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Application of Electromagnetic and Acoustic Emission for the Diagnostics of Advanced Composite Materials
Trčka, Tomáš ; Chobola, Zdeněk (referee) ; Lokajíček,, Tomáš (referee) ; Koktavý, Pavel (advisor)
The subject of this dissertation is a theoretical and experimental study of electromagnetic and acoustic emission generated in the course of crack formation in solid dielectric materials. Theoretical part of this work is focused on the electromagnetic emission method, because it is related to a number of unsolved problems in the field of generated emission signals measurement, as well as in the field of the correct interpretation of obtained experimental data. Consequently, issues of emission signals detection by capacitance sensors and the transformation of crack primary parameters on the measured variables within the proposed transfer system have been dealt with. The results in this area were an extension of application range of the electromagnetic emission method on composite materials (especially on fiber reinforced polymer composites), identification and evaluation of the most significant emission sources in investigated composites and developing a methodology for evaluating of the crack primary parameters based on the measured emission signals waveforms in time and frequency domain. The experimental part of this dissertation was focused on a complex methodology for emission signals (including data from additional sensors) continual recording, processing and evaluation and for monitoring the response of stressed material to an applied mechanical load in real-time. Partial results from different research areas were also implemented into this methodology. This included the detection of emission signals, design and implementation of the appropriate measuring apparatus, analysis of measured signals in the time and frequency domain and advanced methods for processing and evaluation of measured data.
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Monitoring masonry buildings affected by the surrounding construction
Kirschbaum, Adam ; Heřmánková, Věra (referee) ; Cikrle, Petr (advisor)
This bachelor’s thesis deals with monitoring of a building object affected by a surrounding construction. In the first, theoretical part the defect of wall constructions, ways of measuring wall cracks and possibilities of a static load are described. The second, practical part deals with monitoring of a multi-storey building which was damaged by a building of a neighbouring object in the gap site. It covers the inspection and documentation of the damage and the description of the applied methods. The results of measuring are elaborated graphically and analysed in connection with interventions to the construction.
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Analysis of stress field in the vicinity of fatigue crack in IPE made from stainless steel
Juhászová, Tereza ; Malíková, Lucie (referee) ; Seitl, Stanislav (advisor)
The master thesis is focused on analysis of stress field in the vicinity of stress concentration of stainless steel IPE beam loaded in tree point bending. Theoretical part includes introduction to fracture mechanics with basic terms, principles and variables used to describe fatigue behaviour of material. It concludes teoretical grounds of fracture tests which are future focus of the thesis, methodes used by numerical softwares and methodes used to obtain numerical results. Practical part includes comparision between two and three dimensional numerical models in three point bending, IPE model with different crack front shapes and plastic zone size. Numerical modelling was processed in Ansys Mechanical APDL. Thesis also involves results of experimental testing evaluated using numerical model.
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Monitoring of buildings in relation to surrounding construction activity
Ledvoňová, Monika ; Heřmánková, Věra (referee) ; Cikrle, Petr (advisor)
This thesis deals with the monitoring of buildings disorders caused by surrounding con-struction activity. The first section describes the methods of monitoring failures, from the detailed inspection to the result evaluation, there is also given an overview of measuring instruments. The second part describes the methodology of passports implementation and contains an example of the object repassport that was violated by tunneling. There is a comparison of passport and repassport. The third largest section describes a practical ex-ample of monitoring object cracks around which the building activity took place. There is a documentation of failures, a description of the measuring spots choise, installation of the bases, monitoring, processing of results and conclusion.
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Sewage disposal plant
Doležal, Martin ; Kraut, Jan (referee) ; Šulák, Pavel (advisor)
This thesis deals with the design and static assessment of a concrete part of a sewage treatment plant. Specifically, the calculation and assessment of the base plate, external walls, internal walls and ceiling slabs, elaboration of shape and reinforcement drawings of selected structural element. The concrete part of the Sewage disposal plant is all below ground level. Static system and the calculation of internal forces was carried out in Scia Engineer 2011 - student version.
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Influence of Friction to the Shear Stress State in the Crack-Front Vicinity
Vlach, Jiří ; Hutař, Pavel (referee) ; Horníková, Jana (advisor)
The aim of this master thesis is to explore the influence of frictional forces to the stress and strain on the straight crack tip loaded in shear modes. The first section summarizes the most important things from the field of fracture mechanics. Especially theoretical knowledge about fracture parameters (stress intensity factor, J – integral) and their determination in computational environment ANSYS Workbench. The second part deals with computational modeling. At the beginning, is created the model of material, the model of geometry, the model of loads, etc. Then it is possible to solve the direct problem outlined in the introduction. A result of this thesis is the assessment of how the friction influences the fracture parameters in shear modes II and III.
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Computational analysis of the influence of initial defects on the ceramic foam failure upon mechanical loading
Papšík, Roman ; Majer, Zdeněk (referee) ; Ševeček, Oldřich (advisor)
The thesis deals with computational modelling of ceramic foams and analysis of influence of structural manufacturing defects (like broken struts, closed pores and material clumps) have on foam strength. Model of foam geometry was discretized using beam elements in order to decrease computational cost. In place where several struct join, rigid beam element was used so that the increased stiffness is better modelled. Closed walls of pores were modelled and discretised by shell elements. Influence of loading direction was analysed on foams containing no defects and then influence of amount of defects in foam on strength was further analysed. Highest strength show foams created by cells whose structs are oriented in direction of loading. These were losing strength most rapidly. Foam with structure of rhombic dodecahedral cell was least influenced by presence of closed pore defects but it also showed lowest strength even without defects. Cells with struts oriented in direction of loading experienced biggest drop in strength. Kelvin cell is a compromise. It was shown that difference in strength of strut with constant and varying cross-section is tenths of percent.
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Residual fatigue life estimation of railway wheelset
Pokorný, Pavel ; Zouhar, Michal (referee) ; Náhlík, Luboš (advisor)
The first part of this master's thesis deals with the high cycle fatigue of materials, especially on growing cracks using linear elastic fracture mechanics. Much of this work is focused on the concept of stress intensity factor. This concept is nowadays one of the most widely used concepts for describing a body with crack. The first part ends with theoretical approaches to determine the residual fatigue life of the body with a crack. The second part of this master's thesis is focused on the determination of residual fatigue life of a specified railway wheelset. An existence of crack-like defect is assumed at the railway wheelset. The goal of this master's thesis is to estimate how long it will take to grow from initial defect to a critical crack length. The last part of this master's thesis is devoted to addiction order load cycles on crack growth rate.
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Methodology of Passportization of Building Objects Damaged by Surrounding Activities
Novák, Jindřich ; Hobst, Leonard (referee) ; Anton, Ondřej (advisor)
The passportization of building structures is very important task efore the initiation of negative influences on to object. The aim is to prevent possible legal deputies in between owners of affected object. The demand of passportization of building structure is increasing with the exploding of developments projects from green fields to vacancies. The aim of this work is to determine the metodology of passportization of building structures and to apply it on existig object.
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