bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating Implementation of Electric Power Generation Projects in Iraq
Authors: Nadhum Ameer A. , Erzaij Kadhim R.
Published: September 2020

Iraq has witnessed development in many fields and the electricity production sector is one of the most important of these fields. This is attributed to the State’s philosophy in supporting this sector through the development of economic development projects to serve and raise the level of the Iraqi individual. Electricity production in Iraq is affected by many variables such as load growth, economic and financial conditions, planning, etc. All these led to a disparity in the production of electric power to cover the demand for energy. The paper deals with the electricity generation sector overview in Iraq, Analysis of the effects of variables on the implementation of power generation projects in Iraq, and Creating a mathematical model. The results enable decision-makers to prioritize the implementation of power generation projects in Iraq.
Modeling the Response of Wrap-faced Reinforced Lime Treated Soil Retaining Walls under Static Condition
Authors: Gidday Bisrat Gissila , Mittal Satyendra
Published: September 2020

This paper presents model studies conducted on geotextile wrap faced reinforced soil walls under static conditions in a rectangular model box. Untreated and lime treated clay was used as backfill soils. Numerical modeling has been done by PLAXIS software. The surcharge pressure, angle of the slopes, and different number of reinforcement layers were varied in model tests. The influence of these various parameters at different elevations of the retaining wall, settlement at the crest, and horizontal face displacement are presented in this paper. The tests were conducted at 45° and 60° slopes. It was seen that vertical crest settlement and horizontal displacement of reinforced soil wall decrease with an increase in reinforcing layers.
Mathematical determination of the optimal control and maintenance scheme for industrial processes
Authors: Ashour M A H , Al-Turfi M N , Almaliki S J B
Published: September 2020

Modern industrial projects face many challenges in order to sustain their productivity in a capital effective manner. Operational costs and production lines maintenance policy is on the top factors that play critical roles in that challenge. Linear programming is utilized in this paper to examine the possible minimization of the operational cost and determine an effective optimal maintenance policy for middle-sized furniture manufacturing plant in Baghdad city, taking under consideration all alternatives, non-sensitivity, and solidness. A mixture of Markov decision processes and linear programming analysis is implemented for the actual site and operational data to help decision-makers in planning for their project’s mid and long term maintenance policy and performing Solidness and, as result, the tentative cost reduction scheme.
Neural network analysis for the solidification scheme of the recycled metal casting
Authors: Askar A J , Al-Turfi M N , Ibrahim A J
Published: September 2020

The use of recycled materials as one of the great results for the industrial raw materials shortage may face serious problems during the mold casting process. This paper researches the difference in solidification step between the edges and the center of the aluminum recycled cast. The implementation of such research passes through two verification steps; the removal of the chemical dyes and then to melt the recycled aluminum cans in a ceramic container in order to produce the metallic 60 x 13cm mold. Six thermocouples are inserted on the casting edges and the center and liked directly to a computer system in order to simultaneously record the temperature readings from the start of the cooling/solidification process. The Artificial Neural Network ANN approach is applied to the recorded data via the utilization of the software MATLAB in order to analyze the cooling curves and determine the mathematical representation of the solidification layers through the casting. The interior layers microstructure is examined via SPECTROPORT mobile metal analyzer so as to detect the solidification trend through the examined ingots. The edges of the casting are shown to solidify more quickly than the central region and also it is demonstrated via the microstructural samples that the boundaries are more clear in the center than these at the edges.
Aspects on the use of GNSS technology in maritime and fluvial navigation
Authors: Bădescu G , Călina A , Călina J , Săvescu P , Miluț M , Băbucă N I
Published: September 2020

It presents the use of global navigation technology, NAVSTAR-GPS and GLONASS systems in maritime navigation and some aspects that are encountered in maritime navigation, using these systems. The use of GNSS technology in maritime navigation is beneficial and at the same time it can be used in the civil domain, the system which is eminently civil, being the Galileo European positioning system. Commercial vessels sailing on the seas and on the planetary oceans can be monitored and managed in real time, if the GNSS-type global positioning systems are used. The global positioning systems of the GNSS type include all the positioning systems, but especially those of the NAVSTAR-GPS, GLONASS, GALILELO, BEIDOU type. The advantages of using in the navigation of global positioning systems is unmatched and it makes sailing much more useful and safer on the seas and oceans of the earth. River navigation is a component of trade and water transport, which can be managed using modern means of navigation by satellite type GNSS, Romania participating with neighboring countries in different European programs. There is a brief introduction of the notion of global positioning system to the general mode and a specific appreciation of each global positioning system in part and to the general mode of GNSS global positioning systems. Important aspects are presented in the use of GNSS technology, in the maritime and related fields, the advantages of this technology in relation to the classical technologies and the judicious cooperation in the extreme cases between the two technologies. The sources of positioning errors in the use of global GNSS positioning systems and the methods by which they can be eliminated or reduced are presented. It presents the calculation of the navigation coordinates in different projection systems and the stages of transformation of the coordinates in the WGS-84 system, specific to the Navstar-GPS positioning system in different coordinate and projection systems. Maritime navigation is guided by specific methods, but lately, global positioning systems are a beneficial presence in the steering and navigation component of the world’s seas and oceans. Finally, conclusions and proposals regarding the judicious and beneficial use of the GNSS positioning system in navigation are presented.
Classic or fully automated technology lines?
Authors: Barbu I , Fogorasi M S , Nicolaescu C , Bucevschi A
Published: September 2020

