ASTM E561-08 pdf free download.Standard Test Method forK-R Curve Determination.
ASTM E561-08 covers the determination of the resistance to fracture of metallic materials under Mode I loading at static rates using either of the following notched and precracked specimens: the middle-cracked tension M(T) specimen or the compact tension C(T) specimen. A K-R curve is a continuous record of toughness development (resistance to crack extension) in terms of KR plotted against crack extension in the specimen as a crack is driven under an increasing stress intensity factor, K.
Referenced Documents
ASTM E1823 Terminology Relating to Fatigue and Fracture Testing;
ASTM Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials;
ASTM Practices for Force Verification of Testing Machines;
4. Summary of Test Method
4.1 During slow-stable fracturing, the developing crack
extension resistance Kg is equal to the applied stress intensity factor K. The crack is driven forward by continuously or incrementally increasing force or displacement Measurements are made periodically for determination of the effective crack size and for calculation of K values,which are individual data points that define the K-R curve for the material under those test conditions.
7. Specimen Compliance Measurement Requirements
7.1 In the K-R test. the effective crack size is determined either by direct measurement of the physical crack size and adjusting for the crack tip plastic zone, or by specimen compliance techniques which can determine effective crack size directly. This section provides background and require ments for the use of compliance techniques.