No 7 (2024)

The work investigated the effect of fatigue failure on the elastic characteristics of metastable austenitic steel AISI 321: Poisson’s ratio and acoustic anisotropy parameter. The elastic characteristics were calculated using ultrasonic measurements of the propagation time of longitudinal and shear elastic waves. The volume fraction of strain-induced martensite was determined by the eddy current method. Theoretical studies have shown that the main factors influencing Poisson’s ratio are the accumulation of microdamages and changes in phase composition. The change in the acoustic anisotropy parameter is associated with the influence of cyclic deformation on the crystallographic texture of the material matrix and the formation of oriented crystals of strain-induced martensite. Based on the analysis of experimental results, expressions were obtained for calculating damage and relative accumulated plastic deformation based on acoustic measurement data, which are widely used in engineering practice to determine the fatigue life of structural materials.

Formulas for calculating of the resulting magnetic field strength of magnets with a given magnetization distribution or given field of external sources are presented. We have collected exactly those cases where a user who does not have much experience in the field of computational mathematics and programming can perform calculations using these formulas. Namely, in these cases formulas for tension are mostly expressed in final form through elementary functions or require the use of one of the standard subroutines available in the library of any programming language. Such formulas can serve both as reference material and for solving corresponding problems with suitable real objects, as well as for determining optimal strategies and the optimal set of input parameters when using universal software packages and assessing the error of the results obtained.

The paper presents the results of experimental and numerical investigations on water ingress trapped in aircraft honeycomb panels. The ingress of atmospheric water during aircraft service may cause minor or major damages of airplane crucial components. The percentage of water/ice filling honeycomb cells is an important factor related to possible cell damage. This study is focused on the analysis of the following inspection parameters: 1) influence of panel orientation (horizontal, vertical and Inclined at 30, 45 and 60°) on the efficiency of water detection, 2) efficiency and optimization of a heating technique in evaluating water ingress, 3) influence of water/ice phase transformation on detectability of water ingress.

The numerical analysis was conducted by using the ThermoCalc-3D software in order to evaluate the detectability of water ingress in the cases where a test panel is placed in different spatial orientations. The samples with water and ice were tested and analysed by using several data processing algorithms available in the ThermoFit software to enhance water detection performance. The signal-to-noise ratio concept was used to compare efficiency of image processing algorithms in the inspection of water ingress in honeycomb panels with varying water content, spatial orientation and water/ice phase transformation.

A procedure has been proposed for determining the concentration of lithium in formation waters using NMR relaxometry. The method allows to determine quickly lithium content at concentrations of industrial interest. Experiments showed good agreement of the proposed method with the inductively coupled plasma (ICP) method.

The optically stimulated luminescence (OSL) and the separation efficiency of the neutron and gamma components by OSL outputs were studied for samples of anion-deficient corundum (α-Αl₂O_3-δ) in ceramic and single-crystal forms with various neutron converters. For OSL dosimetry in mixed gamma-neutron fields, a detector material synthesized using ceramic technology consisting of a mixture of OSL active α-Αl₂O_3-δ and neutron-converter ⁶LiF powders in a ratio of 7:3 was selected as a promising one. The lower limit of the individual dose equivalent for such material under neutron irradiation does not exceed 30 μSv, and the dose dependence is linear up to 1 Sv.

To identify the zones with the highest tensile stresses and deformations, a two-parameter magnetic method based on the measurement of coercive force and residual magnetic induction was applied. For realization of the method a mobile hardware and software complex DIUS-1.21M with an electromagnetic U-transducer was used, which was located along the pipe axis and along the pipe ring. Measurements were carried out on three pipes: in the first one magnetic characteristics were measured in the absence and under the influence of internal pressure; in the second and third ones — before the test and after the pipe fracture. It was revealed that internal pressure leads to the growth of residual magnetic induction in all zones both along the axis and along the ring, which indicates the occurrence of axial and circular tensile stresses in these zones, and the change of coercivity occurred ambiguously. It was found that fracture significantly increases the scatter of magnetic characteristics, which is explained by the complex nature of the stress-strain state of the fractured object.