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Materials Research, Volume: 15, Número: 2, Publicado: 2012
  • Effect of mixing time on the bed density, and microstructure of selective laser sintered (sls) aluminium powders Regular Articles

    Olakanmi, Eyitayo Olatunde

    Resumo em Inglês:

    The effect of mixing time on the homogeneity of aluminium powder blends and its SLS processed density and microstructure has been explored with a view to providing a basis for quality control. The degree of mixing of the powder particles was quantified in terms of the standard deviation of the bed density of the blended powder. The accuracy of the degree of mixing of aluminium powder's blends obtained at the optimum blending time of 10 minutes is determined by the powder properties and this significantly influenced the powder's bed density. By increasing the mixing time above 10 minutes, particulate agglomeration which inhibit good packing of powdered particles occurs, thus, sintered density decreases and porosity increases. Therefore, high porosity in the powder bed hinders effective thermal conductivity between aluminium particles, thereby, leading to deterioration of the sintered density and microstructure of the SLS processed samples.
  • Improvement compressive strength of cementitious composites in different curing media by incorporating ZrO2 nanoparticles Regular Articles

    Rafieipour, Mohammad Hossein; Nazari, Ali; Mohandesi, Mohammad Ali; Khalaj, Gholamreza

    Resumo em Inglês:

    In the present work, the effect of curing medium on microstructure, physical, mechanical and thermal properties of ZrO2 nanoparticles blended concrete has been investigated. ZrO2 nanoparticles were partially used instead of cement by 0.5, 1.0, 1.5 and 2.0 weight percent. Curing of the specimens was carried out in water and saturated limewater for 7, 28 and 90 days. The results indicate that ZrO2 nanoparticles up to maximum of 2.0% produces cementitious composite with improved compressive strength by curing in saturated limewater. The optimum level of replacement for the specimens cured in water was 1.0 weight percent. ZrO2 nanoparticles can improve the filler effects and also the high activity of fine particles substantially increases the quantity of strengthening gel. Although the limewater reduces the strength of concrete without nanoparticles when compared with the specimens cured in water, curing the specimens in saturated limewater results in more strengthening gel formation around ZrO2 nanoparticles blended concrete causes high strength.
  • Microstructural characterization of as-cast hf-b alloys Regular Articles

    Gigolotti, João Carlos Jânio; Suzuki, Paulo Atsushi; Nunes, Carlos Angelo; Coelho, Gilberto Carvalho

    Resumo em Inglês:

    An accurate knowledge of several metal-boron phase diagrams is important to evaluation of higher order systems such as metal-silicon-boron ternaries. The refinement and reassessment of phase diagram data is a continuous work, thus the reevaluation of metal-boron systems provides the possibility to confirm previous data from an investigation using higher purity materials and better analytical techniques. This work presents results of rigorous microstructural characterization of as-cast hafnium-boron alloys which are significant to assess the liquid composition associated to most of the invariant reactions of this system. Alloys were prepared by arc melting high purity hafnium (minimum 99.8%) and boron (minimum 99.5%) slices under argon atmosphere in water-cooled copper crucible with non consumable tungsten electrode and titanium getter. The phases were identified by scanning electron microscopy, using back-scattered electron image mode and X-ray diffraction. In general, a good agreement was found between our data and those from the currently accepted Hafnium-Boron phase diagram. The phases identified are αHfSS and B-RhomSS, the intermediate compounds HfB and HfB2 and the liquide L. The reactions are the eutectic L ⇔ αHfSS + HfB and L ⇔ HfB2 + B-Rhom, the peritectic L + HfB2 ⇔ HfB and the congruent formation of HfB2.
  • Flexural behavior of Sisal/Castor oil-Based Polyurethane and Sisal/Phenolic Composites Regular Articles

    Milanese, Andressa Cecília; Cioffi, Maria Odila Hilário; Voorwald, Herman Jacobus Cornelis

    Resumo em Inglês:

    Natural fibers used as reinforcement of polymeric composites are interesting research subjects in polymer technology. Nowadays, these materials are being considered as a way to reinforce timber structures improvement. Fibers with larger structural applications are glass and carbon fibers, however, the use of natural fibers is an economic alternative and present many advantages such as biodegradability and having its origin from a renewable source. Castor oil, a triglyceride vegetable with hydroxyl groups, was reacted with 4,4' methylene diphenyl diisocyanate (MDI) to produce the polyurethane matrix. The composites were prepared by compress molding at room temperature using woven sisal fiber as a reinforcement, with and without thermal treatment (at 60 ºC for 72 hours) to the fabrics before the composites molding process. The present paper presents the preparation and a flexural caracterization of sisal/polyurethane and sisal/phenolic composites by using the three-point bending. The sisal fibers moisture content influence on the flexural behaviour was also analyzed. Experimental results showed a higher stiffness for the sisal/phenolic composite (11.2 MPa) followed by the sisal/polyurethane (3.7 MPa), respectively.
  • Pyroelectric composite film for X-ray intensity detection Regular Articles

    Sakamoto, Walter Katsumi; Estevam, Giuliano Pierre; Carvalho, Aparecido Augusto de; Pontes, Wesley; Paula, Mauro Henrique de

    Resumo em Inglês:

    Composite material obtained with modified lead titanate (Pz34) ferroelectric ceramic and polyether-ether-ketone (PEEK) polymer matrix was used as sensitive component to measure X-ray intensity in a novel detection system. The sensing element works as a thermal transducer, converting a non-quantified thermal flux into an output measurable quantity of electrical voltage. The samples were obtained up to 60 vol.% of ceramic, by hot pressing the mixture of Pz34 and PEEK powders at 368 °C and applying 12 MPa pressure for 2.0 hours. The sensor response varies from 2.70 to 0.80 V in the energy fluence rate range of 6.30 to 37.20 W.m-2. The absorbed incident energy was analyzed as a function of the ionizing energy. Furthermore, by measuring the pyroelectric activity of the composite film it was observed that there is no degradation of the sensor after the irradiation.
  • Characterization of calcium carbonate obtained from oyster and mussel shells and incorporation in polypropylene Regular Articles

    Hamester, Michele Regina Rosa; Balzer, Palova Santos; Becker, Daniela

    Resumo em Inglês:

    There is a high content of calcium carbonate in mussel and oyster shells, which can be used in the formulation of medicine, in construction or as filler in polymer materials. This work has as its main objective to obtain calcium carbonate from mussel and oyster shells and used as filler in polypropylene compared their properties with polypropylene and commercial calcium carbonate composites. The shellfish was milling and heated at 500 ºC for 2 hours. The powder obtained from shellfish were characterized by scanning electron microscopy (SEM), X-ray fluorescence, particle size distribution and abrasiveness and compared with commercial CaCO3 and mixed with polypropylene. The thermal and mechanical properties of polypropylene with CaCO3 obtained from oyster and mussel shells and with commercial CaCO3 were analysed. The results showed that CaCO3 can be obtained from oyster and mussel shell and is technically possible to replace the commercial CaCO3 for that obtained from the shells of shellfish in polypropylene composites.
  • Optical (DRUV-VIS) and magnetic (EPR) behavior of synthetic melanins Regular Articles

    Santos, Júlio César Pereira dos; Marino, Cláudia Eliana Bruno; Mangrich, Antonio Salvio; Rezende, Edivaltrys Inayve Pissinati de

    Resumo em Inglês:

    The properties of melanins prepared from L-dopa oxidation by both chemical and electrochemical methods are reported, searching for a material with more intense optical absorption in the visible region. The characterization of the samples have been done by cyclic voltammetry (CV), cronoamperometry (CA), Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance spectroscopy (EPR) and diffuse reflectance ultraviolet-visible spectroscopy (DRUV-VIS) techniques. The electrochemical method enhanced the organic free radical (spin) concentration and the absorption intensity in the visible region of the spectrum. The DRUV-VIS technique along with mathematical tools, such as the Kubelka-Munk remission function, were good options for the characterization of the final products.
  • Cytotoxicity tests for nanostructured chitosan/PEO membranes using the agar diffusion method Regular Articles

    Vulcani, Valcinir Aloisio Scalla; Bizarria, Maria Trindade Marques; d’Ávila, Marcos Akira; Mei, Lucia Helena Innocentini; Bernal, Cláudia; Perussi, Janice Rodrigues

    Resumo em Inglês:

    Electrospinning is used to produce fibers in the nanometer range by stretching a polymeric jet using electric fields of high magnitude. Chitosan is an abundant natural polymer that can be used to obtain biocompatible nanostructured membranes. The objectives of this work were to obtain nanostructured membranes based on blends of chitosan and polyoxyethylene (PEO), and evaluate their thermal and morphological properties, as well as their in vitro biocompatibility by agar diffusion cytotoxicity tests for three different cell lines. A nanostructured fibrous membrane with fiber diameters in the order of 200 nm was obtained, which presented a rough surface and thickness ranging from one to two millimeters. The results of the cytotoxicity tests evidenced that the chitosan/PEO membranes are non-toxic to the cells studied in this work. Further, the electrospinning technique was effective in obtaining nanostructured chitosan/PEO membranes, which showed biocompatibility according to in vitro preliminary tests using the cell lines.
  • Correlation between small punch and CVN impact tests for evaluation of cryogenic fracture characteristics of isothermally-aged nitrogen-containing austenitic stainless steels Regular Articles

    Saucedo-Muñoz, Maribel Leticia; Hashida, Toshiyuki; Shoji, Tetsuo; Lopez-Hirata, Victor Manuel

    Resumo em Inglês:

    The Charpy-V-notch impact test has been used routinely to evaluate the ductile-brittle behavior in steels. Likewise, the Small-Punch test has been applied to evaluate toughness properties in different materials. In this work, both tests were conducted at -196 °C on three types of austenitic stainless steels JN1, JJ1 and JK2, which were solution treated and then aged at temperatures between 700 and 900 °C for 10 and 1000 minutes. The solution treated steels exhibited a ductile fracture with high fracture energy, after testing with both tests. The brittle intergranular fracture was induced by the aging process of specimens and thus the fracture energy of tested specimens decreased dramatically. The highest and lowest decreases in energy with both tests occurred in the aged JN1 and JK2 steels, respectively. The Charpy-v-notch, CVN, test energy and small-punch, SP, test energy at -196 °C was found to follow a linear correlationship equation, CVN Test Energy = 89.7 SP Test Energy -63.0.
  • Osteoinduction test of anorthite by human mesenchymal stem cell culture Regular Articles

    Sousa, Jônatas; Fernandes, Beatriz Luci; Rebelatto, Carmem Lúcia Kuniyoshi; Barchiki, Fabiane; Abud, Ana Paula; Brofman, Paulo; Oliveira, Simone de; Buchi, Dorly; Fernandes, Carlos Roberto

    Resumo em Inglês:

    In this work, adult stem cells of three volunteers were isolated, expanded and cultivated over samples of Anorthite in order to assess its osteoinductive capacity. Alkaline Phosphatase Analysis, ALP, was carried out at days 1, 7, 14 and 21, and the results showed similar behavior between the volunteers considering the initial value of each. For volunteer 1, between day 14 and 21, the decreasing of ALP was remarkable in the wells containing MSC only and MSC+BIO, from 59.9 to 26.3 U.L-1 and from 63.3 to 38.1 U.L-1, respectively, suggesting that the biomaterial was able to induce osteoblast formations. This osteoinduction property could be evidenced by Citochemistry where MSCs did not produce crystals of Calcium Oxalate or Calcium Phosphate, osteoblast compounds, without being stimulated by a chemical inducer, lending to the conclusion that the differentiation of MSC into osteoblast when cultivated on Anorthite, occurred exclusively by its influence, strongly suggesting that it is osteoinductive.
  • Mg2FeH6-based nanocomposites with high capacity of hydrogen storage processed by reactive milling Regular Articles

    Asselli, Alexandre Augusto Cesario; Jorge Junior, Alberto Moreira; Ishikawa, Tomaz Toshimi; Botta Filho, Walter José

    Resumo em Inglês:

    The compound Mg2FeH6 was synthesized from a 2Mg-Fe mixture in a single process through high-energy ball milling under hydrogen atmosphere at room temperature. The complex hydride was prepared from Mg powder and granulated or powdered Fe using a planetary mill. The phase evolution during different milling times was performed by X-rays diffraction technique. The dehydrogenation behavior of the hydride was investigated through simultaneous thermal analyses of differential scanning calorimetry and thermogravimetry coupled with mass spectrometer. The use of powdered iron as starting material promoted conversion to complex hydride at shorter milling times than when granulated iron was used, nevertheless, after 24 hours of milling the 2Mg-Fe (powdered or granulated) mixtures presented similar dehydrogenation behavior. The hydrogen absorption during milling was on average 3.2 wt. (%), however, changing the proportions of the reagents to 3Mg-Fe a Mg2FeH6-MgH2 based nanocomposite with higher density of hydrogen (5.2 wt. (%)) was obtained.
  • Study on effects of wood fiber content on physical, mechanical, and acoustical properties of wood-fiber-filled gypsum composites Regular Articles

