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Fatigue crack growth in polymers. II. The interaction of mean stress, frequency, and temperature
Author(s) -
Radon J. C.,
Culver L. E.
Publication year - 1975
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760150706
Subject(s) - materials science , polycarbonate , composite material , stress intensity factor , fracture mechanics , crack closure , stress (linguistics) , growth rate , polymer , intensity (physics) , ultimate tensile strength , optics , linguistics , philosophy , geometry , mathematics , physics
Fatigue crack propagation was studied in large centernotched plate specimens of two polymers, poly(methyl methacrylate) and polycarbonate, under tensile cycling conditions. Tests were performed at frequencies of 0.1, 5.0, and 20 Hz, and at two temperatures, −60 and +21°C. The interaction of mean stress intensity, frequency and temperature was investigated. It was found that in tests performed at constant frequency or temperature, the fatigue crack propagation rates were dependent on both the range of the applied stress intensity factor and its mean value, K m . All propagation rates increased with increasing K m . Also, the threshold stress intensities decreased with increasing K m , suggesting very low levels of Δ K for non‐propagating cracks, certainly below the 0.4 K c , the minimum level investigated here. In PMMA, decreasing crack growth rates with increasing frequency were established for a wide range of K m . However, in PC crack growth rates increased substantially with increasing frequency. Finally, “upper and lower transition points” were noted on crack growth curves of both materials.