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Parameter Identification for Elastic-plastic Material Models from Experimental Data
Jeník, Ivan ; Šebek, František (referee) ; Kubík, Petr (advisor)
This master's thesis deals with the identification of the material flow curve from record of tensile test of smooth cylindrical specimen. First, necessary theory background is presented. Basic terms of incremental theory of plasticity, tensile test procedure and processing its outputs are described. Furthermore, possibilities of mathematical expression of the elastic-plastic material constitutive law, thus mathematical expression of the material flow curve itself. Mechanism of ductile damage of material is explained briefly as well. Overview of recent methods of the flow curve identification is given, focused on cases, when the stress distribution in a specimen is not uniaxial. That is either kind of analytic correction of basic formulas derived for uniaxial stress state, or application of mathematical optimization techniques combined with numerical simulation of the tensile test. Also unusual method of neural network is mentioned. For 8 given materials, the flow curve identification was performed using different methods. Namely by analytic correction, optimization, sequential identification and neural network. Algorithms of the last two methods were modified. Based on assessment of obtained results, application field and adjusting the parameters of single algorithms was recommended. It showed up, that an effective way to the accurate and credible results is the combination of different methods during flow curve identification procedure.
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Proposal of a program for solving of problems of simple tension/compression of bars and strut frames
Martínek, Tomáš ; Kubík, Petr (referee) ; Polzer, Stanislav (advisor)
The aim of this work is a program that will solve problems from the simple tension /compression bars and strut frames in the range of bachelor. The work consists of two programs developed in the Borland Delphi development environment. The programs allow the user to define a bar (strut frames) on the basis of the geometrical parameters and constraints, determine the rate of statical indetermination, make the necessary calculations and, if necessary, indicate the condition of deformation (a program for solving bars). The written part of the work serves as a manual.
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Development and application of computational model of ballistic resistant composite laminate
Urbášek, Jan ; Kubík, Petr (referee) ; Petruška, Jindřich (advisor)
This master thesis is aimed at computational modeling of ballistic resistant layered laminate. The introductory sections of the thesis are aimed at understanding the individual topics that are closely related to the interaction of the projectile and target and computational modeling of this process. The main goal of this thesis was to create a computational model that is able to reflect the behavior of aramid fabric during the interaction with the projectile. During the development of the computational model were used more methods of modeling and also more material models were used. For the purposes of the development of the computational model were used the available data of the companies SVS FEM s.r.o. and VVÚ s.p. The outcome of the diploma thesis is a computational model of aramid fabric which is designed for ballistic protection simulations. This model is validated on the basis of available experiments. The validated computational model is then applied to the simulation of ballistic protection.
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Minimization of residual stresses for rolled long products
Kubík, Petr ; Raudenský, Miroslav (referee) ; Petruška, Jindřich (advisor)
This thesis deals with simulation of cooling of rail during its passing through cooling device which has been designed by the heat transfer and fluid flow laboratory. Inputs of the computational model have been set up to get best possible correspondence between outputs of the computational model and results of experimental measurement. The solution with using of model of austenitic stainless steel is provided in first part of the thesis. The solution with considering model of carbon steel is performed in next part. Using of model of carbon steel allows including evolution of latent heat during phase changing. A fields of residual stress has been calculated for different cooling conditions in the last part of this thesis.
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Stress, deformation and reliability computational analysis of the adjustable tandem trike frame
Ščotka, Martin ; Kubík, Petr (referee) ; Vrbka, Jan (advisor)
This bachelor thesis deals with stress, deformation and safety analyses of adjustable frame of tandem tricycle. Starting with brief introduction of cycling, especially alternative cycling followed by indicating of whip assumptions and computational model of the frame. The final calculations have been done in three basic modes: direct motion, braking and cornering. Inner Stress Resultant has been summed, reduced pressure in a dangerous point has been expressed and safety issue has been figured up as well. Mathematical software MAPLE has been used to solve the assignment. Model is provided in software Autodesk Inventor
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Implementation, Calibration and Application of Ductile Fracture Conditions in FEM Programs
Kubík, Petr ; Plánička, František (referee) ; Kotoul, Michal (referee) ; Petruška, Jindřich (advisor)
The presented work is concerning with ductile fracture problematic under monotonic loading which is result of gradual material degradation at large plastic deformation. At present, a large number of models, which calibration is not trivial, are used for its prediction. Ductile fracture mechanisms and cut-off region are described in the literature search part. Next, there is given a summary of criteria which are based on different approaches to ductile fracture. There were proposed and used KHPS and KHPS2 criteria within this PhD thesis. Procedure of assessment of the stress-strain curve and ductile fracture criteria calibration are described in last part of the literature search. A summary of tests, which were done in order to calibrate chosen criteria, is given in experimental part. Various stress states within broad range of stress triaxiality and Lode parameter were reached using these tests. Special type of specimen, by which very low stress triaxiality value is reached, was designed within this work. All specimens were made from the steel 12 050. Wrought rods of one melt with circular cross-section of 27 mm in diameter were used as semi-product. Calibration of chosen ductile fracture criteria was performed using foregoing tests. These criteria were implemented by author into explicit finite element software ABAQUS/Explicit using user subroutine VUMAT. Chosen criteria were used for simulation of multistep extrusion at which formation of internal central cracks occurs. These criteria were also used for simulation of cutting of circular cross-section rods. Results from simulation were compared to experiments which were done by industrial partner J-VST.
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Analysis of influence of geometric deviations of semifinished product on following bending process
Anděl, Tomáš ; Kubík, Petr (referee) ; Vosynek, Petr (advisor)
Presented diploma thesis was created in cooperation with Siemens s.r.o., and deals with the analysis of the bending of aluminium sheets which are later used as a conductors of high voltage electrical energy. These parts are completed into assemblies which serves as connectors of particular segments of an electrical network. The problem occurs as a result of incorrect bend, because it is impossible to join these sections properly. The customer would like to verify if the defined tolerances of semi-finished products are sufficient for proper bend and in case they are not, the tolerances should be modified. Due to the requirement for running numerical simulation in one of the open source software, the Salome-Meca program environment was used.
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