Vol 54, No 4 (2018)

Applying ultrasonic-tomography systems makes it possible to precisely determine the shape and dimensions of flaws with the aim of establishing the degree to which the flaws influence safe operation of tested objects. This problem is solved by using special algorithms that make use of echo-signals recorded by an ultrasonic transducer to generate synthesized images of flaws in the sample. The use of phased arrays in ultrasonic tomography is explained by their ability to provide exhaustive data about the internal structure of a test object, thus allowing formation of the high-quality synthesized images of flaws in the object. Increasing the speed of ultrasonic tomography by using phased arrays necessitates the development and implementation of fast data-processing algorithms. In this connection, of interest are calculation algorithms in the frequency domain, which ensure the high speed of producing synthesized images. An ultrasonic-tomography algorithm is proposed that is based on calculations in the frequency domain. The algorithm takes the complex nature of the propagation of ultrasonic waves into account and is connected with the presence of media with different acoustic properties (e.g., in the case of immersion tests). Possibilities offered by the algorithm are investigated by computer simulations using the licensed CIVA 2016 software package and experimentally.

Results of the strength tests of an aircraft wing spar made of Toray T1000 carbon fiber-reinforced plastic are presented. Construction failure zones have been inspected by the methods of acoustic emission (AE) and tensometry. Loading-induced changes in the stress-strain state (SSS) of wing-spar material have been analyzed. The coordinates of AE signal sources that correspond to the separation of the upper spar cap from the spar web have been determined. Algorithms for AE-data processing using wavelet transforms are considered. Connections have been established between changes in stresses emerging in CFRP material, AE signal structure, and the occurrence and propagation of spar fracture.

Nowadays the method of the longitudinal critical refraction wave (L_CR wave) is an effective method to nondestructively measure the on-line stress in the huge steel structures. The present study and research of the method of L_CR wave are mainly focused on measuring the residual stress in the steel structures, in contrast to the few research findings related to the on-line stress measurement in steel structures (including the elastic and plastic deformation). Based on the Acoustoelastic effect, the L_CR wave stress measurement system is built to measure the change of time of L_CR wave propagating, stress coefficient and the energy of L_CR wave in A36 steel test specimens from the elastic deformation to the plastic deformation. The conclusion is: At the free-stress condition, the flight time of L_CR wave and stress coefficient show an obvious change between the elastically deformed test stage and plastically deformed stage. The change of flight time and the intensity attenuation of L_CR wave show a turning point, when the specimen undergoes the process from elastic deformation to plastic deformation. And the extent of plastic deformation in the steel structure can be evaluated by the extent of intensity attenuation of L_CR wave. The experimental method will be showed in this paper for measuring the extent of plastic deformation in the steel structures in service on construction scene using the L_CR wave method.

The increasing application of automotive aerospace materials, such as Magnesium alloys and Aluminum alloys is challenging the joining processes of dissimilar metals and alloys. Friction Stir Welding (FSW) being one among the recent research novelty area on the material joining processes. This paper involves to study the influences of post weld treatment of Aluminum AA6061 and AZ61 through Non Destructive Testing (NDT) methods. The FSW butt joints are post weld heat treated with three different temperatures (100, 300 and 400°C) and aged for 1 hour, three hours and five hours periods. Its effects are analyzed by the study of eddy-current test, micro hardness evaluation and Scanning Electron Microscopy (SEM) analysis. The analysis infers that the aging period also plays a major role as that of temperature in the improvement of joint efficiency. A satisfactory correlation exists between the eddy-current test’s impedance values, micro hardness values and SEM analysis.