No 4 (2015)
- Year: 2015
- Articles: 10
- URL: https://bakhtiniada.ru/1994-6309/issue/view/19981
- Description:
Full Issue
TECHNOLOGY
Use of basic model of process of drilling for rationing of the modes of cutting of the hardly processed materials
Abstract
A method of cutting regimes normalization for hard-to-machine materials using the example of drilling operation is offered. The method is based on application of new models of tool life well consistent with the experiments results as well as on building characteristic lines and surfaces for the cutting process parameters. Applications of the suggested method allows using the mechanism of experimental tools lifetime for different zones of the cutting regimes factor space, which allows to decrease the number of labor-intensive AW experiments, improve accuracy of calculations of optimal processing conditions and graphic display of adopted resolutions. A scheduling algorithm for the experiment to estimate the selected resistibility model parameters is developed on the ground of the suggested method. On the basis of the suggested method a program complex is drawn up to calculate optimal drilling regimes on the criteria of minimal expenses for range diameters of drills (from 3 to 40 mm) and processed materials (with processing ratio of the material, PR, from 0,2 to 1). The basic variables of the cutting process include the dimensions of tools, the applied criteria of tool life, the type of cooling lubricant, the mode of drill fixation, the drill radius, blind or through bore, the material grade, the drill material, the drill type and others. The method allows calculating both local optimal cutting regimes on the criteria of minimal expenses and the table regimes along the characteristic line of maximal life for the current variables for the moment feeds without considering the processing expenses.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):6-17
6-17
EQUIPMENT. INSTRUMENTS
Select of abrasive wheels while pendular grinding of parts from titanium alloy VT22 by high roughness parameters
Abstract
At the present time, grinding of the titanium alloys parts is performed much less than other constructional materials that don’t meet the demands of branches of engineering industries: aircraft, rocket, energy and others. This is due to the sticking of chips on the working surface of the abrasive tools from silicon carbide and electrocorundum because of the high adhesion activity between the titanium and the traditional abrasives at cutting working temperatures. To solve this problem, the high porous wheels (HPW) made of cubic boron nitride CBN30 with 100% concentration on a bond V (K27), a pore-forming KF40, varied grains: B76, B126, B151 (GOST R 53922 - 2010) - and hardness: M and O (GOST R 52587 - 2006) were used to grind titanium workpieces. Additionally the Norton wheels from green silicon carbide with a normal porosity 39C (46; 60) K8 VK and with different grain size were tested. With account for the instability of the grinding process and the random nature of roughness formation, the observation analysis was led using the statistical approaches. It allowed considering the random variables (RV), the characteristics of the one-dimensional frequency distribution which are measures of position (mean, median) and measures of scattering (standard deviation, range and quartile latitudes (QL)). In the technical applications parametric and nonparametric statistical methods were used. The first direction requires that the RV have homoscedasticity and normal distribution that is not fully secured in this study. For this reason, the nonparametric method was selected priority. Its characteristics are medians and QL. It is established that varying the process variables for each group of instruments is insignificant by measures of position. Norton wheels provide reduction of roughness height 1.6 - 1.7 times in comparison with boron nitride HPW. These are recommended for the finishing grinding stage and HPW CBN30 - the preliminary to reduce the thermal effects on workpieces. By processing stability, the Norton wheels with grain 46 rank the first, and among boron nitride HPW - CBN30 B76 100 OV K27-KF40.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):18-30
18-30
Determining the error of location of geokhod stabilizing section sectors on the basis of coordinate measurement data
Abstract
The results of research factual accuracy of the shell stabilizing section of the geokhod prototype are presented. The paper contains an overview of a number of approaches to modeling the mechanisms of formation errors of the ring segmented items and determine its factual accuracy. The problem of experimental verification of the assumptions adopted in the simulation is posed. The study is performed on the basis of experimental data obtained by the coordinate measurement of the geokhod prototype. For the analysis of experimental data, the creation of mathematical models, its research, visualization data and reporting special software is developed. Data is analyzed by the method of mathematical simulation of the shell surface of the stabilizing section in whole and each sector. It is shown that, a significant portion of shell section geometric shape deviations (from 30,3 to 52,3 %) is due to errors in the location of sectors and errors of their radii. On the basis of the simulation absolute values of the respective errors and the actual values of dimensions and deviations are determined. The possibility of providing a given accuracy in the implementation of the shell surface assembly technology used in pilot production is confirmed. At the same time, the proximity of the actual values of the deviations to the limit values can lead to problems in ensuring the consistent quality of geokhod bodies in serial production. The correlation analysis of the data and statistical analysis of series of residuals of the developed models are made. Correlation analysis confirms the dependence of the deviations of the experimental points from their cylindrical coordinates, which confirms the importance of the location of the error sectors in deviations from the geometric precision shell. The results of the statistical analysis of series of models of residues shows that the error location and error sectors of their radii are not the only ones, are significant factors in shaping inaccuracies shell stabilizing section.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):31-42
31-42
Formation of the system of the local indicators to assess the quality of the cutting tool at the stage of technical training of production
Abstract
The technique of a comparative assessment of quality of designs of the cutting tools on a stage of technical training of production. Ten groups of the generalized indicators allowing making a complex comparative assessment of quality of a design of the tool had allocated. Each group of the generalized indicators of quality had presented by set of local criteria. Local criteria had expressed through the variation geometric, design, structural and operational parameters of the cutting tools. The system of the target functions allowing determining parameters of optimum constructions of cutting tools depending on the selected criteria an assessment had created. For a complex comparative assessment of quality of cutting tools the generalized target function in the form of an additive convolution of private criteria had created. As an example, local target functions for comparison purposes of constructions of built-up tooling and broaches had created. The technique is evident, universal and automated with use of the personal computer.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):43-50
43-50
Selection of form factors of machine carrying systems in reliance on the process duty
Abstract
Problems of dynamic behavior in load-carrying systems of technological machines under operational conditions are discussed. The goal of this study was to develop recommendations for selection of the fabric assortment for these machines (using an STB loom as an example). This study is urgent due to the lack of recommendations for selection of technological equipment and unified methods for account of the dynamic character of a technological force. The precision of the computational model for carrying systems, suggested by the authors earlier, is improved in this study by introducing additional elements required for operation of looms during production of the determined fabric assortment. The frequency spectrum of intrinsic vibrations of load-carrying systems for a series of STB looms with widths 180, 190, 220, 250 and 330 cm were determined more precisely using SolidWorks CAD system and finite-element CAE complex ANSYS. The first frequency varies in the range from 24.9 Hz (STB-180 loom) to 17.7 Hz (STB-330 loom), second frequency varies from 26.7 Hz to 20.8 Hz, and the third one varies from 54.8 Hz to 25.2 Hz. It is demonstrated that the technological loading from tension of warp fibers can be presented as loading from static force from preliminary tension of the mobile ram spring and dynamic component depending on operation of the machine mechanisms. It is also demonstrated that load-carrying systems of looms under certain operational conditions can approach resonance conditions. Movements of individual elements in load-carrying systems caused by technological loading presented by a Fourier series are determined. The obtained results make it possible to develop specific recommendations for discrimination of assortment ranges of STB looms in accordance with the requirements to hygiene and sanitary conditions during work on this equipment. During design of technological equipment, it is suggested to use technological loading in the form of a sinusoidal pulse with the period equal to turnaround time of the loom main shaft and amplitude equal to the static component of the acting force for chosen fabric assortment. Using the frequency spectrum of forced vibrations obtained by expansion of the technological loading in a Fourier series, it is suggested to develop constructions of load-carrying systems from the ratio between frequencies of forced and free vibrations equal to three or higher.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):51-60
51-60
MATERIAL SCIENCE
Welding of dissimilar materials with interlayers employment containing copper and tantalum
Abstract
