Processing of plane strain compression test results for investigation of AISI-304 stainless steel constitutive behavior
The paper is oriented toward the determination of constitutive equation constants by the inverse analysis of plane strain compression test results. The interpretation of such results is complicated by the inhomogeneity of strain rate distribution in the specimen caused by rigid ends, the lateral spreading of a specimen friction and the variation of temperature during the test. The results of plane strain compression tests of AISI-304 stainless steel are presented and significant deviations of temperature are observed at higher strain rates. Finite element simulation was performed to estimate the inhomogeneity of strain rate within the specimen and evaluate the effect of friction on the test results. Constitutive equations of the material were obtained by inverse analysis minimizing the deviations between the measured load values and the ones predicted by numerical simulation.
Hot forming behavior of high-strength automotive steel HC420LA is the main objective of this work. Uniaxial and plane strain compression tests were performed at Gleeble 3800 testing machine. A comparison of these types of tests was realized. The material constitutive constants were found as well as the dependences of peak and stady-state stresses on strain rate and temperature. It is shown that the testing technique have an impact on the stress-strain curves obtained by its implementation, this can lead to a mismatch of results of computer simulation of metal forming technologies. In order to evaluate such mismatches a finite element simulation of bar rolling process using the material properties obtained by different testing methods is considered.
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.
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.
In modern space science one of the actual branches is icy satellites explorations. The main interest is concentrated around Jovian’s moons Europa and Ganymede, Saturn’s moons Titan and Enceladus that are covered by thick icy layer according to “Voyager1”, “Voyager2”, “Galileo” and “Cassini” missions. There is a big possibility that under icy shell could be a deep ocean. Also conditions on these satellites allow speculating about possible habitability, and considering these moons from an astrobiological point of view.
One of the possible tasks of planned missions is a subsurface study. For this goal it is necessary to design special equipment that could be suitable for planetary application. One of the possible means is to use a melting probe which operates by melting and moves by gravitational force. Such a probe should be relatively small, should not weight too much and should require not too much energy. In terrestrial case such kind of probe has been successfully used for glaciers study. And it is possible to extrapolate the usage of such probe to extraterrestrial application.
One of the tasks is to estimate melting probe’s penetration velocity. Although there are other unsolved problems such as analyzing how the probe will move in low gravity and low atmospheric pressure; knowing whether hole will be closed or not when probe penetrate thick enough; and considering what order could be a penetration velocity. This study explores two techniques of melting probe’s movement. One of them based on elasto-plastic theory and so-called “solid water” theory, and other one takes phase changing into account. These two techniques allow estimating melting probe’s velocity range and study whole process. Based on these technique several cases of melting probe movement were considered, melting probe’s velocity range estimated, influence of different factors studied and discussed and an easy way to optimize parameters of the melting probe proposed.
This paper considers some problems related to penetration through thick ice layer and to study effectiveness of a melting probe like instrument for penetration through thick Jovians moon Europa icy surface. A melting probes movement model creation, verification and validation, as well as studying a melting process in general is discussed. To create the simulation model of the melting probes movement a mathematical model based on theory of solid water was developed. Model verification was based on experiments carried out by the Austrian Academy of Sciences.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.