bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical elimination of asbestos materials
Authors: Necasova K , Buchta P
Published: August 2019

Asbestos was a frequently used material in the past, mainly in the construction industry, on account of its excellent thermal and chemical resistance. Nowadays, all uses, handling and disposal of asbestos materials are subject to strict legislation due to health hazard. This work is a research of an efficient chemical way to decompose these materials with the lowest energy costs possible so that the method could compete with patented thermal decomposition and other currently common methods. Decompositions were performed at room temperature with acids, namely hydrochloric, sulfuric, phosphoric, acetic and oxalic acid and the results were evaluated based on mass analysis. Asbestos rope and asbestos-cement roof tile were used as samples. From the experiments carried out, the best decomposing agent was hydrochloric acid for the rope sample and acid mixture (hydrochloric and acetic acid in a 1:1 ratio). for the roof tile sample
Behaviour of calcined gypsum-based materials during setting
Authors: Dolezelova M , Jerman M , Vimmrova A
Published: August 2019

The behaviour at early age of several composed gypsum-based materials was investigated. The binary binder, composed of calcium sulphate hemihydrate and slaked lime, several ternary binders with different types of pozzolans were prepared, and their behaviour during setting was studied. Unrestrained volume changes of calcium sulphate-based pasts were measured by displacement of liquid, in which the specimens were submerged. The hydration heat of composed binders was measured by isothermal calorimetry. The behaviour of composed materials with different types of pozzolans was compared with the behaviour of calcined gypsum.
The assessment and prediction of concrete sustainability
Authors: Vymazal T , Teply B , Hrabova K
Published: August 2019

The sustainability of concrete and concrete structures is seeing increased attention; among other things, this is because 5% of global CO2 emissions are produced by cement manufacturing. Responsible sustainability management requires effective tools for the quantification, i.e. measurement, or comparison of material, technological, and structural options. This is why there are a number of initiatives and approaches that aim to reduce global greenhouse gas emissions. Their project design uses techniques that assess whole structures and their usage; however, most of their input data is based on estimates. This paper presents a validation of a method of designing, assessing, and predicting sustainability for one material (concrete) with regard to its composition, relevant properties, and predicted value dispersion utilizing probabilistic approach.
Thin films deposition on 304L stainless steel using e-gun technology for medical applications
Authors: Baila D , Tonoiu S
Published: August 2019

The purpose of this article is to characterize surface of 304L stainless steel coating by e-gun technology with thin films of Ta2O5 and ZnO. ZnO films are used in pharmaceutical industries, in cosmetics and in medicine, grace of their better anticorrosive, antibacterial and photo catalytic properties. Ta2O5 films have rapidly evolved in medicine research with the promise of development of new types of biomaterials used in medicine. Ta2O5 coatings present an excellent biocompatibility, good dielectric properties, and high corrosion resistance. The biomaterials are realized by novel and special methods to resist of the biological reactions that occur in medical implants (protein adsorption, cell adhesion, cell growth, blood compatibility, etc.). The most important surface properties are physical properties, durability and biocompatibility. The physical properties of a biomaterial that must to be measure, are mechanical strength, permeability and elasticity. Biocompatibility is the response of the biomaterial or of the device to the proteins, cells and organisms action, when the implants are in contact with the biological tissue. The common method to characterize biomaterial surfaces are: contact angles, ESCA (XPS), Auger Electron Spectroscopy, SIMS, FTIR-ATR, STM, SEM and EDAX.
An approach with genetic algorithms to improve the workstation space planning
Authors: Belu N , Nitu E L , Gavriluta AC , Ionescu L M
Published: August 2019

Industry 4.0 is characterized by the use of digital solutions and computational technologies. The proposed paper presents a workstation space plan solution using an intelligent computational approach: Genetic Algorithms. On the one hand, we have the operator’s effort represented by the motion trajectories in the normal work area. On the other hand, the production flow requires some constraints on the sequence of the assembled components or their location. Considering both the constraints and the reduction of the operator’s effort, the planning solution proposed in this paper ensures the improvement of the working process by applying the principles of motion economy under the conditions of the constraints required by the production process. The resulting sequence and type of the components and operator effort for the production process is indicated to the operator on the modular workstation. Furthermore, the component placement can be adapted to the characteristics of the production process or of the operator’s needs (left handed, has some disabilities, etc.). The solution proposed in this paper was applied in an experimental laboratory where components from the automotive industry are assembled.
Some aspects of prototyping oversized parts through PolyJet technology
Authors: Carausu C , Negru R , Serban D A , Turc C , Belgiu G
Published: August 2019

