No 4 (2014)
- Year: 2014
- Articles: 11
- URL: https://journal-vniispk.ru/1994-6309/issue/view/19985
- Description:
Full Issue
TECHNOLOGY
Process control of chip formation during plastic material processing
Abstract
The process of chip formation and possible ways of its control during plastic material processing is considered. The dependence of the chips type on the cutting conditions is determined. Processing of some plastic materials such as fiberglass is accompanied by several problems: the tendency to form burns and peeling of the material; heterogeneity of the structure; strong abrasive effect on the tool; reduced thermal conductivity; difficulty in applying lubricating substances. Chip formation process in this case is very important to ensure the quality of the manufactured products, the smooth operation of the equipment and, as a result, increase in efficiency, security of workers. These studies have determined the type of chips from the cutting conditions. Nomograms, reflecting areas that preclude the emergence of the flow chips and ingress of discontinuous and dusty chip into the air are obtained. It is showed that when creating a model of the process of chip formation it is necessary to consider the above-mentioned features of plastic materials processing and solve the problem of designing systems with complex geometric configuration and irregular physical structure.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):6-10
6-10
Structure of wear resistant plasma coatings after high-energy treatment using high-frequency currents
Abstract
Purpose: In order to ensure the required level of wear resistance of high-chromium cast iron powder plasma coatings, research on the effect of high-energy heating by high frequency currents (HEH HFC) on the quality of the surface layer is conducted. Methods: The results of metallographic, X-ray diffraction and energy-dispersive studies of the structure of wear-resistant plasma coatings before and after the induction heating are presented. Results and Discussion: Pores, unmelted powder particles and discontinuities in the transitional boundary, as well as improved uniformity of the microhardness in the depth the layer have virtually disappeared after additional high-temperature influence. After plasma spraying the value of the microhardness confidence interval was 1.7 … 2.8 GPa; after HEH HFC - microhardness confidence interval ranged between 0.5 and 1.3 GPa. In the structure of plasma coatings carbide component is preserved in the selected area of induction heating modes. An efficient mode of HFC reheating (source specific power q = (3,0 ... 3,2) ∙ 108 W/m2, the relative rate of details movement V = 60 ... 80 mm/s) at which there is a decrease in porosity of the plasma coating from 12 % to 1% is set.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):11-18
11-18
EQUIPMENT. INSTRUMENTS
Ensuring the geometric accuracy of shell during assembly of Geohod sections
Abstract
The article shows the way to ensure the geometric accuracy of large segmented-ring structures, for example sections of Geohod. The method of installation, consisting in location of the sector by the shell surface on a fixed support therewith the shells of individual sectors approximate shell section as a whole, is offered. Mathematical expressions of deviation profile of the sector with the real sector size and distances, which define a position of the supports, are received. The factors affecting geometric accuracy of the shell section and the impact of these factors on the accuracy are examined. Problem of determination of the maximum deviation of the profile of the sector, depending on the tolerance of the sector size and distance, establishing the position of the supports, is set. The dependences of the maximum values of the deviation of the sector profile on the of the tolerance levels are gotten. It is shown that the proposed scheme can be installed to provide higher accuracy of the shell section, than that which has a separate sector.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):19-28
19-28
Improving the wear resistance of the drilling carbide tools
Abstract
Creating a rock cutting tool with high performance is a burning problem and its solution will be a significant reserve of the further rise in the efficiency of drilling. The method of combined magnetic-pulse treatment including preheating and effects of pulsed magnetic field to improve the wear resistance of drilling tools carbide type VK8 is proposed. Wear resistance of the samples are evaluated on the equipment for erosion testing according to ASTM G76-07 «Standard Test Method for Conducting Erosion Tests by Solid Particle Impingement Using Gas Jets». The results of experimental investigations show that the preheating temperature of 1000 °C, the magnetic induction of 1.8 T and a pulse influence time 7∙10-4 s of the wear treated samples are 2.5 times less than the untreated control samples. The proposed method of processing carbide tools is promising for mining industry. In future research on the application of the combined magnetic-pulse treatment of drilling carbide tools will be expanded.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):29-35
29-35
MATERIAL SCIENCE
Research of the structure and properties of the hard alloy VK10KS after hardening in waterpolymeric liquid Termovit M
Abstract
The results of research of WC-Co hard alloy VK10KS after hardening from 1150 °С in waterpolymeric liquid Termovit M with concentration of 4 % under the temperature of 40 °С are considered. The changes in the structure of the alloy which are connected with the partial solution of WC during heating before hardening and, therefore, reducing its sizes from 5...8 in the initial state up to 2…4 after heat treatment are discovered. The solution of WC leads to the additional alloying of Co phase by C and W. In the initial samples in sintered state the average amount of dissolved tungsten is 10.89 %, but after hardening its concentration is increased up to 20.18 %. All above mentioned changes in the structure of the hard alloy after hardening lead to the increase of its modulus of rupture in bending up to 10 %, and decrease the area of friction up to 35 % in comparison with the sintered state when tribologic testing was conducted.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):36-42
36-42
The contact endurance of NiCrBSi coatings obtained by gas powder laser cladding
Abstract
