Simulation of a cylindrical rod stretching process during hot deformation
This aim of this paper is the interpretation of the results of mechanical testing of materials to determine their properties under hot deformation. As an example, a simulation of rod stretching in superplasticity mode was considered. Comparing obtained data with the analytical solution was conducted.
The influence of different forms of housing cryobot speed and efficiency of movement them into the ice structures. The problems of cryobot to study the ice surface in Europe
Computer simulation of mechanical testing is used primarily for the correct interpretation of their results and is particularly relevant in cases, when the properties of the material during deformation are essentially nonlinear. For example: when we study mechanical properties of materials with high rate sensitivity. First of all it is superplastic titanium alloys. Superplastic materials exhibit the ability to severe plastic deformation without discontinuities if forming occurs in a narrow range of strain rates, specific to each alloy and temperature-dependent. In the study of superplastic materials, it’s necessary to maintain a constant rate of deformation of the sample. This is achieved by conducting an experiment with a special program loading, crosshead speed at which change during the experiment.
The purpose of this study is to find out the characteristics of hot forming of Ti-6Al-4V titanium alloy in order to determine the conditions of its superplastic behavior. The experiments were performed in two stages: the stepped tensile-tests series (temperature range 700 – 925 °С) and the constant strain rate tensile-test series (temperature range 775 – 925 °С). By the results of stepped tensile tests the constitutive equations which describe relationship between stress and strain rate for each temperature were constructed. On the base of obtained data, the temperature and strain-rate ranges which ensure the realization of superplasticity at forming of Ti-6Al-4V alloy as well as optimal strain rates which corresponds to the maximum value of strain rate sensitivity exponent were determined. In was shown that at low temperatures (700 – 775C) the Ti-6Al-4V alloy shows all signs of superplasticity, however at these temperatures the optimal strain rates are too slow for industrial technological procedures. The dependence between optimum strain rate and reciprocal temperature appears to be well fitted by exponential low. At the second stage of the experimental research, the tensile-tests with a constant, optimum for each temperature strain-rate were carried in order, to estimate the real initial flow stress and the character of strain hardening of the material during the deformation with optimum strain rate. In was found that flow stress values obtained by stepped tensile tests matches the values form constant-strain-rate tests with effective strain value equal to 0,2 and the strain hardening during the deformation with optimal strain rates is significant.
We discuss the materials associated with the formation of chaotic bands on the ice surface on Europe, a satellite of Jupiter. There are suggestions as to their origin.