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1.1This test method covers the determination of plane-strain (chevron-notch) fracture toughnesses, K_Iv or K_IvM, of metallic materials. Fracture toughness by this method is relative to a slowly advancing steady state crack initiated at a chevron-shaped notch, and propagating in a chevron-shaped ligament (Fig. 1). Some metallic materials, when tested by this method, exhibit a sporadic crack growth in which the crack front remains nearly stationary until a critical load is reached. The crack then becomes unstable and suddenly advances at high speed to the next arrest point. For these materials, this test method covers the determination of the plane-strain fracture toughness, K_Ivj or K_IvM, relative to the crack at the points of instability.

(A)See Fig. 6. (A)See Fig. 6.(B)See Note 1. (A)Compiled from Refs (1), (2), (3), and (4), and using the polynomials in Table 5.(B)Minimum value of Y*. (A)Compiled from Refs (1), (2), (3), and (4).(B)Y*=exp[C₀ +C₁ r+C₂ r² +C₃ r³ +C₄ r⁴ ], accuracy 0.5%.(C)Estimated from finite element analysis (3), and extrapolated equation from Ref (4). Accuracy for 0.3 r 0.85 is 0.5%.(D)Extrapolated from equations in Ref (4). Accuracy estimated to be 0.5% for 0.2 r 0.85.(E)Equation from Ref (4). Accuracy estimated to be 0.5% for 0.15 r 0.6.

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Published: 07/01/2014 Number of Pages: 12 File Size: 1 file , 440 KB