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Über dieses Buch

This book presents the latest findings on mechanical and materials engineering as applied to the design of modern engineering materials and components. The contributions cover the classical fields of mechanical, civil and materials engineering, as well as bioengineering and advanced materials processing and optimization. The materials and structures discussed can be categorized into modern steels, aluminium and titanium alloys, polymers/composite materials, biological and natural materials, material hybrids and modern nano-based materials. Analytical modelling, numerical simulation, state-of-the-art design tools and advanced experimental techniques are applied to characterize the materials’ performance and to design and optimize structures in different fields of engineering applications.

Inhaltsverzeichnis

Frontmatter

Effect of Alloying Elements on Corrosion, Microstructure and Mechanical Properties for Casted Free-Nickel Duplex Stainless Steels

Free nickel Duplex stainless steels containing two different levels of 6–13 wt% manganese contents have been studied and analysed. The alloys, made up of appropriate mixtures of the alloying elements, Ferro-alloys and Ferro-alloys bearing nitrogen were melted in an induction furnace under nitrogen pressure. Even though the resistance to the pitting attack was controlled and enhanced by the nitrogen addition as well as, chromium, molybdenum contents. Also, the cast experimental alloy that contained high manganese was found to offer some advantages over the 2205-type duplex stainless steel in combination of mechanical properties and corrosion resistance. The microstructure development due to increasing manganese contents from 6 to 13 wt% revealed the decrease of the ferrite volume fraction from 82 to 75 %, respectively. Mechanical testing results showed that the free nickel alloys containing 0.14–0.23 wt% carbon with manganese contents ranging from 6.44 to 13.45 wt% have moderate mechanical properties whereas U.T.S. ranging from (691–815) MPa, Y.S. (585–738) MPa, elongation (19–21 %), and a corrosion rate of 0.044–6.0 mm/year, respectively. Manganese is therefore an effective element of duplex microstructures. As an economical development, it is concluded that manganese is a useful replacement element for nickel in duplex alloys, but further work is required before the present alloys, or variations of them, could be commercially viable.

Ragaie Rashad, Amer E. Amer, Ahmed Y. Shash, Hany Shendy

Influence of Al2O3 Nano-dispersions on Mechanical and Wear Resistance Properties of Semisolid Cast A356 Al Alloy

The present investigation studies the prospects of using nanoparticles as reinforcement ceramic powders to gain improved performance of A356 Al cast alloy. Alumina nano-powder of 40 nm size was stirred into the A356 matrix with different fraction ratios ranging from (0, 1, 2 and 4 wt%) in a mushy zone (600 °C) using a constant stirring time for one minute. To evaluate the results, the alloys were further characterized by various tribological and mechanical characterization methods. The results showed higher strength values with improved ductility when compared to the monolithic alloy under the same casting conditions. Also, the wear resistance has been positively enhanced as the amount of the Al

2

O

3

nano-particles addition increases from 1 to 4 wt% leading to a decrease in the weight loss ranging from 5.5 to 4.0 mg, respectively. The Scanning Electron Microscopy of the fracture surface and the wear surface revealed the presence of nanoparticles at the interdendritic space of the fracture surface and was confirmed with an EDX analysis of these particles.

Ahmed Y. Shash, Amer E. Amer, Moataz El-Saeed

Evaluation of Mechanical Properties of Natural and Synthetic Rubber Material

It is critical to investigate the mechanical properties of rubber materials to secure the reliability of rubber components. In this study, we performed mechanical tests of natural and synthetic rubber in various environmental conditions. The hardness, elongation, stress-strain relation, dynamic properties, and the nonlinear material constants that are necessary for a finite element analysis were determined through uniaxial tension, equi-biaxial tension and pure shear tests. The hardness of thermally aged rubber increased in proportion to aging time and temperature while that of elongation decreased. The storage modulus increased in proportion to aging time in dynamic property tests while the loss factor decreased. In mechanical tests according to change in strain, we determined the second Mooney-Rivlin and the third Ogden terms that are necessary for the finite element analysis of rubber components.

Chang-Su Woo, Hyun-Sung Park

Influence of Laser Feeding on Structure and Properties of Cast Aluminium Alloy Surface

The modern methods for surface layer engineering in current surface laser treatments, is LSA treatment, where there are small amounts of alloying additions introduced into the surface layer of the matrix material in the form of ceramic particle powders with different properties influencing the surface layer application possibilities. It was possible to produce a layer consisting of the heat affected zone, transition zone and remelted zone, without cracks and defects as well as with a slightly higher hardness value compared to the non remelted material. The laser power range was chosen to be 1.5–2.0 kW and implicated by a process speed rate in the range of 0.25–0.75 m/min. The purpose of this work is to apply High Power Diode Laser (HPDL) for the improvement of aluminum’s mechanical properties, especially the surface hardness. This study was conducted to determine the effect of SiC powder addition on the structure and the mechanical properties as well as the structural changes occurring during the rapid solidification process. The main findings were, that the obtained surface layer is without cracks and defects as well as having a comparably higher hardness value when compared to the non-remelted material. The hardness value increases according to the laser power used so that the highest power applied gives the highest hardness value in the remelted layer.Also, the distribution of the SiC particles is good, but the particles are mainly present in the upper part of the surface layer. The hardness value increases in general according to the laser power used so that the highest power applied renders the highest hardness value in the remelted layer. The main goal of this work is to investigate and determine the effect of HPDL remelting and alloying on the cast Al-Si-Cu cast aluminium alloy structure to recognise the possibility for application in real working conditions mainly for light metal constructions as in the many branches of the industry.

