bluuebunny/crossref_metadata_2025 huggingface dataset:
Manufacturing of Tribologically Optimized Surfaces for Powertrain Applications
Authors: Schubert Andreas , Steinert Philipp , Schmidt Torsten , Hackert-Oschätzchen Matthias
Published: November 2012

Among the major interests in powertrain development are the reduction of frictional losses and service life extension from improved wear resistance. Surface finishing and deterministic microstructuring have been shown to be effective methods in improving the tribological properties of sliding contacts such as bearings and cylinder liners. This is due to their acting as micro pressure-chambers and as wear debris traps. In this work, tribometric ring-on-disc tests were performed in order to evaluate the influence of surface structure − namely, the microstructure geometry and layout − on the frictional behavior of lubricated surfaces. The material combination bronze against steel as typically used in powertrain applications was investigated. The surface structures where machined using electrochemical machining by closed electrolytic free jet (Jet-ECM). It was determined that microstructuring reduced the friction coefficient by up to 45 % in the hydrodynamic regime under loads and speeds found in automotive components. The friction measurements showed that microstructures with low aspect ratios result in the least friction. In addition to the tribological investigations, the process capabilities and implementability in serial production of two surface microstructure fabrication processes: Jet-ECM and a newly developed, hybrid roller micro-embossing and burnishing process were evaluated and contrasted. It was shown that both fabrication methods can attain high structure quality.
Novel Measuring Principle of Pitch Deviation Evaluated through Double-Flank Gear Rolling Test with Rack Probe
Authors: Tang Jie , Shi Zhao Yao , Fang Zhi Qiang
Published: November 2012

High-speed inspection of individual deviations (profile, helix, pitch) in mass-produced gear workshops is a problem. This paper introduces the measuring principle of pitch deviations evaluated through the double-flank gear rolling test for fast inspection in gear workshops, during which the displacement of rack probe in radial & tangential direction is measured when the work-piece is meshing with the rack probe in double-flank.
Micro-Milling of Fully Sintered ZrO2 Ceramics with Diamond Coated End Mills
Authors: Bian Rong , Ferraris Eleonora , Qian Jun , Reynaerts Dominiek , Li Liang , He Ning
Published: November 2012

This work presents an experimental investigation on micro-milling of fully sintered Zirconia (ZrO2) with CVD diamond coated end mills. The experiments were conducted on a Kern MMP 2522 micro-milling centre. Diamond coated WC micro end mills with stiff geometry, are employed. Effects of cutting parameters on surface quality were investigated by means of a mixed full factorial experimental design. Surface roughness was measured by a Talysurf 120L profilometer. Surface topography was examined using a scanning electron microscope. The results show that a smaller feed rate was apt to result lower surface roughness. With the increase of cutting length, brittle damages were observed in some tests.
Numerical Simulation of Fatigue Behavior of Honeycomb Sandwich Panels
Authors: Lu Jie , Zou Guang Ping , Yang Peng Fei
Published: November 2012

In this study, based on Goodman stress correction algorithm, four point bending fatigue behavior of brazed steel honeycomb sandwich panels at room temperature is simulated using Fe-safe emulation module. The cyclic load was sinusoidal with a frequency f= 10 Hz. The residual life and security coefficient are given in the condition of design fatigue lifetime of 106 cycles. The results show that, in the local deformation, local maximum deformation occurs in the core wall under the load region, indicate that this region is the failure region of fatigue. And the residual life of the core wall in this region is less because of local stress concentration, the probability of failure becomes high, while the residual life in the region far away from the mid-span is high.
Material Properties and Fatigue Safety Evaluation of Old Metal Bridges
Authors: Wang Chun Sheng , Sheng Hai Jun , Hu Jing Yu , Yan Sheng Long , Duan Lan
Published: November 2012

Lanzhou Zhongshan Bridge, which is located in the center of Lanzhou city, is a rivet truss bridge built in 1909. It is the first iron bridge over the Yellow River as well as a national cultural relic. An original steel angel cut off from Lanzhou Zhongshan Bridge was used to carry out a series of tests including material mechanics, fracture and fatigue property. Based on the test results, the fatigue and fracture safety was evaluated during the bridge remaining service life. Whats more, remaining service life of Lanzhou Zhongshan Bridge was calculated and found that the trucks weight more than 120 kN should be limited to ensure the safety.
The Role of Grain Size on Deformation of 316H Austenitic Stainless Steel
Authors: Mahalingam S. , Flewitt Peter E.J. , Shterenlikht A.
Published: November 2012

The polycrystalline high purity 316H austenitic stainless steel has been thermo-mechanically treated to produce material with two layers of grain size, one of coarser and the other of finer grains. Small three point bend specimens containing a notch positioned in either the coarser or finer layer have been tested at a constant strain rate and a temperature of -196°C. The results are discussed with respect to the effect of grain size on the underlying deformation between the two layers of different grain size.
Study on the Pin-Load Distribution of Multiple-Bolted Composite to Metal Joints
Authors: Liu Xiang Dong , Li Ya Zhi , Yao Zhen Hua , Shu Huai
Published: November 2012