The contact endurance of NiCrBSi coatings obtained by gas powder laser cladding of the powders with various chrome, carbon and boron content (PG-SR2, wt. %: 14.8 Сr – 2.1 В – 0.48 С; PG-10N-01, wt. %: 18.2 Cr – 3.3 В – 0.92 С) and TiC addition (PG-SR2 + 25 wt. % TiC) is investigated. The average microhardness was 520 HV for PG-SR coating, 720 HV for PG-10N-01 coating and 770 HV for TiC – PG-SR2 coating. Tests on the contact fatigue are carried out using a servohydraulic testing machine (Instron 8801) circuit-wise pulsating non-impact contact «ball-plane» scheme with the load variation during a cycle according to a sinusoidal law. The maximum resistance to a contact impact during repetitive elastic-plastic deformation on mechanical non-impact contact loading is determined for PG-10N-01 coating with increased chrome, carbon and boron content in comparison with PG-SP2, the minimal one was for composite PG-SR2 coating with addition 25 wt. % TiC particles. The examination of the contact spots using scanning electron microscopy shows that the main fracture mechanism of every investigated coating under contact fatigue loading is cracking.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):43-51
43-51
ТРУДЫ КОНФЕРЕНЦИИ
Numerical simulation of gas turbine engines fan blades emergency breakage
Abstract
One of the criteria for evaluating the reliability of the aviation gas turbine engine housing is their ability to retain broken elements of the rotors and, primarily, the fan blades. The paper presents the results of numerical simulation of deformation and fracture of the aviation gas turbine engine housing after a high-speed collision with a fan blade at its emergency breakage. Parameters of Johnson-Cook model, describing the behavior of alloys VT6, OT4 and OT4-0, is verified. Comparison with experimental data showed a good agreement for the flying residual velocity of the broken blade and forms of punched holes. It is shown that depending on the housing material, its thickness and blade breakage velocity, there is a possibility of penetration of the housing by a broken blade and its departure beyond or localization of the broken blade inside the housing.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):52-60
52-60
Evaluation of the composite materials structural condition during fracture
Abstract
The fracture kinetics of the unidirectional fiberglass under cyclic lateral deflection is studied. During fracture process the composite structural state is determined by the changes in its rigidity and inelasticity. Changes in rigidity indicate the breakages both on the stage of the composite layering, and during a break of the fibers. Amplitude dependence of the inelasticity is related to the distribution of internal stresses in the material volume. It characterizes the state of the material structure as the breakages advances. Changes in these characteristics give opportunity to make a conclusion about the stages of the composite fracture process and predictability of its durability.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):61-67
61-67
Calculation of plates made of strain-hardening material with different resistance to tension and compression under creep
Abstract
Samples cut from AK4-1T alloy plates with thickness h = 45 mm are experimentally investigated at T = 195 ºС under tension and compression conditions. The alloy is strain-hardening and has different resistance to tension and compression under creep. Constants for power-law dependences describing creep strain rates are defined according to the experimental data. The model based on the “transformed” space of stresses, taking into account properties of hardening and different resistance of material to tension and compression at creep is developed. The model is tested for the problem of AK4-1T alloy plates’; pure torsion in assuming of planes stress-strain state. Experimental data on flexible plates’; torsion and finite elements’; calculation in geometrically nonlinear statement using constants only on tension or compression are presented. Experimental values are located between the relevant calculated lines, that confirms the complex properties of alloy. These properties should be taken into account in the calculations.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):68-77
68-77
Influence of range of compositions elements characteristics on the effective thermal expansion coefficients for microheterogeneous materials
Abstract
The approach for the numerical analysis of the averaged thermal expansion coefficients of multiphase composites based on the method of statistical testing is proposed. This approach allows to take into account the stochastic nature of the composite. The influence of the variation of physical and mathematical characteristics of the substructural elements: Young modulus, Poisson ratios and linear thermal expansion coefficients is investigated. The mathematical model of the composite is based on the principle of effective homogeneity, structural analysis and correctly formulated interference conditions (for deformation, stress and temperature) at the interphase boundary. The numerical results are presented for the effective coefficients of linear thermal expansion of the composite for various structures of three-phase environments. The confidence intervals with given confidence probability for various structures are found. The influence of the stochastic nature of various characteristics of substructural elements on mathematical expectation of thermal expansion coefficients of the composite is estimated.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):78-84
78-84
The shaping by bending of elements aircraft structures at plasticity conditions
Abstract
The problem of inverse elastic-plastic calculation of predictive snap on the base of residual contour of the detail is solved with taking into account the elastic recovery after load removal for technology of shaping of large-sized finned panels. The form of the detail corresponds to a complex surface of double curvature with zones of convexity and concavity. Panel reinforcement ribs are under tension, compression and torsion during shaping. Preliminary test calculations of elastic-plastic bending at a temperature of 195 ºС of the t-shaped cross-section samples of alloy AK4-1T cut from the plate with the thickness h = 42mm showed satisfactory compliance to the experimental data. Such samples bending is simulation of the deformation of the stiffener with attached aircraft skin. An iterative method of calculation using finite element package ANSYS allowed to get close enough to practice form of detail surface, which can be considered as an initial approximation for developing the technology of shaping process in real conditions.
Obrabotka Metallov / Metal Working and Material Science. 2014;(4):85-93
85-93