K. Labisz

Application of the Finite Element Method for Modelling of the Spatial Distribution of Residual Stresses in Hybrid Surface Layers

The presented investigations concern PVD/CVD surface treatment performed on samples of heat treated cast magnesium and aluminium alloys and properties modelling of obtained coatings using the finite element method (FEM). In order to identify the structure and fractures of the analysed surface coatings, investigations using the scanning electron microscope Zeiss Supra 35 were performed. Evaluation of the adhesion of the PVD/CVD coatings was carried out using a scratch test. The obtained coatings—Ti/Ti(C,N)-gradient/CrN; Ti/Ti(C,N)-gradient/(Ti,Al)N; Ti/(Ti,Si)N-gradient/(Ti,Si)N as well coatings: Cr/CrN-gradient/CrN; Cr/CrN-gradient/TiN and Ti/DLC-gradient/DLC are characterized by a clear heterogeneity of the surface associated with the presence of microparticles in the structure in form of droplets broken out of the target during the deposition process, as well immersions occurring in the surface due to the loss of some droplets during solidification. It was also found that the applied coatings are characterized with a mono-, di-, or multi-layer structure according to the applied layer system; the individual layers are applied uniformly and tightly adhere to the substrate and to each other. The obtained results of the numerical FEM analysis, have enabled a full integration of the material engineering knowledge and informatics tools, confirming compliance of the simulation model with the obtained experimental results.

Tomasz Tański, Krzysztof Labisz, Wojciech Borek, Marcin Staszuk, Zbigniew Brytan, Łukasz Krzemiński

Study of the Utilization of Polyamide Composite with Fiberglass Reinforcement in Automotive Engine Mounts

The aim of this work is to study the replacement of the support of the engine mounts from aluminum to commercial polyamide composite (PA 6.6) reinforced with 30, 35 and 50 % of fiberglass. The purpose of this replacement is to reduce the weight of the component. Flexion and fatigue tests were performed at 120 °C utilizing the Staircase Method. The results have shown the excellent adherence of polyamide in fiberglass. The polyamide composite with 50 % fiberglass presented the lowest deflection. The comparison of the tension distribution utilizing the Finite Element Method between the supports of the bearing engine made of polyamide with fiberglass and Al alloy have shown almost the same results. However, the polyamide composite presented higher values of deflection. Finally, due to the weight reduction of 32 %, it was possible to confirm that the polyamide composite is viable to change the Al alloys in automotive engine bearings.

Leandro Cardoso da Silva, Antonio Augusto Couto, Renato Baldan, Jan Vatavuk

Shaping of Surface Layer Structure and Mechanical Properties After Laser Treatment of Aluminium Alloys

The influence of laser treatment on the structure, mechanical properties and wear resistant casting of aluminium alloys has been studied. The main objective of this investigation was to improve the tribological and mechanical properties of the surface layer of the aluminium alloy AlMg5Si2Mn by remelting and feeding the chromium particles into the melt pool with a rapid solidification. The applied size of the chromium particles have been in the range 50–120 μm. For the remelting of the surface a high power diode laser (HPDL) was used. The applied laser beam power is in the range from 1.8 to 2.2 kW. The linear laser scan rate of the beam was set to 0.5 m/min. The chromium powder has been introduced in the melt pool using a gravity feeder at a constant rate of 2 g/min. The application of the laser surface treatment of aluminum alloys enables us to obtain too much harder and better wear resistance compared to based materials.

Tomasz Tański, Wojciech Pakieła, Maciej Wiśniowski, Leszek Adam Dobrzański

On Shearography Testing of Tires Separations

The paper deals with the systematic experimental study of tires wear accompanied by separation created in tires of different construction exposed to dynamic loading. 12 pieces of tires with the dimensions of 225/75 R 16 C with the same tread pattern were manufactured for the test in order to examine the impact on the material and design changes on the spread of separations in a tire. The atlas of separation is presented. The results of separation detection obtained by contact-less shearography are compared with those of optical. Graphic relevant analysis of tire wearing process is effectuated.

Helena Hajská, Pavel Koštial, Oldřich Kodym, Zora Jančíková, Jiří David, Roman Meca, Vladimír Rusnák

Compression Behaviour of Finite Dimensional Cellular Metals by Generalization of Cell Buckling Effects

Metal foams are materials of recent developments and applications that show interesting combinations of physical and mechanical properties. Foams are commonly used as of passive safety components due to their high capacity of energy absorption under impact conditions. In this work the foam is represented as a cellular material with a regular structure and specimens of a cellular metal are used to study the foam behaviour. Considering that compression is the dominant loading in impact situations, the deformation behaviour of finite dimensional cellular metal specimens under compression is investigated. The specimen deformation configuration is determined by means of fundamental buckling effects on cells walls evaluated from simple representative volume elements. Damage effects under a finite strain context are included together with self-contact considerations. The overall behaviour of a finite specimen is derived from an analytical and numerical framework based on the boundary conditions present on the foam. The main advantage of this method is the capability of determine the full behaviour of a complex foam configuration with only simple case analyses, with low computational cost.

Renato V. Linn, Branca F. Oliveira

Modelling of the Surface Morphology by Means of 2D Numerical Filters

When examining a surface machined by means of a repeatingly acting tool, especially a cyclically acting, as in the case of rotating machines, a characteristic patter can be observed when analyzing the surface morphology. Such a patter can be recognized as a characteristic symptom of the cooperation between the tool and the machined element, being usually in the tight contact. Obtaining any quantitative results evaluating this cooperation, demands establishing of the well suited mathematical model. In this paper a relationship is presented based on the numerical two-dimensional model filters of the quadrant type, acting on a square lattice representing surface. This appears to be an efficient numerical tool, providing a sufficient number of degrees of freedom and a fast execution, even though special measures have to be taken to assure their stability. The filters have been excited with simple stochastic processes simulating randomness of the abrasive machining at its basic level. The obtained results have been examined mainly by to methods: by using classical statistical analysis and by using the surface autocorrelation idea. This second method has been proven to be a good tool for the quantitative evaluation of the surface interaction during the machining process.

Andrzej Golabczak, Andrzej Konstantynowicz, Marcin Golabczak

Modelling of the Roughness Profile by Means of the Autoregressive Type Stochastic Processes

The 2D roughness profile resulting from the standard measurement using a mechanical profilometer is usually the basic examination of a machined surface. Obtained results, usually in the form of the statistical parameters’ set are used for the surface machining evaluation as well as the forecast of the tribological behavior of the surface. The second mentioned purpose demands a particularly well suited mathematical model to accomplish a quantitative evaluation of the tribological parameters. In this paper a specific method is presented for this modelling based on the stochastic processes. In these processes the amplitude distribution has been modelled with the application of different probabilities densities and the spatial behavior has been modelled with application of the autoregressive process idea. The autoregressive capabilities of the model have also been proved by means of spectral analysis. The obtained results show that some probability densities of the used processes are highly related with the statistical roughness parameters, especially skewness and kurtosis. This in turn gives a good basis to forecast the tribological properties of the examined surface, including its directional characteristics. The numerical results have been compared with the experimental surfaces roughness measurements, showing good compatibility with the forecasted tribological parameters.

Andrzej Golabczak, Andrzej Konstantynowicz, Marcin Golabczak

Drainage Concrete Based on Cement Composite and Industrial Waste

The ongoing development of urbanization of our landscape has resulted in continuous demand for building materials, which are even nowadays produced mainly from primary natural resources. The continuous reconstructions and modernizations of already built-up areas are the cause of the production of construction waste which, for example, in Europe represents ¼ of the volume of all waste materials. Such a trend is inconsistent with sustainable development and considerate impact on the environment. The contemporary society is aware of these adverse impacts and it actively participates in the integration of construction waste back into production. Thanks to the systems of recycling, construction waste can return to the building industry as a fully valuable building material. The production of shaped pieces from grey cellular concrete after the autoclave process results in the creation of residual material in the form of waste blocks (rubble). This waste material is stored in dumps. The presence of these dumps has an adverse effect on the surrounding environment. This article presents the first results of a basic research dealing with the treatment process of waste cellular concrete rubble by means of a crushing process and its subsequent use as filler in the production of new porous concretes. The article presents 3 basic recipes of porous concrete, where 100 % of the filler was replaced with crushed porous concrete rubble with the fraction of 0/6 mm. The proposed recipes have been tested in regards to: density of fresh concrete mixture, concrete mixture consistency, strength, and thermal conductivity coefficient.

Lukáš Gola, Vojtěch Václavík, Jan Valíček, Marta Harničárová, Milena Kušnerová, Tomáš Dvorský

Numerical Analysis of Impact Behavior of Rotary Centrifuge Guarded Body

Numerical simulation of dynamic mechanical responses of a rotary centrifuge at different impact velocities and angles is performed. The impact velocities are 25 m/s, 50 m/s and 270 m/s and the impact attitudes are 0° and 45° respectively. Stress fields and failure modes of the guarded body, cavity wall, cover and rotary components are obtained. It indicates that the cavity wall can withstand impact action. The deformation of the cavity wall and cover is elastic when the turntable velocity is lower than 25 m/s. Centrifuge guarded body will be broken when turntable velocity is over 50 m/s. This analysis can guide design and safety assessments of rotary centrifuge.

