ASTM E2899 Measurement of Initiation Toughness in Surface Cracks

Scope:

ASTM E2899 test method defines a standard for test and analysis of surface cracks that aid in research and helps explain test specimens in three regimes: an elastic-plastic regime, a linear-elastic regime, and a field-collapse regime. It provides details about the design, crack-front behavior, and toughness of the material. The electric potential, crack mouth opening displacement, and acoustic emissions are detected in this method.

Procedure:

In ASTM E2899, the fracture toughness is calculated as a function of toughness and constraint values. The testing apparatus comprises notches and fatigue sharpening surface cracks with the specimens that show the tearing upon applying tension or bending force. The characteristics of the specimen are carefully measured, and the testing is initiated under displacement control. Mechanical alignment is used to deal with non-uniformity. A bend testing fixture is installed, and the tension is applied to the specimen. The region of the crack is observed and compared with material properties.

Specimen size

For ASTM E2899 testing, the specimen size should be as per requirements, with the weight and length measurements taken as follows:

 W ≥ 5 × 2 c and L ≥ 2W.

Here, c= surface crack length

Data:

A toughness-constraint locus is created in ASTM E2899 testing by comparing K_φ or J_φ to the values obtained in the variable constraints of the specimens.
Calculate K_φ with the specimen dimensions, crack dimensions, initiation force (P_i) or moment (M_i), and the initiation angle (φ_i) using the appropriate equations.

Conclusion:

ASTM E2899 test method defines a standard for test and analysis of surface cracks that aid in research and helps explain test specimens in three regimes: an elastic-plastic regime, a linear-elastic regime, and a field-collapse regime.