The paper presents the impact of exceeding the railway rails lifespan which usually causes a railway structural failure, thus an accident. The research highlights the rails’s high degradation, especially on the running area, consisting in 60-70% weight loss by advanced wear of the rail, followed by fatigue fracture caused by alternating cyclic stresses that initiates the crack and also by tensile stresses resulting in the crack growth. The chemical composition, structural and mechanical properties were analyzed in order to establish the causes that led to the railway rails rupture.

Machining with tool that have cutting edge radius provides components with high fatigue strength, microhardness of a large surface layer and plastic deformation. Finite element simulations of the cutting process give a better knowledge of the chip generation phenomenon, heat generation in the machining area, stress and temperature field results. This study emphasizes the true importance of the mathematical model that underlies the shape of the tool in the pre-processing steps of finite element analysis. The argument is that its achievement and definition depend on the network difficulty. This research purpose is to perform simulations series of orthogonal machining with different radius and depth of cut. In this way, conclusions on the impact of these variations on the whole cutting process were drawn. The finite element application used is Deform 2D, the Lagrange incremental method and the Johnson-Cook material model. The temperature distribution, stress distribution, von Mises stress distribution, effects on specific tool pressure and wear, and fluctuations in the cutting resistance of the tool tip and C45 workpiece were analyzed.

The most common means to analyze redox gradients in sediments is by push/pulling electrochemical probes through sediment’ strata while repeating measurements. Yet, as electrodes move up and down they disrupt the texture of the sediment layers thus biasing subsequent measurements. This makes it difficult to obtain reproducible measurements or to study the evolution of electrochemical gradients. One solution for solving this problem is to eliminate actuators and electrode movements altogether, while instead deploying probes with numerous electrodes positioned at various depths in the sediment. This mode of operation requires electrode switching. We discuss an electrode-switching solution for multi-electrode probes, based on Complementary Metal-Oxide-Semiconductor (CMOS) multiplexors. In this solution, electrodes can be individually activated in any order, sequence or time frame through digital software commands. We discuss constraints of CMOS-based multilayer electrochemical probes during cyclic voltammetry.

Geopolymer is synthesized by polycondensation of SiO4 and AlO4 aluminosilicate complexes, tetrahedral frames linked with shared sialate oxygen. This paper studies the effect of the solids-to-fluids (S/L) and Na2SiO3/NaOH proportions on the preparing of metakaolin inorganic membrane geopolymer. By consolidating a mixture of metakaolin with sodium hydroxide, sodium silicate and foaming agent, the geopolymer membrane was made in required shape about 1 cm and cured at 80°C for 24 hours. After the curing process, the properties of the samples were tested on days 7. Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution were utilized as an alkaline activator with a NaOH fixation fixed at 10 M. The geopolymer inorganic membrane tests were set up with various S/L proportions (0.8, 1.0, 1.2 and 1.4) and Na2SiO3/NaOH proportions (0.5, 1.0, 1.5, 2.0 and 2.5). Aluminium (Al) powder as a foaming agent was used to create bubbles in porous structure and provide details on the development of membrane geopolymers. This metakaolin membrane, based on the geopolymer, was synthesized by a suspension that depends on the fast cementing mechanism of high-temperature slurries. Porous geopolymeric circles provided a homogeneous composition and quantitative distribution of pores. The water absorption, density, impact toughness testing and microstructure analyses were studied. However, considering the promising results, an adjustment in the mix design of the metakaolin inorganic membrane geopolymer mixtures could increase their mechanical properties without negatively affecting the mechanical properties and porosity, making these sustainable materials a suitable alternative to traditional porous cement concrete.

Herein, the effects of multi-walled carbon nanotubes (CNTs) on the mechanical and dielectric performance of hybrid carbon nanotube-woven glass fiber (GF) reinforced epoxy laminated composited are investigated. CNTs are deposited on woven GF surface using an electrospray deposition method which is rarely reported in the past. The woven GF deposited with CNT and without deposited with CNT are used to produce epoxy laminated composites using a vacuum assisted resin transfer moulding. The tensile, flexural, dielectric constant and dielectric loss properties of the epoxy laminated composites were then characterized. The results confirm that the mechanical and dielectric properties of the woven glass fiber reinforced epoxy laminated composited increases with the addition of CNTs. Field emission scanning electron microscope is used to examine the post damage analysis for all tested specimens. Based on this finding, it can be prominently identified some new and significant information of interest to researchers and industrialists working on GF based products.

This study compares the mechanical properties of recycled high-density polyethylene (r-HDPE)/rice husk (RH) composites from a twin-screw extruder and a heated two-roll mill, and the effect of different filler loadings using different melt blending processes on the mechanical properties of r-HDPE/RH composites. Polyethylene-graft-maleic anhydride (MAPE) acts as the coupling agent to enhance interfacial bonding between the fibre and the polymer matrix. The filler loading used was in the range of 10-40 wt. %. In this work, r-HDPE/RH blends were prepared using a twin-screw extruder and a heated two-roll mill. The ratio of 70/30 twin-screw extruder compounded composites significantly showed higher tensile based on improved to about 45.5% at 11 MPa compared to those compounded in the heated two-roll mill. The same ratio showed an increment almost up to 9% of elongation at break. It has also been verified that the higher filler loading used reduced the tensile strength and elongation at break, while the Young’s modulus increased. The result was evidenced by the increase in water absorption and longer burning time as the filler loading increased.

The introduction of carbon nanotubes (CNTs) onto glass fibre (GF) to create a hierarchical structure of epoxy laminated composites has attracted considerable interest due to their merits in improving performance and multifunctionality. Field emission scanning electron microscopy (FESEM) was used to analyze the woven hybrid GF-CNT. The results demonstrated that CNT was successfully deposited on the woven GF surface. Woven hybrid GF-CNT epoxy laminated composites were then prepared and compared with woven GF epoxy laminated composites in terms of their tensile properties. The results indicated that the tensile strength and tensile modulus of the woven hybrid GF-CNT epoxy laminated composites were improved by up to 9% and 8%, respectively compared to the woven hybrid GF epoxy laminated composites.

For ages, concrete has been used to construct underwater structures. Concrete laying underwater is a very complex procedure important to the success or failure of underwater projects. This paper elucidates the influence of alkali activator ratios on geopolymers for underwater concreting; focusing on the geopolymer concrete synthesized from fly ash and kaolin activated using sodium hydroxide and sodium silicate solutions. The geopolymer mixtures were designed to incorporate multiple alkali activator ratios to evaluate their effects on the resulting geopolymers’ properties. The fresh concrete was molded into 50 mm cubes in seawater using the tremie method and tested for its engineering properties at 7 and 28 days (curing). The control geopolymer and underwater geopolymers’ mechanical properties, such as compressive strength, water absorption density, and setting time were also determined. The differences between the control geopolymer and underwater geopolymer were determined using phase analysis and functional group analysis. The results show that the geopolymer samples were optimally strengthened at a 2.5 alkali activator ratio, and the mechanical properties of the control geopolymer exceeded that of the underwater geopolymer. However, the underwater geopolymer was determined to be suitable for use as underwater concreting material as it retains 70% strength of the control geopolymer.

An alternative for Ordinary Portland cement (OPC) consumption is the production and integration of green cement. In other words, the clinker consumption has to be replaced with new low-carbon binders. A possible solution was introduced by the geopolymerisation technology. However, the alkaline activation of geopolymers offers the possibility of obtaining greener materials with high properties, superior to OPC, but due to the high price of sodium silicate, their industrial use is limited. In the past few years, a new activator has been discovered, namely phosphoric acid. This study approaches the obtaining of coal ash-based geopolymers activated with acid solution cured at room temperature. Accordingly, phosphoric acid, 85% by mass, was diluted in distilled water to obtain a corresponding activation solution for H3PO4/Al2O3 ratio of 1.0 and two types of geopolymers were ambient cured (22°C ±2°C). Moreover, to evaluate the geopolymerisation potential of this system (coal ash – phosphoric acid), SEM and EDS analysis was performed to investigate their morphologic characteristics.

The present study describes a method for the determination of As (III) and As (V) in copper electrolytes. The method is based on the separation of As (III) from a copper electrolyte by triple liquid-liquid extraction using a non-polar organic solvent in a medium of 10-12 mol L–1 HCl. The extract contains As (III) and the raffinate-As (V), respectively. As(III) specie can be re-extracted from the organic solvent through the water. Analyzes of the concentration of As in the re-extract and raffinate were performed by ICP-OES spectroscopic method. The average recovery of arsenic by the proposed method is about 99%. Repeatability was estimated with RSD (n = 6). Selectivity and accuracy were proven by the standard addition method. The relative error for restoring the standard addition of As (III) is about 0.3%. The speciation method analysis could be applied for determination of the arsenic species in the analytical quality control of refined copper in copper tanks in the production of copper cathodes.

Nanostructured systems based on ZnO nanoparticles composite systems/polymer fibers have attracted a lot of attention in the last years because of their applications in multiple areas. Nanofibres based on polymers are used in many domains such as nanocatalysis, controlled release of medicines, environmental protection and so on. This work show the synthesis of cellulose acetate butyrate (CAB) nanofiber useful as substrates for growing ZnO nanocrystals and that ZnO is an unorganic metal oxide nanoparticle used to improve the piezoelectric properties of the polymer. The piezoelectric propertiesof ZnO-doped polymeric was investigated with atomic force microscopy and measurements were performed, in contact technique, in piezoelectric response mode (PFM).In order to analyze the structural and textural features, the obtained materials were characterized using advanced physical-chemical techniques such as X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM). The XRD patterns show the characteristic reflections of ZnO with a hexagonal type wurtzit structure and the broad peaks of the polymer. The SEM images reveal the presence of ZnO nanoparticles on top of the polymer nanofibres.In most ZnO-based nanocomposites their morphology is uncontrolled (agglomerated granules), but in ase of using cellulose acetobutyrate this becomes controlled by observing through flower-like structures SEM and AFM) The study of the functional properties of ZnO/polymer fiber composite systems showed that they have piezoelectric properties which give them the characteristics of smart material with possible sensor and actuator applications.Recent literature reports that the synthesis and characterization of ZnO-polymer nanocomposites are more flexible materials for various applications.

Ballistic targets are multi-material assemblies that can be made of various materials, such as metal alloys, ceramics, and polymers. Their role is to provide collective or individual ballistic protection against high-speed dynamic penetrators or kinetic fragments. The paper presents the impact behavior with incendiary perforating bullets having 7.62 mm of ballistic packages made of combinations between Dyneema ultra-high-molecular-weight polyethylene and high entropy alloy from alloying system AlCoCrFeNi, by analyzing the dynamic phenomena (deformation, perforation) that take place at high speeds. The geometry evolution of the physical model subjected to numerical simulation allows a very good control over the discretization network and also allows the export for modeling to nonlinear transient phenomena. The results obtained by numerical simulation showed that the analyzed ballistic package does not allow sufficient protection for values of impact velocities over 500 m/sec.

Setting time in geopolymers is known as the time taken for the transition phase of liquid to solid of the geopolymer system in which is represented in the initial setting and final setting. Setting time is significant specifically for application in the construction field. This study intends to determine the setting time of high calcium fly ash geopolymers and the properties of the geopolymers after setting (1-day age). This includes the determination of heat evolved throughout geopolymerization using Differential Scanning Calorimeter. After setting properties determination includes compressive strength and morphology analysis at 1-day age. High calcium fly ash was used as geopolymer precursor. Meanwhile, for mixing design, the alkali activator was a mixture of sodium silicate and sodium hydroxide (concentration varied from 6M-14M) with a ratio of 2.5 and a solid-to-liquid ratio of 2.5. From this study, it was found that high calcium fly ash geopolymer with 12M of NaOH has a reasonable setting time which is suitable for on-site application as well as an optimal heat evolved (–212 J/g) which leads to the highest compressive strength at 1-day age and no formation of microcracks observed on the morphology. Beyond 12M, too much heat evolved in the geopolymer system can cause micro-cracks formation thus lowering the compressive strength at 1-day age.

Research in additive manufacturing of tungsten carbide-cobalt has intensified over the last few years due to the increasing need for products designed using topology optimisation and multiscale structures (lattice). These products result in complex shapes and contain inner structures that are challenging to produce through conventional techniques, thus involving high costs. The present work addresses this problem using a two-step approach to 3D print parts with complex shapes and internal structures by employing indirect selective laser sintering (SLS) and tungsten carbide-cobalt sintering. The paper takes further our research in this field [1] to improve the part density by using high bulk density tungsten carbide-cobalt powders. Mechanically mixing tungsten carbide-cobalt with the sacrificial binder, polyamide 12, results in a homogenous powder successfully used by the selective laser sintering process to produce green parts. By further processing, the green parts through a complete sintering cycle, an average final part density of 11.72 g/cm3 representing more than 80% of the theoretical density is achieved.

Through taking the cold rolling process as the research object, the three-dimensional finite element model of the strip rolling process is established by using ANSYS/LS-DYNA software. The actual rolling product data has strong consistency with the finite element simulation results. The rolling process is dynamically simulated, and the distribution curves of important rolling parameters such as equivalent stress, control efficiency coefficient, transverse rolling pressure, lateral thickness and work roll deflection is obtained. Based on summarizing the influence of rolling parameters on rolling deformation, the research results of this paper can play an important role in the actual rolling process control. The research results have certain guiding significance for the development and optimization of the rolling control system.

This research paper aims to study the influence of some of the main parameters applied to the electrodeposition process on the nanocomposite layers obtained by strengthening the cobalt matrix with cerium oxide nanoparticles. Thus, the current efficiency (process efficiency) and the degree of inclusion of cerium oxide nanoparticles into cobalt matrix are analyzed according to the current density, the concentration of nanoparticles dispersed in the deposition electrolyte and time of the process. The choice of the optimal parameters imposed on the electrodeposition process lead to the improvement of the quality of the obtained layers, to the reduction of production costs and last but not least to the improvement of corrosion and tribocorrosion resistance of the material. The obtained results show an increase of current efficiency in the process of the deposited layers with the increase of time and current density applied. There is also a slight increasing in the current efficiency of the obtained layers with the increase of the concentration of nanoparticles dispersed in the deposition electrolyte. The increase of the current density, time and the concentration of nanoparticles also have an effect on the degree of embedded CeO2 nanoparticles into cobalt matrix for the studied nanocomposite layers. The degree of inclusion of nanoparticles decreases for the same studied system with the increasing of the current density.

Laser-generated surface patterns provide the means for local mechanical interlocking between the joined materials, tunes the wettability of surfaces that come in contact, and generally are the main factor for bonding strength enhancement, especially between dissimilar materials. This paper presents the influence of different patterning overlays generated with a pulsed laser on the surface of stainless-steel sheets. For all experiments, an overlapping degree of 90% has been chosen between three different patterns, while the engraving speed, pulse frequency and number of passes have varied. The textured surfaces’ morphology was assessed through optical microscopy, and the roughness of the surfaces was correlated with the corresponding experimental parameters. The results have indicated promising insights for joining stainless steel to plastic materials, which is otherwise difficult to assess through usual welding techniques.

Through partially replacing Y element, Ce was added into near-equiatomic AlNiY medium-entropy amorphous alloy (denoted as MEAA) ribbons by the melt spinning process in this study. The differences of microstructure, thermal stability, hardness and corrosion resistance of Al33.3Ni33.3Y33.4-xCex (x = 0, 2, 5, 8, 13) alloy ribbons were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimeter (DSC) and Vickers-type hardness tester. The anti-corrosion performance in 3.5 wt.% NaCl solution of alloy ribbons was investigated elaborately through the general potentiodynamic polarization curves (Tafel) and electrochemical impedance spectroscopy (EIS). Results suggested that all ribbon samples could remain amorphous structure and the hardness are all above 510 HV0.1. With the increase of Ce content, the thermal stability begins to be gradually lower. However, according to the analysis of crystallization kinetics, all types of MEAA ribbons presents the relatively prominent thermal stability compared with traditional Al-based amorphous alloys. The corrosion current density raises firstly, then shows a decreasing trend, and has a slight increase at last. Therefore, appropriate content of Ce element can improve the corrosion protection performance of alloy ribbons and the 5 at.% Ce MEAA ribbons exhibited the excellent corrosion resistance in this study.

In this paper, the microstructure of laser beam welded Sc-modified AA2519-F has been taken under investigation. The welded joint has been produced using Fanuc 710i industrial robot equipped with YLS-6000 6 kW laser beam source. The welding speed and laser power were equal to 0.75 m/min and 3.2 kW, respectively. The investigation involved microstructure observations with the use of both light microscope and scanning electron microscope with energy dispersive spectroscopy (EDS) analysis of chemical composition and microhardness distribution measurements. It has been stated that laser beam welding allows to obtain Sc-modified AA2519-F weld of good quality, characterized by the presence of an equiaxed grain zone containing scandium-rich precipitates adjacent to the fusion boundary.