Weizhou Zhong, Xicheng Huang, Chengang Luo, Gang Chen, Zhifang Deng

Capillary Active Insulations Based on Waste Calcium Silicates

The issue of capillary active calcium silicate insulation used in the systems of energy redevelopment of historic buildings is a very up-to-date topic. This article describes the properties of the developed material structures built on cement composites with a defined inner surface using industrial waste materials containing aluminosilicates. The article presents the structures containing fly ashes from heating plants improving the rheological properties of the mixture and the latent hydraulic properties allowing a reduction of the necessary amount of the binding matrix, represented by cement in this case, which has a direct impact on the economy of the final material. The aim of the developed material is to extend the segment of capillary thermal insulation board materials used for the purpose of energy redevelopment of historic buildings. The article will present the parameters evaluating the capillary activity of the material, the coefficient of diffusion resistance, the thermal conductivity coefficient and the physical and mechanical properties. The acquired values are then implemented into the simulation software Delphin, taking into account the moisture transport in porous materials under non-stationary conditions. The output of the software is a simulation describing the developed material in time, after the incorporation into a moisture-defined building structure showing a disruption of the waterproofing layers of the lower structure.

Aleš Břenek, Vojtěch Václavík, Tomáš Dvorský, Jaromír Daxner, Vojtech Dirner, Miroslava Bendová, Marta Harničárová, Jan Valíček

Comparison of Some Structural and Stainless Steels Based on the Mechanical Properties and Resistance to Creep

Knowledge of the properties of materials and their behavior in certain environmental conditions is one of the most important factors in the procedure of materials selection. In accordance with this fact, this paper presents and analyzes the experimental results relating to two structural (1.0044, 1.7228) and two stainless steel (1.4305, 1.4122) materials. Stress-strain diagrams as well as creep curves related to short-time creep are presented. According to the mentioned diagrams, the ultimate tensile strength, yield strength and modulus of elasticity are determined. On the other hand, based on material creep curves, some conclusions regarding to creep resistance may be given. Also some data related to Charpy impact energy is shown as well as fracture toughness assessment based on impact energy is made. Based on experimental results it can be said that all of the investigated materials have quite high tensile strength and yield strength. Also, these materials may be treated as creep resistant at temperature of 400 °C if the stress level does not exceed 50 % of the yield strength at this temperature.

Josip Brnic, Goran Vukelic, Sanjin Krscanski

Investigation of the Influence of Improvement on the Effect of Strain hardening of 34CrMo4 in the Production of Seamless Steel Pressure Vessels from Pipes

This paper analyzes the process of making a seamless pressure vessel Ø229 mm on a spinning machine. The pressure vessels are exposed to high operating pressure when in use (up to 200 bar). Therefore, the material of the pressure vessels must meet specific requirements to prevent cases of disaster and damage. It is required to pass a burst test on one out of the 200 pressure vessels. If the burst test meets the requirements and demands, a pressure vessel is randomly selected from the same batch, and is used to make the test samples for testing the mechanical properties. Only if these results meet the standard prescribed limits, the pressure vessels can be delivered to the user. The purpose these tests, by controlling the mechanical properties of samples made from the finished pressure vessels before and after heat treatment by improving 34CrMo4 steel, and comparing them with the required standard values, is to assess the technological parameters and possible approaches in future research that could contribute to the reliability of pressure vessels in use.

V. Marušić, I. Lacković, L. Marušić

Computational Modeling of Structural Problems Using Atomic Basis Functions

This paper presents the application of the

Fup

n

(

x

) basis functions in numerical modeling of different engineering problems.

Fup

n

(

x

) basis functions belong to a class of atomic functions which are infinitely-differentiable functions with compact support. The collocation method has been applied in the development of numerical models. A system of algebraic equations is formed in which the differential equation of the problem is satisfied in collocation points of a closed domain while boundary conditions are satisfied exactly at the domain boundary. Using this way, the required accuracy of approximate solution is obtained simply by an increase in the number of basis functions. So, this concept represents a fully mesh free method. The properties of the atomic basis functions enable a hierarchic expansion of an approximate solution base either in the entire domain or in its segments. Presented numerical models are illustrated by examples of the torsion of prismatic bars, elasto-plastic analyses of beam bending and thin plate bending problems. The results of the analyses are compared with the existing exact and relevant numerical solutions. It can be concluded that the possibility of hierarchically expanding the number of basis functions in the domain significantly accelerates the convergence of a numerical procedure in a simple way. Values of the main solution function, e.g. displacements, and all the values derived from the main solution of the problem such as stresses, bending moments and transversal forces, are calculated in the same points and with the same degree of accuracy since numerical integration is avoided.

