Issue 46

V. E. Wildemann et alii, Frattura ed Integrità Strutturale, 46 (2018) 295-305; DOI: 10.3221/IGF-ESIS.46.27 298 Figure 2 : Experimental set-up with the Instron 8850 biaxial servo-hydraulic testing system (1), the DIC measurement system Vic-3D (2) and the infrared system Flir SC7700M (3) . As an example, Fig. 2 shows an image of the relative arrangement of the test and recording equipment. It should be noted that the synchronization of optical recording systems with the test system controller during the test was carried out by means of the Analog-to-Digital Converter unit (NI USB-6251). M ECHANICAL TESTING . Procedure of defect identification efore carrying out mechanical tests of the specimens with technological defects of the “delamination type”, it is necessary to determine the location and geometric parameters of the defects. The method of identifying the technological defects is based on using the method of active infrared thermography [26]. The tested specimens were heated with the incandescent electric lamp with the intensity of 150 W during 10 seconds at a distance of 0.1 m. During the heating, the temperature fields were recorded with the FLIR SC7700M thermal imaging system. Fig. 3 shows the analysis results of inhomogeneous temperature fields illustrating internal defects in specimens. The temperature field is given in the values of the temperature change, where the value of T  is obtained by subtracting the first frame from a series of images obtained during the imaging. The use of this method made it possible to visualize the configuration of the internal defect, and also to register and evaluate the defect displacement relative to the center of the working part of the specimen (Fig. 3, b). Tension with torsion testing of specimen without defects Mechanical testing of blade specimens without defects were made under proportional tension with torsion with different ratios of the given displacement and the torsion angle in the range of 0 0.083 k   . The following ratio 0.028 k  was chosen to carry out further studies of specimens with an internal defect. With this relation, great values of both the tensile force and the torque are achieved. Fig. 4 shows the curves of the “load-displacement” and “torque-torsion angle” dependences according to the built-in sensors of the test system, obtained with the selected ratio u/  . As an example, Fig.4 (b) shows the image of the specimen after testing. It is worth mentioning that the macrofracture of the tested specimens took place in the gripping part under the axial load of max 48.2 P  kN and torque max 72.2 M  nm. B