bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of magnesium calcium alloys improved by rare earths addition for medical implants
Authors: Savin A , Novy F , Craus ML , Iftimie N , Steigmann R , Istrate B , Munteanu C 
Published: September 2020

Abstract
Biodegradable materials are used as alternative implants for orthopedic applications due suitable strength, fatigue resistance, ductility and biocorrosion resistance which are features for biodegradable implants. Mechanical properties can be improved by adding alloying elements. The decrease of the corrosion rate of Mg can be induced by modifying the structure and phase distribution. Thus, Mg alloys have been designed to meet the requirements of bone repair implant materials by adding = Calcium and Yttrium or Gadolinium. Mg based alloy with Ca and Y/Gd had been proved to be a biocompatible material, osteoconductive and biodegradable and can be used in bone repairs. The system is defined as Mg100-(n+x) Ca(n) RE(x), varying the RE concentration in order to slow the degradation process. Beside morphological combining characterization SEM, EDX, with non-invasive testing is required to be carried out the determination of mechanical characteristics. The interest in this study is to analyze the influence of RE over elastic properties of these alloys in order to choose the best values appropriate with human bones, using Resonant Ultrasound Spectroscopy and ultrasound method.
Monitoring techniques for carbon fibers reinforced plastics used as complex structures
Authors: Savin A , Sturm R , Bergant Z , Stanciu M D , Steigmann R , Dobrescu G S 
Published: September 2020

Abstract
Carbon fiber reinforced plastics (CFRP) have become an indispensable part of modern life. CFRP materials continue to be used in a large number of applications ranging from aerospace systems to automotive, industrial and consumer products. CFRP have evolved both in reinforcement and matrix. The epoxy resin was the most usually matrix for CFRP. The reliability of these materials is essential, especially when it comes to safety-relevant components. The service life of CFRP components is affected by aging processes or improper use. Nondestructive evaluation methods which can be applied for examination carbon/epoxy laminates, manufactured by autoclave processing method with different ply stacking sequences [0]8 and [(45/0)2]s are presented. The samples were realized from 4 plates of carbon-epoxy manufactured at the Faculty of Mechanical Engineering, University of Ljubljana, Slovenia. The paper present influence of thermal treatment and stacking sequence on damage delamination’s due to impact about mechanical properties. Ultrasound and electromagnetic nondestructive evaluation methods are used for good localization of damage and characterization composite materials and other techniques can provide complementary information once the damage location is known.
Practical method of obtaining different levels of seismic energy dissipation using viscous fluid protective system on bridges
Authors: Scheaua F 
Published: September 2020

Abstract
In order to achieve an optimal stability performance during transient vibratory actions the damping method is used for the bridge structures. Conventional approach would dictate that a structure must inherently attenuate or dissipate the effects of transient inputs through a combination of strength, flexibility and deformity. The damping level is being at low values at a conventional elastic structure and hence the amount of dissipated energy during transient vibratory actions is also in very low value. In the event of an earthquake, conventional structures usually perform high deformations which when situated beyond their elastic limits can cause the collapse. In such cases most of the dissipated energy amount is absorbed by the structure through localized damage as it fails. The concept of supplemental dampers added to a structure assumes that most of the energy amount input to the structure from a transient vibratory action will be absorbed, not by the structure itself, but rather by supplemental damping elements. Properly implemented, an energy dissipation system can be able to simultaneously reduce both stress and deflection within the structure elements. The fluid viscous protective system concept is presented as an optimum energy dissipation solution for bridge structure types. The operation of these devices is on the hydro-static principle of fluid flow through orifices of a special diameter value. In this paper it is presented an innovative functional and constructive model of fluid viscous device based on a practical design method which allows the controlled operation regime regarding the viscous fluid flow inside the device cylinder being able to provide considerable resistant force levels to relative motions between a bridge structural frames where is mounted and achieving considerable amounts of seismic energy dissipation when an earthquake occurs. For the constructive method of fluid viscous system model is adopted a practical constructive method aiming the direct control on the circulated fluid flow rate so that the device response force should be considerably larger, acting for limiting the relative movement of the structural frames and without introducing additional stiffness to the structural system to which it is attached, due to the elasticity of the working fluid type used. It represents an innovative method because of the special design orifices for fluid flow rate control used which, depending on the specific diameter values, can provide device different response force values and implicitly different dissipated energy amount levels based on the characteristic represented by the resistant force variation law according to the piston stroke.
The two-dimensional fretting contact with a bulk stress. Part II – Loading history and dissimilar elastic materials
Authors: Spinu S 
Published: September 2020

