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M. Nowak, A. Wawrykowicz


Some methodical problems in fatigue investigations of Elit 25


Polimery 1980, No 10, 378


DOI: dx.doi.org/10.14314/polimery.1980.378

Summary

The results of fatigue Investigations of Elit 25 (polyethylene terephthalate containing 25 per cent of glass fibre) after ageing for 10—15 months have been presented. The influence of the so-called machine effect, of the value of cycles limit (2—100) x 106 and of the method of determination (statistical, reordering by Gatto, up-and-down, modified up-and-down and Probit methods) has been taken into account. It has been found that the fatigue strength limit of Elit 25 is 22,1 MPa at 107 cycles limit at the temperature of 298 K and frequency of 15 cps and is thus by 80 per cent lower than the initial tensile strength. It has also been found that the fatigue strength of - Elit 25 is independent of the testing method used within a 3 per cent error. The effect of machine depends on the value of cycles limit and It is equal to 5 per cent for cycles limit of 107 cycles.


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