    Ramezani, Hamed; Shahdab, Sina; Nouri, Ali

    Resumo em Inglês:

    The Acoustical model of wood-fiber-filled gypsum composites panel is presented. The transmission loss coefficients of the composite structures were calculated by an approximated approach. However, the physical and mechanical properties of board specimens including; water absorption, thickness swelling, bending modulus of elasticity, bending modulus of rupture, internal bond, and compression parallel to the surface obtained experimentally. Finally, the effects of wood fibers to gypsum mixing ratios on physical, mechanical and acoustical properties of composite flat structures were investigated and data analysis was done by use of statistical methods.
  • Prediction total specific pore volume of geopolymers produced from waste ashes by fuzzy logic Regular Articles

    Nazari, Ali; Khalaj, Gholamreza

    Resumo em Inglês:

    In the present work, total specific pore volume of inorganic polymers (geopolymers) made from seeded fly ash and rice husk bark ash has been predicted by fuzzy logic. Different specimens, made from a mixture of fly ash and rice husk bark ash in fine and coarse form together with alkali activator made of water glass and NaOH solution, were subjected to porosimetry tests at 7 and 28 days of curing. The curing regime was different: one set of the specimens were cured at room temperature until reaching to 7 and 28 days and the other sets were oven cured for 36 hours at the range of 40-90 °C and then cured at room temperature until 7 and 28 days. A model based on fuzzy logic for predicting the total specific pore volume of the specimens has been presented. To build the model, training and testing using experimental results from 120 specimens were conducted. The used data as the inputs of fuzzy logic models are arranged in a format of six parameters that cover the percentage of fine fly ash in the ashes mixture, the percentage of coarse fly ash in the ashes mixture, the percentage of fine rice husk bark ash in the ashes mixture, the percentage of coarse rice husk bark ash in the ashes mixture, the temperature of curing and the time of water curing. According to the input parameters, in the fuzzy logic model, the pore volume of each specimen was predicted. The training and testing results in the fuzzy logic model have shown a strong potential for predicting the total specific pore volume of the geopolymer specimens in the considered range.
  • Characterization of Brazilian Bentonite Organoclays as sorbents of petroleum-derived fuels Regular Articles

    Bertagnolli, Caroline; Silva, Meuris Gurgel Carlos da

    Resumo em Inglês:

    This work focused on preparing and characterizing Brazilian bentonite clay through the use of quaternary ammonium salt so as to apply it as a sorbent for petroleum-derived fuels. Bentonite clay was organophilizated by the intercalation of quaternary ammonium salts such as cetyl-pyridinium chloride and benzalkonium chloride. The resulting materials were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, N2 physisorption and infrared spectroscopy techniques. The clay similarity with petroleum-derived fuels, gasoline and diesel oil were defined by sorption and swelling tests. The increase in basal spacing and the appearance of absorption bands related to the CH2 and CH3 groups confirm the efficiency of Brazilian organoclays. Removal percentages between 50 and 60 for benzene, toluene and xylene indicate the potential of organoclay in the remediation of areas contaminated by petroleum-derived fuels.
  • Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4 Regular Articles

    Sousa, Rômulo Ribeiro Magalhães de; Araújo, Francisco Odolberto de; Costa, José Alzamir Pereira da; Oliveira, Antonio Maia de; Melo, Mineia Sampaio; Alves Junior, Clodomiro

    Resumo em Inglês:

    AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN), with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.
  • Analysis by design of experiments of distortion potentials in drawn and induction hardened wire Regular Articles

    Rocha, Alexandre da Silva; Nunes, Rafael Menezes; Hirsch, Thomas

    Resumo em Inglês:

    In this investigation a DoE (Design of Experiments) analysis of distortion for a typical manufacturing process of pre-straightened, cold drawn and induction hardened AISI 1045 cylindrical steel bars was carried out. A careful characterization of the material, including residual stress states and geometrical changes, was done for the different manufacturing steps. In order to identify effects and correlations on distortion behavior, the investigated variables included the drawing process itself with two different drawing angles, a stress relief treatment, which was applied to one part of the samples, and, finally, induction hardening with two different case depths. Main and statistically significant effects on the distortion of the induction hardened samples were found to be in this order, the drawing angle, the stress relief treatment and the induction hardening depth. It was also found that the distortion potentials are transmitted from the drawing process to further manufacturing steps and, consequently, from one production site to the next.
  • Naphthenic corrosion resistance, mechanical properties and microstructure evolution of experimental Cr-Mo steels with high Mo content Regular Articles

    Moura, Lorena Braga; Guimarães, Rodrigo Freitas; Abreu, Hamilton Ferreira Gomes de; Miranda, Hélio Cordeiro de; Tavares, Sérgio Souto Maior

    Resumo em Inglês:

    One method to face the effects of naphthenic acid corrosion in petroleun refining plants is to use alloys with good resistance to this kind of corrosion. For this purpose, molybdenum additions to chromium containing steels are specially recommended. In this work, experimental Fe-9Cr-xMo (x = 5, 7 and 9 wt. (%)) ingots were cast, forged and hot rolled before being tested in a naphthenic acid environment. Evolution of the mechanical properties with composition is presented. The precipitation and dissolution of phases were investigated with the help of Thermocalc and electron backscattered diffraction (EBSD).
  • Synthesis, characterization and catalytic properties of nanocrystaline Y2O3-coated TiO2 in the ethanol dehydration reaction Regular Articles

    Fajardo, Humberto Vieira; Longo, Elson; Leite, Edson Roberto; Libanori, Rafael; Probst, Luiz Fernando Dias; Carreño, Neftalí Lenin Villarreal

    Resumo em Inglês:

    In the present study, TiO2 nanopowder was partially coated with Y2O3 precursors generated by a sol-gel modified route. The system of nanocoated particles formed an ultra thin structure on the TiO2 surfaces. The modified nanoparticles were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) analysis, Zeta potential and surface area through N2 fisisorption measurements. Bioethanol dehydration was used as a probe reaction to investigate the modifications on the nanoparticles surface. The process led to the obtainment of nanoparticles with important surface characteristics and catalytic behavior in the bioethanol dehydration reaction, with improved activity and particular selectivity in comparison to their non-coated analogs. The ethylene production was disfavored and selectivity toward acetaldehyde, hydrogen and ethane increased over modified nanoparticles.
  • Some aspects of barreling in sintered plain carbon steel powder metallurgy preforms during cold upsetting Regular Articles

    Narayan, Sumesh; Rajeshkannan, Ananthanarayanan

    Resumo em Inglês:

    The present research establishes a relationship of bulged diameter with densification and hydrostatic stress in forming of sintered iron (Fe) powder metallurgy preforms cold upset under two different frictional conditions, namely, nil/no and graphite lubricant condition. Sintered plain carbon steel cylindrical preforms with carbon (C) contents of 0, 0.35, 0.75 and 1.1% with constant initial theoretical density of 84% and aspect ratio of 0.4 and 0.6 were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 minutes at 1200 °C. Each sintered preform was cold upset under two different frictional constraints. It is seen that the degree of bulging reduces with reducing frictional constraints at the die contact surface. Further, it is found that the bulging ratio changed as a function of relative density and hydrostatic stress, respectively, according to the power law equations.
  • Influence of wood moisture content on the modulus of elasticity in compression parallel to the grain Regular Articles

    Silva, Diogo Aparecido Lopes; Lahr, Francisco Antonio Rocco; Faria, Obede Borges de; Chahud, Eduardo

    Resumo em Inglês:

    Brazilian Standard ABNT NBR7190:1997 for timber structures design, adopts a first degree equation to describe the influence of wood moisture content. Periodically, when necessary, the referred standard is revised in order to analyze inconsistencies and to adopt considerations according new realities verified. So, the present paper aims to examine the adequacy of its equation which corrects to 12% of moisture the values of rigidity properties obtained on experimental tests. To quantify the moisture influence on modulus of elasticity, it was applied tests of compression parallel to the grain for six specimens of different strength classes, considering nominal moisture of 12; 20; 25; 30%. As results, modulus of elasticity in the moisture range 25-30% showed statistically equivalents, and was obtained a first degree equation to correlate the studied variables which leads to statically equivalent estimations when compared with results by ABNT NBR7190:1997 equation. However, it was indicated to maintain the current expression for the next text of the referred document review, without prejudice to statistical significance of the estimates.
  • Fatigue behavior and physical characterization of surface-modified Ti-6Al-4V ELI alloy by micro-arc oxidation Regular Articles

