Friction and wear experiments were performed on carbon fiber-reinforced polymer (CFRP) composites, and the tribological behavior of these materials under boundary lubrication (based on the 5100 4T 10 W-30 engine oil with TiO2 Degussa P25 nanoparticles) was investigated. Experiments were carried out in two directions: one at a different normal load from 6 to 16 N and one at a low sliding speed of 110 mm/min under boundary lubrication conditions. The obtained results reveal the stick-slip effect and the static and dynamic coefficient of friction decreased slightly with increasing normal applied load on the carbon fiber reinforced polymer composite pairs. The second direction highlights through experimental tests on the pin on disc tribometer that the friction coefficient increases with the increase in normal load (20–80 N) and sliding velocity (0.4–2.4 m/s). On the other hand, it is found that the friction coefficient is slightly lower than in the stick-slip phase. During the running-in process, the friction coefficient of the CFRP pair increases steadily as the rubbing time increases, and after a certain rubbing period, it remains constant regardless of the material of the counter face. The obtained results show that for the observed interval, the influence of normal load and sliding velocity have relatively small fraction coefficients and low wear depths. A 3D analysis of the profile demonstrated the texture of wear marks and tracks of these engineering composite materials. Furthermore, the height variations of wear marks and the morphologies of the worn surfaces of specimens under boundary lubrication conditions were analyzed.
Within the Faculty of Machine Building from the Technical University of Cluj-Napoca, Romania unconventional technologies researches were performed for 20 years. The team focused on national research projects referring to micro machining and special applications. EDM process (Electric Discharge Machining) has a great importance to the industry. Even if it never be able to compete with the metal cutting manufacturing process in terms of material removal rate, today it is the main manufacturing process of complex die and mould, due to the major advantages presented in this paper. Today, also the precision of the process competes with the milling process in terms of quality of the surface, which can arrive at values that, in some cases, are better than the values for grinded surfaces. The article presents the importance of the process in the industry of stamps, which can not be processed with other methods, due to special materials and forms that are wished to be obtained. The article presents comparatively the values of the roughness obtained by EDM process on different types of materials and by different process parameters. Concerning the optimisation of the EDM technological parameters, the research has been done on different types of EDM machines. The final scope is to elaborate a technological data base with the purpose of optimising the EDM process on different machines.
In this paper, an attempt has been made to model the surface roughness through response surface method (RSM) and ANOVA when drilling CFRP composites. Drilling is the most common machining process applied to CFRP. However, the users of this kind of composites are facing difficulties to machining it, due to its properties. Because of the bad effects that lubricants have on the fiber-reinforced composites, the machining of these materials is performed without coolant. On the other hand dry machining offers the risk of a thermal damage induced by high process temperatures. The current experimental analysis is focused towards determining process temperatures with different tools and drilling parameters.
The study aims to increase the efficiency of the use of the pipe-piston unit by ensuring the reliability of the measurement results based on the development of calibrating technique for the pipe-piston installation. Theoretical research is based on using the principles of system and process approaches. To solve the scientific problem, the fundamental provisions of statistical methods and experimental methods were used; methods of mathematical modeling of estimation of measurement uncertainties. Based on the results of the work, the normative document “Metrology. Installations of a standard pipe-piston. Calibration technique”. The approach to controlling metrological characteristics of the pipe-piston installation, based on estimating the uncertainty of measurements during its calibration, was further developed. Application of the proposed approach allows one to control the metrological characteristics directly on site without disrupting the working product’s accounting process and increasing the pipe-piston installation’s efficiency by an increase in the reliability of measurements and ensuring repeatability.
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