Hybrid nanocomposite epoxy-based coatings containing ZrO2, ZnO and Fe2O3 nanoparticles (≤50nm) were deposited on Grade A naval steel substrates by dip-coating technique. The surface morphology and the mechanical properties of coated steel samples were analyzed by optical microscopy and CETR tribometer, respectively. The mechanical measurements showed that 1wt. % doping metal oxides nanoparticles significantly affect the mechanical behavior of coatings in terms of microhardness and friction coefficient. Best results were obtained in the case of Fe2O3 and ZrO2 doping, for which were obtained microhardness in the range of 90-120MPa and 142 MPa, respectively. Regarding the friction coefficient, values in the range of 0.02-0.08 were obtained

The paper addresses the issue of the influence that the law of friction has on the dynamic behavior of the mechanical system that interacts with a tribosystem. The emergence of certain nonlinearities of higher order into the law of friction leads to an intensification of the dissipative process and to tribosystem destabilization. Consequently, friction excited self-oscillations are generated into the elements of the mechanical system with a wide spectrum of frequencies, sustained from the external source of energy. The theoretical and experimental modelling of the dissipative process and of the generation of is based on the frictional harmonic oscillator that interacts with the tribosystem. The oscillator is used as a sensitive element to the fluctuations of the frictional force and as a measure of the dissipated energy. Starting from the model, the elaboration of a method and of devices for experimental research provided the opportunity to study the behavior of the tribosystem in unstable operating

The paper presents experimental results of the mechanical tests (alternating plane bending and Charpy impact) performed on samples obtained from X 65 PSL 2 steel slabs. Samples were taken from different batches, cast at the same continuous casting machine. Since metallographic analyses indicates a heterogeneous micro and macrostructure, the samples were collected from different areas of the slabs (surface and middle). In order to highlight the influence of hydrogen embrittlement on mechanical characteristics of steel, some specimens were hydrogenated into hydrogen sulphide environment, for different periods of time. There were calculated the hydrogen embrittlement degree and the structural heterogeneity degree of the slabs structure with data from the two types of the mentioned tests. It is found that the hydrogen embrittlement mainly influences the fatigue characteristics. The structural differences between surface and middle of the slabs are mainly highlighted by the impact tests.

The paper presents the mechanical behavior of hydrogenated and nonhydrogenated X 65 PSL 2 steel, used for oil facilities, during an alternating symmetric bending cycle. The samples were hydrogenated for 96 and 192 hours. Some of them remain nonhydrogenated. The aim of the research was to determine the influence of hydrogenation time on number of cycles supported by samples till they crack It was found that hydrogenation time has a major importance on this number.

The paper presents the dependability concept for technical and socio-technical systems. There are presented their components and their characteristics. It is also presented the human in the context of dependability of technical systems and a human errors classification. Finally, a technical system representation is given, highlighting the parameters that could be influenced by the human errors.

The paper is focused on modification of surfaces properties by laser cladding. To follow the corrosion behavior in different media of laser cladding layers made of nickel based alloy Ni - Cr - B - Fe - Al. It was studied using the potentiodynamic method. Elasto – plastic behavior of the assembly base material - deposited layer was monitored by using sliding indentation, in dry friction conditions. It was determined the bearing capacity of surfaces.

The paper presents a study about the changes of viscosity for soybean oil, olive oil, corn oil and rapeseed oil in different conditions of forced oxidation. The oils have been tested at 110, 120 and 130 C for 5 and 10 hours. By analyzing the experimental results, we can notice an important increase of viscosity for soybean oil oxidized at 110C, for corn oil, major changes in viscozity we can see at 120C and for rapeseed oil and olive oil a major increase of viscosity is obtained at 130C. This shows a good stability at oxidation for rapeseed oil and olive oil comparing to the other two oils studied.

