František Šimčák

Methods for Verification of Safety of the Sluice Gates in Water Power Plants

Methods for Verification of Safety of the Sluice Gates in Water Power Plants The aim of a paper is to show theoretical and experimental methods that are used in the process of evaluation of safe operation of sluice gates in water power plants. On several examples are represented various treatments that allow to provide identification of locations of possible failures on carrying elements of sluice gates.

The Influence of Facet Size on the Accuracy of Modal Parameters Determined by Digital Image Correlation Technique

The paper deals with measurements of modal parameters using high-speed digital image correlation and assesses how the size of image elements (facets) influences the accuracy of modal parameters of the analyzed structure. The facet size is an important parameter that significantly affects the correlation process and its results. In the paper the experimental modal analysis of steel circular plate that has been excited by the impact hammer is described. Correlation system Q-450 Dantec Dynamics was used to measure the responses of the analyzed structure.

Identification of the Anisotropic Plastic Behaviour of Sheet Metals at Large Strains

The identification of the material properties in sheet metal is usually achieved using uniaxial tests performed along different texture directions. In this paper an experimental procedure to identify the plastic behaviour of sheet metals up to large strains using full field measurement is presented. The tests were conducted on notched specimens. That geometry generates a heterogeneous strain field which has been measured during the test using a digital image correlation system. The advantage of using an heterogeneous strain field in the identification procedure is that a complex state of stress–strain can be analyzed at the same time and much more information can be obtained in a single test. On the other hand the stress field cannot be directly computed from the test and a suitable identification procedure has to be developed. Here, the virtual fields method (VFM) adapted for large strains and plasticity has been used to identify the hardening behaviour and the anisotropy of the two materials. The values obtained with the VFM have been compared with the results coming from a standard identification made with uniaxial tensile tests.

The Knowledge Acquired by Using of Optical Methods by Strain Fields Investigation

These days are preferably used contactless optical methods for experimental investigation of strains and displacements, which give some information on whole investigated surface. In this contribution the optical systems working on electronic speckle pattern interferometry (ESPI) principle and digital image correlation (DIC) method are described. By using of ESPI and DIC methods the displacements and strains fields on chosen types of specimens are determined. Pros and cons of particular methods and influence of various factors on reached results accuracy are compared. There are also mentioned the possibilities of using of optical methods in application of devices on authors department.

Kinematic analysis of snake-like robot using obstacle aided locomotion

This paper deals with an obstacle aided locomotion of snake-like robot, which is the actual problem in the field of mechatronics. Because of many snakes using this kind of locomotion, the first step and hereby the most important is a kinematic analysis. The Denavit-Hartenberg convention was applied for this purpose. By this method the position vector components of each link according to basic coordinate system placed into any obstacle was assigned. Kinematic problem is a stepping-stone to the dynamic solution.

Design of Modifications for Constructional Elements of Manipulator Arm Aimed at Measuring of Operational Torque

There are often designed such constructional elements in the engineering practice that are specified for sensing of operational loading and for a precise setting of the individual components in the given technical device, for example components of a robot arm. Positioning of the robot arms is regulated by means of power output setting (or torque setting) of the driving parts (motors) predominately. Driving effect is transferred between the individual components by means of the connecting parts designed for transfer of force flow. There is described in this paper such design of modification for constructional element of the robot arm, which enables to perform measuring of torque in the joining parts of the robot arm during a current operation.

Possible Causes of Initiation of Plastic Deformation in the Containers Used in Food Industry

The containers used for fluid storage in food industry are during their operation exposed to processes that can potentially lead to the danger of possible overloading (pressure of protecting atmosphere, pressure of fermentation gas over must level, and so on). In the paper are analyzed possible causes of large plastic deformations of vessels that are used for must fermentation.

Balancing of Forces in Segments of Axial Bearing by Dynamometers

The Francis turbine in water power plant station is positioned at top and bottom axial hanging bearings. During reparation work the turbine was disassembled and during assembling the adjusting segments in the hanging bearings were released. In the paper are described procedures that are necessary in order to provide correct distribution of axial forces in twelve segments of upper axial hanging bearing by strain-gages applied on elastic pipes positioned under individual bearing segments.

Residual Stress Analysis in Containers for Transport of Radioactive Materials

During verification of safe operation of containers for radioactive waste is possible to use analytical, numerical and experimental methods of mechanics. Determination of residual stresses was one part of analysis. The residual stresses in container body can be induced during their production, overloading during operation, radiation or by thermal processes. In the paper are presented results from analysis of residual stresses in containers by using strain-gage hole-drilling method.

Strain and Stress Analysis around the Notches Using ESPI Method

Modern speckle optical methods use the properties of coherent light for identification of displacement fields. One of these methods is method ESPI. Using of this method strain and stress fields on surface of flat test samples with symmetric notches by tensile and shear loading were identified. A special fixture for shear loading of test samples was designed. The shape and dimensions of the fixture were modified on the basic results of experimental measurements. A modification allowed us to obtain a better analyse of strain and stress fields of test samples with symmetric V notches.