Investigations of welded joints as well as strength properties of composites formed by explosive welding of plates from titanium alloy VT20 and stainless steel 09Cr18Ni10Ti with interlayer’s employment are conducted. The duty of interlayers are performed by the plates of tantalum or «brass - tantalum». It results in the suppression of brittle intermetallic phase’s formation in the joining zone and obtaining the welds characterized by lack of defects that reduce fracture strength of materials. By the means of a microstructural analysis it is found that in the bonding zone the copper and iron as well as titanium and tantalum based solid solutions are formed. By the means of a transmission electron microscopy the deformation twins are detected in some grains of melted zone between copper alloy and stainless steel. There is evidence that twinning is the predominant deformation mechanism of explosive welding process. At the welding interface of brass and tantalum plates the structure represents a mechanical mixture of copper and nano dispersive inclusions of β - tantalum. The level of layers joining strength is used as a criterion of mechanical properties of composite materials. The maximum ultimate strength 420 MPa is characteristic of composite materials with interlayers from brass and tantalum. The strength of composite materials with tantalum plate as interlayer is 22 % less than the composite with «brass - tantalum» interlayers. This reduction is probably due to the molten zones formation in the thin surfaces layers of plates between stainless steel and tantalum. During crystallization of these zones the low plastic tantalum and iron based chemical compounds were formed. Insertion of two layered «brass - tantalum» interlayer between stainless steel and titanium alloy is reasonable to increase the strength properties of composites.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):61-71
61-71
Wear resistance of hypereutectoid steel, alloy with copper and aluminum
Abstract
Structure, mechanical properties and wear resistance of hypereutectoid steels with 0.09... 8.97 wt. %. Cu is investigated. Addition of 3 wt. % Cu to the steel is accompanied by an increase in microhardness of pearlite from 380 to 430 HV. At the same time Brinell hardness increases from 340 to 390 HB. A further increase in the concentration of copper has no significant effect on the microhardness of pearlite and the Brinell hardness of the steel. Increasing copper content is the reason for the growth of lamellar pearlite microhardness. Three types of copper-based particles are detected. The first type particles have a size of about 20 nm and are arranged at ferrite intervals of pearlite. The particles of the second type have a size of ~ 1 μm and are arranged at a former grain boundaries of γ-Fe. The particles of the third type have a circular shape and size of ~ 25 μm. Wear resistance of hypereutectoid steel, containing 8.97 wt. % copper, is 3.5 times higher compared to bronze and ~ 23 % in comparison with antifriction cast iron when tested according to the scheme of sliding friction. Mainly, this is due to nanoparticles precipitated in pearlite the copper-based ε-phase. Relative wear resistance of hypereutectoid steel with addition of copper is almost 3 times higher than the durability of bronze in the friction conditions of fixed abrasive particles. The increase in wear resistance in sliding friction conditions, associated with a high content of copper, is due to increases in the volume fraction of cupric nanoparticles.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):72-79
72-79
Improving the tribological properties of austenitic 12Kh18N10T steel by nanostructuring frictional treatment
Abstract
Stainless austenitic chrome-nickel steels possess low strength properties, which are not improved by heat treatment. Surface hardening treatments through deformation (ultrasonic impact, shot peening etc.) often cannot provide high quality of the worked surface. Therefore, the primary task is to form and improve the methods of finishing treatments providing both effective deformation hardening and high quality surface of austenitic steels. It has great importance for precision parts of tribological components. The influence of frictional treatment by hemispheric synthetic diamond indenter on phase composition, structure, micromechanical and tribological characteristics of metastable austenitic 12Kh18N10T steel (in wt.%: 0,10 С; 17,72 Cr; 10,04 Ni; 0,63 Ti; 1,33 Mn; 0,57 Si; 0,227 Mo; 0,064 Co; 0,014 Nb; 0,057 Cu; 0,031 P; 0,014 S and Fe for balance) surface layers is studied. Roughness of the worked surface is studied through an optical profilometer. Methods of transmission electron microscopy and X-ray analysis are applied for investigation of steel structure and phase composition. Micromechanical properties are determined by measuring of microhardness by the recovered indentation method and using microindentation technique. Tribological properties (wear intensity and coefficient of friction) are determined upon sliding friction in the air conditions in the «steel 12Kh18N10T - steel 45 (0,45 wt. % of С; hardness is 50 HRC)» friction couple. It is established that frictional treatment of austenitic steel forms qualitative surface with low value of roughness parameter (Ra≈100 nm). At that, nanocrystalline and fragmented submicrocrystalline martensitic-austenitic structures in surface layer are arisen, high level of surface hardening (710 HV0.025) as well as essential decrease of wear rate and friction coefficient under conditions of dry sliding friction is achieved. The revealed leap of tribological properties of the austenitic steel at the initial stage of friction is connected with a limitation of seizure processes development on the nanostructured surface and a change of wear mode - from seizure to plastic edging. The use of kinetic microindentation method for analysis of increased resistance of nanostructured layer with martensitic-austenitic structure to plastic deformation under adhesive wear is justified.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):80-92
80-92
Influence of low dose γ-irradiation on the structural state of mechanically activated powder mixtures of Ti + Al
Abstract
The experimental research of the structural state of the powder components under the influence of γ-irradiation on the powder mixture Ti + Al, and the mixture of the same composition after preliminary mechanical activation treatment is carried out. Samples of selected powder mixtures were irradiated by γ-rays in small dose. To investigate the parameters of fine structure the method X-ray diffraction is used. The dependence between preliminary mechanical activation treatment of the powder mixture and its structural parameters also as the fine structure (size of coherent scattering regions, microstrain) after influence γ-irradiation is established. The influence γ-irradiation on the structural condition of mechanically activated mixture is different. From calculation of the fine structure of the two components in mechanically activated mixture follows that the applicable dose of γ-irradiation parameters affect the fine structure of components in different ways. For example, for Ti after γ-irradiation the value of crystal lattice significantly reduced ROC, and slightly increases the microstrains in the crystal lattice. It was found that preliminary mechanical activation treatment of the powder mixture Ti + Al is a stimulator for the radiation-induced state of the components even at low doses of γ-irradiation. In the sample of preliminary mechanical activation powder mixture, which was irradiated by γ-rays, are formed radiation-induced states of components, which is not observed in the sample of non-mechanical activation powder mixture. Increasing the value of microhardness of irradiated sample in comparison non-mechanical activation powder mixture, wherein the mechanical properties are correlated with the structural changes.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):93-101
93-101
Surface hardening alloy VT6 of electroexplosion alloying with boron carbide and by electron beam treatment
Abstract
Investigations aimed at identifying the changes in the surface layer of titanium alloy VT6 after combined treatment are carried out. Combined surface treatment of titanium alloy VT6 includes alloying with plasma formed during electrical explosion of titanium foil with a powder weight quantity of boron carbide and subsequent irradiation by high-intensity pulse electronic beam of sub millisecond exposure time. The titanium foil is used as exploded conductor during electroexplosive alloying. A weight quantity of boron carbide powder is placed into explosion area over the titanium foil. The laboratory electroexplosive device EVU 60/10 is used for EEA (electroexplosive alloying).The main parameters for a pulse liquid-phase alloying are set by the value of the charging voltage of the energy storage device of the accelerator, the diameter of the nozzle channel and the distance from its section to the sample. Subsequent thermal treatment of the titanium alloy VT6 surface layer is performed with high-intensity pulse electronic beam at the SOLO device (Institute of High Current Electronics SB RAS). The study found that electroexplosive alloying of the surface layer of titanium alloy VT6 samples leads to the formation of the highly developed relief. In the surface layer a heterogeneous distribution of alloying elements is observed through the methods of electron scanning microscopy. A significant difference in its concentration in the revealed layers leads to the difference in its strength and tribological properties. The subsequent electron beam treatment of the alloyed surface leads to its smoothing. The formation of the multilayer structure occurs and the distribution of alloying elements in the surface layer becomes more uniform. Analysis of the treated surface irradiated by the electron beam revealed the presence of two characteristic elements of the structure, formed in the result of the subsequent treatment with high-intensity pulse electron beam. The first structure element is acicular structure areas with the needle size of 1-10 microns. Studies of the transverse sections of the titanium alloy after combined treatment allowed to determine the thickness of the modified layer, which is not more than 30 μm. So, we can conclude that electroexplosive alloying and fast cooling at pulse treatment lead to the formation of a structure of submicro-nanoscale level that can improve the strength and tribological properties of the treated surface.
Obrabotka Metallov / Metal Working and Material Science. 2015;(4):102-112
102-112