Structure, processing and performance of ultra-high molecular weight polyethylene (IUPAC Technical Report). Part 4: sporadic fatigue crack propagation

0532380 - ÚMCH 2021 RIV DE eng J - Článek v odborném periodiku
Bucknall, C. - Altstädt, V. - Auhl, D. - Buckley, P. - Dijkstra, D. - Galeski, A. - Gögelein, C. - Handge, U. A. - He, J. - Liu, C.-Y. - Michler, G. - Piorkowska, E. - Šlouf, Miroslav - Vittorias, I. - Wu, J. J.
Structure, processing and performance of ultra-high molecular weight polyethylene (IUPAC Technical Report). Part 4: sporadic fatigue crack propagation.
Pure and Applied Chemistry. Roč. 92, č. 9 (2020), s. 1521-1536. ISSN 0033-4545. E-ISSN 1365-3075
Institucionální podpora: RVO:61389013
Klíčová slova: consolidation * crazing * fatigue
Obor OECD: Polymer science
Impakt faktor: 2.453, rok: 2020
Způsob publikování: Open access
https://www.degruyter.com/view/journals/pac/92/9/article-p1521.xml?tab_body=abstract

Fatigue tests were carried out on compression mouldings supplied by a leading polymer manufacturer. They were made from three batches of ultra-high molecular weight polyethylene (UHMWPE) with weight-average relative molar masses, -MW, of about 0.6 × 106, 5 × 106 and 9 × 106. In 10 mm thick compact tension specimens, crack propagation was so erratic that it was impossible to follow standard procedure, where crack-tip stress intensity amplitude, ΔK, is raised incrementally, and the resulting crack propagation rate, da/dN, increases, following the Paris equation, where a is crack length and N is number of cycles. Instead, most of the tests were conducted at fixed high values of ΔK. Typically, da/dN then started at a high level, but decreased irregularly during the test. Micrographs of fracture surfaces showed that crack propagation was sporadic in these specimens. In one test, at ΔK = 2.3 MPa m0.5, there were crack-arrest marks at intervals Δa of about 2 μm, while the number of cycles between individual growth steps increased from 1 to more than 1000 and the fracture surface showed increasing evidence of plastic deformation. It is concluded that sporadic crack propagation was caused by energy-dissipating crazing, which was initiated close to the crack tip under plane strain conditions in mouldings that were not fully consolidated. By contrast, fatigue crack propagation in 4 mm thick specimens followed the Paris equation approximately. The results from all four reports on this project are reviewed, and the possibility of using fatigue testing as a quality assurance procedure for melt-processed UHMWPE is discussed.
Trvalý link: http://hdl.handle.net/11104/0311623