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Computational simulation of machining
Zvěřina, Martin ; Hůlka, Jiří (referee) ; Petruška, Jindřich (advisor)
This Master’s thesis process list of different finite element programs, which allows us to simulate process of material separation. We estimated their advantages and disadvantages in the end. In program ANSYS Ls-Dyna was created 3D model, in which we simulate process of orthogonal splinter machining and we study dependence of changes different input parameters (tool geometry, depth of cut, cutting speed) on the chip form and forces rate between tool and workpiece.
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Computational prediction of material damage in forming
Kunc, Vítězslav ; Hůlka, Jiří (referee) ; Petruška, Jindřich (advisor)
The purpose of this thesis is to deal with the initiation of chevron cracks in forward extrusion. Using numerical simulation, the ability of selected fracture models which prognosticates the initiation of chevron cracks is observed. The influence of process parameters is studied (friction, reductions in cross section and angles of reduction) on the initiation and diffusion of damage. Solutions was executed by Abaqus for material 12 050.
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Computational analysis of residual stresses in autofrettaged high pressure rails
Blaha, Jakub ; Petruška, Jindřich (referee) ; Vrbka, Jan (advisor)
The master‘s thesis is aimed on numerical simulation of autofrettage of high pressure fuel vessel – rail in Common Rail system. First there is described Chaboche model, which is later used for simulation of autofrettage. There are described different approaches which can be used to obtain sufficient material model. Then there is observed influence of these different approaches on stress state of rail within the process of autofrettage. Suitability of Chaboche model for autofrettage and re-autofrettage simulations is assessed by comparing with more complex Jiang model. In the end there is a study of influence of autofrettage pressure on different properties, especially on residual stresses.
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Influence of process parameters in forward extrusion on the die loading
Pokorná, Jana ; Návrat, Tomáš (referee) ; Petruška, Jindřich (advisor)
One of the decisive factors of effective using of forward extrusion technology is lifetime of forming tools. Die is very loaded forming tool which loading and therewith related lifetime can be significantly affected by its construction. Construction also affected quality of extruded material. Finete element method allows to simulate this process and assess force which is needed to extrusion and state of stress in die and extruded material. Numerical simulation was realized in program ANSYS 11.0. Influence of reduction, angle of reduction, lenght of extruded material, rounding transition of die parts, extruded material and friction coefficient on die loading and emergence of cracks in extruded material was set in this diploma thesis. Results can be used to die construction optimalization.
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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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Strength and deformation analysis of parametric family of hydraulic stretchers
Jagoš, Jiří ; Vosynek, Petr (referee) ; Petruška, Jindřich (advisor)
The master thesis is focused on an evaluation of a preload lost in a tappered joint. The analyzed bolts are preloaded by a hydraulic tensioner. When the tensioner is removed, the joint is established and the preload in bolt is decreased. The analysisis carried out on axisymmetry model of joint in ANSYS Workbench 15, a finite element method is implemented in that software. The evaluation of the preload lost is made for a used range of ratio of clamped length to a nominal diameter of bolt. Geometry and material assumptions are defined. Before preloading of bolts to a desired value the process of stabilization preloading must be done otherwise outlines of the analysis are not applicable. On the base of the outlines of the analysis, the method for analytical computing of the desired pretension is done. The method involves the preload lost, which occurs due to establishment of the joint. The strength assesment of the hydraulic tensioner for bolts M72x4 is done. A 3D model of the tensioner with one plane of symmetry was used. Strength criteria for maximum allowed linear-elastic stress are in accordance with ČSN EN 13 445-3.
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Computational analysis of a car axle arm opening
Procházka, Vojtěch ; Kubík, Petr (referee) ; Petruška, Jindřich (advisor)
This thesis is focused on behavior of control arm opening with bushing pressed in. The tested component is a part of control arm of a car. The parts were tested in tensile and compressive strength. Real experiments were measured by optical system Aramis during the testing to determine deformations of the part. These tests are also modeled by a finite element method using an Abaqus software. In GOM Correlate software is created full-field comparison of deformation results from Aramis and FEA. Based on this comparison computational model is calibrated. Sensitivity analysis is performed at the end of the thesis.
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Stress-strain analysis of a chosen fire extinguisher
Češek, Jakub ; Petruška, Jindřich (referee) ; Novák, Kamil (advisor)
Bachelor’s thesis deals with stress-strain analysis of chosen extinguisher. Within this thesis, different types of closures are summarized and their influence in stress state is thoroughly analyzed. The stress-strain analysis is solved by using momentum shell theory as well as membrane shell theory. At the end of this thesis numerical solutions by using Finite Elements Method (FEM) is performed in Ansys software. All results are compared in conclusion of the thesis.
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Computational simulation of leveling of pipes
Peter, Ondřej ; Šebek, František (referee) ; Petruška, Jindřich (advisor)
The master thesis deals with the computational simulation of cross-roll leveling of tubes with various degrees of thickness. Based on the Lagrange approach, a several FEM models of curved tube were developed and subsequently solved in ANSYS commercial software. Furthermore, a several models of curved tube were solved by algorithm based on the Euler approach created at UMTMB FME BUT. Based on the comparison of output parameters from both algorithms it was found that the output parameters are comparable to the d/D ratio (inner/outer diameter of the tube) = 0.43.
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