The experiment and finite element analysis were made to determine the pin-load distribution of multiple countersunk bolted single-lap joints. In the experiment, the pin-load fractions were evaluated indirectly by the lap-sheet surface strains collected from a few rows of strain gages. The joint strains and pin-load distribution were also obtained directly in the finite element analysis. The calculated strains correlated well with the experiment. Nevertheless, the pin-load fraction results of the both techniques are quite different. The further analysis revealed that the procedure of transforming the measured strains into pin loads is not reliable, since the intrinsic additional bending had not been taken into account. Therefore the appropriate way to determine the pin-load distribution should be the numerical analysis validated by the strain measurement. The another attempt showed that the pin-load distribution can be evaluated by the finite element modeling of two-dimensional shells and beams as well with satisfied accuracy.
A Novel Testing Method for Measuring Through-Thickness Properties of Thick Composite Laminates
Authors: Li Yu Tu , Zheng Xi Tao , Luo Gui
Published: November 2012

The investigation was concentrated on the through-thickness properties of thick-composite laminates, and the development of a novel test method and several specimens with two different shapes and three to four different sizes. The experiments were performed on thick composite specimens; and all through-thickness mechanical properties under compressive and tensile loading with their corresponding failure mechanisms were determined. Overall, the configuration of specimens and test method in this paper are efficient in obtaining the through-thickness properties of thick-composite laminates.
Interfacial Shear Strength of Carbon Fiber Reinforced Polypropylene
Authors: Takemura Kenichi , Katogi Hideaki
Published: November 2012

In this study, interfacial shear strength of carbon fiber reinforced polypropylene were investigated. Two kinds of reinforcements are used. One is non-treated carbon fiber, another is acetone-treated carbon fiber. And two kinds of matrices are used. One is non-treated polypropylene, another is maleic anhydride-polypropylene. Three point flexural tests and micro debonding tests are conducted. As a result, following conclusions are obtained. Acetone treatment and maleic anhydride are effective to the adhesives on the surface between fiber and matrix. But simultaneous treatments are not effective. The shear strength is not dependent on fiber embedded length. The contact angle and fracture load are dependent on fiber embedded length. The interfacial strength is dependent on the contact angle. As the contact angle increases, the interfacial strength increases.
Load and Environmental Effects on the Corrosion Behavior of a Ti6Al4V Alloy
Authors: Baragetti Sergio , Medolago Alessandro
Published: November 2012

This paper focuses on the static mechanical behavior of Ti-6Al-4V titanium alloy when exposed to several aggressive environments. Flat samples, with very light notches (i.e.Kt= 1.16), were tested under static loads, in inert environment and aggressive solutions: the samples gage sections were exposed to air and immerged in a NaCl solution (3.5%) and in a methanol solution (95%). The results of this experimental tests were analyzed and then compared with previous data coming from fatigue tests, carried out in paraffin oil, air, 3.5 wt.% NaCl, and in a methanol solution (95%), with the intent to decouple the effect of the alternating load and of the aggressive environment.
Fatigue Crack Nucleation and Growth Mechanisms for Ti6Al4V in Different Environments
Authors: Baragetti Sergio , Foglia Cristian , Gerosa Riccardo
Published: November 2012

In this work fracture surfaces of Ti-6Al-4V flat samples subjected to fatigue tests were examined by means of a scanning electron microscope. SEM analyses allowed to observe in detail the morphology of the fracture surfaces, in order to identify the crack nucleation zones and the crack growth mechanisms accurately. The surface morphologies were examined in order to compare the alloy behavior, considering different test environments and stress concentration factor values (Kt). The analyses resulted in the observation of different corrosion fatigue micro-mechanisms related to the stress concentration factor and to the test environment.
Application of the Mesh Superposition Technique to the Study of Delaminations in Composites Thin Plates
Authors: Sellitto Andrea , Borrelli R. , Caputo Francesco , Riccio Aniello , Scaramuzzino Francesco
Published: November 2012

Laminated composite structures are increasingly finding more applications in various fields thanks to their lower weight if compared with other materials of the same strength. Nevertheless, composites thin plates show a critical behavior in terms of damage propagation mechanisms when subjected to (low velocity) impact. Indeed they tend to produce delaminations which can be hardly detected by optical inspections and can affect the global load carrying capability, leading to a premature structural collapse. The aim of this paper is to assess the capabilities of the Davies-Zhang approach (introduced in 1994 and aimed to the estimation of both the delamination initiation impact load and the size of the impact induced delaminations) by using a multiscale FE model based on the mesh superposition technique. Indeed the impact area has been modeled layer-wise with an element per layer while the rest of the structure has been modeled at laminate level by layered elements by means of a homogenization approach for the determination of the equivalent laminate material properties. The impact induced delamination area has been determined by adopting stress-based criteria. The results (in terms of delamination initiation impact force and delamination size) have been compared to the ones obtained by adopting the Davies-Zhang approach.
Micro-Scale Cantilever Testing of Linear Elastic and Elastic-Plastic Materials
Authors: Darnbrough J.E. , Mahalingam S. , Flewitt Peter E.J.
Published: November 2012

