PSI - Issue 17

V.P. Matveenko et al. / Procedia Structural Integrity 17 (2019) 363–370 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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accuracy of calculations, numerical results were obtained with regard to their convergence with increasing number of elements. Figure 3a shows the distribution of strains y  on a large shelf of the specimen. According to the considered technique, the results of numerical simulation were used to select the locations of the sensors, which are shown in figure 3b. Here sensors 1, 2 and 5 are located in the strain gradient zone, which is the ridge of the specimen. The sensors 3 and 4 are located in the zone of uniform strain field, the value of which does not depend on the stress concentrator.

Fig. 3. Numerical results of strain distribution (a); sensor location scheme (b).

In the experiments, the fracture of the specimens was achieved by two modes of stepwise load variation with time (figure 4). It should be noted that with loads greater than 5000 N, the process of material failure in the ridge area of the structurally similar element begins. This process is accompanied by sound effects (cracking) and a change in the color of the material in the vicinity of the corner. It should also be noted that in the absence of damage, the sensors measurements under repeated loads are the same, and their values linearly depend on the magnitude of the external load. These data indicate linear elastic stress-strain dependence. Figure 5 shows the experimental strain values recorded by sensors 1, 2, 3, 4 at different load values. These results show that when load of 6000 N is reached, one of the sensors records significant changes in the previous behavior of strains with increasing load. In this experiment, a fairly strict linear dependence of the strains on the magnitude of the tensile force takes place when 0 4000 P  N. Therefore, the analysis of the ratios 1 2   , 1 3   , 1 4   , 2 3   , 2 4   , 3 4   was taken in this range. Figure 6 shows some of these relationships 1 3   − the ratio measurements of sensor close to the zone of local material failure and the sensor remote from this zone; 3 4   − the ratio of the measurements of sensors remote from the zone of local material failure.