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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Initial notch was prepared by surgical blade in order to obtain sharp notch – similar to a fatigue crack. All specimens were gripped in additional fixture and the clamping force was controlled by bolts system in order to avoid slipping of the specimen during fatigue test. The measurement stand used in experimental campaign is presented in Fig. 4 and consist of: 1 – digital microscope with low magnification and lightening system, 2 – grips, 3- load cell and 4 – specimen.

Fig. 4. Measurement stand; 1 – digital microscope with illumination system, 2 – gripping system, 3 – upper grip MTS with load cell, 4 - specimen

During experiment, the crack length was monitored using microscopic system and image-data processing. Exemplary views on fatigue cracks (in different phases of fatigue crack growth) are presented in Fig. 5. The specimens were loaded with sinusoidal waveform under displacement mode control with keeping strain ratio R  =0 and constant total strain on the level  =15%. In order to avoid thermal effects, during experiments the frequency f was kept on constant level f =1Hz. During tests, the temperature was monitored using thermo-vision camera. The fatigue lives of the specimens; 80 ShA and 90ShA are presented in Fig. 6. a) b)

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Fig. 5. Measured crack length at different stages of fatigue crack growth of PUR elastomers: a) initial crack (80ShA), b) 45 mm crack length (80ShA), c) initial crack (90ShA) , d ) 51 mm crack length (90ShA)