Papers by Keyword: Numerical Modeling

Abstract: The increasing interest for new materials in designing of new structures led to a real need to use powerful analysis tools, able to take into account correctly, their specific performance. Advantages of multilayer structures are now well understood, these materials having already part of the structural components of aeronautics and not only. The use of polyurethane rigid foam (PU) has grown rapidly, due to the excellent properties of energy conservation, a good combination of mechanical strength and weight - lower than other traditional materials with similar mechanical properties. In this paper the authors create a numerical model of polyurethane foam which will be used in further studies of impact behavior of sandwich structures with a polyurethane foam core, coated with steel or aluminum thin layers.

Abstract: The algorithm for numerical modeling of the heterodiffusion from a finite thickness layer under restricted impurity solubility in the matrix and concentration dependence of the diffusion coefficient is proposed. It allows obtaining the time dependence of the impurity distributions in conditions which mimic real experiments.

Abstract: The article presents the results of a numerical study of the compression wave attenuation (CW) in water barriers. The impact of barriers thickness, their quantity and concentration of water particles in the barrier have been analyzed in the process of CW attenuation.

Abstract: Double skin facades very popular in this time. They are applied for construction of new buildings and for reconstruction. But double skin facades contains some defects. In the present paper concrete constructive changes in a design of the Double skin facades which are offered. This changes will can to normalize heatmoisture conditions in the building. All proposed solutions are proved by theoretical calculations and numerical simulation.

Abstract: Materials used for the construction of ballistic shields are characterized by a variety of behaviours under the influence of external loads. Ballistic impact (by a bullet) in armour (ballistic shield) is an example of the phenomena that could be considered in the category of a dynamic load caused by the strike of the mass. Computer simulations are commonly used in such situations. It is especially important to adopt a proper model of the behaviour of the material. This paper presents the results obtained by simulating free 3D points and using the application developed by the authors for the purpose of this research. The made calculations include the translational motion and rotary motion of the projectile as well as the stiffness of the material, the damping of the material, friction at the points of contacting surfaces, viscous friction and plastic deformation (the material beyond the plastic yield point is perfectly plastic). The results of simulations were validated with experimental research.

Abstract: One of the modern methods of production of round bars is the process of rolling in three-high skew rolling mill. This method enables the production of bars with both standard materials as well as hard deformation materials. In this paper, the results of theoretical and laboratory research of the 20 mm aluminum A1050 round rods rolling in three-high skew rolling mill process are presented. The numerical analysis was carried out upon applying the Forge 2011® software package. Based on the theoretical research, the stress, strain and temperature distribution during the rolling process were determined. In order to verify the numerical results, rolling aluminum rods were explored in laboratory conditions.

Abstract: The final mechanical properties of hot stamped components are affected by many process and material parameters due to the multidisciplinary nature of this thermal-mechanical-metallurgical process. The phase transformation, which depends on the temperature field and history, determines the final microstructure and consequently the final mechanical properties. Tailored hot stamping parts – where the cooling rates are locally chosen to achieve structures with graded properties – has been increasingly adopted in the automotive industry. Robustness of the final part properties is more critical than in the conventional hot stamping. In this paper, the robustness of a tailored hot stamping set-up is investigated. The results show that tailored hot stamping is very sensitive to tooling temperature, followed by latent heat radiation emissivity, and convection film coefficient. Traditional hot stamping has higher robustness compared to tailored hot stamping, with respect to the stamped component’s final material properties (i.e. phase fraction, hardness).

Abstract: During the process of hot stamping, due to the deformations of sheet metals are mainly bending and shallow drawing, as well as to prevent the temperature strikingly drop caused by the local contact of sheet metal and die, the hot stamping tool usually does not set up blank-holder. And this leads to the occurrence of local wrinkles in some types of hot stamping parts, which affect the quality of the parts. Through the hot stamping tool design and process test of a car ́s B pillar, it discovered that the local wrinkle in the part ́s big end is more severe. As a result the program was modified by taking advantage of the forming principle of the counter punch to improve the design of upper tool (die), which eliminated the local wrinkle in the big end and improved the contact cooling efficiency, consequently ensured the hot forming parts ́ quality and reduced the production rhythm.

Abstract: Contribution deals with experimental measurements of deformations in the place exposed to local load caused by additional pre-stressing. The measurements are made at the masonry brick corner built in the laboratory equipment. The laboratory equipment was designed at Faculty of Civil Engineering VŠB – TU Ostrava for measurement tri-axial stress-strain conditions in masonry. In this brick corner one pre-stressing bar is placed. And on the pre-stressing bar is anchored to the anchor plate which transfer pre-stressing forces to the masonry. The thickness of brick corner is 440mm and anchor plate will be used about thickness 10, 20 and 30mm. Mathematical modelling of brick corner is based on finite element method using software ANSYS and then the results are compared with results of laboratory tests. On the basis of these results it should be possible to improve the models and to approach closer to the accurate and at the same time simple procedure for design of pre-stressed masonry.

Abstract: In mathematical models, for forecasting prices on commodity exchanges different mathematical methods are used. In the paper the numerical model based on the exponential approximation of commodity stock exchanges was derived. The price prognoses of aluminium on the London Metal Exchange were determined as numerical solution of the Cauchy initial problem for the 1st order ordinary differential equation. To make the numerical model more accurate the idea of the modification of the initial condition value by the stock exchange was realized. The derived numerical model was observed to determine the influence of the decreased size of the limiting value error causing the modification of the initial condition value by the chosen stock exchange on the accuracy of the obtained prognoses. The advantage of the chosen sizes of the limiting value error 7 % and 8 % within different movements of aluminium prices was studied.