Irina Boiko

Wear Estimation Using 3D Surface Roughness Parameters

The aim of this work is to propose a methodology of lifetime prediction of details by new approach for linear wear intensity determination using 3D surface roughness parameters. For qualitative evaluation of the wear process the linear wear intensity (Ih), which may be determined separately for the plastic and elastic contact, is commonly used. Since the elastic contact is mainly required in pairs of details in mechanical engineering in these paper this kind of contact was examined. In our research, the random surface model was used. The surface machined with abrasive instruments (grinding, polishing, honing, etc) has the irregular shape of surface roughness, which can be described with random function. Irregular surface is expressed by a random field h(x, y) of two variables x and y which are Cartesian coordinates of a surfaces point, where the height of roughness asperity h(x, y) has a normal probability distribution. In wear research the probability theory was used. Further in deformed volume calculation, as well as in determination of the length of the surface’s contact the 3D surface roughness parameters were used. The strong correlation between 3D roughness parameters Sa (arithmetic mean height) and Str=Rsm1/Rsm2 (texture aspect ratio of the surface) was revealed. As a result of research, the methodology of lifetime prediction of details by new approach for linear wear intensity determination using 3D surface roughness parameters was elaborated and proposed. After calculation of linear wear intensity Ih, it is possible to estimate lifetime of wearing details. So, at a first time in wear estimation the 3D surface roughness parameters were used. The results of this work have wide practical application, for example in design, texture specification on drawings etc.

Screen Elements Made of Perforated Steel Tape and their Application for Shielding Electromagnetic Fields

In the present work the methods for producing flat and three-dimensional shielding screens from the perforated steel tape are proposed. The possible application variants of mentioned screens are offered and analyzed. Main attention is given for producing one-layer and multi-layer screens with cellular structure due to its relatively low weight and technological elasticity – complex three-dimensional structures could be done successfully.Examples of produced shielding screens from the perforated steel tape for protection from electromagnetic fields in different frequency range are offered and tested. The efficiency of a shielding material was determined by measuring the magnetic field before and after applying the shielding material. Distribution of the magnetic field behind the shielding screen was determined by software vector mapping. Shielding efficiency was measured for 1) a three-layer perforated steel screen; 2) an one-layer perforated steel screen - shielding screen was placed in between the magnetic field source and the measurement point forming a two dimensional screen; 3) copper composite sprayed screen. During experimental investigation it was established, that a three-layer perforated steel screen application allowed the 27% reduction in the magnetic field, while one-layer perforated steel screen gave only 12% reduction. Copper composite sprayed screen reduced magnetic field by 15%.Recommendations for producing the multi-layer perforated steel screen accordingly to shielding efficiency are elaborated and laid down. The discussed material carries also ecological significance, since the material is produced by waste products (after stumping etc.). Therefore the production of such materials comes with reduced cost both in light of capital expenditures and ecological footprint.

New Methodology for the Life Time Prediction of Wear Parts in the Mechatronic Systems

This paper is devoted to the elaboration and verification of the new methodology for the life time prediction of wear parts in the mechatronic systems. The methodology is based on the using of the 3D surface texture parameters instead of 2D roughness parameters for more precise prediction of the life time of machine parts.Experimental testing of proposed methodology for the wear parts of linear motion modules of mechatronic system was done using 3D profilometry, pin-on-disc tribological testing for determination dynamic friction coefficient, slidability and static friction coefficient measurements. The new approach for life time prediction is based on using following 3D texture parameters: Sa, Sq, Str, Rsm1 and Rsm2. It is established, that the amplitude and spatial parameters (Sa and Str (Rsm1) accordingly) have a most significant influence on the static and dynamic friction coefficient as well as on the sliding properties. It can be assumed, that for wear parts and for improving sliding properties the surfaces with less Sa and bigger Rsm1 are recommended.Within the Ti-based multi-layer PVD coatings the best prognosis for the life time was achieved for the samples with multi-layer Ti-TiN-Al PVD coating. Proposed methodology is acceptable for use in practice of engineering calculation, in design etc.

