The article presents a study of the evaluation options sag / temperature / tensile stresses in the conductors of the OHL on the basis of diagnostics of mechanical properties of the tension tower or angle tower. It comes to so called indirect approach of the determination of overhead lines ratings aided by actually measured the vibrations of the observed tower, and on the basis of these measurements the changes of tensile loads in conductors. From this information it is possible to calculate the average temperature of the conductor in the span and sag, respectively. In the paper are treated data, which are extracted from the field research on the angle tower number 111 at the overhead line 220 kV Podlog - Obersielach (Austria), which has a maximum angle of route. This tower can be an indicator of changes in sag of conductor in both neighbouring spans. It has been found that both its fundamental frequency there are in the range of 4.8 to 5.2 Hz as well as 13.3 to 13.6 Hz. Both their frequency are relatively close to one another. The character of these frequencies is derived from a similar method of loading, which is close to the bending and bending threaded loads. For more precise conclusions the results of the measurements, it is necessary to do measurements with swinging the tower as well as with different conductor's spans. It is obvious that in this case the natural frequency and deformation would be changed. The determination of changes in the frequencies and deformities of towers in the changing boundary conditions, such as the current flow intensity and temperature of the conductor presents a subject of ongoing research.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 17013270A welded joint is a typical example for a material inhomogeneity: Global differences in the mechanical properties appear between base metal, heat affected zone (HAZ), and weld metal(s). In addition, local variations of the mechanical properties, a so-called local mis-match, can appear between the different passes of a multipass welded joint and even within a single weld pass. This local mis-match occurs as a consequence of metallurgical and re-heating processes during multipass welding which yields different microstructures. Therefore, the yield stress, y, the strain hardening exponent, n, and the elastic modulus, E, exhibit global and local variations within a welded joint. Macro inhomogenous weld metals have been welded by half undermatch and half overmatch consumables. The aim of work is to apply the configurational force concept as an engineering tool for estimating the near-tip crack driving force (CDF) for different locations of the crack tip within the welded joint. Local variation of CDF depends on distance between crack tip and fusion line of two weld metals and crack propagation direction from overmatch-to-undermatch or undermatch-to-overmatch weld metal. The reason is that the material inhomogeneity induces an additional crack-driving force term, called the material inhomogeneity term, which leads to a shielding or anti-shielding of the crack tip. As a consequence, the local near-tip CDF becomes different from the nominally applied far-field J-integral value. The experimental investigation includes fracture mechanics tests of standard bend specimens machined from the inhomogeneous welded joints with varying distances between the crack tip and the perpendicular fusion line of the different weld materials. The numerically obtained results of the near-tip CDF and nominally applied far-field J-integral value are used in order to explain the fracture behavior of specimens with fatigue pre-cracks in the middle of inhomogeneous welded joint.
B.04 Guest lecture
COBISS.SI-ID: 16995862