ASTM C1368 Slow Crack Growth Parameters of Advanced Ceramics

Scope:

ASTM C1368 determines slow crack growth parameters of ceramics by constant stress-rate flexural testing at ambient temperature. This test method provides empirical parameters for estimating ceramic materials’ relative slow crack growth (SCG) susceptibility in specific settings. It can be used to determine the effects of composition and processing factors on SCG as well as strength behavior of newly generated or existing materials, allowing for more precise customization and optimization of material processing. In summary, this test method may be used for material development, quality control, characterization, and limited design data generation purposes.

Test Procedure:

For ASTM C1368, the specimens are tested on their respective fixtures in specified testing setups. The fixture applies an initial load of no more than 20N to the specimen, followed by preloading,  and then load control mode. A load versus time curve is recorded for each test to determine the actual loading rate, after which the associated stress rate is determined. Fracture load is measured with a 1% accuracy. Specimens that have been broken outside of the gauge length are not used as value data points for slow crack growth (SCG) parameters.

Specimen Size : 

A rectangular beam specimen is used as a test specimen for ASTM C1368, which must be handled with care to avoid random and severe flaws during the test procedure. 

Data:

In ASTM C1368, the coefficients of variation of the SCG parameter n and of the SCG parameter D is calculated as follows:  

where, 

CV_n = coefficient of variation of the SCG parameter n 

CV_D = coefficient of variation of the SCG parameter D

SD_n = standard deviation of the SCG parameter n 

SD_D = standard deviation of the SCG parameter D 

Advanced ceramics’ strength is probabilistic in nature. As a result, SCG calculated from a  ceramic material’s flexural strengths is similarly a probabilistic occurrence.

Conclusion:

ASTM C1368 determines slow crack growth parameters of ceramics by constant stress-rate flexural testing at ambient temperature.