Miroslav Pástor

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.

Implementation of Correction Coefficients Relevant for Photoelastic Coatings into the PhotoStress Software

Optical experimental method PhotoStress is based on the principle of birefringence that occurs on photoelastic coatings on the surface of an object subject to examination. However, photoelastic coating strengthens the examined surface; hence, strains that co-occur in the analysed object exhibit lower values than when no coating is applied. This is the reason for the implementation of relationships for correction coefficients into the PhotoStress software which is now being designed. These coefficients are supposed to eliminate discrepancies in gained values resulting from the impact of stiffness through applied photoelastic coating. Into the PhotoStress software were implemented correction coefficients for plane stress CPS, one-side coated objects under bending stress CB, two-sides coated objects under bending stress CB2, shaft rotation Ct and pressure vessels CN. The following paper includes explanations of particular types of corrections which were implemented into the PhotoStress software.

The Use of Optical Methods in the Analysis of the Areas with Stress Concentration

Abstract Anchoring parts of technical systems are often damaged due to the heavy forces acting on these systems during their operation. For that reason, various modifications are suggested and created on the anchoring screws, which should help to reduce the mechanical stress values in a place of the first load-bearing thread of a female screw. For the determination of stress fields on the surface of a plane model of a threaded joint, two non-contact optical methods were used – conventional transmission photoelasticimetry and modern digital image correlation.

Proposal of Methodology for Determination of Stresses around Groove by Photo Stress Method

The aim of the paper is to propose a new methodology for verifying residual and operational stresses, determined by the drilling method. The newly proposed methodology will be based on the use of optical methods for total surface deformations and stress analysis through optically sensitive material applied to the surface of the object being investigated.

Nonlinearity in Oscillations of Large Displacement Pendulum

In this contribution a theoretical basis of pendulum oscillations is described. The authors deal also with an experimental investigation of nonlinearity in oscillations of large displacement pendulum. High-speed correlation system was used for the registration of pendulum free motion. The obtained data were consequently processed in Matlab and depicted in a form of graphical visualizations and tables.

Possibility of Using of Tensometry in Deformation Analysis in Areas With Sudden Change of Geometry

In the process of design of machines and equipment high attention has to be given to structural notches, defects of materials and surface quality, because they have high impact to their fatigue strength. In the paper is presented proposal of methodology concerning deformation analysis near stress concentrators by using strain gages. The experimental measurement was realized on bended U-shape specimen with notches. The results gained by experimental measurements were verified by numerical modelling by the finite element method.

Stress Analysis Performed by Photoelasticity and Digital Image Correlation

This paper deals with the use of classical experimental technique of photoelasticity as well as modern one – digital image correlation by stress analysis. Both mentioned methods were used to compare the corresponding stress fields obtained on a sample with stress concentrators loaded by bending. The paper contains the basic principle of photoelasticity, methodology of static analysis with polariscope and briefly describes the measurement with low-speed digital image correlation system. Taking into account that the used correlation system does not allow to evaluated stress fields, calculation and visualization of stress fields were realized in program Q-STRESS v.1.0 developed at the authors department.

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.