxter and Wenzel was observed

Tailoring surface properties, biocompatibility and corrosion behavior of stainless steel by laser induced periodic surface treatment towards developing biomimetic stents

Laser-Induced Periodic Surface Structures (LIPSS) holds great potential for regenerative biomedicine. Creating highly precise LIPSS enables to generate biomimetic implant surfaces with improved properties. The present study focuses on the fabrication and investigation of laser-treated stainless steel samples with applied linear LIPSS patterns with grooves made by means of a picosecond laser system using wavelengths of 1064 nm and 532 nm. To investigate properties of the laser-treated surfaces and to understand the basics of cell-surface interactions between the LIPSS and human Umbilical Cord Mesenchymal Stem Cells (UCMSC), flat stainless steel samples with various applied nanopatterns were used. Such LIPSSs demonstrated higher surface roughness, good biocompatibility, lower wettability and higher corrosion resistance compared to the untreated (polished) spec-imens. The surface roughness of laser-treated samples was in microscale that enabled adhesion and migration of endothelial cells, thus increasing the likelihood for endothelialisation. This thereby could reduce the chances for the development of Late Stent Thrombosis (LST) and In-Stent Restenosis (ISR). Furthermore, laser textured surfaces demonstrated an environment supportive for cell attachment, proliferation and alignment with the nanogroves. Therefore, application of the biomimetic nanopatterns could help to overcome frequent post-surgery complications after the stent implantation

School refusal behavior. role of personality styles, social functioning, and psychiatric symptoms in a sample of adolescent help-seekers

Objective: School refusal (SR) in adolescence represents an important risk factor associated with adverse consequences. Although many clinical features of adolescents presenting with SR have been studied, the relationship between SR and personality styles-specifically in the help-seeking population-remains unclear. The present study aimed at investigating differences in personality style, adaptive functioning, and symptomology between Italian help-seeking adolescents who refused (SRa) and did not refuse (non-SRa) to attend school, to provide preliminary evidence of personality patterns in adolescent help-seekers presenting with SR.Method: The study sample was comprised of 103 help-seeking adolescents (54 female, 49 male) aged 14-18 years. Participants were recruited during their first clinical visit and evaluated using the Shedler and Westen Assessment Procedure - Adolescent version (SWAP-A), the Hamilton Rating Scale for Depression (HAM-D), the Hamilton Rating Scale for Anxiety (HAM-A), the Maniac Rating Scale (MRS), the Global Assessment of Functioning (GAF), the Global Functioning Social Scale (GFSS), and the Global Functioning Role Scale (GFRS). Differences in the studied variables between SRa and non-SRa were measured and a multivariable logistic regression analysis was performed to identify possible predictive factors of SR.Results: SRa presented with more anxious and depressive symptomatology and worse social functioning compared to non-SRa. With respect to personality, SRa displayed more schizoid and schizotypal characteristics and fewer adaptive and healthy personality features. Irrespective of any differences between groups, SRa were largely characterized by inhibited-self-constricted and emotionally dysregulated personality styles.Conclusions: The results suggest that personality styles arc clinical features that may contribute to broadening our knowledge of SR behavior and aid in the detection of SRa, also in the help-seeking population. The findings have clinical, social, and political implications for prevention, diagnosis, and treatment, in both clinical and non-clinical settings. However, more data are needed on personality features to clarify their contribution to the more complex phenomenon of school absenteeism

Fast LIPSS based texturing process of dental implants with complex geometries

In the present work, the generation of Laser Induced Periodic Surface Structures (LIPSS) by using femtosecond laser source is investigated in the surface texturing of Ti grade 5 dental implants. The proposed procedure permits a fast treatment of dental implants characterized by complex shape through the combined and synchronous use of a galvo scanner and of workpiece movements. The obtained surface micro- and nanostructures are characterized from a morphological point of view while in-vitro essays are performed to evaluate cellular proliferation. The results indicate the effectiveness of the LIPSS as a method to increase cell viability and the efficiency of the proposed procedure to treat complex geometries as dental implants