bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical modelling of the composite materials structure used for leisure crafts
Authors: Dumitrache C L , Dumitrache R , Faitar C , Buzbuchi N
Published: September 2020

For a leisure craft, chosen materials are mainly made of fibre reinforced composite. This type of materials have more advantages than disadvantages, having a good resistance to corrosion, resistance to impact, are reducing vibrations, are light and are easy to use during construction including maintenance and repairing. In the practice of using composite materials, the most common structural element is the lamina. Within the calculation of a composite material structure, there can be various approaches: to ignore the layering of the composite laminae, considering them isothropic or orthotropic and they can be calculated as standard metallic structures or to consider the layering of the composite laminae, but to ignore the exact orientation of fibers into the matrix. For the calculation with finite element method is used COSMOSM/MATLAB software and it includes several types of laminae, with or without layers. It is carried out a comparison of the results from COSMOSM software, MATLAB software and finite element, being observed a good consistency between the results of the software and the calculated results by other authors. It is worth noting that the study of the specialty literature shows that several programs have been designed to calculate the strength of laminates, but they are meant for internal use. Given that the strengths of laminates can be efficiently calculated, although the calculations may be complicated, it becomes obvious the importance to design such a software program.
Prediction of cutting forces in drilling AL6082-T6 by using artificial neural networks
Authors: Efkolidis N , Dinopoulou V , Kakoulis K
Published: September 2020

This research investigates the comparison of the thrust force (Fz) and cutting torque (Mz) predictive models based on artificial neural networks (ANN). The models were developed based on three-level full factorial design of experiments conducted when drilling of Al6082-T6 alloy material with cutting speed, feed rate and tool diameter as the process parameters. The predictive ANN models of thrust force (Fz) and cutting torque (Mz) were developed using a multilayer feed forward neural network, trained using an error back propagation learning algorithm. The developed models are shown capable of predicting them (Fz and Mz) to a great level. The confirmation experiments provided favorable results with accuracy of 4% and 4.5%, for the thrust force (Fz) and the cutting torque (Mz) respectively. Furthermore the R coefficient for the prediction model of the thrust force is 0.99608 and 0.9946 for the cutting torque. As a result they can be considered as very accurate and appropriate for their prediction. This study promotes the better machining quality and the sustainability of the process that are achieved at the same time
Doubling the power of a wood boiler with fixed grill
Authors: Garleanu G , Garleanu D , Borda C , Luchian C , Dumitras M
Published: September 2020

The article presents one technological modality of doubling the thermal power of a wood boiler. The base of departure is a wood boiler with fixed grill with a power of 30 kW and a yield of 62%. The technological variant is to increase with maximum 50% of the value of the heat transfer surfaces and modify the water circuit. For this, a FEM thermal transfer simulation program was used. In the first part of the article is presented the initial 30 kW wood boiler with the heat transfer surfaces. With the help of the FEM program, a thermal transfer simulation was performed. The results of the program were compared with those of the technical characteristics of the wood boiler. The authors of the article carried out different simulations with new surface types, changes in the water circuit, heat transfer calculations, fluid flow angles, so that the efficiency reaches over 75%. The design results were put into practice and the new wood boiler was built. The power of the wood boiler reached a maximum of 75 kW. The article presents some of the intermediate stages of execution. The wood boiler was tested in a specialized installation. It can be seen that the efficiency increased by 18%, from 62 to 80 and the thermal power reaches a maximum of 75 kW. The hot water flow is about 60 l / min, a very good value considering the type of wood boiler. Using the experimental results presented in this paper, wood boilers can be designed with much smaller dimensions having the same characteristics of power and water flow.
Considerations about the friction inside on a transversal coupling
Authors: Gavrila C C , Lates M T
Published: September 2020

The paper presents, starting from some kinematic aspects as rotations and translations between the Oldham coupling parts, some kinematic equations useful in determining of intermediary element position depending by the transversal misalignments. Then, using the inside translational movements between parts, the friction coefficient between adequate materials to be used are studied. The friction which appears between the coupling parts has an important influence on their dynamic behaviour, wear and lifetime. The most significant friction and also wear is given by the translational movements between parts. Due to this, the study of the friction between some materials to be used in coupling manufacturing is required, but also difficult because of some particularities, as reduced parts translational movements for reduced transversal misalignments between shafts, or the alternative translational movement in translational joints. In the paper final part the results and conclusions are presented.
Modeling of mechanical properties of dissimilar joints using the FEM approach
Authors: Gwiazda A. , Topolska S.
Published: September 2020

Modeling of connections in CAD class systems enables conducting simulation tests of entire structures. It gives the opportunity to reduce costs and speeds up the design process itself. Programs using the finite element method (FEM) are the oldest (over 40 years of history) and the most popular tools for modeling objects and physical processes. It is an absolutely necessary component of the knowledge of every modern engineer. In contrast to physical modeling (see below), in which quite approximate models are used, the MES program can model structures in great detail. But the calculation time for this reason can be relatively long. However the advantage of using CAE systems is the ability to understand the behavior of the object in real conditions, to conduct a numerical experiment under the influence of: load, vibration, temperature, etc. with the use of computer calculations and simulations. The paper presents the use of an advanced CAD / CAE class system for modeling complex technological joints of mechanized mining supports manufactured using the welding technology. One of the most important problems in manufacturing and repairing of mining support using the welding technology is the method of welding the dissimilar joints and analysis of its characteristics. It is particular important for the repairing procedures. A case of such approach is presented in the present paper.
Mathematical development of an efficient three-dimensional workflow for industrial manufacturing systems
Authors: Ibrahim A J , Abduljaleel Y W , Al-Maliki S J B , Al-Khayat Z Q , Albaali G
Published: September 2020

The increasing rate of challenges and competitions that face industrial projects alongside the vast fluctuations in the various related variable, whether human, material or economic nature, have forced decision-makers and researchers to examine all the related technological production dimensions. The three-dimensional 3D array of technological production is formalized and examined in comparison with the relevant two dimensional 2D and one-dimensional 1D ones. The analysis of the general principals of conventional technological systems and the theoretical productivity of technological systems with different types of capacity technological areas were used as the base in order to develop a qualitatively new high efficient, continuous action, low-cost technological system. Flow-helical technological module FHTM was developed in order to ensure an effective solution for a complex automated production processes scheme that ensures sufficient rising of technical and economic indices of manufacturing for a wide range of industries.
Reconditioning by Welding of the Spiral Heat Exchangers Made of Austenitic Stainless Steel - X2CRNIMO17-12-2
Authors: Ionescu F , Solomon Ghe , Gârleanu G , Gârleanu D , Dijmărescu MR
Published: September 2020

The heat exchangers are playing an essential role in some widely used systems including automobiles, heating, refrigeration, air conditioning, distillation, in thermal power plants, district heating and as annexes to thermal machines. During the use of the heat exchanger, different phenomena occur due to the flow velocity of the fluids, the viscosity and the hardness of the microparticles in the fluid. The main causes of defects are corrosion and rubbing. In the presentation of heat exchanger repairs is considered a problem in terms of cost, time and efficiency. The method of repairing a spiral heat exchanger is the uncovering, which is cut outside the inside towards a sheet (s) of the exchanger when it is defective. The repair is performed by cutting the changing sheets from close to the access to the defective area. This paper presents a new method of repairing the heat exchanger, namely the intervention from the inside to the outside. The experimental plan consists of the following steps: choosing the basic material; choice of the reconditioning by welding; choice of filler material; re-welding and non-destructive examination of the samples.
Hydrodynamic loads and wake dynamics of a propeller working in oblique flow
Authors: Lungu A
Published: September 2020

Most of the small crafts and navy ships are equipped with propellers mounted on inclined shafts as thrusters. In spite of its importance, the information on the forces generated by inclined shaft propellers is scarce. To help the designers of small craft and navy ships, the present research describes a systematic numerical program undertaken to evaluate the propeller performances when inclined in respect to the oncoming flow. Scale resolved incompressible Detached Eddy Simulation (DES hereafter) or Delayed Detached Eddy Simulation (DDES) technique are employed by using a volume of fluid approach to study the four-blade propeller recommended in 2015 Tokyo Workshop on CFD Ship Hydrodynamics for the ONR tumblehome ship model 5613. A series of three working conditions are numerically analyzed over a range of shaft inclinations and advance coefficients. Besides, the usual shaftline thrust and torque, horizontal and vertical side forces are computed. The results of these simulations confirm the expectations that a propeller mounted on an inclined shaft produces less thrust than the same propeller on a horizontal shaft. This paper contains propeller characteristic curves and lift- and side-force data which are directly applicable in the design of both high-performance small craft and commercial ships.
Numerical Investigation of the Minimum Gap Impact on the Screw Compressor Efficiency
Authors: Malael I , Bucur I O , Slujitoru C
Published: September 2020

