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Recent 55

Vol. 19 (2018), No. 2 (55), 2018

 

This issue of the RECENT journal was edited with the support of:

CONTENTS



  • Azzedine BOUZAOUIT, Mounir GAHGAH, Mouna LAIFA, Leila RAMECHE

Study and Analysis of the Filter Clogging Effect on the Pressure Losses of an Axial Fan

https://doi.org/10.31926/RECENT.2018.54.005

Abstract

We present in this paper the results of an experimental study conducted on the analysis of the clogging influence of a filter installed on the suction pipe, on the axial fan operating parameters. In this study, we used an axial fan driven by a variable speed electric motor. The filter used has a removable filter element, in this context, we tested five filter elements with different filter surfaces and this to model the effect of clogging the filter on the pressure losses generated at the level of the filter in question. To obtain a differential pressure gauge installed upstream and downstream of the filter is used, the pressure value detected by the latter characterizes the relationship between the filtering surface (the surface crossed by the air flow at the filter) and the singular losses. The tests were carried out for different flow rates and speeds. The results obtained clearly show the effect of the filter clogging on the operating parameters of the fan, and characterize the relationship of these parameters with local pressure losses.

Keywords

linear cutting in abrasive water jet, dimensional variation

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  • Romeo CIOARĂ

Device for Turning Hemispherical Ends - an Innovative Solution

https://doi.org/10.31926/RECENT.2018.54.010

Abstract

Large series or mass production is to a great extent a characteristic of present day industrial production in several branches; two relevant examples are consumer goods and the automotive industry. Minimizing production costs and increasing productivity are major objectives of industrial activity and contribute significantly to ensuring marketplace competitiveness. In order to attain these goals machines manufacturing industry often uses customized technologies that deploy specialized or special machines dedicated to the respective production type and/or tools and devices that amplify the performance of machines with a wider destination. Conceiving and developing a more or less specialized device being less cost intensive renders it the preferred approach in many cases. The paper presents and discusses such an example, a device for turning hemispherical ends of various components, particularly of the holding bars of certain motor vehicle head restraints. A patent has recognised the originality of the device and several diplomas obtained in national and international inventics fairs.

Keywords

device, spherical surfaces, innovative solution, patent

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  • Ioan CIOBANU, Maria STOICANESCU, Sorin Ion MUNTEANU, Vlad MONESCU

Mathematical Model and Soft for the Heating Simulation of Metallic Parts in Solar Furnaces

https://doi.org/10.31926/RECENT.2018.54.019

Abstract

Lately, more and more experimental research regarding the use of solar furnaces was conducted in order to thermally process different materials. In this direction, Transilvania University made a soft to simulate the heating of metallic parts in such furnaces. The soft is based on a 3D mathematical model, presented here with finite differences. The data concerning the structure of the soft and the results that can be delivered are also shown. This soft is useful to preset, by computer simulation, the working parameters of solar furnaces with concentrated flux regarding the concrete processing of some metallic pieces (volume thermal treatments, surface thermal treatment, melting, welding, covering with surface layers, etc.).

Keywords

mathematical modeling, heating simulation, solar furnace, heat treatment

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  • Ioan MILOSAN

2k Factorial Design Used to Optimize the Linear Mathematical Model through Active Experiment

https://doi.org/10.31926/RECENT.2018.54.037

Abstract

The data presented in this paper is part of a comprehensive study on mathematical modelling by active experiment, using first-order designs in order to optimize linear mathematical models. In this respect, a 2k full factorial design was used. In the research, the experimentation plan was established to enable a higher number of experiments than the number of coefficients to be determined. There was established the matrix of the designed experiment and the calculation was performed according to the methodology specific to the 23 full factorial experiments. The results obtained by experimental design were employed in the study, using a special Mo-Ni alloyed cast iron, heat treated, whose elongation values were determined. Finally, a small number of determinations were used to determine the specific technological parameters and the maximum hardness of the analysed material.

Keywords

DOE, 2k factorial design, cast iron, elongation

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  • Maria STOICĂNESCU, Dragoș BUDEI, Eliza BUZAMET, Roxana BUDEI

Researches on Roughness for the Main Brands of Dental Implants

https://doi.org/10.31926/RECENT.2018.54.044

Abstract

Main brands of dental implants demonstrate superior features confirmed for years now. Among them, specific mechanical properties of materials that dental implants are made of, and mechanical properties of the parts themselves, are together with surface treatments, the most important traits that stay behind their success. The comparison of the main brands of dental implants, was made by means of objective analysis (roughness measurement, SEM microscopy with identifying chemical composition, tear tests, etc.). The study tried to penetrate into the depth of crystal structures and chemical formula behind good behaviour that was demonstrated in clinical applications. The study demonstrates the diversity of titanium alloys used in the production of dental implants and opens opportunities of new formulas. New proportions between the percentages of aluminium or titanium and vanadium, and other elements use (zirconium, niobium, etc.), will make possible to obtain new implants with superior performance.

Keywords

roughness, dental implants, titanium alloy

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  • Ioan GIACOMELLI, Maria STOICĂNESCU

The Influence of Low Temperatures on the Mechanical Characteristics of Aluminium Alloys

https://doi.org/10.31926/RECENT.2018.54.052

Abstract

Aluminium alloys, widely used in aeronautics, are subject to high temperature fluctuations during short periods of time. The paper studies the behaviour of an alloy of the 7xxx group subjected to repeated cooling and heating. Following the usual heat treatment, the cooling to -70 oC is applied one to three times in succession. The measurement of some mechanical characteristics, following the application of these procedures, revealed the existence of differences in the values. Therefore, determining the behaviour of these alloys subjected to extreme working conditions is useful.

Keywords

aluminium alloys, mechanical characteristics

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