FATIGUE CRACK GROWTH CHARACTERISTICS OF NUCLEAR PRESSURE VESSEL GRADE MATERIALS. Paper No. 1. Page: 3 of 11
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The fatigue crack growth data are being generated with 2T WOL (Wedge Opening
Loading) specimens at 550 F in an environment (excluding irradiation) typical
of Pressurized Water Reactors (PWR) and Boiling Water Reactors (BWR). The 2T
WOL specimen is illustrated in Figure 1.
Tests are being performed on A533, Grade B, Class 1 steel (HSST Plate 02) and
weld metal prepared by the submerged-arc, electroslag, and manual-arc processes.
Material from the HAZ (heat-affected-zo.e) of the weldments prepared by the
submerged-arc and manual-arc processes are also being studied.
A test chamber was designed and fabricated to operate at 550*F and 2000 psi.
The test chamber was fabricated from stainless steel. The water w.s pumped
from an auxiliary tank through the test chamber. Typical water chemistry is
given in Table 1. Cycling rates were from 60 to 600 cycles per minute for a
minimum of 100,000 cycles. Initially, the ultrasonic crack growth monitoring
technique was utilized to measure the crack growth in the 2T WOL specimens.
Use of ultrasonics as the chosen crack growth rate monitoring technique required
that the test specimen be clamped to the lid of the test chamber. However, it
was concluded that because of the constrainment of the chamber lid, the "stress
intensity KI " at the crack tip was not well defined. To correct this problem,
the experiment was redesigned to utilize compliance (LVDT gauge) to measure the
crack growth rather than the ultrasonic crack monitoring technique.
Crack length "a" versus number of cycles "N" data were generated for twelve (12)
2T WOL specimens. In order to express the raw test data ("a" versus "N") in
terms of fracture mechanics, the data were converted to the form of crack growth
rate, da/dN versus the cycxic stress intensity range, AK. The crack growth rate
was established by computing the slope between successive data points on the "a"
versus "N" curve obtained by means of compliance (crack opening displacement).
The AK values associated with a particular crack length, and in turn the
corresponding crack growth rate was determined from the following expression:
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Mager, T.R. FATIGUE CRACK GROWTH CHARACTERISTICS OF NUCLEAR PRESSURE VESSEL GRADE MATERIALS. Paper No. 1., report, January 1, 1971; Country unknown/Code not available. (https://digital.library.unt.edu/ark:/67531/metadc1034097/m1/3/: accessed March 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.