The screw compressor is a positive displacement machine, with two rotors - driver and driven. In this paper, the influence of minimum gap, between the rotors of an oil injection screw compressor, on the efficiency was investigated. Two cases were analysed, in which the minimum gap ranged from 40 to 60μm, respectively 20 to 40μm. The geometrical model, the physical properties and the initial values represent the input data for the used thermodynamic model. Starting from the 3D CAD model, the computational domain for the stator part was defined, which is composed of three subdomains: suction side, oil inlet and pressure side. The grids for the stator were generated with Ansys Meshing, whereas the meshes for the rotor subdomains were made using the TwinMesh software. In the end, smoothing functions were used to increase the mesh quality. To simulate the flow through the screw compressor, the commercial software of CFD ANSYS CFX was used, employing the SST turbulence model. In the analysis the rotational speed was 6000rpm, with a suction pressure of 2bar and a discharge of 10bar. Using the “opening” type limit conditions with the required pressure, both the air flow variation and the oil flow variation were determined.
New methods and equipment for the machining of cross-axes parts- Case study
Authors: Malea C I , Iordache M D
Published: September 2020

The processes and equipment for manufacturing, assembly, and control operations, adapted to the needs of modern industry, shall be determined according to the volume of production and the technical conditions imposed, at a level which ensures economic effects on the recovery of costs for their design and execution. The design-optimization algorithm, with the four working steps, applied on the case study presented, allows the determination of the optimal number and succession of technological processes, but also of new processing methods, based on a technological graph and optimization criteria. In the second step, determine for each technological operation the optimal orientation and fixation scheme of the analyzed part, combining elements of the set theory and the global utility method, with a method of simultaneous optimization of the orientation and fixation fundamentals for two different transformation areas with distinct quotas and conditions that need to be achieved. In the third step, is identified and analyzed several construction variants of structures for the equipment. By formulating a technologically adapted graph to describe structures of orientations, but also other structures, is obtained an associated mathematical model and optimization criteria for the optimum design variant of the orientation and fixation at the analyzed operation. When is desired a complete appreciation of all the technological operations, the fourth step of system optimization is proposed, which is also based on a technology graph and an associated mathematical model adapted to the evaluation of the analyzed types of equipment.
Microstructure characterization of HfNbTaTiZr High Entropy Alloy Processed in Solid State
Authors: Manea C A , Geambazu L E , Bololoi R V , Mateş I , Miculescu F , Sohaciu M G , Csaki I
Published: September 2020

This work investigates the alloying degree of HfNbTaTiZr high entropy alloy in equimolar percentages from raw, high purity powder, using solid state processing, for further uses in coating work components in harsh environments like marine, geothermal or oil and gas industry. The combination of elements was chosen according their properties, tailoring the composition for the final purpose. The alloying has been performed in a planetary ball mill with stainless steel vial and balls in a protective argon atmosphere to prevent oxidation, contamination or ignition and N-heptane as a process control agent to improve the material’s behavior during welding and re-welding in mechanical alloying process. Samples were taken at regular periods of time and analyzed to check the alloying degree evolution and to establish the optimum parameters for milling, best results being obtained at a speed of 300 rpm for 180 min (effective time) providing an alloying degree over 50% was achieved.
Statistic mathematics – instrument for solving some problems in maintenance activities in the shipyards
Authors: Manea E , Zăgan R , Militaru E
Published: September 2020

The organizational performance plays a fundamental role in the context of the increasing market competition, so that the chance of survival in this competition is considerably favorable for those organizations that very quickly discover and minimize their vulnerabilities and, moreover, implement management performance tools, which facilitates the detection, explanation and resolution of the various shortcomings of the management activities, the main objective being the competitiveness increasing. In the most general way, the study of maintenance involves the calculation of certain numerical indicators that aim to determine the reliability level: the probability of uninterrupted operation over a period of time; probability of success (functioning); the probability of failure (failure). Probability theory and mathematical statistics are applied in the field of engineering sciences where there are conditions of risk and uncertainty and where it is necessary to make some rigorously argued decisions. The probability theory studies random events, that is, those experiences that, repeated several times, occur each time differently, the result being not possible to be anticipated. The random variable, if a series of measurements is made, it is a notion that gives information about the value number of the measured size, as well as the frequency of occurrence of a numerical value in a row. This paper aims to illustrate, by means of justifying examples, the opportunity to use probability theory in solving complex problems from the maritime vessels shipyard maintance and repairing activity, conditioned by uncertainty, risk and variability. By the examples presented and considered to be illustrative, the authors of this paper consider that a mathematical model based on the theory of probabilistic calculations could provide a solution for satisfying the need to predict how efficiently the time required for carrying out the maintenance work of the ships in the drydock and / or on the berth in a shipyard, as part of the maintenance program required by the classification societies.
Energy and exergy analysis of a VCRS working with R600a within a thermodynamic analysis
Authors: Memet F
Published: September 2020

