Solid State Phenomena Vol. 240

Abstract: The rules and capabilities of macro-strains identification method with the use of optical interference for identifying initial phase of plastic deformation process in steels with material instability were discussed in the work. It was also shown how the technique run in presentation of the initial phase of yielding progress. As the example for illustration of discussed method real capabilities the course of plastic deformations beginning in the tension tests of 15CrMo and 34CrNiMo6 steel samples was shown as well as the course of test of pure and simple bending for the steel 15CrMo beam. Namely, the sequence of interference fringes pictures showing the formation of plastic strains correlating to the points on the tensile test curve was presented. For bending process the pictures were correlated with the point on the graph of dimensionless bending moment versus maximal strain measured by the strain gauge

Abstract: The work presents recommendations related to the selection and installation of high power piezo ceramic rings dedicated to simultaneous power supply and data transmission for the purpose of extending life in their operation. Mechanical and electrical defects in piezoceramic elements of conical actuators were presented. The issue is important in the case when energy and information are transmitted at the same time using upper acoustic waves to autonomic wireless measurement nodes (WMN) in mechanical construction elements. A laboratory ultrasonic actuator was made and used to test ceramic rings. Additionally a dedicated vibration sensor was made and a measurement system for determination of frequency response of high power actuators was developed. Identification of the material used to make the ceramic rings and feeding electrodes was conducted. Next calibration tests of conical piezoelectric actuators were conducted and their defects were tested.

Abstract: The purpose of this research was to investigate the changing patterns of the 3D rail residual stress as it accumulates on different portions of the rail manufacturing process. These patterns are of interest for manufacturers and railroad companies but also could serve as initial fields for various further numerical analyses of actual residual stress states in rails, wear and crack formation/development. Examined were four rail samples taken directly from manufacturing: 1. an air cooled rail; 2. an air cooled and roller straightened rail; 3. a head hardened rail; 4. a head hardened and roller straightened rail. An advanced experimental-numerical hybrid technique was developed and applied to perform all the required data reduction tasks. It comprises of an sectioning scheme called as the transverse/oblique slicing (T/O-S) technique and of a physically reasonable data reduction/smoothing procedure called as the global method (GM). Destructive experimental examinations were performed with the neutron diffraction method on thin rail slices at atomic reactor facility of US DOC, NIST Center for Neutron Research in Gaithersburg, MD. In the paper presented and discussed are results of the performed analyses.

Abstract: The results of experimental research on a single span reinforced concrete beams are presented in the paper. The study was undertaken to explain some issues, amongst which the most important one was the recognition of strain distribution in the shear zone of RC beams. It was decided to adopt the modified Digital Image Correlation Method (DIC) and the software created by K. Suprynowicz to follow the surface deformations. This was the first application of the software to the concrete structures behaviour analysis. Hence, another aim of the study was to confirm the proper susceptibility and usefulness of this tool for further research on concrete elements. What’s more the scope of the software future development was defined, that would allow for observation of some particular phenomena characteristic for concrete, like cracking. Finally, the conclusion is presented, that application of the proposed variant of DIC method to concrete structures is promising, although for the recognition of shear strain distribution it requires increasing the accuracy by increasing spatial resolution of images and modifications of the software.

Abstract: This work presents testing mechanical defects of MFC piezoelectric transducers. The issue is important when piezoelectric transducer is used as eg. strain sensor. Repeatability of measurements is a goal, which can be obtained only if transducer has the same physical properties in every measurement. One way to determine damaged part of the sensor is measuring capacitance of MFC transducer. A couple of tests were performed to determine capacitance under non-destroying cyclic loading, and with loads causing PZT failure. Relation of capacity and load level was also investigated. All tests were validated with results from traditional resistive strain gauge

Abstract: This article presents paper deals with experimental verification of defect’s influence on the beam structures’ eigenfrequency extraction performed numerically with the ABAQUS Finite Element Analysis (FEA) software. The results for beams with defects were compared to those obtained for their undamaged (healthy) counterparts. The beams were made of aluminum and of a laminated glass-epoxy composite. The experiments confirmed the numerical results both quantitatively and qualitatively showing also some differences between the two materials.

Abstract: The paper deals with experimental estimation of the frequencies of free vibrations for composite plates with damage. Two different glass-epoxy composite plates with damage were tested and their mechanical behavior was compared with their non-damaged counterparts. Dynamical properties of the tested structures were examined with the Laser Scanning Vibrometer. Finite Element Analysis (FEA) was performed simultaneously for free vibration frequencies and mode shapes. The numerical results agreed well with the experiment.

Abstract: In this work, the mechanical state of the material is considered in the form of the oscillation of the molecule. The analysis is carried out for material without an external load and for material under the action of the mechanical load. These two states are tested in a Raman spectroscope where oscillations of molecule with modulations are induced by laser light. One should expect that the results of these investigations will confirm the capability of Raman spectroscopy in analysis of molecular mechanical state of material.This research is carried out using photoelastic material, and an analogy to state of stress on the continuum level is presented by photoelastisity.

Abstract: Application of the DIC (Digital Image Correlation) method for the analysis of crack initiation and propagation in RC beams reinforced by BFRP bars (Basalt Fibre Reinforced Polymer) is presented in the paper. Two dimensional, single camera DIC system was used to observe strain and crack distribution in such RC beams loaded using four point bending setup. BFRP bars have arose as an alternative to steel bars for RC (Reinforcement Concrete) members in aggressive environments. The low modulus of elasticity of BFRP bars lead on to large crack widths and, as a result, the design of BFRP Reinforced Concrete beams is often governed by SLS (Serviceability Limit State) criterion. Due to this it is necessary to explore specific crack propagation in concrete beams. Process of such beams degradation can be identified by comparison of strains and displacements obtained by DIC method, with the database of experiment results.