One of the problems limiting the use of vanadium as hydrogen permeable membranes is its high dilatation upon hydrogen dissolution in it. The information available for the dilatation coefficient value (Δυ/Ω) is contradictory, experimental information on the hydrogen solubility in vanadium within 100-1000 kPa at from 250 to 700°С is very limited. It does not enable to calculate the membrane dilatation. The article contains the measuring results for dilatation of strips made of vanadium foil 100 μm thick in a hydrogen atmosphere in the pressure range from 75 to 1000 kPa, temperatures from 250 to 700°С. The dilatation coefficient (Δυ/Ω) of polycrystalline vanadium was calculated based on the data obtained for dilatation and data previously published for the hydrogen concentration in the α-solid solution at 400°С. It is 0.165. Isobars for the temperature dependence of the hydrogen concentration in vanadium are calculated and constructed using the dilatation measuring results and the dilatation coefficient values. These data are agreed with theoretical and experimental data published previously. The limiting change in concentration and linear dimensions over the cross section of a hydrogen-permeable membrane from V was estimated at various temperatures and operating pressures at the membrane outlet based on the isobars plotted for temperature dependences of the CH/V. The conclusions are made on the optimal working conditions of Pd/V/Pd membranes when hydrogen is released from hydrogen-containing gas mixtures in accordance with Fick’s 1st law and data published previously for hydrogen concentration value at which solid hydrogen solutions in vanadium become brittle.

In this work, influence of NaCl additive on the transformation process of MoO3 to Mo2C under pure CO atmosphere in the range of room temperature to 1170 K was investigated. The results showed that transformation of MoO3 to Mo2C can be roughly divided into two stages: the reduction of MoO3 to MoO2 (the first stage) and the carburization of MoO2 to Mo2C (the second stage). As to the first stage, it was found that increasing the content of NaCl (from 0 to 0.5 wt.%) was beneficial for the increase of reaction rate due to the nucleation effect; while when the content of NaCl increased to 2 wt.%, the reaction rate will be decreased in turn. As to the second stage, the results showed that reaction rate was decreased with the increase of NaCl, which may be due to the formation of low-melting point eutectic. The work also found that morphology of as-prepared Mo2C was irregular and particle size of it was gradually increased with increasing the NaCl content. According to the results, the possible reaction mechanism was proposed.

In this paper, the macroscopic and microscopic deformation caused by sodium penetration in the carbon cathode has been studied during aluminum electrolysis. The distributions of sodium concentration in the carbon cathode has been measured by SEM-EDS. The microstructure change caused by the gradient of the sodium concentration in the carbon cathode has been studied using transmission electron microscopy (TEM). The results indicate that sodium penetration decreases with the increase of the penetration depth. The stresses caused by the gradient of the sodium concentration result in a remarkable change for the microstructure of the carbon cathode. The formation of dislocations resulting in dislocation arrays and the development of kink band networks bring about material damage growth and possibly subsequent weakening of the cathode. These results can provide useful information that is helpful in developing an improved comprehending of the microscopic deformation mechanism of the carbon cathode during aluminum electrolysis.

Despite of extensive researches for decades, there are many unclear aspects for recrystallization phenomenon in the cold rolled Ni-based alloys. Hence, different thermal cycles were conducted in order to determine microstructural evolutions and its effect on the magnetic and mechanical properties of a 90% cold-rolled thin sheet of a Ni-Fe-Cu-Mo alloy (~80 μm). The obtained results revealed that the recrystallization was started at a temperature of 550°C and was completed after 4 hours. An increase in the number of annealing twins was observed with an increase in annealing temperature, which was due to a bulging and long-range migration of grain boundaries during the discontinuous recrystallization. Ordering transformation occurred in the temperature range of 400-600°C and as a result, hardness, yield strength, and UTS were increased, while with an increase in the annealing temperature these mechanical properties were decreased. Maximum toughness was obtained by annealing at 550°C for 4 hours, while the highest elongation was obtained after annealing at 1050°C, where other mechanical properties including toughness, hardness, yield strength, and UTS were decreased due to the grain growth and secondary recrystallization. Moreover, coercivity and remanence magnetization were decreased from 4.5 Oe and 3.8 emu/g for the cold rolled sample to below 0.5 Oe and 0.15 emu/g for the sample annealed at 950°C, respectively.

Optimal parameters setting of injection moulding (IM) machine critically effects productivity, quality, and cost production of end products in manufacturing industries. Previously, trial and error method were the most common method for the production engineers to meet the optimal process injection moulding parameter setting. Inappropriate injection moulding machine parameter settings can lead to poor production and quality of a product. Therefore, this study was purposefully carried out to overcome those uncertainty. This paper presents a statistical technique on the optimization of injection moulding process parameters through central composite design (CCD). In this study, an understanding of the injection moulding process and consequently its optimization is carried out by CCD based on three parameters (melt temperature, packing pressure, and cooling time) which influence the shrinkage and tensile strength of rice husk (RH) reinforced low density polyethylene (LDPE) composites. Statistical results and analysis are used to provide better interpretation of the experiment. The models are form from analysis of variance (ANOVA) method and the model passed the tests for normality and independence assumptions.