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Recent 51

Vol. 18 (2017), No. 1 (51), March 2017

 

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

CONTENTS



  • Bogdan ARSENE, Gavrilă CALEFARIU

Qualitative Analysis of Replacing Grinding with Hard Turning

Abstract

Because of the development and rising of the manufacturing industry, the cutting tools and machine-tools manufacturers had to innovate and develop newer solutions for industry, a more efficient, from an economic point of view, and more environment friendly, to maintain the competitiveness in the market. Therefore, with the help of the last generation of cutting tools with high hardness and specific geometry, as with very rigid and high precision machine tools (lathes), hard turning became quickly a serious alternative for replacing grinding in many applications. The concerns for this solution started about one decade ago and is applied in high-end industries that have stronger directions to be the best in class. Current papers limited themselves just on highlighting test results performed by different tool manufacturers and users. This paper refers to a systematic approach of replacing grinding with hard turning, incorporating relevant experiences presented both in literature and in the authors direct research. We have highlighted the advantages of hard turning in relation with grinding, as well as the limits of replacing hard turning with grinding.

Keywords

manufacturing, cutting tools, hard turning, grinding, competitiveness

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  • Marcel DĂIAN, Ioan CIOBANU, Mihai Alin POP

The Influence of Speed on the Wall Thickness of Centrifugally Cast Parts

Abstract

The paper discusses a study on the vertical centrifugal casting of tubular parts. The necessary speed for the casting of cylindrical parts by this procedure is determined starting from the equation of the interior surface of the liquid alloy during rotation. The study of the influence of speed and part dimensions on the wall thickness of the casting is followed by a comparison of the theoretical and experimental results. The conclusions concern the determination of the optimum speed for a given part.

Keywords

casting, centrifugal casting, leaded aluminium-silicon alloy

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  • Valerii KYRYLOVYCH, Roman MORGUNOV, Lubomir DIMITROV, Olga TOROPOVA, Svetlana KUMOVA

Information Models of Flexible Manufacturing Cell Components and Related Drawing up Features

Abstract

The paper analyses the feasibility of using the quaternion as a single semantic unit for compiling the information models supported by the analysis results of existing creation methods of information models of flexible manufacturing cell individual components, in relation to the general concepts of the theory of quaternions. By structural components, the authors refer to industrial robots (handling systems and grippers), main and auxiliary technological equipment units, used on devices and objects of manipulation (OM) such as workpieces, semi-finished products, assembly components, etc. The authors present the use of the proposed approach for compiling the information models of the separate geometric primitives and the ordered set for the kinematic structure of the manipulation system of a real industrial robot. Further indicated is the versatility of the proposed approach, describing basic geometric primitives and their possible combinations of 3D parameters of the individual structural components of a flexible manufacturing cell, while displaying the mobility of the components or the immobility of units or elements, specifying the type and the value of relative displacements.

Keywords

optimization, financial management, cost

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  • Mihai Alexandru LUCA

The Retained Austenite Content Reduction in Tool Steels due do Vibratory Tempering Applying

Abstract

The presence of residual austenite in the tool steels determine hardness and durability reducing of the tools. In order to reduce the residual austenite content can be applied the quenching below 0 C, but in these conditions increase the manufacturing costs. A more advantageous to reduce the residual austenite is the vibration of the tools during the tempering treatment. In the research was used a vibratory tempering bath excited with a resonant bar calibrated on the network frequency. The steel C80U kept after tempering 10.49% Ar. After the normal tempering (190 C - 1h) are preserved Ar 3.2%. Under the vibration action, it produces a more advanced transformation, resulting only 2% Ar. The material vibrated at tempering is high quality and the additional costs are insignificant.

Keywords

tool steel, vibration, heat treatment, tempering, retained austenite, eddy current

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  • Elena MACHEDON, Mihai Alexandru LUCA

Analysis of Resonance Curves for Spot Welding Technology Optimization

Abstract

Spot welding is a complex technological process in which the interaction occurs between the electrical, thermal, mechanical and metallurgical phenomena. Different researchers around the world are studying the problems generated by dilatations and contractions in welded joints and the microstructure changes that cause dangerous internal tensions or unacceptable deformations that affect the quality and reliability of welded products. Were experimented, developed and tested various welding conditions and different materials using both theoretical and experimental methods. In this paper are shown the results obtained by dynamic tests applied on specimens subjected to spot welding. The specimens made out of sheet metal for pressing were welded with two different welding regimes. The number and succession of the points execution has varied. In these conditions different internal tensions and deformations was result. For each test specimen to the basic harmonic excitation, the resonance curve was built. Based on the evaluation of resonance curves, the logarithmic decrement was determined for evaluation of internal friction. Experiments have shown that in certain technological circumstances results a lower or bigger internal friction, respectively lower or major internal tensions. The proposed test method is useful for choosing the optimal manufacturing variants when conducting the approval of a new product or when it comes to a reliability analysis.

Keywords

spot welding, resonance curve, internal friction, logarithmic decrement, vibration analysis

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  • Ioan MILOSAN

Experimental Results of a Carbon Steel Analyzed Using the Grubbs Test

Abstract

The paper presents an example of calculation for the data validation by using the Grubbs tests. The values used of Rockwell hardness (HRC) of C45 medium carbon steel. All specimens were heated an electric baking temperature of 850C, while keeping time to equalize the temperature in samples being 20 minutes and then the cooling energy is made in water at room temperature, i.e. 20C. After quenching, samples were subjected to high-tempering operation at 600C. Solving the Grubbs test was done in seven steps, which have analyzed the results and finally some statistic conclusions were done. The second alternative hypothesis of the Grubbs test that says there is only one abnormal result in the data sets analyzed was checked in this paper so this test was properly applied in this experimental research.

Keywords

C45 steel, heat treatments, hardness, Grubbs test

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  • Sebastian POP, Andrei LUCHIAN

Considerations Regarding Detection and Combat Systems for UAVs

Abstract

The use of UAVs in modern airspace means to required new concepts because of the non-compliance in the aeronautical domain, such as anti-drone system. Anti-drone combat systems are assigned to detect, identify, neutralize or destroy miniaturized air mainframe systems (UAVs), when the UAV violates areas or executes hostile action. These systems combine the active detection capability with passive detection systems. Thus, UAVs neutralization is achieved by radio methods or actual destruction. The articles aim is to make an introduction to the anti-drone systems and propose innovative technical solutions.

Keywords

UAV, sensors, anti-drone, target

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  • Vasile PRISACARIU

Performance Analysis of the Flying Wing Airfoils

Abstract

Flying wings flight performances depend directly on the 2D aerodynamic optimization (choosing aerodynamic profile). The aerodynamic profiles used in tailless aircraft have a series of specific constructive performance. This article presents a piece of analysis regarding the 2D aerodynamic profile used in the construction of a flying wing UAV type.

Keywords

aerodynamic analysis, Phoenix airfoil, XFLR5, Profili 2.21

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