Low Specific Weight Research Articles

Fabricación y caracterización de aleaciones porosas de Ti y Ti6Al4V producidas mediante sinterización con espaciador

Titanium is well-known to be a biocompatible material with good corrosion properties and good strength, taking into account their low specific weight. In powder metallurgy field, titanium has been used in order to obtain porosity materials for biomedical applications. Recently, porous materials have been investigated for their use like hips implants. The principal reason is based on a reduction of stiffness implants, minimizing effects of stress shielding. The purpose of the present work is produced porous materials by space holder technique using ammonium bicarbonate like spacer. Scaffolds of titanium have been fabricated by powders of titanium with different grades of particle size and compacting pressure. Before sintering, stability of green parts has been studied by mechanical test. After sintering, porosity has been evaluated besides mechanical properties and elastic modulus by three points bending test. The microstructural characterisation is performed by optical and electron microscopy.

Surface Fatigue of Al-Metal Matrix Composites at Impact Loading

Aluminium 6061 has proven to be a suitable alloy as a basis for producing metal matrix composites (MMC). These MMCs have a low specific weight combined with a relatively good specific stiffness and high specific strength. The hardness and compressive strength of Al composites can be increased by reinforcing bulk material with nano particles. However the ductility of such alloys is relatively low, therefore one of the applications for such light alloys could be wear applications. In many wear conditions such as erosive or abrasive wear at normal impact angles the surface wear resistance plays a significant role. The surface fatigue properties have not been widely studied for such nanoparticle reinforced aluminium composites. The nano-reinforced composite materials were produced by means of high-energy milling (HEM) of nano-sized reinforcement particles together with a metallic matrix powder, followed by hot pressing. By utilizing up to 6 wt% multiwalled carbon nanotubes (MWCNT) as reinforcement the hardness of Al6061 MMC has been increased from 45 HV10 up to 317 HV10, compressive yield strength from 58 MPa up to 660 MPa and indentation modulus from 60 GPa up to 90 GPa compared to hot pressed Al6061. Surface fatigue tests were conducted at impact (dynamic) loading conditions using a hardened steel sphere as indenter. The Wöhler-like curves are plotted to estimate the surface fatigue. The surface fatigue indents were photographed by the aid of light optical microscopy (LOM) and analysed by image analysis software and optical profilometry (OP).

Microstructure, mechanical, and anticorrosive properties of a new Ti-20Nb-10Zr-5Ta alloy based on nontoxic and nonallergenic elements

For an alloy to be suitable for use as an implant material, it must have a low specific weight and Young’s modulus, good mechanical properties that are similar to those of bone, and very good corrosion resistance and biocompatibility. In this study, we have developed a novel Ti-20Nb-10Zr-5Ta alloy that is composed of nontoxic, nonallergenic, corrosion-resistant elements. This alloy has low specific weight and Young’s modulus and good mechanical properties. It has a fine microstructure with a matrix that is mainly composed of the β phase and some α phase due to recrystallization during cooling. It shows elastoplastic behavior with a fairly linear elastic behavior and low Young’s modulus (59 GPa). In addition, its ultimate tensile strength, 0.2% yield strength, and hardness are higher than those of CP Ti, commercial Ti-6Al-4V, and similar β-type alloys. It exhibited a very stable passive state and its electrochemical parameters and corrosion and ion release rates were better than those of CP Ti in Ringer’s solutions of different pH values that simulate the severe functional conditions of an implant; this is attributable to the beneficial influence of the alloying elements and to the better protective properties of the coated passive film.

Avaliação da qualidade da casca dos ovos provenientes de matrizes pesadas com diferentes idades

Foi realizado um estudo sobre qualidade da casca dos ovos incubáveis provenientes de matrizes pesadas com diferentes idades, por meio da avaliação da relação entre peso da casca e peso do ovo e análises de peso específico, espessura, porosidade, resistência e microscopia eletrônica. Os dois tratamentos foram definidos pela idade da matriz, sendo considerados ovos de matrizes novas - 33 semanas - e de matrizes velhas - 63 semanas. Os ovos de matrizes com 33 semanas foram mais leves, e o número de poros por cm² foi menor que o de ovos das aves mais velhas. Ovos de aves com 63 semanas apresentaram menor percentual de casca em relação ao peso do ovo, menor peso específico e menores resistência e espessura da casca. A proporção das membranas da casca em relação à sua espessura total foi maior nas matrizes mais novas. Concluiu-se que ovos de matrizes velhas têm qualidade de casca inferior aos ovos das matrizes novas e que as membranas da casca nos ovos de matrizes novas desempenham papel relevante em sua estrutura.

Influence of Lightweight Aggregates and GRP By-Product Powders on the Properties of Self-Compacting Concretes

Self-compacting lightweight concrete was developed to attain good workability, high compressive strength (at least 50 MPa), minimum cracks, and low specific weight (less than 2000 kg/m3), as well as low elastic modulus (about 30 GPa). The attention was also focused on sustainability of this construction material, which was improved by using in the mixture both GRP industrial by-product as filler and artificial (light expanded clay) or recycled (demolished concrete) as coarse aggregates replacing natural gravel. Satisfactory, if not excellent, results were obtained from the collected experimental data.

Effect of Artificial Aging on the Mechanical Properties of an Aerospace Aluminum Alloy 2024

Aluminum alloys have low specific weight, relatively high strength and high corrosion resistance and are used in many applications. Aluminum Alloy 2024 is widely used for aircraft fuselage structures, owing to its mechanical properties. In this investigation, Aluminum Alloy 2024 was given solid solution treatments at 495, 505, and 515°C followed by quenching in water. It was then artificially aged at 190 and 208°C. Subsequently, hardness measurements, tensile tests as well as impact and fatigue tests were carried out on the heat treated alloys to determine the mechanical properties. The tensile and hardness tests revealed similar mechanical properties for specimens of this alloy that were given the three solid solution treatments. Aluminum Alloy 2024 specimens that were solid solution treated at 515°C and artificially aged at 208°C for 2h exhibited the highest yield and tensile strength. In general, the increase in strength was accompanied by a decrease in ductility. Cyclic fatigue studies were conducted with symmetric tension-compression stresses at room temperature, using a bending-rotation test machine. The alloy solution heat treated at 515°C and aged at 208°C/2h was fatigue tested at constant frequency. The relation between stress amplitude and cycles to failure was established, enabling the fatigue strength to be predicted at more than 7.8x106 cycles, with maximum stress of 110.23 MPa. The fracture surfaces of specimens that failed after fewer cycles showed mainly precipitates and micro voids, whereas specimens that fractured after a higher number of cycles indicated that cracks initiated at the surface. The high cycle fatigue fracture surfaces revealed pores that could be due to precipitates from the matrix.

Low C High Mn Cold Rolled TWIP Steel: Kinetics of Isothermal Recrystallization

The increasing demand, mainly from the automobile industry, for materials which combine high strength, high ductility and low specific weight makes steels with the TWIP (TWinning Induced Plasticity) effect a promising material to meet these requirements. This work aimed to study the kinetics of isothermal recrystallization of a TWIP steel (C-0.06%, Mn-25%, Al-3%, Si-2%, and Ni-1%) after cold rolling. The steel was hot and cold-rolled and then annealed at 700°C with soaking times ranging from 10 to 7200 s. Microstructural analysis was performed using light (LM) and scanning electron microscopy (SEM). Furthermore, quantitative metallography was performed in order to evaluate the recrystallized volume fraction and grain size. A JMAK based model was applied to describe the nucleation grain growth process. The restoration of the steel was also evaluated by microhardness tests. A complete recrystallization after 7200 s at 700°C was observed. It was found that with increasing annealing times, the recrystallized volume fraction also increases, while the nucleation and growth rates decrease, in agreement with the results for plain carbon steels.

W012004 高強度マグネシウム合金のLPSO相における変形特性の結晶塑性解析

Magnesium alloys are considered to be one of the most promising materials in the industry application, for example in the automobile usage, due to their significantly low specific weight. Much study efforts were done mainly from the materials science society to develop strong yet ductile alloys at ambient and elevated temperatures. Recently, a series of new alloys which consist of Mg-TM-RE were developed where TM and RE represent transition metals and rare earth elements, respectiely. The microstructure consists of fine particles of LPSO (long - period - stacking - ordered) phase embedded in a-phase of magnesium. After extrusion of cast alloys, the LPSO phase shows a typical aspect of "kinked" shape and this character is considered to be a key issue in realization of their high strength and ductility. We attempted to understand the mechanism of kink formation in LPSO phase from the view point of non-uniform slip deformation and accumulation of the geometrically necessary dislocations. In this communication, concepts of crystal plasticity analysis for this kind of alloys are introduced and some analysis results for the process of kink deformation in single crystal model of LPSO phase are shown.

