The subject of the paper is a study of the material behavior during hot rolling. The process considered is a rolling of round bar in roughing mill group which consist of four passes. The computer simulation of the process shows that the local plastic deformations which appear in the material are extremely large. This fact can leads to extension of surface defects. The dependences of maximum local plastic deformation on geometrical parameters of the calibers have been obtained and analyzed during this study. The investigations performed, led to the development of new roll pass design which almost halved the maximum value of local plastic deformation in the material during the rolling. Since full 3D FEM models needs significant amount of computer memory and CPU time, it was not suitable for the performed study which involves a bulk of simulations with different initial conditions. Therefore, the quick algorithms for simulation of rolling processes which based on so-called “2.5D” method have been used. This method, due to number of simplifications, is significant faster than conventional 3D FEM, and at the same time it allows to reach good accuracy of the model. The developed computer software SPLEN(Rolling) which implements “2.5D” FEM simulations was applied for computations and analysis of the results. This software is able to predict the shape evolution of rolled material, as well as distributions of strain, strain rate and temperature within the volume of deformation zone. It has been shown that computer simulation based on “2.5D” FEM with SPLEN(Rolling) software can be efficiently used for optimization of technological procedures in rolling industry.
Determination of material constants describing its behavior during superplastic gas forming is the main subject of this study. The main feature of free bulging tests is the stress-strain conditions which are very similar to ones occurring in the most of gas forming processes. On the other hand, the interpretation of the results of such tests is a complicated procedure. The paper presents a simple technique for the characterization of materials superplasticity by free bulging tests, which is based on inverse analysis. The main idea of this technique is a semianalytical solution of the direct problem instead of finite element simulation which allows one to reduce the calculation time significantly. At the same time the results this simplified solution are accurate enough to obtain realistic material constants.
Opal matrix is a regular 3D-packing of spherical particles of amorphous SiO2, forming an ordered system of voids. Opal matrixes with spherical particles of SiO2 diameter d ≈ 260 nm (Δd ≈ 2 %) were synthesized. The frequency dependences of the conductivity, real and imaginary components of the dielectric and magnetic conductivity of nanocomposites containing crystallites 16–65 nm in size of magnetic materials ‒ double phosphates (LiNiPO4, LiCoPO4) and vanadates (GdVO4 and DyVO4) were measured. The dielectric losses of nanocomposites remain low (at a level of ~ 0.06) in the frequency range 107–1010 Hz for nanocomposites with DyVO4 and LiCoPO4. The dielectric loss increases both in the direction of low frequencies (< 106 Hz) and in the direction of THz frequencies.
The regularities and features of physical processes (blistering, sputtering, radiation-induced segregation and radiation-intensified sublimation), occurring in surface-adjacent layers of aluminium alloys and austenitic steels under the action of the fluxes of accelerated charged ions and electrons are considered.
Superplastic forming has already been proven as a practical solution for manufacturing lightweight components in niche applications such as the aerospace and luxury cars industries. The demand to produce such components will continue with the limited nature of the energy resources available today. Therefore, superplastic materials are expected to stay as potential candidates in such applications. In addition, superplastic forming offers many unique advantages over conventional forming techniques including greater design flexibility, relatively low tooling cost, and no spring back. However, the full potential of the process has not yet been fulfilled due to concerns about the nonuniformity of the produced parts thickness profiles and the need for heating to achieve the superplastic properties of the material. In this paper the authors address the main challenges that hinder the wide spread of the process. It is of great practical importance, for example, to develop accurate simulations of the superplastic forming process. Such simulations are required for identifying the optimum process parameters for high quality components. The results of any such simulations or experimental investigations should be translated into simple and clear industrial guidelines. In addition, they discuss the current trends and the prospects of this process.
Numerical and physical simulation on model samples can provide data for various aspects of metal forming, without resorting to time-consuming and costly full-scale tests. This paper presents examples of modeling of the deformation of a slab with a liquid core. The use of soft reduction can enhance the homogeneity of the structure, which improves the quality of cast billets. Mathematical modeling is described here where the fluid layer is taken into account by the influence of boundary conditions in the crust in the form of ferrostatic pressure, which allows calculation of the intensity of deformation, total deformation and strain. It also provides a novel method for studying the process of soft reduction. It is based on a physical model of the slab consisting of a closed solid shell made of a calibrated lead shot and the Wood's alloy. To simulate the liquid molten metal, the interior of the shell is filled with gelatin. This approach can be applied to further studies on deformation processes and the penetration of deformation into complex metallic systems.
It has been shown that the sputtering stability of Al-Li alloys under bombardment by 0,5 keV neon ions was 3 times higher than that of Al.
An abnormal sputtering stability has been found under bombardment of the Al-Li and Al-Be alloys by 0.5 keV neon ions.
This paper presents the research of the flow characteristics of the Ti-6V-4Al alloy in wide ranges of temperature (725 ‑ 950 °C) and strain rate (10-5 ‑ 10-2 s-1). The material processing maps were constructed based on the basis of dynamic materials model (DMM) developed by Prassad and modified by Narayana Murty. For the construction of such maps the data of the material’s flow stress at different temperatures and strain rates is necessary. To obtain such data the stepped tensile tests which allow get the stress - strain rate dependence at a given temperature are ideal. The experiments conducted consist of the tensile-testing of samples’ series at various temperatures with stepped change of the deformation speed. By the results of these tests the constitutive equations, which describe relationship between stress and strain rate for each temperature were obtained. The data was analyzed in terms of the two different approaches proposed by Prassad and Narayana Murty to assess the impact of deformation conditions on the formability and flow stability of the material. Based on these approaches, the processing maps which allow identifying the conditions of the Ti-6V-4Al alloy superplasticity were constructed.