The paper presented a series of experiments to improve the performance of rapid prototyping processes. The paper presents aspects regarding the realization of polymeric parts by PolyJet rapid prototyping technology. Achieving oversized parts on printers whose print size is small is subject to additional demand for the designer and the technology engineer who designs the printing strategy. Small parts segmentation is a solution, provided that after gluing the parts with adhesives recommended by the manufacturer, the general assembly acts as a one-piece piece – this is the ideal case. An acceptable solution is that the overall assembly has at least 70-80% of the properties of a part made up of a single piece. In the present work several sets of specimens were used for the experiment and they were joined together. Their properties were compared to one-piece specimens. Finally, the useful conclusions for designers and technologists are presented.
Thin coatings for pumping station mechanical components
Authors: Paleu C Cirlan , Paleu V , Istrate B , Cimpoesu N , Munteanu C
Published: August 2019

The pumping stations are key points of water treatment plants, their performance directly affecting the serviceability of the entire water treatment system. The excessive wear of mechanical components conducts to pumping station out of service state. The deposition of thin coatings on the elements subjected to wear can generally extend the operating time of the water treatment plants. The paper analyses the failure modes of the mechanical components of the pumping stations and the existing efficient solutions for thin coating deposition to protect them from excessive wear. Consequently, an effective coating is deposited on the raw metal by Atmospheric Plasma Spraying (APS) and tribological tests are developed for an initial assessment of the anti-wear properties of the coating. The worn contact surfaces are analysed by Scanning Electron Microscopy (SEM) and the chemical composition is established by Energy-dispersive X-ray spectroscopy (EDS). The tests are still in development, revealing that the main failure modes of the coating are abrasive wear and delamination. Future research will be conducted to identify the best combination of powders for a multiple layer deposited coating with high wear resistance.
Manufacturing analysis with discrete events using IoT platform
Authors: Ciortea E M
Published: August 2019

The paper presents how to integrate cloud systems and access them with IoT devices. The IoT platforms addressed in the paper are Platform as a Service (PaaS) and Software as Service (SaaS). The analysis is presented by modeling a case study for systems with discrete events. Because the general system is analyzed as a cloud system on levels, we will leave the general system as stochastic.Qualitative analysis has the role of checking the structural and behavioral properties of the system, the existence of bottlenecks, bridging, and security systems. The quantitative analysis measures the specific performance of the manufacturing system. The results show that this approach can be used to detect jams in the system. Thus, manufacturers can resize production capacity and optimize even the entire manufacturing system.
Study of some heat treatment effects on thermodynamic and structural properties of Ti-Ta biomedical shape memory alloys
Authors: Costache C , Apostol V , Pricop B , Lohan N-M , Comaneci R I , Bujoreanu L-G
Published: August 2019

The shape memory effect (SME) in binary β-Ti alloys is associated with a reversible martensitic transformation from α”- orthorhombic martensitic phase to β-bcc austenitic phase. The present paper reports the experimental results obtained on TiTa alloys, containing 25, 30, 35 and 50 mass % Ta. The specimens were processed from as-cast levitation induction melt ingots, cut by wire electric discharge, hot/cold rolled (enabling to obtain 500-mm long thin ribbons), solution treated (900°C/30 min/water quenched, W.Q.) and aged (300°C/1 h/W.Q.). From each heat treated state, samples were cut for tests meant to emphasize the presence of thermal and mechanical memory behaviour. Thermal memory was highlighted by SME-work generating training cycles, investigated by cinematographic analysis. The respective results were corroborated with those recorded by dynamic mechanical analysis (DMA). Mechanical memory was revealed by winding-unwinding and tensile tests. The winding and tensile tests offered information about the capacity of cold rolled ribbons to memorize their room temperature (RT) profile. Tensile tests were applied up to complete failure or by RT loading-unloading cycles.
The influence of the surface preparation of aluminium alloys for brazing upon the hardness of the assembly
Authors: Dimitescu A , Alecusan AM , Babis C , Dascalu L
Published: August 2019

The wider use of aluminum and its alloys also involves specific technologies for reconditioning and repairing the various components. Specialist studies have shown that a more advantageous technique, from an economical point of view, than welding with less polluting and good mechanical properties is brazing. The only disadvantage of this process is the stage of preparing the surfaces to be assembled.

Specialty literature and many published papers provide detailed information with direct reference to the mechanical and physical properties of aluminum alloy assemblies refurbished by brazing depending on the surface preparation mode.

The present paper aims to make a study, based on experimental data, on how the surface preparation influences the hardness of aluminum alloy assemblies refurbished by brazing. The areas of the base materials, the filler material as well as the thermal diffusion zones resulting from the brazing operation will be studied.