Proof test of hybrid shrink fits with ceramic hub

Advanced ceramic machine components are required in many applications because of their specific material properties like high hardness, resistance to chemicals, corrosion and wear, low specific weight etc. The most suitable shaft-hub connection to ceramics is an interference fit assembly because it is free of geometrical notches and transmission of forces takes place in a large area. Such a shrink fit is rated for endurance strength when the stress intensity factor is below the specific value KI0 where no crack growth occurs. The total component suddenly fails, when the stress intensity factor exceeds the KIC value. The load to the press fit during the joining process, caused by the interference of the assembly, could be regulated by ambient conditions. In case of undetected material defects or microcracks in the ceramic and if the stress intensity is below KIC, the ceramic will not fail but a crack could grow. Thus, the joining process only seems to be a proof test. When the load during operation leads to a stress intensity that remains higher than KI0 the crack grows until the whole ceramic component fails. This effect was verified in tests at the Institute for Engineering Design and Industrial Design.

Effects of the carbon nanotube distribution on the macroscopic stiffness of composite materials

Having extremely high stiffness and low specific weight, carbon nanotubes (CNTs) have been known recently as perfect reinforcing fibers in nanotechnology. They can improve the stiffness and strength of nanocomposites by being used as reinforcing elements for example in polymer matrices. The corresponding properties of the fibers and matrix, such as volume fraction and aspect ratio are some of the significant factors in the characterization of mechanical properties of CNT reinforced composites. In recent years, the way in which fibers are distributed inside the matrix, in terms of randomness, has introduced another important factor in characterizing the mechanical properties of such composites. Based on this factor, composites can be classified into two types namely, aligned and randomly distributed. This research has studied the effect of random distribution of fibers in the matrix on the elastic modulus and initial yield stress of the nanocomposite. Therefore, several models of composites, with different distribution of fibers, were considered while holding the volume fractions and aspect ratio constant. As a result, the effect of randomness on the effective modulus of CNT reinforced composites was estimated. The finite element method (FEM), using the MSC.Marc software, was employed to predict the effective modulus of CNT reinforced composites and the results were successfully validated by comparison with the analytical Halpin–Tsai method.

Study on the Difference between Turfy Soil and Normal Peat Soil in China

As the special soil, turfy soil and peat soil in China contained some similar properties with high void ratio, high water content, high organic content, etc. But turfy soil also had properties which difference from peat soil. In this paper, based on the formation of the cause and geological environment and geomorphologic characteristics of geological in the quaternary, took the typical and widespread turfy soil and peat soil regions for example, systematically discussed the material composition and macroscopic and microcosmic structural features, put further research on the physical chemistry mechanical characteristics. Then the come to the conclusion that the essential reason for difference between turfy soil and peat soil were decomposition degree and organic content. The result that worse engineering properties such as higher the moisture content, porosity, compressibility, internal cohesion and the lower specific weight, consolidation coefficient and permeability were due to the lower decomposition degree and higher organic content of turfy soil than peat soil. It can provide reference to the practical projects of turfy soil to distinguish peat soil according to this characteristic.

Service properties of aluminum-matrix precipitation-hardened composite materials and the prospects of their use on the modern structural material market

The methods of production, the structure, and the service properties of aluminum-matrix composite materials (CMs) hardened by high-strength high-module particles are discussed. Owing to high wear resistance, a low specific weight, and a low cost, such CMs are promising for application in many fields of machine building. The need for commercial development of these new functional reinforced CMs with hardening fillers of various natures and fraction compositions (including nanoparticles) as high-temperature and wear-resistant materials instead of traditional materials is grounded.

Functional plasticity of photosynthetic apparatus and its resistance to photoinhibition in Plantago media

Morphological and functional characteristics of Plantago media L. leaves were compared for plants growing at different light regimes on limestone outcrops in Southern Timan (62°45′N, 55°49′E). The plants grown in open areas under exposure to full sunlight had small leaves with low pigment content and high specific leaf weight; these leaves exhibited high photosynthetic capacity and elevated water use efficiency at high irradiance. The maximum photochemical activity of photosystem II (Fv/Fm) in leaves of sun plants remained at the level of about 0.8 throughout the day. The photosynthetic apparatus of sun plants was resistant to excess photosynthetically active radiation, mostly due to non-photochemical quenching of chlorophyll fluorescence (qN). This quenching was promoted by elevated deepoxiation of violaxanthin cycle pigments. Accumulation of zeaxanthin, a photoprotective pigment in sun plant leaves was observed already in the morning hours. The plant leaves grown in the shade of dense herbage were significantly larger than the sun leaves, with pigment content 1.5–2.0 times greater than in sun leaves; these leaves had low qN values and did not need extensive deepoxidation of violaxanthin cycle pigments. The data reveal the morphophysiological plasticity of plantain plants in relation to lighting regime. Environmental conditions can facilitate the formation of the ecotype with photosynthetic apparatus resistant to photoinhibition. Owing to this adjustment, hoary plantain plants are capable of surviving in ecotopes with high insolation.

