ASTM C1465-08(2013)
高温下用恒定应力速度挠曲试验测定高级陶瓷慢裂增长系数的标准试验方法

Standard Test Method for Determination of Slow Crack Growth Parameters of Advanced Ceramics by Constant Stress-Rate Flexural Testing at Elevated Temperatures

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标准号

ASTM C1465-08(2013)

发布

2008年

发布单位

美国材料与试验协会

替代标准

ASTM C1465-08(2013)e1

当前最新

ASTM C1465-08(2019)

 

 

适用范围

4.1 For many structural ceramic components in service, their use is often limited by lifetimes that are controlled by a process of slow crack growth. This test method provides the empirical parameters for appraising the relative slow crack growth susceptibility of ceramic materials under specified environments at elevated temperatures. This test method is similar to Test Method C1368 with the exception that provisions for testing at elevated temperatures are given. Furthermore, this test method may establish the influences of processing variables and composition on slow crack growth as well as on strength behavior of newly developed or existing materials, thus allowing tailoring and optimizing material processing for further modification. In summary, this test method may be used for material development, quality control, characterization, and limited design data generation purposes.

Note 3—Data generated by this test method do not necessarily correspond to crack velocities that may be encountered in service conditions. The use of data generated by this test method for design purposes may entail considerable extrapolation and loss of accuracy.

4.2 In this test method, the flexural stress computation is based on simple beam theory, with the assumptions that the material is isotropic and homogeneous, the moduli of elasticity in tension and compression are identical, and the material is linearly elastic. The average grain size should be no greater than one fiftieth (1/50) of the beam thickness.

4.3 In this test method, the test specimen sizes and test fixtures were chosen in accordance with Test Method C1211, which provides a balance between practical configurations and resulting errors, as discussed in Refs (7, 8). Only the four-point test configuration is used in this test method.

4.4 In this test method, the slow crack growth parameters (n and D) are determined based on the mathematical relationship between flexural strength and applied stress rate, log σ_f = [1/(n + 1)] log σ˙ + log D, together with the measured experimental data. The basic underlying assumption on the derivation of this relationship is that slow crack growth is governed by an empirical power-law crack velocity, v = A[K_I /K_IC]ⁿ (see Appendix X1).

Note 4—There are various other forms of crack velocity laws which are usually more complex or less convenient mathematically, or both, but may be physically more realistic (9) . The mathematical analysis in this test method does not cover such alternative crack velocity formulations......

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