PSI - Issue 5

Terekhina Alena et al. / Procedia Structural Integrity 5 (2017) 569–576 Terekhina Alena et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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Fig. 1. Notched plate loaded in tension and local system of coordinates and e ffective stress σ eff estimated according to the Point Method.

The critical distance takes the following form:

2

0        1 Ic K  

L

(2)

where 0  is the material inherent strength. The most accurate way to determine critical distance and inherent material strength is to test samples containing two different geometrical features, the two linear elastic stress-distance curves in the incipient failure condition are plotted, in the incipient failure condition, in terms of the adopted equivalent stress obtained by testing a sharp and blunt notch, respectively, the coordinates of the point at which these two curves intersect each other directly gives the values of both L and σ 0 (Figure 2) . Ic K is the plane strain fracture toughness and

Fig. 2. Determination of length scale parameter L and inherent strength r0 through experimental results.

2.2. Critical distance approach for dynamic loading

Mechanical properties of metallic materials subjected to dynamic loading are different from the ones observed under quasi-static loading. Since dynamic failure stress and the dynamic fracture toughness Id K vary as the applied load/strain/displacement rate increases, in the same way also the inherent strength 0  and the length scale parameter L have to vary. So, the effect of the dynamic loading on the failure stress and the fracture toughness can be expressed as follows: