ISSN: 1945-7553
CODEN: JTEVAB
Page Count: 7

Review of the Effects of Fatigue Cracking Loads on Plane Strain Fracture Toughness

Towers, OL
Research engineer, The Welding Institute, Research Laboratory, Abington Hall, Abington, Cambridge,

Abstract

Plane strain fracture toughness for Mode I loading K_Ic testing standards impose restrictions on the loads used to prepare the fatigue cracks because experiments have shown that if the loads are too high the resulting toughness measurement might be unconservative. Data displaying the effects of fatigue cracking load level on K_Q measurements (“candidate” K_Ic values) have been reviewed and compared to restrictions imposed by two relevant standards on fatigue cracking load level and on the R ratio (K_Fmin/K_Fmax). For the majority of the materials studied these restrictions are sufficiently stringent, but for some materials that display a particular tendency to cyclically soften it may be necessary to increase their severity to the maximum value of stress intensity factor in fatigue K_Fmax ≯ 0.5 K_Q. The basis of the restrictions on R ratio of the two standards is unknown, but relaxation of the limit (≯ 0.1) is difficult to recommend because of lack of relevant data.

Keywords:
fatigue (materials), standards, crack initiation, test specimens, KIc, fracture toughness

Paper ID: JTE11583J
DOI: 10.1520/JTE11583J
ASTM International is a member of CrossRef.