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WK87 Test Method for Determination of Slow Crack Growth Parameters of Advanced Ceramicsby Constant Stress Flexural Testing (Stress Rupture) at Ambient Temperature

Date Initiated: 02-07-2003

1. Scope

1.1 This standard test method covers the determination of slow crack growth (SCG) parameters of advanced ceramics by using constant stress flexural testing in which time to failure of flexure test specimens is determined in four-point flexure as a function of constant applied stress in a given environment at ambient temperature. In addition, test specimen fabrication methods, test stress
levels, data collection and analysis, and reporting procedures are addressed. The decrease in time to failure with increasing applied stress in a specified environment is the basis of this test method that enables the evaluation of slow crack growth parameters of a material.
NOTE 1 - The test method in this standard is frequently referred to as "static fatigue" or stress-rupture testing (Refs (1-3)) in which the term "fatigue" is used interchangeably with the term "slow crack growth." To avoid possible confusion with the "fatigue" phenomenon of a material that occurs exclusively under cyclic loading, as defined in E1823, this test method uses the term "constant stress testing" rather than "static fatigue" testing.
1.2 This test method applies primarily to monolithic advanced ceramics that are macroscopically
homogeneous and isotropic. This test method may also be applied to certain whisker- or particlereinforced ceramics as well as certain discontinuous fiber-reinforced composite ceramics that exhibit macroscopically homogeneous behavior. Generally, continuous fiber ceramic composites do not exhibit macroscopically isotropic, homogeneous, continuous behavior, and the application of this test method to these materials is not recommended.
1.3 This test method is intended for use with various test environments such as air, other gaseous environments and liquids.
1.4 Values expressed in this standard test are in accordance with the International System of Units (SI) and Practice E 380.
1.5 This test method may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and
determine the applicability of regulatory limitations prior to use.