This standard describes tests for determining the fatigue crack growth rate from the fatigue crack growth threshold stress-intensity factor range, , to the onset of rapid, unstable fracture.
This standard is primarily intended for use in evaluating isotropic metallic materials under predominantly linear-elastic stress conditions and with force applied only perpendicular to the crack plane (mode I stress condition), and with a constant stress ratio, R.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 10623 Metallic Material - Mechanical Testing C Vocabulary (GB/T 10623-2008; ISO 23718: 2007, MOD)
GB/T 16825.1 Verification of Static Uniaxial Testing Machines - Part 1: Tension/Compression Testing Machines - Verification and Calibration of the Force-measuring System (GB/T 16825.1-2008; ISO 7500-1: 2004, IDT)
GB/T 25917 Axial force-applied Fatigue Testing Machines Dynamic Force Calibration (GB/T 25917-2010; ISO 4965: 1979, MOD)
ISO 23788 Metallic Materials - Verification of the Alignment of Fatigue Testing Machines
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 10623 and the following apply.
3.1
crack length
a
linear measure of a principal planar dimension of a crack from a reference plane to the crack tip
Note: This is also called crack size.
3.2
cycle
N
smallest segment of a force-time or stress-time function which is repeated periodically
Note: The terms “fatigue cycle”, “force cycle” and “stress cycle” are used interchangeably. The letter N is used to represent the number of elapsed force cycles.
3.3
fatigue crack growth rate
da/dN
extension in crack length
3.4
maximum force
force having the highest algebraic value in the cycle; a tensile force being positive and a compressive force being negative