Abstract
The contact model for similarly elastic materials advanced in the companion paper is enhanced to account for the more general case of contacting bodies with different elastic properties. The latter contact model, involving dissimilarly elastic bodies under partial slip, is particularly difficult to solve due to the mutual interaction between the normal and the shear tractions. As opposed to the contact of similar elastic materials, pressure is affected by the shear tractions and vice versa. Therefore, the contact submodels in the normal and in the tangential direction are not independent. The connection can only be overcome in an iterative manner, by adding a new external loop to the contact algorithm, in which the solutions of the systems in the normal and in the tangential directions are mutually adjusted by successively solving both systems until convergence is reached. Moreover, with friction being a dissipative process, any state depends upon the process path, i.e., on all previous states attained during the loading history. The contact model is solved as a series of quasi-static states that are expected to replicate the loading path. Two levels of iterations are added to the model of similarly elastic materials, described in the companion paper, to account for the dissimilarity in the elastic properties. The contact process is reproduced on a prolonged loading history, consisting in the first fretting loops. The distributions of contact tractions are obtained using a technique for the fast computation of convolutions involving the fast Fourier transform. The conducted simulations prove the method robustness and its application in the modelling of the fretting processes.
Researches and constructive solution to enhancing the stiffness of the gantry type milling machines
Authors: Stan G , Zichil V 
Published: September 2020

Abstract
For machining of large size work pieces, CNC milling machines with moving bridge (known as Gantry Type milling machines) that have a large distance between the bridge columns, i.e. 4 to 7 meters are frequently required. This leads to a difficult guiding, driving and stiffening of the moving bridge. At the same time, the moving bridge is required during the cutting process by a number of forces, some of them fixed, others variable. The manufacturers of such machine tools sort out this problem by a “suitable” sizing of the moving bridge that involves large overall dimensions of the bridge, with major implications on its guiding. This work presents an innovative solution concerning the increase of the stiffness of the Gantry type bridge, so that the geometrical accuracy of the machine is preserved regardless the force variations in the guiding system of the moving bridge. This work sets out an interdependent connection between the variation of the requiring forces generated at a high extent by the location of the moving elements on the cross rail and the compensating forces in the guiding of the two columns of the bridge.
Contact stress simulation problem in case of thermal spray coatings
Authors: Stescu C , Chicet D , Tufescu A , Istrate B , Munteanu C , Strugaru-Iacob S 
Published: September 2020

Abstract
In this study was addressed the problem of the contact stress simulation, generated in the case of the loads applied on thermal spray coatings, by finite element modelling. Starting from the characteristic lamellar morphology of this type of coatings, consisting of splats, voids, oxidized or unmelted particles, the studied layers were assimilated to an anisotropic material. Thus, it was tried to establish the parameters necessary for modelling, so that they define as accurately as possible the studied material. The purpose of this study was to identify the maximum value of the tension developed in the point contact, on the depth of the analysed layer. This value was subsequently used to determine the limit values for in practice use of the coatings.
Improvement of machine tool accuracy through ball screw location optimisation in relation to the guideways of the axes
Authors: Stoica A , Stan G 
Published: September 2020

Abstract
An important role in obtaining a high positioning accuracy is also played by the location of the ball screw in relation to the guideways of each axis. This makes that noncompliance with the Abbé principle to lead to higher positioning deviations. The compliance with the Abbé principle is difficult to be achieved from the constructive point of view because the cutting forces differ in terms of direction, sense and value within the working space of the machine tool. This work develops a mathematical model that allows finding the location direction of the ball screw in relation to the guideways, so that the positioning accuracy is increased. The conditions that may influence the improvement of the positioning accuracy by increasing the guideway stiffness and settling the dimensions of the moving element are studied in this work, as well. The mode of locating the position encoder in case of direct measurement that, together with the noncompliance of the Abbé principle leads to affecting the positioning accuracy is also presented. The results have been obtained experimentally on a milling machine where the ball screws have been located symmetrically in relation to the main guideway.
Influence of cutting parameters on surface hardness in milling of AL6061T6
Authors: Tampu C , Chirita B , Cristea I , Zichil V , Schnakovszky C , Herghelegiu E , Carausu C 
Published: September 2020