In this paper we compared a classic technological lines and a fully automated line for the manufacturing of 100% cotton yarns. For this comparison we analyzed the complexity of classical and fully automated technological lines, the differences between the yarn structures, aspects related to the quality of textile yarns but also an analysis of production costs and benefits. The spinning mill is the first sector in the textile field, the sector in which the textile yarns are made. The quality of textile products, fabrics, knits, garments or technical articles are strictly dependent of the quality of textile yarns. The yarns are made of short fibres of cotton, wool, linen, hemp or other raw materials, with a great unevenness of the physical-mechanical characteristics, and the technological engineer must make a series of adjustments, settings of the machines so that the yarns made have a lower unevenness. This is the reason why the technological engineer must set the technological process so that the yarns are of adequate quality, have low production costs and deliver orders to the beneficiaries within the terms established by the commercial contracts concluded with them. In order to decrease the production costs, there were permanent concerns for the introduction of new automation elements, so that in the field of cotton spinning reached an extremely high level, right at the fully automated cotton spinning mill. Practical, on the technological line there are only two operators, one that supplies the technological line and one that transfers pallets with bobbins from the palletizing robot to the transport means. Practically the technological lines are composed of the same machines, but the automation elements on each machine and the aggregation systems between machines allow the almost complete elimination of the operators for service of machines. Given the complexity of the technological lines and the difference between the human resources for the two technological lines, in the first step we made a comparative calculation of the costs for the salaries of the operators and the taxes that an employer must pay. Then we made a comparative calculation of energy consumption. The comparative analysis was done for a cotton spinning mill with a production of 4000 t/year, classical yarn, 100% cotton yarn, with average fineness Nm40, made on ring spinning machines. Finally, we made a comparative study of the investment effort and the amortization of the investments made, amortizations which is reflected in the total costs and then in the delivery price of the yarns to the beneficiaries.
Numerical and Experimental Investigation on the Free-surface Flow and Total Resistance of the DTMB Surface Combatant
Authors: Bekhit A , Obreja D
Published: September 2020

Starting with the initial design stage, the ship resistance constitutes one of the most important hydrodynamic aspects. In order to generate and optimize the body lines plan, the ship resistance performance must be considered. In this case, both numerical and experimental methods must be applied to obtain the minimum ship resistance controlled by the speed domain. In the last years, numerical studies based on the Computational Fluid Dynamic (CFD) were implemented in the initial ship design stage in order to analyse the free-surface flow and to predict the ship resistance. The numerical optimization process of the hull forms must be validated by means of the experimental model tests in the specific towing tanks. The constant evolution of the numerical and experimental methodologies can be noted. As a consequence, the accuracy level of the ship resistance prediction is increased; though, difficult numerical problems can occur in case of the unconventional hull forms. Taking into account this aspect, a complex numerical and experimental investigation of the ship resistance problem and free-surface topology was performed in the case of the DTMB surface combatant. A parallel numerical simulation was carried out by using the viscous flow solver ISIS–CFD of the software FINETM/Marine provided by NUMECA. The solver is based on the finite volume method to build the spatial discretization of the transport equation to resolve the Reynolds-Averaged Navier Stokes (RANS) equation. Closure to turbulence is achieved by making use of the k-ω SST model, while the free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. For the validation purpose, the tank conditions are reintroduced in the numerical model to account for any banking effect, especially for the high speed cases. Experimental model tests were performed in accordance with the ITTC standard procedures, while the extrapolation process to the full-scale was obtained by using an in-house code, based on the ITTC 57 method. The experimental results are compared through with some internationally recognized towing tank experiments that have been performed for a similar ship model, showing a good agreement. Also, the numerical results are validated against the experimental data and showed to be within a satisfactory congruence.
Interface for Data Protection and Integrity in IoT Equipment for Industry
Authors: Belu N. , Ionescu L.M. , Mazare A.G.
Published: September 2020

