Eddy-Current System for Testing Inner Diameter of Pipes

We propose a method for eddy-current testing of the inner diameter of electroconductive pipes. The design of an eddy current transducer is described, as well as an algorithm for converting measurement information signals and the block diagram of a system for testing the inner diameter of pipes that allows testing under conditions of significant radial displacements of the eddy current probe inside the pipe. The effectiveness of the proposed engineering solutions is evaluated.

     

Use of Emulsion Explosives in Experimental Studies of Flows in the Bonding Zone in Explosive Welding

Bonding of steels of different hardness through a ductile layer was obtained by explosive welding using an emulsion explosive. In the bonding zone, two types of waves were found: large waves and small waves which have not been observed in previous experiments. Empirical relations for calculating the wave size are proposed that take into account the influence of the strength and density of the colliding materials on them. Cracking in the bonding zone can be avoided by reducing the wave size.     

Deformation Anisotropy of <Emphasis Type="Italic">Y</Emphasis> + 128°-Cut Single Crystalline Bidomain Wafers of Lithium Niobate

Bidomain single crystals of lithium niobate (LiNbO₃) and lithium tantalate (LiTaO₃) are promising materials for use as actuators, mechanoelectrical transducers, and sensors capable of working in a wide temperature range. One need to take into account the anisotropy of the properties of the crystalline material when such devices are designed. In this study we investigated deformations of bidomain round shaped Y + 128°-cut wafers of lithium niobate in an external electric field. The dependences of the piezoelectric coefficients on the rotation angles were calculated for lithium niobate and lithium tantalate and plotted for the crystal cuts which are used for the formation of a bidomain ferroelectric structure. In the experiment, we utilized an external heating method and long-time annealing with the lithium out-diffusion method in order to create round bidomain lithium niobate wafers. Optical microscopy was used to obtain the dependences of the bidomain crystals’ movements on the rotation angle with central fastening and the application of an external electric field. We also modelled the shape of the deformed bidomain wafer with the suggestion that the edge movement depends on the radial distance to the fastening point quadratically. In conclusion, we revealed that the bidomain Y + 128°-cut lithium niobate wafer exhibits a saddle-like deformation when a DC electric field is applied.     

High-symmetry DC SQUID based on the Nb/AlO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/Nb Josephson junctions for nondestructive evaluation

Topology of high-symmetry thin-film SQUIDs based on the Nb/AlO _x /Nb tunneling junctions is developed and optimized. The devices exhibit relatively low sensitivity to static external field and electric interference. An experimentally implemented SQUID sensor with an integrated input coil with a sensitivity of 0.26 μA/Ф₀ exhibits an intrinsic noise with respect to magnetic flux of less than \(5\mu {\Phi _0}/\sqrt {Hz} \). A system for encapsulation of sensors is developed for applications in multichannel systems for nondestructive evaluation of materials and alternative diagnostic systems.