František Trebuňa

Determination of the Necessary Geometric Parameters of the Specimen in Ring-Core Method

There are several measuring techniques for determining residual stress which can be divided according to the created damage in to the construction in non-destructive, semi-destructive and destructive ones. One of the most common is semi-destructive hole-drilling method. This paper deals about Ring-Core method which is based on the similar principles. Today, there is no standard for the Ring-Core method, thus it is important to consider various influential factors. One of them are the dimensions of specimen. Calibration coefficients are determined by finite element (FE) analysis using the commercial software Solidworks. These coefficients are used for residual stress evaluation by incremental method used in Ring-Core method. The influence of different specimen dimensions on the accuracy of the evaluated residual stresses is considered.

Methodology of contact stress analysis of gearwheel by means of experimental photoelasticity.

The subject of this paper is the analysis of contact stresses that occur between the teeth of a gear. The analysis was carried out by means of reflection photoelasticity, which is an experimental method rarely used in this field. Contact stresses assessed in the experiment are compared with values assessed through an analytical calculation while using the Airy stress function or Hertzian relations.

Further Possibilities of Using Software PhotoStress for Separation of Principal Normal Stresses

Further Possibilities of Using Software PhotoStress for Separation of Principal Normal Stresses Software PhotoStress, elaborated in our laboratories allows determination of directions and magnitudes of strains or principal normal stresses in loaded photoelastically coated structural elements. It allows accelerating process of measurement and evaluation of deformations or stresses in point, along line or along curve, respectively. In those entities can be determined directions, and magnitudes of differences and separated principal deformations or stresses on the basis of photography of loaded photoelastically coated objects. In the paper is given procedure for of evaluation of separated principal normal stresses by using of separation methods: method of difference of shear stresses with using separation strain gage and method of oblique incidence.

Concept of Locomotion Mobile Undercarriage Structure Control for the Path Tracking

The article deals with the proposal structure of undercarriages mobile robot GTR 2010 control. Functional model of the undercarriages mobile robot GTR2010 should be able to carry out active tracking of desired path for achieving a goal and get over obstacles in unstructured environments.

Application of the harmonic star method in photoelastic separation of principal stresses.

This paper deals with automation of an experiment process by means of photoelasticity on the condition that only information which was previously collected by identification of isochromatic fringes is used. The analysis of this issue pointed to Poissons and Laplaces equations. These equations were solved through the harmonic star method. The automation of an experiment was based on the development of a noncommercial program for processing of data which had been collected during photoelastic measurements. In addition, the program was used for verification of these measurements and comparison of measurement outcomes with results which were gained by the finite element method (FEM). Such a program enabled us to measure stresses in a certain point of the examined surface and, at the same time, separate these stresses, that is, determine the magnitude of individual stresses. A data transfer medium-a camera-was used to transfer the picture of isochromatic fringes directly into a computer. The chosen procedure of solving and evaluating the experiment provided us with reliable outcomes comparable to results gained by FEM.

Kinematics of Self-Reconfigurable Robotic System

Kinematics of Self-Reconfigurable Robotic System Theory of mechanisms with variable structure in robotic applications self-reconfigurable structures is one of the directions of development of robotics. On our faculty is developed self-reconfigurable modular robotic system capable of rebuilding a structure according to the requirements of the current task. To perform kinematic changes of its structure we needs to have information on where to find the modules and their submodules. Therefore it is necessary to know the mathematical relationship between the positions of its individual parts. Spatial kinematic chains is investigated based on the theory of simultaneous movements, where the position of each member is specified in the global coordinate system using local coordinate systems associated with individual members. To identify the position of the individual local coordinate systems were used transformation matrix, the accuracy of which is verified in mathematical programs and results from these programs are then compared with results of movement analysis notified by simulation procedures.

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.

An inspection of pipe by snake robot

The article deals with development and application of snake robot for inspection pipes. The first step involves the introduction of a design of mechanical and electrical parts of the snake robot. Next, the analysis of the robot locomotion is introduced. For the curved pipe, potential field method is used. By this method, the system is able to generate path for the head and rear robot, linking the environment with obstacles, which are represented by the walls of the pipe. Subsequently, the solution of potential field method is used in inverse kinematic model, which respects tasks as obstacle avoidance, joint limit avoidance, and singularity avoidance. Mentioned approach is then tested on snake robot in provisional pipe with rectangular cross section. For this research, software Matlab (2013b) is used as the control system in cooperation with the control system of robot, which is based on microcontrollers. By experiments, it is shown that designed robot is able to pass through straight and also curved pipe.

Influence of Material Structure and its Properties on Predicting Life of Pressure Pipelines

Pressure pipelines belong to the group of technological carrying structures that are designed in accordance with Standard Eurocode 3: STN EN 1993: Design of steel structures. These standards are used also later in the stage for assessment of failure states and fatigue life. Standard Eurocode 3: STN EN 1993-4-3 establishes the requirements for material properties of pipes and welds, associated with mechanical properties. A serious problem in estimating fatigue life of structure is the consideration of gradual degradation. The article also discusses the analysis of fatigue failure of the pressure pipeline, where it was found that the initiation of fatigue failure occurred in the area of poor weld. The further spread of the crack then occurred in the base material of the pipeline.

Operational Safety of Compressor Station Pipeline

Failure of pipeline system can endanger human lives and cause serious damage; therefore it is necessary to check it in terms of strength and life reliability. Inspection was performed on compressor station pipeline, where in terms of resistance to brittle failure it was discovered, that the weakest point of the pipeline is the weld. At lower temperatures danger of brittle failure of weld joint can arise. To assess the strength of the pipeline in investigated cross-section, with respect to state of plane stress, strength theories were applied. Values of reduced stresses were assigned based on main normal stresses resulting from experimentally set components of state of plane stress. Fatigue assessment was done, based on currently valid standards.