Near-tip and remote characterization of plasticity-induced fatigue crack closure
Conference
·
OSTI ID:20005699
An elastic-plastic finite element model and high resolution experimental measurements of growing fatigue cracks are employed in partnership to investigate the relationship between crack closure, near-tip deformation behavior, and remote load-displacement measurements. The model focuses on plasticity-induced closure effects for fatigue cracks in the Paris regime, while the experiments study fatigue cracks in the Paris and near-threshold regimes in a variety of materials. The suitability of the ASTM compliance offset method and the recently-proposed adjusted compliance ratio (ACR) method to characterize near-tip closure effects is evaluated. The experiments and analyses both show that crack-tip strains below the crack-opening stress, S{sub op}, are a relatively small fraction of the total crack-tip strain range for cracks in the Paris regime, and therefore may be insignificant for crack-tip deformation and damage and crack growth. The experiments further indicate that crack-tip strains below S{sub op} are a relatively larger fraction of the total crack-tip strain at lower {Delta}K values, near the threshold, where S{sub op} values are higher. The current ASTM compliance offset procedure for determining the crack opening load is shown to provide accurate information about true crack-tip opening loads in theory. However, due to the limited sensitivity of the method in practice, and the corresponding need to employ a non-zero compliance offset, the method gives underestimates of opening and closing loads that may be considerably in error relative to the true crack-tip values. The current ACR technique does not appear to do a good job of characterizing the near-tip deformation response for cracks in the Paris regime, because remote displacement measurements do not appear to be adequately sensitive to near-tip strains.
- Research Organization:
- Southwest Research Inst., San Antonio, TX (US)
- OSTI ID:
- 20005699
- Country of Publication:
- United States
- Language:
- English
Similar Records
Evaluation of the adjusted compliance ratio technique for measuring crack closure in Ti-6Al-4V
Determining fatigue crack opening loads from near-crack-tip displacement measurements
Separating the influence of K{sub max} from closure-related stress ratio effects using the adjusted compliance ratio technique
Conference
·
Thu Jul 01 00:00:00 EDT 1999
·
OSTI ID:20005698
Determining fatigue crack opening loads from near-crack-tip displacement measurements
Conference
·
Thu Jul 01 00:00:00 EDT 1999
·
OSTI ID:20005702
Separating the influence of K{sub max} from closure-related stress ratio effects using the adjusted compliance ratio technique
Conference
·
Thu Jul 01 00:00:00 EDT 1999
·
OSTI ID:20005696