International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The occurrence of road accidents due to a pavement surface with inadequate roughness is an alarming issue. This problem involves not only the design, construction and maintenance of road pavements, but also the properties of the materials used in the asphalt mixes, traffic volume and vehicle speed, as well as tire characteristics, human factors, environmental conditions and many other contributing elements. As a result, there is a growing awareness of these problems and adequate measures have to be taken by road administrations in order to improve traffic safety. For the design, construction and maintenance of a modern road network, along with strength and sustainability, skid resistance has become an integral part of a safe and efficient road system. With the increase in traffic speed and volume, the road pavements built today must have initial and continuous qualities of high skid resistance. It is a well-known fact that the pavements skid resistance is reduced primarily by mechanical wear and polishing due to traffic action; however, to what extent the friction characteristics are diminished and the other causes and effects of this reduction are problems that road engineers have to face. Although the automotive and tire industries have contributed greatly to the research and development of skid-resistant road pavements, it is quite obvious that most of the improvements will go to pavements. In the following, the paper will focus on establishing the roughness criteria that can be applied from the early stages of the construction of a road infrastructure, by selecting those materials and techniques that lead to a high level of roughness and thus traffic safety. Also, the paper presents the results of recent experimental studies undertaken to determine the road roughness, using the microtexture as well as macrotexture criteria, conducted in Romania on the national roads DN 2 km 212 + 000 and DN 15 km 290 + 870.

Currently, one of the most important and monitored surface properties is the ability to achieve the highest possible level of adhesion after applying a layer of paint or glue. To guarantee this property, it is extremely important to choose the right surface pretreatment. The paper is focused on chemical surface pretreatment and subsequent evaluation of morphological surface changes after application of various selected types of chemical pretreatment based on roughness parameters.

In this work the possibilities of reducing the roughness and defects of surfaces obtained by 3D printing with selective laser melting (SLM), via reactive electrospark surface modification (ESD) with low-melting AlSi alloys has been shown. The influence of the energy parameters of the ESD process on the roughness, microstructure, microhardness and performance characteristics of the coatings has been studied. Surfaces with new phases and ultrafine crystal-amorphous structure with particle sizes from micro to nano level, with new relief, with thickness up to 15 μm and microhardness up to 11 GPa were obtained, as the initial SLM roughness from Ra = 8-11μm is reduced to Ra=3-5 μm. Possibilities for control of the characteristics of the coatings and purposeful synthesis of new phases by changing the parameters of the spark discharge have been established. The parameters of the ESD process, which provide simultaneous reduction of SLM surface roughness, removal and erasure of the defects and targeted reactive synthesis of new phases with high performance properties and wear resistance, are defined and optimized.

Surface quality and its evaluation is currently a very important part of surface preparation for all types of technologies involved in surface formation. Knowledge of the new surface formation mechanism is of great importance from the point of view of production, because it allows to understand the nature and properties of the newly created surface and thus gives the opportunity to both improve the processes used and create a smooth process. surfaces. Therefore, any changes that occur in the surface layer of the component can be considered as changes in the surface quality. The paper deals with the expansion of current knowledge in the evaluation of metal surfaces microgeometry in terms of current trends.

To create a high-hardness and wear-resistant coating on the heat-resistant aluminum AK4 alloy, the technology of microarc oxidation is used. The possibility of forming an oxide layer on the surface (mainly of α−Al2O3 and γ−Al2O3 phases) with a thickness of about 150 μm and a hardness of 17000 – 18000 MPa is shown. For this, the process of microarc oxidation was carried out at a current density of 20 A/dm2 in an electrolyte of the composition KOH (1-2 g/L) and Na2SiO3 (6-12 g/L). The obtained properties of MAO coatings on the AK4 alloy make it possible to effectively use such materials for engine elements.

We present non-trivial spatio-temporal patterns observed in reactive-wetting of mercury droplets spreading on thin metal (silver or gold) films on glass at room temperature. This is the only known study of reactive-wetting at room temperature. We show that there exist two main regimes, the bulk propagation regime and the interface kinetic roughening regime. In both regimes, rich spatio-temporal patterns are observed. We study and characterize these patterns using statistical physics tools, such as the growth, roughness and persistence exponents, and show the manifestation of surface tension relaxation in these statistical measures.

Drilling is most often associated with hole-making. The surface roughness parameters represent a measure of surface quality, and it is mainly influenced by the cutting process parameters (cutting speed, feed rate, drill diameter), tool geometry, tool material, tool type, type of processing, coolant and lubricating fluid, tool machine and type of work piece material.

The purpose of this paper is to explore the effects of drilling parameters such as; cutting speed (vc), feed rate (f), drill diameter (d) and drill point angle (θ) on the surface roughness. There are different parameters used to estimate the severity of the surface roughness (Ra, Rz, Rq and Rt). The arithmetic average deviation Ra is commonly used for finish surface processing. The experimental plan was based on Box –Wilson Central Composite Design. First order model predicting equations for surface roughness have been established by using RSM methodology to collecting the experimental data, during machining of Ck45E steel according to EN 10083-1.1191 in wet drilling process, using HSS coated TiN drill tools.

Aluminum matrix composites composed of Al, Al-5,6 wt.% Cu (Al5.6Cu), Al-7 wt.% of alpha brass α-Cu_0,8Zn_0,2 (Al7CuZn) and Al-9 wt.% of nickel brass Cu_0,64Zn_0,31Ni_0,05 (Al9CuZnNi) as the matrix and 15 vol.% of TiC and synthesized Al-Ti-C master alloy (MA) as the reinforcement were successfully fabricated by hot forging. Sliding wear tests were conducted at different velocity and loads using a pin- on-disc apparatus and under dry conditions. The results of the investigations indicate that the coefficient of friction significantly lower in composites with Al-Ti-C master alloy then that reinforced with TiC, while the wear rates are lower in composites with Cu additions. The post-test analysis of the material damage mechanisms were examined by optical profilometer.

The main issues are considered in this topic is the impact of pneumovortex effect on the free ball located inside the cylindrical thin-walled elements. Researches were carried out with various diameters of deforming balls and lengths of cylindrical parts. Obtained results show high precision of roughness inside walls of cylindrical tubes.

Because of the surface oxide film’s presence, a negative electric potential and formation of the disadvantageous residual strains under the galvanic film’s putting on soft metals and alloys, there are the coming of considerable technological complications. This is obstructive to the good interaction between the films and main metal. In this case it is expedient the technological combination the galvanic film of the surface with surface plastic deformation. In this case, the surface plastic deformation is realized by the tools with radial feed of the deforming elements.

The processing of the grooves for a putting gaskets in the hydraulic holes is embarrassed because the high requirements for their precision and roughness. In this case like a method for finish processing it is suitable using surface plastic deformation. This method ensures as the quality of the machining surface as higher productivity.

Achieving the appropriate characteristics of treated surfaces by SPD is not only entails with choose of relevant scheme solutions, deforming elements, regimes and conditions of processing, but also with the specifics of the re-implementation of the technological impact. It is reasonable to assume that re-implementation of the technological impact is identical to its previous implementation, if with that is achieved only generates additional smoothing effect due to the increased multiplicity of the metal deformation in the same area of the treated surface.