National Repository of Grey Literature 24 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Monitoring techniques for special alloys from some medical prostheses.
Savin, A. ; Vizureanu, P. ; Převorovský, Zdeněk ; Steigmann, R. ; Chlada, Milan ; Krofta, Josef ; Baltatu, M.S. ; Craus, M. L. ; Nový, F.
The paper presents complementary methods for noninvasive evaluation of an exotic class of alloys possible to be used in medical prosthetics. The interest in this study is the analysis of Ti alloys with different concentration of Mo and Si, in order to make the elastic modulus and Poisson ratio reach values appropriate with human bones. The both methods, acoustic emission and resonant ultrasound spectroscopy are proposed as complementary methods for nondestructive evaluation of entire sample volume.
Nonlinear ultrasonic porosimetry of 3D printed metallic parts
Převorovský, Zdeněk ; Krofta, Josef ; Kober, Jan ; Kirschner, A.
Additive manufacturing process optimization requires a feedback from nondestructive testing (NDT) and evaluation. In this contribution are discussed NDT results obtained by nonlinear elastic wave spectroscopy methods to classify presence of defects in Ti-6Al-4V prismatic samples fabricated by electron beam printer. Quantitative calibration of porosity was realized by metallography. The best porosity classification results were obtained by nonlinear wave modulation spectroscopy with chirp excitation and by ESAM (Excitation Symmetry Analysis).
Localization of continuous acoustic emission sources using time reversal procedure
Převorovský, Zdeněk ; Krofta, Josef ; Kober, Jan ; Chlada, Milan
A new solution with the help of Time Reversal (TR) signal processing approach is suggested in this paper. It allows planar location of burst AE sources under high background noise using only one transducer, and continuous AE sources with two transducers, both under high background noise from other sources. TR procedure was in this approach applied to long random noise signals for the first time. Suggested method was verified by means of experimentally simulated AE sources on a steel plate and tube. Source location results certified high robustness of suggested approach. Certain disadvantage of the new method is requirement of detailed scanning of region around a presumed source. Scanning may be eliminated if we use numerical simulations with TR signals put into a computer model of the structure. Localization accuracy of suggested procedure (approx. 1 mm) is better than the wavelength and transducers aperture.
NDT in additive manufacturing of metals
Převorovský, Zdeněk ; Krofta, Josef ; Kober, Jan
In this study we tested possibilities of nonlinear elastic wave spectroscopy (NEWS) methods to classify two types of artificially created defects in Ti-6Al-4V prismatic samples fabricated by Electron Beam Melting (EBM) system. Two series of samples with variable internal defects were tested: samples with central circular defects (missing material gaps), and samples with gradually growing stochastic porosity. Each group of samples contained also fully compact sample for a comparison. Five ultrasonic NEWS procedures were used to classify defects variability. Relatively simple experimental facility with two piezoelectric transducers allows interrogate samples and record their response. The best results, documented in this paper, were obtained by two modifications of NWMS procedure. Results of NEWS tests indicate that selected NEWS procedures can be used also for online AM monitoring.
Verification of diagnostic device using NEWS methods
Chlada, Milan ; Krofta, Josef ; Kober, Jan
Within the framework of the project „Verification of diagnostic device using NEWS methods“ supported by SIC, several calibration tests of newly developed apparatus for non-destructive testing of materials by NEWS (Non-linear Elastic Wave Spectroscopy) methods were realized. The report summarizes the results of characteristics measuring for case of particular components of the device and the demonstration tests of defect detection in selected structure parts.
The System for Automatic Location of Impacts
Chlada, Milan ; Kober, Jan ; Převorovský, Zdeněk ; Krofta, Josef
The report deals with the automatic target system for on-line evaluation of shooting precision based on acoustic emission (AE) method, known from the field of non-destructive testing as an approach for location of material defects. Since the bullet stroke on a steel plate can be considered as an AE source, the method can be included in a target system consisting of impact plate, AE sensors and AE measuring system with implemented advanced location algorithms. Whole system can be sized and matched to specific customer needs. At the end of the report, the real demonstration of the system is shown.
Krstić, Marija ; MAKONJ, Karel (advisor) ; KROFTA, Josef (referee)
This thesis conserns the process of preparation of the performance ?The Jungle Book?, based on the original contemporary adaptation of the stories by Rudiard Kipling for childrens' puppet theatre. The curiosity of this process relies on specific conditions in the post-yugoslav Balkan countries, more precisely in Zagreb, Croatia, where the performance will be presented at the beginning of 2013. In order to realise the project at the institutional theatre, it was neccesary to apply for an international grant that supports cooperation projects with Balkan countries. The questions of tolerance of differencies and inclusion of the underrepresented social groups have become the key topics of the project. On the basis of personal experience with specific prejudices of the Balkan folks I've worked out the directing concept for the puppet theatre performance with the elements of contemporary circus. In the atractive manner it introduces the healthy social values to children 5 - 11 years old. This thesis presents the reaction to the situation in the contemporary puppetry in the Balkans, explains the process of creative decision making and reflects the struggle for the financial support for the project.
Acoustic Emission and Nonlinear Elastic Wave Spectroscopy During the Fatigue Test of Aircraft Wing Main Spar Flange, Flange Joint, and Wing Lifting Eye
Převorovský, Zdeněk ; Chlada, Milan ; Krofta, Josef ; Farová, Zuzana
The report introduces the results of monitoring of crack initiation and growth during fatigue tests of the three airplane structure parts. The method of acoustic emission was used together with nonlinear elastic wave spectroscopy (NEWS) and nonlinear time reversal mirrors (NLTRM).
Nondestructive evaluation of concrete structure of the nuclear reactor cavity by nonlinear elastic wave spectroscopy (NEWS) : contract number-771318
Převorovský, Zdeněk ; Kudrna, P. ; Kober, Jan ; Krofta, Josef ; Chlada, Milan ; Chlada st., Milan
The structural health of two model samples of concrete shaft of nuclear reactor was non-destructively tested by three variations of nonlinear ultrasonic spectroscopy methods denoted as NWMS, SSM a TR-ESAM. The results of measuring procedures approved inherent nonlinearities of tested concrete compounds given by their inhomogeneity.
Localization and Identification of AE Sources by the Help of Time Reversal Mirrors
Převorovský, Zdeněk ; Krofta, Josef ; Chlada, Milan ; Farová, Zuzana
In this paper we suggest new concepts of more precise acoustic emission (AE) source localization and identification in komplex structures. The method is based on a Time Reversal (TR) AE signal processing. The new offline procedure, called TRAED (Time Reversal AE Deconvolution), is relativem simple and does not require any knowledge on the structure material and geometry.

National Repository of Grey Literature : 24 records found   1 - 10nextend  jump to record:
See also: similar author names
1 Krofta, Jan
1 Krofta, Jiří
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