Vedrana Kozulić, Blaž Gotovac

Simulation of Plastic Deformation Behaviors of Bulk Metallic Glasses with Micro- and Nano-sized Pores

Based on the phase-field model for deformations in bulk metallic glasses (BMG), shear banding in BMG with micro- and nano-sized pores is simulated and the thermo-plastic deformation behaviors are investigated. In the simulations, we use the free-volume concentration

w

0

at the pore surface as a measure of the roughness of the pore. We obtain the critical

w

0

when shear bands are initiated from the pore surface under different loading conditions. The effect of local heating due to shear banding on the critical

w

0

is also quantitatively determined. By considering the heat conduction around pores, shear banding around vacuum pores or pores filled with helium gas are found to be quite different. It is shown that the nano-sized pores act as sinks or sources for shear bands when the pore surfaces are tailored. The simulations indicate that engineering BMG with nano-sized pores is effective in improving their ductility.

Hong-Ying Zhang, Guang-Ping Zheng

The Influence of Process Parameters on the Temperature Profile of Friction Stir Welded Aluminium Alloy 6063-T6 Pipe Butt Joint

The temperature profile of friction stir welded aluminum alloy 6063-T6 pipe joints will be investigated in this paper. A pipe with an outside diameter of 89 mm and a wall thickness of 5 mm will be used as test pipe piece for this experiment on closed butt joint configuration by utilizing a Bridgeport 2216 CNC milling machine and orbital clamping unit which is specially-designed to cater for this task and function. Several samples will be prepared with varying process parameters such as rotational speed and travel speed. A very simple tool was used with a flat shoulder and a cylindrical pin. An infra-red thermometer will be employed to assess the temperature profile of the friction stir welded pipe butt joints during the experiment. The correct selection of process parameters will lead to a better joining condition of the welded joint. Several good samples were produced by this experiment setting.

Azman Ismail, Mokhtar Awang, Shaiful Hisham Samsudin

Influence of Cement Type and Mineral Additions, Silica Fume and Metakaolin, on the Properties of Fresh and Hardened Self-compacting Concrete

Proportioning and mixing self-compacting concrete is a challenging task because the concrete mixture has to be stable and has to have the ability to fill formwork and to bypass obstacles under the influence of its own weight. Besides that, the final product has to be quality hardened concrete. It is known that even a little alteration of any component can significantly change characteristics of fresh and hardened concrete. In this work, the influences of the type of cement and additions, namely silica fumes and metakaolin on the workability and compressive strength of self-compacting concrete, are experimentally examined. For this purpose, several mixtures of self-compacting concrete were prepared and tested. The properties of fresh mixture were determined by the slump flow method, visual assessment of stability, T50 time, V-funnel method, L-box method and J-ring method. Also, in the hardened state, compressive strengths after 7 and after 28 days were determined. Results obtained in this work were compared with the results of other authors.

Sandra Juradin, Dražan Vlajić

On the m-Term Best Approximation of Signals, Greedy Algorithm

Described the class of signals such that the error between signal and m-term best approximant with respect to orthonormal basis has the following behavior : o( log m )¯

¼

.

Martin G. Grigoryan

Effect of Simultaneous Plasma Nitriding and Aging Treatment on the Microstructure and Hardness of Maraging 300 Steel

Simultaneous nitriding and aging heat treatment of maraging 300 steel was carried out inside a DC-pulsed plasma nitriding reactor. A single heat treatment cycle was done, as the plasma nitriding and age hardening processes occur at the same ranges of temperatures and times. Samples of maraging 300 steel, in the solution annealed and solution annealed and aged conditions, were tested. Plasma nitriding and aging, carried out at 480 °C for 3 h, increased the surface hardness up to 1140 HV, producing case depths of 50 μm since ε-Fe

3

N and γ′-Fe

4

N nitrides were formed in the hardened surface layer. It is observed that the microstructure of the core material remains unaltered as the typical martensite plate-like microstructure of maraging steels. The core hardness of solution annealed samples increased from 331 to 597 HV after the plasma nitriding treatment proving the possibility of nitriding and aging at the same treatment cycle. The pre-aged samples did not show any overaging or martensite reversion to austenite after the simultaneous plasma nitriding and aging treatments, that could be showed by the core hardness of 620 HV and can be related to the time of total aging exposure of 6 h, including pre-aging and plasma nitriding.

Adriano Gonçalves dos Reis, Danieli Aparecida Pereira Reis, Antônio Jorge Abdalla, Jorge Otubo, Susana Zepka, Antônio Augusto Couto, Vladimir Henrique Baggio Scheid

State Analysis and Development Perspectives of the Algeria’s Railway Network

The current rail transport in Algeria does not meet the needs of the national economy because some of the lines have been designed and built according to a set of old standards, which results in them being characterized by a relatively low productivity and lack of work efficiency. This is why the reconstruction and strengthening of the Algerian railway network is becoming necessary if not mandatory. The further development of the railway linking and improving the quality of its operation will result in improved performance and speed. This is why the development of the Algerian rail network is a very important and specific task addressing this issue must ensure a high competitiveness. The development of an approach in order to increase the railway lines efficiency in the Algerian context and the process of reconstructing them needs a thorough analysis the state of a number of railway lines with low profitability, in order to organize their reconstruction, open the possibility of having easier access and efficient facilities, thus reaching a rational scheme.