Presently, industrial processes are increasingly based on the equipment that communicates with each other. IoT is present in all branches of the manufacturing process, from the flows of the equipment that work together to achieve the finished product, to the equipment for checking the quality of the process, to the existing logistics infrastructure inside the factory, to the coordination and administration side. One of the problems raised by using IoT is that related to data security and integrity. We are talking about data protection for unauthorized access: maintaining confidentiality at the level of the different departments in the production flow, protecting the data provided by equipment and preventing the injection of unauthorized data flows and we are talking about ensuring data integrity: the data from the equipment must be resistant to any disturbances that occur in the industrial environment on the communication channels (wireless or wired), be assured the correctness of the transmission of the commands from the operator to the equipment. The paper proposes a specialized IoT interface that ensures the protection and integrity of the data transmitted between endpoints. The protection is provided by a light encryption algorithm based on two keys stored at the source and the recipient and on a very simple but efficient coding / decoding scheme. Data integrity is ensured by an 8-bit code word algorithm that allows for the detection of 2 wrong bits and the correction of a wrong bit for a 4-bit packet. All these features are provided by a computer system integrated in the IoT equipment. The efficiency of the solution is illustrated by a case study where in the manufacturing process of pistons it was desired to introduce specific elements Industry 4.0: communication between equipment in order to detect problems in the flow of manufacture (a Poka Yoke system). On the one hand, the system is presented without the protection solution in which there are several communication errors due to the disturbances induced on the communication channels on the other side to the system, the interface proposed in this article is added (at minimum cost) and the performances will be presented in the communication introduced by it.
Horizontal-Axis Wind Turbine Blades Manufacture with Composite Materials
Authors: Bucur I O , Malael I , Breban S
Published: September 2020

The aim of this paper is to contribute to the wind turbine manufacturing industry through investigating the technological manufacturing process of a 2.5kW horizontal axis wind turbine’s (HAWT) blades. Composite materials, such as fiberglass and carbon fiber are engaged in the manufacturing process, due to their mechanical properties. The material selection process is discussed, motivating the choices based on several criteria, such as weight and tensile strength. The adopted technologies for the manufacturing process include layup method at ambient temperature and vacuum. Regarding the used moulds, these were previously manufactured using the infrastructure that NRDI COMOTI has at its disposal. Layups of fiberglass and carbon fiber are disposed in the aluminium alloy moulds. In the end, a layup of peel ply is placed upon the outer surface of the composite and the vacuum bag is applied and sealed. The outcome of this research consists of two parts. Firstly, the presented methodology, techniques and materials selection criteria represent a reliable source of information for future scientific papers on the matter. Secondly, the manufactured blades, after post-processing techniques, can be tested in relevant conditions in the aerodynamic tunnel and further studies can be conducted with the obtained results.
An efficient strategy for 3D numerical simulation of friction stir welding process of pure copper plates
Authors: Constantin M A , Iordache M D , Nitu E L , Diakhaté M , Demmouche Y , Dhondt M , Bădulescu C
Published: September 2020

Copper and its alloys have a wide spectrum of engineering applications such as heat exchangers, hot water tanks or nuclear pressure vessels. Most of these structures are obtained by welding. Unfortunately, the use of conventional arc welding process is affected by several factors such as the thermal conductivity of the alloy being welded, the shielding gas, the joint design, the welding position, and the surface condition and its cleanliness. Friction stir welding process could be an interesting alternative as it can be performed without melting the material, it involves a non-consumable tool, and provides good mechanical properties. To understand in depth both the physical and the thermal mechanisms involved in this process, numerical modelling is essential. The aim of this paper is to propose an efficient simulation strategy based on the coupled Eulerian Lagrangian finite element method. The mass scaling procedure, which is used to decrease the computation time will be presented, as well as its effect on the temperature field distribution and on the down force. This model will then be used for a parametric study in order to improve the friction welding process’s parameters.
Determination of the theoretical deviations at the tooth bottom processing with Vortex threading device
Authors: Cretu G
Published: September 2020

The paper presents the calculation method of the theoretical deviations resulting in the processing of worms screws profiles bottoms using the Vortex threading method. Because the deviation of this size depends on several factors, a program has been developed in order to analyze its size according to the screw constructive parameters but also to the threading device’s constructive characteristics. Also, the working regime used was taken into account. Base on these, the conclusions were drawn regarding these theoretical deviations size and of their influence on the manufacturing process.
Design and Development of a Software for the Estimation of the Vickers Hardness Measurement Uncertainty
Authors: Dijmarescu MC , Dijmărescu MR
Published: September 2020