The most significant concerns related to vapour compression refrigeration systems (VCRS) refer to environmental behaviour and energy efficiency. The present study is taking into consideration the refrigerant R600a due to its very good thermodynamic properties and environmental position. On the other hand, the maximum performance of such a system will be identified by the help of the laws of thermodynamics. This is due to the fact that the analysis based exclusively on the energy analysis will not reveal where the performance of the system is degraded and how intense. After the formulation of the specific mathematical background, within the analysis have been varied the evaporation temperature in the range (–22, –8) ° C. Exergy losses in the main components of VCRS were assessed; the energy and exergy efficiencies of VCRS – as well. Resulted that the system is working at its highest efficiency for the highest evaporation temperature considered: for te = –8°C, the energy efficiency is 2,7 while the exergy efficiency is 55%. The most inefficient component part was found to be the compressor, while the most efficient is the evaporator. Such an analysis is very useful when aiming the design, the optimization and performance assessment of VCRS.
Modelling of the energy transfer during scrap melting in microwave furnace
Authors: Mitrică D , Șerban B A , Olaru M , Burada M , Dumitrescu D , Bănică C. I.
Published: September 2020

Efficient recovery and processing of metal waste is a priority for today’s economy. Several technologies are dealing with the recovery of metals through furnace melting but the extraction efficiencies are rather low. The paper studies the influence of heat transfer, produced by the action of microwaves, on the melting of metal waste batch. Correlation equations of the heat flux transmitted through the crucibles inside the oven were calculated by means of MATLAB modeling. Specific dimensions for the furnace enclosure were used in the paper. The simulation results were than compared to the experimental findings, to verify the model. The experimental stage consisted in the melting of aluminum and copper waste in the microwave installation, at laboratory level, and at the optimized parameters of the system.
Analyse of dynamic operation mode for drilling machine equipped with drill for pits digging
Authors: Muscă (Anghelache) G. D. , Potîrniche M. A. , Căpățână G. F.
Published: September 2020

The working part of drilling machine is the drill. It is the one that performs soil dislocation, crushing, evacuation and depositing around the pit. Drilling machines with a drill operate according to dry rotating drilling method, where dislocation and evacuation of drilled soil are performed by the drill. To perform this, the drill is subject in the same time to rotation and vertical push-down. Milling cutter type equipment for pits digging was 3D generated in Mechanical Desktop. Cutter model was introduced in Algor medium and automatically digitized by this. After digitization, the user introduces in Algor the supporting set and loading set for all situations. The user has only available the possibility to refine the digitization within the entire model and not only in areas of interest (as it is mostly wanted). Two real situations were considered and analysed wherein the work equipment during digging process can be found: front stress on the cutter teeth performing material cutting and front stress on cutter teeth and body that go inside material and perform centring. In both situations, supporting has tried to follow real situations wherein work equipment components subject to analysis can be found. In both loading situations, it is noticed that the operating part is not at risk to crush under stress. It is also noticed that displacements of the knots belonging to analysed structures do not have greater values in either situations.
An Analysis of The Drawing with Aluminum Brazed Sheets
Authors: Olaru I
Published: September 2020

This paper analyzes drawing of aluminum sheets joined by brazing. Drawing is the transformation of a plan workpiece into the drawn part or workpiece, transformation with decreasing of depth corresponding transverse dimensions. The brazing process is based on the difference by the melting points of the base materials and filler metal. During the brazing process, the aluminum sheets to be assembled are heated to a temperature between the melting temperatures of the two alloys, this process tends to modify the geometry and the microstructure of the brazed sheets. In various industries such as automotive, aerospace, electronics, machine building industry etc., aluminum alloys can be used to replace the steel parts of carcasses (car body). Brazed sheets are widely used in the manufacture of heat exchangers by using an aluminum alloy. These sheets have different thicknesses and are generally made by hot rolling. Aluminum in natural form is very soft and ductile, slightly used due to its mechanical properties. The brazing process is based on the difference in the melting points of the base materials and filler metal. During the brazing process, the sheets to be assembled are heated at a temperature between the melting temperatures of the alloy, this process tends to modify the geometry and the microstructure of the brazed sheets.
Effect of laser cladding parameters on structure properties of cobalt-based coatings
Authors: Poloczek T , Kotarska A
Published: September 2020

The article presents results of microstructure, microhardness and geometry tests of cobalt-based alloys deposited on low-alloy steel by a laser cladding process. As a deposited material MetcoClad 6 powder was used. Powder is characterized by a spherical shape of particles obtained in inert gas-atomization process with a size of -106 +45 µm suited to a variety of hardfacing processes. The experiments were carried out using a disk laser Yb:YAG TruDisk 3302, with a wavelength of 1.03um equipped with a disc powder feeder. The laser cladding process was carried out at various parameters of cladding speed, beam power and powder feed rate in order to obtain layers with low dilution, low porosity and good coating uniformity. Macroscopic studies were performed using a metallographic microscope light stereoscopic Olympus SZX9. Vickers microhardness tests were provided on the cross-section of layers on Wilson Wolpert 401 MVD device.
Creative Simulation Environment for Automation Control
Authors: Pomazan V M , Sintea S R
Published: September 2020

