Fracture of thin sections containing surface cracks

✍ Scribed by R.M Bonesteel

• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 883 KB
• Volume: 5
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(73)90039-8

✦ Synopsis

Surface-cracked specimens of several thicknesses of 7075-T65 I and 7075-T6 aluminum were tested in uniaxial tension. For thicknesses t less than 0.25 in., the gross fracture stress of of 7075-T65 I AI was empirically related to flaw size by the following expression:

where cull is the ultimate strength, a the crack depth, 4 a function of crack shape, and S a proportionality constant equal to -I .7 in.-"2. For 0.25-in. thick 7075-T65 1 aluminum, u, was found to obey this relationship only when a/#? is less than 0.065 in.; for larger flaws, such that 0.065 < a/@ < 0.1 I, uf is better predicted by Irwin's surface-crack equation with an apparent K,, value of 32.2 ksi-in."'.

Fracture data for thin sections of 2014-T6 and 2014-T65 1 Al tested at -423°F are analyzed in terms of the empirical relationship above and are found to be in good agreement. For these alloys, S has a value of -2.6 in.-"*.

Applicability of the empirical relationship and Irwin's surface-crack analysis to the fracture of thin sections is discussed in terms of crack size, section thickness, and plastic zone size.