Experimental Assessment of a Modal-Based Multi-Parameter Method for Locating Damage in Composite Laminates

The low specific weight of composite materials, together with their excellent mechanical properties, make them suitable to be widely used in many modern engineering structures. However, composite materials are quite sensitive to impacts: a specific kind of damage, called Barely Visible Impact Damage (BVID), may occur, constituting an unsafe failure of difficult assessment. In the past few years several methods have been developed aiming at assessing this type of damage. In this paper, a vibration-based technique that combines both the natural frequencies and the modal damping factors as damage sensitive features is tested for locating impact damage in carbon fibre reinforced laminates. The method is intended to be used for locating damage in real laminated composite structures that undergo in-service impacts, such as an airplane’s fuselage or wings. Assessing a minimum of one response coordinate is the strict requirement during each inspection, because it uses the dynamic global parameters of the structure as damage features. This is possible because the method assumes that, at least for BVID, the mode shapes remain practically unchanged. The theory is summarized and the method is tested using experimental setups where damage is introduced at different locations. Additionally, the hypothesis that different damage morphologies on composite materials have different contributions to the damage features is addressed.

Combined Al‐ plus F‐treatment of Ti‐alloys for improved behaviour at elevated temperatures

AbstractTitanium is a widely used structural material because of its low specific weight, good mechanical properties and excellent corrosion resistance at ambient temperature. As a result of increased oxidation at elevated temperatures and environmental embrittlement the maximum operation temperature of standard Ti‐alloys is only about 600 °C. The oxidation behaviour can be improved by different methods, e.g. coatings. This leads to an improvement which is, however, often limited. The combination of Al‐enrichment in the sub surface zone, so that a TiAl‐layer is formed, plus F‐treatment gives impressively good results because a protective alumina scale is formed due to the fluorine effect. This alumina scale prevents oxygen inward diffusion which causes embrittlement and protects the material against environmental attack. The procedure is applied to alloys with a very low Al‐content or even no Al at all. In the paper results of oxidation tests of α‐Ti without any treatment, with Al‐treatment and with a combination of Al‐ + F‐treatment are presented. Aluminium was diffused into the samples by a powder pack process. Fluorine was applied by a liquid phase process. The formation of an alumina scale on treated samples was revealed by post experimental investigations. The results are discussed referring to the fluorine effect model for TiAl‐alloys.

Procedure for Making a Cement Mixture with Recycled Plastics Applicable to the Manufacture of Building Elements

This review is about the Argentina Patent number AR 047617B1 published on August 12, 2008. Its inventors are Gaggino Rosana, Arguello Ricardo and Berretta Horacio. The topic is a procedure to make new constructive elements (bricks and plates) by using these recycled plastics: - Low-density polyethylene (LDPE), recycled out of discarded soft drink packs. - Polyethylene-terephthalate (PET), recycled out of discarded soft drink bottles. - Several plastics, from the printed films used, like packages of candies (remainder of production plant by faults of inked or thickness). These conveniently grounded plastics were taken as aggregates to be mixed with Normal Portland cement, replacing heavy sand and gravel habitually used in these mixtures. These materials can be used in constructive elements such as bricks and plates for economic houses closures or traditional construction. The developed constructive elements offer high thermal insulation, so they can be used in closures with a smaller thickness than conventional bricks and blocks. Besides, they have a lower specific weight than these traditional constructive elements. Recycling means lowering costs, making part of the environment contaminating waste useful and providing the unemployed and/or unqualified work force with jobs through uncomplicated technologies. Therefore, it has an economical as well as ecological and socially concerned proposal.

