Opening and closing of cracks at high cyclic strainsThe closure behavior of cracks of different length and at different cyclic strain levels (ranging from predominantly elastic to grossly plastic strains) was studied to observe the effect of residual crack-tip plasticity on crack closure. Cracks were initiated either naturally or artificially (from electric discharge machining pits) in uniaxial test specimens of strengthened alloy steel AISI 4340 with a grain size of 0.016 mm. It was found that, at high strains, cracks closed only when the lowest stress level in the cycle was approached. The stress or the strain opening level depended upon the exact point along the crack length where the observations were made. As the plastic deformation increased, the relative crack opening level was found to decrease and approach the value of stress ratio R. The experimental results were compared with those of three analytical models of crack closure and opening, demonstrating the limitations of the currently available elastic-plastic crack growth analysis.
Document ID
19870047387
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Iyyer, N. S. (Virginia Polytechnic Inst. and State Univ. Blacksburg, VA, United States)
Dowling, N. E. (Virginia Polytechnic Institute and State University Blacksburg, United States)