t is increasingly a requirement to be able to determine the mechanical properties of materials: (i) at the micro-scale, (ii) that are in the form of surface coatings and (iii) that have nanoscale microstructures. As a consequence micro-scale testing is an important tool that has been developed to aid the evaluation of the mechanical properties of such materials. In this work cantilever beam specimens (typically 2μm by 2μm by 10μm in size) have been prepared by gallium ion milling and then deformed in-situ within a FEI Helios Dual Beam workstation. The latter is achieved using a force probe with a geometry suitable for loading the micro-scale test specimens. Thus force and displacement can be measured together with observing the deformation and fracture of the individual specimens. This paper considers the evaluation of the mechanical properties in particular elastic modulus, yield strength and fracture strength of materials that result in relatively large deflections to the micro-scale cantilever beams. Two materials are considered the first is linear elastic single crystal silicon and the other elastic-plastic nanocrystalline (nc) nickel. The results are discussed with respect to the reproducibility of this method of mechanical testing and the evaluated properties are compared with those derived by alternative procedures.
Mechanical Characteristics of Bamboo
Authors: Shioya Tadashi , Asahina Toshikatsu
Published: November 2012

Fracture toughness, stress-strain relation and the damping characteristics of bamboo are investigated. The fracture toughness of bamboo in tearing along the longitudinal direction is measured by the use of newly devised apparatus in which the crack opening displacement is controlled in a constant velocity and a quasi-steady extension of the crack is maintained. The stress-strain relation of bamboo is examined in a reversible elastic range using a conventional tensile test in the longitudinal direction. Repeated tensile loading tests show that the stress-strain relation has a strong non-linear hysteresis and that it converses to a steady loop. The damping of bamboo is measured by the use of inverted torsion pendulum apparatus. The specimen is taken so that damping of twisting longitudinal bar is measured. The damping coefficient of bamboo is much larger than that of metals. The mechanical properties of bamboo are examined in terms of water concentration and fiber density in the bamboo.
Effects of Strain and Strain Rate on the Abrasive Wear Behavior of High Manganese Austenitic Steel
Authors: Lindroos Matti , Kuokkala Veli Tapani , Lehtovaara Arto , Kivikytö-Reponen Päivi
Published: November 2012

An abrasive wear analysis of the hardened surface layer in high austenitic manganese steel is presented to determine the effects of plastic strain and strain rate. The pre-deformation levels used in this study represent the typical surface layers resulting from the abrasive contact of Hadfield type steels. The effect of dynamic loading used in the pre-straining is accounted for alongside with various plastic strain levels. A friction study of the surface was included to determine the localization of work hardening and the ability of the microstructure to resist abrasion.
The Study of the Tribological Properties of One-Process and Two-Process Textures after Vapour Blasting and Lapping Using Pin-on-Disc Tests
Authors: Dzierwa Andrzej , Pawlus Pawel , Zelasko Wieslaw , Reizer Rafal
Published: November 2012

Wear tests were conducted using a pin-on-disc tester. In the experiment, a steel disc of hardness 40 HRC was put in contact with a steel pin of hardness 64 HRC with spherical end. Disc samples were prepared in order to obtain very similar values of the Sq parameter of one-process and two-process isotropic surfaces. Height of one–process disc surfaces, characterized by the Sq parameter was in the range 0.5 – 6 µm, but of two-process textures 1- 4.5 µm. Dry and lubricated tests, using different contact conditions were carried out. During testing, the friction force was monitored as a function of time. Wear of disc was measured after the test using white light interferometer. Tests under boundary lubrication condition were done using L-AN 46 oil.
Limit Plastic State of Notched Stripes with Stress State Dependent Properties
Authors: Lomakin E.V. , Melnikov A.M.
Published: November 2012

Behavior of isotropic media with stress state dependent plastic properties is studied in this paper. One of the possible general approaches to the formulation of constitutive equations of these materials is demonstrated. The derived equations are applied to the problem of tension of a notched stripe under plane stress conditions. Some general equations of stress state dependence of plastic properties of materials that can be used with large variety of models are derived in the case of hyperbolic constitutive equations. Theoretical results are compared with FEM solution of this problem for the Drucker-Prager material model.
Estimation of Thermal Boundary Conditions by Gradient Based and Genetic Algorythms
Authors: Felde Imre
Published: November 2012

The prediction of third type boundary conditions occurring during heat treatment processes is an essential requirement for characterization of heat transfer phenomena. In this work, the performance of four optimization techniques is studied. These models are the Conjugate Gradient Method, the Levenberg-Marquardt Method, the Simplex method and the NSGA II algorithm. The models are used to estimate the heat transfer coefficient during transient heat transfer. The performance of the optimization methods is demonstrated using numerical techniques.
Application of Risk-Informed Inspection Strategy to Improve the Lifetime and Efficiency of Cleaning Pigs
Authors: Fótos R. , Koncsik Zsuzsanna , Lukács János
Published: November 2012

The aim of the research work was to analyze the operation of cleaning pigs, in natural gas transportation pipelines from point of view of risk-informed in-service inspection. During the analysis, the main factors considered were the stresses (mechanical, thermal and environmental) and loads, which have effect on cleaning pigs during its operation. The possible damage mechanisms were analyzed which can occur due to their consequences and qualitative probability analysis was performed on the basis of the available information.
Laser Cutting of Small Diameter Nitinol Tube
Authors: Nagy Péter , Dobránszky János
Published: November 2012

In this article the complex research and development project of the laser cutting micromachining of nitinol alloys are shown. The laser cutting parameters of the 1.04 mm inner diameter and 0.1 mm wall thickness nitinol tubes are also shown. The laser cutting parameters of micromachining and the cut surface of nitinol tubes are summarized when 3 mJ pulse energy, 0.02 ms pulse duration, 6 bar Ar gas pressure, 3000 Hz frequency, 10 mm/s rotation speed and 5 mm/s2 speed-up were used. The effect of the laser cutting to the raw material is characterized by microstructural and micromechanical examinations. A detailed description is given of the energy input by laser beam machining. The pulse and the impact of the applied pressure parameters of the gas to the raw material are also shown.
Porous Metal-Organic Framework Materials: Microwave Assisted Synthesis and Oxidative Catalytic Tests
Authors: Barbosa André D.S. , Balula Salete S. , Paz Filipe A. Almeida , de Castro Baltazar , Cunha-Silva Luís
Published: November 2012

Metal-Organic Framework Materials MIL‑101(Cr) ([Cr3X(H2O)2O(bdc)3]∙n(H2O), where X− = F− or OH−, n ≈ 25 and H2bdc stands for 1,4-benzene-dicarboxylic acid] and MOF‑5(Zn) [Zn4O(bdc)3] were prepared by hydrothermal or solvothermal methods as well as Microwave‑Assisted Synthesis (MWAS), for which the detailed synthetic parameters were optimized. The crystal structures were confirmed by powder X-ray diffraction and the materials were further characterized by FT‑IR absorption spectroscopy. MIL‑101(Cr) and MOF‑5(Zn) showed weak catalytic activity in the oxidation of terpene, thiophene and cis-cyclooctene. Reasonable catalytic activity was observed for MOF-5(Zn) in the epoxidation of cis-cyclooctene and a 100 % of selectivity was observed for the epoxide. The structural stability of the materials was tested under the employed catalytic medium for oxidation reactions. MOF-5(Zn) revealed a remarkable structural stability at high temperature and also in the presence of high oxidant amounts.
Strap Repair Optimization by Using Embedded Patches
Authors: Pinto Arnaldo M.G. , Campilho Raul D.S.G. , Mendes Isabel R. , Magalhães A.G. , Baptista A.P.M.
Published: November 2012

Adhesively-bonded techniques offer an attractive option for repair of aluminium structures, and currently there are three widely used configurations, i.e., single-strap (SS), double-strap (DS) and scarf repairs. SS and DS repairs are straightforward to execute but stresses in the adhesive layer peak at the ends of the overlap. DS repairs additionally require both sides of the damaged structures to be reachable for repair, which is often not possible. In these repair configurations, some limitations emerge such as the weight, aerodynamic performance and aesthetics. The scarf repair is more complex to fabricate but stresses are more uniform along the adhesive bondline. Few studies of SS and DS repairs with embedded patches, such that these are completely flush with the adherends, are available in the literature. Furthermore, no data is available about the effects of geometrical and material parameters (e.g. the Young’s modulus of adhesive, E) on the mechanical behaviour optimization of embedded repairs. For this purpose, in this work standard SS and DD repairs, and also with embedded patches in the adherends, were tested under tension to allow the geometry optimization, by varying the overlap length (LO), thus allowing the maximization of the repairs strength. The influence of the patch embedding technique, showing notorious advantages such as aerodynamic or aesthetics, was compared in strength with standard strap repairs, for the viability analysis of its implementation. As a result of this work, some conclusions were drawn for the design optimization of bonded repairs on aluminium structures.
First Principles Study of Copper Sulfides (for Applications as Photoconductors)
Authors: Ferreira Jorge A. , Braga M. Helena
Published: November 2012

The Tetrahedrite’s family constitutes a complete solid-solution series, and is among the most frequent complex sulfides in Nature. This kind of structure can be generically expressed by the composition, Cu12Sb4S13. We have calculated the electronic band structure of Cu12Sb4S13 and Ag6Cu6Sb4S13 (with band gaps of 1.24 and 1.20 eV, respectively) to demonstrate that different elements occupying certain sites of the crystal structure will make a difference in what concerns the conduction process in Tetrahedrites. We will use this effect and ab initio calculations to show that the electronic properties of these compounds make them promising candidates as solar cells photovoltaic materials since not only they possess a direct band gap but their energy falls within the range of energies of photovoltaics. Moreover, we can optimize these properties by doping and substituting ions furthermore. Mechanical properties were also calculated for both compounds and will be compared.
Magnetic and Piezoelectric Properties of the Fe3+ Doped PLZT Electroceramics
Authors: Kozielski Lucjan , Płońska M.
Published: November 2012

For the growing interest in developing of more attractive multiferroic and magnetoelectric ceramics an alternative is a double-doped Pb(Zr1-xTix)O3- material with trivalent lanthanum and iron ions. Such material has a structure based on ABO3 perovskite and properties depending on the chemical and structural composition. In the present work the results of the preparation and characterization of Fe3+- modified 9/65/35 PLZT ceramics have been reported. Two samples of Pb0,91(La1-zFez)0,09(Zr0,65Ti0,35)0,9775O3 ceramics, for different Fe ions concentration (z = 0,0 and 0,5 at.%), were prepared from the MOM derived powders and sintered by the hot uniaxial pressing methods. To analyze the obtained ceramics properties the XRD, SEM and also application oriented dielectric and magnetic measurements were performed. The Fe3+ substitution at the La-site of PLZT has shown many interesting and unusual dielectric, piezoelectric and magnetic properties. The obtained material was proposed to implement into Piezoelectric Transformer structure to change gain characteristics proportionally to magnetic field intensity.
Synthesis of Functional Ceramic Materials for Application in 2 kW Stationary SOFC Stacks
Authors: Martinelli Antonio E. , Macedo Daniel A. , Cesário Moisés R. , Cela Beatriz , Nicodemo Juliana P. , Paskocimas Carlos A. , de Araújo Melo Dulce Maria , Nascimento Rubens M.
Published: November 2012