    Potomati, Fernanda; Giordani, Enrico José; Duarte, Laís Tereza; Alcântara, Nelson Guedes de; Bolfarini, Claudemiro

    Resumo em Inglês:

    Anodizing has proven an effective method for preparing bioactive titanium and has been the subject of many studies regarding the performance and biological characterization of the layers obtained. However, the fatigue behavior of titanium alloys, after undergoing this process is still poorly studied. This study aims to investigate the influence of MAO (Micro-Arc Oxidation) process on the fatigue properties of titanium alloy Ti-6Al-4V. Therefore axial fatigue tests were performed to obtain SxN curves, of specimens in polished and anodized (MAO processed, phosphate salt solution, potential of 290 V) conditions. Roughness measurements, SEM, Raman spectra and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize the features of the modified surface. SEM was also used to analyze the fatigue fractures of the tested specimens. The MAO process, with the parameters used in this investigation, had no influence on the fatigue behavior of the Ti-6Al-4V alloy, when compared to specimens without surface modification.
  • Grain refinement of commercial purity Magnesium processed by Ecap (Equal Channel Angular Pressing) Regular Articles

    Poggiali, Flávia Spitale Jacques; Figueiredo, Roberto Braga; Aguilar, Maria Teresa Paulino; Cetlin, Paulo Roberto

    Resumo em Inglês:

    Grain refinement in magnesium is evaluated in the present paper. Equal Channel Angular Pressing is used to process commercially pure magnesium. Processing was carried out at 523 K which is lower than the temperature used in other papers on the literature. The grain structure was evaluated throughout the deformation zone. The low processing temperature prevents significant grain growth. The evolution of the grain structure is compared to a recent model for mechanism of grain refinement in magnesium. The present results confirm the validity of the model.
  • Effect of initial microstructures on the properties of Ferrite-Martensite Dual-Phase pipeline steels with Strain-Based design Regular Articles

    Hu, Yueyue; Zuo, Xiurong; Li, Rutao; Zhang, Zhanzhan

    Resumo em Inglês:

    This study aims to investigate the effect of initial microstructures on the properties of ferrite-martensite dual-phase pipeline steels with strain-based design. For this purpose, the as-received acicular ferrite steels were first austenitized at 920 ºC for 15 minutes followed by air cooling and water quenching to produce ferrite-pearlite and ferrite-martensite microstructure, respectively. Subsequently, the steels with ferrite-pearlite, ferrite-martensite and as-received acicular ferrite microstructure were intercritically annealed at 820 ºC for 10 minutes followed by water quenching to produce three different ferrite-martensite dual-phase microstructures. Tensile tests, Vickers hardness and Charpy impact tests were carried out to investigate the mechanical properties. Scanning electron microscope was used to analyze the microstructures and tensile fractographs. The results showed that all the tensile specimens of these three different ferrite-martensite dual-phase steels fractured in ductile mode, however, their microstructures and mechanical properties varied significantly. By contrast, the ferrite-martensite dual-phase steel derived from acicular ferrite initial microstructure had optimal combination of the strength, toughness and deformability, which provided a good candidate for the pipeline steels with strain-based design used in severe geological environments.
  • Experimental study of impact energy absorption in aluminium square tubes with thermal triggers Regular Articles

    Peixinho, Nuno; Soares, Delfim; Vilarinho, Candida; Pereira, Pedro; Dimas, Dina

    Resumo em Inglês:

    This study presents an approach for the improvement of crashworthiness properties of aluminium tubular structures using initiators introduced through localized heating. The main objective of this approach is to improve the ability to absorb impact energy in a progressive and controlled manner by a local modification of material properties. Through a localized heating in areas previously chosen for initiation, associated with the softening of the aluminium alloy the deformation can be introduced precisely, forcing the tubular structure to deform in a mode of high energy absorption and reducing the maximum load in a controlled manner. This study presents the properties for an aluminium alloy 6061-T5 modified by thermal treatment by the use of a laser beam. Experimental results are presented of quasi-static and impact tests of tubular structures using the proposed approach. This concept appears as possible and effective in the experimental work presented.
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