PSI - Issue 16

Cristian Alejandro de León Gómez et al. / Procedia Structural Integrity 16 (2019) 265–272 Cristian Alejandro de León Gómez et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig 1. (a) Single V groove joint preparation and (b) experimental welding setup.

Rectangular shape of specimen with the geometric orientation shown in the right of Fig. 2 was used for corrosion fatigue test with dimensions at 5 × 5 × 100 mm. A sinusoidal waveform of load with a frequency of 0.90 Hz was used. The initial maximum stress of 0.99σ ys (yield strength) and a load ratio (R) of 0.5 was applied for fatigue test. The loading was parallel to the short transverse (S) direction, as demonstrated in Fig. 2. Fatigue tests were conducted in natural seawater at open circuit potential (OCP), all at ambient temperature. After determining the fatigue life (N f ), some interrupted fatigue tests at certain loading cycles were also performed.

Fig. 2. Cross-section cuts to the weld bead.

3. Methodological aspects of the research

In Polishchuk et al. (2015) the analysis aimed at determination of corrosion-cyclic crack resistance of profile steel of 45 × 45 × 5 mm angle of different operated machines has been carried out. However, the results of the research do not give a clear answer regarding further evaluation or durability of this construction element. For such assessment the given paper contains analytical relations for stress intensity factor (SIF) K 1 and their change rate d K 1 / da near a size crack tip in the plate used for modelling of the investigation object (here a – typical size of crack like defect). Six cases of potentially possible crack like defects are considered. Such analytical base serves for assessment the durability of roads with crack like defects by the factor “resistance of construction element to crack growth” that is the characteristic of SIF K 1 change rate near the crack tip of a length during its growth in a specific structural element, as shown by Dmytrakh et al (2005). Along with this, on the basis of experimental research, presented in Polishchuk et al. (2015) critical values of crack depth were determined: 1) when the depth of the crack is less than its safe value, at which further crack propagation is not observed a < a th , where a th – threshold size of the crack; 2) when depth of the crack is greater than the value at which spontaneous crack growth is possible, that leads to brittle failure of the investigative object: a ≥ a fc where a fc – critical size of the crack. To realize such approach, the extension of the investigated plate with such existing crack like defects is considered: extension of the plate with through-thickness centred crack; extension of the plate with extended surface crack; extension of the plate with two extended surface cracks; extension of the plate with semielliptical surface crack; extension of the plate with quarterelliptical corner crack; extension of the plate with embedded elliptical crack (centred), models of which are shown in Fig. 3. a – f.