To increase resistance to wear of the surface layers made from 0.45% C steel, a multilayer deposit by powder injection with the chemical composition Cr 8.9%, 4.5% Fe, 5.1% B, 2.4% Al, 0.6% Cu, and Ni was tested in a molten bath with a continuous wave of CO2 laser, coupled to a table within x-y-z coordinates. The layers were characterized by microstructural analysis, qualitative analysis of phase with the radiation difractometry X and EDX microanalysis. It was determined the friction coefficient developed during sliding indentation in dry friction conditions.

Sealing systems used fir non-metallic rod pneumatic drives have hard duty conditions, including the absence of any kind of lubricant and non-linear thermal regime. Due to this, the wear evolution of the lip -rod pair can be difficult to be estimated. The paper propose an ANN based method for wear prediction during service life of the hp seals, taking into account some seals' working behavior influencing factors.

The paper presents shear stability and extreme pressure test results in order to characterise hydraulic oils. This comparative study is used to establish the way that the mechanical solicitations during service life of the oils affect the viscosity modification and thus the quality of oils performance.

A theoretical model adapted for studying steel continuous casting technology was proposed.The model based on system theory contained input/output,command,and control parameters.The process was divided into five stages,i.e.,tundish,mold,guiding system,guiding-drawing system,and guiding-drawing-soft reduction sys- tem.The model can be used to describe the physicochemical processes,thermal processes,chemical processes,and characteristics of the cast material according to the above-mentioned stages.It can also be applied to other metallur- gical technologies and even to other industries （chemistry,food,etc.）.

Each system (stand - driving) and the continuous rolling line to which it belongs have its own functional and energetically parameters. To reduce any faults of the strip surface it is also necessary to check (eventually having a control line) the roll surface quality, the work roll eccentricity, and depending on the disposal by compensation, of eccentric lobes. The appearance of the specific faults on the rolled strip-during the experiments carried out is duet o the vibrations covered by the range of 100-300 Hz. This many-sided theme needs mathematical patterns to correlate the factors and the dimensions (strip types, technological flow, driving) which should be able to basically support the monitoring system. Taking into account the aspects regarding the quality of the surfaces, the geometry of strips and the costs, it necessary to do a monitoring

THE ANNALS OF UNIVERSITY “DUNĂREA DE JOS“ OF GALAŢI FASCICLE VIII, 2007 (XIII), ISSN 1221-4590 TRIBOLOGY

Based on the tribosystem concept, taking into account the presence or the absence of the lubricant, the authors make some consideration on tribosystem “state” notion, defining friction and antifriction states of tribosystems. Researches were done on two friction couples (tribomodels): basalt syntherised/cast iron and high density wood/cast iron. In the first case, the lubricant was mineral oil K 95 and a soap emulsion and water for the second. The separation between friction and antifriction states is possible by the help of an imposed friction coefficient and the thermal state. These can be considered tribological state indexes of a tribosystem. For µ≤0.08÷0.1, the tribosystem has an antifriction state, while for the values µ ≥0.25÷0.35 a friction one.

The paper presents an experimental - analytical method for sliding indentation elasto-plastic and plastic deformation study. The research is focus on ditch like trace cross-section profile. Form (circular or parabolic) and dimensions (depth, width, maximum, minimum, average radii) are determined or computed. A comparison between real trace profile and indenter one is made with the object of finding the sense of elastic recovery. The method is used for alloy steel (40 Cr10 and 30HRC hardness). The research reveals that through the use of method accurate results are obtained. For example, for the steel that was studied, results that the indenter radius is on average three times bigger than the profiles average radii, the form of the profiles is parabolic and can not be approximated with circular one.

The biodegradable and ecological lubricants complete the range of lubricating products, including also mineral oils. These lubricants may be used for environment protection in applications where contaminating risk is high due to losses either on soil or in water. This paper presents experimental results on oxidation resistance of sunflower oil used as possible industrial lubricant. Tests were done using both unadditived sunflower oil, for grades as obtained after different steps of manufacturing process and additivated sunflower oil. The additives were ascorbic acid and hydroquinone, added in the first two stages of manufacturing process. The authors established that the vegetable oil obtained after the first two steps of manufacturing process presents the most reduced oxidation phenomena as compared to the oils obtained after other manufacturing steps