Measurement uncertainty is a common concept. This concept gives us a certain degree of confidence in the results obtained from a specific measurement. However, its estimation is a very complex process, requiring knowledge of mathematics, but also a thorough knowledge of the method by which a certain type of measurement is performed. The uncertainty of the measurement result reflects the lack of knowledge of the measurand value. The result of a measurement after correction for recognized systematic effects is still only an estimated value of the measurand because of the uncertainty arising from random effects and from imperfect correction of the result for systematic effects. Scientists have created and developed tools to optimize their work in order to reduce the time wasted by making the mathematical calculations necessary to estimate uncertainty of measurement, regardless of the type of measurement. This paper aims to present the design and development of a software used to determine the Vickers hardness measurement uncertainty based on the mathematical model presented in the ISO 6507 standard. For the development of the software, a special program based on the C ++ programming language, program that allows graphical modelling of the interface, will be used.
Approximation method of the speed-torque mechanical characteristics using the spline interpolation of various electrical motors
Authors: Dordescu M , Nicolescu F , Oanta E
Published: September 2020

The design of the electric drives of the on-board installation requires motors of an adequate power. The dimensioning of the electric drive takes into account the mechanical loads and it provides the value of the torque which loads the electrical motor shaft. The selection of the appropriate electrical motors is based on the speed-torque mechanical characteristics, n = u(M), where n is the angular speed in rpm and M is the load torque in N · m · Drawing the n = u(M) characteristic, one can notice that the function is not injective, therefore we employ its ‘rotated’ version, i.e. the M = f(n) function. In this way we are able to mathematically define the … f function, and further on to deduce its approximation using the spline functions. As a case study we use an asynchronous motor for which the calculus is based on the Freidzon method that uses relative values. The spline approximation uses an original data processor which outputs various types of information in a wide range of text, image and computer code formats. Using the experimentally acquired data as input information in the spline based processor we have a more accurate approximation of the speed-torque mechanical characteristics. The previously mentioned methods are useful for the rapidly evaluation of the mechanical characteristics of the motors, that is an important criterion in the marine engineering decision making process.
Optimizing the energy efficiency of vessels using recovery boilers
Authors: Faităr C , Nedelcu A , Buzbuchi N , Stan L , Dumitrache C
Published: September 2020

In general, the energy requirement on board the ship is divided into three categories: propulsion power, auxiliary electric power and auxiliary thermal power. The WHRS system uses the energy dissipated from the exhaust gases, but also it can be used the energy from the main engine cooling water system (high temperature freshwater cooling circuit) and the air system by applying a WHR heat exchanger element to the main engine. The application of CFD in the analysis of heat exchangers is somewhat limited, being able to be used in the initial dimensioning thus reducing the number of prototypes and offering a clear image of the phenomena of heat transport from the equipment. In the economizer the water supply will turn into steam, so the problem to be solved is the two-phase flow with two different properties and the phase transformation of water from liquid to steam. These two phases are mixed in the economizer tubes at the macroscopic level. The two phases can coexist in dispersed form, droplets or steam bubbles. In the fluid field can coexist phases with different densities or different speeds.
A detailed micro-modelling approach for the diagonal compression test of strengthened stone masonry walls
Authors: Ghiga DA , Țăranu N , Ungureanu D , Isopescu DN , Oprișan G , Hudișteanu I
Published: September 2020

The aim to retrofit and preserve the monumental stone masonry buildings due to their historical and cultural relevance is accompanied by the necessity of understanding the behaviour of the unstrengthen structure, as well as its behaviour after the strengthening systems are applied. There is scarce information related to the mechanical properties of stone masonry buildings and even less regarding the assessment of these characteristics in numerical models. Therefore, simulating the force displacement variation and the stress-strain distribution of stone masonry loaded in diagonal compression is a challenging issue. This work contributes to this topic by developing two detailed micro non-linear 3D models. The first model was designed for an unreinforced masonry (URM) wall and the second one was developed for a strengthened URM wall. For this purpose, a commonly used seismic strengthening system, referred to as reinforced plastering mortar (RPM) or textile reinforced mortar (TRM) was applied on the wall. All the components of the TRM strengthening system and the interfaces between the system and the stone masonry wall were considered in the numerical model. The structural responses of the models were analysed and compared and the TRM system effectiveness in increasing the in-plane load resistance and ductility of stone masonry walls was highlighted.
Influence of resistance butt welding thermal cycle on structure and properties of termomechanically rolled steel
Authors: Górka J , Jamrozik W , Wyględacz B
Published: September 2020

