Analysis of residual stress in circular cross-section wires after drawing process
Residual stresses arising in the drawing process have a significant impact on the quality of the cold-drawn wire. Knowledge of residual stresses and their distribution makes it possible to predict the behavior of metal products under operating loads and to prevent their possible destruction. In this regard, it is necessary to adjust the main parameters of the drawing process, including the geometry of the die channel. The work is devoted to the study of residual stresses arising from inhomogeneity of plastic deformation depending on the reduction value and the die angle. Computer simulation of wire drawing process by finite element method is performed. The distributions of residual stress tensor components along the wire radius are calculated for different values of reduction and die angle. The analysis of the obtained relations is carried out. The influence of the die angle on the distribution of residual stresses is most noticeable at small reductions. After the maximum values of residual stresses are reached at the reduction values of 35-40%, they noticeable decrease occurs.
The results concern roll pass design for rolling a round bar of a 20mm diameter from a 55mm diameter input. Concerning materials, this roll pass design must cover a wide range of steels, from low-carbon micro-alloyed steels to stainless steels. The roll pass design proposal takes into consideration lower plasticity of certain steels. The comparison was enabled by suggesting two roll pass designs. The classical oval-round roll pass design, where the maximum extension coefficient is set to 1.55 in oval and 1.22 in round grooves. The second roll pass design uses a combination of smooth part of the roll (curves) and round roll passes. Distribution of the extension coefficient in individual passes is similar to that of oval-round series. The paper also compares values of energy-force parameters calculated analytically using the method of finite elements. If we compare the distribution of temperature, stress and size of the grain, it is proved that the oval-round roll pass designs are the best as far as the balanced distribution of the above-mentioned values is concerned. The roll pas design combining smooth part of the roll with a round part does not achieve such balance. However, its advantage lies in far lower requirement for the needed length of the working part of the roll. Five passes are carried out on the smooth part of the roll, which considerably cuts down the required length of the roll body. Therefore it is this variant that will be used in the laboratory of wire rolling created within the project RMSTC.
The paper deals with an investigation of relief formation in Europa's surface. Jupiter's satellite Europa is close in size to the Moon. Its surface is covered with a layer of ice crust of thickness 10-30 km. Europa's surface is of large interest, because under the ice crust there is an ocean of liquid water creating conditions for possible life. The entire ice surface of the satellite is covered with a system of bands, valleys, and ridges. These structures are explained by the fact, that the ice surface is rather mobile and it was repeatedly broken from internal stresses and large-scale tectonic processes. The analysis performed showed that compressing, extending, shearing and bending stresses can influence some arbitrarily separated section of Europe's ice surface. The computer simulation with a finite element method (FEM) was performed to see, what types of defects could arise from such effects. The heterogeneity of the satellite's ice cover in thickness, density and temperature was taking into account during the simulation. The calculations, carried out for the cross-section of a thawed ice structure's area, have shown that, the most dangerous, from the crack formation viewpoint, is the shear stress at loading application angles of ±90°. Using models of thawed ice patches in the distributed field of temperatures, the effect of mechanical gravitation-tidal forces on the formation of surface defects on Europa was studied. It is shown that fractures and cracks can have various forms depending on the stress-strained state arising in their vicinity. The formation of such defects is caused by the chaotic set of many factors, mechanic and temperature ones predominantly. Copyright © 2013 by the International Astronautical Federation. All rights reserved.
The exploration of icy satellites such as Saturn’s moon Enceladus or Jupiter’s moons Europa and Ganymede is one of the popular branches in modern space research. Each icy body has its own feature: water ice presence on Enceladus, cryo-vulcanism on Ganymede, Europa’s smooth shell. Also conditions on these moons allow speculation about possible life, considering these moons from an astrobiological point of view.
Research in the last decade shows that there should be a deep ocean (the estimated thickness varies up to 100km) under the icy sheet of Europa. The estimated thickness of the ice on Ganymede varies up to 800km. To study this possible ocean and to look for life’s traces, it is necessary to penetrate the icy sheet. This means that special equipment should be designed. On the Earth, similar kinds of probes have been used successfully to study glaciers. Use of such probes enables extrapolation from terrestrial to extraterrestrial application.
There are several ways to penetrate through the ice. The authors consider these possibilities and explain why, in the case of exploration of icy moons, a melting probe is preferred.
Other unsolved problems are in the areas of analyzing how the probe will move in low gravity and low atmospheric pressure; whether the hole formed in the ice will be closed when the probe penetrates far enough or not; what is the influence of the probe’s characteristics on the melting process; and what would be the order of magnitude of the penetration velocity. This study explores the technique based on elasto-plastic theory and so-called “solid water” theory to estimate the melting velocity and to study the melting process. Based on this technique, the authors considered several cases of melting probe motion, estimated the velocity of the melting probe, studied and discussed the influence of different factors, and propose an easy way to optimize the parameters of the probe.
Nowadays planetary bodies' studies are of the great interest. First of all, such space objects are the icy moons of the giant planets like Jupiter and Saturn. Of particular interest is the relatively smooth Europa's surface that is covered by a bands system, valleys, and ridges. To study the planetary icy body in future space missions, one of the problems to solve is the problem of design of a special device, capable to penetrate through the ice, as well as the choice of the landing site of this probe. To select possible landing site analysis of the Europa's surface relief formation is studied. This analysis showed that the compression, extending, shearing, and bending can influence on some arbitrarily separated section of Europe's icy surface. The computer simulation with finite element method (FEM) was performed to see, what types of defects could arise from such effects. Also the problem of melting probe movement through the ice is considered: how the probe will move in low gravity and low atmospheric pressure; whether the hole formed in the ice will be closed when the probe penetrates far enough or not; what is the influence of the probe's characteristics on the melting process; what would be the order of magnitude of the penetration velocity. This study explores the technique based on elasto-plastic theory and so-called “solid water” theory to estimate the melting velocity and to study the melting process. Based on this technique, several cases of melting probe motion are considered, the velocity of the melting probe is estimated, the influence of different factors are studied and discussed, and an easy way to optimize the parameters of the probe is proposed.
Mathematical and computer simulation of economic processes.
In the article are esteemed assigning and main capabilities of the subsystem of the analysis and maintenance of thermal values of designs of radio electronic means ASONIKA-T, and also principles of simulation of thermal processes in designs with the help of the subsystem ASONIKA-T. The example of simulation of thermal processes in a standard design is adduced.
The application of mathematical modeling methods (with subsequent computer sales) to determine the parameters of accuracy geometry bands obtained with the new equipment and process the step deformation bands of hard alloys based on copper