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

The materials of the article consider the influence of external mechanical loads of static and dynamic action (pressure force, mechanical impulse, vibration) on the change of electrophysical characteristics (electrical conductivity, specific capacitance) of film sensor elements. It is shown that an increase in the mechanical load on such an element with a simultaneous decrease in the interact ion time with a constant contact area leads to an exponential increase in the power and sensitivity of the reaction pulse, provided that such mechanical load does not exceed the mechanical strength of the sensor element. At the same time, the increase in the mechanical load on the sensor element at constant time and contact area, almost does not change the sensitivity of the reaction pulse (the maximum increase in sensitivity does not exceed 1.8%). In this case, vibrational oscillations in the frequency range 30… 85 Hz at mechanical forces of the order of 20 … 150 mN create response pulses of the order of 12… 45 mV/μs, which are perceived as “false positives” of the sensor elements. A further increase in frequency and mechanical effort leads to the destruction of the base of the sensor element and the detachment of the sensor f ilm from the base. Reducing the frequency and mechanical forces create reaction pulses up to 12 mV/μs, which does not exceed the allowable values of “white noise” (about 25… 35% of the minimum value of the reaction pulse).

The aim of this paper is the investigation of the effect of natural aging on the mechanical, physical and microstructural properties of an EN AW-6060 aluminum alloy. These properties were investigated during different aging treatments. Firstly, the effect of natural aging on properties was investigated, after which the influence of natural aging (room temperature pre-aging) on the artificial aging was studied. The results showed the beneficial effect of natural aging in both sets of experiment. During the natural aging, the hardness increased for around 20 % while electrical conductivity values were slightly higher than in the quenched sample. The hardness of the samples gradually increases up to 25 days of natural aging reaching a plateau state, after which the values of hardness remain the same. Also, room temperature pre-aging had a positive effect on subsequent artificial aging. Samples that were pre-aged for 40 days or more before artificial aging had around a 13 % increase in hardness values compared to the samples that were directly artificially aged. Electrical conductivity had increased by around 1 MS/m in pre-aged samples compared to only artificially aged samples. Optical microscopy investigations confirmed the existence of precipitated phases and their distribution in the microstructure.

In this study, the electrical conductivities and hydrophobic/hydrophilic properties of Polyacrylonitrile (PAN) + Polymethyl methacrylate (PMMA) composite nanofibers reinforced with nanowires were be investigated. The nanofibers are produced by the electrospin method. Their electrical conductivities and their hydrophobic/ hydrophilic properties were examined. The maximum the electrical conductivity value is 0.00298 S/cm at PAN + PMMA composite nanofibers with Ag nanowires (5 wt. %). The the biggest static contact angle occurred in PAN+PMMA composite nanofibers with 1 wt. % Ag nanowire. The static contact angles of all PAN + PMMA composite nanofibers with Ag nanowire were found to be bigger than those of PAN + PMMA composite nanofibers.

Cold forming process in the plastic domain of deformation causes strain hardening in the formed material. Strain hardening can be used for practically all metals and alloys to increase most of mechanical characteristics, however ductility and some others are reduced. In the paper experimental researches of the influence of effective strain on change of main mechanical characteristics such as tensile strength, yield strength, impact toughness, and some other characteristics of cold formed material were carried out and analyzed.

The results of the experiments are presented in the form of graphs. Special mathematical models for determination of different properties were obtained. These models are especially helpful for prediction of mechanical and other properties of a cold formed material. Knowing the material properties and their changes during the cold forming processes is very important for quality of the product and for planning the right technology of the forming processes.

The electroconductive and magnetic properties of nanomaterials containing carbon nanoforms synthesised for electrocatalytic, electrochromic, and ferrofluid applications, etc., are of interest to researchers. This article aims to understand the physical effects influencing the electroconductive and magnetic properties of materials synthesised by arc discharge. The nanomaterial formation processes leading to the formation of magnetic and electroconductive structures are also discussed. Arc discharge between graphitic electrodes results in the emergence of a fan-shaped jet of helium and carbon. The gasdynamic and temperature parameters of the jet depend on the parameters of the arc discharge and the buffer gas. Variations in the parameters of the carbon vapour flow change the kinetics of carbon condensation, leading to variations in the morphology and structure of the carbon material. The main external parameter of the synthesis (buffer gas pressure) was varied in the study, and correlations between the intensity ratio of the D to G peaks on the Raman spectrum and the electrical conductivity and magnetic susceptibility values were found. During the synthesis, nanographite structures were formed. However, the formation of an amorphous carbon structure on the free ‘zig-zag’ edges of the graphite fragments reduced the magnetic susceptibility, the electrical conductivity and the ID/IG ratio.

Structure and properties of low-alloyed copper-based alloys with Cr, Zr and Hf after severe plastic deformation (SPD) using techniques of high pressure torsion (HPT) and equal channel angular pressing (ECAP) have been studied. SPD significantly increases strength of the alloys by formation of ultrafine-grained structure. Cu5Zr and Cu5Hf particles suppress the grain growth in ultrafine-grained (UFG) structure more effectively than the Cr particles and provide additional hardening during aging. Moreover, it was found that the application of additional aging after SPD significantly improves service properties of the alloys (fatigue limit, wear resistance and electrical conductivity). This combination of properties results in a high durability of electrodes for resistance spot welding produced from UFG Cubased alloys.