Modern automation control design requires new technologies to develop, test and transfer technology from design to real world. One important step in automation design is testing automation algorithms in a simulated environment appropriate by real world. Our scope is to help designers to create a simulated environment for testing automation control. We created an interface and programming tool which help designers to simulate industrial installation and can connect with automation control equipment, using real electrical signals. Our base equipment is an industrial input/output controller, which connects with the computer. On the computer, is defined and runs a simulation environment, using a software tool. This environment communicates with the real world via an input/output controller. Design engineers can create their own simulation environment, using high level programming language (C++.Net, VB.Net or C#.Net) and can connect their software with external controller, using the proposed tool or a set of objects, from the library that might be added to it. This tool is useful for the creation of a simulation environment for industrial installation or subsection of a plant.
Usage of Coloured Petri Nets for the Performance Evaluation of the Metallographic Samples Analysis Automated Systems
Authors: Pop A , Blaga F S , Ursu M P , Vesselenyi T , Bungău C
Published: September 2020

This paper presents the results that we attained about modeling and simulation of the metallographic samples preparation and analysis automated systems, made of two subsystems. The first subsystem polishes the samples and assesses the surface state by means of a microscope. In the second subsystem the samples are reagent attacked, washed, dried and analyzed by the electronic microscope. The evaluation of the system performance and the identification of possible bottlenecks was made by means of coloured Petri nets modeling and simulation. The CPN Tools software was used to make the model. Three coloured Petri nets models were developed. The first version assumes the analysis of the system operation by means of coloured Petri nets with simple colours, and such a simple colour was assigned to each entity of the subsystem: samples to be analyzed, robots, storage devices, microscopes etc. For a better observation of the analyzed sample path within the system, the second model version was designed, with complex colours assigned to the marks. The third version considers the time factor. The models with timed coloured Petri nets allow the system performance evaluation considering the number of analyzed samples in a given time interval. This paper presents the first and the third model, as the last one includes the second model.
Experimental study of thermal behavior of heated Natural Composite Materials
Authors: Qasim M S , Fadhel A A , Mohammed H R
Published: September 2020

An experimental investigation was carried out for the thermal behavior of horizontal heated natural composite material plates; (polyester resin mixed with seed dates, or egg shells, or and feathers) with different volume fraction (10%, 20%, and 30%). Natural composite materials are heated with different heat flux (1078W/m2, 928W/m2, 750W/m2, 608W/m2 and 457W/m2). Experimental test rig is used to measure the temperature distribution upper surface of composite materials. Also the thermal properties (thermal conductivity, specific heat, and thermal diffusivity) of natural composite materials are studied. The results show that the maximum value of temperature occurs at the mid- point of the all types of natural composite material plate when the volume fraction equal to 30% and the heat flux equal to 1078 W/m2. Results show that the thermal conductivity for seed dates composite material, the specific heat for feathers composite material and the thermal diffusivity for seed dates composite material are higher value when the volume fraction equal to 30%.
Design and Model of a Prosthesis for Hand
Authors: Radu (Frenţ) C , Roşu M M , Iliescu M
Published: September 2020

This paper presents research results on a prosthesis for human hand, focused on the need to be light weight and user friendly, with relatively low costs and enabling people have almost normal life. The idea to have a customized hand prosthesis, whose dimensios and aspect look as much as possible to that of the real hand pointed to the reverse engineering technique. The authors’ concept of prosthesis for hand is that of three phalanges finger and, mainly, two rotational motions for each of the fingers. Considering the 3D model of the hand prosthesis, with phalanges lengths and joints, there has been done kinematic analysis so that trajectories of fingers were determined and plotted. For the research presentd by this paper, are evidenced the 3D models and stages of rapid prototyping fused deposition models (FDM) of the index finger phalanges. Motion control has been modelled using fuzzy logic. The studied motion is that of getting closer to an object in order to take / grip it. Further development of the research will be focused on: all mechanical components detailed design; complete desgin of the command and control system for the mechatronic parts; prototyping; test and validation of the prosthesis prototype.
Assessment of occupational noise exposure in tyre manufacturing
Authors: Roșca (Ciocan) I , Dascălu L C , Solomon G
Published: September 2020

