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Open access

Vasile Andrei, Cornel Marin and Alexis Negrea

Abstract

According to the IWA norms, the water loss category includes also the apparent loss water due to measurement errors of the water meters used at the connections. This paper presents the experimental results obtained during two years of registrations in TARGOVISTE’s Water Company network. A program for verifying the water meters used for connections has been implemented according to a statistical distribution, depending on the number of appliances and their dimensions. Using a theoretical simulation model, calibrated on the basis of the actual reference flows measured on the metrology approved measuring stand, a procedure was developed to assess the level of deviations in the fully metered water distribution network. Depending on the values of deviations and flows actually recorded by the meters in the distribution network, it was possible to estimate the percentage of the losses from the actually used water meters.

Open access

Nicolae Angelescu, Cristina Stancu, Sofiane Amziane, Vasile Bratu and Elena Valentina Stoian

Abstract

Refractory concretes based on aluminous cements are used with great success in areas where high temperatures are required. The mineralogical composition of the high alumina cement is the main factor which gives the physical and mechanical properties at high temperatures of refractory monolithic materials.

It is therefore desirable to use high alumina cements based on mineralogical compounds with high refractoriness, because in the end those beneficial properties can be found in the final product - refractory concrete.

The aim of this paper is to design, realize and characterize different compositions of high alumina cements based on mineralogical compounds with the highest refractory from the CaO-Al2O3 binary system (i.e. CA, CA2, and CA6), and to find ways of hydraulic activation of calcium hexa aluminate, also.

Open access

Ivona Petre, Aurora Anca Poinescu, Adrian Catangiu and Simona Mihai

Abstract

With the development of industry have made efforts to improve the performance of braking systems of motor vehicles on public roads. The choice of materials used for coupling brake system involved the development of new materials that meet safety requirements in circulation. During braking of any vehicle, due to the friction created between the disk and pad, temperature rise occurs with negative effects on the process of slowing down the vehicle. Mechanical and thermal stress being put on the brakes is very high. Due to overheating, brake discs and pads may warp or crack, and the material they are made may their change its structure. These defects give rise to vibrations and noise during braking, to reduce the coefficient of friction, reduce the effectiveness of the braking mechanism. This paper proposes a study regarding the thermal stresses effects of brake mechanism on the disc material of a car Dacia Logan. It proposes a theoretical model to calculate the temperature that occurred during the operation of the braking system and experimental analysis on the influence of temperature on the brake disc material.

Open access

Florina Violeta Anghelina and Dan Nicolae Ungureanu

Abstract

The structural transformations occurring at tempering for some high-speed steels are a subject of research for which have been dedicated numerous studies. More complex compositions of the high-speed steels were direct consequence of the complexity of structural transformations which occur during heat treatment. On the other hand, current tendency in energy requires maximum efficiency and rational use of heating sources used in industry. Thus, only a precise knowledge of the kinetics of transformations occurring at tempering can be a basis for optimizing this treatment. Although cobalt is used for a long time as an alloying element, though relatively recently it was considered important to the properties of rapid steel. These circumstances, combined with the lack of quantitative information on the kinetics transformation at tempering operation treatment for some steel has led to this paper. The thickness of the studied samples is 5 mm and was taken from the annealed steel bars. These samples were subjected to hardening and tempering treatment in salts bath. Heating for hardening was performed in two steps, at 5500C and 8300C. Austenitizing was done at 12000C, during 120 seconds. The cooling was done up to 5300C in salts bath, with a keeping of 15 seconds, and then air cooling was done. On these samples were carried out, HRC Rockwell hardness measurements, and X-ray diffraction analysis.

Open access

Radu Iatan, Mihai Stătescu and Cristina Salca

Abstract

It is known that the transportation of oversized technological equipment raises particular poroblems, both from the economical and technicall point of view. Knowing the loads in the platform-equipment assembly, the intensity and the direction of the wind loads, the condition of roads and the way these act is imperative. The present paper seeks to determine the expression of the loads obtained on a platform with an even number of axles, loaded with a technological equipment and neglecting or not the deformation of the suspensions and tires.

Open access

Radu Iatan, Pavel Florescu, Carmen Popa and Gheorghiţa Tomescu

Abstract

Starting of the characteristic expressions of some breaking polynomial criteria, known and used in practice, it is highlighted how to assess the safety coefficients used in some practical cases. It is obvious that the decision belongs to the user given the experience in the adequate technical domain. In this regard it must not neglect the fact in that the breakage is produced most often in unpredictable moments, conditioned by multiple factors, dependent on material, on manufacturing technologies of finished products, respective the operating conditions.

Open access

Liliana-Laura Badita, Gheorghe Gheorghe, Vasile Bratu, Valentin Gornoava, Marian Vocurek, Aurel Zapciu and Iulian Sorin Munteanu

Abstract

Taking into account the importance of mechatronic applications, researches regarding the possibility to improve the lifetime of mechatronic components were made. Nanostructured metallic thin films (Ti, Cr, Al and Ti/Al multilayer) were deposited on different types of steel substrates, because nanomaterials have exceptional properties in relation to the common materials. In this paper a part of the results obtained after mechanical and topographic characterization of the thin films are presented. Cr is the deposited thin film showing the highest hardness on the surface of steel substrate type OSC. After the scratch tests realized, Ti layer presented the best adhesion on all types of steel substrates used in experiments. The results of these researches could be extremely useful for engineers in the mechatronic field.

Open access

Vasile Bratu and Ileana Nicoleta Popescu

Abstract

In order to determine the optimum geometry of the ingot mold format (the format of ingot mold with a diameter per height ratio H / D <3 and the conicity of minimum 7%) was analyzed by mathematical modeling of solidification and segregation of the carbon and sulfur in it.

It was considered 205Cr115 steel type (according with , STAS 3611 - Romanian stardandization) and known also as X210Cr12 steel type (according with European standard). It has been considered an element of volume of coordinates x, y, z in the solidifying ingot and have made the following assumptions: (i) the equilibrium distribution ratio K, is applied to the solid-liquid interface; (ii) solid diffusion is negligible during solidification; and (iii) the solid density is constant during solidification. In carrying out the simulation of segregation mechanisms are resolved heat transfer equation, that simulating the solidification process and are are solved the interdendritic fluid equation of motion.

Open access

Mirela Popescu and Bela Varga

Abstract

In this paper it was studied the structure of EN AC 5083 aluminum alloy depending on cooling conditions. By cooling curves recorded for different casting conditions there were calculated the cooling rate (vr). The structural analyzes, performed by Image Pro-Plus 6.0 software, allowed both be highlighted structural particularities of various conditions for casting and establishing the correlation: lg d = lg v + n (where d is the dendritic parameter).

Open access

Adrian Catangiu, Dan Nicolae Ungureanu and Veronica Despa

Abstract

The strength of materials is a complex function which involve two main components, material nature and the presence of defects. Usually glasses exhibit a fragile behavior due to a numerous flaws and the effect is a large range of data scattering in tensile strength measurement. The Weibull probability density function was applied to describe the scatter of experimental data in tensile test, which emphasize a difference between variance in case of tensile strength of three stainless steel grades and glass epoxy composite. The main goal is mathematical modeling of those distributions and finding of equations which predict the probability of failure for a sample subjected to a specific stress.