Jaroslav Smutny

STUDY OF METAL TIMBER JOIN BY ACOUSTIC EMISSION METHOD

Actual behaviour and general load carrying capacity of timber structures depends primarily on the load bearing capacity of joints. The present paper deals with slotted-plate steel-to-timber joints. In addition, innovative measuring methods were used to determine the strength of the metal-wood-metal structure. One of them was the acoustic emission method, which belongs to the group of non-destructive testing methods. It is to be noted that the acoustic emission method responds to the defect generation much sooner than the visual or any other method. The time-frequency analysis can play a central role in the signal analysis.

Nondestructive Testing of Advanced Concrete Structure during Lifetime

The paper reports on measurements and analysis of the measurements during hardening and drying of specimens using selected acoustic nondestructive testing techniques. An integrated approach was created for better understanding of the relations between the lifetime cycle and the development of the mechanical properties of concrete. Acoustic emission, impact echo, and ultrasonic techniques were applied simultaneously to the same mixtures. These techniques and results are presented on alkali-activated slag mortars. The acoustic emission method detects transient elastic waves within the material, caused by the release of cumulated stress energy, which can be mechanical, thermal, or chemical. Hence, the cause is a phenomenon which releases elastic energy into the material, which then spreads in the form of an elastic wave. The impact echo method is based on physical laws of elastic stress wave propagation in solids generated by mechanical impulse. Ultrasonic testing is commonly used to find flaws in materials or to assess wave velocity spreading.

Determine Parameters for Double-K Model at Three-Point Bending by Application of Acoustic Emission Method

As concrete is one of the most popular building materials, it is important to know its basic properties and behaviour especially at loading. When cracks occur in concrete, released fracture energy will be proportionally transformed into the energy contained in acoustic emission. According to this physical phenomenon, acoustic emission technique provides an effective monitoring method for fracture process of concrete through generated acoustic emission. However, such monitoring is limited in qualitative evaluation of fracture process in most occasions. Quantitative interpretation of fracture process is difficult to accomplish by simply acquiring the amount of acoustic emission generated or by conducting parameter-based acoustic emission analysis. This paper investigates the use of the double-K fracture model and acoustic emission for prediction of load at the beginning of stable crack propagation in three-point bending tests of concrete specimens. Double-K model combines the concept of cohesive forces acting on the effective crack increment with a criterion based on the stress intensity factor.

Application of Acoustic Emission Method and Impact Echo Method to Structural Rehabilitation

The paper is concerned with the technical aspects of the appraisal and retrofitting process of fire damaged reinforced concrete structures. The assessment of fire damaged structures is carried out along lines similar to those of the appraisal of existing structures. In practice, constructions are most often assessed by destructive tests in-situ and on core bore specimens. In addition to destructive tests, damaged structures are also assessed by non-destructive ones. The present paper shows the use of non-destructive methods of measurement using the acoustic-emission and impact-echo methods. Acoustic emission provides valuable data on the structural integrity of a material. This method has a significant potential to be used for in-situ monitoring and evaluation of the current state of structures. An impact-echo method is based on impact-generated stress waves that propagate through concrete and are reflected by internal flaws and external surfaces. Impact-echo can be used to determine the location and extent of flaws such as crack delamination, voids, honeycombing and deboning in plain, reinforced, and post-tensioned concrete structures. The paper presents a possible rehabilitation plan based on the potential results obtained by these non-destructive methods.

Evaluation of Acoustic Emission Events Generated at Three Point Bending of Different Concrete Specimens by Spectral Analysis

The paper aims to the determine of the mechanical properties of the concrete specimens at three-point bending test by application of the Acoustic Emission Method. Recorded acoustic emission events generated during three-point loading have been chosen. Some frequency and joint time-frequency methods are applied to these records. Time series as acoustic emission events may be analyzed in the time, frequency, and/or time-frequency domains. The selection is based on the type of the signal in question, on the type of analysis to be used or the result achieved. In many applications, direct evaluation of the time-amplitude representation is neither easy nor advantageous. The individual mixtures were different in cement dosage and water-cement ratio based on how much the amount of cement was increased while maintaining consistency S2 according to EN 206.

Analysis of Dynamic Parameters of Rail Fastening by Born-Jordan Transformation

The method using Born-Jordan transformation has been developed for the evaluation of response signals obtained by rail fastening analysis. In the paper the laboratory measurements and dynamic parameters analyses of flexible fastening of Vossloh SKL14 type have been descripted. This method can also be used for designing new fastening systems and their parts, for comparison of various rail fastening types and so on.

Evaluation of the Railway Substructure in the Turnout with the Movable Frog by Help of Decomposition

The aim of the paper is focused on the analysis of the stress measurement in the railway substructure in the turnout with the movable frog prototype designed for a high speed. The evaluations were compared the measurement and the results obtained with theoretical presumptions. The Discrete Wavelet Transformation for the decomposition of the stress measurement and its evaluation is described. Two sections in the turnout with the movable frog were used for the measurement and signal analysis.

Three-Point Bending Test Evaluation of Concrete Specimens by Non-Traditional Analysis of Acoustic Emission Method

The aim of the paper is focused on the analysis of the mechanical properties of the concrete specimens with plasticizer at three point bending test by the signal analysis of the acoustic emission signal. The evaluations were compared the measurement and the results obtained with theoretical presumptions. The Joint Time Frequency Analysis applied on measurement data and its evaluation is described. It is well known that the Acoustic Emission Method is a very sensitive method to determine active cracks into structure. However, evaluation of acoustic emission signals is very difficult. A non-traditional method was used to signal analysis of burst acoustic emission signals recorded during three point bending test.

Experimental Determination of Wheel and Guiding Forces on the Tracks

Force interaction between a railway track and a vehicle affects the safety, comfort, and last but not least, economical maintenance. Train of wagons incidence on track in both transversal and vertical direction is simplified by qualifying of force wheel (FQ), guiding (FY) and perpendicular and transverse acceleration. An experimental basis for dynamic determination of vertical, FQ, and lateral, FY, forces at the wheel using strain measures in the foot of the rail is given. Measurements of the dynamic forces during passing train are normally very costly and uneasy. These method consists of measuring strains at selected points of the rail profile is very simple and therefore interesting.