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Structural Health Monitoring in aerospace and civil engineering supported with two ultrasonic NDT methods - AE and NEWS
Převorovský, Zdeněk ; Krofta, Josef ; Farová, Zuzana ; Chlada, Milan
Structural Health Monitoring (SHM) becomes today an important technology improving reliability and safety of aeronautical and civil structures. Combining of two ultrasonic NDT methods - Acoustic Emission (AE) with Nonlinear Elastic Wave Spectroscopy (NEWS) - in SHM systems brings many advantages. AE enables real-time detection and localization of initiation and progression under operational stimulations, and NEWS methods provide retrieval of structural faults and complete information on AE sources. Examples of a complex SHM system design for critical parts of both aircraft and building roofs are discussed in this paper. The NEWS pseudo-tomography procedure, based on Time Reversal Mirrors (TRM) with Excitation Symmetry Analysis Method (ESAM), enabled zone-location of initiating defects, not detectable by other classical NDT procedures.Our results reflect good robustness of both techniques, and support their helpfulness in SHM of aircraft and building structures.
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Motion Techniques and Patterns - Creative Freedom of Expression
Riedlbauchová, Veronika ; Laštovková-Stodolová, Adéla (advisor) ; Krofta, Josef (referee)
Riedlbauchová, Veronika. Motion Techniques and Patterns - Creative Freedom of Expression. M. A. Thesis, Academy of Performing Arts in Prague, Theatre Faculty, Prague 2009, 111 pp.
In her M. A. thesis, the author focuses on the education of an open and all-round actor and stage director by the means of movement. In doing so, she draws from her artistic practice as well as from her personal experience with physical acting she got acquainted with during two years of study at Institut del Teatre in Barcelona. She points out that the contemporary theatre still keeps omitting movement - one of the most important stage elements. Through a detailed reflection she presents various motion techniques and patterns, which may signifícantly enrich the actor´s or stage director´s expression capabilities subsequently leading them to creative freedom. The author emphasizes an empiric approach to the search for a stage expression and she presents a variety of concrete exercises. She also demonstrates some ways of applying the knowledge of particular techniques in modern practice.
The paper is divided into two parts. The first part called Body Language focuses on general patterns of motion and its communicativeness in theatre. In the first chapter the author pursues motion as a specific element of stage work, in the second chapter as a component of the theatre language. She explores motion and its energy, the motional expression and its capability to reveal the personage´s emotions, motion in a mutual interaction with the space and time, motion in relation to the sound and word. In the third chapter she expresses a necessity of a lifetime development and training of an actor and stage director, which reinforces their creativity and makes them equal partners. In the second part called How to Apply a Mask Technique in a Contemporary Practice the author focuses in detail on the application of the knowledge of two concrete mask techniques in a broader theatre practice. The fourth chapter presents work with a neutral mask inspired by the method of Jacques Lecoq and its employment in the creation of a stage personage. The last, fifth chapter concerns the old technique of commedia dell´ arte and its application in teaching the improvisation. This chapter is innovatory as it presents practical instructions how to train the actor´s improvisatory abilities in the framework of the whole onstage composition.
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Enlightened Actor
Hajdyla, Jiří ; Krofta, Josef (advisor) ; Tichý, Zdeněk (referee)
I am convinced that the theatre phenomenon is closely linked with light and its theatre performance characteristics. I am convinced that the first catharsis in the theatre history was the moment when a spectator experienced an awe while looking at the sunset and realizing his smallness. I am convinced that the wholeness of the creation of our world including its smallest details is based on theatre principles. Shouldn't theatre be the mirror of life? Is not man created as an image of God, according to the Bible?
Isn't nature with all its action and principles an image ? a mirror ? of something hidden, great, but intimate to us? In this respect, I would like to name the light as the agent of all these pictures. Light is a kind of informer of hidden things for the man ? things that man cannot see but the light tells him about them. The world is one great light theatre. It is a God's theatre in which we as well as all things around us are the theatre props and where the light enters as God's actor. For this reason, I as an actor see light as my colleague from whom I can learn a lot. Recognizing the possibilities of light in a theatre performance is a prerequisite for becoming an enlightened actor, an actor who desires to draw from the light, to be the light and to manage the stage space similarly to the light?
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Searching for the Magic of the Theatre
Happonen, Linnea ; Pilátová, Jana (advisor) ; Krofta, Josef (referee)
Searching for the Magic of the Theatre, is according to the name, a
theoretical search of the author in world of theatre. The work is divided
in four parts, first for searching the forms, second for the means and
third for the makers of magic. The fourth part is reflecting author´s own
concrete experience in theatre, especially in the theatre group Krepsko,
and that with looks for before, during and after performances. The aim of
this writing is to resume some thoughts, questions and beliefs of the
author after ten years working in and around theatre.
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NONDESTRUCTIVE EVALUATION OF CONCRETE STRUCTURES BY NONLINEAR ULTRASONIC SPECTROSCOPY METHODS
Převorovský, Zdeněk ; Krofta, Josef ; Chlada, Milan
Facilities of nonlinear ultrasonic spectroscopy for defects detection in steel-reinforced concrete structures are discussed in the paper. Results are shown from non-destructive evaluation of concrete block samples reinforced with intact and corroded armature. Seven piezoelectric transducers were glued on the sample surface. One of them was used to harmonic excitation of the structure with frequency f1=45 kHz and stepwise growing amplitude. Among other 6 transducers one was multiplexed as a second transmitter of harmonic signal with f2=217 kHz and remaining sensors were receiving structural response on 2-frequency excitation. Most pronounced spectral differences between samples with corroded and intact reinforcement were observed on amplitude dependence of 3f1/2f1 ratio and f2-3f1 sidebands, which can be considered as nonlinear parameters characterizing concrete damage.
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Nelineární časově reversní ultrazvuková-tomografie
Převorovský, Zdeněk ; Krofta, Josef ; Převorovský, David
Nonlinear Elastic Wave Spectroscopy (NEWS) becomes new effective method for non-destructive testing of complex structures providing high sensitivity of damage detection. One of the most promising NEWS procedures is Nonlinear Time Reversal Acoustics (NLTRA) realizable in a lot of different ways. Common NLTRA procedure is mostly global, which means that localization of defect by this procedure can be often difficult. A modification of NLTRA is proposed in this paper, based on similar arrangement as ultrasonic tomography. Computer controlled switching between transmitting and receiving transducers is realized by specially designed high-voltage relay multiplexer.
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Ultrazvukové časově-reversní zrcadlo-numerická simulace v desce s defektem
Krofta, Josef ; Převorovský, Zdeněk
The time reversal mirror (TRM) is a method which can be effective in NDE of defects in materials. In this case an input ultrasonic wave is transmitted into the examined sample, then recorded by receiving transducers, time reversed and sent back by the same transducers. A simple numerical model of a solid plate was developed. Using this model, a simulation of TRM was performed. The propagation of ultrasonic waves used in time reversal method is studied. A number of tests with various configurations of transducers and defects and different methodology of the TRM procedure is simulated.
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