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This issue of the RECENT journal was edited with the support of: CONTENTS
Software Application for Documents Management in Higher Educationhttps://doi.org/10.31926/RECENT.2019.59.094 Abstract Study program management is a very time-consuming process, especially due to large number of documents to be made. On the market, Romanian or international, there is no commercial software that may help. Software application developed by the authors is designed to automatically generate documents required in quality evaluation of the university study programs (with direct application for distance learning study programs) based on curricula. Using this software, half of the documents are generated 40% faster than are generated before. In addition, a great advantage of it would be the opportunity of using it on an eLearning platform. Keywords software, informatics application, higher education, documents management
An Approach on a Transient Regime of a CNC Machining Center Spindle Drive System Using the Active Electrical Power Evolutionhttps://doi.org/10.31926/RECENT.2019.59.099 Abstract This paper proves in theoretical and experimental terms the availability for scientific research of the active electrical power absorbed by a CNC machining centers during a transient regime of the spindle motor (start/stop on 10,000 rpm) electrically supplied by an AC/AC converter. A simple computer assisted experimental setup (with transformers placed on the electrical supply system of the converter, signals acquire system) and processing procedures are used in order to produce a correct approach of spindle motor and converter behaviour concluded in condition monitoring and diagnosis. Some relevant results were obtained in description of active electrical power (energy) absorption during acceleration and negative power absorbed during deceleration by electrical braking, in the description of instantaneous power constituents (voltage and current) and evolution in frequency domain by fast Fourier transform. An experimental approach on energy conversion efficiency (converter input electrical energy into output mechanical energy of spindle motor) was done. As an interesting topic for future, these research achievements are available in the research of mechanical loading (torque) during cutting processes (cutting tool and process condition monitoring). Keywords CNC machining center, spindle motor, transient regime, active electrical power, monitoring
Properties of Resinous Wood Species Used in OSB Technologyhttps://doi.org/10.31926/RECENT.2019.59.107 Abstract The paper aims to discover the characteristics of softwood species used in the technology of oriented strand board. In this sense, the main physical-mechanical properties of three wood species (fir, spruce, and pine) were determined and obtained, based on the European standards. The physical properties of the solid wood will be compared with the characteristics of the oriented strand boards obtained from each resinous wood species, in a future work. From the analysis of wood properties, it was found that the softwood species are the best corresponding specie to this technology, because they have soft and light wood (due to their low density), and their higher mechanical strength will give very good mechanical strength of the boards. As a final conclusion of this work, it can be stated that the softwood species remain the basic species of the technology for the manufacture of oriented wood strand boards, due to their low density (thus good compressibility and compactness) and superior mechanical properties. Keywords OSB, wood specie, MOR, MOE, IB
Study of the Influence of Chemical Treatment on the Performances of the Mechanical Properties of the Naturel Fibre of Agave Americana Marginatahttps://doi.org/10.31926/RECENT.2019.59.113 Abstract Today the use of plant fibers in industrial fields and especially in composite materials appears as a good alternative and it has become widespread due to the interest of these fibers and their physical, biological and economic properties. So for that, composites or bio-composites are fairly developed materials and well involved in the industry. Our research has focused on the characterization of new fibers behavior and understanding their mechanical behavior regarding chemicals treatments to build better bio-composites. In this context, we are studying the fibers of Agave Americana Marginata, which is a widespread plant in Algeria with yellow and green leaves up to a length of two meters but it is not yet exploited. The first step that has been made is the extraction of the fibers by a simple ecological method is to immerse the cut leaves in a barrel of water closed at a temperature of about 30° for 25 days so that we can extract and treat these fibers with three chemicals: NaOH, KMnO4 and Na2CO3. In each product nine bundles of fibers are considered as samples, each bundle contains 50 fibers for tensile tests. These sheaves are treated at room temperature with different durations and for several concentrations. After the treatments, a microscope observed these fibers and the results show the perfect elimination of the porosity and the increase of the roughness of the fibers, which constitutes an important advantage for us because the mechanical properties of the composites will be improved. In addition, these fibers are subjected to tensile tests to observe the effect of the three chemical treatments on their properties. Keywords natural fibers, chemical treatments, mechanical properties, bio-composites, agave
Design Failure Mode and Effects Analysis (DFMEA) for Automotive Safety Systemshttps://doi.org/10.31926/RECENT.2019.59.119 Abstract In this paper is presented an effective application of Failure Modes and Effects Analysis (DFMEA) in product design stages specific to vehicle safety systems. The scope of DFMEA is to eliminate as early as possible the design faults that could lead to the defective products. The potential failure modes, its causes, and effects are identified and severity, likelihood and detection are quantified in order to provide the corrective actions before first production run occurs. The results analysis for optimized stage indicate that all the analysed characteristics have a priority-risk level (RPN) located in the medium and low risk areas, which means an improvement of the design process performance. Keywords failure modes and effects analysis, vehicle safety systems, risk priority-number (RPN), design improvement
Particularities Regarding the Wear of SPMR150612-P30 Metallic Carbide Insertshttps://doi.org/10.31926/RECENT.2019.59.123 Abstract Metal cutting processes still present a high weight in obtaining various parts needed for the industry, both due to the quality of the surfaces and especially to the dimensional and geometric precision. The cutting tools are in continuous development and their wear is a constant concern of the researchers. Standardization of wear forms has become a necessity and ISO 3685/1993 is an example in this regard. However, the measurement of the average wear on the cutting tool flank is not detailed in the standard. This question naturally arises "In how many points should wear be measured on flank so that the average values are as close to reality as possible?”. If in the case of a uniform wear the approach is simple, not the same thing happens when the wear is non-uniform. This paper analyses in detail a non-uniform wear on the flank of a metal carbide plate mechanically fixed and through experiments proposes the optimum interval of making the measurements so that the average of values is as close to the average of the finer used interval, in this way significantly reducing the time spent on measurements. Keywords cutting, turning, wear of cutting tool
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