Contact Estimation Using 3D Surface Roughness Parameters

This work is devoted to the elaboration of the new methodology for the wear parts contact estimation using 3D surface roughness parameters defined in the standard ISO 25178-2:2012 for friction and wear rate determination. In our research the random surface model was used, where the height of surface asperities h (x,y) has a normal probability distribution. As a result of research the equations for estimation of the elastic contact area and friction coefficient were derived. The existence of the correlation between friction coefficient and 3D surface roughness parameters was proven as well. The results of this work could have wide practical application, for example in design, for the texture specification on drawings, calculation of load, etc.

Research of Laser Cladding of the Powder Materials for Die Repair

The study of laser cladding of powder materials (H13, A11 and M2) onto the tool steel 41Cr4 and C80U was conducted with the aim to establish the influence of overlap ratio, scanning speed and powder feed rate as well as appliance of post-heat treatment on the coating quality and mechanical properties. The highest hardness was achieved for A11 and M2 cladding materials, lowest coefficient of friction – for H13 and M2 coatings. It could be recommended to apply the laser cladding at larger percentage of overlap (50%).

Titanium Compound Erosion-Resistant Nano-Coatings

The main objective of this paper is to offer ion-plasma technology for production of Ti (titanium) and titanium nitride (TiN) erosion-resistant nanocoatings for the machine building products, which ensures the coatings with optimum and stable properties. As a result of experiments and processing experimental data the optimum composition of ion-plasma titanium and titanium nitride nanocoatings was obtained and offered.The approbation of the developed technology on the existing machine building products (compressor blade of the helicopter gas turbine; base material: Incoloy 800) was carried out. The comparative study on the influence of the coating on the surface quality, coefficient of friction, adhesion strength and erosion resistance was done. For evaluation of the obtained nanocoating surface’s quality 2D and 3D surface description approaches were applied. Achieved results prove the effectiveness of offered ion-plasma technology for production of titanium and titanium nitride erosion-resistant nanocoatings with appropriate and stable properties.

New Composite Materials Based on Intermetallics for Protection Details of Hydropower Equipment from Cavitation, Hydroabrasive and Corrosion Wear

The corrosion behavior in seawater of NiAl and NiTi intermetallics and composites based on them has been studied in this paper. It was shown that the developed composite NiTi-30 wt.% CrB2 hardly corrodes. The developed materials are meant for protect different shipbuilding details and details of hydropower equipment from aggressive sea water environments, as well as against hydro-abrasive and cavitation wear.

The Application of the Pulsed Electromagnetic Field for Joining Powder Parts

The paper is devoted to the permanent joining of powder parts by the pulsed electromagnetic field. The possibility of such joining was proved experimentally and testing the obtained samples. The method of permanent joining of powder parts employing technologies of the pulsed electromagnetic field is the most effective for joining powder parts with relatively high copper content (more than 10%) and when the thickness of powder parts is in the range from 2 to 10 mm. Using a concentrator of the electromagnetic field allows increasing pressure in a relatively small zone up to 2...3 times, which significantly increases the deformation of the material of joined parts and, consequently, the reliability of joints.

Influence of Material Internal Stresses to the Coefficient of Friction

The aim of this paper is to calculate and compare both tangential and normal internal stresses in contacting area of two spherical bodies in contact. The results of these calculations have a practical use in further research of coefficient of friction in relation to the surface roughness asperities of contacting bodies.

Application of Pulse Electromagnetic Field for Metal Coatings Manufacturing

In current article, applications of pulsed electromagnetic fields (PEMF) for processing of powder parts obtaining bronze coating on a steel rod are presented. Experiments were carried out in Laboratory of Metal Forming Technology (University of Applied Sciences of Zwickau, Germany) and in Laboratory of Powder Materials (Riga Technical University, Latvia). An adhesion strength between steel and bronze parts was measured by means of a shearing test.