PSI - Issue 13

N.V. Boychenko / Procedia Structural Integrity 13 (2018) 908–913

909

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Boychenko N.V. / Structural Integrity Procedia 00 (2018) 000–000

1. Introduction To assess the residual life and safe operation of structural components by fracture mechanics methods, it is necessary to determine the stress intensity factors for a specific technical problem. Currently, several handbooks on stress intensity factors Tada et al. (1973), Sih (1973, 1974), Murakami (1987) are published and widely used. These handbooks are devoted to the determination of the elastic stress intensity factors. However, in cracked bodies a local zone of plastic deformation appears along the crack front, consequently, the elastic-plastic fracture resistance parameters should be used to describe crack growth. The concept of the plastic stress intensity factor taking into account the constraint effects is formulated and its experimental substantiation is presented by Shlyannikov et al (2014a-c). This paper devoted to elastic and plastic stress intensity factors determination in specimens of aluminum alloys under various loading conditions in the temperature range. Elastic and plastic stress intensity factors are determined along the front of a curvilinear semi-elliptic crack with a variation in the relative sizes of defects and the loading types at room, high and low temperature. Wide range of relative crack depth and aspect ratio is studied. The calculations are carried out under uniaxial tension and a three-point bending for two aluminum alloys D16T and B95. Fundamental differences in the behavior of the elastic and plastic stress intensity factors for surface cracks in the plate are established at temperature range (20°С, 250°С, -60°С). 2. Material properties and specimen geometry The object of the study is a plate with a central surface crack. The geometry of the specimen and the semi-elliptical crack is shown in Fig. 1. The thickness of specimen is equal to 10 mm. The crack front is approximated by an elliptical curve with the major axis 2c and the minor axis a .

Fig. 1. Details of the plate and crack geometry.

The studies were carried out for different combinations of the aspect ratio ( a/c from 0.3 to 1) and crack depth ( a/t from 0.3 to 0.8), combinations of crack geometry parameters are presented in Table 1.

Table 1. Combinations of variable parameters

Uniaxial tension

Three-point bending

a/c

а/t

а/t

0.3 0.5 0.7

0.3 0.3 0.3 0.3

0.4 0.4 0.4 0.4

0.6 0.6 0.6 0.6

0.8 0.8 0.8 0.8

0.3 0.3 0.3 0.3

0.4 0.4 0.4 0.4

0.6 0.6 0.6 0.6

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