Abstract
Milling is an important industrial common machining operation used to produce complex surfaces. Surface quality in milling operation is influenced by various factors such as cutting speed, cutting feed, depth of cut and chemical composition of the material. Surface quality is defined by roughness, residual stress and microhardness and is important in determining corrosion resistance and in fatigue crack initiation. The aim of the present paper is to analyse the influence of above-mentioned cutting parameters (cutting feed, cutting speed, depth of cut) on surface microhardness. Tests were conducted using a Coro mill 490 with a single insert that was indexed for every experiment, thus eliminating the influence of tool wear. Al 6061-T6, a material widely utilised in aircraft, defence, automobiles, and marine areas due to its good proprieties (good strength and lightweight) was used. Microhardness was measured on workpiece surface but also in the cross section of the workpiece, up to a depth of 1mm, in order to observe material state in subsurface layer. It was observed from the results that an increase of cutting speed have led to an increase of microhardness while a higher value for depth of cut has led to a lower value of microhardness. Feed rate has generated similar results with the depth of cut.
The process of optimizing the radial sliding bearing
Authors: Turof M 
Published: September 2020

Abstract
The problem of optimizing the bearing choice process, caused by the failures due to the short life of the bearings, caused by the difficult working conditions, is becoming more and more frequent.
By further optimizing the type of bearings used, we aim to both improve efficiency and productivity and reduce costs.
For the choice of a radial sliding bearing, the three basic steps are followed: calculation of the diameter of the shaft, verification of the bearing pressure, thermal calculation. If at least one of the last two is not appropriate, the designer must change the material, the cooling conditions or the length / diameter ratio and then recalculate the bearing.
The methodology of optimizing the choice of bearings involves the establishment of a set of initial constraints to reduce arbitrary recalculations.
In optimal design, we eliminate the drawbacks presented in usual design and we impose at the beginning some restriction for shaft material, deflection, cooling capacity, we determine the type of fit and tolerances, that is neglected in usual design.
Characterization of drying behavior and modeling of industrial drying process
Authors: Vasić M , Radojević Z 
Published: September 2020

Abstract
The general method for industrial chamber dryer optimization was reported in this paper. The first step in finding the most suitable drying regime is to characterized the clay raw material, especially its water loss at 2000C and to determine the critical drying rate inside the specially constructed laboratory dryer. These data provides us information if the product or the dryer is the bottleneck for the optimisation. If the optimization is justified geometry of the dryer, air mass flows, temperature, and humidity profiles inside the dryer as well as initial water content in the drying material, initial temperature of the products and the load of the dryer are required. Some of the previously mentioned data are only used to check if the chamber dryer is working properly, while the others are used as the initial parameters necessary for software simulation. In this paper two models for calculating the optimal drying parameters were used. The first model was developed from the comprehensive theory of the moisture migration during isothermal drying. The calculation software for setting up the non - isothermal drying regimes was reported in our previous papers. It is important to say that this model was not able to adequately predict the temperature raise within the drying products. In order to simulate the raise of the temperature of the roofing tiles during drying the second model was used. This simple receding drying front model was firstly reported by Kitcher. If both models are used simultaneously it is possible to calculate air temperatures, product temperature, absolute and relative humidity of the drying air, moisture content of the product, drying rate etc… It is important to mention that this approach can lead to the recommendations for changes inside the dryer before an optimized situation is achieved. One example of such situations is described in this paper in details.
Natural zeolites: prospects for heavy metal polluted soil remediation
Authors: Bocharnikova E A , Shabayev V.P. , Ostroumov V.E. , Demin D.V. 
Published: September 2020

Abstract
The environmental concerns related to oil extraction, transportation and refining include the pollution with heavy metals (HMs). Currently, there is a growing interest in the study of an influence of silicon-rich materials, including such natural minerals as diatomite, zeolite, and others, on the HM behavior in the environment with regard to their exploitation in soil remediation strategy. In greenhouse pot experiment, the effects of natural zeolite on the biomass of barley plants grown in artificially cadmium (Cd)-contaminated soil and Cd uptake and translocation were studied. Zeolite applied to soil at a low rate (0.15%) mitigated the Cd phytotoxicity and provided the same plant biomass production as in uncontaminated soil without zeolite. Zeolite stimulated development of root system. The application of zeolite at a low rate enhanced the phytoextraction process–cleaning up the soil from HM at the early (booting) stage of plant development.
The formation of nanoparticles in the process of ultrasonication of the pure water
Authors: Ivanova D D , Gorbachevskii M V , Novikov A A , Kuryakov V N 
Published: September 2020

Abstract
Ultrasonication is a very convenient method for the preparation of various dispersions. However, it is often not clear what influence the ultrasonication procedure is on the purity of the prepared dispersion. In this paper, we show that the prolonged ultrasonication of the pure water results in dispersion formation. We characterized the nanoparticles in the resulted dispersion by the TEM, DLS, conductivity, and zeta potential measurements. This work points to the possible source of contamination of the sonicated dispersions.
Monitoring of mechanisms of formation of corrosive aggressiveness of soils and grounds of underground gas pipeline routes and on its basis assessment of service life of gas pipes in various soil-climatic zones
Authors: Khudyakov O I , Reshotkin O V , Demin D V , Velikotskiy M A 
Published: September 2020