In this article examination of structure and properties of resistance butt welded joints from S700MC high strength steel. 10 mm thick including recording welding thermal cycle recording are presented. The thermal cycle acquisition was performed on purpose build rig with a thermographic camera and a computer. The thermal fields acquisition station consisted of Varocam Head HR thermal camera and computer with Ibris 3 plus software, which enabled control of thermal camera parameters and saving of acquired on a local storage media. Aside from environmental parameters, such as temperature and humidity of surrounding, transmissivity of atmosphere equal to 1 and mean emissivity of steel surface of 0.9 were set. Noticeable impact of welding thermal cycle on strength and plastic properties was observed.
The analysis of high-pressure water jet cutting of thick aluminium alloy 6061-T651 from a statistical perspective
Authors: Grigoraș C C , Chiriță B , Brabie G , Zichil V , Herghelegiu E , Tâmpu C , Ciofu C , Iancu C
Published: September 2020

The main context in which abrasive water cutting is used is the reduction of thermal deformation induced by thermal (plasma arc PAC, oxyfuel OFC, laser) of electrothermal (electroerosion EDM) cutting methods. Although it is not the cheapest or time-efficient technique it can be used on a wide variety of metallic and non-metallic materials. Among other benefits are the lack of burrs, high precision and improved surface finish, low setup time and stress-free cutting. This leads to no secondary processing required in many other applications. Depending on the material hardness the cutting thickness can reach up to 300 [mm]. The present study proposes an analysis of high-pressure abrasive water jet cutting of a 19 [mm] thick plate. The aluminium alloy used in this study was Al-6061-T651. This alloy is being used especially in the aeronautics industry due to is excellent welding properties. The experiments were conducted using multiple input and output factors. The design of experiments (DOE) takes into account input factors and offers models for responses. The study was organised according to response surface methodology, with an I-optimal design type and a quadratic design model. The input factors were: cutting pressure, standoff distance, programmed quality of the cut. The responses analysed were: entrance (Iw) and exit (Ow) width of cut, and taper angle (α). An ANOVA analysis was performed for each response. This interpretation implies the significance (p-value) that the input factors have on the variation of the responses. For Iw and Ow a reduced 2FI model was proposed, while for θ a linear model was suggested. The p-value obtained for each response is smaller than 0.0001, which classifies the models as significant. The ANOVA fit statistics determine the R-squared error between 0.964 and 0.995, meaning that the responses are well defined by the input value variations. This high confidence in the results leads to accurate mathematical models.
Design of reinforced composite material to overcome wear occurrence in transportation pipes
Authors: Ibrahim A J , Salih A L M , Al-Maliki S J B , Al-Baali G
Published: September 2020

The wear of carbon steel piping systems has been one of the major problems for various industries that involve the high-speed transportation of their raw materials and/or products. Transportation of cement in construction materials manufacturing factories through carbon steel pipes was studied to suggest a resistible material of unsaturated polyester reinforced with glass fiber and the aluminum honeycomb to be used instead of these pipes. A laboratory-scale apparatus was built to examine the wearing in pipes for the carbon steel and composites specimens. The electrical and mechanical prosperities of the composites were studied by using the ASTM standards to find the best conditions for the newly constructed pipes. It was found that, by increasing the concentration of aluminum powder up to 50 wt% of the composite mixture, the electrical conductivity was increased to be within the range of semi-conductance but the mechanical properties decreased. The best concentration of aluminum powder was found to be 30 wt% of the composite mixture, which represents the most suitable electrical and mechanical properties. Also, it was found that the samples of aluminum honeycomb were gained very good electrical conductivity with special mechanical properties that are suitable for many practical applications.
Lean Manufacturing 4.0 - dynamic physical and cybernetic system for Industry 4.0
Authors: Ionel D-S , Opran C Gh , Vălimareanu B C
Published: September 2020

The intelligent manufacturing system is realized through fusion between the production system with information and communication technologies. This allows to build a digital twin of physical production system, the two being connected and communicate each other data in real time about production status and progress. The existing Industry 4.0 physical system identify the active production resources, who are directly involved in the production processes, and of the passive ones, who have supporting roles. In Industry 4.0 those resources are directly interconnected with the corresponding cyber elements in order to supervise the whole system and the corresponding processes. Into this architecture, the physical production passive and active resources will form a dynamic subsystem, through which one can manage the physical and cybernetic changeable manufacturing processes and various products, in different manufacturing stages. This paper presents a solution to change the cyber-physical system by replacing the production physical active elements with those elements who need to change on the production line and the corresponding digital resources, including the specific Lean 4.0 production system tools who supervises the manufacturing cell and controls the execution. This dynamic system allows achieving a higher level of the production system.
Optimal management of production processes using the function of losses in the production processes
Authors: Kirov K , Avramova T
Published: September 2020