According to the legislation in force the employer has a responsibility to evaluate and to measure the noise levels to which workers are exposed, paying special attention: level, type and duration of noise. Noise risk assessment is critical to protecting workers from the risks that threaten their health and safety from noise exposure. The noise risk assessment identifies the workers exposed to the risk generated by the noise and determines their level of noise exposure to ensure that the maximum noise exposure limit is not exceeded. When the worker exposure is exceeded, the noise becomes a risk for safety and health, because high noise levels cause hearing loss and this is irreversible. Also, stress from time spent at a high noise level was associated with increased workplace accident rates. This paper presents a technical method for measuring noise exposure in working environment using homogeneous noise exposure groups. The measuring process requires observation and analysis of all noise exposure conditions so that the quality of the measurements can be controlled. The uncertainty of the results is also taken into account. More than half of the workers were investigated during the research (over 900 workers), covering all the production workplaces. The results of the measurements obtained according to this method provided useful informations in order to define the main priorities regarding noise control measures.
Analysis of flow in fluidized bed of particles
Authors: Sabau A
Published: September 2020

The paper presents a study of the flow in a fluidized bed. The analysis is based on measurements made on an experimental stand and computer simulations. Free software packages have been used for simulations. Simulation is done used the most common model for this kind of problem. The first type of model is the Eulerian-Eulerian type and have as their first approximation, the assimilation of the solid phase with a continuous environment. The second category of models is Eulerian-Lagrangean type, they treat the fluid phase as continuous and the solid phase as individual particles or groups of particles “parcels” with similar characteristics. The results of the simulations were compared with the measurements performed on an experimental stand. The experimental stand is composed of a glass column with a diameter of 75mm and a height of 500mm and allows the study of flow in a fluidized bed containing spherical glass beads of 250–500μm in diameter. The results of the simulation were in good agreement whit measured data and in accordance whit the result presented in other specialized studies.
Thrust force evaluation for a ROV (Remont Operating Vehicle) propeller
Authors: Sabau A
Published: September 2020

The underwater vehicles operated remotely, known from the specialized literature under the name of ROV are common and are intensively used in the maritime industry. Depending on the area of use, ROV must satisfy numerous constructive and functional requirements, which are difficult to achieve in practice and the simulation is a challenging alternative. The big challenge is the simulation of the thrust force generated by the propeller. The present work aims to present such a simulation realized with the Ansys Fluid Dynamics software package. The simulation presented uses a 3D model of an asymmetrical propeller in the duct, having as reference the T100 propeller marketed by Blue Robotics. The fluid volume extracted after the model was made was separated into two domains one static and other rotating around the propeller, which was discretized using the default grid generator. The solution was obtained under stationary conditions using only the flow equations together with the standard k-ε model for turbulence modelling. The calculation was made for rotation speed values in the working domain. In the end, using the facilities of the program, the thrust force of the propeller was calculated. The obtained results were compared with the experimental measurements and critical analysis will be done.
Injection moulded composite bipolar plates for a portable hydrogen fuel cell charger
Authors: Serban D , Opran C Gh
Published: September 2020

Fuel cells are electrochemical devices that convert the chemical energy of a reactants directly into electricity and heat with high efficiency. Proton Exchange Membrane or Polymer Electrolyte Membrane (PEM) fuel cells are one of the most common type of fuel cells. In a convection PEM fuel cell, the oxygen from air is introduced to the cathode and hydrogen is introduced to anode. Between the anode and cathode electrodes is sandwiched the polymer electrolyte membrane. The hydrogen molecules break apart into protons and electrons due to the reaction helped by catalysts. The protons travel through the membrane to the cathode and electrons travel to an external circuit. At cathode side the protons, electrons and oxygen molecules combine to form water. Research work was directed to the study of hydrogen fuel cell power systems for portable applications. Last decade the industry developed portable power systems based on hydrogen fuel cell, mobile telephone chargers, vehicles energy supply. In this paper are presented the experiments with a hydrogen fuel cell stack in which were assembled resin filled graphite bipolar plates and then injection moulded polymeric conductive composite bipolar plates and results were compared concluding that injection moulded bipolar plates could represent an attractive alternative in building efficient fuel cell portable power systems.
Computer Simulation of Thermal Processing of Steel
Authors: Smoljan B , Iljkić D , Hajdek K , Sitek W
Published: September 2020

The review of the numerical modelling of casting and welding of steel workpieces was studied. The contemporary industry needs tools to optimize and control parameters of processes by considering the favourite chemical composition of steel. In recent time, very efficient tool for optimizing and controlling of the process parameters is numerical modelling of engineering processes. At casting and welding numerical modelling is focused on optimization of distribution of microstructure contents, mechanical and physical properties distribution and tolerated distortions and residual stresses. Mechanical properties and prevention of distortion and cracking can be accomplished by prediction and control of residual stresses and microstructure distribution. The numerical modelling of thermal processing of metals consists of the research of multi-scale processes and multi-physics processes, such as phase transformations, heat transfer and mechanics of materials, and research of numerical methods for computer interpretation of the problem. By means of the numerical modelling and computer simulation of thermal processing should calculate the transient temperature field, melting and solidification processes, as well as, to calculate distribution of mechanical and physical properties and microstructure composition. In this work, the numerical models of studied thermal processes are based on the finite volume method. Values of surface heat transfer coefficient, heat capacity and heat conductivity coefficient were obtained by the inversion method. The microstructures composition has been predicted by CCT diagrams and additionally improved by the kinetic equations. The mathematical model has accomplished to solve thermal processing of 3-D axially symmetric specimens.
An Analysis of Performance Factors Evaluation of Reusable/Returnable Packaging
Authors: Smoljan B , Hajdek K , Šarkanj B , Bogunović J
Published: September 2020