Hakim Siguerdjidjene

Characterization of the Superalloy Inconel 718 After Double Aging Heat Treatment

The application of heat treatment, by solid solution and precipitation hardening, is very important to optimize the mechanical properties of superalloys. The main phases present in Inconel 718 are: gamma prime γ′ face ordered Ni

3

(Al, Ti); gamma double prime γ″ bct ordered Ni

3

Nb; eta η hexagonal ordered Ni

3

Ti; delta δ orthorhombic Ni

3

Nb intermetallic compounds and other topologically closed-packed structures such as μ and Laves phases. δ, μ and Laves phases have low ductility, which causes losses in mechanical and corrosion properties (Fu et al. in Mater Sci Eng A 499:215–220, 2009 [

1

]). The heat treatment applied to Inconel 718, precipitation hardening, has two steps: solid solution and aging treatment. In first step the secondary (hardening) phases are dissolved along the matrix, as well as carbides. It is important to note that after 650 °C (Durand-Charre in The microstructure of superalloys. CRC Press, Boca Raton, 1997 [

2

]) and with long exposure times, γ″ transforms in the stable phase δ, which results in a loss of mechanical resistance. In this study we aim to characterize the microstructure and phases in superalloy Inconel 718 during the steps of heat treatment with double aging. The double aging treatment performed followed the steps of solid solution to 1095 °C/1 h and double aging at 955 °C/1 h to 720 °C/8 h + 620 °C/8 h. The characterizations were performed through the techniques of XRD and SEM/EDS. It was possible to obtain the microstructural and phases characterizations before and after heat treatment in all steps.

Katia Cristiane Gandolpho Candioto, Felipe Rocha Caliari, Danieli Aparecida Pereira Reis, Antônio Augusto Couto, Carlos Angelo Nunes

Development of an Innovative 3D Simulator for Structured Polymeric Fibrous Materials and Liquid Droplets

Contribution to the Experimental Characterization and Optimization of Deposition Time and Spreading Area Using an Innovative 3D Optic System and a Fibrous Porous Materials Simulator

An innovative 3D approach is used to develop and optimize structured polymeric fibrous materials. Using our own materials simulator we are able to design a new material with optimized properties such as porosity or thickness. In this work, for the first time we developed and tested a methodology to design a new fibrous material for which the penetration of a liquid drop can be predicted and optimized. The deposition of a liquid drop into a porous solid material is an important step in many materials applications like printing or filtration. The ability to control and predict the liquid kinetic deposition and the spreading area, are also determinant steps when developing new advanced materials, like structured porous materials, and new applications, like the transport of therapeutic molecules for medicinal purposes. We have used a methodology that includes an innovative 3D model for fibrous materials, an experimental plan to obtain 3D structures with different fibers, and an optic 3D prototype for collecting 3D data of the liquid drop deposition along time. We were able to quantify the time of deposition and the spreading area over time. Using the simulation model for fibrous materials we were able to simulate and produce in the laboratory an optimized structure for the ideal spreading area of the liquid droplet.

Joana M. R. Curto, António O. Mendes, Eduardo L. T. Conceição, António T. G. Portugal, Paulo T. Fiadeiro, Ana M. M. Ramos, Rogério M. S. Simões, Manuel J. Santos Silva

The Effect of Vacancy Defects on the Evaluation of the Mechanical Properties of Single-Wall Carbon Nanotubes: Numerical Simulation Study

A three-dimensional finite element model is used in order to evaluate the tensile and bending rigidities and, subsequently, Young’s modulus of non-chiral and chiral single-walled carbon nanotubes containing vacancy defects. It is shown that the Young’s modulus of single-walled carbon nanotubes with vacancies is sensitive to the presence of vacancy defects in nanotube: it decreases with increasing of the density of vacancy defects.

Nataliya A. Sakharova, Jorge M. Antunes, André F. G. Pereira, Marta C. Oliveira, José V. Fernandes

Structure and Properties of Zn–Al–Cu Alloys with Alloying Additives

In the present work the investigations concerning the influence of the modification with cerium on the microstructure and properties of the Zn–Al–Cu alloy was shown. The investigations were realized for Zn–Al–Cu samples with approximately 0.1 % Ce in the form of Al–Ce master alloys added. The heat treatment was performed in a resistance furnace with a chamotte-graphite crucible. For the remelting, with cerium as an alloying element, an argon protective atmosphere was used. The treated alloy was cast into the metal casting dies. To determine the influence of the modification on the structure and properties of those alloys, the following investigations were carried out: transmission and scanning microscopy, EDSX-ray analysis, and hardness analysis. The modification of the chemical composition, properly realized, leads to the improvement of mechanical properties of the produced castings. That is why, it is important to recognize the dependencies between the structure of the casts and chemical composition changes connected with the addition of modifiers. Investigations concerning both the optimal chemical composition and production method of Zn–Al–Cu alloys modified by chosen rare-earth metals as well as the improved properties in comparison with traditional alloys and methods contribute to better understanding the mechanisms influencing the improvement of mechanical properties of the new developed alloys.