This paper presents an overview of recent advances in the synthesis and preparation of solid oxide fuel cells (SOFCs) functional ceramic materials, focusing on low-/intermediary-temperature SOFCs. Novel synthesis processes for oxygen ion-conducting and mixed electronic and ionic conductors, fundamental to reduce the operating temperature of SOFCs were studied. Ni-Ce0.9Gd0.1O1.95 (Ni-CGO) anodes were successfully synthesized by the so called “one step synthesis”. La0.5Sr0.5Co0.8Fe0.2O3 (LSCF), Ce0.8Sm0.2O1.9 (SDC) and their mixture were produced as a cobaltite-based composite cathode by mixing powders synthesized by microwave-assisted combustion and the modified polymeric precursor method, respectively. Preliminary electrochemical activity tests with the synthesized electrodes were performed in electrolyte-supported SOFCs using commercially available 200 µm thick yttria stabilized zirconia (8YSZ) as electrolyte. The maximum power density of 52 mW/cm2 was reached at 850 °C. This result can be further improved replacing thick YSZ electrolytes by doped-ceria thin films, aiming at operation temperatures of 500–800 °C and power densities as high as 800 mW/cm2. The assembling of anode-supported cells with the configuration Ni-CGO/CGO (10 µm thickness)/LSCF-SDC are for applications in 2 kW stacks are currently under way.
Durability of Biodegradable Internal Fixation Plates
Authors: Szaraniec Barbara
Published: November 2012

In this work prototypes of internal fixation plates of acetabular fractures were developed and manufactured. The injection moulding was used to produce polymeric and composite samples. The plates and paddle-like beam samples made of polylactide and the polymer composite modified with 7 wt. % of tricalcium phosphate were produced. The samples were incubated in physiological fluids for 8 months. During the in vitro tests their durability and mechanical properties were determined. In comparison to the pure polylactide the addition of TCP accelerated degradation process. The degradation of the composite started after about 100 days of incubation, whereas the initial polymer began to degrade about 50 days later. The obtained biodegradable plates revealed sufficient mechanical properties for internal fixation of acetabular fractures for bone joining.
Tetraethylortossilicate Plasma Thin Film with Hydrophilic and Hydrophobic Characteristics: Use on Passive Mixers
Authors: Hernandez Leonardo F. , Lima Roberto R. , Pecoraro Edson , Rosim-Fachini Esteban , da Silva Maria L.P.
Published: November 2012

This work aims to obtain plasma thin film composites with hydrophobic/hydrophilic alternated regions, which are useful for the production of miniaturized mixers. These regions were acquired by two different strategies: either the codeposition of TEOS and HFE plasma thin films or the exposition of TEOS plasma films to ultraviolet radiation (UVA and UVC). These films were characterized by several chemical and physical techniques. The refractive indexes vary from 1.4 to 1.7; infrared and photoelectron spectroscopy detect Si-O-Si and CHn species. Silicone-like structures with high or low number of amorphous carbon microparticles and with fluorinated organic clusters were produced. Cluster dimensions were in the 1-5 mm range and they are made of graphite or COF (carbon/oxygen/fluorine) compounds. Scanning electron and optical microscopy showed rough surfaces. Water contact angles were 90º; however, for TEOS films that value changed after 6 hr of UVC exposure. Moreover, after UV exposure, organic polar compounds could be adsorbed in those films and water was not. The passive mixer performance was simulated using the FemLab 3.2® program and was tested with 20 nm thick films on a silicon wafer, showing the capacity of these films to be used in such devices.
Wettability and Nanotribological Response of Silicon Surfaces Functionalized by Ion Implantation
Authors: Nunes Bruno , Magalhães Sergio , Franco Nuno , Alves Eduardo , Serro Ana Paula , Colaço Rogerio
Published: November 2012

Aiming to improve the nanotribological response of Si-based materials we implanted silicon wafers with different fluences of iron ions (up to 2x1017 cm-2). Implantation was followed by annealing treatments at temperatures from 550°C to 1000°C. The implanted surfaces were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and wettability tests. Then, samples were submitted to AFM-based nanowear tests. We observe an increase of both hidrophobicity and and wear resistance of the implanted silicon, indicating that ion implantation of Si can be a route to be deeper explored in what concerns tribomechanical improvement of Si.
A Method for the Evaluation of Femoral Head Trabecular Bone Compressive Properties
Authors: Aleixo I. , Vale A.C. , Lúcio M. , Amaral P.M. , Rosa Luis Guerra , Caetano-Lopes J. , Rodrigues A. , Canhão H. , Fonseca J.E. , Vaz M. Fatima
Published: November 2012

