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EFFECT OF PARTIAL‐COVERAGE UPON THE FATIGUE FRACTURE BEHAVIOUR OF PEENED COMPONENTS
Author(s) -
Meguid S. A.
Publication year - 1991
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1991.tb00680.x
Subject(s) - peening , shot peening , residual stress , materials science , paris' law , stress intensity factor , structural engineering , stress concentration , fracture (geology) , stress (linguistics) , bending , crack closure , fracture mechanics , composite material , engineering , linguistics , philosophy
Abstract The achievement of full‐coverage during the application of shot‐peening to critical components represents a major concern in the aerospace and power generation industries. It has been accepted, for many years, that full‐coverage of such components is needed to attain the beneficial fatigue‐life effects of the treatment. It has also been proposed, by a number of industrialists, that partial‐coverage may apparently shorten the fatigue‐life of the component because of the presumed presence of tensile residual stresses in the uncovered areas. Three aspects of the investigation were accordingly examined. The first deals with the accurate measurement of peening coverage using a three‐dimensional surface profilometer arrangement. The second deals with the development of fatigue crack growth data for fully‐ and partially‐peened components using an instrumented rotating‐bend fatigue rig. The third deals with monitoring the residual stress field associated with different peening‐coverage using the dissection method. In order to highlight the effect of the treatment upon the fatigue behaviour of the tested components, both theoretical and experimental techniques were considered. In the theoretical work, three‐dimensional finite element analysis of circumferentially cracked notched and un‐notched cylindrical components was considered in the development of the corresponding stress‐intensity factor ( K K 1) under bending loads. The stress‐intensity factor vs crack length relationship was subsequently used in the experimental determination of fatigue crack growth rate data at the different stress levels examined. Accordingly, room temperature rotating‐bend fatigue tests were conducted on specimens made from medium carbon steel 080 M40 (En 8) and aluminium alloy (7075‐T6). Surprisingly, the results of both materials reveal that a life improvement of up to 50% can be attained at 35% coverage level.