Accession Number:

ADA142609

Title:

Fatigue Behavior of Long and Short Cracks in Wrought and Powder Aluminum Alloys.

Descriptive Note:

Annual rept. 15 Apr 83-14 Apr 84,

Corporate Author:

CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND MINERAL ENGINEERING

Personal Author(s):

Report Date:

1984-05-01

Pagination or Media Count:

205.0

Abstract:

The fatigue behavior of short cracks, which are small compared to the scale of the microstructure, small compared to the scale of local plasticity or simply physically small i.e., approximately 1 mm, must be considered as one of the major factor limiting the application of defect-tolerant fatigue design for airframe and engine components. Accordingly, the current program is aimed at identifying factors which govern the growth of such short cracks in contrast to long cracks in a series of commercial aluminum alloys, with specific reference to behavior at near-threshold levels below approximately 10 to the minus 6th power mmcycle. In this second annual report, the status of the program is described in terms of i an expanded review of the factors which lead to differences in long and short crack behavior, with particular regard to the role of crack closure mechanisms, ii a description of experiments performed to characterize the role of microstructure in influencing the propagation of long cracks in IM 7150 aluminum alloys, and iii a description of experiments carried out to isolate the effects fo crack closure on the propagation of both long and short cracks, and specifically to investigate the location of the closure responsible for the development of a threshold.

Subject Categories:

  • Properties of Metals and Alloys
  • Statistics and Probability
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE