Alexey Anatolievich Kruglov

• PhD
• PhD at Institute for Metals Superplasticity Problems of Russian Academy of Sciences

The paper proposes a method for calculating the rheological parameters included in the standard power ratio of superplasticity based on the results of test forming of hemispheres using a cylindrical matrix. The method takes into account the value of the entry radius of the matrix. The analytical model of the process is developed based on the main a...

The results of studies on the mechanical behavior of a Ti-6Al-4V laminated material obtained by diffusion welding are analyzed. It is shown that the impact behavior of the layered material depends on many factors including the interface defects, the orientation of the notch tip relative to interface, the number and microstructural state of the laye...

By finite-element modeling the process of forming a rectangular welded sheet package with gas under pressure was studied. It is found, that when a cylindrical dome is formed, the width of the package firstly decreases, and when it reaches the diameter of the shell, it begins to increase, i.e., the cylindrical shell deforms almost without thinning....

Superplastic forming of a three-sheet structure is considered. The focus is on overcoming the main disadvantages of the process of manufacturing of such structures by means of the SPF/DB technique including high temperatures of treatment and the formation of folds on the outer surface of the article manufactured. The application of ultrafine-graine...

A novel procedure to determine the values of the material constants K and m for the standard power superplastic law from the results of the bulge tests of the hemispheres is suggested. Unlike other approaches known in the literature.the involved procedure requires only two experimental measurements of the time of formingunder constant pressure, wit...

Corrugated core panels manufactured by methods of superplastic forming concurrent with diffusion bonding (SPF/ DB) are promising for the production of high specific strength articles. One of serious problems arising in forming of corrugated core panels is concerned with the formation of outer folds. The cause of folding is uneven deformation of the...

A general scheme for identifying the constitutive equations of superplasticity, according to which the values of material constants are calculated by the results of technological experiments using interpretation techniques based on the adoption of additional hypotheses of the stress-strain state nature in the deformation region, is proposed. The ve...

The problem to determine experimentally the values of material parameters for two material models of superplastic flow, σ=Kξm and σ = K′ξm′εⁿ, from the results of technological trials is considered. With this in view, a special computational procedure is developed to minimize the deviation of the theoretically predicted forming times from experimen...

The process of pressure welding branch pipes with hot local heating and the ratio for calculating the conditions are proposed. The constitutive equations of the material in plasticity and creep are used. The energy method is used for calculating the pressure for the fracture axisymmetric field of the displacement speeds. The experimental and produc...

The boundary problem in the mechanics of superplasticity is formulated on the basis of a standard superplasticity power law and the Perzyna viscoplasticity model. Methods of identifying these models on the basis of the same input data are proposed.

The methods for calculating the duration of the superplastic forming of a circular membrane are considered. The results of calculations by analytical formulas are compared with the solution of boundary-value problems of the theory of creep and viscoplasticity found in the medium of the ANSYS software complex. The values of material constants were d...

A method is proposed which allows one to search for a solution to inverse problems of identifying constitutive relations from the results of technological experiments. The method uses simplified mathematical models of technological plastic metal forming processes based on the membrane theory of shells, which allows for calculations of material cons...

Application of the conventional superplasticity (SP) allows producing the unique hollow structures. One remarkable example is the hollow titanium blade of the air engine fan produced by Rolls-Royce. However, high temperature titanium alloys processing (~ 927 °С) limits wide industrial application of the conventional SP. The solution of the mentione...

The deformation mode of a titanium-alloy three-sheet structure consisting of a corrugated filler placed between two protection sheets is considered for the case of the linear pressure-supply law of the inert gas entering the region between the filler and protection sheets. A simplified process mode based on the use of the thin-shell theory is prese...

The paper studies the phase composition, microstructure, and mechanisms of plastic deformation and fracture under impact load in a laminate obtained by pressure welding of VT6 titanium alloy sheets. Under impact loading at 20 and -196°C, the material is delaminated into sheet piles with attendant changes in their fracture rate. At fracture surfaces...

There was considered regime of forming for sandwich construction from titanium alloy that represents corrugated filling, inserted between two shell plates, by means of linear law of neutral gas supply. This gas entered in the area between filling and shells. There was offered simple model of process, based on the use of torque-free shell theory. Th...

Superplastic forming of the rectangular edge welded envelope consisting of two rectangular sheets welded along their periphery is considered. The diameter of the cylindrical shell manufactured turns out to be considerably less as compared with the initial width of the rectangular edge welded envelope to be formed superplastically. The deforming of...

Application of the conventional superplasticity (SP) allows producing the unique hollow structures. One remarkable example is the hollow titanium blade of the air engine fan produced by Rolls-Royce. However, high temperature of Ti-6Al-4V titanium alloy processing (~ 927 °С) limits wide industrial application of the conventional SP. On the base of e...

Ways of increasing the structural strength of spherical pressurized containers made of titanium alloy are described. The author suggests using the technological scheme of pressure welding/superplastic forming for production of full-strength containers. It has been shown that the principle of multilayer and ultra-fine-grain rolled sheet can be used...

Uniaxial tension and superplastic forming experiments are performed with ultra fine grained titanium VT6 alloy under conditions of low temperature superplasticity at temperatures 600 and 650оС. The initial mean grain size in ultra fine grained titanium VT6 alloy was 0,2 μm. Pores were not display at the steady superplastic state up to 600% of sampl...

Two multilayer materials based on Ti-6Al-4V alloy have been processed by diffusion bonding at two different temperatures [1023 K and 1173 K (750 °C and 900 °C)]. The influence of the processing temperature on microstructure, texture, and mechanical properties of the two multilayer materials has been analyzed. Scanning electron microscopy, X-ray dif...

Microstructure and mechanical properties, with emphasis in impact toughness behaviour, of two multilayer composites have been investigated. The multilayer materials are constituted by thirteen layers of high strength Ti–6 Al–4 V alloy. Stacked layers have been successfully joined by diffusion bonding considering two processing temperatures, 750 and...

The superplastic forming process of the VT6 titanium alloy three‐layered hollow structures with goffered filler are investigated. Based on the results of experimental studies and on the results of finite element modeling, we determine rational parameters of the process such as gas pressure increase rate, when superplastic flow condition is satisfie...

We compare the mechanical behavior of samples under shock loading made of VT6 titanium alloy with different structures: coarse-crystalline (CC) structure with lamellar morphology of phases, microcrystalline (MC) structure with globular morphology of phases, and nanostructure (NS). The test results show that the alloys with CC and MC structures have...

The mechanical behavior of pressure-welded VT6 titanium alloy sheets under shock loading was studied. It is shown that the impact strength of its layered material depends on both the location of its joint surfaces relative to a propagating crack and the relative extent of pores in the zone of solid-phase joints. If pores are present in the material...

Two alternative production flowcharts for the fabrication of cylindrical shells from titanium alloys in the superplasticity (SP) state, namely, the formation of the sheet into a rectangular matrix and the free formation of a package consisting of two sheets welded along a rectangular contour by diffusion welding, are considered. It is stated by com...

Layered semiproducts produced by pressure welding of sheet workpieces of a VT6 titanium alloy are studied. Possible methods of achieving isotropic mechanical properties of the semiproducts are discussed. The pores that are present in solid-phase joint zones are found not to influence the impact toughness of the samples in which layers lie perpendic...

Creation of new improved faces for wood golf clubs is impossible without providing such advantages as decreased shock experienced at impact, elevated stored energy from the club head to the ball at impact for increasing ball distance and more efficient usage of the face material having the required strength. The paper presents a new structure of go...

Titanium alloy Ti-6AI-4V is used to manufacture the layered material by means of diffusion bonding techniques. The layered material consists of sheets with nano-and microcrystalline structures. The layered material is investigated by conducting the mechanical tests and metallographic studies. The possibility to achieve isotropy in mechanical proper...

