Authors: KS Chan JW Tian B Yang PK Liaw
Publish Date: 2009/09/01
Volume: 40, Issue: 11, Pages: 2545-2556
Abstract
The evolution of slipbands into fatigue cracks in surface grains of commercially pure Ni Ni200 9935Ni04Fe025Cu in wt pct was studied at ambient temperature Roundbar specimens with electropolished surfaces were fatigued under displacementcontrolled fully reversed conditions at four strain amplitudes under a nominal strain rate of 1 × 10−3 s−1 Lowcycle fatigue tests were periodically interrupted to characterize the slip morphology at various fatigue cycles using scanning electron microscopy The results showed that the distribution of slip in Ni200 varied considerably in individual surface grains at a given strain amplitude Some grains were deformed more severely and exhibited more intense slipbands than others while some surface grains showed the absence of slip lines with no evidence of plastic deformation The evolutions of slipband width and spacing in deformed surface grains were followed as a function of fatigue cycles in order to assess the slipband morphology at the onset of fatigue crack initiationThis contribution of KSC was supported by the Southwest Research Institute and by the Air Force Office of Scientific Research AFOSR USAF under Contract No F496200110547 and was performed as part of the AFOSR MEANS program Dr Craig S Hartley program manager JWT BY and PKL are supported by the National Science Foundation International Materials Institute IMI program the Combined Research and Curriculum Development CRCD program and the Center for Materials Processing CMP at the University of Tennessee with Dr C Huber Ms M Poats and CJ McHargue as the program directors respectively The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements either expressed or implied of the Air Force Office of Scientific Research or the United States Government The authors acknowledge the clerical assistance of Ms L Mesa Southwest Research Institute in the preparation of the manuscript
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