Isotopic analysis of cyanobacterial nitrogen fixation associated with subarctic lichen and bryophyte species

Dinitrogen fixation by cyanobacteria is of particular importance for the nutrient economy of cold biomes, constituting the main pathway for new N supplies to tundra ecosystems. It is prevalent in cyanobacterial colonies on bryophytes and in obligate associations within cyanolichens. Recent studies, applying interspecific variation in plant functional traits to upscale species effects on ecosystems, have all but neglected cryptogams and their association with cyanobacteria. Here we looked for species-specific patterns that determine cryptogam-mediated rates of N2 fixation in the Subarctic. We hypothesised a contrast in N2 fixation rates (1) between the structurally and physiologically different lichens and bryophytes, and (2) within bryophytes based on their respective plant functional types. Throughout the survey we supplied 15N-labelled N2 gas to quantify fixation rates for monospecific moss, liverwort and lichen turfs. We sampled fifteen species in a design that captures spatial and temporal variations during the growing season in Abisko region, Sweden. We measured N2 fixation potential of each turf in a common environment and in its field sampling site, in order to embrace both comparativeness and realism. Cyanolichens and bryophytes differed significantly in their cyanobacterial N2 fixation capacity, which was not driven by microhabitat characteristics, but rather by morphology and physiology. Cyanolichens were much more prominent fixers than bryophytes per unit dry weight, but not per unit area due to their low specific thallus weight. Mosses did not exhibit consistent differences in N2 fixation rates across species and functional types. Liverworts did not fix detectable amounts of N2. Despite the very high rates of N2 fixation associated with cyanolichens, large cover of mosses per unit area at the landscape scale compensates for their lower fixation rates, thereby probably making them the primary regional atmospheric nitrogen sink.

Material data identification to model the single point incremental forming process

In this study, the Single Point Incremental Forming process (SPIF) is applied on a specific aluminium alloy used in the aerospace industry since this technique and material combine a low specific weight, high strength and stiffness properties and high strain levels. To be able to optimize the process, a model and its material parameters are required. It was noticed that a simple isotropic hardening model was not sufficient to provide an accurate tool force prediction [1]. Therefore an elasto-plastic law with a mixed isotropic-kinematic hardening is investigated. The inverse method coupled with the Finite Element (FE) code: “Lagamine” [2] is used to fit the material data of this complex law. In order to validate the model and the material data, a Line test and a Cone test are used.

Effect of using organic microminerals on performance and external quality of eggs of commercial laying hens at the end of laying

The objective of the present study was to evaluate the effect of using microminerals in organic form on the performance and quality of eggs from commercial laying hens at the end of laying. Four hundred and eighty Hisex strain hens, 72 to 80 weeks of age, were used. A randomized complete design was used, with six replications and 16 birds for each experimental unit. Five diets were evaluated: basal feed supplemented with all microminerals in inorganic form (control); basal feed supplemented with 50% microminerals zinc (Zn) + manganese (Mn) + copper (Cu) in organic form and 50% in inorganic form; basal feed supplemented with 50% zinc in organic form and 50% in inorganic form; basal feed supplemented with 50% manganese in organic form and 50% in inorganic form; and basal feed supplemented with 50% copper in organic form and 50% in inorganic form. There was no effect of diets on egg production, feed intake, food conversion and egg shell percentage and thickness. Birds fed basal feed supplemented only with zinc or manganese in organic form produced eggs with lower specific weight. The use of basal feed supplemented with copper in organic form has minimized egg loss. However, the best results (lower egg loss, higher specific weight and higher weight of eggs) were obtained with the basal feed supplemented with microminerals Zn + Mn + Cu in organic form and, therefore, it is recommended for feeding of commercial laying at the end of laying.

CARACTERÍSTICAS DO ENCRUAMENTO DO AÇO TWIP ALTO Mn E BAIXO CARBONO LAMINADO A FRIO E RECOZIDO

There is a current need for the automotive industry for materials that combine high formability, high strength and low specific weight in order to reduce fuel consumption and increase passenger safety. In this context, appears the TWIP steel (TWinning Induced Plasticity), defined as a steel with high content of manganese and, yet, silicon and aluminum (2% to 4%) in its composition. Its main feature is the formation of twining under stress. In this study, it was investigated how the characteristics of hardening work of the steel C-0,06, Mn-25, Al-3, Si-2, Ni-1, with TWIP effect, hot and cold rolling and annealing at temperatures varying between 600°C and 850°C, influences their mechanical properties. This research used optical micrography and scanning electron microscopy (SEM) for assessment of grain size and volume fraction of recrystallized grains. To complement this study, tensile tests were performed. The hardening work study uses the approach of Hollomon associated with the Considere criterion. The sample annealing to 850°C shows a work hardening exponent of 0.55, 66% of total elongation and maximum strength of 700 MPa