A critical analysis of approaches to find constitutive relations from the tests on uniaxial and two axial loading is presented. Then we report on the methodology of fitting parameters of constitutive relations for superplastic forming based on the results of cone cup and elongated wedge cup tests. Optimal cone and wedge angles are estimated analyti...

The principles of fabricating nanostructured bulk and sheet materials by the methods of multiple isothermal forging and warm rolling are formulated. The first method, which is based on dynamic recrystallization, allows one to obtain bulk materials with a uniform nanostructure. The second method makes it possible to transform the latter into a sheet...

This paper reports the results of experiments on superplastic forming (SPF) and pressure welding (PW) performed with sheets of nano- and submicro-crystalline Ti–6Al–4V alloy. The decrease in the mean grain size of Ti–6Al–4V alloy sheets from 0.4 to 0.2μm allows the decrease of the SPF temperature from 750 to 600°C and the fabrication of cylindrical...

The results of the application of nanostructured titanium alloys, in particular the VT6 alloy, for the manufacture of hollow structures by superplastic forming and by a method combining it with pressure welding, are presented. Possibilities of the application of nanostructured titanium alloys are shown by the example of the formation of dome-shaped...

There are given the results of manufacturing spherical vessels by superplastic shaping from semi-finished products obtained with the help of pressure welding under superplasticity from set billets of the titanium alloy VT6. A new technological scheme is suggested that provides obtaining the equal-strength and structure-homogeneous spherical vessels...

There are considered the features of manufacturing spherical vessels with lugs by superplastic forming (SPF) from the half-finished items produced by welding under pressure (PW). Stress-strain state in the item under forming has been analyzed by means of computer simulation. The results of mechanical tests showing that application of PW-SPF scheme...

The mathematical modeling results are given on the behavior of hollow fan blades from sheet titanium alloys under the conditions of the distributed load on casing, the longitudinal bending and torsion. The promising constructions of the cell, corrugation and truss types of the hollow blade fin are described by the casing elements of the finite-elem...

Superplastic free forming of edge welded titanium envelopes is investigated theoretically and experimentally. The envelope is transformed into a spherical shell without clamping of its edges so that the final diameter of the spherical shell, Ds, produced is less than the initial diameter of the envelope, D0. Mathematical modelling of the process un...

The possibility of manufacturing regular shape vessels without equatorial flange was shown on the base of numerical and experimental studies of the process of superplastic forming (SPF) spherical vessels out of flat preforms produced by pressure welding of sheets. It was established the relationship between radii R and r of outer and inner lateral...

A new engineering model for the superplastic forming of domes has been developed. Unlike the well-known Jovane's model [1], it allows one to predict the thickness distribution of the domes. The approach involved permits the calculation of the pressure-time cycle and the thickness distribution without complicated numerical calculations. The superpla...

The analysis of free superplastic forming of spherical vessels from sheet envelopes is given. The finite element method (FEM) is used to simulate the process and good correlation between numerical results and an experiment is obtained. It has been established that the free forming of sheet envelopes is accompanied by a considerable movement of the...

Solution of the problem of spherical vessels forming of sheet semiproducts in a form of a package in a free state has been considered. The material behaviour was considered as nonlinear viscous-plastic one. The axial-symmetric problem formulation is discussed. Its numerical solution has been obtained using the final elements method. the effect of s...

Advantages and disadvantages are discussed for forming special control facilities. They are classified under three conventional groups: mechanical, electric and pneumatic. The latter facilities show the best performance. They are used to estimate the billet geometry and the rate of its deformation in terms of the volume of gas displaced using a mic...

Personal computer oriented method has been developed to calculate a free forming process in superplasticity schedule for spherical shells made from flat sheet blanks. The use of the method revealed specific features of free checked forming, determined process parameters. The results of modelling were tested in the fabrication of Ti-alloy (VT-6S) sh...