Identifying Polymeric Constitutive Equations for Incremental Sheet Forming Modelling

AbstractRecent publications have revealed an increasing interest in forming polymer materials using Incremental Sheet Forming. Therefore, several constitutive material models are being developed in an attempt to predict the physical response of polymeric materials during the process. This paper discuss several material models that could be used to predict experimental data collected on samples of PVC and PC subjected to simple uniaxial test performed at various temperatures and testing speeds. The results have shown that the Marlow and the rule of mixture material models could be used to describe viscoelastic and softening and permanent set effects, respectively, to predict the behaviour of a part formed by Incremental Sheet Forming

A peach germplasm collection for increasing the genetic diversity in European breeding programs

Trabajo presentado al VIII International Peach Symposium, celebrado en Matera (Italia) del 17 al 20 de junio de 2013.European breeding programs are hampered by the low intraspecific genetic diversity, which is due to the self-compatibility of this homozygous species along with the low number of genotypes introduced and thus used for breeding. In 2009, four research institutions which carried out peach breeding programs in Aragon, Catalonia, Valencia and Murcia, started a new peach germplasm collection worldwide aimed at enlarging the peach genetic diversity available for breeding. The plant material was introduced from germplasm collections located in China, Central Asia, Iran and the USA (National Germplasm Repository of Davis). Sanitary status was assessed by molecular diagnosis of known diseases caused by virus, viroid, bacteria and phytoplasm pathogens. Healthy plant material was grafted and maintained in quarantine conditions. The new germplasm collection was established in two places: Zaragoza as high chilling and Murcia as low chilling requirements. Pomological and molecular data were gathered and a public database constructed. The descriptors used were from the National Center for Genetic Resources from the INIA. Introduced budwood and seeds resulted in more than 250 new genotypes from 15 countries. The molecular analysis of a subset of the collection with 21 SSR markers evenly distributed in the genome resulted in a high number of alleles per SSR (mean A=9.5) and low observed heterozygosity (mean Ho=0.38). Variability was further assessed by geographic origin. Population structure analysis revealed the existence of 8 subpopulations explained, in some cases, by the geographic origin of the genotypes. As a result of the project a new database containing 95 accessions and 38 variables is available.Peer reviewe

Contribución al estudio del proceso de doblado al aire de chapa. Modelo de predicción del ángulo de recuperación y del radio de doblado final

Modelo de predicción de la geometría final de una pieza de chapa, radio y ángulo de doblado final, producida mediante un proceso de doblado al aire.Prediction model of final geometry of sheet metal part, radius and final bending angle, manufactured by air free -V bending process

Development of P(3HB-co-3HHx) nanohydroxyapatite (nHA) composites for scaffolds manufacturing by means of fused deposition modeling

[EN] This work reports on the development of nanocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] and nanohydroxyapatite (nHA) for the development of scaffolds by means of a two-stage extrusion process followed by a 3D printing process. Tensile test samples were produced for the characterization of the materials. Each processing thermal cycle promoted a slight thermal degradation, identified by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Also, a viscosity reduction was observed in the rheological measurements. The 3D-printed tensile test samples exhibited increasing stiffness at increasing nHA content (with elastic modulus values close to 1000 MPa), while tensile strength and strain at break were reduced. Nonetheless, the deposition direction oriented with the tensile direction (raster angle of 0°C) exhibited the highest tensile strength (18 MPa) but lower elongation at break than the 45/45°C deposition, which resulted in the highest strain (up to 17 %). Regarding the scaffolds, they were degraded in phosphate-buffered saline at 37°C for 8 weeks. This degradation was identified by a reduction of their weight (between 1.5% and 3.0%) and reduced mechanical behavior measured by means of a compression test. Scaffolds showed a decrease of the compression strength (from values close to 13 MPa to 9 MPa).Juan Ivorra-Martinez wants to thank for the FPU19/01759 grant funded by MCIN/AEI/10.13039/501100011033 and, as appropriate, by ESF Investing in Your Future. Funding for open-access charge is provided by Universitat Politècnica de València (UPV). Marc Delgado-Aguilar is a Serra Húnter Fellow. Microscopy Services at UPV are also acknowledged for their help in collecting and analyzing images. This work is supported bythe grant PID2020-116496RB-C22 funded by MCIN/AEI/10.13039/501100011033 and the grant TED2021-131762A-I00 funded by MCIN/AEI/10.13039/501100011033 and by the European Union. Authors also thank Generalitat Valenciana-GVA for Funding this research through the grant numbers AICO/2021/025 and CIGE/2021/094. This study is also funded by Aid for First Research Projects (PAID-06-22) , Vice-rectorate for Research of the Universitat Politecnica de Valencia (UPV) .Ivorra-Martinez, J.; Ferrer, I.; Aguado, R.; Delgado-Aguilar, M.; Garcia-Romeu, ML.; Boronat, T. (2024). Development of P(3HB-co-3HHx) nanohydroxyapatite (nHA) composites for scaffolds manufacturing by means of fused deposition modeling. International Journal of Bioprinting. 10(1):274-293. https://doi.org/10.36922/ijb.015627429310

Revisiting formability and failure of polymeric sheets deformed by Single Point Incremental Forming

Single Point Incremental Forming (SPIF) has been intensively investigated in the last two decades. It is a versatile and economical manufacturing technology that is especially viable for small and medium-sized batches, with a great potential for manufacturing highly customized parts. One of the most important advantages of this technology is the greater formability it can attain compared to conventional sheet forming processes. The aim of this paper is to evaluate the overall formability of a series of polymeric sheets deformed by SPIF process, including biocompatible and non-biocompatible materials, while considering a variety of process parameters including spindle speed which, in previous studies on polymers formed by Incremental Sheet Forming (ISF), has been shown to be the most influential process parameter. The results show that variations in spindle speed caused a variation in the forming temperature and the material forming limits. For a better understanding of the deformation mechanism and the failure process of polymers during SPIF, a fractographic analysis using optical microscopy was carried out, as well as a Differential Scanning Calorimetry (DSC) analysis to determine the glass transition and melting temperatures and the degree of crystallinity of the polymersThe research leading to these results has received funding from the University of Girona (MPCUdG2016/036) and the Spanish Ministry of Education (DPI2016-77156-R and DPI2015-64047-R

Manufacturing PLA/PCL Blends by Ultrasonic Molding Technology

Ultrasonic molding (USM) is a good candidate for studying the plasticization of polymer mixtures or other composite materials due to either the little amount of material needed for processing, low waste or the needed low pressure and residence time of the mold. Thus, the novelty of this research is the capability of USM technology to process PLA/PCL blends and their corresponding neat materials, encompassing all the production stages, from raw material to the final specimen. The major findings of the work revealed that the thermal properties of the blends were not affected by the USM process, although the crystallinity degree experienced variations, decreasing for PLA and increasing for PCL, which was attributed to the crystallization rate of each polymer, the high process speed, the short cooling time and the small particle size. The employed ultrasonic energy increased the molecular weight with low variations through the specimen. However, the degradation results aligned with the expected trend of these material blends. Moreover, this study also showed the effect pellet shape and dimensions have over the process parameters, as well as the effect of the blend composition. It can be concluded that USM is a technology suitable to successfully process PLA/PCL blends with the correct determination of process parameter windows

Forming force prediction in two point incremental forming using backpropagation neural networks in combination with genetic algorithms

Process feasibility and material formability are two of the most concerning factors which are studied in Incremental Sheet Forming (ISF) process. They are two important matters under study of the scientific community with the final goal of improving the process performances and to make it reliable to allow its use for rapid prototyping and for small batch production. In recent years, the application of neural network techniques to forming processes has been a research topic for optimizing and predicting process parameters and ISF process has not been an exception. Unfortunately, there are some drawbacks in using Backpropagation (BP) neural networks, such as easily falling into local minimum point. Because of that, recently Genetic Algorithms (GA) are applied to BP networks in order to optimize them. This paper describes the application of BP networks and GA applied to BP networks for the prediction of the forming force in ISF process. These models have been developed using experimental data from several tests. The two point incremental forming (TPIF) tests were performed on a horizontal CNC milling machine and DC04 deep drawing sheets steel 0.8 mm thick were worked. The reliability of the proposed approach has been evaluated by testing the trained networks with unseen experimental data and the comparison between the two BP and GA-BP models are presented. All the details are accurately discussed in the paper

Breast Cancer Stem Cell Culture and Enrichment Using Poly(ε-Caprolactone) Scaffolds

The cancer stem cell (CSC) population displays self-renewal capabilities, resistance to conventional therapies, and a tendency to post-treatment recurrence. Increasing knowledge about CSCs’ phenotype and functions is needed to investigate new therapeutic strategies against the CSC population. Here, poly(ε-caprolactone) (PCL), a biocompatible polymer free of toxic dye, has been used to fabricate scaffolds, solid structures suitable for 3D cancer cell culture. It has been reported that scaffold cell culture enhances the CSCs population. A RepRap BCN3D+ printer and 3 mm PCL wire were used to fabricate circular scaffolds. PCL design and fabrication parameters were first determined and then optimized considering several measurable variables of the resulting scaffolds. MCF7 breast carcinoma cell line was used to assess scaffolds adequacy for 3D cell culture. To evaluate CSC enrichment, the Mammosphere Forming Index (MFI) was performed in 2D and 3D MCF7 cultures. Results showed that the 60° scaffolds were more suitable for 3D culture than the 45° and 90° ones. Moreover, 3D culture experiments, in adherent and non-adherent conditions, showed a significant increase in MFI compared to 2D cultures (control). Thus, 3D cell culture with PCL scaffolds could be useful to improve cancer cell culture and enrich the CSCs population

Classe de problemes alternativa: aprenentatge cooperatiu i actiu

Aquesta comunicació presenta l’activitat anomenada 'classe de problemes alternativa', basada en principis d’aprenentatge cooperatiu i d’aprenentatge actiu per part de l’alumne. De manera que, per un costat es detallen els seus objectius formatius, la seva descripció, el procediment i la planificació necessària per portar-la a terme, a més de la gestió de recursos necessaris, així com l’avaluació de l’activitat. De l’altre, es presenten els resultats acadèmics obtinguts aquest primer curs en el qual s’ha posat en pràctica, comparant-los amb els dels plans d’estudi anterior

Classe de problemes alternativa: aprenentatge cooperatiu i actiu

Aquesta comunicació presenta l’activitat anomenada 'classe de problemes alternativa', basada en principis d’aprenentatge cooperatiu i d’aprenentatge actiu per part de l’alumne. De manera que, per un costat es detallen els seus objectius formatius, la seva descripció, el procediment i la planificació necessària per portar-la a terme, a més de la gestió de recursos necessaris, així com l’avaluació de l’activitat. De l’altre, es presenten els resultats acadèmics obtinguts aquest primer curs en el qual s’ha posat en pràctica, comparant-los amb els dels plans d’estudi anterior