Fatigue crack propagation testing

Fatigue crack initiation, in metal-matrix composites, 16 185 Fatigue crack initiation sites, 13 481 Fatigue crack propagation tests, 16 185-187... 

Fatigue crack propagation tests were performed on 73-nmi x 73-mm (2.9 in. x 2.9 in.) compact-tension specimens that had been machined from the plaques and then precracked. An electrohydrau-lic closed-loop test machine was used to produce a constant-amplitude, 10-Hz sinusoidal load. Host of the tests were performed in duplicate at room temperature in laboratory air at an average ambient RH of A0%. In view of the slow rate of moisture equilibration in air at room temperature (15), the difference between the ambient RH and that of the nylon being tested was presumed to be unimportant within the time period of the test (3-5 hr). 

Varadarajan R, Rimnac CM. Compliance calibration for fatigue crack propagation testing of ultra high molecular weight polyethylene. Biomaterials 2006 September 27(27) 4693-7. 

Fatigue Crack Propagation, ASTM STP 415, American Society for Testing and Materials, Philadelphia, Pa., 1967. 

Brocklehurst [37] has written an exhaustive review of the early work (prior to 1977) on fracture in polycrystalline graphite. Much of this work focused on the fracture behavior of nuclear graphites. In most investigations considered, conventional fracture mechanics tests and analysis were performed for macroscopic cracks. LEFM provided an adequate criterion for failure. Additionally, results on work of fracture, strain energy release rate, and fatigue crack propagation were reported. 

A further development of this procedure is fatigue crack propagation (FCP) experiments in the presence of a stress cracking environment. While in the fracture mechanics test methods described above the specimen is under constant load, in a FCP experiment the specimen is tested under cyclic loading conditions in the presence of a sensitizing medium. 

The influence of test frequency on fatigue crack propagation of notched specimens has been studied by several investigators, but mostly by Hertzberg, Manson and coworkers For PS, they observed a decrease in FCP rate as test frequency was increased from 1 Hz to 10 Hz to 100 No results were presented for HIPS... 

PVC show. Additives, e.g. stabilizers, may also have an influence. It is often due to differences in these intrinsic parameters that test results in the literature on commercially available polymers from different manufacturers are not fully comparable. In this context it is interesting to note that an influence of test frequency has been reported for different polymers in which the fatigue crack propagation rate decreases with increasing frequency While in one grade of PMMA this... 

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