NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Treatment of singularities in cracked bodiesThree-dimensional finite-element analyses of middle-crack tension (M-T) and bend specimens subjected to mode I loadings were performed to study the stress singularity along the crack front. The specimen was modeled using 20-node isoparametric elements. The displacements and stresses from the analysis were used to estimate the power of singularities using a log-log regression analysis along the crack front. The analyses showed that finite-sized cracked bodies have two singular stress fields of the form rho = C sub o (theta, z) r to the -1/2 power + D sub o (theta, phi) R to the lambda rho power. The first term is the cylindrical singularity with the power -1/2 and is dominant over the middle 96 pct (for Poisson's ratio = 0.3) of the crack front and becomes nearly zero at the free surface. The second singularity is a vertex singularity with the vertex point located at the intersection of the crack front and the free surface. The second term is dominant at the free surface and becomes nearly zero away from the boundary layer. The thickness of the boundary layer depends on Poisson's ratio of the material and is independent of the specimen type. The thickness of the boundary layer varied from 0 pct to about 5 pct of the total specimen thickness as Poisson's ratio varied from 0.0 to 0.45. Because there are two singular stress fields near the free surface, the strain energy release rate (G) is an appropriate parameter to measure the severity of the crack.
Document ID
19910029873
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Shivakumar, K. N.
Raju, I. S.
(Analytical Services and Materials, Inc. Hampton, VA, United States)
Date Acquired
August 14, 2013
Publication Date
October 1, 1990
Publication Information
Publication: International Journal of Fracture
Volume: 45
ISSN: 0376-9429
Subject Category
Structural Mechanics
Accession Number
91A14496
Funding Number(s)
CONTRACT_GRANT: NAS1-18256
CONTRACT_GRANT: NAS1-18599
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available