Fracture Toughness in Design

There are three crucial factors which must be considered in designing for fracture:

• The fracture toughness (K_c or plane strain K_Ic)
• the imposed stress (s)
• and the flaw size (a)

It must be determined first what the limits and constraints on the variables will be

• Once two of them are determined, the third will be fixed
• For example, if the stress level and plane strain fracture toughness are fixed, then the maximum allowable flaw size must be: