cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.6857549.v1
title: Obtención de compuesto de titanio con gradiente de porosidad mediante técnica pulvimetalúrgica

description: ABSTRACT Within the study of biomaterials for implantological use titanium is among the most widely employed metals due to its excellent corrosion and mechanical resistance. In spite of the advances made, there are some issues remaining with the value of the elastic moduli of the titanium (110GPa) in comparison with the elastic moduli of the cortical bone (20-30 GPa) and the trabecular bone (1-5GPa). This difference is one of the main reasons a bone prosthesis fails once implanted, producing what is known as Stress shielding. One of the techniques employed to diminish the elastic moduli of titanium consists in incorporating pores to the material. This is done through powder metallurgy techniques, allowing the fabrications of porous composites, sintering a mix of powders of metallic hydrides and spacers that are eliminated during the heat treatment. Taking into account the structural characteristics of the bone, it makes sense to think on the possibility of fabricating a prosthesis with pore gradients. Another problem encountered when employing titanium, is its inability to promote the osteointegration. There are different techniques to tackle this problem, and one of them is to incorporate hydroxyapatite which has the problem that it decomposes in the presence of titanium when sintered at high temperatures. The current study shows the results obtained during the fabrication of samples of titanium with pore gradients. We studied different fabrication techniques, analyzing each stage during the powder metallurgy. process. The obtained material was characterized mechanically through compression tests, determining the elastic moduli of the composite, which was found to be between 16.4 and 20 GPa. Also, different physical characterization methods where employed to analyse the pore content which was found to be 18%. The obtained data was employed for the estimation of elastic moduli of the compound, and compared to the empirical results obtained with the mechanical tests.
DOI: 10.6084/m9.figshare.6857546.v1
title: Optimización del proceso RSW para acero DP 1000

description: ABSTRACT In recent times new materials have been introduced in automobiles construction in order to reduce their weight and consequently fuel consumption and emissions level. Among them are Dual Phase (DP) steels, constituted by a ferritic matrix with martensite islands. Resistance Spot Welding (RSW) is the most commonly used welding process in the automotive industry. However, the welding of these materials presents greater challenges, since the parameters used for RSW welding of conventional steels are not applicable on these advanced steels. Also, the welding thermal cycle degraded its properties, with the minimum hardness being found in the sub and/or inter critical zone. In turn, due to the high cooling rates imposed by the strong cooling of the electrodes, structures of high hardness can be generated in the nugget region. In this sense, the optimization of welding procedures is of particular interest. In other way, productivity is an great relevance aspect in these applications, thus reducing welding times is a requirement. The objective of this work is to evaluate the effect of RSW welding parameters on DP1000 steels in order to optimize them. To this end, 1.2 mm thick DP1000 steel probes were welded by RSW, varying the current and the welding time. On the welded joints, macro and microstructural characterization was performed by optical and scanning electron microscopy, Vickers microhardness profiles and peel-test and shear-test stripping tests. The fracture surfaces were analyzed by light microscopy. A set of parameters that optimizes the welding process of DP1000 steels by RSW was obtained. It was found that from 10 welding cycles and with current levels of 7 KA the points achieves the dimensional requirements and mechanical properties adopted by the automotive industry.
DOI: 10.6084/m9.figshare.6857540
title: Releasing systems for aerospace industry based upon Shape Memory Alloys: characterization of materials for actuators

description: ABSTRACT Releasing and deployment maneuvers carried out during space satellites launching are usually performed by utilizing pyrotechnics loads. However, it is considered convenient to replace this technique by others not requiring explosives (Non Explosive Actuators-NEA). This is mainly due to the necessity of reducing high-shock and vibrations induced levels, also avoiding the contamination of sensible instruments because of dust and gas release during explosion. In addition, the avoidance of risks associated with storage and manipulation of explosives and the possibility of performing device retesting prior to final mounting are desirable qualities. Among NEA devices, those exploiting the singular mechanical behavior of Shape Memory Alloys (SMA) have reached commercial maturity. In this study, the performance of a NEA device that uses the mechanical stress generated upon reverse transformation of a mechanically constrained SMA actuator (constrained recovery effect) to generate the controlled fracture of a notched bolt is analyzed. Firstly, the mechanical components of the system are described, and the main problems associated with its design are introduced. Then, the results of the experimental characterization performed on a NiTi SMA cylindrical tube actuator with 12.7 and 7.8 mm outer and inner diameter respectively, are presented. After an activation stage in which the cylinder is compressed to induce the martensitic phase (or re-orient the existing martensític phase), the temperature is raised while a constant displacement condition is imposed. For temperatures near 120 ºC, a loads increment of 35 kN (440 MPa) is obtained. The repetition of this loading-unloading-heating-cooling cycle does not generate any important deterioration in the material response.
DOI: 10.6084/m9.figshare.6857543
title: Application of a composite ultrafiltration membrane for biodiesel purification

description: ABSTRACT This study was carried out to investigate the potentialities of the application of membrane technology in biodiesel purification without need of the decantation step. A new composite UF membrane was prepared from poly(vinylidene fluoride) casting solution (17 wt%) containing a sulfonated Carbon (20 wt%). The assays were performed in a dead-end filtration cell with synthetic mixtures of the transesterification reaction products. The influence of two operational variables was analyzed, transmembrane pressure (∆P = 4-8 bar) and temperature (T = 50-60°C). The membrane performance was evaluated determining the flux and the permeate compositions. Temperature resulted to be the most important operational variable. An increase in 10°C duplicated the permeate flux at 6 and 8 bar. The best performance was obtained at 60°C and 8 bar, with a flux of 12.6 Lm-2h-1. In this operative conditions, the influence of the added acidified water (Wadd = 0-20 %v/v) in the synthetic mixture was evaluated, which increased considerably permeate fluxes. Finally, the impact of synthetic mixture composition was determined for the assayed best operational conditions. The higher flux value was measured in the mixture with less glycerol and without soaps. In all assays the biodiesel retention was complete and the permeates were composed mainly of glycerol and ethanol.
DOI: 10.6084/m9.figshare.6857537
title: Effect of strain-path change on the formability of DP-780 steel and Zn20 zinc sheets

description: ABSTRACT The Forming Limit Diagram (FLD), frequently used to characterize the formability of sheet metals, is determined by assuming proportional loading histories up to the onset of necking. However, the limit strains are highly affected by strain-paths changes, which are very usual in real metal forming processes. The aim of this work is to analyze the effect of the loading history on the FLDs of a 0,9 mm thick DP-780 steel sheet and a 0,65 mm thick Zn20 zinc sheet by applying two-stage tests. The forming limits are studied under uniaxial deformation for the biaxially pre-deformed materials. The reference FLD was obtained by hydraulic bulge tests and uniaxial tests with different samples geometries. The limit strains of the pre-deformed DP-780 steel sheet are above the reference FLD, which reveals a non-negligible dependency between the material formability and the loading history. On the other hand, the differences between the FLDs of the zinc sheet are significant. This is attributed not only to the effect of changes in the strain path, but also to the continuous dynamic recrystallization experienced by the material at room temperature.
DOI: 10.6084/m9.figshare.6857540.v1
title: Releasing systems for aerospace industry based upon Shape Memory Alloys: characterization of materials for actuators

description: ABSTRACT Releasing and deployment maneuvers carried out during space satellites launching are usually performed by utilizing pyrotechnics loads. However, it is considered convenient to replace this technique by others not requiring explosives (Non Explosive Actuators-NEA). This is mainly due to the necessity of reducing high-shock and vibrations induced levels, also avoiding the contamination of sensible instruments because of dust and gas release during explosion. In addition, the avoidance of risks associated with storage and manipulation of explosives and the possibility of performing device retesting prior to final mounting are desirable qualities. Among NEA devices, those exploiting the singular mechanical behavior of Shape Memory Alloys (SMA) have reached commercial maturity. In this study, the performance of a NEA device that uses the mechanical stress generated upon reverse transformation of a mechanically constrained SMA actuator (constrained recovery effect) to generate the controlled fracture of a notched bolt is analyzed. Firstly, the mechanical components of the system are described, and the main problems associated with its design are introduced. Then, the results of the experimental characterization performed on a NiTi SMA cylindrical tube actuator with 12.7 and 7.8 mm outer and inner diameter respectively, are presented. After an activation stage in which the cylinder is compressed to induce the martensitic phase (or re-orient the existing martensític phase), the temperature is raised while a constant displacement condition is imposed. For temperatures near 120 ºC, a loads increment of 35 kN (440 MPa) is obtained. The repetition of this loading-unloading-heating-cooling cycle does not generate any important deterioration in the material response.
DOI: 10.6084/m9.figshare.6857543.v1
title: Application of a composite ultrafiltration membrane for biodiesel purification

description: ABSTRACT This study was carried out to investigate the potentialities of the application of membrane technology in biodiesel purification without need of the decantation step. A new composite UF membrane was prepared from poly(vinylidene fluoride) casting solution (17 wt%) containing a sulfonated Carbon (20 wt%). The assays were performed in a dead-end filtration cell with synthetic mixtures of the transesterification reaction products. The influence of two operational variables was analyzed, transmembrane pressure (∆P = 4-8 bar) and temperature (T = 50-60°C). The membrane performance was evaluated determining the flux and the permeate compositions. Temperature resulted to be the most important operational variable. An increase in 10°C duplicated the permeate flux at 6 and 8 bar. The best performance was obtained at 60°C and 8 bar, with a flux of 12.6 Lm-2h-1. In this operative conditions, the influence of the added acidified water (Wadd = 0-20 %v/v) in the synthetic mixture was evaluated, which increased considerably permeate fluxes. Finally, the impact of synthetic mixture composition was determined for the assayed best operational conditions. The higher flux value was measured in the mixture with less glycerol and without soaps. In all assays the biodiesel retention was complete and the permeates were composed mainly of glycerol and ethanol.
DOI: 10.6084/m9.figshare.6857534
title: Effect of parameters of micro-arc oxidation process on Ti-6Al-4V ELI for dental implants

description: ABSTRACT In order to study the variation effect of some parameters of micro-arc oxidation process (MAO) on Ti-6Al-4V samples for dental implants, several treatments were carried out under different conditions of current density, exposure time and electrolyte chemical composition. These processes resulted in generated bioactive titanium oxide surface coatings enriched in calcium and phosphorus. The MAO treatment was perfomed from two starting surface conditions: machining and blasting. After each MAO treatment, an alkali treatment was performed to evaluate its influence on the bioactivity of the coating obtained. The surfaces were characterized by means of topographic analysis with scanning electron microscopy, coating adhesion from Rockwell-C standard test and bioactivity in a simulated body fluid test (SBF). The best results (uniform and bioactive coatings with satisfactory performance in the adhesion assay) were attained with longer treatment times and in phosphoric-sulfuric and potassium diacid phosphate electrolytes. Furthermore, the results showed that the blasting treatment previous to MAO process enhanced the coating adhesion while a subsequent alkaline treatment improved MAO bioactivity.
DOI: 10.6084/m9.figshare.6857534.v1
title: Effect of parameters of micro-arc oxidation process on Ti-6Al-4V ELI for dental implants

description: ABSTRACT In order to study the variation effect of some parameters of micro-arc oxidation process (MAO) on Ti-6Al-4V samples for dental implants, several treatments were carried out under different conditions of current density, exposure time and electrolyte chemical composition. These processes resulted in generated bioactive titanium oxide surface coatings enriched in calcium and phosphorus. The MAO treatment was perfomed from two starting surface conditions: machining and blasting. After each MAO treatment, an alkali treatment was performed to evaluate its influence on the bioactivity of the coating obtained. The surfaces were characterized by means of topographic analysis with scanning electron microscopy, coating adhesion from Rockwell-C standard test and bioactivity in a simulated body fluid test (SBF). The best results (uniform and bioactive coatings with satisfactory performance in the adhesion assay) were attained with longer treatment times and in phosphoric-sulfuric and potassium diacid phosphate electrolytes. Furthermore, the results showed that the blasting treatment previous to MAO process enhanced the coating adhesion while a subsequent alkaline treatment improved MAO bioactivity.
DOI: 10.6084/m9.figshare.6857531
title: Treatment of aqueous effluents from the biodiesel industry using membrane technology

description: ABSTRACT The wastewaters from biodiesel production are generated mainly in the washing process, in this step the contaminants of biodiesel are eliminated in order to the obtained biodiesel meets with the internationals regulations. These wastes contain impurities such as methyl ester, residual oil, mono and diglycerides, soluble salts, catalyst, soap, glycerol and alcohol. The aim of this study is the application of membrane technology for the treatment of aqueous wastes from biodiesel industry. By means of the phase inversion method was synthesized a membrane of UF using a 17wt% of polyvinylidene polyfluoride (PVDF) and 8,5wt % polyvinylpyrrolidone (PVP) casting solution. The filtration essays were performed in a cross flow cell. The operational conditions were: T= 20°C, Δp=0.4-1 bar y v=0.5-1 m/s. A synthetic sample prepared in the laboratory and a real effluent sample from biodiesel industry was employed as membrane feed. At constant feed stream speed, the permeate flux decreases with increase of pressure (mass transfer controlled region). While an increasing in the permeation speed at constant pressure the permeate flux gradually increases. With increasing speed, membrane surface cleaning increases due to solutes are swept tangentially away. It was concluded that the studied membrane retains between 83-100% of oils and fats, and between 20-40% of DQO, whereas pH and TSS remain constant.
DOI: 10.6084/m9.figshare.6857537.v1
title: Effect of strain-path change on the formability of DP-780 steel and Zn20 zinc sheets

description: ABSTRACT The Forming Limit Diagram (FLD), frequently used to characterize the formability of sheet metals, is determined by assuming proportional loading histories up to the onset of necking. However, the limit strains are highly affected by strain-paths changes, which are very usual in real metal forming processes. The aim of this work is to analyze the effect of the loading history on the FLDs of a 0,9 mm thick DP-780 steel sheet and a 0,65 mm thick Zn20 zinc sheet by applying two-stage tests. The forming limits are studied under uniaxial deformation for the biaxially pre-deformed materials. The reference FLD was obtained by hydraulic bulge tests and uniaxial tests with different samples geometries. The limit strains of the pre-deformed DP-780 steel sheet are above the reference FLD, which reveals a non-negligible dependency between the material formability and the loading history. On the other hand, the differences between the FLDs of the zinc sheet are significant. This is attributed not only to the effect of changes in the strain path, but also to the continuous dynamic recrystallization experienced by the material at room temperature.
DOI: 10.6084/m9.figshare.6857528
title: Strategy for the optimization of a rubber compound with soybean oil using design of experiments

description: ABSTRACT When a rubber component is made, is necessary to start from a “rubber compound” which may be composed of one or more polymers and various additives or fillers. The development of an elastomer mixture to produce a compound with a specific end-use is complicated in the field of rubber technology. Therefore, the successful development of a compound requires a systematic work, being crucial to use a statistical design of experiments (DoE). By implementing the DoE, the variables for the system under investigation should be selected; i.e., the observed or measured variables (responses, compound properties to be controlled) and the independent variables describing the system (the ingredients and amounts in the formulation of the compound). The purpose of the DoE is to specify the value of the independent variables, as well as to select the appropriate response. The DoE strategy was already tested using two grades of E-SBR rubber (emulsion styrene-butadiene), E-SBR 1712, E-SBR 1721 and a BR rubber (polybutadiene) high-cis, in order to find a mixture of the three with properties comparable to those of a high performance tire. In this paper we will show the use of the DoE strategy working with the extender oil added to the compound. A mixture of three types of oils, two petrochemical oils (Pq1 and Pq2) and soybean oil are used, seeking to maximize the amount of the latter. The tested properties are those related to features required for the tread of a tire: the glass transition temperature (Tg); the ratio between the viscous modulus and the elastic modulus (tanδ@60°C); the Mooney Viscosity and the tensile-elongation properties. The values obtained for each measured property were fit to statistically significant models, yielding response surfaces for the properties. The surfaces are combined in the desirability function, where values are set for each property and under the condition that the amount of soybean oil is maximum in the mixture. Applying this desirability function, it was possible to predict the optimal composition of oils (3.17 pHq of oil Pq1, 5.90 pHR of oil Pq2 and 7.86 pHR of soybean oil) to be added to the compound to achieve the desired properties. The successful experimental validation of the proposed models shows the ability of DoE as a useful strategy for the optimization of properties in a rubber compound with complex formulation.
DOI: 10.6084/m9.figshare.6857528.v1
title: Strategy for the optimization of a rubber compound with soybean oil using design of experiments

description: ABSTRACT When a rubber component is made, is necessary to start from a “rubber compound” which may be composed of one or more polymers and various additives or fillers. The development of an elastomer mixture to produce a compound with a specific end-use is complicated in the field of rubber technology. Therefore, the successful development of a compound requires a systematic work, being crucial to use a statistical design of experiments (DoE). By implementing the DoE, the variables for the system under investigation should be selected; i.e., the observed or measured variables (responses, compound properties to be controlled) and the independent variables describing the system (the ingredients and amounts in the formulation of the compound). The purpose of the DoE is to specify the value of the independent variables, as well as to select the appropriate response. The DoE strategy was already tested using two grades of E-SBR rubber (emulsion styrene-butadiene), E-SBR 1712, E-SBR 1721 and a BR rubber (polybutadiene) high-cis, in order to find a mixture of the three with properties comparable to those of a high performance tire. In this paper we will show the use of the DoE strategy working with the extender oil added to the compound. A mixture of three types of oils, two petrochemical oils (Pq1 and Pq2) and soybean oil are used, seeking to maximize the amount of the latter. The tested properties are those related to features required for the tread of a tire: the glass transition temperature (Tg); the ratio between the viscous modulus and the elastic modulus (tanδ@60°C); the Mooney Viscosity and the tensile-elongation properties. The values obtained for each measured property were fit to statistically significant models, yielding response surfaces for the properties. The surfaces are combined in the desirability function, where values are set for each property and under the condition that the amount of soybean oil is maximum in the mixture. Applying this desirability function, it was possible to predict the optimal composition of oils (3.17 pHq of oil Pq1, 5.90 pHR of oil Pq2 and 7.86 pHR of soybean oil) to be added to the compound to achieve the desired properties. The successful experimental validation of the proposed models shows the ability of DoE as a useful strategy for the optimization of properties in a rubber compound with complex formulation.