The main problem is the difference in hardness between the materials to be assembled and the material with which they are assembled. This can be a major cause, which can generate defects in operating cycles by lowering the strength of the assembly. By choosing an optimal surface preparation technology, we can reduce these differences by obtaining an assembly with uniform properties in all its structure, so with a longer service life.
Sustainable anti-corrosive protection technologies for metal products by electrodeposition of HEA layers
Authors: Florea R M , Carcea I
Published: August 2019

The purpose of this paper is to study the electrochemical synthesis of thin films of multi-component alloys with improved structures and properties to ensure optimal protection of metallic materials used in extreme environments against various types of corrosion, oxidation and wear. Electrochemical deposition is an inexpensive alternative to thin film synthesis because it does not require complex or costly equipment and uses readily available raw materials. This simple method offers the possibility of depositing thin layers on substrates of complex geometry and can be achieved at low process temperatures with reduced energy consumption. Electrodeposition allows easy control of chemical composition, morphology and thickness of coatings by varying deposition parameters. HEA alloys are usually developed by physical methods, most commonly by casting-melting. Mechanical alloying and rapid solidification are other synthesis processes used to obtain structural materials. HEA coatings have also been obtained by various deposition methods, such as magnetron-sputtering and laser deposition. In this paper is investigated the microstructure, mechanical properties and oxidation behaviour of HEA coating obtained by electrochemical deposition.
Effect of grain refinement on mechanical and corrosion behavior of AZ91 magnesium alloy processed by ECAE
Authors: Gajanan M N , Narendranath S , Satheesh Kumar S S
Published: August 2019

AZ91 Mg alloys were processed by equal channel angular extrusion (ECAE) up to 4 passes through route-R. The increase in number of ECAE passes to yield fine-grain structure in the bulk Mg alloy with a more dislocation density, this enhances mechanical properties and corrosion resistance. Indeed, microstructural observations revealed an equiaxed and significant grain refinement after ECAE-4P, with a mean grain size (d) of ∼ 4.36μm. Further, the tensile strength, micro-hardness and corrosion resistance were also increased, however the elongation was reduced with the increasing of ECAE passes. The electrochemical polarization test in 3.5wt % NaCl solution revealed a noticeable enhancement in the corrosion resistance of ECAE processed AZ91 Mg alloy compared with the as-received Mg alloy. This is mainly due to grain refinement and distribution of secondary phase particles in Mg alloy matrix during ECAE-4P.
XPS, XRD, and SEM characterization of the virgin and recycled metallic powders for 3D printing applications
Authors: Gorji N E , O’Connor R , Brabazon D
Published: August 2019

We characterized the surface and microstructure of both feedstock (virgin) and recycled Stainless Steel 316L powders used for selective laser melting process. Reusing the recycled powders can significantly reduce the powder consumption, production cost and time. We have performed X-ray photoemission spectroscopy (XPS), Scanning electron microscopy (SEM), X-ray Diffraction (XRD) and rheology analysis on steel powders both on the virgin powder and the powders not adhered to the printed parts but recycled in the powder bed. The results confirm that the oxygen level on the surface of the recycled powder is increasing and the metallic oxides diffuse out to the surface of the powder particles during the manufacturing process. Nevertheless, the changes are not significant which promise the reusability of the recycled powders for several cycles. We observed no change on the phase of the recycled powder. Further characterizations are ongoing to measure the chemical composition and morphology of both virgin and recycled powders to correlate them with the mechanical properties of the printed parts. These characterizations allow extending the powder reuse for a number of reusing cycles and reducing the manufacturing time and cost without reducing the mechanical properties of the final parts.
Thermal cutting of thermomechanically rolled S700MC and heat-treated S690QL steels
Authors: Gorka J , Poloczek T
Published: August 2019

The article describes the impact of oxygen, HD air plasma and laser beam cutting processes on structural changes and quality of the surface of thermomechanically treated S700MC and heat-treated S690QL steels. Taking into account good quality of obtained cut surface, particular attention shall be attached to the structural and chemical changes due to the impact of the heat cycle. Those modern steels are especially susceptible to a loss of their properties during the heat interaction in thermal cutting processes. The quality of the surfaces after thermal cutting processes were evaluated in accordance to ISO 9013:2017 (bevel angle, surface roughness, rectangularity tolerance). Also, measurements of cut widths and breakthrough holes diameters were accomplished. In the next stage the hardness measurements and metallography examination were performed. The following devices were used for this purpose: metallographic light stereoscopic microscope Olympus SZX9 and Wilson Wolpert 401 MVD for Vickers’s hardness measurements.
Developing structures for the construction of the processing equipment - Case study
Authors: Iordache M D , Costea A , Malea C , Nitu E , Rizea A
Published: August 2019

