PSI - Issue 13

Tretyakov M.P. et al. / Procedia Structural Integrity 13 (2018) 1720–1724 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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Tensile tests at room temperature with the joint using of the universal servohydraulic biaxial test system Instron 8850 and noncontact 3D optical system for analyzing displacement and strain fields of Vic-3D were carried out. Test system allows providing tension-compression tests with loads is 100 kN and torsion tests with maximum torque is 1000 N ∙ m in quasistatic or cyclic regime with frequency up to 30 Hz. The load in the tests was recorded by the Instron Dynacell load cell with an accuracy of no more than 0.4 % of the measured value. The stretching, deformation and diameter changing of the specimens in the test part during necking effect were measured due to the video system data. The estimation of the accuracy of data recording by used video system was considered in [Tretyakova et. al (2011)]. Installation of the test equipment is shown in Fig. 1. The 3D optical system Vic-3D based on the digital images correlation technique, consist of two CCD cameras (c), illumination system (d), calibration grids (e), synchronization module (f) and specialized software for acquisition, processing and analyzing images. Data synchronization of test machine controller and video system were realized during the testing. The registration of the displacement and strain fields was done with the high-resolution cameras Prosilica, with recorded frequency of 2 Hz, with set resolution of 16.0 MP.

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a f Fig. 1. Biaxial test system Instron 8850 (a), installation of equipment for carrying out tension tests with using 3D digital video system Vic-3D (b), which consist of two CCD cameras (c), illumination system (d), calibration grids (e) and synchronization module (f). 3. Test procedure Uniaxial tension tests with different strain levels at the postcritical deformation stage (after necking effect) were carried out. There were realized three deformation levels before the beginning of unloading. Achieved parameters are presented in the Table 2, which contains the engineering strain values ε , engineering stresses σ and corresponding values of the coefficient of realization of the postcritical deformation stage       1 / 1 / P P B P B k P P , possessing the following values of   0 1 P k . Parameter values achieved at failure of specimen are presented too. The transition of the deformation process to the postcritical stage is corresponded to achieve the ultimate stress (   760 MPa B ,   0.1 ). Table 2. Characteristic of levels of postcritical deformation achieved at the beginning of unloading and at failure. Deformation levels ε, mm/mm σ Р , MPa k Р Level 1 0,136 730 0,04 Level 2 0,171 650 0,15 Level 3 0,194 580 0,24 Failure 0,216 500 0,34 c d e