0 102030405060708 β -4 -3 -2 -1 0 1 2 3 KI , KII (MPa m1/2) (deg.) ΚΙ ( ΚΙΙ ( ΚΙ (σ 3= 28 ΚΙΙ (σ 3= 28 ΚΙ ( ΚΙΙ ( D = 98 mm a/R = 0.3 0 -4 -3 -2 -1 0 1 KI / KIC 0 1 2 KII / KIIC Straight Notch a/R = 0.3 D = 98 mm Condition Ambient σ3= 28 T=116oC (a) (b) Figure 2: Compar ison of (a) fracture toughness, (b) fracture envelopes -3 -2 -1 0 1 KI / KIC 0 1 2 KII / KIIC a/R = 0.3 D = 98 mm Notch Type Straight Chevron -3 -2 -1 0 1 KI / KIC 0 1 2 KII / KIIC Straight Notch a/R = 0.3 D 84 mm 98 mm (a) (b) Figure 3: Fracture envelopes for Brazilian disks with (a) different D, (b) different notches TABLE 2 REGRESSION PARAMETERS FOR VARIOUS CONDITIONS Positive Region Negative Region Condition Notch Type D (mm) A B C A B C Chevron 98 0.9589 1.2436 −2.1709 0.9811 −0.1746 −0.0799 Straight 84 0.8664 −0.9402 0.0928 1.0797 0.1162 −0.0203 Ambient Straight 98 1.0891 −0.3701 −0.7584 1.0779 −0.3120 −0.1616 σ3 = 28 MPa Straight 98 1.0290 0.0461 −1.1663 1.0399 −0.0670 −0.1779 T = 116°C Straight 98 1.1046 0.6635 −1.7977 1.0759 −0.0882 −0.0661
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