Development and application of reusable industrial packages, which can be used in assembly line has been investigated. The reusable industrial packages are often called reusable crates and totes or reusable/returnable packaging containers. The trend of development of reusable packaging systems has been facilitated by the plastics industry developing lightweight rugged crates and totes, which can be used in storages and manufacturing lines. Sizes range of these kind packages is from handled totes to pallet-load sized intermediate bulk containers for manufacturing.

Possibility that each component reaches the manufacture at the right time, in the right sequence, and in the appropriate version, referred as Just-In-Sequence was analysed. An automotive supply chain characteristics and scheme of component suppliers’ structure in Just-In-Sequence way was illustrated. Materials properties of reusable packaging was studied. The most important packaging performance factors are durability, flammability, sanitation and ergonomics of packaging, which affect the cost, and operations of a reusable packaging system. Since the importance of industrial reusable packaging is growing up, the new sophisticated test method for transport packages are needed by which vulnerabilities and exposures in the application of reusable industrial containers will be taken into account.
Analysis of piston applications due to fuel burning
Authors: Stan L C , Faităr C
Published: September 2020

The paper aims to analyze the demands of four-stroke naval pistons. To begin with, a brief analysis of the evolution of shipbuilding was made. Mechanical requests are produced by the gas pressure force and inertial force of the alternate moving masses. Under its action, the piston suffers an axial deformation. The thermal demands appearing in the engine are all the more important as the engine power is higher. The possibility of calculating them is more difficult due to the complexity of the thermogazodinamic phenomena in the engine cylinder. Thus, in the piston head, which comes in contact with both the hot gases and the fresh (much cooler) load, a non-stationary heat flow is installed which leads to a certain thermal regime of the engine. Considering the demands outlined in the last chapter, they lead to the conclusion that although the most unfavourable loading situation was considered as the maximum pressure during the processes and even exaggerated in establishing the working conditions, the piston is still close to the elastic limit. This demonstrates that the way of calculating the dimensions of the piston is correct and safe, as long as its constructive dimensions are not oversized.
Physical and mechanical characterization of resonance spruce (Picea Abies L)
Authors: Stanciu M D , Dinulică F , Cîrstea I C
Published: September 2020

The aim of the paper is to presents the experimental results related to physical and mechanical characteristics of resonance wood, one of the most qualitative wood material. Resonance wood, mainly spruce (Picea abies L) is used for musical instruments manufacturing and Romania is well known for resonance wood located in Gurghiu Mountains. Physical features of resonance spruce in terms of colour, ring width, ring regularity, latewood proportion and density were determined on samples provided by musical instruments factory from Reghin. The density profile of resonance spruce samples was determined using the X-Ray Density Profile Analyzer DPX300 and color of samples was obtained by means of chroma meter CR-400 Konica Minolta. Mechanical properties as elasticity modulus, viscous modulus, damping were obtained using dynamic mechanical analysis (DMA).
Influence of thermo-mechanical deformations on the positioning accuracy of CNC machine tools
Authors: Stoica A , Stan Gh
Published: September 2020

This research aims at improving the machining accuracy of the CNC machine tools by decreasing the errors caused by the thermo-mechanical deformations and increasing the positioning accuracy of the mobile element. This work analyses and researches the effects of the thermo-mechanical deformation on the positioning accuracy of the feed kinematical linkages of the CNC machine tools that are using the indirect measuring system of the position. The analysis is focused on feed kinematical linkages having rapid speed rates, of 40 m/min, that use a preloaded bearing system of the ball screw, supported at both ends. Constructive methods are also presented for decreasing the temperature at the heat generating sources by thermo-stating both the ball screw and its bearings. Through thermostats the temperature in the ball screw and its bearings is decreased, that leads to decreasing its influence on the positioning accuracy. The thermo-stating of the ball screw makes possible to keep a constant preloading force of the two ball screw nuts and, as far as the bearings are concerned, the coolant agent is the same as the lubrication agent that leads to a smooth running and, by default, to expanding the life of the feed kinematical linkage.
Method for estimating price procurement of standardized components. Case study – springs
Authors: Tiriplică P G , Rosu M M , Dijmărescu M R , Tarbă I C
Published: September 2020