In today’s modern world the manufacturing processes are designed in such a way as to ensure the desired quality of the end product. In this article are considered some aspects of desired quality in performance. The described quality management tools are based on Taguchi’s theory Quality Engineering and Robust Engineering. In relation to this in the paper are presented a new application for assessing the losses of society from the irrational use of resources or their harmful impact in the transformation into a production process, the possibilities of Taguchi’s theory in assessing the losses of the stakeholders in the functioning of the enterprise - in case of ineffective or inefficient use of the production process and proposal of the possibility for a complex assessment of the losses of the society and the stakeholders from the production of products and operation of production processes at quality indicators different from the desired nominal values
Experimental study on catamaran hydrodynamics
Authors: Mandru A , Pacuraru F
Published: September 2020

In the last decade, the main concerns of the maritime industry are the reduction of fuel and carbon emissions. IMO (International Maritime Organization) has introduced relevant conventions and improvements in fuel economy standards for ships. Thus, different research projects have been developed to improve the energy efficiency of ships, reducing fuel consumption and carbon dioxide emissions. The flow around the catamarans is a complex hydrodynamic phenomenon due to the interference effects that occur on the free surface between the bodies of the catamaran. The flow around the ship hull has a wide variety of physical fenomena, many of which are relevant for the study of resistance. The two important aspects of the interference effects associated with the catamarans with direct influence on the hydrodynamic performances are: the viscous interference due to the asymmetric flow around the bodies with direct effect on the development of the boundary layer and the wave interference generated at the free surface from the interactions between the wave systems generated by each hull.

First set of towing tank tests have been performed to evaluate the ship resistance of the catamaran hull, interference between wave system of the hulls and to analyse the hydrodynamic parameters of the flow. To evaluate the effect of the central bulb positioned between the hull bodies on the ship resistance, six different sets of experiments were carried out for seven speeds corresponding to Froude numbers between 0.20 and 0.80. Six different configurations of the bulb considering three different depth and two position along the hull (bow and stern) have been considered. The calculations revealed that residual resistance can be reduced by using a central bulb between the catamaran hulls by up to 10%. This happens when the bulb is positioned at the bow and the stern and for Froude numbers 0.4-0.6.
Modelling of maritime ship repairs processes in shipyards, using the linear regression and correlation theory
Authors: Manea M G , Zăgan R , Manea E
Published: September 2020

The tendering and programming-planning activities carried out in the shipyards for the execution of the repair works of the maritime vessels are the result of estimates that operate with fixed data, conditioned by variables belonging to a wide spectrum of conditions and limitations. In the documentation made for the elaboration of the present work and the resolution of the chosen research topic, the studies were directed to the fundamental theoretical fields of: probabilities and statistics; modelling and numerical simulations. The objective assumed by the authors was to find a well-founded method for estimating the retention period of the ship in the shipyard, to exploit the information held in the portfolio of repair works performed to various clients, over time. This gives the perspective of optimizing the decisions of the shipyard management with reference to the problem of anticipating and programming the duration of the repair works of the maritime vessels. The purpose of the research consists in proposing an analytical function for analyzing the linear dependence of the time period, as a dependent variable, on the works carried out in the shipyard, considered as independent variables. The role and importance of the technical specification of the works prepared by the owner / technical manager of the ship, from the perspective of the management of the repair works of the maritime vessels in a repair yard, are highlighted, as well as the importance of the selection of variables with significant influence in the forecast of the duration of the repair works of the maritime vessels in a shipyard.
Micro gas turbine combustion chamber CFD modelling
Authors: Mangra A C
Published: September 2020