The evolution of the manufacturing processes requires, as a mandatory condition, to increase the performance of the technological equipment for processing, assembling and control, by promoting new solutions in the field of devices of the semi-finished products, but also by developing special or modular multifunctional components for the modernization of machine tools. This paper proposes a method of optimization of the technological process and equipment, which in the first stage determines, on the basis of a technological chart, the optimal sequence and the number of operations or phases of processing, and in the second step with the global utility method, the optimal combination of special or modular structures, from existing or new ones, is determined for the construction and configuration of a flexible multislot machine for simultaneous and successive centring and spherical operation. We believe that the creation of tools, devices for orientation and fixing, tooling, support, guidance, reinforcing and transfer blanks and modernization of machine tools, is an important measure to streamline manufacturing systems involving important material effort. Our theoretical and experimental research and industrial applications in recent years aim to develop new structures, processing systems and equipment with features, performance and especially flexibility, superior to existing ones.
Investigation of machining parameters on corner accuracies for slant type taper triangle shaped profiles using WEDM on Hastelloy X
Authors: Manoj I V , Joy R , Narendranath S , Nedelcu D
Published: August 2019

Wire electro-discharge machining (WEDM) is a widely used machining process for machining of difficult to cut materials, which are used in precision profile applications like dies, metal stampings, and gas turbine parts. In the present research work, a new slant type taper fixture was used to obtain angular machining of triangular shape slots of sides 1mm, 3mm and 5mm machined both in 0° and 30° as slant angles on Hastelloy X. The corner radius and corner errors were investigated for different machining parameters like corner dwell time (CDT), offset distance (WO), wire guide distance (WGD) and cutting speed override (CSO) using L16 orthogonal array for both the slant angles. SEM micrographs indicated that corners were with lower radii at 30° than in 0° slant profiles, at lowest and highest cutting speeds. The main effects plot showed that the corner radius increases with the increase in wire offset and wire guide distance parameters. The increase in corner dwell time has an adverse effect on the corner radius. The triangles were machined at different cutting speeds from 0.47 to 1.51 mm/min with various parameters; it was observed that as the corner radius decreases the corner error also reduces. However, the corner radius and corner error can be minimized by selecting an optimized cutting parameter.
Experimental results regarding industrial filtration using ultrasonic filters
Authors: Nitoi D , Amza Gh , Petrescu V , Zoia A , Petriceanu C
Published: August 2019

The paper presents general description of an ultrasonic air filter used in industrial air filtration system and the experimental results obtained. The method can be used in air purification system from the highly polluting processing technology of an industrial shop (paint shops, foundries, welding constructions, forging, etc.). The ultrasonic system construction and the advantages of using ultrasounds in the pollutant air filtration and purification process and an ultrasonic filter designed are here presented. In this case, the transducer which is the most important element consist in two asymmetrical passive elements (reflector and radiant element). For the ultrasonic system design there are presented the principal theoretical elements and in the final the finite element analyze of the whole ultrasonic system. To start a different filtering system some considerations like the following are important: the construction should be as simple and easy to install in the working zone, do not require dismantling to clean the filter element, cleaning periodically when the pressure drop reaches a limit value by commanding the operation of the ultrasonic transducer, allow restraint of the finest particles leading to the final consumer (in some technological processes) pure air, have a much longer operating life than conventional filters, in the sense that the ultrasonic activated filter elements have a higher reliability, to achieve a pressure drop in a range of restricted values, practically to be kept constant or with very small variations, creating stationary waves to allow not only very fine particle retention but also air drying, allow easy maintenance, the operating costs of which do not exceed the costs of the classic ones.
Study of the influence of surface roughness parameters on the frictional characteristics of materials
Authors: Pena-Paras L , Maldonado-Cortes D , Martinez C , Arias M , Ontiveros A , Castanos B , Morales-Martinez M
Published: August 2019

The study of surface roughness parameters and their correlation with coefficient of friction (COF) is of great importance for metal-mechanic applications. Evidence suggests that Ra (surface roughness average) is not directly related to COF under sliding conditions. In this study, the relation between surface roughness parameters, namely Ra, Rt (maximum height of the profile), Δa (mean slope of the profile), and COF, as well as their interactions, were particularly studied. The materials were of an aluminium alloy Al A380. Samples were chemically attacked to modify their surface roughness characteristics. Six different conditions were tested: Al A380 with the surface attacked with an alkaline substance for 0, 2.5, 5, 15, 30 and 60 min. The value of COF was determined using a T-05 block-on-ring tribotester, and surface roughness data was obtained using an optical 3D surface measurement system. MathWorks MATLAB software was used to process the data. Results show that Δa has a strong positive correlation with COF during sliding conditions, whereas both Ra and Rt may vary without directly affecting COF, contrary to the commonly used industry standard.
Processing effects on tensile superelastic behaviour of Fe43.5Mn34Al15 ± XNi7.5∓X shape memory alloys
Authors: Popa M , Pricop B , Comaneci R-I , Gurau G , Vollmer M , Krooss P , Niendorf T , Bujoreanu L-G
Published: August 2019

Fe43.5Mn34Al15Ni7.5 was introduced in the current decade as a new superelastic alloy with great applicative potential due to: (i) superelastic behaviour over a thermal range of 200°C and (ii) recoverable strains up to 9.7 %. One of the key factors in enhancing the superelastic response of several shape memory alloys (SMAs) is the formation of an oligocrystalline structure, i.e. without triple junctions between grains, which is the result of an abnormal grain growth (AGG) process that can be induced by cyclic heat treatment (CHT). Considering that, up to present date, no systematic observations were reported on the effects of Al substitution with Ni, the present study aims to analyse precisely these effects of on the structure and properties of Fe43.5Mn34Al15-xNi7.5+x, where x = 0; 1.5 and 3 at. %. The ingots with the five above mentioned compositions were: (i) cut by wire electrical discharge machining (WEDM); (ii) hot rolled (HR) at 1060°C with 43.7-70 % thickness reduction degrees; (iii) annealed (A) at 900°C/1h/water, (iv) cold rolled (CR) with 60-92.7 % thickness reduction degrees; (v) cut by WEDM under the configuration of tensile specimens; (vi) subjected to CHT between 1225 and 900°C with heating-cooling rates of 10°C/min (repeated three times) and final water cooling to 80°C before being subjected to (vii) final ageing (AT) at 200°C for 3 hours/water. After applying this complex thermomechanical procedure, the specimens were analysed by optical microscopy (OM) and the average diameter of crystalline grains was calculated based on dimensional measurements. Considering that the approximate specimen thickness was 1 mm, since the average grain size of thermomechanically treated specimens ranged between 1.3 and 3.7 mm, it can be concluded that oligocrystalline structure, characterized by grain size larger than specimen’s thickness/diameter has been obtained. Tensile tests were performed on thermomechanically treated specimens, both up to failure and by loading-unloading. The evolution of average hardness, during the five processing stages, HR-A-CR-CHT and AT was determined and discussed.
Modelling of the visco-elastic pendular hybrid system with dissipative rolling elements
Authors: Scheaua F
Published: August 2019

The construction industry has seen a remarkable development in recent decades, making it possible to build infrastructure elements capable of withstanding considerable demands on traffic, wind or seismic actions. These achievements have been made due to the solutions used for isolation against dynamic actions that may require the structure at a given time. In order to ensure the protection of construction structures against seismic actions, many constructive solutions have been developed which can be mounted inside the resistance structure. These are mechanical systems used for isolation and seismic energy dissipation, which by operation are able to modify structural behaviour at earthquake. A hybrid seismic isolation model is described which is classified under the building base isolation systems category. This system consists of concave roller elements in combination with elastomeric shock absorbing elements. An experimental model has been developed and analysed, and the results are presented in terms of accelerations in time and frequency at the level of the structural elements at which the recordings are made during excitation simulating the action of a seismic event. The isolation system is used on the low model of a bridge or viaduct structure. Analyses are made for different models of insulation system layout at the isolated structure and distinct cases regarding the construction of the component parts regarding the rolling elements in contact with the concave surface. The results are presented for each structural element in part describing the registered values of acceleration due to the excitation on the supporting pier and the superstructure over the three main directions of movement according to the constructive type of the rolling elements that are included in the isolating system. Experimental analysis was performed on a small-scale system under laboratory conditions, based on a set of simplified assumptions. The advantage of this approach is supported by multiple possibilities of simulation of real dynamic loading situations, static and dynamic loading states, structural and functional schemes and functional configurations of the supporting and isolation systems against dynamic actions. Thus, the transfer of experimental results from reduced models to real systems through mathematical and computer models associated with them is ensured by appropriate transfer functions.
Study on reducing pollutant gases and particulate content inside the passenger car
Authors: Vranau A M , Bujoreanu C
Published: August 2019

The pollutant gases entering the car through the ventilation system are very harmful and the effect they have on the human body is often lethal. The European Environmental Agency is talking about over 45000 “premature deaths” that occur annually due to the particles in the atmosphere. A rigorous monitoring of pollutant content in the passenger compartment is absolutely necessary, therefore the appearance of the first pollen filter in 1940 by Nash Motors on the Weather Eye ventilation system. Studies conducted by researchers in Germany show that not all systems work the same way, and the degree of air filtration is only 40% for some cars, while other cars filter outdoor air up to 90%. The most car manufacturers recommend the filters replacing, and huge gaps exist between a classic particle filter (it captures and retains dust, pollen and soot) and one with active carbon that also captures unpleasant odours. In reducing the amount of pollutant gases entering the passenger compartment, the air quality sensor (AUC), mounted in the pollen filter housing, also controls the activation of the recirculation function when the car enters a polluted area. Our paper presents an overview in the field of pollution in the passenger compartment, the main types of passenger car filters launched on the market and the importance of their use according to the manufacturer’s indications.
The behaviour of “liquid wood” when exposed to some physico-chemical factors
Authors: Barhalescu M L , Jarcau M , Poroch–Seritan M , Costescu E , Vaideanu Dorin , Petrescu T C
Published: August 2019

