No 10 (2024)

In ultrasonic flaw detection, lateral cylindrical drillings are traditionally used to adjust and check the parameters of equipment. Other volumetric reflectors, such as vertical drillings or spherical pores, are rarely used. This article notes that such models of internal and surface defects of welded seams are convenient to use and easy to manufacture. For a long time, a limitation to the use of drillings for modeling in ultrasonic flaw detection was the use of these effects not only on defect models in the form of noise associated with the diffraction effects of elastic waves running around cylindrical cavities. It is noted that these effects are currently well studied and are used to identify the type of defects and measure their sizes. Based on the results of experiments on observing the scattering of longitudinal waves and transverse waves with different polarization on cylinders and spheres, typical examples of the manifestation and use of these diffraction effects are given. The expediency of using not only drillings, but also spherical pores is noted. Experiments of the ultrasonic waves scattering on pores are performed on transparent glass samples for clarity. Comparative data on the manifestation of diffraction effects on various volume cavities are presented. In particular, it is noted that there is a focusing of signals enveloping spherical pores. Limitations on the duration of ultrasonic wave pulses are noted, at which diffraction signals can be used to increase the information content when detecting defects. It is recommended to expand the use of 2 mm diameter side drillings in samples to adjust sensitivity during ultrasonic testing using the echo method.

Magnetic phase transformations in the Curie temperature region of a ferrite material with the composition Ni_0,4Zn_0,6Fe₂O₄ were studied using thermomagnetometric analysis and methods for recording the temperature dependence of the initial magnetic permeability μ₀(T) and electrical resistivity ρ(T). The description of the equipment utilized and the key characteristics of the application of the experimental methods under review are provided. During thermomagnetometry at the cooling stage, it was found that the temperature at which the material completes the transition to the ferrimagnetic state corresponds to the inflection point temperature on the µ₀(T) curve and the breakpoint on the lnρ(T) plot. The established interaction between the parameters of transients can be useful for more correct determination of the Curie temperature in ferrites.

Sulfur is a substance with an abnormal dependence of viscosity on temperature. An experimental setup was created to study the viscosity of sulfur at pressures up to 100 bar and temperatures up to 500 °C. To visualize the process of falling of a tungsten carbide ball located in molten sulfur, the proton radiography method was used. The experiment was carried out on a PRIOR-II proton microscope (Institute for Heavy Ion Research, GSI, Darmstadt, Germany). In this experiment, the operating mode of the SIS-18 accelerator with slow beam extraction was used for the first time for proton radiography. The viscosity of the sulfur melt was measured at a pressure of 90 bar and temperatures of 190—320 °C. It has been shown that the viscosity of sulfur is greatly influenced by impurities, including hydrogen sulfide, which appears in the molten sulfur at high temperatures.

Experiments were conducted on certain types of combustible building materials and wood-based structures to determine the interaction between firebrands and forest fuel (FF). Using non-contact IR diagnostic methods in narrow spectral ranges of infrared wavelengths, the heat flux values generated by firebrands and the temperature field of the most heat-stressed sections of the structures under study were determined. Using a JADE J530SB thermal imager with an optical filter of 2,5—2,7 m, temperatures in the range 310—1500 K were measured in the infrared region. In order to interpret the recorded emission from the test sample, calibrations supplied by the narrowband optical filter manufacturer were used.