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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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Evaluation of the flange joints calculations approaches
Jeník, Ivan ; Chlud, Michal (referee) ; Hůlka, Jiří (advisor)
This bachelor´s thesis deals with the design and assessment of flange joints with gasket. The first part defines term flange joint and its load. It surveys and assesses the possible alternatives of design solution. Mentioned is the issue of bolt connections with pretension, including force relations in the joint, determination rigidity of parts and their strength. In addition, analysis of the causes of bolts failures and their removal, methods of creating pretension. It gives an overview of the most widely used types of gaskets, their properties, application and definition of characteristic values of gaskets and their determination according to ČSN EN 13 555. Another section deals with the design process of flange joints, standards for the design, desired outputs and assesses analytical and numerical approach. Computational program was created in MS Excel 2007 for design calculation of flange joints according to ČSN EN 1591-1. Verification of the results was performed with calculation of identical models using finite element method (FEM) in ANSYS Workbench 14.0. Errors in standards formulas were submitted. In conclusion, the results obtained analytically and by FEM were assessed for a specific load conditions of gate valve DN 300. Camprofile (grooved) gasket with nonlinear material model was used.
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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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Evaluation of the flange joints calculations approaches
Jeník, Ivan ; Chlud, Michal (referee) ; Hůlka, Jiří (advisor)
This bachelor´s thesis deals with the design and assessment of flange joints with gasket. The first part defines term flange joint and its load. It surveys and assesses the possible alternatives of design solution. Mentioned is the issue of bolt connections with pretension, including force relations in the joint, determination rigidity of parts and their strength. In addition, analysis of the causes of bolts failures and their removal, methods of creating pretension. It gives an overview of the most widely used types of gaskets, their properties, application and definition of characteristic values of gaskets and their determination according to ČSN EN 13 555. Another section deals with the design process of flange joints, standards for the design, desired outputs and assesses analytical and numerical approach. Computational program was created in MS Excel 2007 for design calculation of flange joints according to ČSN EN 1591-1. Verification of the results was performed with calculation of identical models using finite element method (FEM) in ANSYS Workbench 14.0. Errors in standards formulas were submitted. In conclusion, the results obtained analytically and by FEM were assessed for a specific load conditions of gate valve DN 300. Camprofile (grooved) gasket with nonlinear material model was used.
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