Because of an ever-increasing demand of non-toxic, biodegradable, naturally-sourced materials and products, the human society is always searching for new materials with specific applications, which are able to fulfil the above-mentioned requirements. Consequently, it is essential to identify the qualities of these materials and their behaviour when subjected to various external factors, in order to find their optimal solutions for application in various domains. Such a material, obtained from renewable resources, is known as “liquid wood”, a material which exhibits composite polymer-like properties, having a lignin matrix. “Liquid wood” can be found in three different forms: Arboform, Arbofill and Arboblend, depending on the natural substances (besides or associated with lignin), which are to be found in the material – resins, wax, vegetable fibres etc. As such, “liquid wood” has been subjected to various external factors, the aim being to determine the degradation of the material when acted upon by environmental factors. Thus, “liquid wood” has been immersed in distilled water and then in an alkaline environment and in an acid environment for 210 days. Measurements were periodically performed to determine the mass variation and the change of electrical properties when subjected to the specific environmental factors and to UV radiation. The changes were determined by comparison with standard samples. Following this study, it has been observed that the main degradation factor is water, which leads to cracking and then fracture in the material. Furthermore, significant changes have been observed in the electrical properties of the material and in the pH of the environments in which it has been immersed. These observations lead to the idea that the material is hydrophilic. The results obtained following the immersion of “liquid wood” in distilled water and then in an alkaline environment and in an acid environment point towards some of the possible application of this material in various fields of activity, which may have a significant positive impact upon the environment.
Experimental researches on the tribological analysis of composite materials sintered with iron matrix
Authors: Caliman R
Published: August 2019

In this paper a study is conducted on the abrasion wear behavior of iron matrix composite materials, testing of samples obtained by sintering was made for different values of the applied load as for the relative speed of sliding. Starting from the studied literature, recipes of sintered sintered metal composite materials having iron matrix have been developed which have been tested for their physico-chemical and tribological properties. The prepared powders were dosed according to the formulations (Fe 68%, Cu 13%, Ni 5-7%, Graphite 6%, SiC 8%, SiO 2 8%), and the resulting mixtures were homogenized to achieve homogeneous mixtures to ensure, finally, a good reproducibility of the physico-mechanical properties of the sintered material. For forming, a cylindrical die having a surface area of 2cm2 was used. Working pressures ranged from 5000 ÷ 6000daN/cm2. The densities obtained for the compressed samples were determined by weighing the METTLER analytical balance and measured with the micrometer for the volume calculation. The values of „raw” densities range from 5.12 to 6.3g/cm3.
Numerical modelling of structural behaviour of URM panels strengthened with cement matrix composites
Authors: Ghiga D A , Taranu N , Ungureanu D , Isopescu DN , Scutaru MC , Hudisteanu I
Published: August 2019

Unreinforced masonry (URM) structures represent a large share of the dwelling stock, traditional industrial buildings and historical heritage of mankind. Most of the URM structures have been built with little or, in some cases, no seismic provisions. In order to overcome this drawback, the application of external reinforcement layers, especially those made of composites, to improve the structural behavior of masonry structures has been a research focus area during the past decades.

The aim of this paper is to propose and assess a simplified and accepted Finite Element (FE) modelling strategy to simulate the diagonal compression test of the URM walls strengthened with glass fibre meshes embedded in a cement-based mortar. In the case of masonry walls strengthened with composites reinforced with glass fibre meshes, both the masonry material model and the modelling and the meshing of the composite strengthening system need to be addressed by taking into account the complex phenomena that characterise the bond interaction between the glass fibre mesh, mortar and the masonry support. The FE analyses were developed with reference to the experimental tests available in the current literature and, according to the preliminary outcomes of an experimental program which is currently under development at the Faculty of Civil Engineering and Building Services, Iasi.
Interlaminar failure investigations on delamination growth of composite laminates
Authors: Hudisteanu I , Taranu N , Isopescu D N , Munteanu V , Ungureanu D , Scutaru M C
Published: August 2019

The investigation of the interlaminar damage evolution on multi-layered composites as well as the numerical modelling techniques available for the simulation of the interface delamination are still a current concern. The complexity of modelling the mechanical behaviour and fracture modes of composite laminates is increased because of the anisotropic behaviour of the material, the fibre arrangement or other important parameters, such as stacking sequence, fibre orientation angle and the configuration of the composite laminates. Different failure modes may occur on multi-layered composites, which can lead to significant stiffness and strength reduction or to the complete loss of the load carrying capacity. The interlaminar stresses are the main factors responsible for the initiation and growth of the interlaminar failures such as delamination. They may occur as a result of manufacturing defects, low-velocity impacts or as an effect of the presence of the free edges. The delamination onset can lead to serious problems such as the premature buckling of the laminates, moisture infiltration, and stiffness degradation or even to progressive delamination growth and the separation of the layers of the composite laminates. The paper presents the numerical modelling of a multi-layered composite subjected to the tensile opening fracture mode as well as the investigation of the delamination growth. The purpose of the analysis is to study the delamination evolution on a symmetric composite laminate, starting from a pre-existing initial crack, at the interface between the adjacent layers from the middle plane. Thenumerical modelling approach for the simulation of the delamination evolution is conducted based on the Cohesive Zone Method. The results are presented in terms of the total displacement jump and equivalent stress distributions on the layers of the composite laminates.
Assessment of the rehabilitation benefits by finite element method
Authors: Dimitrescu A , Babis C , Chivu O , Dascalu L
Published: August 2019