The interest in micro gas turbines has been steadily increasing. As a result, the researchers’ attention has been focused on obtaining optimal configurations for micro gas turbines depending on the applications in which they are used. Micro gas turbines are suitable for both civil and military applications. Presently, they are often used in the development of Unmanned Air Vehicles (UAVs). Micro gas turbines have the following advantages: a wider range of options regarding the used fuel and a significant system weight reduction. This paper presents the CFD modelling results regarding an annular type combustion chamber. This combustion chamber is part of a 80 daN micro gas turbine, destined to equip a small scale multifunctional airplane. The combustion chamber is equipped with eight pressure-swirl injectors, using Jet-A as fuel. A 3D RANS numerical integration of the Navier-Stokes equations has been carried out, using an Eddy Dissipation combustion Model (EDM) and the k-ε turbulence model, implemented in a numerical simulation conducted using the commercial software ANSYS CFX. An unstructured computational grid, generated using ICEM CFD, has been used. The fuel is injected directly in the fire tube in the form of droplets. The initial fuel droplet’s diameter has been considered to be 50µm and the fuel spraying cone angle has been set at 90°. The fuel droplet break-up and evaporation processes have been simulated using numerical models available in ANSYS CFX library. A two steps reaction mechanism, which takes into consideration the formation of NO, has been used. The results thus obtained are encouraging. The flame developed in the central area of the fire tube, its walls thus not being subjected to high temperatures. Also, the maximum temperatures were obtained in the primary zone of the fire tube. The temperature then decreased in the fire tube’s secondary zone and dilution zone, until it reached an average value of 1200 K at the combustion chamber exit. Regarding the pressure, based on the numerical simulation results, a 5% pressure loss has been obtained. The numerical results will be validated by conducting combustion tests on a testing rig which will be developed inside the institute’s Combustion Chamber Laboratory.
Dynamic modelling of overhead crane
Authors: Muscă (Anghelache) G. D. , Năstac S.
Published: September 2020

This paperwork deals with dynamics of overhead crane. Dynamically speaking, I considered the overhead crane beams as continuous medium with distributed elasticity and weight, simple supported at ends, stressed by distributed as well as focused forces. The distributed forces are the own weight and forces of inertia (mass forces) and focused forces are those produced by the carriage and transported load. Focused forces may travel along the overhead crane, so they have variable position and are, in their turn, variable in time as the carriage, always considered in contact with overhead crane, is, on one hand subject to the same accelerations as the beams oscillate in vertical plane in the place where the carriage is at the said moment, and produce variable inertia forces, and, on the other hand, a load is hanging on it, sustained by elastic cables, pulling down with a variable force, depending on how oscillations of the load and overhead crane beam mix up together. The overhead crane is a beam with variable profile subject to static and dynamic, focused and distributed loads. This makes the mathematic model of the overhead crane dynamics to be very complicated and the presentation that follows shall prove it. Analysing the results presented in this study it may come to the conclusion that monitoring and analyse of overhead crane dynamics is extremely important because it may highlight the potentially dangerous situations in operation of this equipment.
A Thermal Analysis in Solidworks for the MQL Systems of the Metal Cutting Processes
Authors: Olaru I , Olaru C
Published: September 2020

Through the cutting operations of the different metallic materials, large cutting forces are developed, they depend on the material to be processed and on the cutting parameters. During the cutting operation, due to the friction between the tool and the material to be processed, an important amount of heat is released. As the friction between the elements is higher, the heat generated by the attachment can disturb the cutting process. If the temperature from the cutting process is higher than a certain value, the resulting surfaces may have a number of processing defects. In order to reduce the temperature value of the cutting process, different cooling systems have been developed over time that use a wide range of cooling liquids. Cooling liquids have a number of advantages and disadvantages, after the cutting process they have to be discharged and their negative influence on the environment to be minimal. Recent studies have attempted to reduce this amount of coolant by streamlining fluid flows. Systems that use minimal amount of lubricant or coolant are MQL (Minimum Quantity Lubrication) type. These systems have special nozzles so as to obtain the best possible distribution of the coolant in the cutting area, as well as a good mixing if different cooling liquids are used. This paper aims to study the cooling systems for the cutting processes, forms of nozzles to send the fluid in the working area, thereby thermal analysis, from the desire to use an efficient MQL system.
Indoor air quality monitoring universal device
Authors: Panaitescu M , Dumitrescu M V , Panaitescu F V
Published: September 2020

This paper presents a solution for indoor air quality monitoring universal device. Existing devices on the market analyze a small number of indoor air quality parameters, require expensive consumables and periodic maintenance services. Our solution has a small volume, portable, easy to use, low price, almost non-existent maintenance, possibility monitoring a wide range of compounds and harmful elements of air. The proposed device can be equipped with a wide variety of sensors: gas sensor, digital gas sensor for air quality breakout, combined temperature and barometric pressure sensor, a 3 sensor device suitable for gas leak detection air quality monitoring. The results obtained with this device are: the individual values for each monitored element, local and online visualization of the data, the alarms for exceeding values, online access to data for analysis and processing. Finally, the solution proposed by us is cheap, we can work continuously, with the mention that if defects occur they can be remedied quickly by replacing the parts with replacement ones, without requiring periods of interruptions in the monitoring process.
An innovative class of aluminum alloys for automotive industry: investigation on their corrosion resistance
Authors: Peter I , Castella C , Molina R
Published: September 2020

