Applied Mechanics and Materials Vol. 611

Abstract: 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.

Abstract: Procedures for residual stress evaluation by using Ring-Core method have not been standardized. Most common techniques are derived from the ones used for similar semi-destructive hole-drilling method. The differences between research approaches can cause significant errors. New approach using neural network is proposed as a more adaptive way for residual stress evaluation than the commonly used methods.

Abstract: A necessary procedure for the evaluation of reliability and durability of supporting steel structures is an identification of critical points with the stress contractors because the critical areas are decisive with regard to location of supporting structure damage or loss of functionality. The identification of critical points can be performed by means of various methods. The full-field optical method can be found among the most often used ones. In this article there is presented an application of the transmission photoelasticimetry at the full-field stress analysis of the selected construction elements.

Abstract: This paper presents the approach to improve localization based on GNSS. The principles of the GPS localization and impact of the DOP parameter on localization error are mathematically analyzed. The algorithm based on the use of DOP parameter and Kalman filter for the improvement of the localization accuracy suitable for small scale outdoor mobile robots and other outdoor applications is proposed. The applicability of the proposed methodology was verified by performed experiments with two common cheap miniature GPS modules and accurate high-end GNSS receiver used as a reference frame for the measurements. The obtained results affirmed the improvement of the localization accuracy.

Abstract: The development of manufacturing technology is mostly given by economics, environmental trends and the development of cutting materials and machine tools. Manufacturing is a significant part of the worldwide economy. Machining (material removal processes) represents major part of production costs. This paper yield inquiries into the hard and precise milling with a focus on force effects in experimental machining, tool wear and final surface qualities (roughness, micro hardness). The precision machining of hardened steel differs from conventional machining in terms of the hardness of the workpiece materials and the cutting tool materials that are required. Hard materials are characterized by high hardness (> 45 HRC) and abrasiveness. Machining processes require cutting tools of much higher hardness and also higher resistance of the abrasive wear. Recently developed cubic boron nitride (CBN) and coated sintered carbides cutting tools are considered to have the ability of cutting such as steel. CBN cutting tools show good performance during machining of the hardened steel because of their hot hardness and good fracture toughness.

Abstract: In the contribution an experimental modal analysis of the manipulator arm on the mobile chassis is described. For an assessment of modal parameters the conventional mechanical transducers of acceleration were used. The natural frequencies as well as the magnitudes of displacements were investigated at two different static robot modes – without stabilization of the chassis and with stabilization of the chassis, respectively. The measurements were also performed by the simulation of robot effector loading.

Abstract: Spectometers are specified and classified according to extent, differentiation ability, sensitivity (permeability), dynamics, dimensions, construction and software. Manufactures supply series of more or less universal spectometers and, moreover, it is possible to suggest and to use specially assembled and adapted device for the majority of special applications. The use of spectometers in the field of mechatronic systems, which are comprising principles and bases of mechanical engineering, control systems, electronics and informatics, is indisputable and it holds important position especially in the chemical analysis of metal and metal materials area, in the control of chemical ingredients of materials, identification of alloys, qualities and material standards, manufacture process control inclusive of material identification – PMI, QC, QA both in internal section and in external material production section, where there in a horizontal integration.

Abstract: 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.

Abstract: The aim of this article is to present the influence of stochastic pattern on results accuracy of digital image correlation method in plastic areas. The various types of stochastic patterns were applied on testing specimens which were then tensioned. There was correlated the intensity of black and white color (denoted as grey value) dispersed on a specimen, then the mean value of estimated error for unloaded state as well as state of highest measured deformation and finally the amount of non-correlated facets. Also the maximal deformation of specimens was compared by which the damage of stochastic pattern emerged.

Abstract: 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.