We addressed the importance of defining a mechanical testing methodology for the compression of human trabecular bone specimens. In fact, currently there are several protocols to test trabecular bone, but a single, standard and validate method has not been accepted yet. In our work, human femoral epiphyses collected from patients with osteoporosis (fragility fractures) and hip osteoarthritis, submitted to total hip replacement surgery, were used. The aims of our work were to develop a mechanical testing methodology for the compression of trabecular bone specimens taking into account the optimization of bone extrinsic and intrinsic variables, in order to establish a patient bone sample database with clinical, structural and mechanical information. Extrinsic variables, such as the effect of specimen preparation, with particular focus on the dimensions of test specimens, and others associated with the compression test, such as the method employed to determine specimen deformation, and hence strain, were evaluated. Also, a new device used to withhold the specimens was developed and tested by the present authors. Although each specimen showed a unique behaviour, even when comparing compression curves between patients from the same disease group, implicating additional complexity and difficulty in the data analysis, the authors managed to assemble the results in two groups related with a possible difference in the deformation mechanisms occurring after yielding.
Effect of Mud Acid on Portland-Aqueous Polyurethane Composites to Oil Well Cementing
Authors: da Nóbrega Ana Cecilia Vieira , Martinelli Antonio Eduardo , de Araújo Melo Dulce Maria , de Freitas Melo Marcus Antonio , de Oliveira Freitas Julio Cezar , de Oliveira Filipe Silva
Published: November 2012

Mud acid attack of 14 lbm/gal Portland cement composites with 15 % of nonionic aqueous polyurethane was investigated. Plain Portland hardened cement slurries showed the loss of weight around 23 %. The addition of aqueous polyurethane resulted in longer durability, with reduction around 87 % on the loss of weight without influence on the compressive strength or fratographic. The mechanism is related with the decreased porosity and permeability due to the polymeric net formation on the bulk and minor quantities of Ca+2, preferentially leached to the acidic solution. In this way, Portland-aqueous polyurethane composites are possible solutions to oil well cementing submitted to steam injection and mud acid acidizing operations.
Nanostructured Thin Coatings from Chitosan and an Elastin-Like Recombinamer with Acute Stimuli-Responsive Behavior
Authors: Costa Rui R. , Ribeiro Artur J. , Rodríguez-Cabello José C. , Mano João F.
Published: November 2012

In the present work, chitosan (CHI) and elastin-like recombinamers (ELRs) were used to conceive nanostructured thin films driven by sequential electrostatic layer-by-layer (LbL), a simple and versatile technique that discards the use of harmful reagents. Two similar ELRs were engineered to contain negatively charged aminoacids and organized and a single monoblock or a triblock. The buildup of the films was monitored in real time using a quartz-crystal microbalance with dissipation monitoring (QCM-D). Wettability transitions were observed from a moderate hydrophobic surface to an extremely wettable upon increasing the temperature to 50 °C, accompanied by topography changes at the nanoscale as assessed by atomic force microscopy (AFM). Furthermore, the dependence on time for the surface molecular rearrangement was studied for the films with each ELR. The potential of this technology may stimulate the development of devices and biomaterials for biomedical applications in the near future, such as surfaces with tunable and patterned cell adhesion, while the use of ELRs will allow developing polypeptides with biological significance.
Fibre Reinforced Thermoplastic Composite Rods
Authors: Kling Veronika , Rana Sohel , Fangueiro Raul
Published: November 2012

The present investigation is concerned with the development of fibre reinforced thermoplastic composite rods using braiding process. An innovative technique has been developed to produce composite rods with outer braided layer of polyester fibres and axially reinforced with high performance glass fibres. Polypropylene filaments which were introduced in to the core along with the glass fibres during the braiding process formed the thermoplastic matrix upon melting. A special mould has been designed for uniform application of heat and pressure during the consolidation of the composite rods as well as for the alignment of core fibres. The cross-section of composite rods was characterized with help of optical microscopy in order to see the distribution of core fibres and matrix. The effect of amount of glass fibres on the mechanical properties (tensile and flexural) of composite rods has been investigated and discussed.
Influence of the Parameters of Formulation on the Chemical Activity of Admixtures in Mortars
Authors: Boudchicha Abdelaziz , Cheikh Zouaoui Mustapha , Gallias Jean Louis
Published: November 2012

To analyze the chemical activity of admixture in mortars, we used a methodology which guarantees that the obtained mixtures still have a volume of the flexible phase and an initial porosity constant. Then, only the clean chemical effect of the admixture is taken into account in the variation of the mechanical strengths. The chemical contribution of admixtures on the strengths of mortars had been evaluated in the basis of the factors of activity K deduced from the concept of the equivalent binder and using the predictive model of strength of Feret. To study the influence of the parameters of formulation on the activity of admixtures in mortars, we used seven admixtures different by their mineralogical natures, their fineness, and their morphological characteristics, two types of cements and two types of superplasticizers. The main results achieved showed that the factors of activity are very sensitive to the nature fineness and proportion of admixtures substituted to cement, but the influence of the nature of cement or superplasticizer was less important. Consequently the activity of admixtures differs from the concept of the equivalent binder recommended by the standard of the ready-mixed concretes which are based on a coefficient of reactivity with contractual values.
Mechanical Performance of Concrete with Partial Replacement of Sand by Sewage Sludge Ash from Incineration
Authors: Jamshidi A. , Jamshidi M. , Mehrdadi N. , Shasavandi A. , Pacheco-Torgal F.
Published: November 2012