Self-hardening aluminum alloys (AlZn10Si8Mg, EN-AC-71100) represent an interesting innovative class of material for the production of automotive and aerospace components with high-mechanical strength and good corrosion resistance. The aim of the present is related to the investigation of the intergranular corrosion resistance of an innovative class of self hardening alloys. Microstructural characterization combined with compositional analysis has been carried out by Optical and Scanning Electron Microscope equipped with Energy X-rays Dispersive Spectroscopy unit. Three-point bending test and Charpy Impact test have been performed and the corrosion resistance of the alloys has been investigated according to standard BS 11846, method B. The susceptibility of the alloy to intergranular corrosion has been assessed evaluating the maximum corrosion depth and the weight loss of the alloy after corrosion test. The results obtained have been demonstrated that the corrosion resistance of the alloy can be achieved by Mg addition.
Liquid Wood Rheology
Authors: Petrescu T C , Bărhălescu M L , Ibănescu C , Danu M , Văideanu D , Costescu E Puiu
Published: September 2020

“Liquid wood” is a biopolymer composite exhibiting a lignin matrix. Lignin is separated as a by-product of paper. Following research by German scientists from a production company, an invention was made that determines a new use of lignin, the capitalization of said product in this case being superior. This material combines lignin with other natural substances: resins, waxes, vegetable fibres etc. It results a polymer that exhibits certain physic-chemical properties which recommend it for large scale use, being able to substitute plastic materials. Some of the properties of “liquid wood” are: it is a thermo-injectable polymer, it is obtained from renewable resources and it is biodegradable. Existing injection or extruding machines, used for synthetic polymers such as polyethylene and polypropylene, can be employed to obtain various “liquid wood” parts. It has been observed that injection process parameters influence mechanical and physic – chemical properties of products obtained from “liquid wood”. In order to find the optimal injection parameters for an object that exhibits certain mechanical and physic – chemical properties, it is necessary to determine the rheological properties of “liquid wood”. In this paper, several “liquid wood” rheological properties have been determined, in order to assist the optimization of the injection process.
Numerical Analysis of the Thermal Performance in Traditional and Developed Shapes of Thermosyphon
Authors: Qasim M S , Freegah B , Ali G S
Published: September 2020

In recent years, the research in renewable energy is remarkably increased to reduce the reliance on fossil fuels. Solar energy took the lead among the other sources of renewable energy due to its availability everywhere and the feasibility of its use for various circumstances. Thermosyphon is one of the most successful systems for solar energy conversion. In the present study, a CFD code is employed to analyze the natural convection phenomenon which is inherent in the performance of a thermosyphon system. A steal pipe of 25 mm internal diameter and 1250 mm length is considered as the condenser of the thermosyphon. Water jacket is used to cool the condenser with an internal diameter that is five times that of the condenser. Two types of pipes are considered in the present study, namely; straight and helical pipes. The case of helical pipe assumes five different numbers to turns, which are; 10, 20, 30, 40 and 45 turns. A solar heat flux of 500 W/m2 and above is used in the analysis. The results obtained from the numerical analysis showed that the helical pipe is more efficient than the straight pipe in heating the water inside the condenser jacket for the same operating conditions. The ratios of increase in jacket water temperature of the five cases of the helical pipe to that of the straight pipe were 23.8%, 36.5%, 42.1%, 45.3% and 46.2%, respectively.
An Analysis on some thermal characteristics of AlMg10-SiC ultralight composite materials
Authors: Rusu O , Rusu I
Published: September 2020

The paper presents the determination of the specific heat, thermal conductivity and thermal expansion coefficients of some composites of the type AlMg10-SiC with the help of a differential scanning calorimeter. For the experiment we will use several types of composites with different concentrations of SiC (5%, 10%, 15%, with 120 micrometres medium size).One sample category was obtained by melt bubbling method (A) and the other one by soluble salt method (B). We obtained cellular composites using A method and porous composites using B method. The paper presents by comparison the thermal properties of the two categories of materials. The paper also presents the equipment used, as well as its operation. We used a differential scanning calorimeter for the specific heat and thermal conductivity determinations and thermomechanical analyser equipment for linear expansion coefficients. Based on the values obtained for the thermal characteristics of the investigated composite materials, those directions of applications can be suggested, which can be based on the absorption characteristics of the deformation energy of these composites, even at temperatures above 100°C, a situation for which, for example, in general, polymeric composites cannot be used.