No 1 (2014)
- Year: 2014
- Articles: 10
- URL: https://journal-vniispk.ru/1994-6309/issue/view/19982
- Description:
Full Issue
EQUIPMENT. INSTRUMENTS
Decomposition method in design of multifunctional machines
Abstract
The main purpose of designing of supporting constructions of heavy multifunctional machines is the reduction of mass at the given precision and productivity of working. To achieve this objective, the technology of rational design of supporting constructions offered by us uses the decomposition method and the finite elements method in combination with optimization methods. The technology has four stages: 1) calculation (computation) of external all forces and loads, 2) as a result of the boundary conditions (force, kinematics) for individual supporting constructions are formed, 3) the problem of the final optimal distribution of a material by the individual supporting constructions with the real cross-section is solved; 4) dynamic analysis. Due to the large-scale computational model of the machine bearing system, consisting of a consistent set of interconnected basic details, on a design stage it is proposed to use the substructure, derived from the basic details. On the example of designing heavy machining center column it is shown that the application of the substructure significantly reduces the dimensionality of the model and the time of an actual design of the base detail. Strain field of the optimal column substructure is consistent with the strain field of columns, which is obtained when calculating the machine carrying system, consisting of basic details of a simplified column while coming up to the precision standards of machining. The turning angle of the optimal column with real cross-section is less than the column as part of the support system with simplified geometry for basic items - 0.0778 rad and 0.1495 rad, respectively, i.e. torsional stiffness of the optimal column is higher.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):61-68
61-68
Numerical-experimental study of the strength of constructional elements, made of carbon laminate
Abstract
Experimental results on the strength of CFRP laminate samples with stress concentrators of cylindrical hole- and counterformed hole-type are presented. Photographs of the samples after testing either with stress concentrators or smooth specimen with typical laminate stacking are showed. The rate of the strength reduction, obtained by means of experiments, and depending on the concentrators’; type and the material of a sample, is presented in a tabular form. Along with the experiment, a numerical evaluation of the samples’; strength with the usage of a gradient criterion (the case of compression) and Nuizmer criterion for stress in a point (the case of stretching) is conducted. Similarly, the rate of the strength reduction, obtained with the usage of criteria, are presented in a tabular form. Based on the comparison of the results obtained by numerical and experimental way, the parameters of the Nuizmer criterion corresponding to the experimental samples’; rupture stresses are offered. Guidance on the application of the considered criteria of the strength assessment to the layered composites under examination, depending on the type of stress concentrator is provided.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):69-75
69-75
Improvement of the design of the steel-making electric-arc furnace ДСП-40-Н1
Abstract
Stress calculation of the main structural elements of the steel-making electric-arc furnace ДСП-40-Н1 is considered. Static deformation of spatial design of the furnace is modeled using the finite element method in the ANSYS program pack. To reduce the computation effort a model of massive construction is recruited from the plates (shell finite elements are used). Stress calculation of the furnace structural members most subjected to load is conducted. It is revealed that in the original version of the construction there are stresses that are several times higher than the yield stress of the material, prescribed in the GOST for sheet metal that makes up the construction. On the basis of the distribution of stresses in the finite element model several options to strengthen the construction were worked out and the most appropriate variant, that provided the required safety and ease of constructive implementation were selected. The construction of the proposed reinforcements successfully completed in-plant test limit loads. This will ensure further safe operation of the furnace.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):76-80
76-80
MATERIAL SCIENCE
Achievement the strength level of 2400-2500 MPa in the ХН3МФС-type steels with different carbon contents
Abstract
The possibility of obtaining high strength of about 2400-2500 MPa is studied on the samples of high-purity steels 45ХН3МФСА, 55ХН3МФСА and 65ХН3МФСА melted in a vacuum induction furnace. Research efforts suggests that it is not possible to receive high strength of the steel 45ХН3МФСА even after high-temperature thermomechanical treatment (HTMT). It is possible to receive the strength level of 2400-2500 MPa on the steels 55ХН3МФСА and 65ХН3МФСА after tempering at 150 and 200 oC each after quenching and HTMT. In this case the impact strength and plasticity steels after HTMT are at on quite a satisfactory level (δ = 9-13%, ψ = 28-42%, KCU = 0,40-0,46 MJ/m2). The study of the destruction mechanisms undertaken on the fractures of the impact samples showed that the reduction of impact strength of the samples after quenching and tempering at the temperatures in excess of 250 ° C is explained by activation of intergranular fracture, which is associated with the manifestation of irreversible temper brittleness. HTMT reduces the tendency of high-strength steels to irreversible temper brittleness, so after tempering at 300 ° C in the fractures of the samples subjected to HTMT facets of quasi-chip and pits are observed.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):6-13
6-13
Application of the method of laser-plasma surface modification of metals to improve tribological characteristics of combustion engines
Abstract
The results of the development of laser-plasma method for surface hardening of metals in two areas: high-performance surface modification of iron and synthesis of superhard (20 - 30 GPa ) nanocomposite coatings are presented. Laser- plasma method is based on pulsed optical plasma discharge. Repetitive discharge is ignited with a high repetition frequency (tens of kHz) by laser pulses at the focus of the CO2 laser beam. For the formation of the plasma in the processing head, high flow of gas: argon , nitrogen and oxygen is generated. Plasma gas flow in the plasma-chemical chamber has a speed of 500 m / s and pressure up to 0.5 MPa. For the synthesis of coatings a two-channel plasma chemical chamber additionally provides delivery of thealloying gas in the focus area of the laser.To improve the wear resistance of gray cast iron in friction couples by laser processing, a structure with high-hardness (12-20 GPa ) nanostructured surface layer and having thickness of 1 micron, which is adjacent to a layer with a thickness of about 100 microns with a locally hardened regions surrounding the graphite areas . The resulting structure of the surface reduces the coefficient of friction by 30% and twentyfold increase in wear resistance under conditions of hydrodynamic friction. This is due to the creation of micro-relief wear pairs , including capillary channels accumulating grease by location of graphite and solid constituents - ledeburite and martensite surrounding these microgroves.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):14-23
