Papers by Keyword: Deformation Model

Abstract: This article suggests a calculation procedure for the parameters of complete moment-curvature deformation diagrams with a down leg that can be used for the calculations of the multistorey monolithic building frameworks taking into account the specifics of reinforced concrete. To construct complete deformation diagrams for bending elements, a non-linear deformation model is used that is based on using the physical diagrams of the concrete and reinforcements to calculate the inner moments of cross-sections at all loading stages via balance and strain compatibility equations. Using this model, the authors researched complete moment-curvature deformation diagrams for the elements with different percentages of longitudinal tensile reinforcement that changes the bending properties of the structure. We used grade А500 steel as the reinforcement. The parameters of the tensile reinforcement diagram were determined in the tension testing of samples with constant deformation rates. The performed computer tests to calculate the moment-curvature diagram parameters for reinforced concrete beams reinforced with grade А500 efficiency rods and conventional grade A400 reinforcement rods with different longitudinal reinforcement congestion rates helped the authors assess the bending properties of the elements under conditions approaching their destruction and determine their efficient use in the calculations of building frameworks taking into account the redistribution of forces.

Abstract: The paper presents the results of experimental studies of physical and mechanical properties of casting cores (-set process using Carbectis binder) high-speed heated with subsequent destruction. Based on experimental data, such parameters of deformation model of a core are obtained which permit to calculate the values of hindered shrinkage of AK7Ch alloy with the accuracy of 1.5 %.

Abstract: Considering the material property of the soil body, A method erecting the deformation model of the horizontal deformation monitoring network in the landslide is discussed, it uses the partitioning method to erect the deformation model based on the topographical and the geological condition and the mathematical statistics theory. The method erecting the model can describe the deformation law of the landslides objectively. The example of calculation verifies that the method erecting the model is suitable and feasible.

Abstract: The goal of this work was to study the asymmetric rolling process using the Finite Element Method (FEM) coupled with the deformation model of polycrystalline material. The Leffers-Wierzbanowski (LW) model was selected to be implemented into FEM. This implementation enables a study of heterogeneous plastic deformation process, like asymmetric rolling, taking into account its crystallographic nature. The asymmetric rolling was realized using two identical rolls, driven by independent motors, rotating with different angular velocities. This enabled to obtain a controlled range of rolling asymmetry. Our aim was to examine the properties of asymmetrically rolled commercially pure titanium (Grade 2).

Abstract: The relation between residual stresses occurring in plastically deformed material and after subsequent annealing is of practical and theoretical importance. In the present work the X-ray multi-reflection method was applied to determine residual stresses and their orientation distribution in rolled and annealed ferrite and austenite steel samples. An important decrease of the first- and the second-order residual stresses was observed during recovery and recrystallization processes. Diffraction peak width was also studied and correlated with stress variation during annealing. Different kinetics of stress relaxation in ferrite and austenite were explained by different levels of stacking fault energy and different types of intergranular interactions occurring in these materials.

Abstract: Rotation of grain crystal lattice is the basic mechanism of texture formation and of anisotropic behavior of metals during plastic deformation. The classical definition of crystal lattice rotation leads in some cases to different texture and residual stress predictions than the definition based on the orientation preservation of selected sample planes and/or directions. Also the intensity of grain-matrix interaction plays an important role in the prediction of the above quantities. These problems were studied using elasto-plastic deformation model of polycrystalline materials. Examples of austenite and ferrite steels were considered.

Abstract: Formation of residual stresses and crystallographic textures during rolling have been studied using elasto-plastic deformation for polycrystalline material (Leffers-Wierzbanowski model). The rotation of grain crystal lattices is the basic mechanism of texture formation and anisotropic behavior of metals during plastic deformation. The classical definition of crystal lattice rotation leads in some cases to different texture predictions than the definition based on the orientation preservation of selected sample planes and/or directions (preservation condition). Also predicted residual stresses can be influenced by a choice of rotation definition. In the used deformation model of polycrystalline material, the intensity of grain-matrix interaction is described by the parameter L= aG, where G is shear modulus and a is elasto-plastic accommodation parameter. Model calculations have been done for different values of this parameter and for two definitions of lattice rotation. The predicted second order residual stresses and crystallographic textures for cold rolled ferrite steel are compared with experimental ones.

Abstract: X-ray diffraction method was applied to measure residual stresses in deformed and annealed polycrystalline austenitic steel. An elastoplastic deformation model was used in analysis of experimental data. As the result, the orientation distribution function of grain stresses, created during elastoplastic deformation was determined and presented in the Euler space. An important decrease of the first and the second order residual stresses was observed during recovery process. It was found that the magnitude of the stresses decreases, while their distribution between different grain orientations remains almost unchanged.

Abstract: The crystallographic texture formation in low carbon steel during asymmetric rolling was studied experimentally and analysed numerically. Modelling of plastic deformation was done in two scales: in the macro-scale using the finite element method ( FEM) and in crystallographic scale using the polycrystalline deformation model (LW model). The stress distribution in the rolling gap was calculated using FEM and next these stresses were applied in LW model of polycrystalline plastic deformation. In general, the predicted textures agree very well with experimental ones.

Abstract: Stored energy plays a crucial role in recrystallization process. One can distinguish two contributions to this energy. The first one is the elastic energy, connected with residual stresses, i.e., with grain-grain interaction. Another part of the stored energy is due to dislocation density, which is mainly localized inside grains. The latter one is considered as a main driving force of recrystallization. However, the stored energy connected with residual stresses can also have some influence on this process. Both types of energy can be determined experimentally and predicted by deformation models. Taking into account both types of the stored energy, some features of recrystallization textures can be explained.