Crack closure in 2219-T851 aluminum alloy

✍ Scribed by K.D. Unangst; T.T. Shih; R.P. Wei

• Book ID: 103068153
• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 646 KB
• Volume: 9
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(77)90085-6

✦ Synopsis

The effects of specimen thickness, stress ratio (R) and maximum stress intensity factor (Kin.x) on crack closure (or opening) were studied using a 2219-T851 aluminum alloy. The crack length and the occurrence of crack closure were measured by an electrical potential method. The experimental work was carried out within the framework of linear-elastic fracture mechanics.

The experimental results show that the onset of crack closure (or opening) depends on R, K .... and specimen thickness. In terms of the "effective stress intensity range ratio" (U), as defined by Elber, the results show that U tends to increase for increasing R, decrease for increasing K .... and decrease with increasing specimen thickness. From these trends, it is shown that the "effective stress intensity range" (AKcn) does not always increase with increasing stress intensity range (AK).

The experimental results show that crack closure cannot fully account for the effects of stress ratio, specimen thickness and Km.x on fatigue crack growth. The use of AKo~ as a parameter for characterizing the mechanical driving force for fatigue crack growth is questioned.