14-23
Economically alloyed steels with a strength level of 2200-2600 MPa
Abstract
The possibility of obtaining high-purity steels 65С2А and 65С2ВА melted in a vacuum induction furnace, with the level of strength of about 2500 MPa is studied. It is shown that without the use of special processing methods this level of strength can't be achieved. Using high-temperature thermomechanical treatment (HTMT) and treatment to ultrafine grain gives the opportunity to get tensile strength σB ≈ 2600 MPa, ψ = 20-35% and КСU= 0.25-0.4 MJ/m2. Upon alloying mild steel by carbide-forming elements (65С2А steel) the ductility КСU= 0.4 MJ/m2 is provided , but plasticity is relatively low ψ < 20%. Without the carbide-forming elements (65С2А steel) value of КСU is 0.25-0.30 MJ/m2, but the value of plasticity is ψ = 35-40%. Study of the fracture structure showed that due to HTMT the dimensions of the chipping surfaces are reduced, intergranular fracture sites are disappeared and the most important thing is that the area of the fracture occupied pits is increased. It can be assumed, that this is a consequence of the general dispersion structure in HTMT.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):24-31
24-31
The formation of the structure and mechanical properties of the structural steel during cold plastic deformation by radial forging
Abstract
The laws of formation of the structure and properties of structural steel 35X during cold plastic deformation by radial forging (RF) are discussed. Tubular billets were subjected to toughening before cold radial forging. Methods of metallographic analysis, transmission electron microscopy, a uniaxial tension tests with determination of the strength and ductility, as well as the impact tests КСU and КСТ were used in the work. Methods of statistical analysis were used to quantitative evaluation the size of the elements of the subgrain structure of steel 35X. The studies found out that the cold RF of steel 35X tubular billets causes structure fragmentation, dissolution of the carbide phase formed by toughening and development of dynamic recrystallization. In this case the average size of α-phase subgrains reduced from 1500 nm to 730 nm after the first pass of cold RF and there is a further refinement of subgrain structure of investigated steel to the size of subgrains α-phase, 640 and 525 nm, after a second and third pass, respectively. The deformation of the structural steel 35X with deformation ratio 55 % results in incensing of the offset yield strenght (σ0,2) by almost 50%, and the ultimate tensile strength (σB) – 25 %, compared with the initial condition after the toughening. In this case, the reliability behavior (δ, ψ, KCU, KCT) of tubular billets of structural steel 35X are reduced insignificantly and remained at a high level.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):32-38
32-38
The effect of structure dispersion on mechanical properties of low-carbon structural steel
Abstract
The relationship between the size of structural elements, the grain direction and the level of the strength and reliability of hardened low-carbon sheet steel 12Х2Г2НМФТ is investigated. Methods of metallographic analysis, transmission and scanning microscopy, a uniaxial tension tests and three-point bending impact were used. It is established that there is a deviation from the Hall-Petch relationship with the achievement of the nanocrystalline state of lath martensite in the steel under consideration. The dependence of fracture toughness (KCT) and the fracture structure on the struc-ture dispersion of the steel under consideration is largely determined by the by the fiber direction with respect to the applied load. The grain direction relative to the applied load largely determines the dependence of the impact toughness (KCT) and the structure of the fracture on the dispersion of the structure of investigated steel. The impact toughness (KCT) began to increase with the dispersed austenite grain less than 40 microns on samples cut lengthwise to the rolling direction, at the same time the destruction took across the fiber in the tests. And the micromechanism of destruction varies from quasi-chip to tough in the preparation of nanostructured state with the size of the lath of 96 nm. In transverse samples dispersion of structure has almost no effect on the level of impact tough-ness (KCT), but the fibrous structure significantly influence the level of impact toughness (KCT).
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):39-45
39-45
Influence of a basic structure on the structure and properties of diffusion boride coatings
Abstract
It is found that the effect of base alloying elements on the chemical and phase composition of diffusion boride coatings is determined by its solubility in iron borides . Chrome which is well-soluble in FeB and Fe2B borides enhances the coating ability to deform plastically under dry friction. Insoluble in borides elements are pushed to the border with the base material, slowdown diffusion processes and forming a transition layer with dispersed borides of high-melting elements in the soft interlayer of siliceous ferrite. This structure of the coating provides a uniform distribution of the normal modulus of elasticity, increases the resistance of the protective layer in the thermal cycling conditions and linear wear.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):46-53
46-53
Structure of electroexplosive composite coatings, consisting of incompatible components of Cu-Mo-system, after electron-beam treatment
Abstract
Modification of the electroexplosive composite coatings by electron beam is the perspective direction in the development of methods of electroexplosive spattering of composite materials. In recent years the method of the surface treatment by the multiphase plasma jets of electrical conductors explosion has been developed. In this paper it is showed, that repetitively-pulsed electron-beam treatment of the electroexplosive coatings of the Cu-Mo-system leads to a smoothing of the coatings surface relief and formation of its’; two-layer structure. Surface layer with a thickness of 30-50 μm after electron-beam refusion is characterized by a defect-free structure and is formed by molybdenum cells with an average size of 1.3 μm, which is combined in grains with the size of 10-22 μm. Thickness of the copper layers in it is 0.1-0.2 μm. Molybdenum and copper content in it is 70 and 30 at. % respectively.
Obrabotka Metallov / Metal Working and Material Science. 2014;(1):54-60
54-60