Cruciform fillet welded joints are found in many industrial applications. Welded structures are often subjected to load cycles due to loads that can vary in position and value. As a result of these loads, the phenomenon of fatigue occurs. Fatigue consists in the occurrence of failures, after applying a large number of load cycles, of loads below the yield limit of the material from which the structure is made. Fatigue mattempts have to be carried out over very long periods of time and are very expensive because of the expensive machines. A method by which the fatigue behavior of fillet welded joints can be predicted is the finite element method. The paper proposes to investigate by the finite element method, the fatigue life of some cruciform-fillet-welded specimens, making a comparison of two applied rehabilitation techniques.
Modeling of stress and strain states induced by torsion of straight rods with elliptical cross sections
Authors: Glovnea M , Manolache-Rusu C , Suciu C
Published: August 2019

Torsion of bars of various cross-section is of great practical utility in engineering, structural design and mechanical work. It is applied in machine construction, steel bridge or railway construction. Many publications can be found in literature that present the stress-strain analysis in the case of straight rods with constant profiles subjected to torsion. Most of these works were however directed to the case of rods with simple connected domains as cross sections. The present work uses a semi-inverse method which permits to determine general equations for stress-strain analysis in the case of rods having a multiple connected domain as cross section, subjected to torsion. For the present study, the general equations were customized for two particular cases that of an elliptical cross section and that of an elliptical ring.The determined analytical equations were implemented to a specific situation by aid of Mathcad software. This permitted to graphically represent the distribution of torsion stresses and cross-section deflection.
CFD analysis of a hybrid, Darrieus-Savonius, horizontal wind turbine, using static and moving mesh
Authors: Grabowski L , Sobek M , Baier A
Published: August 2019

Changes in the ecological spirit of the world lead to the need for usage of additional ways of obtaining clean energy. With help comes solutions to use wind energy. In the world, there are numerous commonly used, various kinds of wind turbines of different sizes, numbers of generated power and the different place of use. They are increasingly used as household wind turbines to improve the ecology and a marked decrease in household spending. Moreover, it was decided to use an innovative, previously unused connection of two separate types of wind turbines. The approach to turbine positioning is also innovative. Due to the use of its horizontal orientation and purpose to mounting on the roofs of the buildings, to do not exceed the specified size limits in building regulations. It also allows increasing the number of applications of this solution. With the use of Darrieus - Savonius turbine increasing of the range of the wind speeds, which are able to spin a turbine is achieved. In the case of higher efficiency, the Darrieus turbine operates at high wind speeds, while the Savonius turbine at lower wind speeds. Two separate solutions have been coupled with each other by claw clutch, which allows the rotation of only one part or two parts of the turbine depending on the prevailing wind conditions. The CAD model of the turbine was made and then the turbine was subjected to advanced CFD analysis. Initially, analysis of the air course around the turbine was performed, using statistical and analytical data on wind speeds prevailing in Poland, within the areas of single-family houses. The approximate values of the wind flow streams and the torque which ultimately is moving the electric generator were determined. The subsequent CFD analysis was performed using the moving FEM mesh, mapping the actual velocities of the turbine blades. The turbine blades revolved at velocities close to the obtained analytical speed of the shaft and turbine components. Airspeeds were analysed in the case of the shape of the flow of streams. The pressure of the air around the turbine was also analysed, the value of which could be used to add strength analysis using FEM method. The main purpose of the test was to determine the torque acting on the engine. Thanks to this information, it was possible to determine the energy efficiency of the turbine and select the appropriate elements, such as the generator, bearings etc. The obtained information has also had an impact on the final shape of the turbine’s executive elements. Thanks to performed analysis, it was possible to obtain proper turbine performance parameters without conducting expensive, real, experiments. In the end, the prototype of this Darrieus – Savonius turbine was manufactured.
Nondestructive testing sensor using semiregular architecture with folding ligaments
Authors: Iftimie N , Savin A , Steigmann R , Stanciu M D
Published: August 2019