Krupińska Beata

The Benefits of Using Tyre Rubber Aggregate in Concrete Specimens

The present experimental paper studies the mechanical and physical properties of concrete in which tyre rubber aggregate is incorporated. From this study, one can conclude that the presence of tyre rubber aggregates (RG) significantly reduces the velocity of ultrasonic waves in concrete added with RG. This composite has the potential to dampen vibration, which may be of particular use of sound insulation. Furthermore, the incorporation of RG significantly reduces the kinetics of ultrasonic pulses in concrete. This reduction is mainly attributed to the decrease in density the composite and the presence of water and air pores in the material. With such a damping capacity of waves in general and more specifically mechanical vibrations, it is worth considering the use of this composite in the applications such as noise walls of arterial roads, as the foundation of rails gear wheel or foundation for vibrating machines, etc. From this study, we conclude, that the benefit of using waste tyre rubber could be greatly appreciated to preserve environment and to discover other new concrete composites.

Hadda Hadjab, Oussama Boulekfouf, Ahmed Arbia

The Use of PSC Technique to Estimate the Damage Extension During Three Point Bending Test

It is already known that when a mechanical loading is applied to cement-based specimens weak electrical currents are generated. Their existence is attributed to the creation of cracks and the eventual evolution of the cracks’ network in the bulk of the specimen. This work introduces the simultaneous recording of electrical signal emissions at both the tension and the compression region of cement mortar beams of rectangular cross-section that were subjected to mechanical loading using the Three-Point-Bending technique. During the experiments the behavior of the electrical signal was studied during four sequential load stages: (1) Abrupt load increase up to the vicinity of 3 PB strength, (2) maintaining the high load level for relatively long time, (3) abrupt load decrease to a low load level (i.e. 50 % of the 3 PB strength approximately), (4) maintaining the low load level for relatively long time. The electrical signal analysis was conducted using non extensive statistical physics (NESP) and specifically the Tsallis entropy model studying the values of its q-parameter. The aim of this work was to study the electrical signal relaxation process that follows the change of the mechanical load and the law that describes this relaxation with respect to the mechanical status of the specimen using statistical physics analysis.

Charalampos Stergiopoulos, Ilias Stavrakas, Dimos Triantis, George Hloupis, Filippos Vallianatos

Numerical Modelling of Young’s Modulus of Single-Layered Cubic Zirconia Nanosheets

It has been established that zirconia nanosheets have many potential applications when compared with other materials possessing similar properties; however, the utilization of most of their potentials is constrained due to minimal data currently available on its mechanical properties. In this paper, the Young’s modulus of single-layered zirconia nanosheets is predicted based on the concept of the finite element analysis. The nanosheet was modelled structurally as a hexagonal network of bonds connected by zirconium and oxygen atoms. Zirconia nanosheets with different dimensions and chirality were simulated with bonds between the atoms regarded as beam elements. The Young’s modulus of the nanosheet was determined based on the combination of molecular mechanics and structural mechanics. The results obtained from the modeling indicates that the technique used is a viable tool for predicting mechanical properties of cubic zirconia nanosheets at a lower computational cost when compared to complex ab initio molecular dynamics and sophisticated experimental techniques.

Ibrahim Dauda Muhammad, Mokhtar Awang, Lee Kain Seng

Closed Form of a Transverse Tapered Cantilever Beam Fundamental Frequency with a Linear Cross-Area Variation

The present work is based on the Rayleigh quotient formula to express the transverse vibration frequency of a tapered cantilever beam by a closed form equation. In this investigation the tapered case considered is that of a linear cross-section variation. Thus, a shape equation is needed. It can be obtained through an exact solution of the fourth order differential equation, with non constant coefficients governing the equilibrium of the tapered beam element. The shape form of a uniform beam is considered as being the first mode shape in the present investigation. By applying the Rayleigh quotient, a simple closed form equation of the circular frequency as a function of the taper degree is suggested for practical use. A validation of the numerical results with the extreme case corresponding to the uniform beam is done. By comparing the curves of the two shapes corresponding to the tapered and uniform cantilever beams, they are found to be in good compliance.

Farid Chalah, Lila Chalah-Rezgui, Salah Eddine Djellab, Abderrahim Bali

Free Vibration of a Beam Having a Rotational Restraint at One Pinned End and a Support of Variable Abscissa

To carry out a dynamic analysis of vibrating systems, different methods exist and numerical methods take a large place. In this study, a beam with one overhang, having a rotational restraint at one pinned end and a support of variable abscissa is investigated. Many situations are studied using the finite element method based on the Euler-Bernoulli assumptions to analyze beams vibration, without elastic restraints. The purpose of this investigation consists of treating similar beam cases with and without a rotational restraint at one node. The first step of validation is relative to the extreme situations where either the overhang or the intermediate span length is zero (span length approx. zero). In these two studied cases, the rotational restraint is not considered. It is compared to theoretical, energetic Rayleigh method results and those due to the finite element method for the simply supported beam, pinned-clamped and free-fixed beam (cantilever beam). When the rotational restraint value increases the beam is considered first pinned-pinned and then pinned-fixed behavior is obtained. The results as found are in agreement with analytical ones and after introducing the rotational restraint at the right-hand end, an intermediate behavior is initiated by varying the s/L (span length/beam length) ratio, allowing a simplified extraction of the fundamental vibration frequency for various values of K

r

(rotational restraint).