Abstract
The experience of studying the problem of corrosive aggressiveness of soils and grounds in terms of improving the reliability of Gazprom’s pipeline systems operation is summarized and presented. Soil factors causing surface corrosion of gas pipelines in soil conditions are studied. Based on the obtained results, it was suggested to evaluate not only the corrosive aggressiveness of soils and the gas pipe lifetime, but also the corrosive resistance of pipe metal in corrosive environments. Special attention is paid to the stress corrosion cracking formation mechanism.
Study on rheological properties of clayless drilling fluids influenced by fractional composition of carbonate weighting agents
Authors: Leushevaand V A Morenov E L 
Published: September 2020

Abstract
Study of the influence of weighting-bridging agents on technological parameters of drilling fluids is an important aspect in the development of washing fluid compositions, especially when drilling-in productive formations. At selection of weighting agents, it is often assumed that these substances are inert and do not affect the structural and rheological parameters of the fluid, but only increase the density (due to higher specific gravity) and lower the filtration parameters (due to an increase in the solid phase content). Paper presents experimental study to assess the effect of the fractional composition of carbonate weighting agents on structural and rheological parameters of a biopolymer drilling fluid used to drill-in a reservoir. Carbonate substances with an average particle size of 5 to 150 microns were used as weighting-bridging agents. Based on the data obtained, dependences of the main structural and rheological parameters of the drilling fluid on the size of the weighting-bridging agent’s fraction are revealed.
Method of signal identification based on wavelet analysis.
Authors: Loginov V A , Elnikov A V 
Published: September 2020

Abstract
The article presents the results of the development of a method for identifying the source of vibroacoustic impact on the sensitive element of the fiberoptic perimeter protection system of industrial facilities. The methodology was tested on the identification of signals from the following sources of vibroacoustic impact: impact over a certain period of time, or shaking the fence (t-impact); short-term impact type impact (ẟ-exposure). In the course of the work, polygon tests of the perimeter security system were conducted, a library of signals was compiled, and characteristic features of signals of various types of impact on the sensitive element of the system were identified. The main signal processing tools are the Fourier and wavelet transforms.
Biodegradation of polymer compositions with pro-oxidants
Authors: Lukanina Yu K , Popov A A , Khvatov A V 
Published: September 2020

Abstract
Oxo-biodegradable plastics are widely used as an alternative to well-known polyethylene and polypropylene. thanks to the polyolefin base, they have the necessary set of operating characteristics and are able to be processed with the same parameters as for example polyethylene. The presence of prooxidant in their composition ensures its oxo-destruction after the end of the product’s service life with the subsequent biodegradation of the obtained material fragments. The combination of a natural filler and a pro-oxidant additive in polymer compositions makes it possible to obtain a material with a programmed life and destruction
Thermal properties of polyethylene compositions with micro-and nanocellulose
Authors: Perova A N , Usachev S V , Koverzanova E V , Khvatov A V , Lomakin S M 
Published: September 2020

Abstract
The effect of micro- and nanocellulose addition on the thermal properties of polyethylene compositions has been studied by means of thermogravimetric analysis and pyrolysis-gas chromatography-mass spectrometry. The main temperature characteristics of the thermo- and thermo-oxidative degradation of the compositions are determined. The influence of micro- and nanocellulose additives on change of the distribution of hydrocarbon pyrolysis products of composite materials was established.
Study of hydraulic resistance in collapsible pipelines
Authors: Seoev L V , Drozdov D A , Plotnikova K M , Elkin A V 
Published: September 2020

Abstract
The features of conducting research on hydraulic resistances of collapsible pipelines with a bell and spigot joint are shown. The importance of taking into account the influence of pipe joints on the flow of the pumped liquid, as well as deviations from straightness due to angular mobility, is noted. Data on the determination of pressure losses in collapsible pipelines PMTP-100 and TSR-MK-100 based on the results of tests carried out on sections of 1200 m long when pumping water are presented. The values of Darcy friction factor are also set. As a result of processing experimental data using mathematical statistics, the values of the coefficient of equivalent roughness of the inner surface of pipes of prefabricated pipelines PMTP-100 and TSR-MK-100 were determined. Using the methodological apparatus of hydraulic modeling, calculations were made to simulate the pumping of various groups and brands fuels through collapsible pipelines. In the analysis of the data revealed that by reducing the coefficient of equivalent roughness of the inner surface of pipes, supply pipeline TSR-MK-100 can be higher than by pipeline PMTP-100 on average, 5-13%.