In present, much more studies on patterned structures composed of periodic unit-structures have been performed. These studies mainly based on the electromagnetic wave propagation, because the variation of physical properties of the patterned structure depends on the change in the unit-structure. Structural topology optimization has made remarkable progress over the past decades. The periodic topology of many periodic cellular makes the analysis of their wave propagation characteristics particularly interesting. This paper presents the results obtained at the electromagnetic testing using a structure in a semiregular arrangement with “exotic” behavior. The CAD/CAM models of reconfigurable folding architecture were designed in the multiple flat unit cells structure considering that the kinematics of a structure with ligaments is function of the angle in the XY horizontal plane. It was followed in response to the modification of the architecture and the size of the structure, their response to the interaction with the electromagnetic field. The simulation of the operation of the wavelength excitation process, first realized theoretically using the Finite Difference Time Domain (FDTD) method, was performed using specialized XFDTD software.
A sliding grid based method for the roll decay simulation
Authors: Lungu A
Published: August 2019

The paper describes a novel technique meant to support the numerical prediction of the roll decay for a ship hull equipped with bilge keels in an attempt of establishing a methodology for accurate prediction of the damping forces which occur during the oscillation. The numerical simulation is achieved by making use of the ISIS-CFD solver, part of the FineTM/Marine package available in the NUMECA suite. The solver is based on finite volume method to build the spatial discretization for the governing equation to solve the incompressible unsteady RANSE in a global approach. Closure to the turbulence is achieved by making use of the detached eddy simulation model which has been found as being enough accurate. All the computations are performed in respect to an earth-fixed Cartesian reference frame with only one degree of freedom i.e. roll motion. The validation of the computed solution is done through the comparisons with the experimental data.
DES-based computation of the flow around the DARPA suboff
Authors: Lungu A
Published: August 2019

Flow modelling is a key issue not only for the correct prediction of hull-propeller interactions, manoeuvring characteristics and the flow field in the stern region of any marine vehicle, but also for the correct estimation of the fuel consumption. The paper describes a thorough investigation of the hydrodynamic performances of the DARPA suboff hull. The flow is numerically simulated by integrating in time the unsteady Navier-Stokes equations in which closure to the turbulence is achieved by means of a modified detached eddy simulation (DES hereafter) technique. The solver used for the purpose is the ISIS-CFD, part of the Numeca FineTM/Marine suite, which employs the finite volume of fluid technique. A comparative analysis between the numerical solutions based on the DES and explicit algebraic stress model (EASM hereafter) are provided in an attempt to sustain the choice for the turbulence model in the present study. Extensive parallel computations are carried out on 120 processors for which comparisons with the experimental data prove the accuracy of the chosen investigation methodology. A grid convergence test is performed for verification and validation purposes.
On the bending vibration of a train driving wheelset
Authors: Mazilu T , Gheti M A
Published: August 2019

The driving wheelset is used on the traction railway vehicle to support a part of the vehicle’s weight and for traction and braking purpose. The driving wheelset consists of the axle on which the two wheels and the driving gear are rigidly attached. The bending vibrations in the driving wheelset may be caused by variations of the vertical wheel/rail contact force. In this paper, a mechanical model of the driving wheelset, consisting of a free-free uniform beam with three rigid bodies, representing the axle, the two wheels and the driving gear, is considered. Using an analytical method for solving the equations of motion for the model, the steady-state harmonic behaviour of the bending vibrations is analysed. The frequency response function and the impact of the position of the driving gear upon this function are pointed out.
Including GNU Octave in a numerical programming C++ rapid development software context for research models
Authors: Oanta E , Pescaru A
Published: August 2019

The paper is included in the strategy to use API facilities of CAD/CAE commercial applications and dedicated programming languages, such as GNU Octave, in order to create a set of instruments useful for the rapid development of the hybrid models. In this way, an exploratory investigation is presented regarding the most appropriate methods to use GNU Octave scientific programming facilities in C++ applications. Four software demonstrators are included in the paper, which may be used as an inspirational environment. Each program presents relevant aspects regarding the C++ API. The first demonstrator presents two methods to start the Octave interpreter, depending on its current version, and the use of the ‘feval()’ function for ‘gcd()’, ‘acos()’ and ‘inv()’. The type of the input and output values of ‘feval()’ are ‘octave_value_list’, being necessary appropriate conversion functions. The second program is dedicated to the built-in-functions, being presented three case studies. The third demonstrator presents the conversion of the values from a user defined C++ type to the Octave types, i.e. the conversion of a two dimensional array into a ‘Matrix’ Octave type,which is tested using the ‘norm()’ function.The fourth program uses ‘source_file(OCT_script_file)’, which executes the commands in the OCT_script_file\ The content of this file is written from a string and it is either a set of Octave commands, or the name of another Octave script file which is executed. We have solutions to minimise the access time spent due to the frequently write operation on the disk. We plan to continue our tests in order to find the best methods to use the GNU plotting facilities to develop graphical interpreters.