Nondestructive Evaluation of Metal Fatigue.
Abstract
Magnetic perturbation signatures and Barkhausen noise results have been obtained from an AISI 4340 steel fatigue specimen stress-cycled at 180ksi. The magnetic perturbation signals were obtained over a large number an scan tracks for a variety of applied load conditions and for crack lengths from 0.010 inch to 0.050 inch. The signal amplitude varies with load and crack length in agreement with analytical results for magnetic leakage fields, whereas the signal shape appears to be related to the crack depth and localized plastic zones. Analysis of the magentic perturbation data suggests a crack opening model for small surface entering fatigue cracks in which the crack opens in response to applied external forces as though the adjacent crack surfaces are hinged at the bottom. Analytical work is in progress to interpret these results in terms of the magneto-mechanical properties in the vicinity of the fatigue crack. Barkhausen noise signals were obtained on a grid pattern in the vicinity of several fatigue cracks with a Barkhausen detection probe 1/5 the length of the cracks. The results can be interpreted in terms of the stress fields in the vicinity of the cracks. AF 1410 steel fatigue specimens are being fabricated for magnetic perturbation and Barkhausen noise analysis measurements. Fatigue cracks in Ti-6Al-4V specimens were investigated with the electric current injection technique.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1977
- Accession Number
- ADA037672
Entities
People
- F. N. Kusenberger
- G. A. Matzkanin
- Joshua R. Barton
- Philip H. Francis
Organizations
- Southwest Research Institute