ASTM E 399:2024

1.1 This test method covers the determination of fracture toughness ( K_Ic and optionally K_Isi ) of metallic materials under predominantly linear-elastic, plane-strain conditions using fatigue precracked specimens having a thickness of 1.6 mm (0.063 in.) or greater 2 subjected to slowly, or in special (elective) cases rapidly, increasing crack-displacement force. Details of test apparatus, specimen configuration, and experimental procedure are given in the annexes. Two procedures are outlined for using the experimental data to calculate fracture toughness values: 1.1.1 The K_Ic test procedure is described in the main body of this test standard and is a mandatory part of the testing and results reporting procedure for this test method. The K_Ic test procedure is based on crack growth of up to 2 % percent of the specimen width. This can lead to a specimen size dependent rising fracture toughness resistance curve, with larger specimens producing higher fracture toughness results. 1.1.2 The K_Isi test procedure is described in Appendix X1 and is an optional part of this test method. The K_Isi test procedure is based on a fixed amount of crack extension of 0.5 mm, and as a result, K_Isi is less sensitive to specimen size than K_Ic . This less size-sensitive fracture toughness, K_Isi , is called size-insensitive throughout this test method. Appendix X1 contains an optional procedure for reinterpreting the force-displacement test record recorded as part of this test method to calculate the additional fracture toughness value, K_Isi . Note 1: Plane-strain fracture toughness tests of materials thinner than 1.6 mm (0.063 in.) that are sufficiently brittle (see 7.1 ) can be made using other types of specimens ( 1 ) . 3 There is no standard test method for such thin materials. 1.2 This test method is divided into two parts. The first part gives general recommendations and requirements for testing and includes specific requirements for the K_Ic test procedure. The second part consists of Annexes that give specific information on displacement gage and loading fixture design, special requirements for individual specimen configurations, and detailed procedures for fatigue precracking. Additional annexes are provided that give specific procedures for beryllium and rapid-force testing, and the K_Isi test procedure, which provides an optional additional analysis procedure for the test data collected as part of the K_Ic test procedure. 1.3 General information and requirements common to all specimen configurations: Section Referenced Documents 2 Terminology 3 Stress-Intensity Factor 3.1.1 Plane-Strain Fracture Toughness 3.1.2 Crack Plane Orientation 3.1.4 Summary of Test Method 4 Significance and Use 5 Significance 5.1 Precautions 5.1.1 - 5.1.5 Practical Applications 5.2 Apparatus (see also 1.4 ) 6 Tension Machine 6.1 Fatigue Machine 6.2 Loading Fixtures 6.3 Displacement Gage, Measurement 6.4 Specimen Size, Configurations, and Preparation (see also 1.5 ) 7 Specimen Size Estimates 7.1 Standard and Alternative Specimen Configurations 7.2 Fatigue Crack Starter Notches 7.3.1 Fatigue Precracking (see also 1.6 ) 7.3.2 Crack Extension Beyond Starter Notch 7.3.2.2 General Procedure 8 Specimen Measurements Thickness 8.2.1 Width 8.2.2 Crack Size 8.2.3 Crack Plane Angle 8.2.4 Specimen Testing Loading Methods 8.3 Loading Rate 8.4 Test Record 8.5 Calculation and Interpretation of Results 9 Test Record Analysis 9.1 ...

77.040.10