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Dynamika soustav těles s neurčitostním modelem vzájemné vazby
Svobodová, Miriam ; Lošák, Petr (referee) ; Hadaš, Zdeněk (advisor)
This diploma thesis deal with evaluation of the impact in the scale of uncertaintly stiffness on the tool deviation during grooving process. By the affect of the insufficient stiffness in each parts of the machine, there is presented a mechanical vibration during the cutting process which may cause a damage to the surface of the workpiece, to the tool or to the processing machine. The change of the stiffness is caused in the result of tool wear, impact of setted cutting conditions and many others. In the first part includes teoretical introduction to field of the uncertainty and choosing suitable methods for the solutions. Chosen methods are Monte Carlo and polynomial chaos expansion which are procced in the interface of MATLAB. Both of the methods are primery tested on the simple systems with the indefinited enters of the stiffness. These systems replace the parts of the stiffness characteristics of the each support parts. After that, the model is defined for the turning during the process of grooving with the 3 degrees of freedom. Then the analyses of the uncertainity and also sensibility analyses for uncertainity entering data of the stiffness are carried out again by both methods. At the end are both methods compared in the points of view by the time consuption and also by precission. Judging by gathered data it is clear that the change of the stiffness has significant impact on vibration in all degrees of freedome of the analysed model. As the example a maximum and a minimum calculated deviation of the workpiece stiffness was calculated via methode of Monte Carlo. The biggest impact on the finall vibration of the tool is found by stiffness of the ball screw. The solution was developed for the more stabile cutting process.
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Surrogate modelling and safety formats in probabilistic analysis of structures
Novák, Lukáš ; Sýkora,, Miroslav (referee) ; Šejnoha,, Michal (referee) ; Novák, Drahomír (advisor)
The presented doctoral thesis is focused on the development of theoretical methods for probabilistic design and assessment of structures. In order to reduce the computational burden of the probabilistic approach, the developed methods are based on surrogate models. Specifically, Taylor series expansion has been utilized for the derivation of a novel analytical method for a simplified semi-probabilistic design of structures represented by non-linear finite element models. The novel approach estimates a variance of quantity of interest and the influence of correlation among input random variables. The second part of the doctoral thesis aims at the development of efficient numerical algorithms for the construction of a surrogate model based on polynomial chaos expansion and its utilization for uncertainty quantification. Although the proposed algorithm is based on cutting edge techniques, it was beneficial to improve its accuracy and efficiency by advanced statistical sampling. Therefore, a novel technique for adaptive sequential statistical sampling, reflecting the exploration of the design domain, and exploitation of the surrogate model, is proposed specifically for polynomial chaos expansion.
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Surrogate modelling and safety formats in probabilistic analysis of structures
Novák, Lukáš ; Sýkora,, Miroslav (referee) ; Šejnoha,, Michal (referee) ; Novák, Drahomír (advisor)
The presented doctoral thesis is focused on the development of theoretical methods for probabilistic design and assessment of structures. In order to reduce the computational burden of the probabilistic approach, the developed methods are based on surrogate models. Specifically, Taylor series expansion has been utilized for the derivation of a novel analytical method for a simplified semi-probabilistic design of structures represented by non-linear finite element models. The novel approach estimates a variance of quantity of interest and the influence of correlation among input random variables. The second part of the doctoral thesis aims at the development of efficient numerical algorithms for the construction of a surrogate model based on polynomial chaos expansion and its utilization for uncertainty quantification. Although the proposed algorithm is based on cutting edge techniques, it was beneficial to improve its accuracy and efficiency by advanced statistical sampling. Therefore, a novel technique for adaptive sequential statistical sampling, reflecting the exploration of the design domain, and exploitation of the surrogate model, is proposed specifically for polynomial chaos expansion.
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Dynamika soustav těles s neurčitostním modelem vzájemné vazby
Svobodová, Miriam ; Lošák, Petr (referee) ; Hadaš, Zdeněk (advisor)
This diploma thesis deal with evaluation of the impact in the scale of uncertaintly stiffness on the tool deviation during grooving process. By the affect of the insufficient stiffness in each parts of the machine, there is presented a mechanical vibration during the cutting process which may cause a damage to the surface of the workpiece, to the tool or to the processing machine. The change of the stiffness is caused in the result of tool wear, impact of setted cutting conditions and many others. In the first part includes teoretical introduction to field of the uncertainty and choosing suitable methods for the solutions. Chosen methods are Monte Carlo and polynomial chaos expansion which are procced in the interface of MATLAB. Both of the methods are primery tested on the simple systems with the indefinited enters of the stiffness. These systems replace the parts of the stiffness characteristics of the each support parts. After that, the model is defined for the turning during the process of grooving with the 3 degrees of freedom. Then the analyses of the uncertainity and also sensibility analyses for uncertainity entering data of the stiffness are carried out again by both methods. At the end are both methods compared in the points of view by the time consuption and also by precission. Judging by gathered data it is clear that the change of the stiffness has significant impact on vibration in all degrees of freedome of the analysed model. As the example a maximum and a minimum calculated deviation of the workpiece stiffness was calculated via methode of Monte Carlo. The biggest impact on the finall vibration of the tool is found by stiffness of the ball screw. The solution was developed for the more stabile cutting process.
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