Calculate the KIC from the data - thick cylinder:

In a fracture test a 3-point bend specimen of thickness 20 mm and depth 25 mm is supported over a span of 100 mm. The specimen is precracked. The surface occurs at a load of 16513 N and crack length is measured after fracture as 10.25 mm. Calculate the KIC from the data.

Solution

W = 25 mm, B = 20 mm,  S/ W =  100 /25  = 4, a = 10.25 mm,  a/W = 10.25/25 = 0.41

Y = 1.93 - 3.07 (0.41) +14.53 (0.41)²  - 25.11 (0.41)³  + 25.8 (0.41)⁴

= 1.93 - 1.2587 + 2.4425 - 1.7306+ 0.729 = 2.1122

Z = (1 /6)BW ² = (1/6) 20 ´ (25)² =2083.33 mm²

            M =      Pf  S /4 =(16513 ´ 100) /4 = 412825 N-mm

s = M/Z = 412825 /2083.33 = 198.156 N/mm²