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This study shows that the strength of silicon-alloyed pyrolytic carbon is not affected by long-life cyclic stress up to 6 x 10(8) cycles at stress levels which are two, four and eight times higher than the estimated peak service stress of a mechanical heart valve. It is demonstrated that there is clearly a threshold size for cyclic fatigue crack propagation(More)
The test method introduced here enables the fatigue test of a brittle material at a stress level that is as high as its ultimate fracture strength. The procedural design of the test eliminates uncertainties that often make interpretation of the results difficult. The results, using a statistical analysis, demonstrate that isotropic pyrolytic carbons are(More)
Materials for implanted heart valves face challenges unmatched for most mechanical applications. The valves must function without interruption for lifetimes in the order of 10(9) cycles in a corrosive, hostile environment. A particular carbon has been widely used for the past three decades. The mechanical behavior of this isotropic pyrolytic carbon (PyC),(More)
The theory of contact charging between metals was established in 1951 by Harper and confirmed experimentally in 1975 by Lowell who measured the net charge after separation of pure metals in contact and related it to the contact potential difference and capacitance of the surfaces using a specialized measurement technique. It is generally assumed that these(More)
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