The production of sewage sludge from waste water treatment plants is increasing all over the world. Disposal of sewage sludge ash is a serious environmental problem. If we think of the areas needed for sludge ash disposal, we clearly understand the importance of reusing sewage sludge ash in concrete. This paper presents results related to the replacement of sand by sewage sludge ash. The sludge was characterized for chemical composition (XRF analysis), crystalline phases (XRD analysis) and pozzolanic activity. The effects of incineration on crystal phases of dry sludge were investigated. Two (W/C) ratios (0.55 and 0.45) and three sludge percentages (5%, 10% and 20%) by cement mass were used. The mechanical performance of SSAC at different curing ages (3, 7, 28 and 90 days) was assessed by means of mechanical tests. Results show that sewage sludge ash leads to a reduction in density and mechanical strength. Results also show that concrete with 20% of sewage sludge ash and W/C=0.45 has a 28 day compressive strength of almost 30MPa.
Mitigation of Internal Expansive Reaction: The Role of Tungsten Mine Sludge
Authors: Sousa Sofia , Santos Silva António , Velosa Ana , Gameiro André , Rocha Fernando
Published: November 2012

The concrete degradation caused by internal expansive reaction (IER) is a problem that affects many structures in the world. These reactions, which include the alkali-silica reaction (ASR) and the internal sulphatic reaction (ISR) related with delayed ettringite formation, are very dangerous, due the expansive behavior of products formed, that cause the cracking of concrete. So it is urgent to find preventive methods to avoid or mitigate the onset of these reactions in new structures. This work aims to show the applicability of sludge from a tungsten mine in the mitigation of the IER. To evaluate the effect of sludge in the mitigation of ASR and ISR, mortar and concrete mixes were produced with 30% (%in mass) of cement replacement. The results obtained so far allow stating that tungsten mine sludge as Portland cement replacement could be effective in the ASR and ISR mitigation.
Finite Element Model of Granite Ablation with UV Laser
Authors: Saavedra Emilio , López Ana J. , Lamas Javier , Fiorucci Maria Paula , Ramil Alberto , Rivas Teresa
Published: November 2012

This work presents 3-D Finite Element Model of the heat transfer inside granite during pulsed laser ablation with the aim of achieving laser cleaning treatment without damaging the stone surface. The model is focused on biotite, the most affected granite-forming mineral, owing to its low melting temperature. The model predicts sizes of the molten region that are consistent with experimental results. Moreover, the effects of different irradiation parameters; i.e., fluence, laser repetition frequency, and speed of scan have been investigated through the size of the biotite molten region. This model may be considered as the first stage of a comprehensive model of the laser ablation process in granite.
Influence of Mesh Discretization on the Prediction of Polymer Flow Behaviour in Microcavities
Authors: Zhiltsova Tatiana V. , Oliveira Monica S.A. , Vasco Joel C. , Pouzada António Sergio , Pontes A.J.
Published: November 2012

Microinjection moulding is one of the key technologies for the mass production of plastics microcomponents. Recently, significant effort has been made to test the limits of applicability of existent numerical codes for simulating the polymer flow at the microscale. However, the modelling precision in what concerns polymer flow in microimpressions depends on factors which may not be properly accounted for in the process simulation. In this study, a micropart with variable thickness was designed, and the moulding block fabricated and instrumented. Short shots and complete filling of the cavity were carried out and the flow front progress was subsequently evaluated. These data were also assessed numerically by 3D-finite element modelling. A flow simulation considering the polymer as incompressible was carried out to investigate how the mesh size and density affected the prediction of the flow field in the microimpression, using the same processing conditions of the experimental study. The reduction of the mesh size as well as the increase of the mesh density are consistent with better representativeness of the experimental flow front progress in the microimpression. Moreover, the weld line prediction also tends to be improved. This study suggests that the mesh adaption and domain discretization is important in numerical studies of the polymer flow at the microscale.
Modeling the Calibration/Cooling Stage of Complex Thermoplastic Profiles
Authors: Ribau Ângela M. , Gonçalves Nelson D. , Silva Carolina , Nóbrega João M. , Carneiro Olga S.
Published: November 2012

Thermoplastics have very low thermal diffusivity, which is advantageous for some applications but create difficulties for their processing. In fact, in continuous processes, such as extrusion, it can limit the production rate, which is dependent on the installed cooling capability of the extrusion line, originates the development of considerable thermal gradients during the cooling stage and, consequently, the development of stresses that can be frozen in the product (generally referred as residual thermal stresses) that will affect negatively its mechanical performance in use. Therefore, the conditions in which the cooling stage takes place not only determine the production rate, but also the final properties of extruded products. Due to the large number of parameters influencing the cooling stage, its optimization requires the use of proper modelling codes. The work here presented is intended to improve the scope of application of an existing 3D non-isothermal multi-domain numerical code based on the finite volume method (FVM), through the implementation of unstructured meshes enabling, therefore, to predict the evolution of the thermal field during the cooling stage of the extrusion of complex profiles.
Eco-Efficient Concrete Using Industrial Wastes: A Review
Authors: Pacheco-Torgal F. , Shasavandi A. , Jalali Saíd
Published: November 2012