Lila Chalah-Rezgui, Farid Chalah, Salah Eddine Djellab, Ammar Nechnech, Abderrahim Bali

On the Buckling Behavior of Curved Carbon Nanotubes

In this study, numerous armchair and zigzag single-walled carbon nanotubes (SWCNTs) were simulated by a commercial finite element package and their buckling behavior was investigated through performing several computational tests with cantilevered boundary conditions and different bending angles. Both computational and analytical results were compared in the case of straight tubes. It was pointed out that the computational results are in good agreement with the analytical calculations. It was also concluded that the first critical buckling load of both straight armchair and zigzag CNTs increases by increasing the chiral number. In addition, it was indicated that the first critical buckling load of straight CNTs decreases by introducing the bending angle to the structure of CNTs. However, this decrease is more noticeable in the case of armchair and zigzag CNTs with higher number of chirality and it is almost negligible for CNTs with lower number of chirality.

Sadegh Imani Yengejeh, Seyedeh Alieh Kazemi, Andreas Öchsner

Metrology by Image: Discussing the Accuracy of the Results

The development of new inspection techniques have been studied due to their important role in ensuring the quality of products and services. Achieving technical specifications of products considering acceptance criteria requires knowledge of assured inspection methods. Inspection techniques have evolved expressively, lacking, however, in some cases, of certified standardization. The past ten years have experienced considerable development of inspection methods. In part, this is due to the need to meet the security and reliability requirements for consumer protection. Moreover, the extraordinary advances in electronics and computers were also important factors for this advance. In this context visual inspection by images is being applied in many applications, allowing the identification of innumerous product features, like cracks, corrosion, distortion, misalignments, porosity, among others. But, inspections and measurements require calibration of instruments, devices and systems. In order to obtain confident measurements it is important to study and specify the suitable lighting system, camera, lens and principally the best computer measurement algorithms. Thus the aim of this paper is to discuss the relevance of the main parameters that influence the measurement of images using computer vision techniques.

Fabiana Rodrigues Leta, Juliana F. S. Gomes, Pedro B. Costa, Felipe de O. Baldner

Experimental and Numerical Studies of Fiber Metal Laminate (FML) Thin-Walled Tubes Under Impact Loading

Fiber metal laminate (FML) in form of tubular structures is a modern light-weight structure fabricated by incorporating metallic and composite materials. This present study deals with the impact characteristics and energy absorption performances of fiber metal laminate (FML) thin-walled tubes subjected to impact loading. Dynamic computer simulation techniques validated by experimental testing are used to perform a series of parametric studies of such devices. The study aims at quantifying the crush response and energy absorption capacity of FML thin-walled tubes under axial impact loading conditions. A comparison has been done in terms of crush behaviour and energy absorption characteristics of FML tubes with that of pure aluminium and composite tubes. It is evident that FML tubes are preferable as impact energy absorbers due to their ability to withstand greater impact loads, thus absorbing higher energy. Furthermore, it is found that the loading capacity of such tubes is better maintained as the crush length increases. The primary outcome of this study is design information for the use of FML tubes as energy absorbers where impact loading is expected particularly in crashworthiness applications.

Zaini Ahmad, Muhammad Ruslan Abdullah, Mohd Nasir Tamin

Dynamic Calibration Methods of Accelerometer in Vibration-Temperature Combined Environment

The ground simulation experiment of vibration-temperature combined environments is an important means of aircraft testing for environmental adaptability research and structural response analysis. An accelerometer is used to measure structure mechanics parameters with vibration loading, while the sensitivity of the accelerometer drifts as temperature starts to rise, something which could affect the precision of vibration experiment as well as the data obtained from the test. Based on the acceleration calibration method and standards, this paper expounds the key points of dynamical calibration technique with vibration-temperature combined loading, and also introduces some latest experimental methods and calibration devices, which provide an accurate and controlled means of sensitivity calibration of the accelerometers in accordance with back-to-back comparative calibration standards. At last, we combined accelerometer’s calibrations and the obtained data, to establish the sensitivity correction of the temperature drift model to improve precision of the combined load during the ground simulation experiment.

Chun zhi Li, Ying Chen, Tong Zhou

Erratum to: Effect of Simultaneous Plasma Nitriding and Aging Treatment on the Microstructure and Hardness of Maraging 300 Steel

Adriano Gonçalves dos Reis, Danieli Aparecida Pereira Reis, Antônio Jorge Abdalla, Jorge Otubo, Susana Zepka, Antônio Augusto Couto, Vladimir Henrique Baggio Scheid
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