A modified thickness criterion for fracture toughness testing

✍ Scribed by J.C. Ritter

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 806 KB
• Volume: 9
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(77)90068-6

✦ Synopsis

Ahstraet--A modified criterion is developed on an empirical basis for the minimum thickness Brain of a plane strain fracture toughness test specimen: B.,. = 400 g~o Ecq.

where K~, is the plane strain fracture toughness, E is the Young's modulus and ~r~, is the yield stress of the material. The modified criterion is tested alongside the ASTM thickness criterion against published data on the variation of Kc with thickness, and shows significantly the better agreement with observed values of B=in for a wide range of materials.

An attempt has been made to rationalise this criterion. The expression is considered to take into account two major factors which determine B=i., the attainment of plane strain in the specimen interior ahead of the crack tip, and the role of microstructure in determining how far the quasi-plane strain fracture (square fracture) extends beyond the region of true plane strain.