Concrete is one of the most widely used construction materials in the world. However, the production of Portland cement as the essential constituent of concrete requires a considerable energy level. Also releases a significant amount of chemical carbon dioxide emissions and other greenhouse gases (GHGs) into the atmosphere. Global demand will increase almost 200 % by 2050 from 2010 levels. Thus, seeking an eco-efficient and sustainable concrete may be one of the main roles that the construction industry should play in sustainable construction. Portland cement can be partially replaced by cementitious and pozzolanic materials, especially those of industry by-products such as fly ash, GGBS, silica fume, ceramic waste powder and metamorphic rock dust from stone cutting industry. The aggregates are also conserved by replacing them with recycled or waste materials (among which recycled concrete), ceramic waste, post-consumer glass, and recycled tires. All of the previous alternatives are, currently, the most used. This paper summarizes current knowledge about eco-efficient concrete, by reviewing previously published work.
Alternative Feedstocks for Biodiesel Production
Authors: Ribeiro André , Carvalho Joana , Castro Joana , Araújo Jorge , Vilarinho Cândida , Castro Fernando
Published: November 2012

The increasing in the world population has continuously increased the energy demand. As an effective fuel, petroleum has been serving the world to meet its energy needs. Continued use of petroleum sourced fuels is widely recognized as unsustainable because of depleting supplies and all the environmental issues around its use could be responsible for a major deficit in the future. Thus, the development of alternative energy sources, are to be welcomed. Biodiesel, as an alternative fuel, has many benefits. It is biodegradable, non-toxic and compared to petroleum-based diesel, has a more favorable combustion emission profile, such as low emissions of carbon monoxide, particulate matter and unburned hydrocarbons. In brief, these merits make biodiesel a good alternative to petroleum based fuel. The use of alternative feedstock as waste cooking oils (WCO), bovine fats and microalgae oil for biodiesel production has some advantages. It is cheaper than edible vegetable oils and it is a way to valorize a sub-product. Nevertheless, these oils has some contaminants, which can reduce the quality of biodiesel, a problem that was solved by testing different operating conditions and equipment designs for each stage of processing. The technological assessment of this process was carried out to evaluate their technical benefits, limitations and quality of final product. In this work biodiesel was produced by an alkali-catalyzed transesterification, a reaction involving the WCO feedstock and an alcohol to yield fatty acid alkyl esters (biodiesel) and glycerol. The evaluation of quality from raw materials and final biodiesel was performed according to standard EN 14214. Results show that all parameters analyzed meet the standard and legislation requirements. This evidence proves that in those operating conditions the biodiesel produced from WCO, bovine fats and microalgae can substitute petroleum-based diesel.
Aluminium Evaporation during Ceramic Crucible Induction Melting of Titanium Aluminides
Authors: Gomes Fernando , Barbosa Joaquim , Ribeiro Carlos Silva
Published: November 2012

Melting TiAl based alloys in ceramic crucibles often leads to chemical contamination, alloy heterogeneity and non-metallic inclusions. The severity of such phenomena usually depends on the nature of crucible materials, the melting stock composition and the melting parameters, namely superheating time and temperature and melting pressure. Among the referred drawbacks, Al loss during melting is a critical aspect, as its concentration in TiAl based alloys has a very strong effect in their mechanical properties. Although a few studies of critical factors affecting the evaporation behaviour of Al during electron beam and induction skull melting of Ti-Al alloys had been carried out, until now no information was released on this subject for the ceramic crucible induction melting process. In this work a Ti-48Al alloy was induction melted in a zircon crucible with Y2O3 inner layer, using 50 and 100 °C superheating temperatures and 0, 60 and 90 second holding times, and poured into a graphite mould. The effect of different temperature/time combinations in the alloy composition, Al loss by evaporation and extent of the metal/crucible interaction was studied for different melting pressures. Al loss was found to increase significantly for melting pressures below around 10-1 mbar, at a rate that increases as melting pressure decreases, until a maximum rate is reached, remaining constant for lower pressure levels. Metal/crucible interaction increased directly with the melting pressure and superheating time, leading to alloy contamination with yttrium and oxygen. For the experimental set-up and conditions used on this work, optimal superheating time/pressure combinations that lead to acceptable alloy composition and sanity have been identified.
Characterization of Aluminium Single-Lap Joints for High Temperature Applications
Authors: Banea Mariana D. , da Silva Lucas F.M. , Campilho Raul D.S.G. , de Jesus Abílio M.P.
Published: November 2012

In this study, an experimental investigation into the shear strength behaviour of aluminium alloy single-lap adhesive joints was carried out in order to understand the effect of temperature on the strength of adhesively bonding joints. Single lap joints (SLJs) were fabricated and tested at RT and high temperatures (100°C, 125°C, 150°C, 175°C and 200°C). Results showed that the failure loads of the single-lap joint test specimens vary with temperature and this needs to be considered in any design procedure. It is shown that, although the tensile stress decreased with temperature, the lap-shear strength of the adhesive increased with increasing of temperature up to the glass transition of the adhesive (Tg) and decreased for tests above the Tg.