This paper presents a mode for applying a methodology of estimating the price, presented in previous researches and applied for the price forecasting of springs for light / heavy load. By applying this methodology, the manufacturing companies will succeed in forecasting the procurement price from price offers given to the customers, offers related to similar quotation requests, for products with constructive characteristics comparable or different to the most currently proposed ones. The methodology proposed can be used for the procurement price forecasting for standard components from different equipment from manufacturing process systems. This methodology has as starting point a causal forecast model that is based on the hypothesis that the variable we want to forecast (the product procurement price) is related to another variable which in turn is related to the general environment. The methodology is exemplified by a case study on springs price forecasting. In the spring price estimation process different elements are considered, such as: the shape and the size of the items, the production costs, the profit margin practiced by the manufacturing company, the utility of the item etc.
Hybrid welding of steel 4330V
Authors: Żuk M , Wyględacz B , Stano S
Published: September 2020

The article describes the hybrid welding process (Laser-MAG) of 4330V steel. This steel is a high-strength, micro-alloy material with tempered martensite structure. The microstructure of tempered martensite is obtained through the heat treatment process and through the vanadium micro-additive. Due to the high carbon content (approx. 0.3%), this material causes problems during welding and requires heat treatment before and after welding. The material’s high strength and plastic properties make this material desirable on the market. Hybrid welding is a process of joining materials, where a laser beam is used to achieve deep penetration into the material, and the use of a MAG welding source results in an additional electric arc that supports the melting process of the base metal and the additional material completes the weld. Using a robotic station for hybrid welding, a 11mm thick butt joint was made of 4330V steel without heat treatment processes before and after welding. The joint was welded from two sides. After welding, a number of tests were performed to determine the properties after welding. Visual and penetration testing, macro and microscopic tests, Vickers hardness test, tensile strength test and bending test on both sides were performed. The tests showed a properly made joint with numerous splashes, but unfortunately transverse cracks in the weld were detected which resulted from the stretching of one weld by the other. Macro and microscopic examinations revealed the correct execution of the joint on a full penetration cross-section, the martensitic structure in the heat affected zone and in the weld was visualized. Destructive testing revealed, among others, an increase in hardness in HAZ (Heat affected zone) to a level of about 500HV, high tensile strength at the level of the base metal. The cracks formed on the face mean that the welding process needs to be refined to eliminate such defects.
Technical solution for supplying a solvent of asphalt-resin-paraffin deposits (AFS) to a tubing string of oil wells equipped with electric centrifugal pumps.
Authors: Cheban S.E. , Valeev M.D. , Leontiev S.A. , Mayer A.V. , Samoilov A.R.
Published: September 2020

For prevention and combating paraffin deposites different chemical regents are widely used (ihibitors and AFS solvents). In field conditions many ways of chemical regents dosing are applied. Injection of chemical reagents in oilwell tubing is the most effective for ARPD solvents; in this case consumption of reagents is largely decreasing by comparison with chemical reagents dosing through the well-casing annulus. The article describes design and operating processes of technology of ARPD-solvent dosing in electric centrifugal well pumps installation. This process opens fluid access to oilwell tubing at higher pressure at the wellhead. Reagent RT-1-3, is used as aromatic ARPD solvent. In RT-1-3there is butylbenzene fraction of Kazan Production Association Orgsintez containing a mixture of butylbenzene, isopropylbenzene and polyalkylbenzene.
Centrosymmetric and acentric whitlockite-type phosphates and vanadates among Ca3(VO4)2-Ca3(PO4)2-Y2O3 compositions
Authors: Deyneko D V , Titkov V V , Aksenov S M , Yu Stefanovich S , Lazoryak B I
Published: September 2020

Identifications and studies of whitlockite-type phases for the first time are fulfilled in the cation-anion mixed phosphate-vanadate ferroelectric systems Ca10.5(V1-x
P
x
O4)7, Ca9Y(V1-x
O4)7, Ca10.5-1.5x
Y
x
(VO4)7 and Ca10.5-1.5x
Y
x
(PO4)7. These systems are the sections of a more extensive multi-component system Ca3(VO4)2 - Ca3(PO4)2 - Y2O3, but are all built on the basis of well-known individual compounds of the type of mineral whitlockite. The solid solutions formed between them are also of ferroelectric whitlockite-type, but some compositions are not ferroelectric, and according to the nonlinear optical phase analysis possess centrosymmetric structure. Ferroelectric phase transitions were detected in the region of 1000–1300 K by the method of dielectric spectroscopy. A precision X-ray study of some compositions of solid solutions using synchrotron radiation revealed a significant deviation in the cationic-anionic arrangement from being completely disordered. Partial ordering of structural tetrahedral groups of PO4
3- and VO4
3- determines a significant increase in nonlinear optical activity in the mixed anions whitlockite-type compounds.