Question

A structural component in the form of a wide plate is to be fabricated from a steel alloy that has a plane strain fracture toughness of and a yield strength of 1400 MPa (205,000 psi). The flaw size resolution limit of the flaw detection apparatus is 4.0 mm (0.16 in.). If the design stress is one half of the yield strength and the value of Y is 1.0, determine whether or not a critical flaw for this plate is subject to detection.

Answer 1

Not subject to detection

Step-by-step explanation:

Assuming the value of strain fracture toughness is 77 Mpa
`\sqrt m`

The design stress is half hence
`\sigma=0.5* 1400=700 Mpa`

Critical flaw size,
`a_c=\frac {1}{\pi}(\frac {K_(1c)}{Y/sigma})^(2)`

Where Y is dimensionless parameter,
`\sigma` is applied stress,
`K_(1c)` is plane strain fracture toughness,
`a_c` is critical length of surface crack

`a_c=\frac {1}{\pi}(\frac {77}{1*700})^(2)= 0.0038515496\approx 0.00385m`

The critical length of surface crack is therefore 3.85 mm, which is less than detection apparatus size given as 4 mm

Since the critical flaw size is less than the resolution limit of flaw detection apparatus, the critical flaw for this plate is not subjected to detection.