PSI - Issue 13

Lesiuk G. et al. / Procedia Structural Integrity 13 (2018) 1595–1599 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

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2.2. Essential Work of Fracture

In order to evaluate the critical essential work of fracture, the two types of specimens were prepared. According to the literature standardization of the EWF test method, the 40-DENT specimens were fabricated from molded plates 2 mm thick. The moulding process was performed with accordance of the material manufacturer DOW Company using Hyperflex 101 material. Two type of hardness in specimen were obtained; 80 and 90 ShA. During the experiments, the force, displacement and temperature were measured (with additional channel from thermovision camera). According to the numerical procedure prepared in HP VEE environment all energy quantities, responsible for fracture process were solved. All the mechanical tests were performed with a constant cross-head of displacement speed level – 50mm/min using the MTS 810 machine with 5kN load cell. The cracks were prepared using a surgical knife. As it was expected, a significant difference was observed due to the differences in hardness of polyurethane elastomers. According to the EWF method, the We – specific, essential work of fracture were evaluated; for 80ShA – 26.8kJ/m 2 , for 90ShA – 52.3kJ/m 2 . Exemplary load-displacement results for different crack lengths are presented in Fig. 2.

Fig.2. a) Exemplary diagram with the registered differences in load-displacement curves for PU80ShA and PU90ShA (L=14mm), b) Exemplary diagram with the registered differences in load-displacement curves for PU80ShA and PU90ShA (L=8mm)

2.3. Fatigue crack growth rate test For fatigue crack growth characterization, the PS – Pure Shear, cracked specimens were involved. Typical PS specimen is presented in Fig. 3. In experimental campaign, the main dimensions of the PS specimen were following: h 0 =20 mm, c 0 - initial crack length = 24.mm, W (specimen width) = 160 mm.

Fig. 3. PS (Pure Shear) planar specimen scheme with crack subjected to fatigue test; Thor (2012)